So many of us are used to storing electricity in batteries, that one might be led to think that this is perhaps the only way to store electricity.
Batteries are of course the most obvious way to store energy.
But here are a few more
- Fuel Cells – in this case, the energy is stored in the form of hydrogen, which when combined with oxygen, gives out energy along with – water!
- Pumped Storage – in this interesting concept, electricity is used to pump water to a higher altitude (a reservoir), and the energy is released when the water is released from the reservoir to run a turbine. Thus, the energy is stored in the form of the potential energy which can be converted to electrical energy back again based on requirements.
- Phase Change Materials – many materials change from one phase to another when subjected to heat – from solid to liquid, or from liquid to vapour etc. When for instance a solid changes phase to liquid when heated, the heat energy is stored in the liquid, which, when converted back to the solid form, releases the energy. This concept can be used to store electricity in systems such as concentrating solar power, where, heat energy stored in a phase change material such as molten salt is released during its solidification to generate steam, which in turn runs a turbine to generate power.
The other two, not so well-known but commercially used energy storage technologies include:
- Compressed Air Storage (CAS) – CAS has seen some use in renewable energy storage in the recent past, but they have not yet been used for large scale enery storage. Part of the reason is that is the cost – my estimates say that compressed air storage are far more expensive per unit of energy delivered than batteries, as of 2016.
- Energy Storage in Flywheels – Flywheels are already used as an energy storage source in a host of regular electrical as well as mechanical equipment and gadgets, but their use as a large scale source of renewable energy / power storage is just beginning. In fact, some of the flywheel manufacturing companies I have been in touch with have been keen on expanding their solution portfolio to start serving the renewable energy markets as well, but my suggestion to them had been to hold their horse until the market matures a bit more.