petajoule - definition"

Just thought it might be of use to have definition of Petajoule - I certainly did not readily have a clear grasp of what it is

"A measure of energy equivalent to a thousand trillion joules, or 1,000,000,000,000,000 joules, or roughly 30 million kilowatt-hours. Usually used to express energy consumption by large customers such as cities or major industries, or cumulative output from commercial energy production facilities."

Of course the big question is how much of it can be economically extracted (if any)

However , with global warming & peak oil, current account deficit etc...there are many reasons and incentives to use this energy resource if at all possible