Solar thermal power

I have a feeling that this article about eSolar (a solar thermal energy start-up) is important.

We looked at all of the renewable technologies that can be deployed at scale, and they were all variations of solar thermal.

Solar thermal power plants consist of a central tower surrounded by mirrors. The mirrors are arranged to reflect sunlight towards the top of the tower, where the sunlight heats water. The boiling water in the tower drives a steam turbine, which generates electricity. In a sense, this approach is just like nuclear fission power plants — nuclear energy (in this case, from fusion in the sun) boils water, which drives a turbine.

The advantage of solar thermal over photovoltaics (“solar panels”) is that the components are much easier to manufacture. The parts are commodities: mirrors, water, and decades-old turbine technology. By contrast, solar panels are relatively expensive, high-tech components.

On the other hand, since the sun moves across the sky during the course of a day, the angles of solar thermal mirrors have to be constantly, precisely adjusted via motors so that the reflected sunlight continues to hit the tower. Solar panels are significantly cheaper to install because they don’t need motors or precise alignment.

eSolar has lowered installation costs by using sensors and software to automatically aim the mirrors at the tower (rather than precisely surveying the position of each individual mirror).

When we place the mirrors, they’re not surveyed at all: we open our shipping container, we unfold our stuff, and we place it in the ground. The guys can be drunk when they place the rows; it really doesn’t matter. Our tolerance is plus or minus a foot.

That’s a nice visual: drunken men scattering reflectors helter-skelter across the desert. It remains to be seen whether eSolar can actually keep costs as low as they claim. But I had not realized that solar thermal was such a strong competitor to solar panels. Solar panels will continue to be the most practical in rooftop installations and the like. But when it comes to producing renewable energy at scale, those mirrors and motors are starting to sound like a good bet.

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