HomeMy WebLinkAboutSolar Wind Consultants Solar Site Survey Report for the Ambler august 2009Solar Wind Consultants
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Solar Site Survey Report
For the Alaska Village Electric Cooperative
Ambler,AK
Report Date:10 August 2009
Prepared by Greg Egan
Reviewed by Bruno Grunau P.E.
Solar Site Survey Report
For the Alaska Village Electric Cooperative
Ambler,AK
Introduction:
Alaska Village Electric Cooperative (AVEC)has requested a Solar Site Survey for their
facility located in the village of Ambler,Alaska.This report is intended to provide power
production estimates for a proposed 50 kW photovoltaic (PV)system as well as solar array
shading and layout considerations.It is based on information gathered during a visit to the
proposed PV system site on May 26,2009.
Using the Solar Pathfinder™(SP)site analysis tool,sunpath diagrams were generated from
digital photos taken at the site.These images were then analyzed using So/ar Pathfinder
Assistant™Version 4.0 (SPA)software.SPA uses TMY3 data sets (see reference 1)
derived from the 1991-2005 National Solar Radiation Data Base (NSRDB)update,which
was developed by the National Renewable Energy Laboratory (NREL)and contains hourlysolarradiationandmeteorologicaldatafor1,454 stations across the country'.In this case
the nearest NREL-published data station is in Selawik,Alaska,a distance of 66 miles from
Ambler.
References:
1."Users Manual for TMY3 Data Sets,”NREL/TP-581-43156 revised May 2008
retrieved 16 June 2009 from the National Renewable Energy Laboratory.
Web Source:http://www.nrel.gov/docs/fy08osti/43156.pdf
Site Survey 1
The first site considered in this report is located across Schwatka Street,southwest of the
existing power plant facility (reference Figure 1).This lot slopes to the northwest and is
covered with a mixture of black spruce and willows.
1 TMyY3 data are Typical Meteorological Year (TMY)hourly values of solar radiation and
meteorological elements derived from the 1961-1990 and 1991-2005 NSRDB.
Digital photos,similar to the one shown in Figure 2,were taken of the SP which were then
uploaded to a computer and analyzed using SPA software.
A sunpath diagram is a circular projection of the sky vault onto a flat diagram used to
determine solar positions and shading effects of landscape features on a solar energy
system.The sunpath diagram has been edited within the SPA software to trace the
landscape features which would cause shading on a PV array.Figure 2 shows a photo of
the SP and a sunpath diagram generated from the same photo,side by side.
Figure 2.Digital image taken of SP at site 1.Image on right is sunpath diagram
generated with SPA software
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Notably,the property being considered was thick with spruce and willow bushes at the
time of the site visit.It was therefore difficult to get a useful SP image that was truly
representative of the site.SP images were also taken from less obstructed areas adjacent
to the site,as well as digital photographs of the surrounding area.Production estimates
were then generated through analysis of these images and estimating the effect the
surrounding landscape would have on a proposed PV array.
Community
Center
Storage Tank (Figure 1)___--{Formatted:Font color:Red
(Figured,=ee ---(Formatted:Font color:Red )
abs
Figure 3.Site 1 as viewed from the top of a fuel tank at the AVEC tank farm.
Accumulation of snow during colder months can severely limit the power produced by solar
electric panels.Fixing the array tilt at 90 degrees (plumb)will keep most of the snow from
accumulating on the panels and adversely affecting output.However a 90-degree tilt is
not the optimum angle for year-round power production.Having the panels mounted on
adjustable racks will allow the tilt angle to be decreased and power generation increased
during the late spring to early fall timeframe.
To accommodate a PV array on this site without inter-row shading becoming an issue it
was determined that one row of rack mounted modules be installed facing south.The
array would consist of 180 Sharp 175 watt modules measuring approximately 160 feet wide
and 18 feet high and would fit within the boundaries of the property (as shown in Figure
1).The relatively narrow east-west dimension of the property would limit the array size
from 50.4 kW to 30.5 kW;therefore all calculations for feasibility on this site were based
on this assumption.
