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 :thumbup:.
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.

http://ecorenovator.org/forum/attach...panelmount.jpg

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.

Cool :cool:

Good news about the wattmeter being usable as monitor :thumbup: 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.

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.

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 :D. 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.

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?

Pretty sweet set up, :). I'm really jealous right now.

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 43.6°N.

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.

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.

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.

So you're averaging about 1/4 kWh per day. Not too bad for such a small setup. Do you know how much you use per day on average?

I'm embarassed to say that I don't know exactly how much we average :o. I can figure it out when I get home and look at my energy bills. I'm guessing around 26kwhrs/day in the dead of winter. Closer to 10kwhrs/day in the best of weather. I do know that it is much higher (2-3x) in the winter due to electric space heating. Fall and spring are way low and summers are pretty low unless we are hit with major heat and humidity that calls for heavy window AC use(that sounds nice right now as we are in the single digits F) .

:thumbup: 26kWh/day is very little with such a low external temperature.
How much square feet do you heat ?

For 900 sq ft we are using 17kWh/day (12.5 peak hours, 4.5 off peak) in addition to summer consumption (no AC), ie +85%, but our single digit temperatures are in °C, so 32-48°F.

We are currently producing per week what we are consuming in one day for heating... :( In summer, we should produce 6 times more, ie per day the 3/4 of what we'll consume per day (too much 24x7...), but the instantaneous production should be up to 6-7 times the instantaneous consumption :cool:.

With optimized orientation and angle from horizontal, you should be able to have an average production of 4-5Wh/Wc/day, ie 40kWh/month.

Do you have an idea about your minimal instantaneous consumption in summer ?
With your low consumption it may be lower than your instantaneous production : you'll have to switch on the AC more ;)

Denis.

I forgot to check my last bill, but I wouldn't be surprised if were are using more than that at the moment. It's -14F air temp right now :eek:. We heat 2500 sqft with a combo of propane, wood and electric.

In the summer there are times when the fridge isn't running when the instantaneous consumption should approach zero.

4 panels swapped for a scooter? That's a nice deal.

I would recommend staking the corners of your array though. You'll get a storm blowing through there at some point that'll threaten to tip those puppies over. It'd be a shame to break 'em.

That would literally and figuratively blow :(.
The photo doesn't show it, but I used some of those spiral dog stakes at each corner. Won't be enough in the spring when the ground is mush but that's all I could get in the frozen ground for now. My brother gave me a mobile home anchor (looks like an earth auger thing) that I'll put in as soon as the ground allows. Until then I could add more cement blocks at the corners to be safe.

Woo! Just checking. :)

I've already broken one panel - a small cheap grade 1 amp 12v battery trickler. I had leaned it against the side of the garage while I was charging a battery, and a gust pushed it over. Only 12 inches tall, and it still broke when it tipped and smacked the ground.

That's an ecobummer Metro:(.


I remembered to check my last three electric bills, and from mid Oct thru mid Nov we averaged 19.1kwhrs/ day. From mid Nov to mid Dec we averaged 26.9kwhrs/day, and from then to now we averaged a whopping 32.8kwhrs/day:eek:. It's been unusually cold lately though.

I managed to grab 560whrs today too :).

560 is good. Cold & sunny, eh?

But it's sobering to realize how small a fraction of total power usage it is.

I think the general public vastly overestimates the power production capabilities of solar, if the number of people who suggest I power the electric car with PV is any indication. They need to see a thread like this to get a better idea.

Some of the panels I have in my setup are from the early 80s and they still generate about 90 of their rated output. I have my panels mounted on a pole so I turn them around several times a day to face the sun. this helps with a battery setup because you can get charging for a longer time rather than higher amps for a short time period. I also have to scrape/brush the snow off them (sometimes several times a day).
-James

I need to check mine for snow more often.

I've thought about using the pole mount for my big old satellite dish. I could reuse the linear actuator and come up with some sort of active tracking system. The pole is already in the same area as my pv set-up.

On friday I pulled over 1200whrs from the sun :cool:. That's over 6 hours of full inverter output. I need more days like that :).

Wow very nice. How many times did you adjust it on Friday?

I don't adjust mine other than seasonally, so that was a fixed rack production #.

Very true. On a good sunny day you might offset the power used by accessories :D. Plus these panels are fairly heavy and large, so it would be impractical to have on a moving car. They could mount on a full size truck over the bed or on a big stationwagon's roof, but not a metro :).

