Scientists at the University of Wisconsin-Madison, led by chemistry Professor Song Jin, have developed a single device that uses solar energy to charge a battery without the intermediate step of producing electricity and then using that electricity to charge the battery.

In the new device, standard silicon solar cells are mounted on the reaction chamber of a redox flow battery. The energy captured by the cell charges a water-based electrolyte, which is pumped out to a storage tank. The size of the storage tank  can be varied to match the amount of energy produced by the solar cells making them suitable for large-scale grid applications.

Currently, storing energy captured by solar cells requires converting the solar energy to electrical energy and then converting the electrical energy to chemical energy. The unified design in which solar cells directly charge an electrolyte, makes for simplicity, cost reduction and potentially higher efficiency.

The current study uses an aqueous electrolyte containing organic molecules, further reducing the cost compared to other batteries which use expensive rare metals.

The researchers are now working on matching the solar cell’s voltage to the chemistry of the electrolyte, minimizing losses as energy is converted and stored.