HomeMy WebLinkAboutAmbler Solar Energy Project Site Survey Report - Aug 2009 - REF Grant 2195412915 30`" Avenue
Suite 229
Fairbanks, AK 99701
For t/le- Alaska L/i/laae ElectriC LCOoperative
Arnblet, AIK
Report Date: 10 August 2009
Prepared by Greg Egan
Reviewed by Bruno Grunau P.E.
For he A;'�-,Na Volace-, f-. Coo.)era, tive
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 Solar 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 (NREQ and contains hourly
solar radiation ;;nri mAtpnmionirAl data for 1,454 stations across the countrxil, in this rase
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:/Iwww.n,-el,_govldocsIfA,08osti,/43156.1)d
Site Survey I
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 TMY3 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 SPand 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
IM
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.
Accumulation of snow during colder months can severely limit the power produced by solar
electr|c nane|o. Fixing the array tilt at 90 degrees (plumb) will keep most of the snow from
accumulating onthc panels and adversely affecting output, However a 9G'degreetilt 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 ooearly fall Umeframe.
To accommodate a rVarray on this site withoutinter,mwshadiny becoming an issue it
was determined that one row of rack mounted modules be installed facing south. The
array would consist of 180Sharp 175 watt modules measuring approximately z60feet wide
and 18 feet high and would fit within the boundaries of the property (as shown in Figure
z). The relatively narrow east -west dimension of the property would limit the onay $zr
from 50.* kW to 30.5 kw/ therefore all calculations for feasibility un this site were based
on this assumption.
RM
The lagoon site is wide enough east to west that a 50.4 kW array could be installed in a
single long ro.,
Digital photos were taken of the SPwhIch 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.
W
Figure S. Digital image taken of SP at the sewage lagoon site. Image on right is
-7-unpath diagram generated with SPA software
A final site survey was conducted on the grounds ofthe AvEC Power Plant Facility.
Sufficient space isavailable for anarray of18.5Nwinthe area tothe northwest of the
tanks (see Figure §). The location of the tanks and generator buildings on this property
vmv|d cause considerable shading of an array |mauad at this site.
Digital photos were taken of the Spand these images were then uploaded to a computer
and analyzed using SPA software. The ounpath diagrams generated are shown in Figure r.
Figure 7. Digital image taken of SP at the AVEC Power Plant site. Image on right
is sunpath diagram generated with SPA software
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-phase
power '2
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 = 900/520
Average Solar Estimated AC Actual AC
Rad w/ Shading Energy (KWH) Energy (KWH)
(KWhr/m^2) w/ Shading w/o shading
Azimuth=180' Azimuth=180' Azimuth=180' 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 13.5
Month Sep) 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 vac
3-phase power.2
4 Different models and1lor brands of equipmentmay have sigaiticandi, difflerent operating
eftkaiendes. using different equipment could significantly affect system porter production.
IN
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 I 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 Anglit,
= 90'/52'
Average Solar
Average Solar
Actual AC
Red wl Shading
Rad w/ Shading
Energy (KWH)
(KWhrim-2)
(KWhrim-2)
w/o shading
Azimuth=180'
Azimuth=180'
A7imuth=180'
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 13.5
Month
Sep)
Sep)
Sep)
WWh iGalion)
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
188
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.S kW Array at Power Plant Site 2- Tilt Angle
90-/52-
Average Solar
Red wl Shading
(KWhrImA2)
Azimuth=163'
Tilt=90' for snow
Tilt=52' for
summer (May -
Month
Sep)
January
0.01
February
0.69
March
3.28
April
173
May
5.89
June
6.48
Actual AC
Actual AC
Energy (KWH)
Energy (KWH)
w/ shading
w/o shading
Azimuth=163'
Azimuth=163'
Estimated Fuel
Tilt=90' for snow
Tilt=90' for snow
Savings
Tilt=52' for
Tiit=52* for
(Gallons)
summer (May -
summer (May -
(based on 13.5
Sep)
Sep)
kWh /Gallon)
2.37
245
0,18
157.81
306
11.69
838,93
94T00
62.14
863.53
921.00
63.97
1,363.85
1,372.00
101.03
1,449.73
1,467.00
107.39
10
July
4.07
e03�6
mmm
66.94
August
3.42
789.25
870.00
58.46
September
3.76
859.85
970.00
63,69
October
1.*6
348,09
628
25.78
November
0.03
5.99
230
0.44
December
o
0
*o
0.00
Totals
7583.08
.
ee2+u0
56171
The power production estimates for the xvEC power plant site are based onasystem
enploying6o pvmodules rated mt z75watts each. The modules used in these production
estimates consist urmnnocrystaiiine cells and are manufactured bySharp Solar, The
inverter used in this model is manufactured by pmn|usand produces o77vac 3-phase
power.'
The production model assumes that (z)the tilt angle ofthe pvarray would be adjusted
twice annually, once in the late spring and again in early fall, and (2) that any trees m
other obstructions tn sunlight would be removed as needed to ensure optimum system
Table 3shows estimated power production for a zO.5Nwarray assuminythe array would
be located facing south as shown in Figure 5 and that the array tilt angle would be at 52
degrees May uhmogx September and atgO degrees the remainder nfthe year.
The first site considered inthis report |slocated directly across Schwatka Street from the
power plant facility. The close proximity ofthe lot »othe power plant would curtail the
need for 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. 4few 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 isthat the lot slopes to ,he northeast. This
gradient orientation would |mc^eamc the effect o[inter-row shading if more than one row of
modules were installed. Having one long row ofPvmodules situated nn aneast-west axis
as indicated in Figure z would bathe optimal solution to resolve the inter -row shading
concerns; however the system size would be limited ooapproximately 31.5 kw.
The second site is located about 1/4 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 apvarray could beinstalled on this property the lagoon would need mbe filled in
Gravel has already been delivered tnAmbler for this purpose. Unfortunately, asbestos
2Different v�,-Is andMor brands of equipment may.have significantly mffeFentoperating
efflciende5 Us ngdifferent equipment could significantly affect system power production
Im
fibers have been found inthe gravel, resulting mmlawsuit 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 a50Nmgenerator. The cost olupgrading 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 oftransmission wiring that would be necessary. This site has a
6foot security fence along its perimeter which offers some degree nrprotection from
vandalism orunauthorized 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 asolar array installed mthis 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 Us of sites to be oons|deped, Prioritizing the sites with the lowest overall
cost would strike the old sewage lagoon site due m uncertainties in power transmission
line upgrade costs and pending lawsuit costs, although this site has the best solar access
and PVproduction capability. The site directly across 5chwatua 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 a,the schwatua Street site, care must hetaken ,o insure limited accessibility ,o
the high voltage DC wiring. Adequate signagsaswell assecurity 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 orthat the load |ssupported 8ythe frozen soil under the active layer. The
foundation used to support the array should be installed on large quantities nrnon-frost
susceptible soil such asgravel. Since gravel ianot locally available, the shipping costs for
this material would add substantially ,o overall project cost. The amount ofgravel 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 |argeTriodeUc foundat|nn, 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
TriodetirhnundaUun. Addmona||v, ballast material added to the foundation or some sort of
anchoring mechanism would be necessary to keep the solar array from b|nwmm over or
shifting in the event ufhigh winds inthe area.
Analternative installation option would betodrive piles into the permafrost atadepth
substantial enough to resist jacking (and creep settlement) and install the array on the
piles. xgemechnica|report should be conducted, however. mdetermine active layer
depth and soil composition before pursuing this option, asthe required pile depths depend
on this information.
N