As more and more people install solar panels, the need to store solar power is growing. Batteries that store sun-generated electricity are key for houses to have power at night or when it’s cloudy. But today’s battery technologies are riddled with issues such as high cost, toxicity, and short life. Researchers at Harvard University have developed a new kind of low-cost battery that can run for more than 10 years with no maintenance. It is also non-toxic and inexpensive, to boot. The technology could make grid-scale renewable energy storage a reality, the researchers say in a paper published in the journal ACS Energy Letters
. Solar power customers today have two common options for storing solar power. Lithium-ion batteries such as the ones found in electronics and EVs are still very expensive. Lead-acid batteries cost half as much, but require a lot of maintenance and contain toxic materials
. Another emerging storage technology is what’s called a flow battery. Instead of the solid electrodes found in conventional batteries, flow batteries contain liquid electrolytes held in separate tanks that react as they flow through cells. Today’s flow batteries use electrolyte solutions of vanadium metal dissolved in corrosive acids. Not only is vanadium expensive, but this formulation also adds cost because it requires special corrosion-resisting tanks. Plus, all of today’s battery technologies start losing their capacity to hold charge after a few years, or a few hundred recharge cycles. Roy G. Gordon, Michael J. Aziz, and their colleagues came up with a fresh take on flow batteries. They developed new chemical compositions for non-toxic organic and metallic compounds for the positive and negative electrolytes. The compounds are made from elements that are abundant in the earth, such as iron. The researchers dissolved these compounds in pH-neutral water to make the electrolytes. This was not possible with similar compounds developed in the past: those either broke down in neutral water or simply didn’t dissolve. The new battery should be cheaper to produce than today’s devices. “And since the medium is noncorrosive, you can use cheaper materials to build the components of the batteries, like the tanks and pumps,” Gordon said in a press release
. The battery loses only 1 percent of its capacity after over 1,000 charge cycles, which is much longer than lithium batteries. The researchers also calculated that if the battery was charged and discharged completely once a day, “we would expect it to retain 50 percent of its energy storage capacity after 5,000 cycles, or about 14 years.”
Source: Beh ES et al. A Neutral pH Aqueous Organic/Organometallic Redox Flow Battery with Extremely High Capacity Retention. ACS Energy Letters. 2017.
Photo: Organic mega-flow battery in the Harvard SEAS lab. (Photo by Eliza Grinnell, Harvard School of Engineering and Applied Sciences)