Renewable energy needs storage

The use of wind, solar and decentralized generation will have to increase significantly in order to turn our power generation sustainable. This will have a major impact on the current energy system, which is based on real time power production following demand. The supply of energy from renewable sources however is not easy to control. Storage is needed, as well as innovative ways to keep the supply and demand balanced.

Energy storage aims to create a fast controllable energy buffer. It stores energy when a surplus is available, and delivers back during times of shortage. Switzerland and Austria already use hydropower for storage. Another technology, used in Germany, is called: compressed air energy storage (CAES). Energy is stored by compressing air in, for example, an underground salt cavern. When set free again the air pressure is used to generate power.

Ways of power storage currently researched in the Netherlands are the underground pump accumulation plant (OPAC) in the province of Limburg and the energy isle in front of the Dutch coast. Both projects use energy surpluses to pump water to a higher level. In case of OPAC this is water from an underground lake approximately 1400 m deep. In case of the energy isle water from an artificial lake, 30 m deep, is pumped to sea level. When there is an energy shortage, the water is dropped again. A vigorous waterfall comes to existence and generates power.

Demand side management (DSM) or demand response controls both the electricity load and production on the demand side, by controlling local assets on a distance. The most feasible assets at this day and age are (micro-)CHPs, especially with heat storage, heat pumps, and electric cars. Most of which are a form of energy storage. The main issue with DSM is how to control a fast growing number of assets without interfering with their main purpose and which belong to someone else.

All these individual devices together create a mobile smart grid. A system designed to control the charging of electric vehicles in a way the grid capacity won’t be exceeded. Micro CHP’s, heat pumps and electric vehicles need to be coordinated in order to create enough regulating power to balance the supply and demand of electricity. This will change our point of view on issues like ownership, main purpose and availability of the diverse assets.

Ecolutie, March 4 2010

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