Energy accounting of alternative energy sources

Abstract

An energy accounting study has been made of the five alternative energy resource systems—solar, geothermal, wind, wave and tidal power. Owing to a lack of suitable data, a consistent methodology could not be pursued and a detailed comparison of these five systems with regard to likely energy ratios is not possible at the present time. (The energy ratio is here defined as being the total amount of energy obtained from a given system over its lifetime, divided by the total inputs of energy to that system in order to establish and maintain it in operation throughout its life.) There is a spread of possible energy ratios for each system studied, depending upon the assumptions made but, in each case, a value of about 10:1 is seen as a reasonable possibility for the future. The significance of this 10:1 energy ratio is that it could mean that our primary fossil fuel resources, when used to generate electricity through wind, wave or tidal power systems, would go about 33 times as far as they would if used in the conventional way. In the case of solar and geothermal energy, the savings factor would be somewhat less than 33; it could be somewhere between 6 and 30, depending upon system design, local conditions, etc. Energy pay-back times appear to be short for all the systems studied, the longest being about four-and-a-half years. This exercise has revealed just how much our primary non-renewable fuels could be conserved by using them to operate renewable energy resource systems although economic assessments at the present time might not provide justification for such a policy.