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Site Survey 2
A second site survey was conducted at the old sewage lagoon for the village.The lagoon
is located approximately %mile northwest of the power plant.Refer to Figure 4.The
present lagoon is a few feet deep but is scheduled to be filled in with gravel in the future.
The lagoon site is wide enough east to west that a 50.4 kW array could be installed in a
single long row.
pings copesmenti {Wisi ie
Figure 4.Aerial view of Site 2:Old Sewage Lagoon with proposed 50.4 kW array
Digital photos were taken of the SP which was set up on the northwest bank of the lagoon.
The images were then uploaded to a computer and analyzed using SPA software.Figure 5
shows the sunpath diagram generated for this site.As can be seen in the digital image of
the SP,there are trees that could be removed which would improve this sites solar access.
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Figure 5.Digital image taken of SP at the sewage lagoon site.Image on right is
sunpath diagram generated with SPA software
Site Survey 3
A final site survey was conducted on the grounds of the AVEC Power Plant Facility.
Sufficient space is available for an array of 10.5 kW in the area to the northwest of the
tanks (see Figure 6).The location of the tanks and generator buildings on this property
would cause considerable shading of an array ltocated at this site.
Digital photos were taken of the SP and these images were then uploaded to a computer
and analyzed using SPA software.The sunpath diagrams generated are shown in Figure 7.
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RTP OMFigure6.AVEC Power Plant Facility
Figure 7.Digital image taken of SP at the AVEC Power Plant site.Image on right
is sunpath diagram generated with SPA software
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Power Production Estimate:
The power production estimates for site 1 are based on a system employing one hundred
eighty PV modules rated at 175 watts each.The modules used in these production
estimates consist of monocrystalline cells and are manufactured by Sharp Solar.The
inverters used in this model are manufactured by Fronius and produce 277 vac 3-phasepower.
The production model assumes that (1)the tilt angle of the PV array would be adjusted
twice annually,once in the late spring and again in early fall,and (2)that any trees or
other obstructions to sunlight would be removed as needed to ensure optimum system
performance.
Table 1 shows estimated power production for a 31.5 kW array assuming the array would
be located at site 1 facing south as shown in Figure 4 and that the array tilt angle would
be at 52 degrees May through September and at 90 degrees the remainder of the year.
Table 1.Estimated Production 31.5 kW Array Site 1:Tilt Angle =90°/52°
Average Solar Estimated AC Actual AC
Rad wi Shading Energy (KWH)Energy (KWH)(KWhr/m42)wi Shading wio shading
Azimuth=180°Azimuth=180°Azimuth=1 80°Estimated Fuel
Tilt=90°for snow Tilt=90°for snow Tilt=90°for snow Savings
Tilt=52°for Tilt=52°for Tilt=52°for (Gallons)
summer (May -summer (May -summer (May -(based on 13.5MonthSep)Sep)Sep)kWh /Gallon)
January 0.00 0.00 771.00 0.00
February 0.86 622.56 960.00 46.12
March .3.48 2800.80 2974.00 207.47
April 4.03 2897.05 2898.00 214.60
May 6.05 4309.00 4309.00 319.19
June 6.72 4606.90 4611.00 341.25
July 4.26 2888.76 2889.00 213.98
August 3.79 2710.00 2728.00 200.74
September 3.97 2853.35 3049.00 211.36
October 1.72 1293.80 1971.00 95.84
November 0.00 0.00 721.00 0.00
December 0.00 0.00 151.00 0.00
Totals 24982.22 28032.00 1850.53
The power production estimates for the old sewage lagoon site are based on a system
employing one hundred eighty PV modules rated at 175 watts each.The modules used in
these production estimates consist of monocrystalline cells and are manufactured by Sharp
Solar.The inverters used in this model are manufactured by Fronius and produce 277 vac3-phase power.”
