Basic Components of an Energy Storage System

In its most basic form, energy storage absorbs energy to be released at a later time. Most commonly, the input and output to the energy storage system is electricity but systems that store heat and kinetic energy also exist. Each energy storage unit or facility is made up of three subsystems: the storage medium, the power conversion system and the balance of the plant (Baxter, 2006). A description of each subsystem is as follows:

·        Storage Medium – the storage medium is the reservoir in which energy, in an energy storage system, is stored. The energy can be stored in the form of chemical energy, electrochemical energy, electrical energy, mechanical energy and thermal energy. The energy density of the storage medium often dictates the size of the storage device relative to its desired power and energy output. Low energy density, high power storage devices tend to be physically larger than high energy density, low power storage devices. Generally accounting for one half the cost of the storage unit, the cost of the medium is divided into the capital cost of the medium and the cost of maintaining the medium in a charged state (Baxter, 2006).

·        Power Conversion System (PCS) – is the interface between the storage medium and the end user of the storage system’s output. If the output is electrical, the PCS will need to not only convert the power from the storage medium but also condition the electricity so that it is appropriate for consumption. Often, the PCS is also used to charge the energy storage medium. The PCS can often account for greater than 25% of the cost of the storage unit; more commonly in the range of 33% to 50% (Sandia Corporation, 2012).

·        Balance of Plant (BOP) – the BOP is essentially the components of the storage unit that are not the storage medium or the PCS. The BOP can include equipment to control the environment of the storage medium and the PCS, equipment to house and shelter the storage device, and other equipment necessary for operation. BOP tends to be the most variable component cost across energy storage devices, representing the remainder of costs after the storage medium and PCS. The BOP is typically in the range of 10% to 30% of the overall device costs (Baxter, 2006).

Works Cited

Baxter, R. (2006). Energy Storage; A Nontechnical Guide. Tulsa, Oklahoma: PennWell Corporation.

Sandia Corporation. (2012). Energy Storage Systems - Technology; Power Electronics. Retrieved January 5, 2012, from Sandia National Laboratories: http://www.sandia.gov/ess/tech_power.html