The concept of energy harvesting signifies an integrated approach to the gathering of energy, usually fiom natural resources, with centralised collection providing for subsequent distribution according to requirements. On Earth, by far the most significant source of available energy is solar in origin. For the abundance of the environmental resource it represents, and also the extent of its geographic availability, solar energy easily outstrips any competition. Each year, in excess of J of solar energy impinges on the Earth, surpassing by a factor of more than a hundred the next largest source, wind energy.