Liquid battery to solve solar efficiency issues

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This solar-charged battery, developed in the lab of Song Jin at the University of Wisconsin–Madison, directly stores energy from sunlight in a tank. Image: David Tenenbaum

A chemistry professor from the University of Wisconsin-Madison has invented a battery to address night-time solar efficiency issues.

Currently, one of the main limitations of solar power is the fact that it is unreliable as a power source. To address this, companies are beginning to invest in lithium-ion battery storage. Taking a different stance, Professor Song Jin and his colleagues decided to integrate the solar cell itself with a large-capacity battery. According to Jin, this eliminates the step of making electricity and instead transfers the energy directly to the battery’s electrolyte.

Jin chose a “redox flow battery”, or RFB, which stores energy in a tank of liquid electrolyte.

This makes it simple to discharge the battery to power the electric grid at night, according to Jin.

“We just connect a load to a different set of electrodes, pass the charged electrolyte through the device, and the electricity flows out.”

Solar charging and electrical discharging can be repeated for many cycles with little efficiency loss, he added.

Unlike lithium-ion batteries, which store energy in solid electrodes, the RFB stores chemical energy in liquid electrolyte.

“The RFB is relatively cheap and you can build a device with as much storage as you need, which is why it is the most promising approach for grid-level electricity storage,” said Jin.

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This solar-charged device directly transfers energy from sunlight into a liquid battery and stores it in the container at lower right. During the discharge cycle, electricity leaves the device through electrodes at top. Image: David Tenenbaum

In Jin’s device, standard silicon solar cells are mounted on the reaction chamber and energy converted by the cell immediately charges the water-based electrolyte, which is pumped out to a storage tank.

While there are already RFBs on the market that have been attached to solar cells, “now we have one device that harvests sunlight to liberate electrical charges and directly changes the oxidation-reduction state of the electrolyte on the surface of the cells,” said Wenjie Li, lead author of the study.

“The solar cells directly charge the electrolyte, so we’re doing two things at once, which makes for simplicity, cost reduction and potentially higher efficiency,” said Jin.

 

Source: University of Wisconsin-Madison