13. Energy Conservation and Efficiency

In a strict sense, the term “energy conservation” is a misnomer. As demonstrated in Chap.​ 3 with the First Law of Thermodynamics, energy is conserved by nature. “Energy conservation” does not require any action by engineers or by the general population. What is usually meant by this colloquial term is the eventual conservation of natural primary energy resources, when we perform tasks that are necessary for the functioning of the human society. The colloquial “energy conservation” may be more scientifically expressed as exergy conservation , minimum exergy destruction or minimum entropy production while the societal tasks are being performed. The use of the exergy concept and exergetic calculations ultimately lead to the minimum consumption of primary energy resources and, finally, to the conservation of natural resources. While most of the other chapters in this book pertain to the supply side of the energy equation, conservation and improved efficiency are directly related to the demand side. By “conserving energy” and forgoing the use of a fraction of primary energy sources for the performance of societal tasks, the human society demands less primary sources that supply the global energy demand. As a result, less primary energy is demanded and consumed and the natural resources that supply this energy are conserved. In this chapter we distinguish between conservation and higher efficiency, we apply the concept of exergy in order to perform tasks with the minimum possible exergy destruction and we present several examples of methods that lead to the lesser consumption of natural resources in the areas of transportation and comfort in buildings. These methods include the use of fluorescent or LED devices for lighting, geothermal heat pumps for heating and air-conditioning, evaporative cooling, and electric cars.