The Quest for Solar Batteries, the Holy Grail of Clean Energy
The sun beams down enough energy to supply all the electricity the Earth needs, but for all our advances with renewable energy, one of the most frustrating barriers to a zero-emissions world is the lack of a great solar battery.
Solar panels are hailed as an easy, affordable step toward reducing cities’ reliance on fossil fuels for electricity, but at the moment most solar panels can only produce electricity on-demand. They can store energy, but not for long enough to keep the lights on during cloudy days and long winter nights, said Nate Lewis, head of a solar fuels initiative at the California Institute of Technology.
Even though scientists and engineers are building cheaper and more efficient solar panels, one major bottleneck is the ability to store that energy for times when the sun is not shining, said University of Wisconsin, Madison, professor Song Jin, whose team is trying to develop a better battery.
Lewis said the best battery developed so far stores 200 watt hours per liter, roughly enough energy to power a water heater for maybe two weeks, whereas one liter of gasoline has about 12,000 watt hours (enough to power that same water heater for two-and-a-half years). In terms of potential, it’s like comparing a tricycle to a motorcycle—you’re not even in the same ballpark.
“In fact, the limit for many forms of renewable energy that are intermittent (solar, wind, etc.) is that the electrical grid will become unstable,” if cities rely on them too much, Song told Motherboard. So making this technology more powerful is as important as getting solar panels into more areas.
But to reduce the current greenhouse gas emissions that are causing climate change, researcher are looking to close this energy storage gap. Some labs are using sunlight to separate water into oxygen and hydrogen, in the hopes of burning the hydrogen as a clean energy source. Other labs are using reverse photosynthesis, where specially designed chlorophyll reacts with sunlight to create biofuels.
Lithium-ion batteries are the most common batteries used for most purposes (think the batteries in your flashlights and TV remotes), but researchers are working on different batteries for solar storage, Lewis said.
Redox flow batteries are the more common choice for solar panel electricity storage, he said/ They work by flowing reactants from two holding tanks into a central area where it reacts, and then the resulting products from the reaction is deposited into different containers. It’s “a twist” on regular batteries because the whole thing is fairly large and the products and reactants aren’t all stored in the same way as a lithium-ion battery.
Jin’s team is working on making a better redox flow battery by using liquid electrolytes, which he said are able to store more energy. He essentially combined a solar cell with a large-capacity battery that transfers energy directly to the battery, rather than having to create electricity first before storing it in the battery in the form of energy.