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Solar Landmarks | Solar design tips, sales advice, and industry insights from the premier solar design software platform

In our Solar Landmarks series, we “travel” to famous landmarks and investigate their potential for solar energy generation.

Two years ago, in honor of Independence Day, we went on a virtual visit to Independence Hall in Philadelphia. This year, we’re visiting Fort McHenry to see what it would take for the fort and its visitor and education center to be powered 100% by solar.

What is Fort McHenry?

Chances are that, even if you’re not a history buff, you’ve probably unknowingly retold the story about Fort McHenry, you might have even sang about it.

Fort McHenry is actually the stage for the United States’ national anthem, The Star Spangled Banner. Francis Scott Key, an American poet, was at Fort McHenry during the War of 1812. Despite being heavily bombed, the Maryland fort was successfully defended to everyone’s surprise. After the smoke cleared at dawn, and seeing that the American flag was still flying, Francis Scott Key wrote a few lines in tribute to what he witnessed.

"O say can you see, by the dawn's early light...that our flag was still there..."

The full poem was originally titled Defence of Fort M'Henry, and was later modified and became commonly known as The Star Spangled Banner. Today, Fort McHenry is a national monument and the flag that inspired the national anthem is permanently displayed at the National Museum of American History.

## Estimating Fort McHenry’s Annual Energy Consumption

The fort doesn’t use a lot of electricity, and the electricity needed to illuminate the flag is actually already sourced by a small set of solar panels that was installed in 2009.

The visitor and education center was completed in 2011, and was awarded LEED Gold Certification by the U.S. Green Building Council because of its sustainable design and efficient usage of energy. Since we don’t have data on the actual energy usage of the 17,500 square-foot building, we will need to estimate the energy use. We can estimate the usage using what’s called energy usage intensity (EUI), which is 15 kBtu/sqft/year.

This converts to about 77.6 MWh annually, which is equivalent to around eight houses in Baltimore.

Assuming the center’s electricity usage for the year is 77.6 MWh, Aurora’s consumption profile tool estimates that the National Park Service pays about $8,400 a year in electricity costs to operate the center. ## Constructing the Site Model Modeling the site can be fairly easy by using Aurora’s SmartRoof and Roof Face tools. We modeled the outerworks with a single SmartRoof object by tracing the outline, and used Roof Faces for the buildings because it can easily detect clerestory windows (i.e., windows in the high-section of the walls). Next, we started adding panels to the outerworks of the fort and found that a 61 kW installation would meet the needs of the center. Anticipating that we probably wouldn’t be able to place panels on a historic building, we checked to see if a 61 kW installation will fit on the visitor center by creating a new design in the project. We easily got to 56 kW by placing panels just on the top roof face alone. We could have fit more panels on the sides, but when we looked at the built-in irradiance map, we found that the lowest roof face is subject to a lot of shadows. Here is what the model looks like with the panels placed: ## Is Solar a Worthwhile Investment? Since the National Park Service has a limited budget, it’s important to show them what the financing aspect of the project would look like. Using Aurora’s financing tool, we can see that an additional PV system provide a monthly average savings of$668 with 95% of their electricity bill offset – well worthwhile.

Next, we calculated the net savings and the payback period of the PV system. Using a commercial system cost of $2.80/W, and assuming the National Park Service can use the current 26% federal incentive tax credit and depreciate the cost of the system, we’re looking at a net savings of$53,000 over the life of the system. With the fairly low cost of electricity, the payback period is 10 years.

Besides saving Fort McHenry money, the PV installation would also offset substantial carbon dioxide emissions. The overall carbon emissions that would be removed are equivalent to burning 60,000 pounds of coal or 6,000 gallons of gasoline each year!

If you're interested in learning more about solar from experts across the industry, join our FREE conference on July 23rd here.

Is there a landmark you’d love to see a solar design for? Let us know in the comments below or email us at hello@aurorasolar.com!

Topics: Solar Landmarks

It’s the holiday season and all we wanted for Christmas was an ITC tax extension. While it wasn’t extended in this year’s congressional session, we’re hopeful that progress will be made to prevent a drop off the cliff from 22% to 0% at the end of 2021.

In the spirit of Christmas, we are taking a look at three places commonly associated with Santa Claus: the Santa Claus House in North Pole, Alaska; Santa’s Workshop in North Pole, New York; and Santa Claus Village in Rovaniemi, Finland. We figured that if Santa is giving away all his coal to naughty children, he’ll need some solar power to keep the workshop up and running!

In our Solar Landmark series, we use Aurora’s solar design and sales software to design solar installations for notable locations around the world, from baseball stadiums to the White House.

Let’s take a look at modeling the buildings and campuses of these Santa-affiliated locations, using Aurora’s SmartRoof design tools, LIDAR and Google Street View, automatic terrain shading, and much more!

### Santa Claus House, North Pole, Alaska

The first location we’re taking a look at is the Santa Claus House in North Pole, Alaska. This outpost has been around since 1952 and offers letters from Santa, delicious snacks, and a chance to meet his reindeer team.

North Pole, Alaska has LIDAR and standard-definition imagery. We found that Bing’s satellite image was slightly sharper than Google’s so we switched to that. Examining the building, there are three main sections to focus on: the two-story entrance by the freeway, the one-story midsection with dormers, and a three-story tower. With Aurora’s SmartRoof design tool, we can model each of these as a separate piece, and have Aurora stitch them together to make the full building.

First up is the two-story section. We use SmartRoof to draw the perimeter, which gives us this a hip roof. When we set the edges to be vertical, the roof changes from a hip structure to a gable structure.

The first step of designing Santa Claus House in North Pole, Alaska is to adjust the default hipped roof (left) to a gable roof (right).

Finally, we raise the height of the remaining two edges and adjust the slope so that it fits with the LIDAR data, and then use the dormer tool to add in the two dormers. After we repeat this for the lower section, we get a mostly completed building.

Santa Claus House in North Pole, Alaska can be modeled in multiple sections in Aurora as shown. LIDAR data allows the designer to match the pitch of the roof and other elements to the real conditions at the site.

The tall tower is a little trickier. We start this as an octagon, and set the “diagonals” to be vertical faces, leaving four of the faces to determine slope. We set one pair to have a higher height, corresponding with the front edge of the building, and another pair to have a lower height. This allows us to create this complex shape, following the same steps as any other SmartRoof building in Aurora.

The tower element of Santa Claus House in North Pole, Alaska can be modeled in Aurora by creating an octagon.

The completed site model of Santa Claus House in North Pole, Alaska as created in Aurora solar design and sales software.

Our irradiance map tells us that the southwest facing section would receive the most sunlight throughout the year, so we’ll start by adding a system there. We filled the roof surface with solar panels, and then used the autostringing tool to automatically connect them, which also takes into account the higher string voltages in the cold weather.

Before we run the performance simulation, we added in monthly snow loss for Big Delta, the closest TMY3 station to North Pole, Alaska. You can get some estimated snow loss data from NREL’s weather stations by checking out our map here.

We entered monthly snow loss values for this location based on the nearest NREL weather station in order to more accurately estimate how much solar energy our proposed PV system would be able to produce.

With the snow losses in place (and assuming Santa doesn’t have his elves clean off the array after each storm), we ran the simulation and estimated an annual production of 19 MWh for the year - a low solar yield compared with sunnier climates like California. Even though the loss factors from snow are quite high in the winter months, snow only accounted for a 7.5% production loss according to the loss diagram, due to the short winter days reducing the light that would have been available in the first place.

We think this might not be enough to power Santa’s toy factory, so we used the carport tool to draw an 80 kW carport over the parking lot (shown below). This brings the production up to 79.1 MWh per year for the site.

The completed solar design, with a carport, for Santa Claus House in North Pole, Alaska, created in Aurora Solar Software.

### Santa’s Workshop, North Pole, New York

Santa’s Workshop in North Pole, New York consists of several small houses that visitors can stop by for last-minute gifts. Each of these can be done with an individual SmartRoof. Since the workshop is on a hill, we chose to increase the heights of all buildings and all trees to match the LIDAR data, ensuring that shadows from neighboring buildings and all trees are correctly assessed. We fit panels onto the two surfaces with the highest irradiance, giving the 39.2 kW system shown below.

A site model and solar design for Santa’s Workshop in North Pole, New York, created in Aurora Solar.

Aurora’s simulation produced a yield of 937 kWh/kWp for a total of 36.8 MWh over the year, making this system a bit better performing than Santa’s Alaskan outpost. Only 4.3% of sunlight was lost to snow by our estimation.

We made sure that automatic horizon shading was calculated for Santa’s Workshop, since the location is surrounded by steep hills. However, we found that this only resulted in a 0.4% irradiance loss over the year, since the panels were placed on faces that look away from the hills.

### Santa Claus Village, Rovaniemi, Finland

Santa Claus Village in Rovaniemi, Finland is located within the Arctic Circle, and offers a chance to meet Santa in person. It’s the largest of the sites we’re investigating. As usual, we used SmartRoof pieces to build pieces of each building, letting the software stitch together the parts to create the finished structure. Here’s our site design and system:

A site model and solar design for Santa Claus Village in Rovaniemi, Finland, created in Aurora Solar.

While Aurora has added LIDAR in many regions around the world, Rovaniemi does not have LIDAR available. Fortunately, users can use our Street View Ruler tool to measure the slope and lengths of buildings. The measurements are saved in the 3D design view and buildings can be adjusted to match those measurements - in this case, the front entrance has a roof pitch of about 25 degrees.

Using Aurora Solar’s Street View Ruler tool, a solar designer can measure the slope of roof faces and the length of different parts of the building or surrounding objects like trees. The left image shows how you can place nodes on the equivalent parts of Street View and top-down images for Aurora to provide the pitch of the roof; results are shown in the right image.

After completing the village design, we can take a look at the sun path to see what areas are shaded throughout the day. Near the summer solstice, the sun doesn’t set, as shown with the sun path tool:

Aurora’s sun path tool shows the path of the sun through the sky at different times of the year. At this location in Rovaniemi, Finland, in the Arctic Circle, we observe an unusual sun path in summer months because the sun never sets.

We fit a 153.4 kW system on the roofs of Santa Claus Village, spread across several buildings, good for an estimated production of 115.2 MWh over the year but with a low yield of 751 kWh/kWp. (Yield measures how much energy, in kWh, is produced for every kilowatt of module capacity under ideal conditions, kWp, over the course of a year.)

Aurora’s loss diagram (which shows how much energy production is reduced by different sources) shows an interesting effect. We have a positive environmental conditions “loss.” This is because the modeled cell temperature was colder than the STC rating conditions of 25C for a good part of the year, which in turn increases the production of the panels compared with the test conditions. Most sites, particularly in hot desert environments, will see a negative value for the environmental loss which also includes mismatch between strings.

Aurora’s loss diagram shows how much energy production is reduced by different sources. Santa Claus Village in Rovaniemi, Finland has an unusual loss diagram that shows positive environmental “losses” because the consistent cold temperatures lead to more efficient panel operation.

Between the three locations modeled, Santa Claus Village presents the most available roof area for solar panels, even though the output per panel will be worse than the North Pole, New York location. We estimate that this system will offset about 2.5 million pounds of coal over its lifetime.

Wherever Santa’s workshop actually is, we suspect that making all those toys requires a lot of energy and think solar could be the perfect gift for the jolly old elf himself. Not only would he and Mrs. Claus enjoy cleaner air, and likely cost savings some great cost savings compared to their current energy source, they’d also be helping to counter the impacts of climate change on their home.

We hope this article provided some insights on how to approach the remote modeling process and helped you see how you can utilize some of the advanced capabilities of Aurora in your solar work. Happy Holidays!

Santa Claus House, Santa Claus Village, and Santa’s Workshop are not affiliated with Aurora Solar Inc. This blog post is for entertainment purposes.

Topics: Solar Landmarks

In honor of baseball opening day this week, we decided to model our local baseball stadium—Oracle Park, home of the three-time World Series championship-winning San Francisco Giants, in the latest installment of Aurora’s Solar Landmark series.

