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Energy Storage
Have you ever wondered what happens to all of the electricity that is produced but not used? While you may think that it is going to waste, there are energy storage systems to help store this excess energy for later usage. This reduces the demand on the environment and cuts down on wastage. Read on to learn more.
Why is Energy Storage Necessary?
Energy storage is becoming an increasing concern as the cost of energy increases. By storing energy, you cut down on wastage. This is especially true of electrical energy as if it is not used, it simply goes to waste. Electrical energy cannot be stored directly, although it can be indirectly stored by converting the electrical energy to some other form of energy (storage energy). When electrical energy is required, the storage energy is then converted back into electrical energy.
Energy storage facilities allow power generation facilities to be more evenly used. For example, the additional energy generated during off peak hours can be converted and stored, and then reconverted for use during peak hours, when demand is higher. The most commonly used energy storage systems are pumped hydroelectric storage, batteries, and compressed air storage.
Pumped Hydroelectric Storage
In pumped hydroelectric storage, electrical energy from the electricity network is used to pump water from a lower level water storage to a higher level water storage. The electrical energy is stored as the gravitational potential energy of the water in the higher storage. When it is needed, the water in the higher storage is released and flows through a turbine on its way back to lower storage. The potential energy in the water is reconverted into electrical energy by the turbine. This system may have a storage efficiency as low as 70 percent.
Batteries
Battery storage is made up of the battery, DC/AC converter, transformer, AC switchgear, and a casing to house all of these parts. Batteries are able to be added to in small increments, meaning that they are capable of matching growth in energy production. They also provide dynamic source benefits as they provide spinning reserve, area frequency, and voltage control, as well as increased system reliability. Because batteries come in small sizes and can be located in virtually any area, they can be located near the site of energy production, meaning that there are minimal losses. However, batteries do cost a lot initially, and those that use existing technologies require replacing every eight to ten years. Currently the only battery available for large energy storage applications is the lead-acid battery.
Compressed Air Energy Storage
Compressed air energy storage (CAES) is a technology in which energy is stored in the form of compressed air in an underground cavern. The air is compressed during off peak periods, stored in the cavern, and then used on demand in peak periods to generate power with a turbo generator system. The electricity from the grid powers an electric motor which drives an air compressor. The heat generated by the compression process is extracted by inter stage cooling and after cooling and stored. Most of the electricity from the grid is therefore stored as the pressure potential energy of the compressed air in the cavern. When air is taken from the cavern, it is preheated in the recuperator, which reuses the energy extracted by the compressor coolers. The heated air is then mixed with small quantities of oil or gas, which is burned in the combustor and the hot gas from the combustor is expanded in the turbine to generate electricity.
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