Hybrid Solar Power Works Even When It’s Not Sunny
Combining the strengths of two different solar technologies could yield “hybrid solar power” that works even at night or when it’s cloudy.
The Advanced Research Projects Agency–Energy is devoting $30 million to several demonstration projects that will attempt to combine photovoltaics with solar thermal. Early-stage work being conducted by researchers around the U.S. hints at how the combined technology might work.
The effort seeks to solve an important problem. ARPA-E estimates that the intermittency of solar electricity could limit it to providing just 5 percent of total energy in the United States. “You end up having so much solar at times that you can’t use it, that you end up having to dump it,” says Cheryl Martin, ARPA-E’s deputy director.
Currently, storing electricity from solar panels is either prohibitively expensive or, in some areas, unfeasible. Solar thermal power, which concentrates sunlight to heat water and make steam for turbines, can store energy by keeping heat in insulated containers. But overall, solar thermal power is twice as expensive as power from solar panels.
According to ARPA-E, there are several ways the two types of solar power might be combined.
Some solar power systems involve concentrating sunlight on tiny, super-efficient solar cells. As they’re currently configured, the heat from the concentrated sunlight is quickly extracted and allowed to dissipate into the atmosphere. If it could be collected instead, it could be stored and used to generate electricity later. The challenge is that this approach would require operating solar cells at much higher temperatures than is normal, and this can damage them. Researchers are looking at ways to make solar cells more resistant to high temperatures.
Another possibility is to split up the solar spectrum. Solar cells are very good at converting certain wavelengths of light into electricity—but not others. It may be possible to redirect wavelengths that can’t be used efficiently, and to use these to heat up water and produce steam.
Yet another approach is being developed by Todd Otanicar, a professor of mechanical engineering at the University of Tulsa. He uses nanoparticles suspended in a translucent fluid to absorb certain wavelengths but allow others to pass through to a solar cell. As the nanoparticles absorb sunlight, they heat up, and the fluid can be used to generate steam.
The idea of using both heat and electricity from solar panels isn’t new. Some companies run tubes along the back of conventional solar panels and then pump water through the tubes. The waste heat from the solar panel heats up the water, replacing water heaters. But these systems do not work very efficiently.
ARPA-E is also considering funding novel energy storage technologies that use both heat and electricity. Adding heat to electrolysis, for example, might improve the economics of splitting water to produce hydrogen. The hydrogen could then be run through a fuel cell to generate electricity. Heat could also aid other electrochemical reactions, such as those that can be used to make liquid fuels for vehicles.
The inside story of how ChatGPT was built from the people who made it
Exclusive conversations that take us behind the scenes of a cultural phenomenon.
Sam Altman invested $180 million into a company trying to delay death
Can anti-aging breakthroughs add 10 healthy years to the human life span? The CEO of OpenAI is paying to find out.
ChatGPT is about to revolutionize the economy. We need to decide what that looks like.
New large language models will transform many jobs. Whether they will lead to widespread prosperity or not is up to us.
GPT-4 is bigger and better than ChatGPT—but OpenAI won’t say why
We got a first look at the much-anticipated big new language model from OpenAI. But this time how it works is even more deeply under wraps.
Get the latest updates from
MIT Technology Review
Discover special offers, top stories, upcoming events, and more.