Solar Power

Solar power is a great idea, but not everyone can install a solar system on their home or property. But more and more companies-utility companies in particular-are seeing the benefits of using renewable energy sources. Some of them are building solar power plants.

Two southern California utilities have combined forces and plan to build two solar power plants in the southern California desert. One will generate 300 megawatts of clean, renewable electricity, the other 500 megawatts. This will be the largest solar power project in the world so far.

It will generate electricity and jobs, but no air or water pollution. This project, like many other current solar projects, uses curved mirrors or dishes that focus the sun's energy on an engine that contains hydrogen. The hydrogen expands as it heats, powering the engine's pistons, which then generate electricity.

Using the curved dishes results in greater efficiency-an estimated 30% in the California example. Simply increasing the efficiency of the power-generating solar setups will result in cheaper power, since the initial investment will produce more power than less-efficient construction.

Another advantage of solar power plants is that some of the best sites for solar power generation are remote, hot, and sparsely populated. The California desert is one example, but other plants have been built on landfills, on top of large industrial complex roofs, and outside former Olympic villages. In fact, a solar plant is currently under construction outside of Seville, Spain, that will power the entire city once it's fully operational around the year 2013.

Yet if you don't limit your thinking of a "plant" to a huge industrial complex, any building with solar cells on it could be considered a solar power plant. You are, after all, generating most or all of the power needed for your own needs.

Solar power plants have typically used large quantities of flat-plate photovoltaic panels, but more and more the curved collectors, aimed at fluid-filled heat-transfer device. Photovoltaic plants operate much less efficiently during cloudy weather, and of course stop operating during the night.

Any excess energy is usually stored in batteries, so your energy use during the night is only as much as the battery can store. If you've been subject to several cloudy days, that could be a very short time.

But using the sun to heat a transfer medium (oil, hydrogen, salt) means that the heat can be used or stored, and pulled off during the night. Solar trough designs and solar tower designs both have higher efficiencies than photovoltaic systems, and are the current methods of choice for most plants under construction.

The space required for these plants is also shrinking as the new designs come out and the efficiencies rise. It may not be too far in the future before we see small solar "plants" replacing substations throughout America.