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coulomb
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Post by coulomb »

EV2Go wrote: ... just shy of 700watts from a 2.2 kW system.

Which leads me to believe at less than 1/3 its potential output ...

Don't forget that the sun doesn't shine at night. (I'm assuming that the total hours includes nighttime.) So 50% (a little more in summer) is all you could get with panels that glued to the sun from dawn to dusk, never a cloud, no atmospheric dispersion, perfectly clean panels, no derating from temperature.

2.2 kW of panels is never going to produce anything like 2.2 kW continuously 24 hours. From 11am to 1pm (ignoring daylight savings) in summer with no clouds and cooling the panels... yes.

There are many that say that trackers aren't worth the hassle.
Last edited by coulomb on Wed, 20 Apr 2011, 09:33, edited 1 time in total.
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EV2Go
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Post by EV2Go »

No I don't think so, I believe it only records the hours where there is a production of energy.

Just checked when I first posted it was 13 days ago, so 13 * 24 = 312hrs (rough figures) so 138.4 producable hours sounds about right.

Quick calc... 138.4 / 13 = 10.65hr per day.

Considering some of those hours are spent at above 1.6kWh there must be quite a number of hours well below the the .7kW average.

Assuming the mornings and evenings are the culprits. that indicates to me there must be a few hours both ends of the day when power delivery is not much more than a few hundred watts.

Edit: Further calcs 96kWh / 13 days = 7.38kWh average per day, so about 700w an hour looks about right.
Last edited by EV2Go on Wed, 20 Apr 2011, 10:05, edited 1 time in total.
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woody
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Post by woody »

It's not just the angle of the panels which affect the kWh in the morning and evening - it's the distance through the atmosphere which the light travels through - e.g. when the sun is at the horizon, the light is travelling through the atmosphere at a shallow angle, lots of power is lost there compared to when the sun is beating directly down.

Also you'd need to spread your panels out further or angle them as one big panel so that each panel didn't cast shadows over the neighbouring panels.

Maybe if you have a camera which does time lapses you could take a photo every 10 minutes of the meter on a sunny day and see when you are making the big bucks :-)

You could get the sun angle from a website somewhere and calculate how much power is lost through panel angle (cosine?) and see how much money you are throwing away everyday by not doing it...
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Post by EV2Go »

With the roof pitch being fairly shallow I don’t think it actually does much until the sun gets overhead, I think your suggestion of time lapse photography would tell the real story (or just go out at set interval and note it down). Getting a power profile might give some kind of idea if moving the panel would be worth the effort or not.
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Post by EV2Go »

Took a few random readings today to put my theory to the test... today was sunny and fairly even temp.

At 12.00 - 3.6kW had been produced (assuming it started producing minimal power at 6.30ish – 654w per hr)
At 3.00 - 8.8kW had been produced (1.73kW per hr)
At 4.00 - 9.3kW had been produced (500w per hr)

When I checked the output at 4.00 the reading was down to 350w-400w with the sun struggling to get any direct light on the panels.

Unfortunately I didn’t get a final reading before it shut off for the night.
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Post by moemoke »

We have a 2kw grid system which I moniter with a Sunny Beam data collector, it has a daily graph and a monthly one. The most we have produced in a day is 13.3kw/h which was in late feb/ march I think.
The daily graph is interesting in that around late dec it starts producing power from about 6am up until about 7.30 pm. This summer as been pretty poor as we've had a lot of cloudy days.
If your inverter has bluetooth which most of the newer ones do try uploading your data to this great site http://pvoutput.org/live.jsp
here you can also see how other peoples systems perform, you may find someone near you with a similar system which you can compare with.
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Post by electriker »

I've had a 1600 watt system running for a couple of years now, and this graph shows the percentage of my consumption which came from the sun, month by month. I initially started with 1000 watts, but upgraded to 1600 watts in Feb last year, so those figures from year to year don't match. Where there are four months showing more than 100% generated there are several days where I've actually gone to 200%.

Image

I've got a few batteries which store the energy during the day, so I switch the house off the grid (except for the old 240 volt fridge) at sundown after a sunny day and draw very little from the grid. The biggest single power consumer is the electric booster for the solar hot water system, but it gets switched off at about the end of September and doesn't go back on again until the end of April or later.

At the end of the financial year '10/'11 I received a cheque for $277 from the Govt for power I sold. So really I had all my power for that year free and even made money. I reckon, taking into account some of the govt grants and subsidies, I'll probably have the whole system paid off by about 2016 or so.

Joe

Last edited by electriker on Tue, 20 Sep 2011, 16:25, edited 1 time in total.
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