quality evaluation methods There appear to be two main kinds of methodology used for the calculation of energy quality. These can be classed as either receiver or donor methods. One of the main differences that distinguishes these classes is the assumption of whether energy quality can be upgraded in an energy transformation process. Receiver methods: view energy quality as a measure and indicator of the relative ease with which energy converts from one form to another. That is, how much energy is received from a transformation or transfer process. For example, A. Grubler used two types of indicators of energetic quality pars pro toto: the hydrogen/carbon (H/C) ratio, and its inverse, the carbon intensity of energy. Grubler used the latter as an indicator of relative environmental quality. However Ohta says that in multistage industrial conversion systems, such as a hydrogen production system using solar energy, the energy quality is not upgraded (1994, p. 125). Donor methods: view energy quality as a measure of the amount of energy used in an energy transformation, and that goes into sustaining a product or service (H.T.Odum 1975, p. 3). That is how much energy is donated to an energy transformation process. These methods are used in ecological physical chemistry, and ecosystem evaluation. From this view, in contrast with that outlined by Ohta, energy quality is upgraded in the multistage trophic conversions of ecological systems. Here, upgraded energy quality has a greater capacity to feedback and control lower grades of energy quality. Donor methods attempt to understand the usefulness of an energetic process by quantifying the extent to which higher quality energy controls lower quality energy. Energy quality in physical-chemical science (direct energy transformations) Constant energy form but variable energy flow T. Ohta suggested that the concept of energy quality may be more intuitive if one considers examples where the form of energy remains constant but the amount of energy flowing, or transferred is varied. For instance if we consider only the inertial form of energy, then the energy quality of a moving body is higher when it moves with a greater velocity. If we consider only the heat form of energy, then a higher temperature has higher quality. And if we consider only the light form of energy then light with higher frequency has greater quality (Ohta 1994, p. 90). All these differences in energy quality are therefore easily measured with the appropriate scientific