What is Exergy? We refer to the following definition from a paper of Wes Hermann:
Exergy is used as a common currency to assess and compare the reservoirs of theoretically extractable work we call energy resources. Resources consist of matter or energy with properties different from the predominant conditions in the environment. These differences can be classified as physical, chemical, or nuclear exergy. This paper identifies the primary exergy reservoirs that supply exergy to the biosphere and quantifies the intensive and extensive exergy of their derivative secondary reservoirs, or resources.Wes Hermann not only calculates the available Exergy from most energy sources, he also determines where particular energy resources are most plentiful. ("How much solar energy can one generate if one blanketed the earth's ENTIRE surface with the most efficient solar panels?") In essence, Wes Hermann sets out to calculate the terrestrial potential from all possible energy sources. He concludes that Solar, Wind, and Nuclear (in that order) are the most plentiful. In addition, Hermann locates the best places to harvest each possible energy source. In the sample graph below, we have the Tidal Power available (in watts per sq. meter) across the planet:
Similar maps can be constructed for other energy sources. In an ideal world, precious materials (e.g. silicon for solar panels) would be deployed in areas with the most potential (solar) Exergy.
Starting from the current global Exergy consumption of 18TW, Exergy calculations should inform energy policy. The 18TW is set to grow as the India, China, and the Southeast Asian economies continue to develop. Using the U.S. as an example, economic growth is positively correlated to energy consumption:
India and China's economies are growing at a steady pace, so the 18TW total Exergy consumed is sure to rise sharply:
Just like energy consumption, Ecological footprints rise as countries (see Human Development Index) develop:
The size of the populations of the fast-growing Asian countries means we need to pay attention to Exergy now!
Of course the Indian, Chinese, and ASEAN economies may hit obstacles along the way, but sound energy policy suggests that we assume that they will continue to develop in a modest pace.
Actually in another interesting discussion at FOO camp, Steve Hsu pointed out an interesting fact: historically, China's share of the world's GDP was quite high.
Using PPP (purchasing power parity), China's share of the world's GDP may actually just be reverting to its historical values. Look for China's ecological footprint, and Exegy consumption, to keep rising. Unless we act soon, the current 18 TW global Exegy consumption will surely look small in a few decades.