2 Different models and/or brands of equipment may have significantly different operating
efficiencies.Using different equipment could significantly affect system power production.
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The production model assumes that (1)the tilt angle of the PV array would be adjusted
twice annually,once in the late spring and again in early fall,and (2)that any trees or
other obstructions to sunlight would be removed as needed to ensure optimum system
performance.
Table 2 shows estimated power production for a 50.4 kW array assuming the array would
be located facing south as shown in Figure 1 and that the array tilt angle would be at 52
degrees May through September and at 90 degrees the remainder of the year.
Table 2.Estimated production 50.4 kW Array at Sewage Lagoon Site 2:Tilt Angle
=90°/52°
Average Solar AverageSolar Actual AC
Rad wi Shading Radwi Shading Energy (KWH)
(KWhrim'2)(KWhrim'2)wio shading
Azimuth=180°Azimuth=180°Azimuth=180°Estimated Fuel
Tilt=90°for snow Tilt=90°for snow'Tilt=90°forsnow Savings
Tilt=52°for Tilt=52°for Tilt=52°for (Gallons)
summer (May-=summer (May -summer (May -(based on 13.5MonthSep)Sep)Sep)kWh /Gallon)
January 0.07 *101.07 1371.00 7.49
February 1.16 1504.73 1709.00 111.46
March 3.39 4849.00 5285.00 359.19
April 3.87 4980.81 5152.00 368.95
May 5.89 7495.42 7662.00 555.22
June 6.64 8124.76 8194.00 601.83
July 4.10 4985.96 5138.00 369.33
August 3.58 4578.27 4850.00 339.13
September 3.88 4967.00 5422.00 367.93
October 2.15 2883.08 3505.00 213.56
November 0.11 152.95 1284.00 11.33
December 0.00 0.00 268.00 0.00
Totals 44623.05 49840 3305.41
Table 3.Estimated production 10.5 kW Array at Power Plant Site 2:Tilt Angle =
90°/52°
Average Solar Actual AC Actual AC
Rad wi Shading Energy (KWH)Energy (KWH)
(KWhrim42)wi shading wio shading
Azimuth=163°Azimuth=163°Azimuth=163°Estimated FuelTilt=90°for snow =Tilt=90°for snow'Tilt=90°for snow Savings
Tilt=52°for Tilt=52°for Tilt=52°for (Gallons)
summer (May -summer (May -summer (May -(based on 13.5
Month Sep)Sep)Sep)kWh /Gallon)
January 0.01 2.37 245 0.18
February 0.69 157.81 306 11.69
March 3.28 838.93 947.00 62.14
Aprit .3.73 863.53 921.00 63.97
May 5.89 1,363.85 1,372.00 101.03
June 6.48 1,449.73 1,467.00 107.39
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July 4.07 903.68 919.00 66.94
August 3.42 789.25 870.00 58.46
September 3.76 859.85 970.00 63.69
October 1.46 348.09 628 25.78
November 0.03 5.99 230 0.44
December 0 0 49 0.00
Totals 7583.08 8924.00 561.71
The power production estimates for the AVEC power pliant site are based on a system
employing 60 PV modules rated at 175 watts each.The modules used in these production
estimates consist of monocrystalline cells and are manufactured by Sharp Solar.The
inverter used in this model is manufactured by Fronius and produces 277 vac 3-phasepower.
The production model assumes that (1)the tilt angle of the PV array would be adjusted
twice annually,once in the late spring and again in early fall,and (2)that any trees or
other obstructions to sunlight would be removed as needed to ensure optimum system
performance.
Table 3 shows estimated power production for a 10.5 kW array assuming the array would
be located facing south as shown in Figure 6 and that the array tilt angle would be at 52
degrees May through September and at 90 degrees the remainder of the year.
Conclusions:
The first site considered in this report is located directly across Schwatka Street from the
power plant facility.The close proximity of the lot to the power plant would curtail the
need for a long and expensive power line extension.