In our Solar Landmark series, we use Aurora’s solar design and sales software to design solar installations for notable landmarks around the world—from Buckingham Palace to Independence Hall.

Located just a few blocks from the Aurora office, Oracle Park (recently known as AT&T Park until this year) was straightforward to model using Aurora’s new Draw Roof Face tool. The stadium was opened in 2000, replacing the team’s former, notoriously windy, home at Candlestick Park. With beautiful views of the San Francisco Bay, the Giants’ ballpark is a leading tourist attraction in the city.

Although the SF Giants don’t have their home opener for another week, we’re excited to welcome the return of baseball season. Read on to learn how we created a 3D model of Oracle Park in Aurora and created a solar design to match its existing solar arrays.

## Creating a 3D Model of the Giants’ Ballpark in Aurora

When beginning to create our 3D model of the park—which would allow us to determine where solar panels would fit, as well as what areas get the most sunlight—first up were the stadium stands.

We used Aurora’s Draw Roof Face tool, which allows you to draw individual surfaces, providing a simple option to quickly estimate the solar production of a roof face and produce a quick first pass quote to the customer.

A top-down view of Oracle Park, home of the San Francisco Giants, as designed in Aurora solar software.

Modeling these sections was a breeze with the Draw Roof Face tool since it automatically snaps to the LIDAR data for the site. Each of the single “roof” pieces can be manually adjusted if necessary as well. On the curved sections, we created multiple segments to match the curve of the field. You can see the process of creating a section of the stadium stands in the GIF below.

The process of using Aurora Solar's Draw Roof Face tool to model sections of the stadium stands at Oracle Park, home of the SF Giants.

We also modeled a few prominent features of the park, including the giant Coca-Cola bottle past the left-field bleachers, the field lighting (which was upgraded with LEDs recently, cutting energy consumption by 60%), and the palm trees scattered around the walkways. We also recreated the pitching mound using Aurora’s Draw Tree tool. By creating a sunken tree (setting the tree trunk to a negative height) we were able to create the mound.

The distinctive Coca-Cola bottle at Oracle Park, recreated using Aurora solar software.

## Designing the Oracle Park Solar Array

The next step in our process was to add the solar panels. (Normally one would assess the irradiance of the site before deciding where to put panels, but since the stadium has had a PV system installed since 2007, we opted to begin by recreating it.)

Oracle Park’s PV system includes awnings along the waterfront walkway and a larger array above the staircases. High-definition Nearmap imagery captured last year (available through Aurora’s Nearmap integration) clearly shows where they have been installed.

An aerial view of the solar installation at Oracle Park.

Modeling the arrays in Aurora was simple. The large array above the stairwell can be modeled using the carport tool, the tilted system on the roof can be modeled using the module placement tool. To model the solar awnings, we used a pre-configured carport array.

Here’s how easy it is to replicate awnings or carports with Aurora:

Aurora allows users to create carport/ground mount templates, which will use specified arrangements of modules. This tool made it easy to design the solar awnings at Oracle Park.

With all of the buildings and features in place, we ran the irradiance map to see how much solar potential the site has (and how much sun your seats will get over the year). We noticed that the large rooftop arrays receive a lot of sunlight over the year, but some of the awnings lose out on afternoon sun due to shade from the upper deck of the stadium.

An irradiance map or Oracle Park, home of the SF Giants baseball team. Aurora Solar software generates the irradiance map using local weather data and simulations of the sun’s path at every daylight hour of the year.

Calculating the irradiance at every point of a complicated structure like this stadium requires complex computation. Aurora Solar generates this data in about 20 seconds.

This irradiance information gives some interesting insights for finding your preferred seating options. Seats along the 3rd base line and left field receive the most sunlight over the year, while the 1st base side is much more shaded.

Thanks to the Sun Path tool, we can see that in August the first seats to get shade (at 4 pm) are behind home plate and the back-most seats in all three levels of the right-field side of the stadium. Meanwhile the left-field seats are sun-exposed until about 5 pm and the bleachers don’t get shadows until 6 pm. Of course, you can also use this feature to determine where to place panels in your new installation!

Aurora’s Sun Path tool shows the movement of the sun through the sky at any time throughout the year—and the resulting shadows at your solar project site.

Having determined the irradiance at different parts of the stadium, we were able to use Aurora’s Performance Simulation tool to estimate how much energy it produces in a typical year. Aurora reveals that the system produces about 191,694 kWh per year (191.694 MWh).

Based on that, in the 12 years since the installation, we estimate that the PV system has produced enough energy to offset about 1,000,000 lbs of CO2, based on CA emissions of around 452.5 lbs CO2 per MWh.

And there you have it—the process of designing a solar installation for Oracle Park!

Do you have other favorite landmarks you’d like to see solar designs for? Let us know in the comments below!

Topics: Solar Landmarks

The Aurora Solar team had a great time at Solar Power International (SPI) last week. SPI is the largest solar event in North America. With attendees from over 3000 companies and hundreds of exhibitors showcasing the latest in solar technologies, Anaheim Convention Center was abuzz with activity for SPI 2018!

With all the energy it takes to power such a huge event (at the largest convention center on the West Coast), we were happy to know that some of that energy was coming from clean solar power–quite appropriate!

To keep the fun of the conference going, we took a few minutes to model Anaheim Convention Center’s solar installation in Aurora. In this installment of our Solar Landmark series–where we model solar PV systems for landmarks around the world–we used Aurora’s new and improved design capabilities to quickly generate this large design. It took Aurora’s Research Engineer, Andrew Gong, only about 10 minutes to complete! Here’s how he did it.

The 2.4 megawatt array on the rooftop of the convention center was installed in 2014. According to the contractor that installed it, the system utilizes 7,908 Yingli Solar panels, Sunlink Core RMS racking, and Advanced Energy 500NX inverters. It is owned by the Anaheim Public Utilities (APU) and the City of Anaheim and helps APU meet its mandate to source 33% of its energy from renewable sources by 2020.

An aerial view of the solar array on Anaheim Convention Center, the site of SPI 2018. Source: Google Maps.

## Modeling the Project Site

### Constructing the Buildings

To create an accurate design, we began by constructing a precise 3D model of the convention center. To do this in Aurora, we started by outlining the edges of the buildings in satellite imagery using Aurora’s SmartRoof Tool.

A top-down view of our site model of Anaheim Convention Center. You can see the outlines of the buildings in white. Based on these outlines, Aurora generated a 3D version of the site.

Based on the building outlines, Aurora’s SmartRoof Technology generated 3D versions of the buildings. One advantage of the SmartRoof tool is the ability to construct the building from several simpler parts, which SmartRoof then merges together.

Additionally, because the building has three similar sections (the sections where the solar arrays are located in the image above), we were able to save time by modeling one and then copying it to create the other two sections. This allowed ups to create those sections of the building with just had to make a couple of slight manual modifications.

To save time creating the site model for the convention center, we duplicated similar sections of the site and adjusted them as needed. In this demonstration, you can also see how Aurora's SmartRoof tool allows designers to construct a larger building out of simpler parts which it then merges together.

Aurora reDesigned, our latest software update, made it easy for us to view the building from different angles:

Aurora reDesigned allows seamless transitions from 2D to 3D views of a project.

Once the structure of the buildings was complete, we had to make sure that the model included any obstructions on the roof–such as skylights and HVAC units–that would prevent the placement of panels.

To save time, we took advantage of Aurora’s automatic obstruction detection tool. Powered by computer vision, this tool allows the designer to model one obstruction which Aurora uses to find all other obstructions like it on the roof.

### Ensuring Accuracy with LIDAR

Once we had a complete model of the site, we used LIDAR to ensure the accuracy of the site. If you’re not familiar, LIDAR data creates a detailed 3D map of the heights of structures in an area, like buildings and trees. The LIDAR data used for these purposes is typically gathered by planes that ping an area with lasers and measure how long they each beam takes to return to a sensor (similar to SONAR but using lasers instead of sound pulses).

LIDAR shows the topography of this area, allowing us to confirm the accuracy of our model of Anaheim Convention Center, where SPI 2018 took place.

We used Aurora’s “Fit Buildings to LIDAR option” to ensure that our model matched the actual building details. With that, we had a complete and accurate 3D model of Anaheim Convention Center–an excellent starting point for designing a solar installation suited to the site.

## Designing the Installation

Before placing panels, we used Aurora’s walkway tool to add appropriate walkways to ensure compliance with local codes. Once walkways have been placed, Aurora will avoid placing panels in those areas, even when automatically filling the roof face.

Placing walkways in Aurora.

We then used Aurora’s panel placement tool to quickly place solar panels in the available space. This tool allowed us to click and drag to automatically place panels while avoiding obstructions. The results, modeled on the existing array, are shown below.

The final design of Anaheim Convention Center's solar system.

And there you have it! A recreation of the solar array on Anaheim Convention Center, modeled in about 10 minutes. This impressive system produces approximately 302,192 kWh each month and 3,626,310 kWh per year. It offsets 17% of the convention center’s energy needs–making this a great site for an event like SPI!

As more commercial customers consider solar to help them cut costs and show commitment to sustainability (a recurring topic of SPI panels this year), design tools that support fast but accurate designs can help solar contractors better serve this growing segment.

Notes: Since this was just a quick educational exercise, we didn’t delve into some later steps of the design process, like stringing, modeling energy production, and financial analysis.

Acknowledgments: Special thanks to Research Engineer Andrew Gong for designing this system in Aurora.

Topics: Solar Landmarks

If you’re a regular reader of the Aurora Blog, you know we love to flex our solar design skills through periodic “Solar Landmarks”—where we design solar installations for notable landmarks around the world. Today on Independence Day, we could think of no better landmark to model than Independence Hall, the birthplace of American democracy.

Both the Declaration of Independence and the U.S. Constitution were crafted and signed in these hallowed halls, now a UNESCO World Heritage Site. Andrew Hamilton oversaw construction of the building, which began in 1732, and George Washington was appointed Commander in Chief of the Continental Army here in 1755.

Independence Hall in Philadelphia, Pennsylvania. To the right of Independence Hall is Congress Hall, which housed the US Congress from 1790 to 1800, and to the left is Old City Hall, which housed the United States Supreme Court in the 1790s. Credit: NPS photo.

While we suspect that the National Parks Service might have some reservations about adding solar panels to such a historic roof, in today’s article we engaged in a fun thought experiment to see how solar could deliver energy savings and environmental value to this national treasure.

## Evaluating the Project Site

The building is comprised of three main partsa central hall, which sports a tall tower and steeple (these were added in 1750, and were not part of the original building), and two wings on the east and west sides. The wings are connected to the main portion of the building by covered walkways.

The east and west wings have hipped roofs, while the roof of the central section has folds and is relatively flat in the center. This center section section of the roof has a few obstructions we need to be mindful of when considering a rooftop solar installation: low fences section off this part of the roof, which is also bounded on either end by decorative brick walls.

In this view of Independence Hall, the obstructions on the roof of the central building (decorative fences and brick walls) are clearly visible. Credit: NPS photo.

Immediately to the right and left of Independence Hall are two other notable buildings from the colonial era, Congress Hall, which housed the U.S. Congress from 1790 to 1800, and Old City Hall which housed the United States Supreme Court in the 1790s. These two structures are also part of Independence National Historical Park operated by the National Parks Service, through an agreement with the City.

### Consumption Data

In order to determine how large of a solar installation was appropriate for this site, and how much solar could reduce the building’s utility bills, we first needed to determine how much energy the building uses.

While we lacked the utility bill data we might have if this were a real solar client, thankfully, Philadelphia publishes energy consumption data for city-owned buildings—including Independence Hall!

We found that in 2016 Independence Hall used 839,230.2 kBTUs of electricity. Knowing that 1 BTU, or British Thermal Unit = 0.00029307107017 kWh and there are 1000 BTUs in one kBTU, we were able to determine that the building’s annual consumption is 245,954.1 kWh.

We didn’t have a monthly breakdown of how that consumption was distributed throughout the year. However, because Aurora’s consumption portal can extrapolate energy use throughout the year based on even a single monthly data point, we worked backward entering a couple of monthly consumption values until we arrived at the appropriate annual consumption.

