I am in Melbourne and about to install a 2K system. Some installers have told me you should't have them facing directly west as the overheating in summer can substantially reduce their efficiency. Does anybody know anything about that?
Issues with West facing Panels overheating?
(13 posts) (5 voices)-
It does have an effect, but possibly not quite as serious as some might imply. I have a 2kw, west facing system installed June last year, so have experienced my first summer. I'm in central west NSW where the temps typically well exceed Melbournes.
In January my system produced 347kWh for the month, an average of 11.19 per day. My best days produced 14kWh. My hottest day 38.8 produced 12kWh, a day of 36.9 produced 13kWh, ad I still achieved 14kWh on a day recorded as 33.8. (also December 31, 2010 a day of 36 produced 14kWh)
I know from my own recordings that the afternoon temperature in the sun was at least 48, so goodness knows what is was on the roof!
If you can't have a northern orientation, then you can still get good results on the west.
Posted Sunday 1 May 2011 @ 11:25:32 am from IP # -
Russell Moore
Memberglynn,what your installers have said is correct, for every 1ºc your panels rise in temperature you lose around 0.45% of output. On a sunny day when the air temperature is 35ºc your panels can get to 65ºc. I water cool my panels and can reduce that panel temperature to 45ºc on such days. Check out the whirlpool forum site ,water cooling solar (PV) cells, to see how some are doing this.
Is your roof facing directly west? or north of west, as the further towards the north you can point them the better. I have also seen that panels facing NE will do better than panels facing NW as the mornings are cooler, and hence you get better output. Also in summer you often get afternoon cloud build up which can effect west facing panels more.
Search through the pvoutput site as well, and see if you can find some systems in your area with different aspects, so you can compare the differences. Remember to only compare systems with similar days of outputs. It is not fair to compare a system that has been up for say 2 months through summer, with one that has been up for a year. You can strip the information to equal days if you want to.
If your have heaps of roof space you could try amphorous panels, as they are supposed to withstand heat better, but you need twice as many for the same output as mono and poly panels. Or if you are prepared to spend more, Sanyo makes panels that are a cross between the two (HIP/HIT) and withstand heat better than the standard mono/poly panels.
Posted Monday 2 May 2011 @ 1:14:11 am from IP # -
I guess the word "substantially" in glynn's post could to be put into some sort of context.
a system may well drop its output by 20% on a 40 degree plus day, however we are talking about Melbourne, a city which statistically experiences these temperatures on 0.7 days during the month of January! so the "substantial" reduction in efficiency over the course of a summer, may in real terms be quite modest.
Melbourne cloud levels (east or west) will have a far greater negative effect the systems efficiency than a few hot days.
glynn, you might also find the CEC consumer guidelines helpful to read, I forgot to add the link yesterday
http://www.cleanenergycouncil.org.au/cec/resourcecentre/Consumer-Info/solarPV-guide
Posted Monday 2 May 2011 @ 3:49:25 am from IP # -
hamish05
MemberYou have to believe the science regarding loss of efficiency due to heat.
However, what the science doesn't take into account is Melbourne's extremely variable weather. You immediately think summer = consistently high temps, well I don't have to tell you that is not the case, the consistent part anyway. I am in Melbourne, my panels face about 10 deg north of west, and I made a 8% allowance in my production capacity for that. (pos this is generous)
I am of the view that the efficiency lost due to high afternoon temps is somewhat negated by slightly better performance during Autumn and Spring when the west or north west facing panels are better aligned to maybe take advantage of the mid to late afternoon sun, which is a regular in Melbourne.
I noticed an array on a tilt frame on a house in Brunswick Rd Northcote recently on a west facing roof , looked b awful for what is possibly a very small gain.
Posted Monday 2 May 2011 @ 4:22:24 am from IP # -
hamish05 - agree, we have to believe the science, however the temperatures "on the ground" so to speak can tell a different story as you note
for January, Melbourne statistically has 11.4 days > 30 degrees, whereas my location has 30.6 days > 30.
my 'argument' if you will, is primarily with the word 'substantially'.
also has anyone seen research showing that high temps have a worse effect on western oriented panels, to those oriented north? afterall, the northern orientation is to maximise year round production & I don't see how the temp on my northern roof surface area would be any cooler than the western area on a hot day.
just curious about this last point
Posted Monday 2 May 2011 @ 5:00:22 am from IP # -
hamish05
MemberI am inclined to agree that "substantial" is quiet possibly overstating the real situation.
