Energy storage
From WikiClimate
As renewable energy is not always available when needed, methods have to be found to store energy for use when wanted. Essentially this can be done by storing electricity, or storing energy in some other form that can then be quickly and conveniently converted back to electricity when needed.
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Storage Methods
Suggested storage methods include:
Intermediary Storage
- Pumped Hydro (Potential Energy)
- Compressed Air Energy Storage (Potential Energy)
- Flywheels (Kinetic Energy)
- Conversion to Hydrogen, for use in fuel cells (Chemical Energy)
- Conversion to Hydrocarbons, for subsequent combustion (Chemical Energy)
- Phase change materials (PCMs) - (Latent Energy)
- Paraffin waxes. These are cheap and have moderate thermal energy storage density but low thermal conductivity meaning they require a relatively large surface area. They are often based around fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid and stearic acid.
- Hydrated salts, such as Glauber's salt (Sodium Sulphate decahydrate). These have a greater energy storage density and higher thermal conductivity but may experience supercooling and phase segregation.
- Metals. These work better at higher temperatures (eg. in short term storage of heat from industrial processes) and have excellent thermal conductivity.
- Use in Buildings. Typically PCMs can be incorporated into a Gypsum wallboard or trombe walls, although they may also be incorporated into shutters, ceiling boards or warm air heating systems.
- Storage as hot liquids, usually water (Thermal Energy)
- Inter-seasonal storage with low temperature differences, eg. solar ponds or ground storage (Thermal Energy)
Pure Electrical Storage
- Lead-Acid Batteries
- NiCad (Nickel-Cadmium) Batteries
- Sodium Sulphur Batteries
- Flow Batteries
- Superconducting Magnetic Energy Storage
- Electrochemical Capacitors
Problems with Storage
There are two main problems with any form of storage:
- losses, both in conversion to and from the storage medium, and while being retained as that medium (ie. leakage)
- availability - how quickly can stored energy be brought back on line, and converted into the required form (usually electricity)?
Some of items on the list, such as pumped hydro, are well developed and have been used for many years as backup energy storage for primarily fossil fuelled electricity networks. Others are still at a very early stage of development and many never prove to be cost-effective.
Natural Storage of Energy
Much of the energy that we use is stored solar energy, in one form or another. Apart from fossil fuels (which is in effect using solar energy stored many millions of years ago, and releasing carbon trapped at the same time), the most common form of natural energy storage is in plants, for use as biomass or biofuels. However thermal energy is also naturally stored in the ground, and this can captured by Ground Source Heat Pumps.
