Solar-PV

Comment

Comment by Ingemar Mathiasson on March 17, 2010 at 1:59pm

Hi Don

I am using an Outback FM-60 Mppt,,

It allows me to connect strings of modules with higher Voltage rating
Up to 150 Volts
This saves on the wirering..

There is a small continues draw of a few mA for the controller'

But I have not seen any other adverse effects..

It works very well, however I do not have a direct comparison to PWM..

Also the Enphase Grid inverter I am testing in Kotzebue have a built in MPPT..

Ingemar

Comment by Don Eller on March 17, 2010 at 1:44pm

HI,

Does anyone have any hands on experience with PWM and MPPT solar controllers? Would you share what your experience has been and the pros and cons that you have discovered for each type of controller.

Thanks

Comment by Ingemar Mathiasson on March 12, 2010 at 9:41am

Hi all

does anyone know what kind of panels the PWatts calculator is based on ?
What kind of efficiency of the panels ?

I

Comment by Don Eller on March 11, 2010 at 4:19pm

Hi All,

There is a test being done by the cold climate housing research found http://cchrc.org/solar-power . If you take the 2009 PV production data and compare it to the information calculated by NREL's PV Watts calculator, actual electricity produced is 71% of that calculated by the PV Watts calculator.


http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/Alaska/

Comment by Don Eller on March 10, 2010 at 4:36pm

Hi all,

To follow are the theoritical output of an solar array and the actual measured output of the array. Based on 6 months of data the theoritical output is 30% higher than actual measured output.

What has other peoples experience been? Actual data is critical for making informed energy choices, please collect and share data.

Array consisted of the following 24 SunWise 120 watt panels. 6 sets of 4 panels hooked in series were used (48 VDC). The Morningstar TS-60 was used as the controller. No tracking system. No inverter, everything configured for DC. While the differences seen between measured output and theoritical calculated output could be because of weather, I doubt it.

Good accurate data for solar and wind is critical for making good decisions, please make sure data gets collected and shared when possible.

Station Identification
City: Anchorage
State: Alaska
Latitude: 61.17° N
Longitude: 150.02° W
Elevation: 35 m
PV System Specifications
DC Rating: 2.7 kW
DC to AC Derate Factor: 0.770
AC Rating: 2.0 kW
Array Type: Fixed Tilt
Array Tilt: 61.2°
Array Azimuth: 180.0°
Energy Specifications
Cost of Electricity: 89.0 ¢/kWh

Results

Month
Solar Radiation(kWh/m2/day)
AC Energy (kWh)
Energy Value ($)
Actual production KWh
1 0.83 48 42.72
2 2.16 126 112.14
3 3.77 242 215.38
4 4.35 261 232.29
5 4.88 292 259.88
6 4.74 262 233.18
7 4.50 254 226.06 171.256712
8 3.77 214 190.46 179.0339057
9 3.28 186 165.54 64.17898733
10 1.88 111 98.79 85.58441912
11 1.39 83 73.87 39.69683292
12 0.61 33 29.37 11.28393767



Year 3.02 2112 1879.68

Comment by Don Eller on March 10, 2010 at 4:01pm

Hi just ran the numbers using PV Watts. http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/code/pvwattsv1.cgi The production estimate used for the Noatak water plant closlely follows the expected output. Does anyone have a feel for how actual solar output compares with the calculated output from PV Watts?


Station Identification
City: Kotzebue
State: Alaska
Latitude: 66.87° N
Longitude: 162.63° W
Elevation: 5 m
PV System Specifications
DC Rating: 10.0 kW
DC to AC Derate Factor: 0.819
AC Rating: 8.2 kW
Array Type: 2-Axis Tracking
Array Tilt: N/A
Array Azimuth: N/A
Energy Specifications
Cost of Electricity: 89.0 ¢/kWh

Results

Month, Solar Radiation(kWh/m2/day), AC Energy(kWh), Energy Value($)
1 0.66 187 166.43
2 2.37 617 549.13
3 5.54 1574 1400.86
4 8.51 2253 2005.17
5 8.84 2349 2090.61
6 8.74 2150 1913.50
7 7.25 1810 1610.90
8 4.60 1119 995.91
9 4.08 1002 891.78
10 2.45 628 558.92
11 0.92 235 209.15
12 0.10 27 24.03


Year 4.51 13951 12416.39

Comment by Ingemar Mathiasson on March 10, 2010 at 3:45pm

We will see...

There is definitely a very wide margin in how much solar energy we can get in each location.
The different climate and weather is the big factor from just calculations.

I think the only way to do it somewhat accurately would be to run a small array for 1 year in a specific location, that could benefit for solar.

I have suggested just that for our 11 villages up here, we may be funded for 6pc. 2Kw arrays for 6 of our schools for educational purposes this year.

A suggestion would be to do the same for all High-schools in the State, this will give us some solid data for each community and also benefit the students that needs to study Alternate Energy,,,
The arrays do not need to be very big to quantify the data.
Something simmilar to "winds for schools"..

I am evaluating the "Enphase" Inverters since October last year and am impressed with the performance.

I also started to measure solar radiation in Ambler since October.
So this fall I should have some solid data.

The other issue to look at is that in some villages solar-PV may be the only alternative as wind or Hydro is non-existant..

How is that array in south central configured,, ?
Tracking or not and in 1 or 2 directions..?
What kind of inverter if any ?
What brand of Panels ?

I

Comment by Don Eller on March 10, 2010 at 1:57pm

Hi Ingemar,

I can definately see why there is a difference in our opinion regarding the value of solar energy. If I understand the answer of 1167 KWh correctly, this is the average expected electrical energy produced by the array monthly. So total annual energy produced by the array would be 14000KWh or in terms of avoided commerical electrical costs $12463 annually.

Based on actual production of a solar array in South Central a 2880 watt array is expected to produce 1100KWh annually. If we extrapolate what a 10000 watt array should produce based on the production of a 2880 watt array in South Central Alaska, 3819 KWh of electricity should be produced annually by a 10000 watt array in South Central AK.

So there is a significant difference in the expected annual production of the solar array based on my experience in South Central and the expected array output used in the break even calculation for the Noatak water plant.

Does anyone else out there have some empirical data for expected solar array output? Please supply annual production, array size and array location.


How was the expected output of the array for the Noatak waterplant calculated? Do you happen to have the historical output of the solar array being used to power your home in Ambler? Martin hit on this but the differences in our expected output of the array really point out the need for accurate real data.


What are your thoughts?

Don

Comment by Ingemar Mathiasson on March 10, 2010 at 11:24am

Hi Don

1. Cost of Commercial power @ $ 0.89/Kwh before PCE..

2. Average Consumption 1500 Kwh/month

3. expected averaged out output of solar 1167Kwh
This is a 2 way tracking array with derate factor of 0.819 on the
inverters..

Now I do have the complete calculations, they are actually more complex as there is 2 tiers on cost and PCE..
But I need to send you a spreadsheet in E-mail for that..



Sincerely Ingemar

Sincerely Ingemar

Comment by Don Eller on March 10, 2010 at 10:43am

Hi Ingemar, could you provide the following information for the Noatak waterplant example:

1) Cost of commercial power.
2) Annual consumption of WaterPlant broken down by month.
3) Expected output of 10 KW solar array in Noatak broken down by month.

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