This Solar-Charged Battery Directly Converts Sun’s Energy and Stores It in Liquid Electrolyte

A team of researchers at the University of Wisconsin-Madison have made a device that transfers solar energy straight to the battery’s electrolyte, without the need to make electricity in between. Song Jin, who is a professor at the University, collaborated with graduate student Wenjie Li and colleagues at the King Abdullah University of Science and Technology in Saudi Arabia to show the world just how this could be done.

A Redox flow battery (RFB) was chosen to store energy in a tank of liquid electrolyte. The RFB stores chemical energy in the liquid electrolyte rather than in solid electrodes like lithium-ion batteries. To discharge the RFB battery and use it to power the grid at night, Jin says, “We just connect a load to a different set of electrodes, pass the charged electrolyte through the device, and the electricity flows out.” This type of solar charging and electrical discharging can be used several times with very good efficiency levels.

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. PHOTO: David Tenenbaum, University Communications/UW-Madison
This solar-charged device, developed in the lab of Song Jin at the University of Wisconsin-Madison, 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. PHOTO: David Tenenbaum, University Communications/UW-Madison

Although Redox flow batteries are already being attached to solar cells and used within the market, they are not being used in quite the same way. Li, the first author of the study, says, “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. We are using a single device to convert solar energy and charge a battery.” Its design also provides many advantages such as the ability to directly charge the electrolyte, reducing costs and improving efficiency.

Now that the team has produced one successful design they are looking to see how they can improve on it further which will include searching for electrolytes with larger voltage differential which is one of the limiting factors in this type of technology. As Jin says, “It’s not just about the efficiency of converting sunlight into electricity, but also how much energy you can efficiently store in the device.”

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