Battery Energy Storage System (BESS) described as delivering say 50MW, 100MW etc, these are 50 or 100 million watts. This is meaningless in terms of the total energy in the system which needs to be expressed in watt-hours, kilowatt hours or Megawatt-hours. If you turn on a 3kW electric fire and run it for 1 hour you consume 3 kW-hours of electricity. The average household uses 3.7 MWh per year.

The energy is stored in the BESS in thousands of Lithium ion cells linked up in series and parallel. (Remember that the 12volt starter motor battery used in motor vehicles is composed of 6 lead acid cells linked in series. Each of these cell provides 2 volts, and linked in series, they provide just over 12 volts).

Battery Energy Storage Systems or any capacity should present deep concerns in regard to the real possibility of devastating battery fires.
The charging and discharging of the battery give out significant amount of heat, due to the high currents which flow through the cells. Adequate cooling must be provided. Often this is air conditioning with the warm air being drawn out of the sytem and replaced by cool air.
A closed ycle air conditioning system guards against changes in temperature in the outside environment. However, heat exchange unit needs to be used to the air being pumped out of the cabinets and cooled down before re-entering.
The use of pumps and electric motors runnig continuously night and day can create environmental noise pollution. Also there may be extensive use of water to provide the cooling for the heat exchange units.

Furthermore, attention needs to be drawn to the sheer size and weight of the battery components which must be delivered and manoeuvred into place down country lanes with consequent disruption of normal life during the construction of the energy storage system.