I have been following the solar power news for some time out of personal interest. It seems to me solar power is likely to play an important and growing role in meeting the world’s energy needs. It is environmentally friendly, very modular (you don’t need a huge energy plant to use solar, unlike, say, nuclear), and can be unobtrusive.

Also – we are being bathed in more solar energy than we currently need to run the world. According to Wikipedia:

• The total solar energy absorbed by Earth’s atmosphere, oceans and land masses is approximately 3,850 zettajoules (ZJ=10^21 joules) per year.
• Global wind energy at 80 m is estimated at 2.25 ZJ per year.
• Photosynthesis captures approximately 3 ZJ per year in biomass.
• Worldwide electricity consumption was approximately 0.0567 ZJ in 2005.
• Worldwide primary energy consumption was 0.487 ZJ in 2005.

That means that the Earth receives 7905 times the energy from the sun as we currently use. This means that we would need to cover only 0.12% of the earth with 10% efficient solar panels to meet current needs – if we ran everything on solar.

This sounds very impressive, and certainly the potential of solar is obviously huge – hence my interest. But there are many practical considerations, all of which can be summarized in the concept of cost-effectiveness. Right now – today – solar energy is not quite ready for prime time. There are certain applications that make sense, and it is an interesting adjunctive power source, but we are not yet ready to run our civilization on solar.

But if the technology news is any indication (and I am not overly blinded by enthusiasm) it seems that we are rapidly getting there. I throw in the usual caveats because predicting the path of future technology is inherently difficult to impossible. But I do think we can guess as some broad brushstrokes (like that solar will be increasingly important) even if we cannot guess the details (will carbon nanotubes be the substrate, or something else?).

Solar power is steadily getting more cost effective. Various companies are making headway in developing cheap solar panels (but ones with modest efficiency: 6-10%), while others are developing techniques to increase the efficiency of solar panels (the percentage of photons that get converted to electricity – commercial panels are currently at 12%). Even modest gains in both areas can make solar competitive with other energy sources.

Also – solar is backing across the line to cost effectiveness as the cost of fossil fuels shoots up. This is like making the playoffs because the other team in the running lost, rather than winning yourself. This is generally considered the one positive side to rising fuel costs – it makes “green” energies like solar more cost effective in comparison.

This brings me to the latest announced breakthrough in solar power technology, announced by MIT. This is not an improvement in solar cell technology but in light-gathering technology. In the 1970’s researchers worked with the idea of adding dye to a sheet of plastic so that the dye would absorb light from the sun then re-radiate the light through the sheet of plastic to the edge. This way solar cells could be arranged around the edge of the sheet facing in and the sheet of plastic would funnel light to these cells.

This technology failed because too much of the light was lost during the trip to the solar cells, so it was abandoned. But now the MIT researchers, led by Marc A. Baldo, have resurrected the idea. The MIT press release explains the breakthrough:

The MIT engineers, experts in optical techniques developed for lasers and organic light-emitting diodes, realized that perhaps those same advances could be applied to solar concentrators. The result? A mixture of dyes in specific ratios, applied only to the surface of the glass, that allows some level of control over light absorption and emission.

This is neat because it is the application of one technology – optics for lasers – being unexpectedly applied to another technology – solar energy. This is the kind of clever development that just cannot be predicted, and why technology is so hard to predict.

Their “solar concentrator” would allow for tall glass buildings to be huge solar collectors. The glass panels will be tinted and semi-transparent, allowing some light through. But most of the light will be funneled to thin strips of solar cells.

This also enables the solar cells (which are expensive) to be much smaller and less exposed. Therefore this may make it cost effective to go with more expensive but higher efficiency solar cells rather than cheaper but inefficient cells.

This one development, assuming it pans out and can be mass produced, is not going to solve our energy problems or make solar ubiquitous. However, it is an interesting development that complements developments in solar cell technology.

Call me an optimist, but I think these kinds of developments will make solar a major contributor to the world’s energy needs over the next 20 years or so. By the end of this century we may even be a solar civilization.