HomeMy WebLinkAboutSusitna Energy Productionyears of stream -Flow data from 1950 to 1932 are available and Project
operation was simulated 'on a monthly basis for the entire historical
period.
3.6.3 Reservoir Data
The relationship of area and volume of reservoirs to the elevation of
the Watana and -Devil Canyon dams is set forth in Exhibits 3.2 and 3.3.
At the Watana Development's normal maximum pool elevation of 2185, the
reservoir surface area is about 38,000 acres, and the gross storage
v.,9tn„n ie 0 F mill inn. Arra-fani a+ +he, nAvaNma ii f'nvnn nnl mAvirmim
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Pool elevation of 1455, the reservoir surface area is about 7,800 acres,
with a gross storage volume of 1.1 million .acre-feet. The .active
storage volumes are 3,700,000 acre-feet for Watana, and 350,000 acre--
feet for Devil Canyon.
3.6.4 Turbine and Generator Data
The installed capacity of the Watana Development is 1020 MW, provided in
six units, each rated at 170 MW. The fifth and sixth units provide no
additional energy production in the early years but are available for
peaking use and reserve to the degree such operation would conform to
stream flow requirements.
The operating characteristics for the Watana and Devil Canyon power -
plants are summarized on Exhibit 3.4 based on the rated net head at each
site. In all cases, generator and transformer efficiencies of 98 and 99
percent, respectively, were used to compute the overall plant effi-
196/174 3-10
ciency. The head loss incurred in flow of water through the intake,
penstocks, and discharge passages of the Watana and Devil Canyon power -
plants is assumed to be 1.5 percent of the gross head.
3.6.5 Reservoir Operation Constraints
During the early years of operation, energy generation from the Susitna
Project would be limited by Railbelt electrical demand. Operation
simulations were made for a wide range of Railbelt system demand levels
(4000-8000 GWh/year) to establish the -relation of system demand to
energy production from the Project.
Analysis of the Project's economics has assumed operation designed to
meet certain energy requirements along with some minimum monthly in --
stream flow requirements for the months of July, August, and September.
These flows were delineated at the mouth of Gold Creek (denoted as "Case
C" in the FERC License Application) are shown in Table 3,3.
_._ , _ - , _t f -__t ,.. �_.___
N raservui r ru i e curve � s a i -i IS�, u.r mun �n iy �arye t rese"ryul r elevai.:lulis
which control reservoir operation to achieve a desired result with
respect to use of a water resource. A preliminary Watana rule curve has
been developed to maximize average energy generation, maintain a high
level of dependable energy and meet environmental requirements as
defined by the "Case C" minimum flows. The Devil Carryon reservoir rule
curve is designed to keep the reservoir as full as possible in all
cases.
196/174 3-11
Table 3.3
POTENTIAL MINIMUM FLOWS AT GOLD CREEK (cfs)
Month
Flow
Month
Flow
October
5000
April
5000
November
5000
May
6000
December
5000
June
6000
January
5000
July
6480
February
5000
August
12000
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3.6.6 Power and Energy Production
Energy production (GW-h) and Project capacity (MW) have been estimated
from the reservoir operation studies described above. The studies
considered the energy demands for the period 1993 through 2020 for the
load forecasts developed in Chapter 2. Exhibit 3.5 sets forth the
annual energy production from the Watana and Devil Canyon developments,
as compared with annual demand figures for the forecast demand.
Exhibit 3.6. summarizes the power and energy production for Watana and
Devil Canyon under the 2020 load forecast. The power and energy esti-
As discussed in the FERC License Application, this flow scenario
was selected as the Project operation flow regime considering both
Project and in -stream flow uses.
** The flow changes by 1000 cfs per day from 6000 on July 25 to 12,000
on August 1 and from 12,000 on September 14 to 6000 on September 21.
196/174 3-12
EXHIBIT 3.6
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