How is Solar Energy Stored?

Many people with solar panels installed in their home don’t realize that the thermal energy collected by the panels can be stored for later use. There are indeed several ways to store solar energy. It can be stored in a packed bed, in a heat-of-fusion storage unit or even in water.

Image Credit: Optics InfoBase

Packed Bed
Also known as thermal energy storage systems, packed beds are containers that hold small objects capable of storing solar energy. The objects, sometimes referred to as the packing material, may be stones, Raschig rings or any other spherical particles. Some packed beds contain structured packing instead of small, individual particles. Structured packing typically consists of corrugated plates of perforated embossed metal or, alternatively, wire gauze. In addition to packing material, a packed bed can also contain catalyst adsorbents such as nitrogen enriched activated carbons or zeolite pellets.

Image Source: Next Big Future

Heat-of-Fusion Storage Unit
Heat-of-fusion storage units are usually used to store larger amounts of energy than packed beds are able to. Also known as phase-changer units, these devices store solar energy in a chemical that changes phase from solid to liquid in order to act as a vehicle for storage. The clever thing about the whole storage process is that it’s the solar energy itself that enables the chemical to change to its liquid phase. Once stored in the chemical, the thermal energy can be tapped at a later point in time. Tapping into the energy allows the chemical to return to its solid form.

As with chemical liquids, hot water can both be produced by and store solar energy. In a home with access to solar power, the hot water tank will fill up during daylight hours. The water in the tank can then be used as and when needed. Water doesn’t necessarily have to be in such a tank to store solar energy. Swimming pools are also often used as storage units, being heated by the very same solar energy they store. A cover is usually put over the pool when it’s not in use, in order to retain heat and thus maintain the water’s warm temperature.

Thanks to these devices and methods, solar energy isn’t just for use when the sun is out. As long as enough thermal energy has been stored away, a person can have a hot bath or take a swim in a heated pool in the middle of the night, if they so wish.

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