Advocates of renewable energy often cite the enormous amount of energy passing from the sun to the earth as evidence that their preferred electricity sources can serve all human needs. While feasibility remains an issue, the general claim is unassailable. Indeed, it can be derived from first principles:
- We have been merrily burning coal, oil, and natural gas for hundreds of years.
- This has produced both heat (which does work and eventually dissipates into the atmosphere) and greenhouse gasses.
- The latter increase the share of solar energy that remains trapped in the atmosphere, thus significantly heating the planet.
- While local heating can arise from the direct heat of fossil fuel burning, this is not a significant planetary phenomenon.
- Thus, the extra solar energy being retained by the planet because of greenhouse gasses is much greater than the amount of energy being added to the planet by the burning of fossil fuels and the fission of uranium.
- As such, the total energy incoming from the sun must be much greater than the total energy being produced through fossil fuel burning.
Of course, the energy in fossil fuels also came from the sun in the first place – back before the organic matter that comprises them got buried underground and chemically altered through heat and pressure.
To make things a bit numerical, consider this. The total amount of incoming solar energy at any point in time is about 174 petawatts (10^15 watts). That is 1.524 zettawatt (10^21 watt)-hours per year of energy. In comparison, global electricity production from thermal sources is about 11.4 petawatt-hours. That is 130,000 times less than the quantity of solar energy, despite the fact that we are burning far more fossil fuels each year than are formed during that span of time.