my diy pv set-up

[groar]

Originally Posted by MetroMPG

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.

Here is my daily consumption (including hot water and heating) vs my weekly production in kWh for the last 8 weeks :

• 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

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.

[groar]

Originally Posted by jwxr7

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

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

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.

[MetroMPG]

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

[groar]

Originally Posted by MetroMPG

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.

[dogbreath]

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

[groar]

Originally Posted by groar

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.

From Watt-peak - Wikipedia, the free encyclopedia :

Watt-peak (Wp) is the DC power output in watts of a solar module as measured under an industry standardized light test before the solar module leaves the manufacturer's facility. The light test tests the output power when illuminated under standard conditions of 1000 watts of light intensity per square meter, 25 °C ambient temperature and a spectrum similar to sunlight that has passed through the atmosphere (air mass 1.5).

But other parameters are also important :

It can happen that a panel from brand A and a panel of brand B give exactly the same watt-peak in a laboratory test; but in a real installation the power output can be different. This difference can be caused by the fact that in real conditions the temperatures are different and the photovoltaic cell temperature will go up. Photovoltaic cells have a different characteristic at different temperatures; a low efficiency cell will become hot and with higher temperature the efficiency will go down and produce less power.

Denis.

[MetroMPG]

Thanks for clearing that up, Denis.

[jwxr7]

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.

[jwxr7]

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

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

[MetroMPG]

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).