Is exergy destruction minimization the same thing as energy efficiency maximization?

Abstract

This paper discusses whether the exergy destruction minimization or energy efficiency maximization comes first in resolving the climate emergency problem and provides sustainable solution options regarding the 2nd Law of thermodynamics. It has been shown that low-temperature district energy systems with renewable energy sources and waste heat are effective in minimizing exergy destructions, while energy efficiency has a secondary impact. The research has been based on the Rational Exergy Management Model. The corresponding rational exergy management efficiency was directly related to nearly-avoidable CO2 emissions responsibility with a global magnitude of around 80% of direct emissions in the built environment. One conclusion deduced from such an unrecognized magnitude so far is that nearly-avoidable CO2 emissions may not be ignored anymore to develop new strategies for sustainable decarbonization, while the 1st Law measures have limited remaining capabilities. New equations were developed to show the impact of exergy destructions on total CO2 emissions. Sample results show that a 30 percent-point decrease of exergy destructions comparing to the supplied exergy in thermo-mechanical systems has the potential of reducing total CO2 emissions by 35%. The paper argues that current exergy destruction is around 0.8 of the supply exergy, as an industry average, which gives ample room for improvement using the 2nd Law, while the 1st Law efficiency is already higher, and there is less room available for improvements concerning CO2 emissions. The paper shows that the 1st Law efficiency may be increased by about 0.15 points, which gives a window of opportunity about a 25 percent-point decrease in emissions. The second main conclusion is that nowadays, new decarbonization strategies are needed based on the 2nd Law, which will positively impact when coupled with the current 1st Law measures towards meeting the Paris agreement.