Average Annual Power Output per pound spent vs Panel Efficiency

[shanklin]

I am in the process of getting quotes for a PV system of up to 4kW for a house located 35 miles SW of London, and have been looking at various manufacturer's claims w.r.t. performance. The primary data that I seeing presented are:

• maximum panel output
• panel efficiency, albeit no satisfactory definition of this is really provided in what I've read

Panel efficiency is clearly relevant in that, the greater the panel efficiency, the smaller the panel's area and weight for a given maximum output power. As stated on a number of discussion threads here, this is helpful if there are weight or space limitations with the roof on which the panels will be installed.

However, this apart, I am not too concerned about panel efficiency. What I am, however, very interested in is the average annual energy output (kWh) per panel and, based on the quotes I get, the cost of each kWh of average annual energy output per pound spent.

Sanyo claim to be (one of?) the best in terms of achieving better power output, compared with their maximum rated output, in different light and temperature conditions. This will presumably help in terms of annual energy output.

So, whilst they are more expensive than other panels I have quotes for, given space/weight considerations I am considering going with an array of their HIT panels.

This unfortunately feels like a bit of a punt of my part as despite massive googling over the last few days, I cannot find any source of data that objectively compares panels in terms of their average annual energy output in a given situation, say south-facing with a given roof pitch at a given location in the UK.

All the focus in instead on efficiency. This seems to me like comparing football teams in terms of what proportion of the chances they create they actually score from (Team A: 20%, Team B: 25%) and ignoring the fact that Team A create 3 times as many chances as Team B.

Anyway, in a practical sense, I would be grateful for any advice people can provide. Many thanks

 

[claypole]

Excellent question - wish I knew the answer! Like you I spent hours googling for the more relevant comparison figures with no joy. As far as I got was to compare the temperature co-efficient of the panels (the HIT's losing less at normal operating temperatures). After doing the math this alone was not sufficient to encourage me to make the extra spend BUT the math still involved a lot of estimations, and of course there will be other differences between the panels' performances. I think I did find one or two o'seas tests but there were still far too many variables and of course was not UK climate based. I wonder if best bet might be to analyse some figures from sites entered on BDVP (think that's right name) and try to get some direct comparisons. Still potential for a number of variables coming into play but if you could garner enough comparison figures it might give you a firmer lead. I gave up in the end and just went with least spend (using Sharp monos) which meant the HITs would have to significantly outperform to make up the difference. Somewhat frustrating because if you can calculate the payback period as being not too far adrift then of course the residual income after the payback period is going to be higher (assuming they do actually outperform). Anybody else found any more meaningful figures?

 

[BruceB]

I think you can get what you are after but you will have to compare the results yourself using something like Sunny Design. I have put a screenshot of the output below. You will see it has the annual yield, but it also has the specific energy yield kWh/kWp. Dividing that into installed cost per kWp will give you a cost per kWh of yield. Sunny Design will let you substitute in the panels you want to compare. A bit laborious but possible. I suspect the HIT panels are only worth it when you want large output from a small roof. In pure cost effectiveness terms I do not believe they work when you compare them with the much cheaper Chinese panels.

Regards
Bruce

 

[claypole]

Thanks Bruce, I'd completely forgotten I'd also used Sunny Design for this. Yield difference was less than 5% for me which even over 25 years was not going to make the payback on the extra panel cost. I did nevertheless wonder how reliable the SunnyDesign figures would be against real world scenario, given that Sunny Design must rely to some degree on assumed figures rather than real world testing of all panels. However the shortfall in making it work was so large I felt it unlikely that the HITs could pay unless, as you say, space limitations come into play.

 

[t4sltd]

Only independent source of kWh / kW data I know of is Photon text: Solarworld best, Sharp worst, Sanyo not included. Difference 10%. I think you could maybe expect Sanyo to perform 10% better than 'standard' panels e.g. Sharp.

 

[SRE]

Here's a thought. On paper Sanyo are better and I have to say are a much nicer panel but I visited one of our customers yesterday with their final paperwork. They were delighted with their Sanyo panels and were telling everyone about them, it's one of the neatest installs we've done - everyone happy BUT they had generated the same amount of energy as we had with out Sharp NU180 panels which are supposed to be 5% less efficient, added to which we are ESE orientation compared to their SSE orientation. Admittedly it's been sunny rather than cloudy so the benfits of the Sanyo may yet kick in but I'm not convinced about paying the extra for extra yield. Extra for better quality and a nicer panel yes, yield - the jury is still out ...

 

[Worcester]

W/m2 though can make a difference, we have one install where due to the shape we got 3.84kWp of Sanyo and could only get 3kWp of anybody else's in that instance the total installed £/kWp did add up

 

[claypole]

Hi SRE - could be some useful comparisons to record there. The 5% efficiency difference is irrelevent - just means the Sanyos will be 5% smaller for same output. However will be very interesting to see if the Sanyos give any higher yields in low diffusion conditions, assuming your Sharps are geographically very close to them.

 

[claypole]

Worcester - looks like we need a new measurement unit of ROI/m2 !

 

[JD6400]

There is every chance that i did not input the data right but i ran a few scenarios through PV-SOL EXPERT the other day for one of our 50kw quotes on a south 15 degree Ag barn with Mitsubishi , sanyo , sharp and schott
Rather interestingly for price / output schott were way ahead on the return on capital ?

 

[Ramjam]

Only independent source of kWh / kW data I know of is Photon text: Solarworld best, Sharp worst, Sanyo not included. Difference 10%. I think you could maybe expect Sanyo to perform 10% better than 'standard' panels e.g. Sharp.

Sharp poly, not Sharp mono, not fair to write sharp off on the basis of that test alone.

 

[t4sltd]

I agree (we install both Sharp Poly and Mono when clients want it). I meant to make the point that the difference between top and bottom is 10% (typically more than the price difference between panel types)