A couple of years ago, I briefly tried to sell solar that I thought was a wonderful deal. Nothing down, cheaper than utility, and I had it myself, so I knew it was great. Maybe I’m not meant for sales, but my results led me to the conclusion that only thing that would spread solar widely would be directly paying people with perfect roofs.
The only people who wanted solar had tiny little steeply gabled cottages in Berkeley with gigantic trees draped over them and $50 electricity bills. People out in sweltering Pleasanton, with $500 swimming-pool-driven electricity bills and the perfect roof for solar could give a damn. But actual income from their roofs would change that. Everyone likes to earn money.
The U.K. has borne out my theory, essentially Al Gore’s “electranet” idea. The country’s feed-in tariff (FIT) that pays cash for electricity production has taken off like a rocket, with over 100,000 separate installations totaling over 400 MW of capacity by the end of 2011—about the size of an average coal plant.
To help the Brits assess their rooftop income potential, the aerial mapping company Bluesky in the U.K. has mapped over 500,000 roofs, using high resolution aerial photography combined with 3D data to determine the size, aspect and gradient of individual properties.
The company is a specialist in aerial imaging and remote sensing data collection and processing for a variety of industries. (One of the more intriguing things they offer is thermal heat loss measurements from each building across entire towns!)
Bluesky’s solar potential mapping is much more comprehensive than any I’ve seen, enabling much more than just aerial measurement of roof surfaces.
- It includes both the pitch of each gable on the roof and which way it faces—south, east, whatever—that are key to knowing what the solar production on each of the gables would be.
- It offers specific output estimates based on the general European PVGIS insolation calculations (how many sun-hours your region averages annually) but with much more local microclimate detail.
- It includes the estimated number of panels that will fit on each roof—and you can specify a particular panel—and calculates how many in that size.
- It shows (in red) gables that are too steep or face the wrong way—or even where just dormers interfere with light flow. It even shows where you would not want to put panels over skylights, or obstructions like vent pipes.
Based on all of these things, it calculates each roof’s monthly and yearly output in kilowatt-hours.
Roofers and solar firms in the U.S. also use aerial mapping that is much more detailed than Google Earth to see where pipes, air conditioning equipment, vents and other small nuisances on roofs obstruct potential solar panel placements. But Bluesky’s program is offered directly to the general public, to help Brits calculate their return on investment for Britain’s FIT. “Installing solar energy panels is not about short term gains,” says Rachel Tidmarsh, Bluesky managing director, “but rather a long term return on investment for both the property owner and the environment.”
With the U.K. now reducing its FIT payments—they threatened to break the budget—it is more needed than ever.
“If tariffs are reduced,” she added, “it becomes more important than ever to get an accurate and independent assessment of a property’s suitability in order to fully understand the balance between installation costs, energy savings and potential income.”