Yes, people don't really think about how much energy is used to move a car down the road. You'd have to be a rich man to do it with solar power. Lights, stereo, and computer use very little by comparison.

here's a summary of the last 7 days production from january 14th thru the 20th;

wed, 40 whrs
thurs, 560 whrs
friday, 1280 whrs
sat, 140 whrs
sun, 440 whrs
mon, 1060 whrs
tues, 1300 whrs

Those numbers are looking pretty darn good. Almost 700 Wh a day from such a small setup!

OK gang- does anyone know of a pv for newbies resource? Tons of ignorance needing to be modified to slight knowledge. Thx

If I were you, I'd start here:

Solar Photovoltaic Projects

Thanks Daox, exactly what I needed.

Here is my daily consumption (including hot water and heating) vs my weekly production in kWh for the last 8 weeks : http://ecorenovator.org/forum/attach...8&d=1232653165

• OPH = Off Peak Hours (10:30PM - 06:30AM) : 12.98 kWh/night
• PH = Peak Hours (06:30AM - 10:30PM) : 27.63 kWh/day
• day = OPH + PH : 40.61 kWh/day
• PV/week : 12.79 kWh/week = 1.83 kWh/day

ie I'm currently consuming by night what I'm producing in one week... Happily in summer I'll produce daily around 75% of my daily consumption :cool:

Remarks :

• This production is done with 23 m² (~207 sq-ft), which correspond to 3kWc. How much sq-ft can you put on the roof of a car ?
• My PV system is static (roof integrated) so its orientation isn't optimized as it would be on the roof of a car,
• There is a correlation between consumption and production. During 1st week, the heating system was misconfigured... Week 7 was the coldest. Weeks 5 (Xmas week, far from home) & 8 were warmer and sunnier that previous ones.

Denis.

Here is a comparaison between an unoptimized installation (mine toward to West with a fixed horizontal angle of 20° - roof integration) and an optimized one (jwxr7's toward to South with a horizontal angle optimized for winter).

day	groar	kWh/Wc	jwxr7	kWh/Wc
wed	3504	1.17	40	0.14
thurs	3305	1.1	560	2
friday	4016	1.34	1280	4.57
sat	2651	0.88	140	0.5
sun	1471	0.49	440	1.57
mon	373	0.12	1060	3.79
tues	3649	1.22	1300	4.64
average	2709.86	0.9	688.57	2.46

We are not living in the same place (so different amount of clouds), but roughly at the same latitude. jwxr7's system is 280Wc while mine is 3000Wc. To compared I divided the Wh by Wc. jwxr7's system is currently 2.46/0.9=2.72 times more efficient.

1st law for a DIY PV : build the installation to be able to optimize orientation and horizontal angle :cool:

Happily in winter I'm loosing 40% while in summer I'll loose only a few%. My system will also pay for itself thanks to incentives and selling rate.

Denis.

Is "Wc" (in kWh/Wc) a measurement of the capacity of the panel in Watts? Its peak theoretical output in ideal conditions & perfect alignment?

Oops, Wc may be the French term ("Watt Crête"), which can be translated by "Peak Watt" but I don't know if this is the English term. This is the output of the panel at normalized conditions: iirc 20°C and 1000W/m², imho the alignment is certainly normalized too but I can't remember about this detail.

Denis.

Stumbled across this file yesterday doing some research; should help newbies like myself-
EERE PV Guide35297solar.pdf
Hope my cut/paste worked.......

From Watt-peak - Wikipedia, the free encyclopedia :
But other parameters are also important :
Denis.

Thanks for clearing that up, Denis.

I was wondering what Wc meant too. Thanks for asking Darin.

One thing that will limit my production on sunnier days is my inverter. It maxes out at 200w while my panels could potentially be making 240-280 watts. This was the best grid tied scenerio I could come up with using my old panels though.

One sunny day last weekend I was able to witness what was probably the inverter running into it's max power level several times. The sun would emerge from clouds and the power would quickly climb until it reached the 200w level. I never saw a level above 202 watts. I can imagine that in the summer it will be maxed out many hours a day.

here's the last 7 days production (jan 21-27)

Wed, 820whrs
Thurs, 340whrs
Fri, 200whrs
Sat, 1280whrs :)
Sun, 460whrs
Mon, 680whrs
Tues, 680whrs

That's neat Jamie.

Know what makes me sad? I have a little 12v peltier cooler that I occasionally use on my sailboat in the summer. If memory serves, it draws 4A, or 48 watts and is not very efficient with that power. That's 1152 watt hours per day to run continous - which your array could have supported for 1 of those days (assuming power storage ability).