PV Gap

Ian Said:

Good things about SOLAR POWER?

We Answered:

Doesn't require fuel to keep running. Requires fuel to make; but it pays it back many times over. Its CO2 emissions over the life cycle are also low (look up any life cycle analysis)


Efficiencies are improving:
http://upload.wikimedia.org/wikipedia/co…

The theoretical limit for a single junction cell is about 31% on Earth. But with multi junction cells you can get higher.



Prices are falling:
My research group works with Cadmium Telluride, or CdTe. If you look at the efficiencies graph above, you'll see it's not the most efficient: silicon and CIGS are better. However, CdTe is much cheaper*. In 1998 it cost $10.80 for a Wp of solar power, which fell to $7.50 by 2007:
http://newenergynews.blogspot.com/2009/1…

FirstSolar are using CdTe cells and built power stations in Germany at $4.50/Wp. They've got stations in planning for about $3-3.50/Wp in China and the US. This is an economic price in very sunny areas!:
http://en.wikipedia.org/wiki/Photovoltai…




*CdTe is a much better light absorber than silicon (because it's a 'direct band gap semiconductor', if you want to put that in and sound clever! :p ), so you need much less of it to absorb the light. Our cells are about 5micro-metres thick. Silicon has to be at least 20 times that to absorb the same amount of light. This means you need more silicon; which costs more!



EDIT: jessica's post is written a little confusingly! Solar cells produce DC electricity. To use it in a normal home, you have to put it through an inverter that turns it into AC power. You can either invert it and use it straight away, invert it and sell it to the grid, or dump it in a battery. A battery is DC, so after it comes out of the battery, you need to use the inverter on it.

Crystal Said:

What are some good things about nuclear energy?

We Answered:

Fossil fuels always release more pollutants, including CO2 if you consider that a pollutant. Hydroelectric electricity has limited availability, and it's a resource that is pretty much tapped out - every river which can be dammed for electricity already is. Solar energy is expensive, far more expensive than anything else. There is a lot of variation is solar panels, but it often involves rare earth elements, which limits the total numbers of panels which could be produced (at a number too low to matter). Solar energy is also not very energy dense. The total land it would take to capture the same amount of energy using solar as can be generated using nuclear is tremendous. States worth of land. Unlike oil, we have a lot of uranium locally, and the other nation with big resources is Australia who we're on pretty good terms with. And if we had some modern reactors, there would be much less nuclear waste produced. In fact, some of the new plants can eat material which was previously considered waste.