Global solar energy supplies are growing rapidly, with nearly 10 times as much solar capacity installed today as there was a decade ago. Leading the boom is the photovoltaic (PV) panel, which converts sunlight into electricity using semiconductors. But even as the glossy rectangles become increasingly cheaper and ubiquitous, solar PV alone can’t solve the nagging question: What to do when the sun isn’t shining? As electric utilities and policymakers seek solutions for storing and dispatching energy on demand, concentrating solar-thermal power (CSP) is once again gaining traction.
Solar-thermal systems use sun-tracking mirrors to reflect sunlight onto a receiver, which contains a high-temperature fluid that stores heat. The heat can drive steam turbines or engines to generate electricity around the clock. Or, solar thermal can directly provide heat for industrial processes to make steel, cement, and chemicals—all energy-intensive sectors that are difficult to clean up. With U.S. states and countries adopting measures to curb greenhouse gas emissions, now “might be the right time for CSP to become more broadly applicable,” said Margaret Gordon, the CSP program manager at Sandia National Laboratories in Albuquerque, N.M.
The first utility-scale solar-thermal plants were built in the 1980s. Today, nearly 120 projects operate worldwide, and Spain claims more than a third of total installed capacity. In recent years, however, CSP development stalled amid the rapidly falling cost of solar PV. Massive solar-thermal arrays require steep upfront investment. Unlike solar PV, the mirrors, heat exchangers, and other key components aren’t yet “off-the-shelf” ready, which adds time and expense to project development, Gordon said. Even so, solar-thermal developments continue to unfurl across the planet’s sunniest expanses, driven by the growing demand for energy storage and cleaner heat sources. IEEE Spectrum looked at four new solar-thermal projects—each representing a different CSP technology—that are curbing emissions by harnessing the sun’s heat.
Source: soectrum