Estimated electricity consumption of Independence Hall by month based on it’s known annual electricity usage. Aurora’s consumption portal is able to extrapolate usage for other months given one or more monthly usage (or bill) values.

[For more information on how Aurora intelligently extrapolates energy consumption based on patterns for different areas and building types, check out our related residential and commercial load profile articles.]

### Constructing a Site Model

To ensure precision in determining how many solar panels this roof could fit, and how energy production would be impacted by shading from trees and other obstructions at the site, we started by creating a detailed 3D model. For good measure, we also modeled Congress Hall and Old City Hall in case they shaded the structure. Aurora’s SmartRoof design functionality made this easier since we could just outline the edges of the roof and Aurora would automatically infer the roof structure.

A 2D view of our site model of Independence Hall, designed in Aurora.

With a few manual adjustments and the addition of roof obstructions, we had a detailed 3D model from which to create an accurate solar design. Obstructions included two tall chimneys on the east and west wings of Independence Hall, the previously mentioned fences on the roof of the main building, and spires on the roofs of Congress Hall and Old City Hall. The area is also filled with many trees and a neighboring skyscraper that could cast shade on the roof, so we carefully modeled these structures as well.

A 3D view of our site model of Independence Hall, designed in Aurora.

At first glance, it seems that there is plenty of roof space to support a moderately large commercial solar installation. However, we also needed to evaluate the solar potential of this roof because we would not want to place panels in heavily shaded areas.

### Assessing Solar Potential

Using Aurora’s remote shading engine we generated an irradiance map of the roof of Independence Hall. Brighter areas represent areas of higher irradiance. Unfortunately, the solar potential of Independence Hall, located in an area with many trees, leaves a lot to be desired. The south-facing roofs, though having higher solar access as expected, have either obstructions (chimneys on the east and west wings) or, in the case of the main building, receive shade from the steeple.

An irradiance map of Independence Hall, showing how much solar energy is available at different points on the roof.

The roofs of Congress Hall and Old City Hall were more promising, with over 90% solar access on some portions of the south-facing roofs (see dialog box above). We initially entertained the idea of placing some panels in these areas, although the roof faces are small and feature dormers.

Using Aurora’s “fill roof face” tool, which allowed us to specify a minimum Solar Access Percentage (SAP) for placement of panels, we explored whether a rooftop system could be a viable option. However, requiring that panels be placed only in areas with a SAP of at least 80% resulted in a smattering of panels that was not aesthetically pleasing:

In our first design we attempted to place panels in areas of the roof with a Solar Access Percentage greater than 80%. However, the limited roof area meeting that criteria made this design strategy undesirable.

With a rooftop solar system effectively ruled out, we turned out sights to a possible ground mount for Independence Hall. We think that option would also be more appealing to the National Parks Service, tasked with maintaining the site’s historical integrity! Plus, on hot summer days, these elevated ground mounts could provide much-appreciated shade for visitors.

Across Chestnut Street is a sidewalk area and a large grassy expanse, both also part of Independence National Historic Park. With little tree cover in this area to obstruct solar access, we thought this was a great place for a solar ground mount.

2D view of our proposed ground mount solar installation for Independence Hall.

3D view of our proposed ground mount solar installation for Independence Hall.

We designed a system comprised of 5 arrays of 64 panels (8 rows of 8) with a tilt of 15 degrees.1 The result is a 109 kW system. We then used Aurora’s performance simulation engine to calculate how much energy this system would produce for Independence Hall. Aurora calculates that the system would produce 127,406 kWh per year, offsetting 52% of the building’s annual energy use. Not too shabby!

Estimated energy production of the ground mount solar installation we designed for Independence Hall.

Aurora’s system loss diagrams show how different factors reduce the energy production of your solar design. This can be helpful in allowing you to improve the performance of your design.

Independence Hall was the site of many of the great advances in modern democracy. With a solar installation like this, it could also help lead the way toward energy independence and a future of clean energy!

Our final solar design for Independence Hall!

P.S. Have another famous landmark you’d like to see solar on? Let us know in the comments below and we’ll see what we can do!

#### Notes:

1. We initially designed the system with a tilt of 9 degrees but using Aurora’s system loss diagram we determined that we were losing a lot of production due to the Tilt and Orientation Factor so we adjusted the solar design accordingly. This ability to see how different design factors impact performance and quickly make adjustments was very helpful, allowing us to generate an additional 22,147 kWh annually!

##### Acknowledgments:

Special thanks to Aurora Research Engineer Andrew Gong for creating the site model of this complex building!

Topics: Solar Landmarks

In our Solar Landmarks series, we explore solar designs for landmarks around the world—such as Buckingham Palace, the White House, and the home of Canada’s Governor General—all from the comfort of the Aurora office.

For the past four years, that office has been in Palo Alto, but starting this week we are excited to have new offices in San Francisco that will give us room to grow as we work to bring you the most robust solar design and sales software in the industry.

With that in mind, for this Landmark article, we decided to set our sights a little closer to our (new) home and use Aurora to model a solar design for San Francisco’s iconic City Hall.

San Francisco City Hall.

This complex building gave us the chance to flex our 3D modeling skills using Aurora’s SmartRoof tool—and an opportunity to get familiar with some of the city’s efforts to advance clean energy and sustainability.

Featuring an impressive dome, a grand staircase in the central hall, gilt exterior detailing, and white marble interiors, this beautiful building was part of an effort to showcase the rebirth of San Francisco after the Great Earthquake and Fire of 1906. It’s completion timed for the the start of the World's Fair of 1915.

Today, City Hall showcases San Francisco achievement in a different way—with a 80 kW solar array that demonstrates local commitment to renewable energy and reducing greenhouse gas emissions.

Views of the solar array on San Francisco City Hall. Photo credits: SFPUC, Robin Scheswohl (left), SFPUC (right). Source: 2015 Energy Benchmarking Report, San Francisco Municipal Buildings.

Leadership by City Hall makes sense. San Francisco has set ambitious clean energy targets, with a goal of sourcing 50% of its electricity from renewable sources by 2020 (ten years earlier than the deadline for California’s equivalent target). Although power for municipal buildings comes from carbon-free hydropower, City Hall’s solar array contributes additional clean energy to the city’s energy mix.

## Determining City Hall’s Energy Consumption

We began our design process by seeking to understand how much electricity City Hall uses. Sometimes, it takes a little detective work to find energy consumption data for our Solar Landmark articles since, unlike a typical solar customer, we don’t have their electricity bill data to plug into Aurora’s consumption portal.

This time, our work was simplified, however, because San Francisco requires owners of non-residential buildings over 10,000 square feet to publish energy consumption data each year. The city publishes this data for municipal buildings in its annual Energy Benchmarking Report.

Because City Hall’s solar array was installed in January 2015, we looked at the 2014 report for the building’s pre-solar energy consumption. The city reports this energy consumption data in the form of Energy Use Intensity (EUI) values in the units of kBtu/sq. ft. This normalized data makes it easier to compare the energy efficiency of buildings of different sizes, and provides a standardized benchmark to assess improvements over time.

City Hall’s EUI in 2014 was 39.4 kBtu/sq. ft. and the square footage of the building is 516,484. This allowed us to determine that an electricity usage of 5.96 GWh per year (for our math, see notes at the end of the article ). While this is quite a lot of energy, the EUI values are in the normal range for commercial buildings. The city is working on increasing building energy efficiency to reduce the energy consumption of municipal buildings like this one (one goal of the annual benchmarking reports). All the more reason solar on City Hall is an exciting addition!

## Modeling the Building

An accurate site model is the basis for designing an optimal solar array and modeling its energy production. To model this intricate building, we turned to one of Aurora’s resident solar design experts—Research Engineer Andrew Gong.

A top-down 2D view of our Aurora model of San Francisco City Hall.

Andrew used Aurora’s SmartRoof tool to create the building from a number of simpler parts as detailed below. SmartRoof seamlessly merges together component sections when they are dragged together, making it possible to create a precise design of even the most complicated buildings. (For more detail on the specific steps Andrew took, see the diagram below.)

An overview of the process of designing San Francisco City Hall in Aurora, by creating simpler component sections and merging them together with SmartRoof.

From there, Andrew used Aurora’s Add Obstruction tool to account for the variety of vents, skylights, and other structural elements that pepper the roof, which would prevent placement of solar panels. While not tall enough to shade the roof, the rows of trees on three sides of the building were added for good measure.

The result is an impressive 3D site model:

A 3D model of San Francisco City Hall created in Aurora.

## Assessing the Roof

As you can see in the site model, the large rotunda in the center of the roof makes placing solar panels in that area impractical, as do recessed areas to the left and right of the dome. However, two large flat areas of roof space on either side of the dome provide ample room for a solar array.

As shown in the irradiance map produced by Aurora’s shading engine (below), while there is some shading from the rotunda, overall the roof has relatively high irradiance making it a good candidate for solar. As expected, the southern roof face—which was selected for the site’s current solar array—has slightly higher irradiance with solar access values of approximately 95% across much of the surface.

Aurora’s shading engine determines irradiance levels with accuracy that is statistically equivalent to on-site shade measurements, according to analysis by NREL.

In most of our Solar Landmarks, we create theoretical solar designs for sites that lack them—but since City Hall already beat us to the punch, we decided to model the existing array as precisely as possible and then explore how much energy it produces.

While we had limited data on the specifications of the installed design like the exact modules used, we were able to use a few pieces of information in combination with satellite imagery to create a design that closely matches the real system.

The San Francisco Public Utilities Commission reports that it is an 80 kW system comprised of 230 panels. This allowed us to determine the approximate wattage of the panels (80,000 watts/230 panels= 347.8 watt panels). We also knew that the system used high-efficiency modules.

Based on this, we input high-efficiency 345 W custom modules which are in the appropriate wattage range. We overlaid them on the roof over recent aerial imagery showing the installed panels and found them to be a match in size.

A comparison of our solar design and aerial imagery the installed design on City Hall.

From there, we used trial and error to find the correct spacing between each module and row of modules. We determined spacing of 1 inch between panels and 16 inches between each row matched the current design. We also estimated a tilt of 10 degrees based on close-up photos of the array.

Finally, we placed 230 panels in the same configuration as the real design, using aerial imagery of the system as our guide. There you have it—San Francisco City Hall’s solar array:

A 3D model of San Francisco City Hall with its solar array precisely recreated in Aurora.

## Analyzing System Performance

With the design carefully recreated, we used Aurora’s Performance Simulation feature to model the expected energy production of the system, taking into account shade at each hour of the day as well as local weather data and the system configuration. Aurora predicts an annual energy production of 116,622 kWh.

Aurora's simulation of monthly energy production of City Hall's solar array based on the system configuration, shading, and local weather data.

Aurora also calculates energy production losses from a variety of different sources, which it presents in a system loss diagram like the one above for City Hall.

While this is only a tiny percentage of the building’s large annual energy consumption (about 0.2%), the array offsets the carbon equivalent of 13 homes' electricity use for one year or the consumption of 201 barrels of oil. The carbon savings are also comparable to the carbon sequestered by 102 acres of U.S. forests in one year.

Of course, in this case, since City Hall is powered by clean hydropower, the system isn’t directly offsetting emissions, but by making hydropower that would have been consumed available to other buildings in San Francisco it is still offsetting other, less sustainable energy consumption further down the line.

We’re excited to be starting a new chapter of our company in San Francisco and hope you’ve enjoyed this design in honor of our new city!

P.S. Is there a landmark you’d love to see a solar design for? Let us know in the comments below!

Acknowledgements: Special thanks to Andrew Gong for making this article possible by creating the model of City Hall and for providing significant guidance on the system design and other details of the article.

