The energy storage is the act of placing a quantity of energy in a given place to allow its subsequent use. By extension, the term “energy storage” is often used to describe the storage of material that contains this energy.Control of energy storage is particularly important to develop alternative energies such as wind or solar , safe and renewable, but inherently intermittent. There is many solve to stock energy :
The electricity is an energy and a secondary energy carrier , that is to say, it results from the conversion of primary energy. Once produced it is instantly consumed or lost. It is not directly storable (except in a capacitor ), and must be converted to another form of energy to be stored.
Storing large amounts of electricity with electrochemical storage giant has never been realized. The electrochemical storage are generally heavy, expensive, have a limited life and pose problems of pollution ( acids and heavy metals ) at their end of life, and sometimes even fire or explosion when fate of their normal use.
By cons, many home systems disconnected from the electricity distribution network is based on the use of accumulator battery or batteries . In practice, they are useful for small devices appliances or airborne electronic equipment.
Recently a renewed interest in vehicles with low or no pollutant gases has revived the creation of electric vehicles :bicycles and cars running completely through this type of energy or as hybrid (electricity to supplement fossil fuel).
The capacitors of medium and large capacity, so-called chemical capacitors and ” SuperCap “are another use of electrochemical systems to store energy. Their use is very common in appliances and machinery electrical with or without electronic board.
The dams provide water reserves which fell in pipes, operate the turbines supplying energy to mechanical generators of electricity.
A system optimization is to reuse the water stored or end of a river at the foot of the hydroelectric plant. Storage for pumped storage (also called STEP: Energy Transfer Station by pumping) is used to equalize the daily load (that is to say the need for electricity): water is pumped and up towards the dams of altitude when demand on the network is low (during peak hours and weekend for example), using the surplus production of energy sources, non-adjustable ( nuclear , solar , wind , …) ; during peak consumption, the water goes down under pressure and produce electricity again.
This is the same device electromechanical reversible, which produces electricity in turbines to go up or consumes water by pumping. The yield is good (around 80% across the plant, taking into account the losses in the pipe, engine performance / alternators, pumps / turbines and transformers). However, relatively few suitable places: with storage dams of sufficient size and with a large height difference between the dams / water reservoirs above and below.
It also uses a variant of this device in the tidal power plant of the Rance (France): at high tide, we do not just passively storing water is pumped also to increase the pool, this water is released to advantageously low tide (one goes up the water a few meters, by using against the potential drop over a dozen meters higher)
We can use the compressed air to produce mechanical work, therefore it is possible to store energy by compressing a gas (usually with a compressor driven by electrical energy available). The performance will be poor, because the compression results in a heating of the gas, except to recover the heat (cogeneration heat + air) . One such system is being developed by the company Enairys .
On a larger scale, can be used underground caves or old mines to store compressed air. When there is a strong demand for electricity, air is used that was previously compressed and stored in order to move a turbine with a generator that produces electricity. Facilities of this type have been implemented or are planned to McIntosh in Alabama (USA) , in Iowaand Germany , although the yield is only about 40%.
A variant of this system for storing compressed air in a tank deep submarine (1000-2000 m), is developing in the UK with the support of electricity producer E.ON .