Tuesday, June 24, 2008

Three Ways to Make Solar Cheaper than Coal

source: http://www.ecogeek.org/content/view/1792/83/


Solar power is magnificently exciting. Just lay down a sheet or a panel and every day, for the life of the device, you get free power. There are no fuel costs. No one is ever going to start charging $4 per gallon of sunlight. But, unfortunately, the size of the initial investment keeps the cost of solar generated power higher than the cost of coal.

It's worth noting that, if you take into account the environmental costs of burning coal, solar power is already slightly more economically sound (according to an analysis by the IPCC.) But we're not taxing carbon (yet) so we've got to make solar power cheaper.

There are thousands of people working on that right now. But here are three of the finest examples of companies that are working to bring solar power to grid parity.

Concentrate on the Silicon
The most expensive part of a traditional photovoltaic array is the silicon wafers. It's the same stuff that microchips are made out of, and it's in short supply. The solar industry eats up every ounce of the stuff that's being produced today, and so prices are skyrocketing. To solve this problem (and also the problem of the environmentally wasteful process of creating the silicon crystals) several people, including IBM and a small startup called Sunrgi are concentrating the sunlight thousands of times onto a extremely small solar panel. They decrease the amount of solar material needed by thousands of times, and produce just as much power.

The result is solar power that is nearly as cheap (if not as cheap) as coal and a VERY HOT piece of silicon. Thus the big problem with this technology. You have to keep the silicon cool, even with sunlight magnified 2000x on it. Otherwise the silicon will melt, and it's all over. Both IBM and Sunrgi are using techniques learned from the microprocessor industry to keep their silicon cells cool. Both have working prototypes already and are hoping to go commercial in the coming year.

Beyond Silicon
Another solution to the problem of limited and expensive crystalline silicon is to just not use it. Which is why there are so many solar startups right now working on solar technology using non-crystalline silicon or other thin-film solutions. The real champion of the thin-film startups is Nanosolar, which has already broken out of the lab and into manufacturing.

Nanosolar prints it's mixture of several elements in precise proportions onto a metal film. The production is fast, simple and cheap, at least for now. Some fear that shortages in indium will bring a halt to nanosolar's cheap printing days. But if that fate can be avoided, Nanosolar, and other thin film manufacturers are already pretty far down the path to grid parity. Though they make some efficiency sacrifices when compared to crystalline silicon, they are so much cheaper to produce that they might soon even beat coal in cost per watt.

The Case for Extreme Heat
While the first two options provide the most efficient path to solar electricity, but converting photons directly into electrons, a less efficient, though simpler, option might turn out to be the real coal-killer.

Simply by focusing hundreds or even thousands of mirrors onto a single point, several startups are hoping to create the kind of heat necessary to run a coal fired power plant...but without the coal. The heat would boil water which would then be used to turn turbines. The advantage of such a system is that there are already lots of steam turbines being produced for traditional power plants, and the rest of the technology just involves shiny objects and concrete.

One problem does present itself, however, when you start to try and make these things too hot. The material holding the boiler has to be able to withstand the extreme heat that these installations can produce. That kind of material, that won't melt or degrade under such extreme heat, can be quite expensive.

Nonetheless, Google-funded startup, eSolar, is saying that by modularizing the construction of these "concentrating solar thermal" power plants, they could be cheaper than coal today.

If Not Today...Then Tomorrow
As coal and gas have remained extremely cheap over the last fifty years, there's been very little pressure to innovate and move beyond that technology. But now, with natural gas prices increasing along with concerns about global warming, we're finally ready to innovate. And expansions in materials and nanotechnology are making the change even more interesting.

It's no longer a question in my mind of if we can get solar cheaper than coal, it's simply when, and whether another renewable energy, like geothermal or wind, will beat solar to the punch.

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