Why can't solar panels produce 1 Kw per 1 square meter? This is the energy of the Sun's radiation per square meter on Earth but solar panels don't come close. Why can't we trap all that energy? Where is the rest of the energy going?
[Physics] Why aren’t solar panels efficient
earthelectromagnetic-radiationenergysolar-cellssun
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The colour you're seeing is from the very small fraction of light that the panels are reflecting. The vast majority of light is being absorbed to generate electricity.
Why some of the panels appear slightly blue while others don't I don't know. Presumably there must be small differences in the manufacturing process. The absorptance of solar panels does fall off at the extreme blue end of the spectrum, so you would expect the reflected light to have a blue tinge. A quick Google found this article that includes a typical absorption spectrum:
The purpose of solar cells is to generate electricity. This can replace the electricity generated by burning fossil fuels for electricity. The fact that it's becoming practical to run vehicles on electricity means we can also replace the fossil fuels burned to power vehicles, which makes things even better.
But let's concentrated on generating electricity. Your analysis ignores two things, one minor and one absolutely crucial:
- The minor point: Generating electricity by burning fossil fuels also adds heat to the planet. For example, only about 1/3 of the energy liberated by burning coal in a coal power plant is turned into electricity; the rest is waste heat.
- The major point: Fossil-fuel power plants continually produce CO2.
This post on RealClimate does an excellent job of going through the details. To take an unrealistic extreme case, they assume that solar cells are perfectly black (albedo = 0), and they ignore the fact that real solar cells are sometimes installed on already dark surfaces (such as roofs). In order to generate the current world electricity supply of 2 trillion watts, perfectly black solar cells would add about 6.7 trillion watts due to waste heat. As they point out, the efficiency of fossil fuel plants means 2 trillion watts of electrical power would be accompanied by about 6 trillion watts of waste heat.
So if you replace fossil fuel power plants with solar-cell power plants, you don't really change the waste heat production.
But you do change the CO2 production, and that's crucial, because the heat added to the atmosphere by adding CO2 is orders of magnitude larger than the waste heat from the power-generation process itself. (This is a continuing process: every second you run the fossil-fuel power plants, you add more CO2 to the atmosphere.)
... by the time a hundred years have passed, the heat trapped each year from the CO2 emitted by using coal instead of solar energy to produce electricity is 125 times the effect of the fossil fuel waste heat. And remember that the incremental waste heat from switching to solar cells is even smaller than the fossil fuel waste heat. What’s more, because each passing year sees more CO2 accumulate in the atmosphere, the heat trapping by CO2 continues to go up, while the effect of the waste heat from the fossil fuels or solar cells needed to produce a given amount of electricity stays fixed.
(You can, if you like, argue that getting rid of electricity generation entirely -- closing all power plants, solar or fossil-fuel-powered -- would be marginally better than converting electricity generation to solar. But that's a very small difference, and not really an option if you want to continue to have some kind of human civilization on the planet.)
Best Answer
The Wikpedia article on solar cell efficiency gives a number of reasons that solar cells are less than 100% efficient. One of the large ones is the thermodynamic limit-a photon of less energy (longer wavelength) than the silicon band gap cannot produce an electron and one with higher energy can only produce as much voltage as the band gap. Even if you could choose the band gap, this limits efficiency to 34%. There are many more, smaller, factors that reduce the overall panel efficiency to around 20%.