Overview

Of the many possible ways of storing electrical energy, the only ones that are truly practical and widely used today are pumped hydro on the medium-to-large scale and battery storage on the small-to-medium scale. Other possibilities (compressed air, flywheels, electromagnetic and electrostatic energy storage, hydrogen) are still in the development stage and, as yet, only have limited application in special situations. It is therefore appropriate that we should devote a Chapter to battery storage.

Batteries are of two basic types: 'primary' batteries that are discharged once and then discarded, and 'secondary' batteries that are recharged many times. Here, we are concerned only with the latter type. Another useful distinction is between 'consumer' batteries as purchased by the individual, and 'industrial' batteries as used in industry and commerce. Most consumer rechargeable batteries are small, single-cell devices (with the notable exception of the automotive battery), whereas industrial batteries tend to be much larger, multi-cell modules.

The manufacture of batteries is a growth industry. The reasons for this are quite clear. There is a huge increase in the sales of portable electronic devices (mobile telephones, laptop and notebook computers, camcorders, etc.) that require battery power, and also of mains-connected devices that use batteries for memory back-up. Industry and commerce are creating a strong growth in the demand for stationary batteries to provide instantaneous power in the event of mains failure (see uninterruptible power supplies, Section 6.3, Chapter 6). In the transport sector, electric traction is proving more popular in environmentally sensitive...