Improving Solar Energy Conversion

After reading an article in Physics Today, it is easy to see why many view solar power as a panacea for our growing energy needs. "The enormous power that the Sun continuously delivers to Earth, 1.2 × 105 terawatts, dwarfs every other energy source, renewable or nonrenewable." For a comparison, an estimate of the recoverable oil on Earth is approximately 3 trillion barrels containing "1.7 × 1022 joules of energy, which the Sun supplies to Earth in 1.5 days." Our current technology, though, is woefully inadequate to tap into the potential of this rich energy source.

The article outlines the current state of the art and future directions for three areas of development:

• direct conversion of light to electricity (solar cells),
• using solar catalysis in the making of fuels (natural or artificial photosynthesis), and
• utilizing solar radiation as the heat source for heat engines, tapping directly into our current technology.

Currently, these technologies have conversion rates of less than 18%, 1%, and 30%, respectively, even though "the theoretical limits suggest that we can do much better."