Notes on our methodology for calculating City Hall’s energy consumption:

• kBTU equals 1,000 BTU
• Conversion rate: To convert BTU to kWh multiply by 0.000293
• 39.4 kBtu/sf/yr *1000= 39400 BTU/sf/yr * 516,484 sf= 20,349,469,600 BTU/yr * 0.000293 kWh/BTU = 5,962,395 kWh per year = 5,962.39 MWh per year = 5.96 GWh per year

Topics: Solar Landmarks

When the International Brotherhood of Electrical Workers in San Jose, California (Local Union 332) decided to replace an aging commercial solar array on their union hall, they set their sights on a solar project that would offer benefits far beyond bill savings and reduced environmental impact. Using Aurora, they designed a unique 200 kW commercial solar installation (which spells out the organization’s name in solar panels!) that will offer business benefits for years to come.

In our previous article, we shared the story of the project’s development and the benefits it provides. In today’s article, we explore the how the system was designed in Aurora and how the use of a robust solar design software streamlined and enhanced project development.

The union hall of IBEW Local 332 now hosts a 200 kW commercial solar array designed in Aurora.

# Project Impacts and the Role of Aurora

As the most extensive electrical union in the world, the International Brotherhood of Electrical Workers (IBEW) advocates for the interests of its member electricians. It also keeps an eye on emerging business opportunities for electrical workers. These days, many of those opportunities are in solar and other renewable energy technologies. So, as they considered replacing the solar installation on their union hall, IBEW Local 332 saw an opportunity for their union members to hone their solar design and installation skills.

Working with the National Electrical Contractors Association (NECA), the trade association representing U.S. businesses in electrical construction industry, Local 332 installed the solar array as part of a broader retrofit to make their union hall a net zero energy building. In addition to giving NECA and IBEW members experience leading a project of this scale from start to finish, the project is a high-profile example of their workmanship for prospective clients. It even provides its own advertising! The array spells out IBEW in solar panels making it identifiable to air travelers flying into San Jose International Airport.

Aurora software, which was used to design the project, played an important role in enabling these benefits. Christopher Smith, Business Developer and Alternative Energy Engineer with NECA and the IBEW, took the lead on the project designs. He credits Aurora solar design and sales software as a key tool that enabled the stakeholders to easily evaluate different design options and settle on an optimal design to meet their needs.

“Aurora was very helpful because we could actually see what a given design would look like. Not only that, we could know what the production value was, what the costs were going to be, and everything in between, even down to the aesthetic level.”

In addition to accurate 3D models that made it easy to visualize exactly how the project would look, Aurora also streamlined the design process. Smith could quickly make design adjustments and share them with project stakeholders. Accurate performance simulation made it easy to compare the energy production of different design configurations.

Chris Smith, project designer (right), discusses the project with Ken Spears (left), whose firm Pacific Ridge Electric installed the system.

# Taking the Project from Concept to Reality

## Modeling the Project Site and Assessing Solar Potential

The first step, before developing and assessing potential designs, was to create a 3D model of the project site. This allowed for the evaluation of potential PV panel locations, as well as assessment of how much solar energy the roof receives (a required input for calculating how much energy the system will produce).

Local 332’s union hall was a cinch to model in Aurora. The one-story building has a flat roof and just a few obstructions, meaning tools like Aurora’s Automatic Obstruction Detection weren’t needed. To model the project, the perimeter of the roof was traced over the aerial imagery of the site. To accommodate the rounded corners of the building, multiple nodes were placed to create a curve.

A 2D aerial view of the building, used to generate the preliminary 3D model in Aurora. As you can see, the first step was to outline the building, allowing the SmartRoof feature to automatically generate the roof structure. Obstructions, such as skylights and the HVAC units were then added.

From there, the model was adjusted to include obstructions that prevented panel placement and could cause shading. Among the obstructions to be modeled were a walled-off area containing HVAC units, several rectangular skylights, and a number of roof vents.

These were easily modeled by drawing polygons with Aurora’s “Add Obstruction Tool,” and then setting the height of each. Another feature of the building that had to be modeled was a shade awning running along one side of the building. Taking into account these factors allowed Aurora to generate an accurate 3D model of the site.

An accurate 3D model of the project site, including obstructions like skylights and vents, created in Aurora using satellite imagery. (The imagery shows the 30 kW solar array previously installed on the building, which was disassembled before installation of the new system started.)

With an accurate site model created, assessing the available solar energy on the site was simple with Aurora’s irradiance engine. As you can see below, the site is excellent for a solar PV system; it is almost completely shade-free and just about every point on the roof has a solar access value of 99%.

Aurora’s irradiance engine, which assesses the available solar energy on each point of the roof for every day and hour of the year, shows that this commercial site is exceptionally well suited for solar.

## Evaluating Potential Designs and Their Energy Production

With the irradiance levels of each point on the roof determined, Smith could explore a wide variety of different design configurations. “By the time we settled on the final design, we were probably on our tenth iteration,” says Smith. “Previously that would have been time consuming, but with Aurora it was simple. I'd sit down to the computer, spend a couple minutes modifying the design, and then I'd take screenshots or send them the file.”

Numerous alternative layouts for the solar array, like these, were considered during the design process. (Note that these are draft designs and are not finalized.)

Aurora’s performance simulation capabilities made it easy to predict how much energy different designs would produce. A key factor that influenced Local 332’s decision to spell out IBEW in solar panels was that they had more space than they needed to meet the building’s full energy production needs.

According to local interconnection policies, grid-tied solar installations must be designed so as not to exceed 110% of the site’s historic electricity consumption. Given size of the roof and its excellent solar generation potential, Smith found that if they had designed the array to fill the entire roof face it would have exceeded this limit. Additionally, under California’s net metering policies excess solar production beyond the building’s annual needs is compensated at a much lower rate.

With space to spare, designing the solar array to spell out IBEW was an appealing opportunity to let the site be its own advertisement. With San Jose International Airport nearby, there is significant air traffic to see the solar installation from above. As the team began to more seriously consider spelling the IBEW acronym in a portion of the array, they wanted to test out how the design would actually look from an airplane before making a final decision.

They arranged panels from the old array, which had been disassembled, to spell out IBEW as designed in Aurora. Local 332 General Manager Gerald Pfeiffer then took photos of the placeholder array as he flew into San Jose International Airport after a trip. The team was thrilled to find that design was easily identifiable from the air, just as it appeared in Aurora. With the feasibility of the plan assured, they proceeded with the unique design.

The final system design is comprised of 595 panels and has a capacity of 202.3 kW.

Aurora’s highly accurate performance simulation feature enabled the team to predict with confidence the energy production of different design variations. The estimated monthly production of the installed system is shown above.

The selected design will produce 302,421 kWh each year, offsetting the building’s total annual energy consumption while not exceeding the maximum energy offset allowed under local interconnection policies.

The final completed installation. Credit: NECA-IBEW Powering America.

The project was completed this month and is already generating attention and business opportunities for IBEW and NECA members. Pacific Ridge Electric, the contracting firm that installed the system, has received numerous inquiries from prospective customers interested in solar projects or net zero building retrofits like this one. (To learn more about the project’s goals and impacts, read our earlier post detailing the project’s development.)

Aurora played a central role in the project’s success by streamlining the design process, accurately estimating energy production, and providing precise 3D models that made it easy to visualize exactly how the project would look. This made it much easier for the IBEW/NECA team to manage the project entirely in-house and reap the full benefits of their clean energy investment.

Topics: Solar Landmarks

Over the last year, the local electrical union serving California’s Santa Clara County has undertaken the development of an impressive 200 kW commercial solar array and net zero building retrofit on their union hall in San Jose. The project, completed this month by Local Union 332 of the International Brotherhood of Electrical Workers (IBEW) and the National Electrical Contractors Association (NECA), will enable the union hall to generate all of its energy with solar. It is also making a splash for the two organizations by providing a stunning example of the solar installation skills of both IBEW and NECA members. If you ever fly into San Jose International Airport, chances are this project will catch your eye from the window of the plane… because part of the array spells out IBEW!

A new commercial solar array on the International Brotherhood of Electrical Workers’ Local 332 Union Hall is easily identifiable to passengers flying into San Jose airport. Left: aerial photograph photograph of the completed project (Credit: NECA-IBEW Powering America), Right: project design in Aurora software.

As part of a broader project to make the entire site a net zero energy building, the solar array will produce more than 100% of the building’s energy consumption. The project, created using Aurora solar design software, will save the local union over $140,000 per year in utility bills and cut carbon emissions. But its value goes far beyond energy savings for the union hall; it is also an important business development initiative. With renewable energy technologies like solar PV and energy storage becoming highly-sought skills for electrical workers, managing the solar project from design to installation allowed IBEW and NECA to showcase their talents to prospective clients in a high-profile way. Aurora played an important role in facilitating the project; it streamlined the process of creating a variety of potential designs and made it easy to assess the energy production and bill savings benefits of each. In today’s article, we delve into the story of the project and its benefits for IBEW Local 332 and NECA members. In our subsequent article, we explore the design process through the lens of Aurora. ## Envisioning the Project: Growing Skills and Business Opportunities Innovation isn’t new to Local 332; it’s one of the largest IBEW Local Unions in Northern California, known for its leadership in implementing cutting-edge technologies. Its union hall previously hosted the . It was also the largest commercial solar array west of the Mississippi when it was installed in 2001. This was during the height of the electricity crisis in California when the state experienced several large-scale blackouts. Because the building also had a back-up battery system that enabled it to keep running during the blackouts, it gained notoriety in the local community. The union hall of IBEW Local Union 332. The solar array show here is the building’s previous installation, which was the first commercial solar array in San Jose, installed in 2001. Source: Google Maps. In the nearly two decades since the historic installation, the early modules had degraded and the union was interested in replacing them. While they could have simply replaced the 30kW system, they had a vision to make the project much grander. Local 332 Business Manager Gerald Pfeiffer saw this as an opportunity for the union to demonstrate its expertise in renewable energy technologies through a larger and more complex project. But that wasn’t the only incentive to embark on this new project. California law has established aggressive targets for all new (and many existing) buildings to meet . Under these requirements, buildings’ annual energy consumption must be less than or equal to the energy generated by onsite renewable energy systems. By 2020, all new residential buildings will be required to meet zero net energy requirements; by 2030, this will apply to all new commercial buildings and 50% of existing ones. Because of this, there will be a rapidly growing market for contractors with the skills to implement net zero energy projects. By expanding the scale of the solar installation and undertaking retrofits to meet the building’s full energy needs, Pfeiffer saw an opportunity for union members to gain skills in this burgeoning field. The project was implemented by Pacific Ridge Electric, a member company of NECA, co-founded by IBEW electrician Ken Spears, pictured above. Credit: NECA-IBEW Powering America, Electric TV- San Jose Net Zero video. While local IBEW and NECA members had prior experience with commercial solar installations, this project had special significance because it was undertaken in-house with one electrical contracting company, Pacific Ridge Electric, overseeing the solar project from start to finish. In many commercial solar projects and net energy retrofits of this scale, there are a large number of contractors managing different aspects of the work. This makes it more challenging for electrical contractors who want to transition into a leading role to gain familiarity with the full range of project requirements. By executing this project from start to finish, Pacific Ridge Electric provides a tangible and impressive example of NECA and IBEW members’ experience with solar installations of this scale. Aurora’s software played an important role in facilitating the project, as did technical and financing assistance from NECA’s Energy Conservation and Performance (ECAP) Platform. Aurora was used to design the installation, and to forecaste the energy production of different design configurations. ECAP, working alongside Pacific Ridge Electric, provided services such as energy auditing, economic modeling, and project management support, and connected the project with$3.2 million in financing—covering the full upfront cost of the building retrofit. The ECAP program’s financial and technical services are designed to make it easy for any member electrical contractor to implement a renewable energy project.

IBEW and NECA - Representing the Workers and Firms of the Electrical Industry

NECA and IBEW are two major organizations in the electrical contracting industry that today work closely together. IBEW is a union representing individual electrical workers, while NECA is a trade organization that supports member electrical contracting firms and advocates for the industry. The two organizations operate symbiotically providing education and training, business development, and other services to advance the industry.

