PV- Is there a business case ?

[Chri5]

About 5 years ago I finish this

Untitled

• Chri5
• 1 May 2010
• 1

The loft conversion gives a flat roof space clear to the skyline aside from the RHS stack. From the balcony look outward to the garden is direct south which allows for a continuous pool of sun all day - when it's sunny.

Flat roof space is 7m x 6.5m or 45 odd sq metres.

The PV tariffs for domestic generated PV are

System Type Size Rate/kWh
Solar PV 0 - 4kWp (new build) 36.1p
Solar PV 0 - 4kWp 41.3p
Solar PV 4kWp - 10kWp 36.1p
Solar PV 10kWp - 100kWp 31.4p
Solar PV 100kWp - 5,000kWp 29.3p

So say I went with a 12 panel (175w each) system that would generate (my cals could be flawed):-

5 hours sun per day x 175w x 12 panels x 365 days per year- 3800 odd kwh

Say I use 30% of that and sell the rest back

2500 kwh x 41.3p means £10k per year back from the grid. The 1300 kwh I use would knock a modest £130 a year of my current usage costs.

I understand panels can be found in trade for £400 odd each (can anyone confirm a source / supplier offering trade costs ???).

So say £5k for panels, 2k for inverters and installation costs- £7k total.


If the above were true then we'd all have PV !

What do I need to buy and leave on the roof to allow some sensible measurement of sun strength and light hours ?

 

[nozspark]

Firs off the Feed in Tarriffs are actually a generation tarriff, you get paid for what you generate (even if you use it). --- this is your 41p/kWh

Then you have the export tarriff, this is where you sell your un used electricity back to your supplier --- i think you get about 13p/kWh for this

I also think that you are being a bit over optimistic on your 5hrs / day (at full output) for 365 days a year..you will only get the maximum output on a clear Summers day.. if it's at all cloudy then the output will drop.

I have just read a Guardian article on this and they claim that the actual cost of installation of PV over a 20 year period is £600 deficit when you take into account of installation costs, payback and interest lost on the installation money..

TBH I think PV is a daft idea in this country.. wind turbines are probably a much better return on investment

 

[maltaron]

Unless you have at least 30 yrs working life left, solar power is a non-starter. A 2k system will cost in the region of £30,000 and it has been calculated that payback is a minimum of 20yrs. Your flat roof will be less efficient than angled roof facing South. Invertors for grid feed are extremely expensive as they have to be accurate sine wave generators and the cost is increased probably at least 2 fold for approval by the powers that be. Grants are available but you have to have highly efficient insulation and double glazing etc and pay for a consultant to advise, and also the system will have to be installed by an approved contractor, so most of the grant goes in paying the consultant and the overpriced installer.

 

[bongos]

I also think that you are being a bit over optimistic on your 5hrs / day (at full output) for 365 days a year..you will only get the maximum output on a clear Summers day.. if it's at all cloudy then the output will drop.

I think you're very unlikely to see that sort of sunshine - even in the sunnier parts where you live Chri5.

 

[ajstoneservices]

Chris you do have your sums wrong.

A 2kw PV system will cost between 10-15 grand installed on your house.Prices vary wildly for no good reason other than what a salesman can get for it.

A 2kw Euorpean manufactured system supply only under £7500 http://www.solarsavings.co.uk/product/2kw_MCS_Approved_Grid_Tie_Complete_PV_kit_PVK-05903

 

[electronicsuk]

I think that if you can get the kit at trade price and install it yourself, there probably is money to be made. However... as I understand it, the generation tariff is government funded with the intention of encouraging use of renewables. This means that they could remove the funding at any time.

 

[ban-all-sheds]

AFAIK you can't get the FIT payments if you DIY it - has to be a registered installer.

Chri5 - how do you heat your water? Do you store it?

 

[ajstoneservices]

You do have to use an mcs approved installer and kit to qualify for the FIT. One doesnt have to come with the other though. There are a growing number of installers happy to install customer supplied kit.

.

 

[Chri5]

I also think that you are being a bit over optimistic on your 5hrs / day (at full output) for 365 days a year..you will only get the maximum output on a clear Summers day.. if it's at all cloudy then the output will drop.

