The importance of developing thermal systems that effectively use energy resources such as oil, natural gas, and coal is apparent. Effective use is determined with both the First and Second Laws of thermodynamics. Energy entering a thermal system with fuel, electricity, flowing streams of matter, and so on is accounted for in the products and by-products. Energy cannot be destroyed – a First Law concept. The idea that something can be destroyed is useful. This idea does not apply to energy, however, but to exergy – a Second Law concept. Moreover, it is exergy and not energy that properly gauges the quality (usefulness) of, say, one kilojoule of electricity generated by a power plant versus one kilojoule of energy in the plant cooling water stream. Electricity clearly has the greater quality and, not incidentally, the greater economic value.

Preliminaries

In developed countries worldwide, the effectiveness of using oil, natural gas and coal has markedly improved over the last two decades. Still, use varies even within nations, and there is room for improvement. Compared with some of its principal international trading partners, for example, U.S. industry as a whole has a higher energy resource consumption per unit of output and generates considerably more waste. These realities pose a challenge for maintaining competitiveness in the global marketplace.

For industries where energy is a major contributor to operating costs, an opportunity exists for improving competitiveness through more effective use of energy resources. This is a well known and largely accepted principle today.