Solar PV...Still worth it?

Martyn1981

Dave, as well as what I said earlier, quick plug for the FAQ thread, though you may have done most of the learning already by the sounds of it.

https://forums.moneysavingexpert.com/discussion/3872445

Mart.

WestonDave

Thanks Martyn - company identified - aint google great! Possibly a bit far away but will have a think.

Message re dual handling fully received - before we sign up to anything we will make sure we know what inverter we are getting and specify in writing that it should be capable of dealing with the two aspects seperately. I'd done enough research before getting any quotes to know that if we went dual aspect we needed to ensure the kit would handle it properly so we have raised it with the surveyors rather than waiting for them to mention it.

Martyn1981

WestonDave wrote: »

Thanks Martyn - company identified - aint google great! Possibly a bit far away but will have a think.

What did we do before Google? Cain are the guys, I spoke to the owner Dave a few times, he and all of the boys (boys - I must be getting old!) were very good, and fun. I'm sure they mentioned work in Bristol and Gloucester.

Best of luck, keep us informed, and by the way, SE and SW will give you a really good generation curve throughout the day, so maybe a little less grand total (-5/10% perhaps) pa than true South, but a steady supply throughout, including the evening. So a very practical system.

Mart.

silvercar

Can someone critique my qoute please.

2 banks of 8 x SHARP Corporation ND-R250A5 250 W, one bank is pointing south (-20 degrees) at a steepness of 25 degrees, the other east (70 degrees). The inverter is Power-One PVI-3,6-OUTD 3.6kW.

The calculations are:

Location: LONDON/HEATHROW
Climate Data Record: LONDON/HEATHROW
(1981-2000)
PV Output: 4.25 kWp
Gross/Active PV Surface Area: 27.92 / 27.99 m²
PV Array Irradiation: 28,680 kWh
Energy Produced by PV Array (AC): 3,496.8 kWh
Grid Feed-in: 3,496.8 kWh
System Efficiency: 12.1 %
Performance Ratio: 80.0 %
Inverter Efficiency: 94.0 %
Specific Annual Yield: 819.7 kWh/kWp
CO2 Emissions Avoided: 3,087 kg/a

Does that make sense??

EricMears

silvercar wrote: »

Can someone critique my qoute please.

2 banks of 8 x SHARP Corporation ND-R250A5 250 W, one bank is pointing south (-20 degrees) at a steepness of 25 degrees, the other east (70 degrees). The inverter is Power-One PVI-3,6-OUTD 3.6kW.

The calculations are:

Location: LONDON/HEATHROW
Climate Data Record: LONDON/HEATHROW
(1981-2000)
PV Output: 4.25 kWp
Gross/Active PV Surface Area: 27.92 / 27.99 m²
PV Array Irradiation: 28,680 kWh
Energy Produced by PV Array (AC): 3,496.8 kWh
Grid Feed-in: 3,496.8 kWh
System Efficiency: 12.1 %
Performance Ratio: 80.0 %
Inverter Efficiency: 94.0 %
Specific Annual Yield: 819.7 kWh/kWp
CO2 Emissions Avoided: 3,087 kg/a

Does that make sense??

It's a little difficult to see where the "PV Output: 4.25 kWp" line comes from !

If all 16 panels were pointing directly at the sun you'd expect them to produce 4kwp (but maybe a little more if they had a significant degree of positive tolerance). With half of them pointing in the 'wrong' direction that should be reduced - indeed, that would be a good argument for an inverter that shouldn't handle the full 4kwp.

If the inverter is rated at 3.6kwp, then again it might briefly sally above that if panels were providing enough output but I wouldn't expect a sustained putput of more than its rating.

GaryMo_2

silvercar wrote: »

2 banks of 8 x SHARP Corporation ND-R250A5 250 W,
PV Output: 4.25 kWp

Does that make sense??

That bit doesn't, it's 4kWp of panels capped to 3.68kW by the inverter.

Martyn1981

silvercar wrote: »

Can someone critique my qoute please.