 The International Brotherhood of Electrical Workers (IBEW)  is the most extensive electrical union in the world, representing approximately 750,000 active members and retirees.The organization was founded in 1891, in the early days of the electrical industry, to improve conditions for electrical workers including advocating for fair pay and improved training and safety for workers. Today, IBEW represents electrical worker members in a wide variety of fields, including utilities, construction, telecommunications, manufacturing, and government and still advocates for members' wages, benefits, and rights. The National Electrical Contractors Association (NECA)  is a trade association that represents businesses in the 130 billion U.S. electrical construction industry.While most NECA members are small businesses, large, multi-area electrical contracting firms are also members of the association.One of NECA’s current initiatives is its Conservation and Performance (ECAP) Platform, which helps members get involved in energy efficiency and distributed generation projects. In Santa Clara County, California, cooperation between IBEW Local Union 332 and NECA includes the operation of a where accepted applicants are provided with cutting-edge training for careers in electrical work, including training in solar PV design and installation. The apprenticeship program is notable, because it is a tuition-free degree program. Apprentices accepted to the program join the IBEW 332 union and are dispatched by IBEW to electrical contractors. They are paid for their work throughout the program and awarded a Journeyman certificate upon successful completion. Project designer Chris Smith poses in front of a mural in the entryway of the IBEW Local 332 union hall. ## Showcasing Solar Technologies and Workmanship The project also serves to educate people about solar technologies, helping turn visitors into solar enthusiasts. The IBEW lettering in solar panels to catch the eyes of incoming airplane passengers may be the most dramatic example, but the entire project was designed for people to see solar technologies at work. In addition to the 200 kW rooftop solar array, a number of other interesting technologies were included, including a battery system, electric vehicle charging stations, skylights containing transparent Building Integrated Photovoltaic (BIPV) panels, and a shade awning comprised of recycled panels from the building’s original array. While the panels have degraded significantly compared to their original efficiency, they still generate a small amount of supplemental power and by shading the windows they help save energy needed for cooling. In the coming months, the building lobby will be outfitted with TV screens showing the real-time energy production of the system, as well as a live video feed of the array so visitors on the ground can see what it looks like. Those who desire will also be able to get a much closer look at the array by taking a tour of the array. As part of the building upgrades, the ladder to the roof was upgraded to give visitors easy roof access. Eventually, Local 332 plans to add a rooftop deck with picnic tables, giving members and visitors ample opportunity to get a close-up view of a solar installation. Project designer Christopher Smith explains that even though solar is becoming more ubiquitous, rooftop solar installations aren’t always very noticeable or easy for the average person to get a close look at. “You probably drive past a thousand places driving between San Jose and San Francisco that have solar, and you just don't know because you can’t see it. Even when you do see a solar installation, you usually don't get to see everything that goes into it; you don't get to ask why they made different design decisions. We really wanted that [educational] aspect.” “Aurora was key in that, because it allowed us to answer questions like, ‘Are people going to be able to get up there and walk around it? How's it going to look from up in the sky? How much is it going to cost?’ That allowed us to make sure that we weren't spending money needlessly.” Employees of Pacific Ridge Electric, a NECA member company co-founded by IBEW union member Ken Spears, work on installing a section of the array. ## Paving the Way for Future Solar Work The project has only just been completed, but already there are indications that it is generating business benefits for IBEW and NECA stakeholders. Ken Spears, co-founder and Vice President of Pacific Ridge Electric which led the project installation, has already received numerous inquiries from businesses interested in adding commercial solar arrays to their facilities after seeing the work at the IBEW Hall. And, with multiple years before California’s net zero buildings requirements take effect, the project has created an avenue for NECA and IBEW to build a strong portfolio of these types of projects in the coming years in order to be well prepared for growing demand in this area. “This project returns Local 332’s building to legendary status within San Jose,” says Smith. “There are few retrofitted Net Zero Energy buildings in the world and a project of this magnitude demonstrates the enormous capabilities and importance of IBEW electricians and NECA contractors.” Credit: NECA-IBEW Powering America.  Does your organization have an innovative solar project designed in Aurora that you’d like to highlight? We’d love to hear about it! You can submit projects using this form . Please note that Aurora Solar makes no guarantee that submitted installations will be profiled. Topics: Solar Landmarks With the holidays just around the corner, we were intrigued by the idea of brightening up an seasonal landmark with solar energy. So when we discovered that Ralphie Parker’s home from the iconic 1983 movie A Christmas Story is a real house in Cleveland, Ohio (restored to all its movie glory and open to the public!) we seized the opportunity create a custom solar design using Aurora. In our latest Solar Landmark article, we walk through the process of modeling this home, designing a custom solar installation, and analyzing the financial return on the system. Figure 1. The house from 1983 movie A Christmas Story in Cleveland, Ohio. Source: Google Maps Street View, image capture September 2016. ©2017 Google. ## Modeling "A Christmas Story House" To construct an accurate 3D model of the site as the starting point for a good solar design, we used Aurora’s SmartRoof modeling tool. SmartRoof’s ability to automatically infer the internal structure of the roof based on its outline made the process faster and easier. To build the roof model, we took advantage of the fact that SmartRoof can merge multiple roof shapes together, allowing solar designers to create complex roofs from multiple, simpler parts. First, we outlined the perimeter of the roof; SmartRoof automatically inferred the structure of the dormer on the north-facing roof plane (Figure 2 below). SmartRoof uses hipped roofs as its default, but allows designers to “unpitch” roof planes with the click of a button to model other roof types (Figure 3 below). A few minor adjustments produced a preliminary starting point for the site model in a matter of seconds (Figure 4). Figure 2. SmartRoof infers the internal structure from the roof outline. It defaults to hipped roofs (a roof type with diagonal ridge lines extending from the corners to central ridge line), but designers can “unpitch” sections to create a gable roof (see Figure 3 below). Figure 3. By right-clicking on unnecessary roof planes (resulting from SmartRoof's hipped roof default), we were able to "unpitch" them. This resulted in a traditional gabled roof as our preliminary roof model. Figure 4. Our preliminary roof model; by right-clicking on the roof polygon, we were able to specify that this roof is two stories high. We then added the roof of the porch by drawing a separate polygon which SmartRoof merged into the structure appropriately after we specified that it was at a height of one story. From there, there were a few unusual aspects of the roof that had to be taken into account to create an accurate site model, particularly that the the south-facing roof plane is comprised of planes at two different pitches, which are straddled by a dormer, as you can see in the Google imagery below. Figure 4. 3D aerial view of the Christmas Story House. As you can see, the southeast quadrant of the roof (where the two skylights are) has a much less steep pitch than the rest of the roof. Source: Google Maps imagery 2017. ©2017 Google. To model the southeast portion of the roof (or the back right section if you were facing the house) we added a separate rectangular roof segment, which SmartRoof automatically integrated into the rest of the roof structure (see Figure 5). Then, we adjusted the pitch of each of the roof faces to reflect their actual pitch. Figure 5. Adding a roof plane as a separate section which will be merged into the rest of the roof model. This enables us to specify a different pitch for this section of the roof. It’s evident from looking at the house that the roof has a very steep pitch—perfect for shedding snow in the cold winter months! But to make sure we got it just right, we used Aurora’s NREL-validated 3D Metric Estimation tool, an application of computer vision, to measure the pitch. Figure 6. Measuring the pitch with Aurora’s 3D Metric Estimation tool reveals a pitch of approximately 46 degrees. Finally, to complete the key elements of the roof structure, we inserted a dormer (using the dormer tool) and aligned the ridge of the dormer with the fold between the two roof planes. We also added obstructions to the roof to ensure that the model provided an accurate reflection where panels could be placed and what shading they would encounter. In this case, there are two skylights towards the back of the house, as well as some vents along the ridge line. Figure 7. The resulting 3D house model, after adding the south-facing dormer, southeast roof plane, and obstructions. With these adjustments, and the addition of trees on the property (to ensure correct shading analysis) we had a beautiful and accurate 3D model of the house that Ralphie would have recognized as his own: Figure 8. Two different views of the completed site model. The image on the right includes the sunpath as well as trees around that house that could cause shading. ## Creating a Custom Solar Design Aurora’s irradiance map feature made it easy to identify the best places to put solar panels (i.e. areas with the highest irradiance). Aurora takes into account local weather data and the industry-standard mathematical model to assess the available solar energy at each point on the roof. Figure 9. Aurora's irradiance engine produces a map showing the solar access value at each point on the roof surface (brighter areas indicate higher solar insolation). This remote analysis been validated by NREL to be comparable in accuracy to on-site measurements. Rather than iterate through countless potential designs, we decided to use Aurora’s AutoDesigner—which automatically identifies the best solar design for a particular site given a particular energy offset or bill savings target. Using a genetic algorithm that mimics the evolutionary process, the AutoDesigner evaluates potential combinations of panel locations, components, and stringing configurations, and identifies the option that gets as close as possible to the target while minimizing system cost. We initially set a target of offsetting 80% of the home’s energy consumption. Unfortunately, due to significant shading, and obstructions (specifically skylights) that prevented panel placement in one of the high irradiance areas, Aurora found that the most we could offset was 27% of the Parkers’ energy consumption. While not as much as we’d hoped, it could still provide some helpful electric bill savings. The resulting system from the AutoDesigner was a 2.0 kilowatt system sited on the southwest quadrant of the roof, with an estimated cost of6,030 (based on a cost per watt of $3). Having identified a design, and used Aurora’s design validation function to ensure that there were no electrical or mechanical errors (such as invalid stringing configurations, module overlap, or setback violations), we proceeded to look at the energy production and resulting bill savings of the proposed system. Figure 10. A solar system design for the Christmas Story house. Based on the design specifications and the conditions at the site, Aurora’s performance simulation engine estimates the system would produce 2,218 kWh of electricity over the course of the year, and provided a monthly breakdown of that production: Figure 11. Estimated monthly energy energy production. The resulting loss diagram detailed exactly how much energy is lost from different sources compared to ideal conditions. Figure 12. Loss diagram for the design. Although not enough to meet all of the Parkers’ electricity needs, the energy produced by this system would offer some valuable environmental benefits. Sourcing 27% of their electricity consumption with renewable solar energy would provide the environmental equivalent of taking 8 cars off the road, growing 883 tree seedlings for 10 years, or driving 82,007 fewer miles! Beyond that, solar has been shown to have valuable impacts on the property values of homes where it is installed. According to a study by Lawrence Berkeley National Labs, a solar installation can improve a home’s market value by 20%! And thanks to a local Cleveland policy that waives increased property tax assessments resulting from renewable energy investments for 10 years, the Parkers could benefit from added home value without increased property taxes. Financial Analysis To understand how much Ralphie’s family could save with solar, we turned to Aurora’s financial analysis tools. We started by applying the local utility rate for residential customers in this area: Cleveland Public Power’s Residential Rate. Ohio has net metering and Cleveland Public Power customers who go solar remain on the same rate. Unfortunately, the low cost of electricity in this area, the structure of the local utility rate, and Ohio's limited solar incentives make a financial return on a solar purchase challenging. Cleveland Public Power offers a declining block rate, meaning the per kWh price of energy actually declines after you consume over 1000 kWh! Summer rates for this rate schedule are$0.0774 per kWh up to 1000 kWh, and $0.0752 per kWh for all subsequent consumption. Under these conditions, Aurora revealed that it would take just under the full 25-year life of the system to recoup the upfront cost! Given the challenge of a cash purchase of a solar system, we decided to look at other financing options as well. Ohio law allows for power purchase agreements (PPAs), so we took a look at what the financial impacts would be if the Parkers signed a PPA agreement with a company that would own and maintain the system and sell them the resulting solar energy at a lower rate than the utility. Assuming a hypothetical PPA that would allow the Parkers to purchase the energy produced by their solar system at a rate of$0.06 per kWh, with a 2% annual escalation over a 20-year contract, the solar project looks a lot more appealing. Without having to take on the initial cost of the system, the solar installation would immediately be cash flow positive, and savings would increase over time as utility rates rise (we assume a 3% utility rate escalation).

Figure 13. Estimated cashflows from a power purchase agreement.

So there you have it: a solar design for this famous Christmas landmark! Maybe Santa will check this system off the Parkers’ lists.

