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August 14, 2015 | UCLA Chemists Develop Material for Solar Cells That Could Store Energy for Weeks

One of the persistent problems in the development of solar energy is how to store the electricity once it is created from a photovoltaic cell. By its very nature, solar energy only works when the sun is up, and works best when the sky is not cloudy. To be practical, solar energy systems have to have a way to store excess electricity when the sun isn’t shining. According to a recent piece in SciTechDaily, some chemists at UCLA have created a new material that could allow solar cells to store excess electricity and release it at will.

Storing Solar Energy in Batteries

Currently, most solar energy storage solutions involve the use of batteries. During the day, the electricity that is not used by the home or small building with the rooftop solar array is stored in a large battery. At night or when the sky is cloudy, the excess electricity is released from the battery to keep the lights on.

Batteries Not Included

Greentech Media reported that three other energy storage technologies exist that do not require batteries, but at this point they’re only used on a utility scale rather than for residential or small business installations.

The first method uses the excess electricity from a solar energy system to crack hydrogen from water. The hydrogen can be used for a variety of energy needs, but for storage purposes it is used as fuel for fuel cells, which can then provide electricity when the sun isn’t shining.

The second method stores the excess energy in the form of compressed air. During the day, solar energy is used to pump air into a storage container. When the sun isn’t available, the air is released, turning a turbine to generate electricity.

A third method pumps water into an elevated reservoir. At night or when the sky is overcast, the stored water is released into a lower reservoir, turning a turbine along the way in the same manner as a hydroelectric dam.

Storing Solar Energy by Mimicking Photosynthesis

This leads us to a new method of storing solar energy, thanks to some chemists at UCLA, who are creating photovoltaic cells that act much like the leaves of plants. Plants absorb solar energy by separating positive and negative charges in nanostructures inside the leaves’ cells and then slowly releasing the stored energy to the plant in the form of chemical energy.

Photovoltaic cells made of silicon only retain the solar energy for fractions of a second before transforming it into electricity. The “organic photovoltaic cells,” as they are called, are made of plastic. Plastic solar cells have been around for a while, attractive because they are cheaper and more environmentally benign than those made of silicon. But they are also far less efficient.

The UCLA chemists have created a new, plastic-based material that retains solar energy for weeks rather than microseconds. It does this by keeping apart the positive and negative electrical charges, much like plants do.

The researchers have not yet created a working solar cell using their new material, but it’s possible to imagine how one would behave once it is created. Not only would the organic solar cells be more efficient, but they might be tweaked to act as solar energy storage devices, the way leaves store excess solar energy to be released as needed.

If the new material can be used to create solar cells cheaply, on an industrial scale, the technology could revolutionize the way solar energy is gathered and stored. The system would negate the need to create elaborate storage devices like batteries, and could bring us closer to the day rooftop solar panels are as common as roof shingles, providing clean energy off the grid.