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Old 01-07-09, 08:41 AM   #1
jwxr7
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Default my diy pv set-up

Here are the 4 older solarex panels that I modified to work with a 200 watt grid tie inverter.

The panels started out life on the Oklahomah city library (so I'm told), and were 6 volt 70 watt utility grade polycrystaline pv panels. I traded a little electric scooter for them from a local alternative energy aquaintence. They are aged and probably only max out at around 60 watts. I tested them all in the fall one day, and they all worked within a watt of each other. They happened to put out in the lower 50 watt range that day with that load. I needed to convert them to 12 volts to be compatible with the inverter input voltage and current range. I did this with a little surgery. I split the panel electrically into 2 halves by cutting internal connections thru the silicone potting. Then I put these 2 halves in series to get twice the voltage and half the current as before. It was a success .
So I made a wooden rack and oriented it to true solar south in my field. I did this with a plum stake and observed the shadow at the sun's transit for that day and my location. The rack is also angled at the optimum winter angle for my area.


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Old 01-07-09, 08:54 AM   #2
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Monday, I just finished installing and wiring everything in time to catch sunset on one of the only sunny days we have had . The forecast doesn't look promising anytime soon either. I didn't have my energy monitoring system hooked up yet that day as the sun set, but I did put a current clamp style meter on one of the hot wires and observed a current that was reduced as the sun faded away. So I assume things are working .
For now I rigged up a Kill A Watt energy meter to read one side of the 240v ac line that the inverter uses. I should be able to multiply the watt hour readings by 2 to get a good idea of what the system is producing. A note on the Kill A Watt; it reads the current on the neutral line. Trying to do what I am, that is a problem. The 240 system to the inverter doesn't use the neutral for current carrying, just communication. I had to route one of the hot wires thru the Kill A Watt's neutral side and the neutral thru the other. The Kill A Watt doesn't seem to mind, and seems to be reporting current consistant to my clamp on meter.
One drawback of this monitoring set-up is that it doesn't tell me which direction the power is flowing. The Kill A Watt doesn't know the difference. I do know the stand by power used by the inverter though, so I can figure it out.

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Old 01-07-09, 11:20 AM   #3
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Cool

Good news about the wattmeter being usable as monitor I was wondering if this could be done as such a project is always in my head (to lower as much as possible my constant consumption).

Generally PV panels are loosing around 1% per year. Mine are guaranteed at 80% for 25 years. The fact their outputs are closed is also a good news as this will insure as much power as possible. As their rating is at a normalized condition, they can produce more, but I have no idea about Michigan.

Now you have a few months to build another rack optimized for summer

Denis.
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Old 01-07-09, 12:04 PM   #4
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I think I'm going to change the angle 4 times a year to maximize power. I calculated the angles I will need for spring/fall and summer. My winter is around 66 deg from horizontal, spring/fall will be 40 deg, and summer just under 15 deg. I kept that in mind when I built the rack, so each corner of that triangle (seen from side profile) can pivot to change the angle. Panel angle change can be done either by shortening the rear leg or moving the rear leg bottom connection fore or aft. The non-winter angles I need will require sets of shorter legs. So I'll make up a set of spring/fall ones soon since they recommend changing to that setting on February 27. I'll need a shorter set by april 20th.
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Old 01-08-09, 08:32 AM   #5
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I have a daily production # for yesterday. When I came home from work the Kill A Watt said 40 watt hours, so total production was 80 watt hours @ 230 volts. That was a little surprising since the sun never made an appearance at all, it snowed on and off all day.

Woo Hoo, I made almost a penny of electricity . No, but really, I was happy. Over night the standby loss didn't even register a change on the kill a watt, so that was also cool. Now I just need a sunny day to really make some power.
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Old 01-08-09, 09:06 AM   #6
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Nice small setup! I love the idea of using the small inverters. My big question is what did it take to setup the grid tie inverter? I thought I heard you need to inform and/or have someone from your electric company come out and set something up?
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Old 01-08-09, 01:04 PM   #7
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Pretty sweet set up, . I'm really jealous right now.
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Old 01-08-09, 03:40 PM   #8
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Quote:
Originally Posted by jwxr7 View Post
I have a daily production # for yesterday. When I came home from work the Kill A Watt said 40 watt hours, so total production was 80 watt hours @ 230 volts. That was a little surprising since the sun never made an appearance at all, it snowed on and off all day.

Woo Hoo, I made almost a penny of electricity . No, but really, I was happy. Over night the standby loss didn't even register a change on the kill a watt, so that was also cool. Now I just need a sunny day to really make some power.
My panels were under the snow mostly all day. They made the worst production since 21st Nov. : 322Wh. For 3000Wc installed, this is 0.1Wh/Wc... Of course the inverter switched on lately and it took a long time before producing. I found the production was more stable when the snow cover was even. As soon as the snow cover had holes, the production was varying quickly. When the sun set, there was always some snow on the panels, but as the clouds disappeared during the last hour their production was maximal for today.

My panels are roof integrated and directed to West with an angle of 20 from horizontal. At sunrise they doesn't receive light directly but even in cloudy weather they are producing before receiving direct light.

The angle of your panels is more important so they shouldn't have any snow cover

My averages are :
  • 0.61Wh/Wc for the last 10 days of Nov. 2008
  • 0.59Wh/Wc for Dec.2009
  • 0.39Wh/Wc for the first 8 days of Jan. 2009
Rather bad weather...

Your panels produced 80Wh for 280Wc so 0.3Wh/Wc which is better than mine, but I don't have the choice of orientation (they had to be integrated to the roof) while yours are optimally oriented. Our latitudes seam close, mine is 43.6N.

I know my wattmeter is bad to measure low power (<10W). As my panels were mainly under 100W today, yours may have been under 10W. Between my inverter and the selling counter there is a difference the latter is slower with low power and faster with higher power, which leads to a 7% gain

Denis.
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Earth absorbs 1.8 t CO2/head/yr, while a French generates 6.2 t CO2/yr
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
  • kg saved 06/08-08/09: 1816.9+382.9 (ecodriving / 1420mi not driven) = 2199.8
    To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
    (2.66 kg/l diesel)
  • kg saved by 3kWc photo-voltaic solar panels : 187 kg/yr
    To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
    (59.1 g/kWh)
Radioactive wastes saved by 3kWc photo-voltaic solar panels :
  • Long life (>100,000 years) : 2.85 g/yr (0.9 mg/kWh)
  • Short life (<300 years) : 31.7 g/yr (10.0 mg/kWh)
Based upon "official" French figures...
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Old 01-08-09, 07:07 PM   #9
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I was able to pull 580 whrs out of the sky today. The sun poked out off-and-on between snow showers thru the day. When I came home there wasn't any snow build-up on them, which is cool.

Wow, Denis, you are probably seeing as little of the sun as I am. I can't wait for a good sunny day.
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Old 01-14-09, 10:37 AM   #10
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Here are some production #s;
friday, Jan 9th only made 60 whrs,
saturday made zero,
sunday I cleaned the snow off from sat and recieved enough sun to make 320 whrs,
monday made 400 whrs,
and tuesday made 540 whrs.

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