Solar panels and battery - any real world reccomendations?

BUDFORCE said:
Is this normal?

Panels been installed for 4 days, first two days a bit cloudier but was peaking about 4.3 ish kw, which is what Id expect on a 4.5kw system.

Yesterday and today, clear days, smoother generation, but it capping out about 3.2kw.

Only thing I can think is heat is affecting something????
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Live near the sea? Couple days after I'd installed mine I went up the roof to find some flying monster had christened the panels with their toxic waste. I wash the panels more often than the car now.
 
Journey said:
No that isn't normal at all, they (the panels) have to be hitting 65c to be severely affected. Find out what the temperature coefficient of Pmax is for your panels, should be on the data sheet. You can then work out what the loss would be based on the formula T(temperature) x Pmax -0.44%/c . If you are hitting 35c then you shouldn't be losing much more than 15% overall. Put your value for Pmax in place of the 0.44 value btw.

So 35c * Pmax 0.35%c for my panels = 12.25% loss of maximum possible output. It's actually much lower than that as I believe they use 25c as the starting point, so it would really only be 10c * Pmax 0.35%/c or 3.5%
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These panels, actually that isnt the EXACT same model as we have, ours in the standard "black - zebra" version? But reading through the technical specifications are idential. 375w x 12 panels.

Edit: The installer is on a course today, but said will call tomorrow to "explain" why, which doesn't fill me with confidence.
 
@BUDFORCE Can you read off the DC input voltage from the inverter? This will tell you the total string value, if using two it might be listed as to separate DC voltages. OCV per panel is 41.5v according to your spec sheet, so you should be hitting a peak of around 490v if all on one string, and fully loaded, less the efficiency loss due to temperature.
 
Journey said:
@BUDFORCE Can you read off the DC input voltage from the inverter? This will tell you the total string value, if using two it might be listed as to separate DC voltages. OCV per panel is 41.5v according to your spec sheet, so you should be hitting a peak of around 490v if all on one string, and fully loaded, less the efficiency loss due to temperature.
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Yes about 350v DC now but we have whspy clouding here now plus 2pm so not peak.

I will check tomorrow at midday if it's clear.

They are all on one string, I overheard the electrician, each panel is 41.5v and the limit was 520 so just within at max load.
 
BUDFORCE said:
Yes about 350v DC now but we have whspy clouding here now plus 2pm so not peak.

I will check tomorrow at midday if it's clear.

They are all on one string, I overheard the electrician, each panel is 41.5v and the limit was 520 so just within at max load.
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Will the panel ISC is 9.3A, so that would put you at 3.255kW which is below what I'd expect, even in this weather, unless they fitted them too close to the roof with zero air flow. You need to know the panel backside temperature to work out efficiency loss but 25% is way off.
 
Journey said:
Will the panel ISC is 9.3A, so that would put you at 3.255kW which is below what I'd expect, even in this weather, unless they fitted them too close to the roof with zero air flow. You need to know the panel backside temperature to work out efficiency loss but 25% is way off.
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63c.

Used an infrared thermometer, that's about 6 inches under from the edge, far as I can get my arm, assume be a bit hotter behind the centre of the panel(s).
 
BUDFORCE said:
63c.

Used an infrared thermometer, that's about 6 inches under from the edge, far as I can get my arm, assume be a bit hotter behind the centre of the panel(s).
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Ok well your NOCT is listed as 42c (+/-2c) and your Pmax for temperature is effected at 0.37%/c, so that makes a 21c difference from NOCT, so you'd expect 21 * 0.37 = 7.77% loss using the NOCT figure provided against the 380w Pmpp figure of the panel.

Something doesn't add up, maybe they are faulty panels or b-grade, either way unless you are hitting 65-80c at the backside, then you'd expect losses at 20-30% of peak efficiency. There are lots of variables, but if installed correctly with a sufficient air gap for a good convection effect then you shouldn't be losing that much. In hotter climates, e.g. desert like conditions, they often fit aluminium heatsinks to the backs of the panels to aid with cooling, or actually have an active water cooling system in place to carry away excess heat, but we are talking very hot, all of the time.
 
Journey said:
If you are using only solar with no battery, or EV (especially this time of year) then the sensible option is to be on Octopus Agile both incoming and outgoing, the incoming is capped at 35ppkWh currently, but there is no cap on outgoing prices, so today the prices in my region are 20-37p during generating hours.

This allows you to offset the differential between the outgoing costs and incoming costs when not generating (when dark in other words), so your cost per unit is much lower, this is made even better if you can consume some of the usage at the cheaper outgoing hours, and you are given those in 30 min segments at least 24 hours in advance. If you are using a decent sized array (6kW) and it is very sunny, you can easily see £8-10 per day back with a cost back to your self of how ever many kWh hours you use at non-generating x35p, but that £8-10 would allow between 22.8 and 28.6kWh of use which is pretty much two full days use for most people, it works even better if you have battery storage!
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Contemplating ending my 2yr electricity fixed tarriff early and moving to Agile even as the summer is no doubt almost over, but in the back of my mind think it would be best to wait until I've gone through a winter to work out how I would actually use my array and batteries. currently the fixed rate is at 24p standing charge, 19.82p kwh, but even if I'm able to sell back 1 or 2kw per day this should cover it easily compared to the 5.5p i would get through ScottishPower.
 
