Exergy assessment of future energy transition scenarios with application to Switzerland

Using an exergy based indicator is highly desirable to compare future national energy strategies. A new web- based information platform called energyscope.ch, informing the general public on the Swiss energy transition was presented at ECOS2016. This paper presents a new extension of the approach that we plan to call exergyscope.ch, clearly stating exergy and distinguishing between primary exergy, final exergy and useful exergy. This allows for a graphical interpretation of the exergy efficiency of each conversion step from primary exergy to final exergy, all the way to useful exergy. Different future energy scenarios for Switzerland are compared to illustrate the gain in exergy efficiency between different strategy choices. Monthly variations in exergy supply are considered by using an average reference temperature for each month. The analysis assesses the useful exergy requirement for all energy services including building and transportation. For heating and cooling services, the proposed framework is coherent with the introduction, reported earlier, of an exergy efficiency indicator in a Law on energy. Accordingly the global exergy efficiency for providing a given useful exergy service can be calculated by multiplying the individual exergy efficiency of each conversion steps. The useful industrial thermal exergy is introduced in a simplified manner with an average service temperature.