ABSTRACT
The important parameters by which the energy storage technologies can be characterised are: (a) Extent, which is the amount of energy that the said device can store. This can be specied as gravimetric energy density (Wh/ kg) and this emphasises the weight of the device. Alternatively, volumetric energy density (Wh/L) can also be a measure, and this emphasises the size of the device. This will be an important specication in dealing with applications where available space is restricted; (b) The delivery rate, which is a certain rate at which the energy needs to be made available. With enduse applications in mind, availability of power can be rated as W/kg and or W/L; (c) The life for which the energy storage devices will be used to store
and withdraw energy. The device then cycles between storage and supply or charge and discharge. No device is ever perfectly reversible, even if mechanical wear and tear is ignored. It has a nite life and is measured in terms of number of cycles of charge and discharge it can withstand before replacement is needed; (d) The response time is a critical factor; when the need for additional power arises a storage system has to respond quickly. Large systems that are used in energy management, are the ones that take time to respond. The quality power systems are generally electrochemical in nature and are used along with electronic control systems that have been designed to make these respond rapidly. An example is a UPS commonly used with a PC. The electronics however do add to the cost; (e) The safety of the device during its use is a critical factor. The commercial success of a device depends on safety during its use; (f) Recyclability of the materials employed in the device is an important factor as it controls the environmental pollution; and (g) Last but not least is the all important factor of cost, which directly determines consumer interest and marketability.
