Bonus: Solar panels help keep buildings cool, reducing A/C needs
Cooling effect equivalent to 5% discount on solar panel priceA great thing to do to improve the energy-efficiency and comfort of a building is to plant trees in strategic positions around it so that, when they are mature, they provide shade, keeping the place cooler than if it was fully exposed to the sun (and in northern latitudes, the trees lose their leaves during the winter, letting the sun through to heat things up).
But trees aren't the only way to keep a building cooler. Solar panels, when mounted on a roof, also provide valuable shade on top of generating clean electricity. Researchers at the University of California San Diego decided to have a closer look at the panels' cooling effect to see how big it is and what kind of panel orientation provides the biggest benefits: "Using thermal imaging, researchers determined that during the day, a building’s ceiling was 5 degrees Fahrenheit cooler under solar panels than under an exposed roof."
the amount saved on cooling the building amounted to getting a 5 percent discount on the solar panels’ price, over the panels’ lifetime. Or to put it another way, savings in cooling costs amounted to selling 5 percent more solar energy to the grid than the panels are actually producing— for the building researchers studied. [...]
Rather than the sun beating down onto the roof, which causes heat to be pushed through the roof and inside the ceiling of the building, photovoltaic panels take the solar beating. Then much of the heat is removed by wind blowing between the panels and the roof. The benefits are greater if there is an open gap where air can circulate between the building and the solar panel, so tilted panels provide more cooling. Also, the more efficient the solar panels, the bigger the cooling effect, said Kleissl. For the building researchers analyzed, the panels reduced the amount of heat reaching the roof by about 38 percent. (source)
Of course, solar panels aren't as effective as reflective roof membranes/paints/materials, but nothing prevents people from combining the two technologies, and it's good to know that solar panels provide this side benefit that has been rather overlooked so far.