Other Methods of Storing Solar or Wind Energy
Batteries are always the prime solution that we have in solving the problem of renewable energy intermittency. Even during days when your solar array or wind turbines cannot generate electricity properly, the battery banks could at least provide a time window, as well as enabling the regulated flow of electricity to your household appliances, gadgets and utilities.
But storing energy is hardly the work of batteries alone. In the quest to solve the problem of intermittency in the most economical way possible, scientists and researchers have come up with many more different ways to store electricity that is generated from solar and wind power.
- Molten salts – this is the traditional energy storing material for concentrated solar thermal energy systems. Molten salts are usually kept in two tanks, one kept cooled and one kept hot. Concentrated solar thermal energy systems store energy in these salts by directly heating one tank. When energy is needed, the system simply lets the hot molten salt pass through the heat exchanger, where it generates steam for the heat engine during the absence of heat from the solar collectors (heliostats).
- Hydrogen – another straightforward source of energy for several fuel-cell systems today. With a simple electrolyzer, you can use the electricity generated by your solar array or wind turbine to separate hydrogen from water and store in a tank. To “reuse” the stored energy, you simply have to find the proper fuel-cell generator that would generate electricity from the stored hydrogen. The working principle is very easy, although it does suffer from efficiency issues due to multiple energy transfer “points”.
- Compressed air -the principle of this storage method uses the simple kinetic energy produced by expanding air. Storage for compressed air systems requires the solar or wind energy system to provide power to the compression process. To extract the stored energy, air is simply blown out of the underground earth cavity “tank”. The expanded air would then make a turbine spin, allowing the connected generator to produce electricity. One notable downside of this storage method is that compression should be done in “heat-exchanged” stages, or else the compressed air would heat up and the expanded air would cool down.
- Pumped water – stored hydroelectric energy is also built on roughly the same working principle as compressed air. When the solar or wind energy system is at its peak energy generation rate, it can use surplus energy to pump water to a high storage reservoir. When it’s time to collect the stored energy, the pumped water is simply made to flow downward to power a water turbine. This is one of the energy storage systems listed here that are in wide use today, even for standard coal-power energy systems.
- Insulated gravel – it is a relatively new method of storing electricity from a renewable energy system. This method works pretty much like a molten salt tank, where the temperature difference of the hotter gravel-gas tank to the colder gravel-gas tank is used to power a heat engine. The only difference is that this system does not use other chemicals, water or refrigerants.
With the exception of the hydrogen energy storage concept, all of the methods described here are usually effective only for large scale energy storage systems. These are energy storage solutions that can only be put into consideration when designing entire power plants that fully rely on renewable green energy. For residential scale applications, the old trusty battery bank might still be the most practical option.
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