Page 9 - Low Temperature Energy Systems with Applications of Renewable Energy

Preface xix

lead to uneconomic returns on investment, and the perceived risk on the part of indus-
try investors who may view heat pump technology as new and not sufficiently proven
in commerce, with limited examples of successful applications. This book may help
change these largely uninformed perceptions.
In Chapter 5 we change direction and look at geothermal energy as a source of heat.
Geothermal energy, a renewable resource if properly managed, can be used either for
the generation of electricity or for a great variety of direct heat applications. One of the
authors (DiPippo) has published extensively on the first use, while here we look in
detail at numerous examples of direct heat applications from around the world. Consid-
erable space is devoted to renewable municipal district heating systems, agricultural
uses, recreational applications, and geothermal aquaculture systems, including ones
associated with geothermal electric generation stations. The chapter concludes with
a theoretical presentation of 1- and 2-stage geothermal heat pumps used for heating
purposes, along with several examples showing how the systems perform under a
variety of conditions.
Given that geothermal energy has a dual-purpose nature, Chapter 6 deals with
combining those two purposes, namely, geothermal combined heat and power
(CHP) systems. CHP is a highly efficient means of capturing the available energy,
or exergy, in the geothermal resource. The basic configurations and fundamental ther-
modynamics of CHP systems are presented. The spectrum of direct heat uses is shown
as a function of temperature, but detailed analyses of these cases are not covered here
as they are presented in other chapters. Technical and environmental considerations
determine the best working fluids for CHP plants. Optimum systems are found that
share the heat and power loads appropriately to achieve the best thermodynamic
and economic performance. Both energy and exergy bases are used to assess system
performance. Lastly, two cases studies are described: (1) a municipal district heating
system in Japan where a power plant supplied waste, hot brine to heat water for a
nearby town, and (2) a campus system in the United States that provides both elec-
tricity and heat for all of the buildings including some snow-melting for walkways.
The production of fuels from biological organisms, biofuels, is discussed in Chapter
7 both from a technical and economic viewpoint. A brief summary of the status of bio-
fuel installations around the world provides the context for this chapter, and gives the
reader a glimpse at the state of the art of biofuel facilities. The technological processes
involved in the transformation of organic waste into useable biofuels are described in
detail. The theory is presented along with some typical commercial systems that are
available in the marketplace. We show how heat pumps and heat recuperators can
be used to improve the efficiency of biogas reactors, and present the results of calcu-
lations carried out to illustrate to performance of these systems. All of these topics are
important in light of the possibilities presented by waste agricultural products that may
be used to generate fuels and reduce the demand for conventional, non-renewable
sources.
In Chapter 8 we discuss various hybrid systems involving renewable energy sour-
ces. We begin with solar power systems including large-scale photovoltaic power
stations. Unique systems such as floating photovoltaic systems and co-located solar-
hydroelectric hybrid plants are described. A section covers solar thermal heating