Sure, during the summer some efficiency will be lost due to hi temperature effecting the panel efficiency,(the science says). But I have spent lots of time north of the Murray and the weather pattern is remarkably different to here.
Today in Melb is very typical. (regardless of temps) Cloudy all morning good sunshine and clear sky all afternoon. My array facing just north of west looks like it is better aligned than if it was facing north.
Unfortunately, there are no others on "PV Output" in my area to compare with
Posted Monday 2 May 2011 @ 5:55:54 am from IP # -
Russell Moore
MemberOK, I have tried to do some comparisons on pvoutput.org, with systems from postcodes 3000 to 3200. I only compared systems that had been posting for between 300 and 420 days.
I found two north facing (Lloyds, and Michigan Frog), two west facing (Stuart's place, and Chowie Power), and one NE facing (Nev's Solar).
Average for the north facing two was a daily average of 3.588kWh/kW, west was 3.120kWh/kW, and NE 3.152kWh/kW. So NE was 12% worse, and west 13% worse in comparison to the north average. Average days reporting for the north panels was 357 days, west was 334, and NE 350 days. Unfortunately this is far too low a number of systems for a real statistical comparison. But at least it is something to go on.
Posted Monday 2 May 2011 @ 11:52:08 am from IP # -
http://www.pvoutput.org/compare.jsp?sid=1265&sid1=16&t=m
well compare the output of these 2 system, mine on the left - they are identical systems supplied by the same installer.
my low numbers in November were due to lacking an inverter for 8 days
certainly my numbers will be lower in late winter & early spring, but then catch up in late spring & summer. hopefully we can continue to compare over a couple of years.
Russell, no one is saying that North is not preferable - however some of the statements tossed about regarding output losses on a western orientation are grossly overstated; as noted by Clean Energy Council and a few other reputable independent bodies.
Posted Monday 2 May 2011 @ 12:53:11 pm from IP # -
Russell Moore
MemberJust giving some real world comparisons....not advocating one or the other, I was a bit surprised to only see a 13% difference from west to north though. Of cause the sample is small, but at least they are in the Melbourne region.
cw nsw, your comparison is with a system 150km away from you, and on the other side of the Great Dividing Range, perhaps a comparison with Wildfire at Dubbo might be closer to the mark? A pity he doesn't post anymore.
Posted Monday 2 May 2011 @ 10:48:04 pm from IP # -
russell, the whole point of the comparison I gave, is to demonstrate that the losses incurred by a combination of western orientation and high temperatures, are not "substantial" when compared to the output of a preferred northern orientation with lower temperatures (also preferred).
basically I've tried to address glynn's question with some live examples that should measurable allay his concerns
petanque - I've read statistics that have shown that to be true in some cases.
Posted Tuesday 3 May 2011 @ 12:14:51 am from IP # -
Russell Moore
MemberI suppose it is what you consider substantial. I would guess 20% could be considered substantial.
So with my rough calculations in Sydney it is 19% worse for west vs north ( H2O Cool russell moore vs PVWest), 13% worse in Melbourne, (as per my other post) and for your area (you vs Wildfire, using only monthly outputs for Aug, Sep, Oct, excluding Nov, Dec Jan) west is 10% worse, if we had more outputs from you two, I would think that the results would skew more towards Wildfire. with better winter results for him.
So all in all not as much difference as you would think, and in fact in December you were 5% in front of Wildfire.
The biggest differences seem to be in winter, where I have been 43% in front of PVWest on average over May, June and July (we are in western Sydney), in Melbourne with Lloyds vs Stuart's in those months it has been 19% in favour of Lloyds norh facing panels. You and Wildfire don't have outputs to compare over those months.
If you can't face your panels north in Melbourne, west seems to be an OK direction, just expect winter outputs to be lower.
Posted Tuesday 3 May 2011 @ 1:35:19 am from IP #
