Page 10 - Low Temperature Energy Systems with Applications of Renewable Energy

xx Preface

systems, followed by a detailed presentation of solar-assisted heat pumps for several
applications in which solar energy is used as a topping or bottoming source of heat.
Geothermal and solar energy may be used together in a synergistic manner for both
district heating and electrical power generation. These applications are presented in
technical detail for various arrangements. Geothermal energy can be combined with
non-renewable energy resources, and such systems are also described in this chapter.
The interesting topic of hybrid geothermal-biomass power systems shows effective
ways to combine these two renewable energy sources provided certain conditions
are present. Lastly, the chapter deals with the general analysis of optimum operating
conditions for hybrid fuel-geothermal heat pumps. The method is illustrated with a
case study of a small municipal heat pump system.
The massive amounts of waste industrial heat are examined in Chapter 9. We look
at a variety of industrial processes and plants that release useable amounts of waste
heat in several forms and at different temperatures. Methods for capturing at least
some of that energy are presented. We consider applications where the waste heat re-
covery system is co-located with the source, such as electricity generation, as well as
remote cases, such as district heating systems. In the latter case, heat transfer fluids are
needed and several groups of fluids are discussed. Rankine cycles are the primary
means of converting waste heat to electricity; systems using both steam and organic
working fluids are presented. Natural gas pipelines offer opportunities for waste
heat and energy recovery; these are described in detail with practical examples drawn
from operating plants. Particular attention is given to the highly energy intensive in-
dustries of cement and glass making. The novel supercritical carbon dioxide Brayton
cycle is presented as an effective means of capturing waste heat from moderate tem-
perature sources. The chapter concludes with a discussion of waste-heat driven absorp-
tion chillers and heat pumps.
Throughout the book we provide nearly 150 review questions and over 30 quanti-
tative exercises for the reader to test his/her understanding of the material. Ample ref-
erences are cited to allow the reader to carry out an in-depth study of the topics
presented.
It is the authors hope that this book will draw much-needed attention to low-
temperature energy systems, and show how they can be exploited in ways that will
contribute to the energy needs of humankind in a sustainable and environmentally
friendly manner.