Energy storage has led to the growth of concentrated solar power.
Solar power is growing rapidly around the world, with installed solar capacity today almost 10 times that of a decade ago. Behind the boom are solar photovoltaic (PV) panels, which use semiconductors to convert sunlight into electricity. But even as smooth rectangles become cheaper and more ubiquitous, photovoltaic solar panels alone won't solve a perennial question: What happens when the sun doesn't shine? As utilities and policy makers look for solutions to store and deploy power on demand, centralized solar thermal power (CSP) is gaining renewed attention.
Solar-thermal systems use sun-tracking mirrors to reflect sunlight onto a receiver containing a high-temperature liquid that stores heat. The heat can drive steam turbines or engines to produce electricity 24/7. Solar thermal can also directly heat industrial processes that are difficult to clean up in energy-intensive industries such as steel, cement production and chemical manufacturing. Some U.S. states and countries are taking steps to curb greenhouse gas emissions, and now "may be the time to make solar thermal power more widely available." Margaret Gordon, project manager for solar thermal power at Sandia National Laboratories in Albuquerque, N.M.
The first utility-scale solar thermal plant was built in the 1980s. Today, nearly 120 projects are operating worldwide, with Spain claiming more than a third of the total installed capacity. But in recent years, as the cost of photovoltaic solar panels has fallen rapidly, the development of solar-thermal power generation has stalled. Large-scale solar thermal arrays require prohibitive upfront investment. Unlike photovoltaic solar panels, helioscopes, heat exchangers and other key components are not "off the shelf," adding time and expense to project development, Gordon said. Even so, the growing demand for energy storage and cleaner heat sources is driving continued solar thermal development in sunny regions of the world. Technology Overview looks at four new solar thermal projects, each representing different solar thermal power technologies that are harnessing the sun's heat to control emissions.