Fundamentals of Renewable Energy Processes, 3rd Edition

Chapter 3

Mechanical Heat Engines

3.1 Heats of Combustion

The driving agent of a heat engine is a temperature differential. A heat engine must have a source and a sink of heat. The heat source may be direct solar radiation, geothermal steam, geothermal water, ocean water heated by the sun, nuclear energy (fission, fusion, or radioactivity), or the combustion of a fuel. In developed countries, over 90% of the energy is derived from combustion of fuels, almost all of which are of fossil origin.

When carbon burns completely in an oxygen atmosphere, the product is carbon dioxide which, under all normal circumstances in this planet, is a gas. However, most fuels contain hydrogen and, thus, when burned, they also produce water. The resulting water may ...