Could Solar Panels on Your Roof Power Your Home?
Researchers at MIT are investigating how to turn houses in Cambridge, Massachusetts, into mini-power plants
- By James Holloway
- Illustration by Sarah Wilkins
- Smithsonian magazine, March 2013, Subscribe
The biggest obstacle to the widespread adoption of solar power is the simple homeowner question: Will I see a return on my investment? In response, major cities across America have unveiled online “solar maps” that allow residents to type in their address and receive estimates of how much money they would save on their electric bill per year.
The most accurate solar map in the United States is one being used by residents of Cambridge, Massachusetts. According to the map’s creators, the MIT Sustainable Design Lab and the design workshop Modern Development Studio, their solar mapping tool can provide energy-saving estimates that fall within 4 to 10 percent of real-world measurements. “Looking at these other maps and all the assumptions that were made, I said, ‘I think we can do a lot better,’” says MIT Associate Professor Christoph Reinhart, who led the underlying research.
MIT created a topographical map of the city based on nearly one million data points gathered by aerial flyovers using LiDAR (Light Detection and Ranging), which measures the distance to an object by bouncing a laser beam from it. This data not only allows the researchers to take into account roof shapes (flat, angled), but even the extent to which nearby trees and buildings block or reflect sunlight.
And then there’s the weather data. Solar panels generate energy not only from direct sunlight, but also from diffuse light across the sky. MIT dug into historical weather data to ascertain sky conditions (overcast, sunny) over Cambridge for every hour of a typical year. The researchers also plundered the weather data for hourly temperature changes. Higher temperatures increase the resistance levels of electric circuits, leading to a decrease in voltage output. “Scientifically, that’s probably the biggest overall correction factor,” says Reinhart. “We see that in the summer, when we think they generate most, the solar cells actually have less efficiency for many roofs.”
The product of all this data is an online map of 17,000 rooftops, using Google Maps and its satellite imagery. On every roof, the solar tool overlays a spectrum of color-coded dots that indicate the fitness for solar power for every 25 square feet. Residents can obtain more detailed data by clicking on or typing in their address. For instance, one address reveals that 611 out of 2,863 square feet of roof space is optimal for solar panels. The actual cost of installation, with federal and state tax credits, would be $33,506. Annual savings would be $4,952. The map also provides comparative financial returns on other investments, such as gold. And an environmental over- view reveals an annual reduction of seven tons of carbon emissions.
The map is still in the prototype phase, but once it’s ready for prime time, the MIT team says it will work with other cities to develop maps of their own. “The end goal,” says Modern Development’s Eduardo Berlin, “is to help consumers capture every feasible kilowatt.”
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Comments (8)
MIT is doing a great job helping consumers to understand that solar is feasible at a multitude of different latitudes. Germany (which receives less sunlight than Canada) is a clear leader in solar so it's great that MIT is helping to get the word out. Understanding the economics of solar is critical to widespread adoption. EnergySage has a great primer that helps people to understand what the return on their investment could be ( https://www.energysage.com/why-clean-energy/its-a-great-investment ) Often times, investments in solar energy deliver returns well in excess of traditional investment vehicles such as stocks or bonds. Breaking down these information barriers will go a long way toward making solar mainstream.
Posted by Eileen Newman on April 5,2013 | 10:09 AM
Re: Power to the People - How much electricity can your roof produce? In the first paragraph, a simple question is asked, “Will I see a return on my investment?” Then the article goes on to not answer it. Well, let me. You will see a return “ON” your investment the next day the sun comes up. How large depends on the size of your array. You will receive a return OF your investment when you eventually sell your home. Do not overcomplicate this. I have been living in what was then a brand new 1,800 sq. ft. home, off the grid, since 1998. I have not paid my local utility (Pacific Gas & Electric) a single dime in all those years. Every single year, my dividend on this investment has gone up. Why? Because electric rates have continued to rise. Guess what? I don’t care. I’m oblivious to this problem. To read about what we did and how we did it go to http://www.rtdouse.com and click on the link to our “off grid” home.
Posted by Richard Douse on March 19,2013 | 12:13 PM
Wow! How exciting! The EnergySage Marketplace also allows people considering solar to get quotes from installers, making the process even easier. These two things together could really change the market!
Posted by EnergySage on March 3,2013 | 04:26 PM
Great Article! Here's a link to the actual map: http://www.cambridgema.gov/solar ...and here's a link to Mapdwell's homepage: http://www.mapdwell.com
Posted by Eduardo on March 1,2013 | 06:35 PM
The map is online at, http://www.cambridgema.gov/solar/.
Posted by Alstan on February 28,2013 | 08:18 AM
Is this map available for people to see? How can we access this map? Could you please provide information on who can be contacted for this information.
Posted by Debashree on February 27,2013 | 09:34 AM
This is awesome! Could you please add a link to the actual map?
Posted by Nicholas on February 26,2013 | 05:10 PM
Thank you. I will share this.
Posted by Lisa Bell on February 22,2013 | 12:33 PM