Shading issues associated with this site are a significant concern.The lot is currently
covered in black spruce and willows;however,these could be removed as needed to
improve solar access.A few solar obstructions nearby would not likely be removed,such
as the community center and the large green storage tank to the south (reference Figure
3).Another shading concern for this site is that the lot slopes to the northeast.This
gradient orientation would increase the effect of inter-row shading if more than one row of
modules were installed.Having one long row of PV modules situated on an east-west axis
as indicated in Figure 1 would be the optimal solution to resolve the inter-row shading
concerns;however the system size would be limited to approximately 31.5 kW.
The second site is located about %4 mile northwest of the power plant at the old sewage
lagoon.This relatively large parcel could easily accommodate enough PV modules for a
50.4 kW array (Figure 4).The land is almost flat and has no significant obstructions to
solar radiation.The perimeter of the site is fenced,providing some level of protection
from vandalism and unauthorized access.
Before a PV array could be installed on this property the lagoon would need to be filled in.
Gravel has already been delivered to Ambler for this purpose.Unfortunately,asbestos
?Different models and/or brands of equipment may have significantly different operating
efficiencies.Using different equipment could significantly affect system power production.
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fibers have been found in the gravel,resulting in a lawsuit being filed.This issue would
need to be resolved before any further progress could be made filling the lagoon.
The old sewage lagoon site has transmission lines available nearby;however,the
conductors are not sized large enough for a 50 kW generator.The cost of upgrading the
lines for such a project may substantially increase the overall project cost and should be
considered before making a final decision about using this site for power generation.
The power plant and tank farm facility was the third site considered.An advantage to this
site is the minimal amount of transmission wiring that would be necessary.This site has a
6 foot security fence along its perimeter which offers some degree of protection from
vandalism or unauthorized access.Unfortunately,the fuel tanks and the generator
buildings would be a source of considerable shading and would substantially limit power
production.The analysis provided in the "Power Production Estimate”section herein
indicates that a solar array installed in this location would yield the lowest energy
production per installed kilowatt of any of the sites considered.
With regard to determining the optimal site for this project,prioritizing the sites with the
highest energy production per installed kilowatt would strike the power plant and tank farm
site from the list of sites to be considered.Prioritizing the sites with the lowest overall
cost would strike the old sewage lagoon site due to uncertainties in power transmission
line upgrade costs and pending lawsuit costs,although this site has the best solar access
and PV production capability.The site directly across Schwatka Street from the power
plant seems to balance high energy production per installed kilowatt with low transmission
costs and overall installation costs,although practical array size limited.If an array were
installed at the Schwatka Street site,care must be taken to insure limited accessibility to
the high voltage DC wiring.Adequate signage as well as security fencing would need to be
addressed at this site.
Foundations for unheated structures on ice rich permanently frozen soils are usually
constructed to ensure that the active layer is contained in a thaw-stable material such as
gravel or that the foad is supported by the frozen soil under the active layer.The
foundation used to support the array should be installed on large quantities of non-frost
susceptible soil such as gravel.Since gravel is not locally available,the shipping costs for
this material would add substantially to overall project cost.The amount of gravel would
be dependent upon the area of the foundation and the depth of the active layer of the soil
that would have to be removed.If a large Triodetic foundation,a stiff foundation designed
to resist twisting and buckling caused by heaving ground,were considered for this site,
further research should be conducted to determine the capabilities and limitations of the
Triodetic foundation.Additionally,ballast material added to the foundation or some sort of
anchoring mechanism would be necessary to keep the solar array from blowing over or
shifting in the event of high winds in the area.
An alternative installation option would be to drive piles into the permafrost at a depth
substantial enough to resist jacking (and creep settlement)and install the array on the
piles.A geotechnical report should be conducted,however,to determine active layer
depth and soil composition before pursuing this option,as the required pile depths depend
on this information.
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