solar flow battery tagged posts

How the solar flow battery works. Image: Li et al./Chem

Scientists in the United States and Saudi Arabia have harnessed the abilities of both a solar cell and a battery in one device – a “solar flow battery” that soaks up sunlight and efficiently stores it as chemical energy for later on-demand use. Their research, published September 27 in the journal Chem, could make electricity more accessible in remote regions of the world.

While sunlight has increasingly gained appeal as a clean and abundant energy source, it has one obvious limitation – there is only so much sunlight per day, and some days are a lot sunnier than others. In order to keep solar energy practical, this means that after sunlight is converted to electrical energy, it must be stored...

Schematic of a “solar flow battery” with the three-electrode configuration: lithium anode electrode, counter electrode (CE), and photo-electrode (PE). Current passes through a liquid in the battery called an electrolyte. The portion of the electrolyte near the cathode electrode is called a “catholyte.” The CE and PE electrodes are in contact with the “catholyte.” Credit: Image courtesy of Yiying Wu, The Ohio State University

More efficient, eco-friendly electricity generation with a “solar flow battery” combines a redox flow battery and a dye-sensitized solar cell, using compatible, water-based (aqueous) solvents. Solar energy is harvested and stored as chemical energy during the charging process. When it is time to recharge the battery, the amount of energy needed to is lower than conventional lithium-iodine batteries because dye molecules, exposed to the sun, donate electrons to the recharging process.

Energy generation from a solar flow battery is more cost-effective, eco-friendly, and can achieve energy savings up to 20% compared to conventional lithium-iodine batteries. Solar flow batteries make renewable solar energy more practical for keeping the lights on and appliances running with stand-alone electricity generation and storage.

Last year, researchers at The Ohio State University demonstrated photo-assisted charging of a lithium-oxygen (Li-O2) battery; however, they used organic (carbon-based) solvents that limited its compatibility with aqueous redox flow batteries. Now, these researchers have built a solar flow battery that uses an eco-friendly, compatible solvent and requires a lower applied voltage to recharge the battery. In solar flow batteries, the proposed charging process links harvesting solar energy and storing it as chemical energy via the electrolyte.

The aqueous electrolyte is in contact with the counter electrode of the battery and the dye-sensitized photo-electrode of the solar cell. To recharge the battery, it is exposed to sunlight. The sunlight causes the dye molecules in the electrolyte to donate electrons to the photo-electrode, reducing the amount of energy needed to recharge the battery. The applied voltage to recharge the solar flow battery is reduced to 2.9 Volts compared to > 3.6 Volts for conventional lithium-iodine batteries, resulting in an energy savings of up to 20%.

The aqueous solar flow battery performs better and is more cost-effective and eco-friendly than those based on organic solvents. The aqueous solar flow battery could solve the intermittency shortcomings of renewable energy and keep the lights on and appliances running. http://science.energy.gov/bes/highlights/2015/bes-2015-10-f/