Professor Reynolds is cautiously pollyannaish on the future of solar energy. An MIT professor working on "quantum dot photovoltaics" suggests we could supply all US energy needs by covering 2% of the continental US with photovoltaic systems working at 10% efficiency. But as Reynolds notes, "Two percent is a LOT of land." Indeed it is. The Truth Laid Bear figures it as, well, Georgia. And asks, "So: who's for paving over Georgia?"Now, I'm no mathematician. And I know less than nothing about solar energy. But I thought to do some figuring myself. My (admittedly back-of-the-envelope) calculations suggest the MIT man was asking for a bit more real estate than he needed.
About 1 kilowatt of solar energy per square meter reaches the ground. So a photovoltaic cell working at 10% efficiency (which is pretty standard, apparently) produces .1 kilowatt, or about 876 kwh per year. The US uses about 3500 billion kwh a year. Which means we'd need about 3,995,443,800 square meters, or about 4000 square kilometers of solar panels to cover current energy use. The total area of the US is 9,629,091 square kilometers, of which 9,158,960 square kilometers is land. Figuring we'd only put solar cells on land, I put 4,000 square kilometers to be about .04% of the of the United States. Or rather, a hair more than Rhode Island.
That's still a lot of solar cells. But at least it sounds remotely plausible.
1 comment:
pretty interesting. i was curious about the discrepancy b/t your calculations and the prof's. it looks like the value 1kW/m^2 is for a sunny day at the equator (from wiki). don't know how much of the difference that would account for, though.
Post a Comment