After all, it’s a Christmas present the whole family could enjoy… unlike the BB Gun that Ralphie longed for, his parents wouldn’t have to worry about him “shooting his eye out”—and perhaps knowing that their electricity was coming from cleaner sources would be some comfort to Mrs. Parker when her husband insists on displaying the infamous leg lamp!

We hope this design brings you some holiday cheer and wish you a joyful season!

Cover Image Credit: © Turner Entertainment.  Leg Lamp Credit: A Christmas Story House & Museum.

Topics: Solar Landmarks

The U.S. Department of Energy Solar Decathlon is a great opportunity for college students to get hands-on experience with the design and construction of houses and solar PV systems. The collegiate competition—happening in Denver, Colorado at the time of publication—challenges student teams to design and build full-size, energy-efficient houses powered exclusively by solar energy.

The Solar Decathlon is a biennial competition that has been running since 2002, and has involved over 35,000 participants across 274 teams thus far. For each competition, up to twenty university teams are selected from a pool of applicants. Once selected, each team has a year and a half to design and build their house before bringing it to the competition site. Previous Solar Decathlon contests have taken place in Washington, D.C. and Irvine, California.

During the contest week, each team works through 10 competitions that evaluate their houses on different criteria, including hosting their rivals for a dinner party, washing loads of laundry, and taking a commute in an electric vehicle charged by their house’s solar installation. The winning team is the one that best blends design excellence and smart energy production with innovation, market potential, and water and energy efficiency. The Solar Decathlon as a whole fosters collaboration between students of different disciplines and an emphasis on sustainability.

I had the good fortune to participate in two previous U.S. Department of Energy Solar Decathlon competitions—once in 2011 as a student, and again in 2013 as a project manager. So naturally, I was excited to take a look at the designs from this year’s competition.

In this installment of our Solar Landmarks Series, we examine all 11 of the Solar Decathlon 2017 houses, what makes them special, and how they can be designed in Aurora.

The Solar Decathlon is also a unique chance to interface with industry leaders—here's me (center) chatting with then-Secretary of Energy Dr. Steven Chu about some of the energy efficiency measures in our Solar Decathlon 2011 house, CHIP. Photo Credit: Stefano Paltera/U.S. Department of Energy Solar Decathlon

### New Themes

In this year’s competition, I picked up a few themes. The contest has brought back electric vehicle driving which had been absent for several iterations of the competition, and battery-powered cars are all on display. The Energy contest has also been upgraded, now featuring net energy metering (NEM) which has encouraged concurrent energy production and usage as well as energy storage systems. The Health and Comfort contest has asked teams to bring in more plants and materials that emit fewer VOCs (a form of air pollutant). And finally, several teams came in with the modular design approach, where the prototype house brought to the competition could be scaled into a larger house in the future.

### Las Vegas - Sinatra Living

The University of Nevada, Las Vegas’s Sinatra Living house features a combination of photovoltaics and thermal heating, plus a battery pack. Deep overhangs and adjustable patio shade are great for managing the intense desert sunlight, and the inclusion of energy storage is helpful given Nevada’s less favorable net energy metering policy.

Photo Credit: Jack Dempsey/U.S. Department of Energy Solar Decathlon

To design this house in Aurora, the user should start with our SmartRoof tool and select the Flat Roof option before drawing (as illustrated below). Once the roof has been outlined, simply select one of the bottom wings and set it to “pitched,” which will tilt the whole roof up from that edge.

### Maryland - reACT

Back in 2011, the SCI-Arc/Caltech team I was on took sixth place in the Solar Decathlon on the strength of heavy insulation, a creative custom smart home app that included a complete power-down button, and some thorough weather analysis that resulted in a PV design that got us through a rainy competition week with energy to spare. The team that took first place overall that year was the University of Maryland team, which not only had a beautiful house, but a custom dehumidification system that worked with just heat from the sun and a large amount of greywater recycling.

This year, Team Maryland brings the reACT house, a self-sufficient design that also features a large amount of plant life and a central courtyard that helps collect thermal heat. The PV system is mounted on two wings of the house, and uses a combination of DC optimizers and energy storage to manage energy usage. With half the array pointed west and half the array pointed east, the system’s peak production is spread out through more of the day.

Photo Credit: Jack Dempsey/U.S. Department of Energy Solar Decathlon

To design reACT in Aurora, we need four SmartRoof structures: one for the east wing, one for the west wing, and two gable-style roof structures—one for the center of the house and another for the enclosed courtyard. The deck is optional, but I made it using a flat roof.

### Missouri S&T - SILO

Missouri University of Science and Technology is taking part in their seventh Solar Decathlon competition, this time bringing in the sleek SILO house. Large glass walls bring in plenty of diffuse light, and the 24 PV modules are more than enough to power this house through the contest. Like many other Solar Decathlon 2017 teams, Missouri S&T elected to use energy storage to manage the TOU energy pricing and the fact that exported energy is valued at a lower rate than energy bought from the grid. Both of these aspects are new to the Solar Decathlon Energy contest this year and are typical of most utility NEM rates.

Photo Credit: Dennis Schroeder/U.S. Department of Energy Solar Decathlon

SILO takes three SmartRoof pieces to design in Aurora, one for the south face with PV, one for the sloped north roof, and one for the arched middle segment. Curves take a little bit of time to model and aren’t optimal for PV installations, but it’s possible to make one in Aurora by using pitched folds with SmartRoof. After creating an outline of the curved roof face, I made only the south edge “pitched” and then inserted several pitched folds. By setting these in progressively smaller tilts, I was able to create a shape similar to the curved roof.

### Netherlands - Selficient

The Selficient house, by HU University of Applied Science Utrecht in the Netherlands, is one of the few cases we’ve seen with dual tilted systems in the Solar Decathlon, although the team from Washington University in St. Louis is also using them this competition. One cool part of this house is the modular design, which lets the installer fit different pieces of wall, floor, and roof to create different floor layouts.

Photo Credit: Jack Dempsey/U.S. Department of Energy Solar Decathlon

In Aurora, dual tilt systems can be created using the Fill Zone feature. This house appears to use a tilt of around 30 degrees, with very small row spacing. Stringing with Aurora fill zones connects modules with the same orientation to avoid mismatch in light availability.

### Northwestern - Enable

The Northwestern University team’s Enable house sports a nicely tilted PV array, a sunroom, and—a rarity in Solar Decathlon designs—a garage for an electric car. The integrated energy storage system pairs well with EV usage, which will allow the car to charge up during the night when electrical rates are more favorable.

Photo Credit: Dennis Schroeder/U.S. Department of Energy Solar Decathlon.

To create a 3D model of Enable in Aurora, we used four separate roof segments: one for the south-tilted section, a flat segment for the middle of the house, a third roof for the sunroom, and one for the back of the house. One way to ensure azimuth alignment is to copy-paste the same rectangle twice and then resize the pieces. The PV array is nicely-sized and sits at a good tilt for the intended latitude.

### Swiss Team - NeighborHub

The NeighborHub from the Swiss team (a team comprised of students from École Polytechnique Fédérale de Lausanne, the School of Engineering and Architecture Fribourg, Geneva University of Art and Design, and the University of Fribourg) has a central core surrounded by an unconditioned flexible-use space. Some other unique features include a zero-water toilet and exterior wall sections that can be folded upwards to open up the flexible space to the outside. The folding wings hold the PV modules used in this house. Most power is drawn from a series of monocrystalline panels, and a small amount of power is generated from a series of semi-translucent thin-film dye-sensitized modules. The effect is truly building-integrated PV.

Photo Credit: Dennis Schroeder/U.S. Department of Energy Solar Decathlon

The structure of the Swiss Team's house is straightforward—it just needs a single roof structure. However, the modules are not placed on the rooftop, so this design calls for roof racks to hold the modules in space, rather than placing them on the structure. I used ground mounts at tilts of 15 degrees for the folded-up section and another piece at 89 degrees for the vertical walls, in order to place the modules. Aurora’s stringing tool also permits us to connect modules in different orientations like we see in this design when the wings are opened.

### Team Alabama - surviv(AL) house

The surviva(AL) house by Team Alabama (comprised of students from the University of Alabama at Birmingham and Calhoun Community College) has a nice large south-facing roof that sports a 9.9 kW array. Each of the modules is attached to a microinverter, which will minimize potential shading losses. It also has a series of 14 clerestory windows (small windows along the top of a structure's wall, near the roofline) and a porch with a translucent overhang, which lets in more light while keeping the elements out.

Photo Credit: Dennis Schroeder/U.S. Department of Energy Solar Decathlon

Modeling surival(AL) in Aurora takes two roof sections: one for the large south face and one for the smaller north face. Each roof piece just needs one edge to be pitched, and they can be set to the same height and tilt which results in the south roof reaching a greater vertical height than the north segment.

### Team Daytona Beach - BEACH House

Team Daytona Beach (comprised of students from Embry-Riddle Aeronautical University and Daytona State College) brings in the accessible BEACH House, designed for Florida’s climate. Like the surviv(AL) house, BEACH House can be modeled with two segments, a north-facing roof and a south-facing roof. To create the extended overhang over the west portion of the house, create the 2D outline as a flat roof, and then change only the bottom-most edge to “pitched” to base the tilt of the roof off of that edge.

Photo Credit: Jack Dempsey/U.S. Department of Energy Solar Decathlon

BEACH House also features two different types of PV modules, all of which are connected to a central inverter. Aurora lets strings with different modules connect to the same inverter on different MPPTs, so there is no difficulty in modeling this design. Aurora’s module snapping functionality even snaps the different model types together without issue.

### UC Berkeley / University of Denver - RISE

The RISE House by UC Berkeley and the University of Denver is intended as a modular design, with stackable stories and communal living spaces. Only the top level is present at the Solar Decathlon due to 18’ height restrictions, but it gives a good sample of the house’s design philosophy.

Photo Credit: Jack Dempsey/U.S. Department of Energy Solar Decathlon

Modeling any version of RISE is a straightforward task in Aurora, using individual rectangles for each level of the house. We also modeled the stairs using a 45-degree sloped roof, but this has no effect on the site performance. There are also railings on the house, which can be modeled using a thin rectangular obstruction if desired.

### UC Davis - Our H2Ouse

UC Davis brings in Our H2Ouse, an incredibly water-efficient house that uses smart systems to display homeowner’s water usage. The array is segmented into two systems, one of which feeds directly to the load panel and another that connects to an energy storage system. We think the bicycle wheels that provide deck shade are also a nice touch.

Photo Credit: Dennis Schroeder/U.S. Department of Energy Solar Decathlon

Our H2Ouse can be modeled in a single polygon using SmartRoof, with the south-most edge set to a slight tilt for the whole structure.

### Wash U - St. Louis- CRETE

The team from Washington University in St. Louis brings in CRETE, a storm-proof precast concrete house with vertical planters that connect the exterior to the interior. The precast modules also have a core of insulation that helps minimize heat losses. Building the main structure of the house in Aurora is as easy as drawing a rectangle.

The PV system for CRETE is row tilted, which can be completed easily by using the standard Aurora module layout tool or a fill zone.

Photo Credit: Jack Dempsey/U.S. Department of Energy Solar Decathlon

Aurora’s CAD tool does not model overhangs so, for aesthetic purposes, I created a dummy module with a deep z-dimension to show a fake gutter piece. To enable an accurate performance simulation with these fake modules present, they are attached to a 0% efficiency inverter. An actual proposal wouldn’t need to go into as much detail, but it was fun to model the house as close as possible to the real deal.

