US energy department to invest $62m in concentrated solar
The US Department of Energy will invest $62m in concentrated solar power, a technically challenging and more expensive form of renewable energy compared with photovoltaics, but which is capable of storing as well as generating energy. Concentrated solar uses mirrors to focus sunlight, converting liquid into steam to drive turbines, with excess energy stored in molten-salt tanks. While some experts have questioned the Trump administration's move, which appears to diminish support for photovoltaics, others have praised the decision to back an underdeveloped technology.
Concentrated solar is at the top of the reshuffled list of research priorities, suggesting DOE officials think the technology can do more to improve grid stability over the long term. That’s because, while the energy it produces has been far more expensive than photovoltaics, it can store some of it in the form of heat. That means it can continue to generate electricity even when the sun isn’t shining, helping to balance supply-and-demand loads on the grid.

Given past behavior, the announcement raises at least some suspicions that the department, under Energy Secretary Rick Perry, may be seeking additional ways to diminish support for photovoltaics, potentially slowing progress behind the solar technology that’s done the most so far to threaten fossil fuels. After all, it follows the Trump Administration’s 2018 budget proposal to cut funding for the Office of Energy Efficiency and Renewable Energy, which oversees the SunShot program, by nearly 70 percent. (So far, Congress has pushed back on most of the proposed cuts to DOE research programs.)

But with that all said, energy researchers are quick to stress that the storage issue is a very real problem for photovoltaics—and a very real advantage for concentrated solar.

“[Concentrated solar power] today hasn’t been able to compete with photovoltaics, but there are some promising research areas,” says Dan Reicher, executive director of the Steyer-Taylor Center for Energy Policy and Finance at Stanford. “Given the climate challenge, we need to put eggs in many, many zero-carbon baskets.”

Concentrated solar generally relies on mirrors to concentrate sunlight, which converts liquid into turbine-driving steam. Some of that heat can also be stored using molten-salt tanks, allowing the plants to continue supplying electricity when the sun isn’t shining.

In contrast, photovoltaic power plants only work when the sun is out, unless they’re coupled with expensive batteries or other forms of external storage. The same goes for wind.

The downside to concentrated solar, however, is that it’s proven to be more expensive and technically challenging. Notably, the $2.2 billion Ivanpah plant in California’s Mojave Desert has struggled to meet production goals and produce electricity at competitive prices. The facility has been relying on increasing amounts of natural gas, the local Press-Enterprise newspaper reported earlier this year.

But there are some promising research avenues that could improve efficiency and costs. In 2015, the DOE’s moonshot ARPA-E division provided $24 million in funding to 11 projects focused on essentially combining the two approaches into what’s known as “concentrated photovoltaic technologies,” using lenses and mirrors to concentrate sunlight onto small photovoltaic cells (see “DOE Attempts to Jump-Start Concentrated Solar”).