solar panel predicted vs actual generation / efficiency

tunnel

selsdon101 wrote: »

i've just received a quote from a local company called fusion electrical who say they can fit a 2.2kW £3920 system (suntech 275) to a 2.4kW £4330 system (using LG 300W panels), with a Solis mini inverter. Thats a tempting deal, definitely seems better value than hanergy - 47% higher peak power for just £120 more.

Now your talking. now get a couple more companies in to quote the same deal and pip them against each other.
There is also benQ 330Wp panels, although these do come at a premium price, see what they can do those for and if the price difference is only 10% more then it's obviously worth considering as you'd get 10% more generation.

selsdon101

Martyn1981 wrote: »

Have a play with PVGIS and explore a 2.5kWp SW + 1.5kWp NE system using 'normal panels'. Installing a 'tiny' system on the basis that it'll generate slightly more efficiently doesn't sound sensible to me. At the end of the day you want as big as system as you can fit, whilst considering overall cost and relative ROI.

Back in my American muscle car days when I learned that torque is more important than bhp, there was a simple saying (or two) - 'there's no substitute for cubes', or 'there's no replacement for displacement'.

Mart.

PVGIS suggests hanergy (CIS/CIGS) of the same kWp as crystalline is only 1% or so higher output for a NE or a SW facing roof, really contradicts the 'better low light performance' claims for thin film, unless i'm misinterpreting or the calculator is wrong - it makes no claims about its accuracy.

zeupater

selsdon101 wrote: »

PVGIS suggests hanergy (CIS/CIGS) of the same kWp as crystalline is only 1% or so higher output for a NE or a SW facing roof, really contradicts the 'better low light performance' claims for thin film, unless i'm misinterpreting or the calculator is wrong - it makes no claims about its accuracy.

Hi

Okay, you're starting to get there, so here's something to ponder over ....

The Hanergy panels are claimed to be more efficient in low light conditions .... so, let's test that by comparing them to a hybrid panel which makes the same claims ....


http://solibro-solar.com/uploads/media/Solibro_data_sheet_SL2_module_G1-5_2014-07_Rev02_Special_data_sheet_125Wp_EN_01.pdf

http://eu-solar.panasonic.net/fileadmin/user_upload/downloads/technical_documents/VBHN285SJ46_PEWEU_UK.pdf

.... Okay, the presentation is different but under standard flash test conditions with 200W/sqm irradiance the 125W Hanergy panel (low irradiance curve) shows a -4% relative drop in performance, so it's producing 24W(125*0.2*0.96) .... in comparison the Panasonic datasheet claims a low irradiance flash test (200W) of 56.8W, which when worked backwards equates to a -1.4% (56.8/(285*0.2)) relative drop in performance, which seems to suggest that the hybrid has better relative low light performance .....

So, considering that a considerable limiting factor is roof area, what does this mean in the real world ?, well that's pretty simple. Under low light standard test conditions, the Hanergy panel generates at a power density of 25.7W/sqm (24/(1.19x0.785)) and the Panasonic 36.9W/sqm (56.8/(1.463*1.053)) .....

The issue here is that the Hanergy 1.5kWp system is costing £2.53/Wp (3800/1500) and that it likely (depending on roof dimensions) that you'd be able to get a larger capacity hybrid array (8 panels?) which perform just as well in low light conditions for a similar total price, so somewhere around £1.70/Wp (3800/(8x285)) ....

HTH
Z

selsdon101

hmm thats really interesting. i've looked at few other spec sheets now for crystalline panels and they all claim around 50-60W low radiance performance, if you take 200W/m2 as being low. But perhaps 50-100W is a more realistic radiance level a solar panel will be exposed to most of the year? In which case the spec sheets don't show the rating.


I'll probably go with crystalline in the end but getting back to the original point of the thread, it would be good to get real world stats from hanergy installs. The pvoutput.org comparison showing the 2.5kW henergy install equalled or outperformed the 4kW crystalline one for the 4 darkest months of the year is promising.

zeupater

selsdon101 wrote: »

hmm thats really interesting. i've looked at few other spec sheets now for crystalline panels and they all claim around 50-60W low radiance performance, if you take 200W/m2 as being low. But perhaps 50-100W is a more realistic radiance level a solar panel will be exposed to most of the year? In which case the spec sheets don't show the rating.


I'll probably go with crystalline in the end but getting back to the original point of the thread, it would be good to get real world stats from hanergy installs. The pvoutput.org comparison showing the 2.5kW henergy install equalled or outperformed the 4kW crystalline one for the 4 darkest months of the year is promising.

Hi

The winter performance difference could easily be explained by a combination of worse winter month orientation and shade on the crystalline panels - a West facing should logically receive less direct sunlight during the winter than one facing SW and shading issues are generally much more apparent in the winter than summer. After all, the comparison was simply to a similar aspect system in the same area which was selected completely at random ....

I agree about the point regarding the Hanergy panel data, but that's really the same for all panel manufacturers ... where there's no regulated requirement on comparative data, performance claims are usually made on an 'up to' basis, often supported by little more than a single comparative test result, probably produced using specially selected panels on a particular day in a particular location .... even in a really good sample distribution curve there are outlying extremes which marketing departments love to leverage ....

Regarding the " 2.5kW henergy install equalled or outperformed the 4kW crystalline one for the 4 darkest months of the year is promising" ... well, for comparison, it outperformed our(~WSW) ~4kWp system in efficiency terms (kWh/kWp) on one of those months by ~2%, then again, in one of the three months where it performed worse, it lost out by well over 20% - then again, in total generation terms, over the four months it generated just over half (kWh) .... our system performs well considering the aspect, but the panels aren't speciality low light units or hybrid, just monocrystalline ...

HTH
Z

Martyn1981

zeupater wrote: »

Hi

The winter performance difference could easily be explained by a combination of worse winter month orientation and shade on the crystalline panels - a West facing should logically receive less direct sunlight during the winter than one facing SW and shading issues are generally much more apparent in the winter than summer. After all, the comparison was simply to a similar aspect system in the same area which was selected completely at random ....

HTH
Z

I think this is quite important when comparing the winter months, as the differences in panel orientation and slope will significantly affect performance at those times.

Not only will W v's SW make a big difference, but the 38d v's 1d pitch is also very significant as you get further off-south.

Comparing my (main) ESE system to the WNW, with both at 30d pitch, the target generations are 807kWh/kWp v's 679kWh/kWp, so no surprises there.

But the June : December ratios are ESE 6.5:1 and WNW 11.42:1

So (apologies for the poor English/description) but for my systems most of the difference seems to get squeezed into the poorer 6 months when panels further from south see less and less sun, and steeper pitches see less and less sky (for reflection).

Mart.

Martyn1981

selsdon101 wrote: »

I'll probably go with crystalline in the end but getting back to the original point of the thread, it would be good to get real world stats from hanergy installs. The pvoutput.org comparison showing the 2.5kW henergy install equalled or outperformed the 4kW crystalline one for the 4 darkest months of the year is promising.

As per my reply to Zeup, I suspect the system differences explain those 4 months. However, for actual results, I compile kWh/kWp results each month on the Navitron forum. About 30 members post results and the spreadsheet covers several years.

One of them has a CIGS system, though he hasn't posted this year. But in previous years his system is generally in the top 5 each month, so I suspect there may be some truth to these systems working a little better, perhaps in the 5-10% range, but it just doesn't seem enough to me to warrant having a smaller system, with overall lower generation, when for the same(ish) price you can simply brute-force it with more kWp/m2.

I'll PM you a link to the spreadsheet.

Mart.