I'm glad to see that the Solar Decathlon is still going strong in its eighth iteration (not counting the international events). Each year it seems that the houses become more innovative and competitive. There is also more emphasis on energy-efficient house design, especially important given the 10 kWdc PV system size limit, making these homes truly designs of the future.

~~~

What do you think about the houses? Comment below to tell us which one is your favorite!

The winners have just been announced, so check out our follow-up post in which we highlight lessons from the winning designs.

The Solar Decathlon 2017 competition site and all of the team's houses, modeled in Aurora.

Top photo credit: Jack Dempsey/U.S. Department of Energy Solar Decathlon

This blog post is not affiliated with the U.S. Department of Energy Solar Decathlon or any of the competing teams.

Topics: solar design, Solar Landmarks

In honor of Independence Day, we thought it was the perfect time to explore a solar design for a revolutionary hero: George Washington. Using Aurora’s remote solar design and analysis capabilities, we explored how solar can bring energy independence to Mount Vernon, the home of America’s first president.

The grandiose manor in northern Virginia was Washington’s pride and joy. He put a great deal of work into Mount Vernon , expanding the original, modest 1.5-story house his father built, and incorporating elements of British architectural style . He also spent decades developing the gardens—including an exceptional vegetable garden to meet the estate’s needs, and even adding a greenhouse for exotic plants. Even when duty called him away for long periods of time, during the Revolutionary War and later his presidency, he wrote home often detailing his vision for renovations and landscaping.

Given the pride he took in developing a self-sufficient home, we imagine Washington would have been intrigued by the opportunity to power his house with only energy from the sun.

George Washington’s home, Mount Vernon, overlooking the Potomac River.

#### Modeling the Home

The 11,028 square foot manor includes the main house where George and Martha Washington lived and hosted guests, as well as side buildings that held the kitchen and servants quarters. The home also sports an iconic front porch, known as the “piazza,” one of Washington’s personal contributions to Virginian architecture. This peaceful sitting area provides the perfect spot for taking in Mount Vernon’s breathtaking views of the Potomac River. Remarking on the vista, Washington once wrote, “no estate in United America is more pleasantly situated than this.”1

We used Aurora’s remote design features to model the house based on satellite imagery. This allowed us to identify architectural issues that would impact solar panel placement and ensure that our proposed design was well suited to the site.

A 3-D model of Mount Vernon, created in Aurora.

#### Prospecting the Roof

To identify ideal areas for the placement of solar panels, we used Aurora’s irradiance map feature to identify sunny areas (areas with high irradiance) where panels would be able to generate the greatest amount of energy.

As the irradiance map below illustrates, the “front” roof facing the Potomac River had high irradiance, as did the roof of the piazza. The kitchen also had an unobstructed roof with high irradiance. While otherwise excellent for solar, the front roof has several dormers that would obstruct the placement of solar panels and cast shade (see the purple areas along the edges in the irradiance map below).

An irradiance map of Mount Vernon’s roofs, generated in Aurora based on the movement of the sun throughout the year and local weather data. Lighter areas indicate greater irradiance.

Next, we analyzed the estate’s energy consumption patterns (load profile) in order to understand what size solar installation would be appropriate. This also allowed us to later model how the solar installation would impact bill savings.

While we didn’t have actual electricity bills or interval data for Mount Vernon, we estimated its monthly energy consumption using data from the U.S. Energy Information Administration. At 11,028 square feet, Mount Vernon is ~5 times larger than the average Virginia house.2 We approximated Mount Vernon’s monthly electricity consumption at ~5 times the average monthly consumption for a Virginia home.3 From the monthly energy consumption (kWh) data we entered, Aurora developed a representative load profile, with an estimated annual energy consumption of 71,768 kWh.

Estimated monthly electricity consumption (orange) and bill amounts (blue) for Mount Vernon, generated by Aurora’s Consumption Profile tool.

#### The Design

From there, we turned our attention to the design of the installation. As we mentioned previously, the front roof and roof of the piazza were identified early on as promising locations for solar. We proposed installations on each of these roof faces, avoiding the dormers on the main roof.

However, we wanted our design to meet as close to 100% of the site’s energy needs as possible, so we also looked beyond the main house to expand the size of the installation. We proposed a roof-mounted installation on the kitchen building, and a south-facing ground mount in an unshaded area of the property. We positioned this to the left of the main house (when facing out towards the Potomac) so as not to obstruct Washington’s spectacular river view. This resulted in an approximately 60 kW (59.97 kW) system, containing 179 modules.

An overhead 2-D view of the proposed solar design for Mount Vernon, consisting of roof-mounted installations on the main building and kitchen and a ground mount.

A 3-D view of the proposed solar design for Mount Vernon.

#### Analyzing System Performance

We then used Aurora’s performance simulation engine to get a detailed picture of how much energy this design would produce. Aurora estimates this design would have an annual production of 70,949 kWh, offsetting 99% of the estate’s energy needs.

We intentionally designed the system to offset slightly under 100%, since production in excess of a home’s annual consumption is compensated at a much lower rate.

Estimated monthly electricity production of the proposed solar design for Mount Vernon, generated by Aurora’s performance simulation engine.

Aurora’s performance simulation engine assesses how different factors reduce the energy production of the system and generates a loss tree diagram.

#### Bill Savings and Environmental Impacts

Using Aurora’s financial analysis features, we then examined how much this installation would save the estate on it’s electric bills, as well as the environmental benefits it would provide.

Mount Vernon’s pre-solar (blue) and post-solar (green) electricity bills.

#### Analyzing the Roof Structure

The first step in designing a solar installation is evaluating the site. Using satellite imagery, Aurora enabled us to create a model of the site and analyze the roof structure. Aurora’s Automatic Edge Detection algorithm, which automatically calculated the direction of each of the roof planes (the azimuths), made this process much easier.

An aerial view of the site model of Rideau Hall, as designed in Aurora. The arrows indicate the azimuth of each roof plane.

Next, we calculated the available sunlight (irradiance) at each point on the roof surface. Aurora’s shading engine allowed us to assess this remotely, with the same level of accuracy as if we had taken on-site shade measurements. To do this, Aurora takes into account the presence of trees and other obstructions (like chimneys) that would cast shade, as well as data from a local weather station. The image below shows the resulting irradiance map of the roof. Lighter sections indicate greater solar energy availability.

An irradiance map of the roof of Rideau Hall. Lighter colors indicate greater solar energy availability.

As you can see, Rideau Hall has a complex roof structure as well as a variety of obstructions (chimneys, vents, and skylights) that would interfere with placement of a solar array. Based on this, we propose placing two arrays on sections of the back of the building. This area has no obstructions and high irradiance, and would have less visual impact on this historic site.

3D site model showing the proposed 9.92 kW solar installation.

#### Simulating energy performance

Next, using Aurora's performance simulation engine, we explored how much energy the system would produce annually, given local weather patterns throughout the year. Our analysis reveals an estimated annual production of 12,079.36 kWh.

Aurora’s Performance Simulation Engine models projected energy output of the system for each month of the year.

Aurora’s loss tree diagram shows exactly where energy output is lost compared to the maximum possible output under ideal conditions.

#### Environmental Impacts

The system would offset greenhouse gas emissions equivalent to planting 4,639 trees, driving 430,749 miles fewer per year, or taking 38 cars off the road!

While the proposed installation is small, its educational reach has the potential to be great. Plus, the Canadian government has established a vision of sourcing 90% of its energy from non-emitting sources by 2030 , so meeting some of Rideau Hall’s energy needs with solar would show commitment to this goal. Add to that the direct environmental benefits the system would provide, and this sounds to us like a great deal for the government and the Canadian people.

We’re excited to see how this project develops under the leadership from Emerging Leaders for Solar Energy and Solar Head of State!

Topics: Solar Landmarks

Here at Aurora, we spend a lot of time thinking about roofs in our quest to enable any solar professional to design and sell an optimal solar project in minutes. We featured Michelle Meier, who helps roofers go solar, and we paid close attention to Elon Musk’s vision of roofs made out of solar cells.

While there are still gaps in what we know about Tesla’s Solar Roof, one of its benefits could be that it allows solar to fit on some complex roofs that are not well suited to conventional panels. Each solar tile is less than a square foot, which should allow for more flexible design.

With that in mind, for this edition of our Solar Landmark series, we set ourselves the task of finding an intricately complex home to model in Aurora. We were fortunate enough to come across one in our own backyard: the Winchester Mystery House.

#### Winchester Mystery House: A Haunted Building with a Haunting Roof

Anyone who grew up in the South Bay of California remembers their first time at the Winchester Mystery House. I went on a Friday—Friday the 13th, to be precise—and while my very rational 8-year-old mind reminded me that the doorknob rattling was probably an employee, my skin couldn’t help but crawl.

Now, decades later, I continue to be spooked by the house; not so much by the ghosts that haunt the halls, but moreso by the complex roof planes that I tried to tackle with Aurora. Still, in the name of our Solar Landmarks series, I persevered (and by that I mean I enlisted Aurora’s customer success star, Victor), and now we can exorcise the ghouls with the power of sunshine.

For those who don’t know about the Winchester Mystery House, it really is an enigmatic building. Its curious creation and elongated evolution all started with a rifle: the Winchester rifle.

Though the rifle business boomed, the Winchester family was struck with tragedy. Devastated by the untimely deaths of her newborn daughter and her husband, heiress Sarah Winchester turned to a spiritual medium who counseled her that the family was cursed by the spirits of those killed by the Winchester rifle. Believing that the unceasing construction of her house would appease the ghosts, Sarah enlisted craftsmen to build, alter, and demolish 24 hours a day, 365 days a year for 36 years.

Now, the Winchester Mystery House serves as a public oddity that haunts to this day. Staircases lead to nowhere. Cabinets the size of apartments share a wall with an inch-deep cupboard. Trap doors open treacherously onto the garden below and doors open to reveal walls.

But what if it wasn’t just a spooky attraction, but a showcase of solar innovation?

#### Assessing the Roof’s Solar Potential

Fortunately modeling the Winchester Mystery House in Aurora, while complicated, did not take 36 years like the original building. We started out by drawing over the satellite image in our software. We were thankful to have Aurora’s Automatic Edge Detection algorithm, which automatically calculated what direction each of the roof planes faced (the azimuths). There were well over 200 unique azimuths — we couldn’t imagine doing all that by hand!

An aerial view of the site model of the Winchester Mystery House, as designed in Aurora. The arrows indicate the azimuth of each roof plane, automatically calculated by Aurora’s Automatic Edge Detection feature.

Once we were done with the 2D model, we tailored our model in 3D space. Fortunately, this building has LIDAR data, which allowed us to ensure our model perfectly matched the actual Winchester Mystery House’s roof height and roof slopes.

Aurora’s site modeling capabilities allow you to view satellite map imagery alongside your 3D model, making it easier to ensure accuracy.

The final step in the process was to assess the energy potential of the roof. It is important to note that at the time of publication, there is a dramatic difference in the cost of Tesla’s energy-producing Solar Roof tiles ($42 per square foot), versus its non-energy producing tiles ($11 per square foot). Therefore, we wanted to make sure we are only placing the energy producing tiles in the most important locations. The final result was a gorgeous and informative heat map (below) that outlined the building’s solar potential.

Irradiance map showing the solar potential of each part of the Winchester Mystery House’s roof.

Aurora’s system design portal also provided us with useful information on the available roof surface area. We found that the roof has a surface area of 33,234 square feet. However, we know not all of this area is a good fit for the energy producing roof tiles. For example, the Solar Roof tiles can only be installed on a surface that has at least a 3:12 or steeper slope. This ruled out the entire roof on the north side of the site (shown below) which, despite being relatively shade-free, was completely flat.

Aurora’s irradiance map feature provides solar access and irradiance values for each point on the roof.

To determine which areas we wanted to place energy producing tiles on, we set the following criteria:

• The roof had to have a pitch of 25 degrees or more
• The roof area has to have at least 500 contiguous feet
• The average Solar Access percentage for the roof surface had to be greater than or equal to 80%

After we filtered by this criteria we found only 6,994 square feet of the Winchester Mystery House’s intricate roof were solar eligible, or approximately 21% of the surface area.

#### Calculating Solar Roof Returns

To calculate the financial benefits of the Solar Roof we used Tesla’s online calculator. There are three key inputs into the calculator:

