Introduction Energy is necessary for a number of reasons, the most basic and obvious involve the preparation of food and the provision of heat to make life comfortable, or at least, bearable. Subsequently, a wide range of technological uses of energy have emerged and been developed, so that the availability of energy has become a central issue in society. The easiest way to acquire useful energy is to simply ?nd it as wood or a hydrocarbon fossil fuel in nature. But it has often been found to be advantageous to convert what is simply available in nature into more useful forms, and the...