HomeMy WebLinkAboutUtility-Scale Railbelt Wind Final Design and Permitting Project Little Mount Susitna Wind Resource Assessment - Dec 2022 - REF Grant 7015021Little Mount Susitna Wind Resource Assessment
Wind energy production is affected by a number of different factors such as the site-specific
wind resource, the inherent variability in the weather and climate, turbine design and
performance characteristics, wind farm layout, various losses, as well as operational and
maintenance approaches.
Alaska Renewables is using a multi-pronged and industry standard approach to characterize
and evaluate the wind resource at Little Mount Susitna. This analysis is used for the
assessment of project economics and the evaluation and optimization of its integration with the
existing Railbelt system. The wind resources at the site were found to be excellent and will
support high capacity factors and economic renewable energy generation.
Meteorological Tower Campaign
In October 2022, Alaska Renewables successfully installed the first meteorological tower on
selection, provide an observational basis for turbine layout optimization and wake loss
modeling, and estimate the net energy production that will result from the project.
Figure 1. Little Mt Susitna meteorological tower #1 (60m) after commissioning on Oct. 12, 2022.
The tower is located near the center of the broad Little Mount Susitna plateau at an elevation of
830 m above sea level. The tower itself is an NRG Super 60m XHD talltower, specifically
designed and selected for its ability to withstand heavy wind and ice loading that may be
experienced at sites in Alaska.
The tower is equipped with six anemometers to measure wind speed in duplicate at three
different heights above ground. Two wind vanes, two temperature sensors, one barometric
pressure sensor and one relative humidity sensor are also present. Statistical data from all
sensors is logged at 10 minute intervals and high frequency 1Hz sample data is also obtained
from three of the sensors to better characterize the potential ramp rates in power output of the
future wind project.
The initial data from the site provide preliminary confirmation that Little Mount Susitna could
support a successful wind energy project. General characteristics are illustrated in Figures 2-3.
Figure 2.Preliminary Little Mount Susitna time series of wind speed from the anemometer at
59m above the ground. Hub height (98m) wind speeds would be slightly faster than those
reported here.
Figure 3.Preliminary wind speed frequency histogram and wind rose from the Little Mt Susitna
meteorological tower observations.
Wind Resource Modeling
A 200m resolution wind resource grid based on downscaled climate and weather models was
obtained from UL. This wind resource grid provides wind speeds, directions, and their
frequencies across the entire Little Mount Susitna Wind Energy Site. This resource grid was
roads, and electrical collector and transmission lines. The resulting layouts are unique for each
project capacity because the software tool attempts to maximize energy production while
minimizing turbine wake loss effects and capital costs such as road and cable lengths. Once
the project layout and cost of energy was optimized, the wind resource grid was used to
calculate the net capacity factors and net energy production from each individual turbine while
accounting for wake effects and other losses. The results are presented in
Little_Mount_Susitna_standard_energy_capture_report.xlsx
In addition to the climatological wind resource grid, we also analyzed an hourly, 21-year long
historical (2000-2020) wind speed time series for the Little Mount Susitna site in order to
generate a wind generation time series and quantify the expected monthly and interannual
variability of expected wind energy production from the site. This ERA5 climate and weather
reanalysis data product combines model data with historical weather observations from across
the world into a globally complete and consistent dataset using the laws of physics. To account
for these terrain effects, we scaled up the wind speed time series data to the average wind
speeds obtained from the high resolution terrain-resolving wind resource grid from UL
(described above). This is the source of the
Figure 4 . Optimized Little Mount Susitna project layout for a 149.6MW project size. Our
modeling optimizes turbine locations and supporting infrastructure alignments in order to
minimize the cost of energy for the project. The modeling takes into account a wide range of
factors including but not limited to the spatial distribution of the wind resource (mean wind
speeds are indicated by the underlying colors in the figure above), wake losses induced by
other turbines, and the total cost of roads, collector, and transmission system. Shown are the
turbine rotor areas (points), minimum turbine offsets (ovals), access road, transmission lines
(red dotted lines), substation (red square) and collector system routing (red lines).
Table 1.Little Mount Susitna average wind speeds at turbines, net capacity factors, turbine
array wake losses, and annual net energy production estimates for each of the proposed project
capacities and their associated layouts. The net capacity factor and net annual energy
production estimates account for the modeled wake losses for each of the different project
layouts as well as the other loss factors specified in
Little_Mount_Susitna_standard_energy_capture_report.xlsx.
Site
Capacity
with GE 3.4-
140 (MW)
Mean free
wind speed at
turbines (m/s)
Net Capacity
Factor (%)
Array
Efficiency %
Total
Losses
Net Energy
Production
(GWh/yr)
Little Mt
Susitna 275 7.20 35.71 91.8 21.73% 860.4
225 7.30 36.85 93.1 20.65% 726.3
150 7.40 38.12 94.9 19.14% 500.9