1. The building’s current average monthly utility bill
2. The total roof area
3. The percentage of the roof area that will be covered by energy-producing tiles

We used an estimate of 15,000 kWh per month (approximately 15 times more than the average energy consumption of a 2,000 square foot American home). We entered this value into Aurora’s Consumption Profile Tool which gave us an estimated monthly bill of $5,825 (see below). With the input of energy consumption or bill amount for a given month (or as many as you have data for), Aurora’s Consumption Profile tool can generate estimated monthly utility bill and energy consumption data for the full year. (The tool can also utilize Green Button Data.) As discussed above, we have a total roof area of 33,234 square feet, of which about 21% of the surface area is a good fit for solar. The Tesla Solar Roof requires a Powerwall battery which was included in our analysis. The final result was an extra$186,600 dollars earned by the Winchester Mystery House over the next 30 years. Apparently, that’s more than enough money to hire a team of over 300 fully qualified ghost hunters to help resolve the secrets of the Winchester Mystery House!

Tesla’s Solar Roof calculator, reflecting the values of our analysis for the Winchester Mystery House.

Whether you believe in ghosts, or are more frightened by the thought of the monstrous electricity bills the Winchester Mystery House must have, we hope this landmark solar design makes this spooky landmark a bit brighter.

If it’s the idea of modeling a roof like this that sends a shiver down your back, sign up today for a demo of Aurora’s solar design and sales software to see how our remote solar design capabilities can save you time, money, and stress.

Have ideas for future solar landmarks? We’d love to hear from you. Tweet @aurorasolar with the hashtag #SolarLandmark to submit your suggestions!

Acknowledgments: This article is the result of contributions from several members of the Aurora Team. Special thanks are owed to Customer Success Analyst Victor Ionin for modeling the Winchester Mystery House in Aurora’s software, and COO Samuel Adeyemo for analysis of the solar potential of the site and financial analysis of the proposed project.

Topics: Solar Landmarks

In our Solar Landmarks series, we explore the world, all from the comfort of the Aurora office in Palo Alto. We will “travel” to famous landmarks and investigate their potential for solar energy generation.

For each site, we will go through the entire solar design process—from determining an optimal component layout based on the roof structure and shading losses all the way to a cost analysis with various financial options.

## Buckingham Palace

A 3D model of Buckingham Palace, created in Aurora.

The UK has recently made some decisions that have left its solar industry struggling to grow. Firstly, it surprised the solar market by cutting the solar feed-in-tariff by 65%, then it surprised the financial markets by voting to leave the EU. This leaves us wondering: what can we do to help highlight the environmental and economic benefits of solar in the land of the Union Jack?

What better way to make a statement than by helping Her Majesty The Queen go solar? We will perform a preliminary site assessment for Buckingham Palace, which was recently listed as the world’s most expensive home with a value of over $1.25 billion (we used an exchange rate of 1.25 US dollars to 1 Pound Sterling throughout this analysis). ### Balancing a Budget: Some Background on Royal Finances Before we get out over our skis, our first step is to qualify the lead. While we suspect they are good for it, we need to make sure that the Royal Family has enough cash, or adequate credit, to afford a solar installation. We also want to get a sense of how much they are spending on electricity in order to ballpark how big a system they would need. At the time of writing the Royal Family has not returned our request for a credit check, however we are able to retrieve information on their income from The Sovereign Grant Annual Report. For those in the US, this is essentially their equivalent of a W2, except it is measured in millions of pounds and read to members of parliament. And it is prepared by the delightfully named Keeper of the Privy Purse, as opposed to Turbo Tax. Here are some fun facts that we learn by combing through the Annual Report: • The Queen is technically the Head of the Armed Forces, the Judiciary, the Civil Service and is the Supreme Governor of the Church of England (you thought you were wearing multiple hats). • The Queen has met eleven of the last twelve US Presidents (we guess even The Queen needs a good excuse to use the good silverware). • The Queen has sent 232,000 congratulatory telegrams to centenarians on their 100th birthdays (yes, telegrams—we had to Google them too). • The Queen pays 50% of her suppliers within 15 days of receipt of invoice, and 95% of them within 30 days of receipt of invoice (an installer’s dream!) • The Royal Household had income of approximately$65 million in 2015.

We think they’re good for it.

The Report records that Buckingham Palace consumed 4.3 million kWh of electricity from the utility grid (that’s about 4 times the estimate we used for the White House, which is a bit more secretive). Based on the utility rates available for the Palace’s area code, we calculated an average day-time rate of approximately $0.15/kWh for daytime energy usage, and$0.07/kWh for nighttime use. Great, we are ready to get started designing!

### Prospecting the Roof Structure

Buckingham Palace’s floor area covers more than 19 acres! The site itself dates back to the seventeenth century, although the modern building was built between 1820 and 1828. We started by taking a look at the irradiance and shading characteristics of the roof.

The irradiance map, generated in Aurora, reveals that south facing surfaces have the most sunlight, and that most shading comes from adjacent buildings.

With a glance at the irradiance map, we quickly see why 4 million British tourists make the annual pilgrimage to the relatively sunny United States: An average irradiance of about 1000 kWh/year is even less than Maine’s, which weighs in at about 1,200 kWh/year.

Unsurprisingly, as seen by the lighter colors on the irradiance map, we found that south facing roof surfaces were the best locations for a solar installation. Unfortunately, the same blocky neoclassical architecture that draws legions of tourists every year also results in roof surfaces that have few uninterrupted areas for placing modules.

### Carport or Ground Mount?

With few options for a roof installation, we have to look to the ground game. Fortunately, in addition to having over 19 acres of floor space, Buckingham Palace has over 40 acres of garden. We are going to look at installing a carport or ground mount system in the backyard. (After all, how much lawn does one really need for croquet?) An elevated structure will still allow for plenty of space for picnic tables for afternoon tea. We can use pipe racks in a 404 kW system and TrinaPeak 330W modules with cell-string level power optimizers, allowing us to mitigate the effects of shading from nearby trees.

### Simulating Energy Performance

Taking into account system loss factors such as soiling, snow, and shading, and running a sub-module performance simulation, we estimate that this solar system can produce 330,195 kWh of electricity in its first year of operation.

Energy production and loss diagram

Our loss tree diagram shows exactly where we are losing energy and how we might improve our design—for example we see inverter clipping losses of 0.8%.

## Financing options

Now that we have established that we can provide shelter for the visitors to Buckingham Palace, and offset approximately 10% of the Palace’s energy consumption, let’s see the financial return of this project.

The UK has a feed-in tariff system where the system owner is paid a credit for any energy she produces, whether it is for self consumption or for export to the grid. At the time of writing, for a 404 kW system, the rate is approximately $0.02/kWh. Adding this to the baseline energy cost of$0.15/kWh, we have a total combined feed-in tariff rate of $0.17/kWh (to simplify the problem we are ignoring the time of use and export bonus rates). In our first attempt we assume that the Royal family dips into their savings to pay for this solar installation with cash. #### Cash Financed Hmm, a return of 6.55% and a Payback Period of over 14 years is not anything to write home about. The Queen probably has a pretty good FICO score though, and at a very minimum, she could post her house for collateral. #### Loan Financed After the Brexit vote bond rates are close to historic lows, so it should be a good time to lever up. Let's model a loan for 80% of the system cost at a rate of 2.2%. Debt does the trick! We are now looking at a very respectable sub 7 year payback, with a return of investment of almost 16%. That's enough to earn a famous Royal Wave: ## Notes According to UKPower.co.uk, electricity rates in Buckingham Palace postal code are 11.76p (incl. VAT) per kWh during the day, and 5.63p (incl. VAT) at night, with a standing charge of 16.6p a day. We make the following financial and system design assumptions: • Annual Degradation Rate: 0.25% • FIT Inflation Rate: 3% • Inverter Life: 13 years • Inverter Replacement Cost:$.3/W
• Project Life: 25 years

The Inflation Rate was calculated by averaging the annual utility bill increase from 1997 - 2015. The utility bill information was obtained from the UK Department of Energy and Climate Change: https://www.gov.uk/government/statistical-data-sets/annual-domestic-energy-price-statistics

Topics: Solar Landmarks

In our new series Landmark Solar Design, we will be exploring the world, all from the comfort of the Aurora office in Palo Alto. In each post, we will ‘travel’ to a famous landmark and investigate its potential for solar energy generation.

For each site, we will go through the entire solar design process - from determining an optimal component layout based on the roof structure and shading losses all the way to a cost analysis with various financial options.

With election season in full swing, we couldn’t think of a more appropriate site than the White House for the inaugural post of our series. We have prepared a preliminary site assessment and proposal for President Obama to look at in the last few months of his term (or the National Parks Service since they’re in charge of maintaining the White House grounds).

## A brief history of solar energy at the White House

President Jimmy Carter on the unveiling of his solar thermal panels in 1979.

The White House is no stranger to the benefits of solar, and has had solar systems in place since 1979.

• 1979 - 32 solar thermal panels are installed on the roof of the White House by President Jimmy Carter. He predicted that solar could “be a small part of one of the greatest and most exciting adventures ever undertaken by the American people.”
• 1986 - Carter’s solar panels are dismantled by the Reagan administration.
• 2003 - Under the administration of Pres. George W. Bush, the National Park Service (NPS) oversaw the installation of a 10kW PV system, along with two thermal solar systems for the White House swimming pool.
• 2013 - President Barack Obama orders the installation of 6.3-kW of PV panels on the roof of the Obamas’ executive residence. The system is estimated to have an eight year payback period.

While 6.3-kW is a typical PV size for an average American home, the White House roof has untapped solar potential that could power administrative offices and facilities in the complex. The estimated yearly electricity consumption of the White House is around 852,500kWh, based on average kWh/sq ft of office buildings.

Given the size of the building, a commercial scale installation would be appropriate. To meet those electricity needs, we found more spots for solar panels on the roof of the White House.

## Analyzing the roof structure

The White House has three main sections:

• Executive residences - where the Obama family lives
• West Wing - presidential offices
• East Wing - office spaces for the First Lady and her staff

•
• And the two colonnades that connect the wings to the original central residence.

The grandiose three-story executive residence has various obstructions on the roof, making it difficult to place large arrays there in our solar design. Its height also results in shading on the surrounding structures.

The irradiance map reveals that the West Wing is a hotspot, not just for political activity but also for solar access.

Based on solar access values from nearby weather stations (TMY3), we see that East and West wings have the highest solar energy potential, followed by the unshaded regions of the East and West colonnades.

## Solar system layout

Using Aurora’s autofill tool, we placed a total of 980 American-made SunPower solar modules on both wings and colonnades, for a 320-kW system. (For the colonnades, we only put solar modules where the annual solar access was more than 80%.)

Spec Table

 System Size 320-kW Panel Tilt 20° Row Spacing 2.0 ft Number of Modules 980 Estimated Project Cost $1,000,000 ## Simulating energy performance Taking into account system loss factors such as soiling, snow, and shading, our performance simulation engine estimates that the solar design can produce 358,123 kWh of electricity in a year. ### Electricity offset The solar energy production would offset almost 43% of the White House’s electricity consumption, significantly reducing its carbon footprint. ## Financing options Now, how should the United States government pay for the proposed solar system we designed? Energy independence: Minimal shading across panels on the White House roof on the 4th of July Cash If the White House paid for the entire system upfront, the payback period would be 11.65 years, or 2.91 presidential terms. Not ideal. Loan Thankfully, the US government can get a pretty good deal with financing options. After all, federal infrastructure development isn’t quite complete without some healthy debt. Let’s assume Uncle Sam takes out a loan consistent with its borrowing history. The loan covers 100% of the project cost and they don’t pay any dealer fees. The loan interest rate is benchmarked to the current 30 year treasury yield rates (USGG30YR:IND via Bloomberg). That looks like a much better investment! Because we predict utility rate escalation at 3.5%, the deal only gets better as time goes on. There you have it: Clean Energy Savings for All -- of the White House. It’s a sound business decision that would entice any candidate. Notes: • We assume the cost is$3.25/W.
• We assume that the White House is on the Potomac Electric Company’s Residential Time Metered (RTM) schedule, with 3.5% utility escalation rate, and 5c/kWh for Net Surplus Compensation.
• We assume that the White House roof is structurally sound enough to support the weight of the solar generation system.

Topics: Solar Landmarks