Jim Shirts was our first customer in the city of Richland Washington. Jim had a quick understanding of solar and did some very extensive research. It was refreshing working with him as he had a great grasp not only on the economics but also the science and applications of solar. Jim agreed to keep a record of his system as I have found over my years in the industry that even with the great satellite information we can utilize, equipment operates differently in different environments. For example we can have some very cold but sunny days that cause panels voltage to raise.
Jim's Report
Hi Eugene,
On my last utility bill, I received a credit of $86.88 (including tax) for power fed back to the grid…yeah!!! I’m attaching an update of production info. I tried to calculate theoretical production based info in “Solar Electricity Handbook”, using orientation, tilt and temperature. The numbers are close to what you estimated, but I couldn’t get exact insolation data for my orientation and tilt. Also, I didn’t finish the shading experiment, based on the first test. Any suggestions on what to do about that? Hope all is well with you. Take care.
Jim
System Design/Installation/Production Details
Front Panels:
Twelve 270 Watt iTEK panels w/Enphase micro-inverters, roof
mounted, facing 50 degrees East of true South, and tilted 72 degrees from
vertical (18 degrees from flat).
Back Panels:
Twenty-one 270 Watt iTEK panels w/Enphase micro-inverters,
roof mounted, facing 130 degrees WNW from true south, and tilted 72 degrees
from vertical (18 degrees from flat).
Three of the panels are affected significantly by shading from a
chimney, one is affected slightly by the chimney and two panels are affected
slightly by shading early in the year by a large shrub.
(For comparison, the optimum fixed, roof-mounted position
would be facing true south and tilted 43.7 degrees from vertical.)
The system was installed in March, 2015 and started
producing power in the afternoon of April 2, 2015, with the installation of the
city meters.
The actual PV panel average
power production, thus far is as follows:
|
Month
|
April
|
May
|
June
|
|
12 Front Panels
|
42.1 kWh
|
50.0 kWh
|
51.6 kWh
|
|
15 Back Panels
|
31.8 kWh
|
41.7 kWh
|
44.0 kWh
|
|
3 Back Panels w/Major Chimney Affect
|
23.7 kWh
|
31.7 kWh
|
32.1 kWh
|
|
1 Back Panel w/Minor Chimney Affect
|
30.9 kWh
|
39.5 kWh
|
40.0 kWh
|
|
2 Back Panels w/Minor Shrub
Affect
|
27.4 kWh
|
41.4 kWh
|
44.6 kWh
|
For comparison, the theoretical calculated PV panel power
production is:
|
Month
|
April
|
May
|
June
|
|
Front Panels
|
45 kWh
|
49 kWh
|
50 kWh
|
|
Back Panels
|
38 kWh
|
41 kWh
|
42 kWh
|
The actual total PV system power production compared to
projected, thus far, is as follows:
|
Month
|
April
|
May
|
June
|
|
System Actual Power Production
|
1140 kWh
|
1440 kWh
|
1503 kWh
|
|
System Estimated Power Prod.*
|
1254 kWh
|
1357 kWh
|
1395 kWh
|
* Production estimate from Now! Solar.
As can be seem from the above, the actual system production
compares favorably with the estimated production from the proposal.
Shading Test:
A test was devised to try to quantify the effects of shading
on PV panel power production. The plan
was to cover one 6 in. x 6 in. cell in one corner of one panel with a square of
white cardboard for one day then compare the production of that panel to an
adjacent panel. Next, two cells would be
covered, the test repeated, and then 3 cells covered. The plan was to start the test before the
panels started producing power and then monitor it for the day.
By ~ 8:45 a.m. of the first day of the test, with one cell
covered (less than 2% of the panel shaded), the test panel was producing only ~
50% of the panel next to it (114W vs. 227W).
This was much more significant than expected and due to this result the
test was discontinued. This clearly
shows that any amount of shading has a significant effect on power
production.
Hi Eugene & Lisa,
Was good seeing you at the BF Fair last week, Lisa. I told you I would provide an update on my system, so here it is:
My July credit from the city was $61.01, bringing the total to $286.16, thus far, not counting saved power. From going hot until the end of June, the state credit due is $1448.64 (4024 kWh generated). The paperwork was filed but I have not received the check from the city yet.
August power production was off as expected, due to the smoke from the wildfires. Attached is my summary to date:
Jim
System Design/Installation/Production Details
Front Panels:
Twelve 270 Watt iTEK panels w/Enphase micro-inverters, roof
mounted, facing 50 degrees East of true South, and tilted 72 degrees from
vertical (18 degrees from flat).
Back Panels:
Twenty-one 270 Watt iTEK panels w/Enphase micro-inverters,
roof mounted, facing 130 degrees WNW from true south, and tilted 72 degrees
from vertical (18 degrees from flat).
Three of the panels are affected significantly by shading from a
chimney, one is affected slightly by the chimney and two panels are affected
slightly by shading early in the year by a large juniper shrub.
(For comparison, the optimum fixed, roof-mounted position
would be facing true south and tilted 43.7 degrees from vertical.)
The system was installed in March, 2015 and started
producing power in the afternoon of April 2, 2015, with the installation of the
city meters.
The actual PV panel average
power production in kWh, thus
far is as follows:
|
Month
|
Apr
|
May
|
Jun
|
Jul
|
Aug*
|
Sep
|
Oct
|
Nov
|
Dec
|
|
12 Front Panels
|
42.1
|
50.0
|
51.6
|
52.5
|
41.7
|
37.0
|
|
|
|
|
15 Back Panels
|
31.8
|
41.7
|
44.0
|
44.0
|
33.2
|
24.4
|
|
|
|
|
3 Back Panels w/Major Chimney Shade
|
23.7
|
31.7
|
32.1
|
31.8
|
25.1
|
18.5
|
|
|
|
|
1 Back Panel w/Minor Chimney Shade
|
30.9
|
39.5
|
40.0
|
40.9
|
32.5
|
16.7
|
|
|
|
|
2 Back Panels w/Minor Shrub
Shade
|
27.4
|
41.4
|
44.6
|
43.7
|
28.5
|
24.9
|
|
|
|
For comparison, the theoretical calculated PV panel power
production in kWh is:
|
Month
|
April
|
May
|
June
|
July
|
Aug*
|
Sept
|
Oct
|
Nov
|
Dec
|
|
Front Panels
|
45
|
49
|
50
|
52
|
50
|
42
|
32
|
19
|
15
|
|
Back Panels
|
38
|
41
|
42
|
44
|
42
|
35
|
27
|
16
|
12
|
The actual total PV system power production in kWh compared to projected, thus
far, is as follows:
|
Month
|
Apr
|
May
|
Jun
|
Jul
|
Aug*
|
Sep
|
Oct
|
Nov
|
Dec
|
|
System Actual Power Production
|
1140
|
1440
|
1503
|
1514
|
1163
|
924
|
|
|
|
|
System Estimated Power Prod.**
|
1254
|
1357
|
1395
|
1487
|
1405
|
1257
|
942
|
499
|
362
|
* August energy production was low due to extensive wildfire
smoke in area for part of the month.
** Production estimate from Now! Solar.
The actual system production compares favorably with the
estimated production in the proposal from Now! Solar.
No comments:
Post a Comment