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Reference Only
(Note: This preliminary design did lead to a real project that is now in operation) BWC
Preliminary Design and Budget
Project:
FAA Chandalar Lake Hybrid System
1.
Wind Resources: The
location and the altitude (442 m) correspond to a Class 1, > 4.4 m/s at a
height of 10 m, wind zone according to the US-DOE World Wind Atlas. However, the
DOE data for this area of Alaska is based on roof mounted anemometers and is
conservative. The DOE report
states: “The map analyses represent the lower limits of the wind power
resource for exposed areas”. Therefore,
we have assumed that the Chandalar Lake site resource is 4.8 m/s (10.8 mph) at a
height of 10 meters. For the
average monthly wind speeds we have scaled data from an earlier project at Ft.
Greely, which in turn, was based on NCDC data.
2.
Solar Resources Solar
resource data from Solarex and PVCAD were combined to establish monthly
estimates of average daily insolation. The
annual average was estimated at 3.4 kWh/m2.
The summer resource is usable, but the winter resources are extremely
low.
3.
Wind Turbine and Solar Array Performance Wind
turbine performance predictions are based on the battery-charging version of the
BWC EXCEL wind turbine, which has a peak output of 7-8 kW.
The modeling was done with WindCAD; a printout is attached.
Please remember that the daily energy predictions are for DC kWh, not AC
kWh, so the losses from storage and power conversion (DC/AC inverter) must be
factored in before comparing them to the load or the diesel generation. The
wind turbine performance predictions assume 18 meter towers, a Weibull K = 2, an
altitude of 300 meters, a wind shear exponent of 0.143, and 5% losses due to
turbulence. Predicted average daily
energy production varies from 17 DC kWh in July to 50 DC kWh in December. Solar
array performance was modeled for an arbitrary 1 kW system using first-order
(non-temperature compensated) efficiency estimates.
The resulting predicted average daily outputs for the 1 kW array varied
from 0.1 kWh in December to 5.8 kWh in May. The
wind and solar resources have good seasonal complementariness.
The wind peaks in the winter and the solar peaks in the summer.
However, in general, the wind resources are predicted to be better than
the solar resources. 4.
Load The
load is a constant 1,520 W AC communications load and a seasonal heating load,
which has been calculated from temperature data.
Both NDB and heating loads have been converted to average daily demand by
month. All loads are assumed to be
120/240 VAC, 60 Hz, 1-phase. 5.
Sizing for Wind/Solar/Diesel Alternatives Figure
A shows the monthly performance spreadsheet used to evaluate the different
hybrid system possibilities. The
model accounts for the DC subsystem losses for storage, power conversion, and
customary deratings and allows the wind and solar subsystem sizes to be varied
to evaluate the effect of these changes on overall system performance. Due to the size of the load the model uses unit sizes of 7.5
kW for the wind turbine (based on the BWC Excel-R) and 1 kW for the
photovoltaics. Figure
A shows the basic performance for a
7.5 kW wind turbine and a 1 kW PV array. The
model predicts that this system would provide ~ 44% of the site’s annual
energy (see Load Coverage, Annual Ave.). The
remaining ~ 56% of the energy would be supplied by the back-up diesel(s). Generally,
the least cost system will provide ~ 75% of the sites annual energy from
renewables and ~ 25% from the diesel. So,
these targets are generally applied. When
looking at the renewable energy alternatives we like to compare only the
renewable energy subsystem costs. For
wind these include the wind turbine(s), tower(s), tower wiring, charge
regulator(s), and typical installation costs.
For solar these include the solar modules, array structures, wiring,
charge regulator(s), and typical installation costs.
The common energy storage, energy conversion, and systems controls costs
are excluded because they will be necessary regardless of the chosen renewable
energy generation equipment. Figure
B shows the least cost all PV system.
An 14 kW PV array would provide ~ 58% of the annual energy at a subsystem
cost (excluding the balance of systems: batteries, inverter, DC source center,
etc) of ~ $126,000 Figure
C shows the least cost all wind
system. A 15 kW (two Excel-R’s)
wind component would provide ~ 78% of the annual energy at a subsystem cost
(excluding the balance of systems: batteries, inverter, DC source center, etc)
of ~ $70,000. Figure
D shows the least cost wind/solar
hybrid capable of supplying a higher percentage of the sites’ power on an
average basis. The sizing is
determined by minimizing the excess production during the high resource months.
This system would have 15 kW of wind and 5 kW of PV and would provide ~
92% of the annual energy at a combined subsystem cost of ~ $115,000. We
recommend the system shown in Figure C: 15 kW of wind, no solar (click
here to see what system the customer, the FAA, decided upon and installed. Use
the "back" feature of your browser to return to this page) 6. Preliminary Design and
Budget As
shown in the attached one-line electrical schematic, BWC is recommending a
system consisting of the following major elements: • 15 kW wind turbine, with 18 m guyed tower •
400A, 48 VDC DC Source Center •
100 kWh battery bank • 5.5 kW 120 VAC, 60 Hz, 1Ř inverter (with diesels control and reverse-mode battery charging) •
10 kW Diesel Generator The
budgetary estimate for the hybrid system is as follows:
Equipment and Materials
Wind Turbines and Towers US$
51,000
Batteries (sealed)
19,000
Inverter / Charger System
4,000
DC Source Center
1,500
Diesel Generator
16,000
Wiring Materials, etc.
3,000
Special Tooling & Spares
1,500
Subtotal:
$ 96,000
Other Costs
Shipping
$ 5,000
Equipment Building & Civil Works
15,000
Misc. Material, Supplies, & Services
5,000
Installation, Commissioning, & Training
12,000
Subtotal
$ 37,000
Total:
US$ 133,000 This includes the cost of a BWC supervisor for the installation, commissioning, and training. (Note: We underestimated the installation costs because we assumed the site was accessible by road and we didn't factor in permafrost. In actual fact, the site was accessible only by air and permafrost was a significant problem. Fortunately, the FAA's construction company was able to construct more accurate budgets) |
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