It seems so simple: mirrors collect and concentrate the sun's rays to heat water. The resulting steam is then used to power turbines. The technology is uncomplicated. The difficulties such as those inherent in nuclear energy and CO2 sequestration don't exist, and it has been used for decades. The first solar thermal plant was built in the 1980s in California. But when oil prices fell once again, solar thermal energy slipped into the background. Now with climate change on everyone's agenda, it is experiencing a renaissance.
The jewel of that renaissance is the Desertec project, a concept developed by a group of scientists that envisions gigantic power plants in the Sahara Desert that could, in theory, provide enough electricity for the entire world. High tension lines are to transport the power across the Mediterranean to Europe.
Solar thermal power plants for the production of electricity make little sense in Central Europe, where there is simply not enough sun. Large facilities would, however, make sense in regions such as southern Spain, North Africa or the Middle East.
Despite having been around for decades, the technology, with an energy-conversion efficiency rating of 15 to 20 percent, is not yet as efficient as coal or nuclear. A kilowatt hour of solar thermal electricity costs between 14 and 18 cents. But improvement is in sight, with experts predicting that technological improvements will sink the cost to below 10 cents per kilowatt hour by 2020.
When it comes to heating, however, the situation looks different. Solar collectors like those used in solar thermal plants can be used to heat water which can in turn easily be used to heat homes. Still, solar energy remains something of a niche product on the German heating market, while oil and natural gas remain dominant.
But solar thermal plays a subservient role even within the renewable energy sector of the German heating market. In 2008, it was responsible for 4,131 gigawatt hours of heating energy whereas biomass -- primarily in the form of wood pellets -- accounted for 97,108 gigawatt hours.
When it comes to heating homes, solar thermal facilities remain too expensive to make much headway. Should costs ever drop far enough to make them affordable without state subsidies, demand will surely rise.
But even then, solar thermal can never completely replace more conventional heating systems -- after all, one would like to have hot water at night as well. Experts envision a home heating model that uses wood pellet heating for day-to-day needs, augmented by solar thermal to cut costs.
Large solar thermal power plants in sunny countries, on the other hand, have huge potential. Should Desertec in the Sahara Desert ever become reality, for example, then huge quantities of power could be generated by solar thermal technology. And for the moment, it looks like progress is being made. In October, a number of industrial and financial heavyweights joined forces to create the Desertec Industrial Initiative. The goal: by 2050, the project hopes to supply 15 percent of Europe's energy needs. The costs, however, are high. The power plant itself will cost some 350 billion with an additional 50 required for a new and efficient grid.
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