I think you're very unlikely to see that sort of sunshine - even in the sunnier parts where you live Chri5.

Oh Dear- I defo need to run a lighting measurement for a few seasons !

AFAIK you can't get the FIT payments if you DIY it - has to be a registered installer.

Sounds like a course cost could be justified- surely self installation could be done if I qualified to do the work.

http://www.niceic.com/en/contractor/article.asp?SECTION=15&ARTICLE=85

http://www.niceic.com/library/Microgeneration-Certification-Fee-Schedule.pdf

Chri5 - how do you heat your water? Do you store it?

CH + HW stored (traditional system with header tank)- Will update boiler to condensing unit in June, and plain to update to a 2 coil stored HW tank in the next year so the potential is there for Solar heated water.

I've seen 2.1kw systems with all the add in items for sell back for £12k so where the £30k system came from I don't know

I'm sure someone posted recently about 175w panels being sub £400 each, but as newer technology it's anyone's guess as to what the panel service life is. If they were throw away at 10 years then that kills any justification for an installation (unless you are a die hard green and do it not for cost, but for carbon neutral status).

We do get bright days, and with global weather change I'd guess more and more.

If each panel 175w gets 600 sun hours per year it generates 105kw per year or £41 of tariff which sort of makes it near impossible to work on the financials alone

 

[ColJack]

don't forget that for optimum efficiency you'll have to get up there twice a day and squegee the dirt, water spots, bird poop, road film etc off them...

 

[Chri5]

don't forget that for optimum efficiency you'll have to get up there twice a day and squegee the dirt, water spots, bird poop, road film etc off them...

So self cleaning glass doesn't work

 

[ColJack]

not layed vitrually flat when a bird craps on it...
self cleaning glass in a window doesn't even work that well, you still need a window cleaner every few months to get the road film off..
at anything less than upright the water won't run off as fast and may bead up in places..

 

[ban-all-sheds]

the potential is there for Solar heated water.

That's the best way to make use of solar energy, as it will also work (to some extent) on hot overcast days, and hot nights.

We do get bright days, and with global weather change I'd guess more and more.

Our local weather may not get warmer. We are on the same latitude as Hudson's Bay - if the Gulf Stream shuts down.....

If each panel 175w gets 600 sun hours per year it generates 105kw per year or £41 of tariff which sort of makes it near impossible to work on the financials alone

Based on a system lifetime of 25 years the cost of the PV generated electricity
was found to be between 20.9p/kWh and 184.7p/kWh with an average of
47.5/kWh. If known underperforming systems are removed, the average and
maximum costs are 39.1p/kWh and 77.8p/kWh respectively.

OK - that's based on a study done 5-10 years ago, and I'm sure that technology has improved and got cheaper since then, but I still think that PV is a chimera, and a much better ROI is obtained from solar heating of water and/or spending the PV budget on better insulation and heat recovery.


Also see http://www.ibpsa.org/proceedings/BS2009/BS09_0789_796.pdf

 

[ajstoneservices]

BAS,
I'd be interested to hear of a solar thermal system that works at night( I'm making an assumption you meant when dark).

 

[mointainwalker]

If you'd like a rough comparison of sunlight and output.......

I live in the N French Alps at 1500 m, 60 -80 km away from significant industry so the air is very clear. On top of that , we get 200- 230 sunny days per year.

A neighbouring farmer has just signed up for 160 m2 pv panels on his (directly)south-facing roof.

The cost of this is about E 100 K (pnds 90 K) and given the feed in tariffs which are about 50 cts kWh ( don't know about self/use/export ) i.e. similar to some figs quoted above - his calculation is pay-back in 9-10 years and since the farmers associations are giving members assistance in calculating yields/sourcing equpment etc, I would guess that's fairly reliable.

Since we also get a lot of sun in winter when the UK is usually under leaden-grey skies for weeks at a time, I would find it hard to believe that a UK user could get even 50% of my neighbour's (planned ) output, so maybe the Guardian got something right for once

This is not just a first leap by him into solar, he has had 6 m2 of solar panels which heats a 350 l tank ( lots of water needed for cheese- making ) for about 5 years already.