SoliD said:
Contemplating ending my 2yr electricity fixed tarriff early and moving to Agile even as the summer is no doubt almost over, but in the back of my mind think it would be best to wait until I've gone through a winter to work out how I would actually use my array and batteries.
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Exactly what I’m doing
 
SoliD said:
Contemplating ending my 2yr electricity fixed tarriff early and moving to Agile even as the summer is no doubt almost over, but in the back of my mind think it would be best to wait until I've gone through a winter to work out how I would actually use my array and batteries. currently the fixed rate is at 24p standing charge, 19.82p kwh, but even if I'm able to sell back 1 or 2kw per day this should cover it easily compared to the 5.5p i would get through ScottishPower.
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You need to do some careful calculations, especially if you can't get back your fixed deal. How long do you have left on it?

Also since you are moving one of your cars to a PHEV then you'll likely be using quite bit of power on that if you want to keep your fuel bills down, so that is another figure to factor into the larger equation. It's slightly different if you are on a full EV with Agile, as you can time the charging when/if the prices go to the lowest point, assuming you aren't depleting the full battery every other day anyhow.

How much of your home heating is going to be done by your AC in the winter now you have your insulation done? That is another factor for you, as it may be cheaper to have Octopus Go Faster, and use the 5hour 21:30 to 02:30 to get cheap electric rather than gas, and re-charge the home batteries if using them for heating etc. in the day time. The rates for that at 8.25ppkWh off-peak and about 40p peak now, so only 5p above Agile, and you can move to the 7.5p outgoing SEG rate.

Lots more could be said, but it is a great big calculation with lots of factors some of which are moving targets, so quite hard to guess.
 
Need a sense check if you guys don’t mind as I’m about to hit the go button on the below, quote was comparative to others when I got quotes earlier this year and selected the supplier based on reviews from friends and they do top notch install work.

Planned to be installed next week (apart from battery) but they have changed the panels at the last minute due to stock issues. I’ve tried to find info on them but coming up blank on reviews, any one had experience or knowledge of them?

12 x 400w Perlight Panels

Mesh Bird Protection

5kw SolarEdge Inverter and Optimisers

11kwh Alpha ESS Smile 5 Battery

7kw Tethered Zappi EV Charger with Hub and Harvi

Total cost £17,350 fully installed
 
redfist said:
Total cost £17,350 fully installed
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They giving you a solid gold inverter for that price? :p

Do you know what panels they were supposed to be using? At that price I'd hope it was quoted with SPR-MAX3-42 BLK (SunPower Maxeon 3's 420w) - 40 years warranty, amazing panels at about £400 each, the Perlights are less than £180, with a 25 year warranty.
 
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Yeah the price is high but it wasn’t the most expensive or cheapest for our area, original panels were 405w Suntech Panels which while not the best do perform quite good.
 
redfist said:
Yeah the price is high but it wasn’t the most expensive or cheapest for our area, original panels were 405w Suntech Panels which while not the best do perform quite good.
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So what exactly would you like to know? The Perlights are ok/good panels, but not at the price you are paying for the system. Why are you buying a SolarEdge fully optimised system, do you have loads of shading? If not then you are just wasting about £4-5k.
 
redfist said:
Need a sense check if you guys don’t mind as I’m about to hit the go button on the below, quote was comparative to others when I got quotes earlier this year and selected the supplier based on reviews from friends and they do top notch install work.

Planned to be installed next week (apart from battery) but they have changed the panels at the last minute due to stock issues. I’ve tried to find info on them but coming up blank on reviews, any one had experience or knowledge of them?

12 x 400w Perlight Panels

Mesh Bird Protection

5kw SolarEdge Inverter and Optimisers

11kwh Alpha ESS Smile 5 Battery

7kw Tethered Zappi EV Charger with Hub and Harvi

Total cost £17,350 fully installed
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That price does seem high. Sure the EV charger probably adds £1k (it retails for £800 plus labour).
I got a very similar setup installed 10 days ago but ordered in March for £11.5k, add 20% for the likely price increase from high demand and inflation, and you’re about £3k over priced.
 
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Journey said:
You need to do some careful calculations, especially if you can't get back your fixed deal. How long do you have left on it?

Also since you are moving one of your cars to a PHEV then you'll likely be using quite bit of power on that if you want to keep your fuel bills down, so that is another figure to factor into the larger equation. It's slightly different if you are on a full EV with Agile, as you can time the charging when/if the prices go to the lowest point, assuming you aren't depleting the full battery every other day anyhow.

How much of your home heating is going to be done by your AC in the winter now you have your insulation done? That is another factor for you, as it may be cheaper to have Octopus Go Faster, and use the 5hour 21:30 to 02:30 to get cheap electric rather than gas, and re-charge the home batteries if using them for heating etc. in the day time. The rates for that at 8.25ppkWh off-peak and about 40p peak now, so only 5p above Agile, and you can move to the 7.5p outgoing SEG rate.

Lots more could be said, but it is a great big calculation with lots of factors some of which are moving targets, so quite hard to guess.
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Runs until next October, think deep down I'd rather just stay on it until after the winter and guarantee the savings as if prices rise further I'll be subject to them over the winter, might give up some seg payments in the short term for benefit next year. Can then work out how much of the heating would be done by the ac. Realistically I'll only be using it with any solar I'm generating.
 
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