Battery Energy Storage Systems (BESS) is a technology that stores charges using specially developed batteries. The basic idea is to be able to utilize this stored energy at a later time. Extensive research has led to the development of battery technology, turning the concept of battery energy systems into a commercial reality. BESS is a subset of Energy Storage Systems (ESS). Energy storage systems refer to the ability of a system to store energy using thermal, electro-mechanical, or electrochemical solutions. BESS typically employs electrochemical solutions.
Essentially, all energy storage systems capture and store energy for future use. Examples of these systems include pumped storage, compressed air storage, mechanical flywheels, and now BESS. These systems complement intermittent energy sources such as wind, tidal, and solar, attempting to balance the production and consumption of energy. Energy storage reduces peak power system demand, and ESS owners are typically compensated through regional electricity market programs. Regulatory bodies also offer incentives (in some cases mandatory) to encourage participation.
BESS has advantages over other storage technologies because it has a small footprint and no geographic limitations where it can be located. Other storage technologies are only applicable to a limited number of locations, considering water and site-related restrictions as well as transmission limitations. Thus, BESS utilizing lithium-ion technology provides high energy and power density suitable for distribution transformer-level usage. The available space at the distribution transformer setup can be utilized to position BESS. The maximum duration of the evening peak to be managed is around 4 hours, therefore, the discharge time required for a specific BESS is less than 4 hours. Thus, BESS only needs to provide partial capacity during peak times, lasting up to a maximum of 4 hours.
Round-trip efficiency: It represents the amount of usable energy released from the storage system relative to the energy inputted. This indicates the energy lost during each charging and discharging cycle. Typical values range from 60% to 95%.
Response time: It is the time it takes for a battery energy storage system to transition from standby mode to full output. This performance criterion is an important indicator of the storage flexibility as a grid resource relative to alternative solutions. Most storage systems have short response times, typically less than a minute. Compared to batteries, pumped storage and compressed air storage tend to be relatively slower.
Ramp rate: Ramp rate represents the rate at which the power output of a storage system can be changed. The ramp rate of batteries may change faster than 100% within one to a few seconds. The slope of pumped storage and compressed air storage is similar to that of conventional generation facilities.
Energy retention or standby losses: Energy retention time is the duration in which a storage system retains its charge. The concept of energy retention is important as certain types of storage devices self-discharge or dissipate energy when not in use.
Energy density: It is the amount of energy that can be stored per given area, volume, or mass. This criterion is important in applications where area is a limiting factor, such as in urban substations where space may restrict site energy storage.
Power density: Power density represents the amount of power that can be delivered per given area, volume, or mass. Additionally, similar to energy density, power density also varies significantly among storage types. Again, if area or space is limited or weight is a concern, power density is important.
Safety: Safety is related to the specific materials and processes involved in electricity and battery energy storage systems. The chemicals and reactions used in batteries can pose safety or fire hazards.