DERs are small, modular, energy generation and storage technologies that provide electric energy installed on site and of a size meeting local need. Furthermore, DER systems may be either connected to the local electric grid or isolated from the grid in stand-alone applications. DER technologies include renewable energy sources (e.g. wind turbines and solar photovoltaics), micro turbines, reciprocating engines, combustion turbines, cogeneration and electrical energy storage (EES) systems. Utilities can use DER technologies to delay, reduce or even eliminate the need to obtain additional central power generation, transmission and distribution equipment and infrastructure. Meanwhile, DER systems can provide voltage support and enhance local reliability. Therefore, the perspective of the electrical power grid in future can be seen as an integration of conventional generation and DERs and consequently the power flow can be bi-directional as shown in Figure 7.2.
Electrical energy storage, Page 1 of 2
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