The Economist magazine wrote that BrightSource Energy recently signed the world’s two largest deals for solar power. BrightSource Energy will use “concentrating solar-thermal technology,” which involves using mirrors to concentrate sunlight to produce heat. The heat created by the mirrors, which is collected in either troughs or towers, is then used to generate steam, which drives a turbine. Construction will begin shortly on the first in a series of “14 solar-power plants that will collectively supply more than 2.6 gigawatts (GW) of electricity—enough to serve about 1.8m homes.”
According to the Economist, about 12 gigawatts (GW) of solar-thermal power is in development worldwide. This is an enormous jump in production, considering only 500 megawatts (MW) of such capacity has been built to date. Sun-baked areas like the U.S. Southwest are aiming to become leaders in solar energy production in the U.S.. In Europe, Spain is investing in solar power. “To maximise the energy that can be collected from the sun, solar-power facilities are being constructed in regions that enjoy daily uninterrupted sunshine for much of the year.” Theoretically, solar power plants based in the U.S. Southwest could provide enough power to run the U.S.. “According to Mark Mehos of America’s National Renewable Energy Laboratory, solar-thermal power could in theory generate 11,000GW in America’s south-west. That is about ten times America’s entire existing power-generation capacity.”
Solar-thermal technology may be better than solar-photovaltaics (otherwise known as solar panels): “They are typically built on a much larger scale, and historically their costs have been much lower. Compared with other renewable sources of energy, they are probably best able to match a utility’s electrical load, says Nathaniel Bullard of New Energy Finance, a research firm. They work best when it is hottest and demand is greatest. And the heat they generate can be stored, so the output of a solar-thermal plant does not fluctuate as wildly as that of a photovoltaic system. Moreover, since they use a turbine to generate electricity from heat, most solar-thermal plants can be easily and inexpensively supplemented with natural-gas boilers, enabling them to perform as reliably as a fossil-fuel power plant.”
Photovaltaics were in the lead as solar producers of energy for the past decade, but once the tax incentives in place for solar-thermal energy disappeared in the early 1990’s production fell. As a result, photovaltaics, which do not require the massive investment needed for large-scale solar-thermal plants, gained in usage. By 2007, worldwide installed capacity of solar photovaltaics reached 9.2GW, even though solar panels are more expensive than solar-thermal on a per-KW hour basis. A few other reasons for solar panels’ success: solar photovaltaics are easy to apply in small-scale, modular form (roofs, yards), and can also generate power off the grid.
Solar-thermal may be making a come-back, largely because they are viewed as more cost-effective for large-scale installations. According to MIT Technology Review, a study conducted by the University of California’s Energy Institute in 2008 argues that solar thermal power will “become cost competitive with other forms of power generation decades before photovoltaics will, even if greenhouse-gas emissions are not taxed aggressively.” Additionally, solar-thermal may more easily integrate with other types of power systems such as natural gas or coal plants, creating hybrid systems. The Economist argues: “because solar-thermal plants have a power block and turbine already in place, the extra cost is marginal. Hybridisation could also be done the other way around, by using steam generated from solar-thermal collectors to help drive the turbines at existing coal or gas plants.” Furthermore, MIT Technology Review notes that solar-thermal could be specifically used to cut the carbon footprint of existing coal power plants: “feeding heat from the sun into coal-fired power stations could turn out to be the cheapest way to simultaneously expand the use of solar energy and trim coal plants’ oversize carbon footprints.”
A few challenges remain for large-scale solar-thermal plants. Solar-thermal plants planned for the U.S. Southwest are often far off the grid, so extra infrastructure in the form of transmission lines is required to tap these energy sources. MIT Technology Review notes storing power for use in bad weather is also critical to making the plants cost-effective. The current business climate means less available funds for investing in renewable energy — many projects have been put on hold. Additionally, while solar-thermal plants produce no C02 emissions, they suck up vast amounts of water, creating problems for communities in the Southwest and elsewhere already dealing with water limits. “Both power-tower and trough-based systems are typically water-cooled, and require millions of gallons of water annually. That can cause big problems, especially in desert environments.”