Energy storage

Energy storage are used to store energy for later use. Is storing an energy form because of technical problems, insufficient capacity or downtime losses unfavorable, it is converted and stored in a different, more suitable for the storage, energy form. If necessary, the energy is converted back. An example is the conversion of chemical energy (fuel) into thermal energy (heat). Both in storage and in the conversion of energy more losses occur.

Classification and survey

Energy storage to be classified according to the stored (main) power form. Often, however, a deviating form of energy is used when loading or unloading the memory. The battery, electric power is supplied, for example; this is converted into chemical energy during charging:

  • Thermal energy: heat storage, district heat storage, Thermochemical heat storage, latent heat storage
  • Chemical energy: inorganic: galvanic cell ( battery, battery), redox flow cell, hydrogen, battery storage power plant
  • Organic: ADP, ATP, AMP, glycogen, carbohydrates, fats, hydrogen storage
  • Kinetic energy ( energy of motion ): flywheel or flywheel storage
  • Potential energy ( potential energy ): spring, pump storage power plant, compressed air storage power plant, Hubspeicherkraftwerk

In addition, the term is sometimes also used for container, the self- absorb any energy, but fuel or motor fuel:

  • Cavern storage for crude oil, natural gas and compressed air
  • Biogas storage that can store approximately between a daily production of biogas power plant.
  • Pore ​​space for natural gas
  • Storage tank and fuel tank
  • Adsorption

The fuel cell is often referred to as an energy storage. However, it is only able to obtain electric energy from chemical reactions.

Storing electrical energy

Electrical energy can be difficult to directly store (in capacitors or superconducting coils). Generally it is more economical to convert the energy into another form of energy and reconvert if necessary. Each conversion is lossy, and the memory can even lose energy over time. The sum of all individual losses may be significant and make the process uneconomical.

The efficiency of the method is in energy storage mostly in the foreground, so the investment and operating costs of the system and the overall efficiency. It is at least in large plants usually not a short-term power increase. For very small systems such as the electronic flash is sometimes the power increase in the foreground, for example because the original energy source can not deliver enough power.

The data refer to the major systems installed in permanent operation.


  • The power constraint refers in all cases that the energy stored again ( an inverter, for example ) converted by a " conversion electronics " in the original type returns must - this is usually the 50 - Hz power. The above values ​​may be far exceeded without this reconversion, if one shorts such as a capacitor or a battery - then the instantaneous power by a factor of 10,000 or more may be higher than indicated in the table. But in the table it comes to energy storage and power not to increase.
  • The lifetimes given are estimated indicative and not absolute limits. For example, a flywheel fail long before reaching the 1- million limit or scrapped earlier. For batteries in most cases ( car battery) is known to withstand 7000 cycles in exceptional cases, but must be replaced after 1000 cycles.
  • When methane and hydrogen, respectively, the compression of the gas at 80 bar ( gas pipeline ) have been considered for the efficiency. The better efficiency here refers to the possibility of the production of electricity and heat ( CHP).

Memory problems in the context of " energy revolution"

In addition to the annex large routes for long distance transmission, the power system of the future changed particularly in the area of the distribution network, as generation, storage and consumption must take place almost at the same time here. Different pattern of variation of photovoltaic ( PV), wind and power consumption also require capacity for various periods of time. Depending on the observed time scale of several technologies are used, which can be identified following time windows:

  • Subsecond to minutes ( Einspeisefluktuationen );
  • Up to one day ( eg daily pattern PV);
  • Up to three days ( random fluctuations );
  • One to two weeks (prolonged high-or low wind periods);
  • Seasonal adjustment.