HomeMy WebLinkAboutKingcove Oldharbor Hydro 6 of 13 1982SECTION IV
LARSEN BAY
SUMMARY
INTRODUCTORY NOTE:
Presented in this section is the Summary from Volume D--
Feasibility Study for Larsen Bay Hydroelectric Project.
Included for easy reference are several items from that
report: Exhibit VI-1, photographs of the project area; Figure
VII-3, Projected Monthly Generation, Demand, and Usage; and
selected project drawings which include Plate I, the General
Plan, Plate III, the Penstock Plan, Profile, and Details, and
Plate V, the Powerhouse Plans and Sections. References to
figures, exhibits, and plates in the summary presented here
refer to items in Volume D, the full feasibility report for the
Larsen Bay Hydroelectric Project.
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LARSEN BAY
SUMMARY
A. GENERAL
Several prior studies of alternative means of supplying
Larsen Bay with electrical energy had recommended a hydro-
electric project as the best available source. As a direct
result of these prior studies and recommendations, the Alaska
Power Authority has authorized a feasibility study to
investigate in detail the hydropower potential in the vicinity
of Larsen Bay.
This report summarizes the activities conducted for the
feasibility study. These activities included projections of
energy needs, formulation of a hydroelectric project and an
alternative base case to meet the electrical energy needs of
Larsen Bay, detailed analyses of economic feasibility, and
preparation of an environmental assessment of the effects of
the project.
The results of the study indicate that a 270 kilowatt (kW)
hydroelectric project can be constructed at Larsen Bay, that
the project is considerably more economical than the base case
alternative, and that the environmental effects of the project
are minor.
The total cost of the proposed Larsen Bay hydroelectric
project is $2,821,400 in January 1982 dollars. The project
could be implemented and on-line by January 1, 1985, if a
decision to proceed with the project is made by December
1982. During an average water year, the proposed project would
be capable of supplying more than 85 percent of the electrical
needs and about 14 percent of the space beating needs in the
project area. The equivalent savings in diesel fuel in the
year 2001 would be about 69,000 gallons for direct electrical
demand and 16,000 gallons for space heating.
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B. AREA DESCRIPTION
The village of Larsen Bay is located near the junction of
two fjords, Larsen Bay and Uyak Bay, on the northwest coast of
Kodiak Island. Shelikof Strait, separating Kodiak Island from
the mainland, lies 14 miles to the northwest and the city of
Kodiak lies 60 miles to the east. The selected hydroelectric
power site is on Humpy Creek, a small tributary of Larsen Bay
fjord about one mile south of town. The general project area
and the proposed project site are shown on Plate I of
Appendix A.
C. POWER PLANNING
Power planning for the Larsen Bay project was conducted
using standards set forth by the Alaska Power Authority.
Previously recommended potential hydroelectric sites were
investigated and the project area was surveyed to evaluate
potential new sites. After detailed study, a project was
selected and then compared with a base case plan.
Present energy demands for Larsen Bay for direct electrical
uses and space heating were estimated and future uses in these
categories were projected. The projections were based on
forecasts of increases in the number of customers and increased
usage rates. Population growth and employment, legislation and
other political influences, life style changes, and other
factors ca❑ influence future energy demands but they were not
explicitly treated.
The period of economic evaluation used was 53 years, which
starts in January 1982 and extends for the 50-year life of the
hydroelectric project after the estimated on-line date of
January 1985. The energy demands for Larsen Bay were increased
for 20 years starting in January 1982 and extending through
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December 2001. The demands were the❑ held level over the
remainder of the economic evaluation period.
For the proposed hydroelectric project, it was assumed that
the first priority of use for the energy produced would be the
direct electrical needs of Larsen Bay, and any remaining energy
would be used for space heating.
D. DESCRIPTION OF RECOMMENDED HYDROELECTRIC PROJECT
Hydroelectric power plants transform the energy of falling
water (head) into electrical energy. Generally, a hydroelec-
tric power project consists of a dam to produce the head or to
divert stream flows so that they can be passed through a
turbine -generator system to produce electric power. In the
case of the recommended Larsen Bay Hydroelectric Project, a low
weir will act as a dam to divert water from Humpy Creek through
an inlet structure and into a penstock (conveyance pipe). The
penstock will be 27 inches in diameter and will carry the water
about 2700 feet to the powerhouse, where it will be passed
through the turbine -generator system to produce electric
energy.
The powerhouse will have the capacity to produce 270 kw of
electrical power. A transmissio❑ line will be constructed to
transmit the power generated at the plant to Larsen Bay.
