Thoughts about future power generation systems and the role of exergy analysis in their development Noam Lior
Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, 297 Towne Building, 220 South 33rd Street, Philadelphia, PA 19104-6315, USA
Abstract In face of the likely doubling of the world population and perhaps tripling of the power demand over the next 50 years, this paper (1) presents some thoughts on the possible ways to meet the power demands under the constraints of increased population and land use while holding the environmental impact to a tolerable one, and (2) outlines the ways exergy analysis may be eﬀectively used in the conception and development of such processes. To eﬀectively develop the innovative power generation systems needed in the 21st century, irreversibility and exergy analysis should be much more focused on the intrinsic process details. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Power generation; Second law analysis; Exergy analysis; Nuclear power; Space power
1. Introduction The expected large rise in power demand during the coming 21st century is accompanied by mounting problems with power plant siting, environmental impact, resource shortages, and increasing shortage of available space for fuel and power generation and distribution. Although industry, often assisted by government, is making gradual progress in addressing these problems, the pace of the progress, when extrapolated into the future, is not likely to meet humanity’s needs. Even worse, if not accelerated, it may lead to irreversible harm to the environment and to the ability of future generations to continue their progress towards improved living conditions.
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0196-8904/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 1 9 6 - 8 9 0 4 ( 0 2 ) 0 0 0 0 7 - 9
N. Lior / Energy Conversion and Management 43 (2002) 1187–1198
The omniferous politician, publisher, and scientist Benjamin Franklin (who, I may add, has also founded the University of Pennsylvania in 1740), a believer in conservation and frugality, has written ‘‘a penny saved is a penny earned’’. In the energy area in general, and in power generation in particular, one could safely say that ‘‘a Joule saved is worth signiﬁcantly more than a Joule earned’’: it takes signiﬁcantly more than 1 J of energy to generate 1 J of power. This is ampliﬁed severalfold when one considers the resources and environmental impact associated with the construction and operation of a power plant. It is clear therefore that the ﬁrst priority in meeting the challenges of the coming century is energy conservation, but not implemented in a way that would deprive large fractions of humanity of basic comforts of life. Indeed, as one of the drafters and signers of the US constitution, Franklin has believed in facilitating people’s ‘‘pursuit of happiness’’ and practiced it himself whenever he could. Such pursuit is made very diﬃcult, or impossible, for a population living under draconic energy conservation measures. Further, improved power generation eﬃciency and reduced emissions, species and energy, are obvious paths that are being taken continuously and should be accelerated further. This may be achieved by gradual improvement of existing processes, and the invention and development of new ones. Finally, humanity may need to look up to space for its future energy needs. Human knowledge and intelligence, accompanied by expertise in many disciplines led by science, engineering, economics, and sociology, must be aggressively employed to solve the foreseen problems. This must be assisted strongly and guided by governments, industries and institutions that have a longer-term commitment to this...