A method for energy analysis using electricity as basis of evaluation : applied to a Swedish nuclear power plant

Abstract: Presently the world's energy supply consists to a large extent of finite resources. Even when producing energy from “renewable” sources, fossil fuels are consumed indirectly to some extent. The dependency on limited resources motivates the comparison of energy systems with respect to efficiency in resource usage. There exist different methods for analysing energy efficiency, of which three are energy-, exergy- and emergy analysis. These methods take different properties of energy resources into con-sideration. In order to analyse the efficiency of energy systems it is important to consider that some forms of energy are more easily used than other. For example, electricity is more useful than heat. Another example is that wooden chips cannot replace petrol in a vehicle without energy demanding conversion. The usefulness of energy resources is not comprehensively dealt with by existing methods. In this thesis a new methodology for the assessment of energy efficiency in energy supplying systems is developed. Central in the methodology is how useful energy resources are. The use-fulness of a resource is in this work technically determined and defined in terms of how much electricity it can provide within a power plant. Electricity is used as base for the calculations be-cause it is an energy carrier easily convertible into any other form of energy and therefore strongly linked to wealth. The objective of the method is to compare the yield of electricity from an energy system to the potential to electricity production in resources used directly and indirectly by the system. In this thesis the method is applied to a Swedish nuclear power plant. It was found that the nuclear power plant is a very good net provider of electricity equivalents to the society, the return on investment ration being approximately 10.