Access to the powerhouse facilities will be provided by
building a short length of new road to link up with an existing
road that extends to an existing and abandoned dam near the
site of the new powerhouse. The transmission line will follow
the alignment of the new access road and the existing road to
Larsen Bay. The general plan and features of the proposed
project are presented on Plates I through VII of Appendix A.
Photographs of the project area are presented in Exhibits VI-1
through VI-4 at the end of Section VI and in the Environmental
Report, Appendix E.
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Under the recommended plan, energy generated by the hydro-
electric plant will have to be supplemented by diesel genera-
tion. Larsen Bay does not currently have a central diesel
generating plant and the plan will therefore require the
construction of diesel facilities for standby and backup
power. The hydroelectric generation will be adequate to meet
the direct electrical needs of Larsen Bay during most of the
year; however, from December through March diesel will be
needed to supplement the hydroelectric generation. A new
electrical distribution system will also be required since none
currently exists.
During an average water year the proposed hydroelectric
project will be capable of supplying more than 90 percent of
the electrical needs of Larsen Bay and approximately 20 percent
of the space heating over the life of the project.
Average annual energy production from the hydroelectric
plant will be 1.09 million kilowatt-hours (kWh) and the average
annual plant factor will be about 46 percent, which means that
the plant is expected to generate about 46 percent of the
energy that it could produce if the turbine -generator unit was
operated continuously at full capacity.
E. BASE CASE PLAN
The base case plan formulated to meet the projected energy
demands of Larsen Bay assumed that the use of individual
existing diesel generating plants would be discontinued and a
new centralized diesel generating plant would be constructed.
Because of apparent economic benefits, it was assumed that the
proposed system would also incorporate waste heat recovery that
would be used for space heating. The possibility of installing
wind generation equipment was also considered, and was found to
be economically viable.
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It was assumed that the diesel system for the 1982 base
case would require about 51,500 gallons of fuel oil per year;
this amount was expected to increase over the next 20 years to
more than 80,000 gallons per year. Waste heat recovery was
expected to displace the use of 17,000 gallons of fuel oil per
year by the year 2001. The wind generators are expected to
displace about 12,000 gallons of oil by 2001.
F. ECONOMIC ANALYSIS
The economic analysis was based on the Alaska Power
Authority criteria that compare the net present worth of the
proposed base case costs to the net present worth of the pro-
posed hydroelectric project costs using specified real price
escalation and discount rates. Net present worth is the
present value of the costs that would be incurred over a
comparable economic evaluation period of 53 years for both
projects.
The present worth of the base case only, that is, diesel
generation, is $7,532,100. If this cost is reduced by the
savings that could be realized from the installation of waste
heat recovery, the present worth is $6,725,100; further
reducing this cost by the benefit obtainable from wind
generation yields a present worth of $6,432,000. All costs
except the cost of the hydroelectric project and its diesel
supplement were considered as adjustments to the base case.
The cost of the space heating credit was added to the base case
because it represents a benefit that would not be realized if
the base case plan was implemented. The next present worth of
the base case after all adjustments is $7,348,600.
For the proposed hydroelectric project, the present worth
of the costs, is $5,941,700. A comparison of this net present
cost with the base case net present costs indicates that the
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recommended hydroelectric project is considerably more
economical than the alternative base case.
An additional measure of project feasibility is the bene-
fit/cost (B/C) ratio. The B/C ratio is the present worth of
the project benefits divided by the net present worth of the
project costs. For this project, the B/C ratio for the base
case only is 1.268. The B/C ratio after adjustment for waste
heat recovery is 1.132; after additional adjustment for wind
generation, the B/C ratio is 1.067; and after all adjustments,
the B/C ratio is 1.237. These B/C ratios indicate that the
proposed hydroelectric project is highly feasible.
G. ENVIRONMENTAL AND SOCIAL EFFECTS
The environmental study results indicate that the effects
of the project will be minor due to the limited scope of the
project activities, the inability of salmon to spawn above the
old diversion dam on Humpy Creek, the abundance of alternative
areas available for trapping, hunting, and general recreation,
and the availability of measures to mitigate potential effects
from the construction and operation of the facilities. Minor
socioeconomic benefits will occur as a result of project
construction and maintenance and cheaper electric rates made
possible by the project. Additional environmental studies do
not appear to be warranted unless regulatory agencies or local
residents express additional concerns.
H. CONCLUSIONS AND RECOMMENDATIONS
The studies conducted for this report indicate that the
proposed 270 kW hydroelectric project is feasible and that the
energy demands of Larsen Bay are sufficient to utilize the
hydroelectric plant's planned capacity. The proposed project
is a more economic means of meeting the area's future electric
needs than the base case diesel alternative. Environmental
effects of the proposed project are minor.
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In view of these findings, it is recommended that actions
be initiated to implement the project.
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