Since the late 1980s, there have been several attempts to investigate the possibility of harvesting lightning energy. A single bolt of lightning carries a relatively large amount of energy (approximately 5 billion joules[1] or about the energy stored in 145 litres of petrol).  However, this energy is concentrated in a small location and is passed during an extremely short period of time (microseconds[2]); therefore, extremely high electrical power is involved.[3] 5 billion joules over 10 microseconds is equal to 5×1014 (or 500 trillion) watts. Because lightning bolts vary in voltage and current, a more average calculation would be 1×1010 (or 10 billion) watts.[4]  It has been proposed that the energy contained in lightning be used to generate hydrogen from water, to harness the energy from rapid heating of water due to lightning,[5] or to use a group of lightning arresters to harness a strike, either directly or by converting it to heat or mechanical energy,[6] or to use inductors spaced far enough away so that a safe fraction of the energy might be captured.[7]