Setting the Stage: The 411 on Energy Basics - Environmental Impacts of Renewable Energy - page 8

s tiRling C yCle H eat e ngine
The Stirling cycle heat engine consists of isothermal compression, isometric heat
addition, isothermal expansion, and isometric heat rejection. It operates by cyclical
compression and expansion of air or other gas, the working fluid, at different tempera-
ture levels such that there is a net conversion of heat energy to mechanical work. Like
a steam engine, the Stirling heat engine's heat flows in and out through the engine
wall. The Stirling engine is noted for its high efficiency (results from heat regenera-
tion), quiet operation, and the ease with which it can use almost any heat source. This
compatibility with renewable energy sources has become increasingly significant as
the price of conventional fuels rises and also in light of concerns such as climate
change and peak oil. An example of this compatibility with renewable energy sources
is evident when Stirling engines are placed at the focus of parabolic mirrors, where
they can convert solar energy to electricity with an efficiency better than that of non-
concentrated photovoltaic cells and as compared to concentrated photovoltaics.

THOUGHT-PROVOKING QUESTIONS
1.1 Is nuclear energy considered to be renewable energy?

1.2 What are the economic ramifications of running out of crude oil? Explain

1.3 Will the crude oil crisis come about gradually or suddenly? Explain

1.4 An economy based on renewable energy will help in our ongoing fight to

reduce pollution. Explain.

1.5 Name 15 products produced by oil that we could get along without.

REFERENCES AND RECOMMENDED READING
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Callen, H.B. (1985). Thermodynamics and an Introduction to Thermostatistics , 2nd ed. New
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CRS. (2006). Chemical Facility Security , CRS Report for Congress. Washington, DC:
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Hinrichs, R.A. and Kleinbach, M. (2006). Energy: Its Use and the Environment , 4th ed.
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