Solar power calculations, please help!

[John Rumm]

Harry's figures suggest a year round average of just under 460W - so hardly 45%. However he has not said what panel area he has.

[Chris Hogg]

Your link says almost nothing about W/m^2 of photovoltaics in California. Plenty on installed capacity of solar farms, but nothing on area. As usual, you give an irrelevant link that you've not even read.

The California Valley Solar Ranch* produces about 62.5MW. It covers an area of 1966 acres, giving an average of ~7.9 W/m^2 if my maths is correct (62500000/1966/4047). Even allowing a factor of two or even three for the area quoted being a total acreage and not actual panel area (i.e. 1966 acres of total area might only be 983 or even 655 acres of actual panel area), it still makes your claims look a trifle optimistic, especially as California gets twice the intensity of sunshine that the south of England gets (204 W/m^2 for San Francisco cf. 109 W/m^2 for London)**.

**

[TomSawer]

[harry]

Tch. A 4KWp array is a 4Kwp array anywhere in the world and will be the same area (if the same technology) Some places have more or brighter sunshine eg California. However, it's also hotter (reduces efficiency) and dustier.

I don't give a *** for your calculations, I am giving you actual meter readings.

You can find insolation maps on the internet if you want to get some idea of PV panel performance. (Doesn't allow for snow covering the panels.

[John Rumm]

So ~23 W/m^2

[harry]

Ah. Another whinging socialist.

[Chris Hogg]

Well, yes, obviously. But we were not talking peak figures, but averages over a year.

That's all very well, but it still doesn't explain why your panels seem to be able to produce more power on average than big commercial operations in a much sunnier place such as California. Two explanations come to mind.

The first is that like is not being compared with like, and figures given for the big farms are based on acreage of the site rather than specifically the area of the panels alone. I think that's a real possibility.

The second is that your panels have better than average efficiency. From the figures you have given here and elsewhere, each of your panels is 1m^2 and produces 200Wp*. That's better than any listed in the table here

which may not be up-to-date. What particular panels do you have installed?

*20 panels, output 4kWp, 20m^2, 1kWp per 5m^2, hence each panel is 1m^2 and produces 200Wp.

[dennis]

Would you have fitted panels if they didn't make you a large profit? Obviously someone that cared about the environment and believed AGW was a threat would have.

You aren't honest enough to admit you did it for the cash and sod all else. Its why I installed cavity wall insulation 30 years ago as it saved cash not because it saved the planet.

[harry]

Both. Renewable energy is the sensible way to go. Only the brain dead can'tseethis.

[harry]

There's 21 panels rated at 185 watts peak each. They are polycrystaline. The efficiency is 11%.

[Chris Hogg]

I have no objection to people doing what Harry has done, insulating their houses to the extreme, using solar panels to supplement existing grid electricity or hot water, driving electric cars and wearing thermal underwear and thick pullovers. If it cuts down on their fuel bills and they think they're saving the planet, it's OK by me, whether they're right or wrong on the latter. But I do object to the rest of us having to pay for their indulgence. The sooner the govt. withdraws subsidies, the better.

[Chris Hogg]

Thank you for that. But not 20 panels as you said earlier, and not

4kWp either, more like 3.885kWp to be pedantically precise. But still nothing on their area. Who made them? As your electric car is a Mitsubishi, I wondered if you had Mitsubishi panels, but AFAICT all their 185Wp panels have areas greater than 1m^2 (typically 1.3 - 1.4 m^2) and have higher efficiencies at 13-14%. All the panels that I can find that have an area of ~1m^2, not just Mitsubishi's, have peak outputs less than 185W. If you don't know the exact size, tell me who made them and I can probably look them up.

[harry]

All energy sources are subsidised in the UK. Renewables less so than most others.

[harry]

They are Mitsubishi panels. Model TD185MF5_

No longer imported. Dunno why.

They do more annual power than was calculated in the quotation which was 31

87.8Kwh Even on a "bad" year.

I think we are in the rain shadow of the Malvern Hills and the quotation is for average conditions. Also, we are on a hilltop (increases day length an d diffused light.) Max daily energy generated 30Kwh (Two occasions only in over four years)

My second array has Norwegian panels and is 16 x 250w. (Less than a year old)

We export more electricity than we use. Plus zero fuel costs with electric car in Summer.

I would get more but the local transformer isn't up to it. Quoted £6000 to change it. So, not viable.

Most of my immediate neighbours have PV panels as well.

[Chris Hogg]

Thank you.

1685 x 834 mm, so 1.383 m^2 each. Efficiency 13.4% (better than you remembered; can't be bad!).

21 panels, total area 29.0 m^2, 4000 kWh, gives a figure of 15.7 W/m^2 averaged over the year. Very close to Chris Dixon's numbers (15.9 W/m^2), which is what one might expect.

Brings the numbers back to something sensible.

[tony sayer]

Prove it...

[tony sayer]

Really>, what sort of amperage are they putting out?...

[harry]

It's a pole transformer, 25Kva ISTR The issue is not the transprmers' capacity, it's the rise in local voltage caused when the panels are at full output and nobody locally is using any electricity. Made worse by other people nearby having PV as well (not on same transformer)

[harry]

If you are that interested our annual "Open Day" event is in October. You can email me.

[Andy Burns]

Putting the lie to your previous statements that solar power reduces load on the grid as it's consumed locally?