2 banks of 8 x SHARP Corporation ND-R250A5 250 W, one bank is pointing south (-20 degrees) at a steepness of 25 degrees, the other east (70 degrees). The inverter is Power-One PVI-3,6-OUTD 3.6kW.

The calculations are:

Location: LONDON/HEATHROW
Climate Data Record: LONDON/HEATHROW
(1981-2000)
PV Output: 4.25 kWp
Gross/Active PV Surface Area: 27.92 / 27.99 m²
PV Array Irradiation: 28,680 kWh
Energy Produced by PV Array (AC): 3,496.8 kWh
Grid Feed-in: 3,496.8 kWh
System Efficiency: 12.1 %
Performance Ratio: 80.0 %
Inverter Efficiency: 94.0 %
Specific Annual Yield: 819.7 kWh/kWp
CO2 Emissions Avoided: 3,087 kg/a

Does that make sense??

Hello Silvercar, I don't understand the 4.25 so I'm going to run with 2 times 2kWp (8*250W).

For East (-70) PVGIS climate gives 1,650kWh/pa
For South (-20) PVGIS climate gives 1,820kWh/pa

Total 3,470kWh/pa, so we appear to be in the same ballpark. I just choose to click on the M4 just above Heathrow. Have I got the roof orientations right?

Regarding CO2 saved, Celerity started a thread yesterday which seems to suggest 0.5kg per kWh, so around 1,700kg.

Remember, these are only calculated guesses, is there any shading?

Mart.

grahamc2003

silvercar wrote: »

Can someone critique my qoute please.

2 banks of 8 x SHARP Corporation ND-R250A5 250 W, one bank is pointing south (-20 degrees) at a steepness of 25 degrees, the other east (70 degrees). The inverter is Power-One PVI-3,6-OUTD 3.6kW.

The calculations are:

Location: LONDON/HEATHROW
Climate Data Record: LONDON/HEATHROW
(1981-2000)
PV Output: 4.25 kWp
Gross/Active PV Surface Area: 27.92 / 27.99 m²
PV Array Irradiation: 28,680 kWh
Energy Produced by PV Array (AC): 3,496.8 kWh
Grid Feed-in: 3,496.8 kWh
System Efficiency: 12.1 %
Performance Ratio: 80.0 %
Inverter Efficiency: 94.0 %
Specific Annual Yield: 819.7 kWh/kWp
CO2 Emissions Avoided: 3,087 kg/a

Does that make sense??

Well, your inverter is twin mppt, which is what you want.

The max input power for your inverter is 4.15kW, yet your panels (nominal 4kW) can actually produce 4.25kW, according to what you wrote. Not ideal, but probably the best fit they could manage, and in any case, your split orientation means you'll never generate the theoretical 4.25kW DC max.

All adds up OK to me. To be ultra cautious, It may be worth checking the max voltage/power for each string - depending on how many panels are on the S string you could potentially exceed those maximums for the S string.

silvercar

Wow, so many responses.

Looking again the quote is for 16 panels, but the diagram has a 9 and an 8 for the 2 roofs, so maybe 17 in total - I assumed the 9 should be an 8, but it could be that the 16 should be a 17.

orientation is -20 and +70.

I'm 30 miles from Heathrow, so I don't really know why the quote uses Heathrow, but the same horizontal level so maybe OK.

Martyn1981

silvercar wrote: »

Wow, so many responses.

Looking again the quote is for 16 panels, but the diagram has a 9 and an 8 for the 2 roofs, so maybe 17 in total - I assumed the 9 should be an 8, but it could be that the 16 should be a 17.

orientation is -20 and +70.

I'm 30 miles from Heathrow, so I don't really know why the quote uses Heathrow, but the same horizontal level so maybe OK.

Sounds good, can I be cheeky and ask the price?

+70 is WSW, but will be almost identical to -70 ESE.

Presumably the 17 is a mistake, unless the installers are hoping to get you the upto 4kWp rate based on the DNC of the inverter at 3.6. My money is on a typo, and 2 banks of 8 panels.

You'll be generating big till 9pm in June!!!! Lucky .....

Mart.