Photovoltaic panels that directly convert sunlight to electricity are what most people think of when they hear the term "solar power," but there is another way.
It's known as solar thermal or concentrated solar power (CSP), and has been around since the 1980s. These systems rely on mirrors known as heliostats to bounce sunlight to a central gathering point. There, the concentrated beams heat a transfer fluid that in turn heats a working fluid. This fluid then evaporates, turns a turbine, and generates electricity.
In 2014, what was then the world's largest solar thermal power station opened in the Mojave Desert in the United States. Today, the world's largest operates in the Sahara Desert in Morocco. But now, China is getting in on the act, and has a new facility that is 90 percent complete.
Two 650-foot-tall (200m) towers have risen in China's Gansu Province. Combined with an array of 30,000 mirrors arranged in concentric circles. According to a report from China Global Television Network, China is implementing a new form of CSP. Much like the facility in the US, the Chinese solar thermal energy storage project will use multiple towers: in this case, two of them, both sharing the same steam turbine.
But unlike the US facility, where each tower is surrounded by its own field of heliostats, the Chinese project will deploy a field of mirrors set in overlapping concentric circles. The mirrors will then be able to follow the path of the Sun and reflect light to either tower in the most efficient way possible.
"The mirrors in the overlapping area can be utilized by either tower," says project manager, Wen Jianghong. "This configuration is expected to enhance efficiency by 24 percent." Helping that efficiency along is the fact that the mirrors being used have a 94 percent reflection efficiency, meaning that most of the solar energy that hits them is beamed back to the power-producing towers.
The two towers at the new plant will employ a molten salt method to store heat during the day and release it at night to keep the facility churning out power. The new facility is expected to come online later this year and churn out a whopping 1.8 billion kilowatt-hours of electricity every year.