90). It is evident that Ohta did not analyse all forms of energy. For example, water is left out of his evaluation. It is important to note that the ranking of energy quality is not determined solely with reference to the efficiency of the energy conversion. This is to say that the evaluation of "relative ease" of an energy conversion is only partly dependent on transformation efficiency. As Ohta wrote, "the turbine generator and the electric motor have nearly the same efficiency, therefore we cannot say which has the higher quality" (1994, p. 90). Ohta therefore also included, 'abundance in nature' as another criterion for the determination energy quality rank. For example, Ohta said that, "the only electrical energy which exists in natural circumstances is lightning, while many mechanical energies exist." (Ibid.). (See also table 1. in Wall's article for another example ranking of energy quality). Transformity as an energy measure of hierarchical rank Like Ohta, H.T.Odum also sought to order energy form conversions according to their quality, however his hierarchical scale for ranking was based on extending ecological system food chain concepts to thermodynamics rather than simply relative ease of transformation . For H.T.Odum energy quality rank is based on the amount of energy of one form required to generate a unit of another energy form. The ratio of one energy form input to a different energy form output was what H.T.Odum and colleagues called transformity: "the EMERGY per unit energy in units of emjoules per joule" (H.T.Odum 1988, p. 1135). See also EKOenergy ecolabel for energy Green energy Eugene Green Energy Standard ISO 14001 Monism Emergy Renewable energy Renewable energy development Transformity Thermodynamics Energy accounting Energy economics Pirsig's metaphysics of Quality References M.T. Brown and S. Ulgiati (2004) 'Energy quality, emergy, and transformity: H.T. Odum's contributions to quantifying and understanding systems, Ecological Modelling, Vol. 178, pp. 201–213. C. J. Cleveland, R. K. Kaufmann, and D. I. Stern (2000) 'Aggregation and the role of energy in the economy', Ecological Economics, Vol. 32, pp. 301–318. A.W. Culp Jr. (1979) Principles of Energy Conversion, McGraw-Hill Book Company I.Dincer and Y.A. Cengel (2001) 'Energy, Entropy and Exergy Concepts and Their Roles in Thermal Engineering', Entropy, Vol. 3, pp. 116–149. B.Fleay (2006) Senate Rural and Regional Affairs and Transport Committee Inquiry into Australia’s Future Oil Supply and Alternative transport Fuels S.Glasstone (1937) The Electrochemistry of Solutions, Methuen, Great Britain. S.E.Jorgensen and G.Bendoricchio (2001)