Solar Cell Efficiencies Continue to Rise

Solar cells seem to have a bad reputation for operating at very low efficiencies. It's true that a standard silicon solar cell will convert somewhere around 16% of the visible light that hits its surface to electricity. This number is much higher than the efficiencies of solar cells of only a few years ago, however, and the trend of increasing solar cell efficiency is well-established and expected to continue.

The current record efficiency for a solar cell is 40.7% (see story here)! That number is almost unbelievable. These cells are multi-junction concentrator cells, and they may be a year or two from large-scale production, but the performance of all types of solar cells has been steadily increasing.

The potential for solar cells to increase in efficiency differentiates solar from other electricity generation methods. No other industry has such great potential for improvement. I may be mistaken, but I do not see similar trends in efficiency in coal, nuclear, natural gas, or other fossil-fuel based methods for creating electricity.

And because of the simplicity of the entire solar electricity generation process, an increase in conversion efficiency has a direct impact on the overall efficiency of the generation system. The two most significant effects are:

1. A doubling of solar cell efficiency means that only 1/2 as much solar cell area is required to generate the same amount of electricity.
2. A doubling of solar cell efficiency also means that only 1/2 as much silicon (or other light-converting material) is required.

The first effect reduces the footprint required for more powerful solar installations. This makes solar a legitimate option for more applications where space is limited.

The importance of the second effect cannot be overstated. The limited supply of silicon available for solar cell production has kept prices high over the past few years. New silicon production capacity is being added, and the supply bottleneck will begin to open up over the next two to three years, but being able to get the same amount of power out of less raw material may drive the price of solar power down more quickly than any other development in the field.

To wrap it all up, here's a chart that should give all of us hope. It shows the efficiencies of a wide range of solar cells achieved in laboratory conditions over the last 30 years. Some types of cells have done better than others, and these lab-grade examples perform better than what we can get off the shelf for the next few years, but the trends and implications are clear.

This image comes from the National Renewable Energy Laboratory at http://www.nrel.gov/

Makes me feel all warm and fuzzy inside, you know?