Overview of the Heat Cycle Research project Page: 1 of 8
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OVERVIEW OF THE HEAT CYCLE RESEARCH PROJECT
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C.J. Bliem and G.L. Mines
Idaho National Engineering Laboratory
Idaho Falls, Idaho
JUN 2 0 1991
The Heat Cycle Research project is developing
the technology base that will permit a much
greater utilization of the moderate-temperature,
liquid-dominated geothermal resources, particu-
larly for the generation of electrical power.
The emphasis in the project has been the improve-
ment of the performance of binary power cycles.
The investigations have been examining concepts
projected to improve the brine utilization by 20%
relative to a "Heber-type" binary plant; these
investigations are nearing completion. Prepara-
tions are currently underway in the project to
conduct field investigations of the condensation
behavior of supersaturated turbine expansions.
These investigations will evaluate whether the
projected additional 8% to 10% improvement in
brine utilization can be realized by allowing
these expansions. Analytical studies of an
"ideal" cycle's performance have shown that the
concepts under project investigation, are
approaching the practical limits of performance
(these limits are imposed by rotating equipment
efficiencies and heat exchanger approach tempera-
tures). Future program efforts will focus on the
problems associated with heat rejection and on
the transfer of the technology being developed to
industry. Geothermal resources are typically
found in the semi-arid regions of the western
United States. In some instances, the lack of an
adequate make-up water supply for a conventional
"wet" cooling system presents a barrier to the
development of the resource or results in the
utilization of a less efficient power cycle. The
project will examine schemes for rejecting heat
which provide a performance similar to the "wet"
systems with decreased make-up water require-
ments, or would allow a lower quality water to be
used. Innovative schemes will also be examined
for areas where the lack of make-up water pro-
hibits the use "wet" systems. Future project
efforts will attempt to intensify the assim-
ilation of the technology base being developed
into industry to assist in the removal of bar-
riers or constraints to the development of a
The objective of the Heat Cycle Research
Project is to develop, or promote the development
of, technology which will result in a more effec-
tive utilization of moderate temperature geother-
mal resources. The emphasis of the program to
date has been directed towards the binary cycle
technology which more effectively utilizes the
energy contained in the liquid-dominated, mod-
erate-temperature hydrothermal resources. The
project is also defining the technology need to
utilize resources having technical or institu-
tional barriers to development.
During the seeping and. ana.lyt.ic.al_ studies in
the initial phases of the program, several cori-'
cepts were identified which showed significant
potential for performance improvements. These
concepts were, and continue to be, the subject of
field investigations conducted by the project
with a small binary plant. These field investi-
gations, which were initiated over 10 years ago
at the Raft River site in southern Idaho, have
been carried out at geothermal facilities in the
Imperial Valley of southern California since the
mid-1980's. The small plant used for these inves-
tigations, referred to as the Heat Cycle Research
Facility (HCRF), is shown schematically in Figure
1. The plant contains most, if not all, of the
components found in a typical binary power plant.
The components are designed to allow the specific
concepts/components under consideration, to be
investigated. The design of the facility allow
for components to be’’ readily changed; its size
allows these changes to be made at reasonable
costs, while maintaining component configurations
similar those that would be found in a commercial
Figure 1. Schematic of the Heat Cycle Research
As indicated, analytical studies1"** con-
ducted projected significant performance gains
could be achieved relative to a reference plant.
For these studies, the conditions for the Heber
binary plant were selected as the reference
plant; it was felt this plant represented the
"state-of-the-technology" at that time (this
assumption appears to continue to be valid).
Relative to the Heber-type plant, the studies
indicated that performance improvements of 20% to
30% (in terms of the net power produced per unit
brine flow rate, or brine effectiveness) were
possible. Utilization of supercritical cycles
with optimized selection of a working fluid mix-
ture and turbine inlet conditions provided the
significant portion (20% of the total 30%) of the
performance improvement. The improvements result
This work was performed under the auspices of the U.S. Department of Enerqy, contract
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Bliem, C.J. & Mines, G.L. Overview of the Heat Cycle Research project, article, January 1, 1991; Idaho Falls, Idaho. (digital.library.unt.edu/ark:/67531/metadc1092871/m1/1/: accessed October 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.