Hierarchy of energy: emergy and transformity

   by

Erik Grönlund

Text by Robert Onsander  

   On Thursday, 6 March 2014, Dr. Erik Grönlund, a researcher and lecturer at the department of Ecotechnology and Sustainable Building Engineering in Mid Sweden University, presented about the hierarchy of energy. He started with referring to the laws of thermodynamics and how unclear they are in our understanding of energy systems. He mentioned about the need to be able to understand, describe and evaluate more complex systems and networks such as ecosystems. Life Cycle Analysis (LCA), Environmental Impact Assessment (EIA), Material Flow Analysis (MFA), Substance Flow Analysis (SFA) and Ecological footprint are all examples of tools developed for this purpose.

   Another tool is the Emergy evaluation linked to a proposed 5th law of thermodynamics covering the understanding of more complex networks and to be seen as a supplement to the existing thermodynamic laws. Emergy is the available energy of one form that is used up in transformations directly and indirectly to make a product or service. The unit of emergy is the emergy joule or emjoule. Using emergy, sunlight, fuel, electricity, and human service can be put on a common basis by expressing each of them in the emjoules of solar energy that is required to produce them. If solar emergy is the baseline, then the results are solar emjoules. Although other baselines have been used, such as coal emjoules or electrical emjoules, in most cases emergy data are given in solar emjoules. For example, if 10,000 solar emjoules are required to generate a joule of wood, then the “solar transformity” of that wood is 10,000 solar emjoules per joule of wood. The solar transformity of the sunlight absorbed by the earth is 1.0 by definition.

   Erik focused a lot on the term Transformity (the emergy input per unit of available energy output) and how it has been evaluated for different kind of activities or products. In the mid part of the hierarchy most of the economic production activities took place while more social activities, education, research and law where located at the top of the pyramid. At the bottom more naturally produced materials occurred.

   Finally, Erik showed pieces of his own research where he analyzed the region Jämtland and showed the inputs evaluated and summed to obtain the emergy of a resulting flow or storage. The purpose of such a system diagram is to conduct a critical inventory of processes, storages and flows that are important “drivers” of the system.

Example of emergy flows for the Jämtland region