Alternative Energy Systems and Applications
While Alternative Energy Systems and Applications, Second Edition is an ideal textbook/reference for advanced undergraduate and graduate level engineering courses in energy-related subjects, it is also an indispensable professional resource for engineers and technicians working in areas related to the development of alternative/renewable energy systems. B. K. Hodge is Professor Emeritus of Mechanical Engineering at Mississippi State University (MSU) where he continues to be involved in MSU mechanical engineering education and research activities. His research areas include enhanced heat transfer, thermal systems simulation, and energy engineering. He also served as the Director of the MSU Industrial Assessment Center. Prior to retirement, B. K. Hodge held the Tennessee Valley Authority Professorship in Energy Systems and the Environment and was Giles Distinguished Professor of Mechanical Engineering and a Grisham Master Teacher. He has served as Chair of the ASEE Mechanical Engineering Division and as President of the ASEE Southeastern Section. He is a Fellow of the American Society for Engineering Education and the American Society of Mechanical Engineers and an Associate Fellow of the American Institute of Aeronautics and Astronautics.
Alternative Energy Systems and Applications
Energy Usage in the USA and the World
1.1 Energy and Power
A review of the customary units used for energy and power is appropriate to initiate a study of alternative energy sources and applications. Although much of the world uses the SI system (Le Système International d'Unités), the USA, in addition to the SI system, also uses the English Engineering and the British Gravitational systems of units. The unit of energy in the SI system is the newton meter (N m) which is defined as the joule (J). Energy in the English Engineering system is defined as the British thermal unit (Btu), or alternately, the foot-pound force (ft lbf); the conversion factor is . Power is the rate of energy usage or transfer, in joules per second, British thermal units per second, or foot-pound force per second. Power expressed in joules per second is defined as the watt (W). The most frequently used power unit is 1000 W or 1 kW. In the USA, power is sometimes expressed in terms of horsepower (hp), where 1 hp is 550 ft lbf/s or 0.7457 kW. The kilowatt-hour (kW h) is a frequently used unit of energy and represents an energy rate (kilowatts) times a time (hour). The conversion is . Anyone engaged in an energy engineering activity needs to remember the conversion between British thermal units and kilowatt-hours; in most instances is used.
Tester et al. (2012) provide a sampling of power expended for various activities. Some of their results are reproduced as Table 1.1 .
Table 1.1 Power expended for various activities.
Activity Power expended Pumping human heart Household light bulb Human, hard work 0.1 kW Draft horse 1 kW Portable floor heater 1.5 kW Compact automobile 100 kW SUV 160 kW Combustion turbine Large ocean liner Boeing 747 at cruise Coal-fired power plant Niagara Falls hydroelectric plant
The range of power expended is astonishing, about nine orders of magnitude. The entries of Table 1.1 indicate various levels of power expended referenced to everyday experiences and can be used to establish a sense of numeracy for power magnitudes.
1.2 Energy Usage and Standard of Living
An irrefutable fact is that developed countries (e.g., USA, Japan, UK) use more energy per capita than less-developed countries (e.g., Mexico, Indonesia). Figure 1.1 graphically presents the HDI (Human Development Index) as a function of the kilograms of oil equivalent (kgoe) per capita per year. The HDI is a measure of the standard of living, and the kilograms of oil equivalent per capita per year is indicative of the energy consumption. The industrialized nations have HDI values in excess of 0.9, while many of the developing countries' HDI values are dramatically less. The correlation between HDI and kilowatt-hour usage is functionally very strong. However, once a threshold of about 3000 kgoe per capita is reached, further increases in electricity usage do not produce a higher HDI. Iceland has the highest HDI, followed by the USA. Some countries with the higher kilowatt-hour usage have large infrastructure length scales and traditions of abundant energy. One of the main themes from Golemberg and Johansson (2004) is that the only way to increase the HDI in developing nations is to increase their energy usage.