Raft River 5MW(e) binary geothermal-electric power plant: operation and performance Page: 5 of 8
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but the cooling water pumps were able to supply
only 78 percent of the rated cooling water flow.
This caused a large reduction in power produced by
the plant. The reason for the poor performance of
these pumps was found to be improper installation.
The pump pit in which the cooling water pumps
operated was found to be too shallow to accommodate
the complete pump inlet. The inlets were shortened
and strainers reduced in size and placed on the
bottom of the pit. The pumps were installed at an
inappropriate distance from the back wall and
appreciable vortexing was noted. It is felt that
if the pumps had been installed correctly, no flow
reduction would have resulted.
Cooling Tower. Measurements on the cooling
water leaving the cooling tower indicated that
when the tower fans were operated at full speed,
the temperature was within 2 to 3°F of the manu-
facturer's predicted value. The temperature was
always higher than predicted, however. Because of
problems with the cooling water treatment facility,
the fans were not run on the high speed for many
of the operating conditions, resulting in an
increased condensing temperature and reduced
turbine power for those tests.
Heat Exchangers. The performance of each
heat exchanger was compared at each of 17 different
tests with predicted performance using the
proprietary computer codes of the Heat Transfer
Research, Inc. (HTRI). Only the low temperature
preheater was not analyzed because its overdesign
and F-shell arrangement made it impossible to
obtain accurate enough temperature measurements to
predict its performance. The high temperature
preheater showed performance approximately 40 per-
cent better than with design fouling (as a percent-
age of the total design thermal resistance). The
low pressure boiler performance was approximately
20 percent better than design. The high pressure
boiler and the condenser were each approximately
20 percent worse than design.
The one problem noted with the heat exchangers
was that the boilers each entrained and exhausted
vapor with a 10 to 20 percent moisture content when
operated at the design boiler levels. When the
levels were lowered, the entrainment was reduced to
three to five percent.
Turbine-Generator. The turbine-generator
performed as the manufacturer had predicted when
the performance was penalized one percent in effi-
ciency for each average percent of moisture in the
turbine. No adverse effects were noted with the
turbine as a result of the liquid flow. Slight
deviations in the expected flow were noted, but
they were of the order to be expected and adjust-
ments to the nozzles would have been made if the
system had been run for a prolonged period.
System Performance
ature was 10°F lower than the design temperature
resulting in a decrease in output power of approx-
imately 500kW. This was, however, the highest
temperature obtained during the testing period. A
sunmary of the reduced state point data of Test 1A
is presented in Table 1; the mass flow rates and
energy balances for the boilers, heat exchangers,
and condenser are shown in Table 2. The state
points correspond to points in the system as indi-
cated in Figure 1. These are the best estimates
of the cycle state point data for the test which
was nearest the design point. The test that pro-
duced the maximum power was not used because the
liquid levels in both the high- and low-pressure
boiler were so high that it was not possible to
estimate the amount of moisture that was being
carried from the boilers.
Avail ability-Irreversibility Analysis. The
ideas associated with an availability-irrevers-
ibility analysis allow the performance of the
system to be considered in the perspective of the
thermodynamic ideal and assess the losses in
thermodynamic performance attributable to the
individual components. Figure 3 presents the
results of such a study on the baseline case (Test
1A). If the plant itself is considered to be this
system of interest, there are a number of things
external to the system that are affected by it.
The geofluid leaving the plant has a lower thermo-
dynamic availability than that entering the plant,
creating a decrease in availability of things
external to the plant. The cooling water increases
in availability as it flows through the plant con-
denser. These processes create increases in avail-
ability external to the plant. (The remainder of
the cooling water loop (pumps and cooling tower)
were not included in the system because the state
points in the cooling tower were not known with
Availacility of gaotluid
entering plant
IT 2.1 --
!ZO«--
6 TurtMoe, including
geartxj* and
5 generator —•*
Figure 3. Availability Analysis
State Point Data. Experimental data taken
during the test were used to calculate thermo-
dynamic properties at state points throughout the
system for each test. Test 1A was taken as the
baseline case for the system. The geofluid temper-
sufficient accuracy.) The algebraic sum of all of
the changes in availability external to the system
is equal to the sum of the irreversibilities of the
components within the system. The irreversi-
bilities of each of the components within the
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Bliem, C.J. Jr. Raft River 5MW(e) binary geothermal-electric power plant: operation and performance, article, January 1, 1983; Idaho Falls, Idaho. (https://digital.library.unt.edu/ark:/67531/metadc1091912/m1/5/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.