Jackson Miller

For the past couple of years I have had a question running around in my head and it won’t go away. Maybe by posting it here someone can point me in the right direction to understand it.

If every rooftop in a city was covered with solar panels, would it reduce the overall temperature of the city?

Now, I freely admit that I am way out of my league on this one. There are probably some people out there reading this and laughing at how obvious the answer is. The thing is, I haven’t heard this question asked before.

I have some basic understanding that heat and energy are related. Engines that run hot are less efficient than engines that run cool. I think that the heat (thermal energy?) in that case is wasted energy. I also know that the reflection of the suns rays warms the planet.

So, does it not hold true on some level that solar panels capture the energy from sunlight and therefore the light that is captured is not released as heat? Could it be a measurable amount?

I did a little research tonight and I know there is a relationship between heat and energy. I know that we cannot create energy from nothing. I know that the measure of electricity (Watts) is the rate of heat transfer (Joules per second).

So, does it not hold that widespread use of solar energy would not only reduce the emissions of green house gas, but it would also have a cooling effect that would counter the heat retention effect of some of the greenhouse gasses that are already in our atmosphere?

Can you help me understand this better?

Update: I may have found more information that helps. A Photovoltaic-Thermal System (PV/T) not only converts sunlight into electricity, but also captures the residual heat in a way that both the electricity and heat are usable. I think that supports this theory b/c “residual heat” seems to indicate that some heat is lost lost by standard photovoltaics (though maybe not all). As PV systems become more efficient will there be less residual heat?