Solar

rogerblack

Martyn1981 wrote: »

Hiya Roger, unfortunately, the FIT rate is based on the kWp of the panels.

This flies in the face of the legislation, describing the maximum continuous output the system is capable of, but OFGEM aint budging, and nobody wants to incur the legal bill of challenging it.

Ok - I was assuming they would stick to the relevant legislation

Interesting - just found the recently published:
http://www.ofgem.gov.uk/Sustainability/Environment/fits/Documents1/FIT%20generator%20guidance.pdf
Which on page 10 confirms the definition of Total Installed Capacity and Declared Net Capacity. (Which are in agreement with what I was thinking - if the inverter is 4kW - then the installed capacity/DNC can never be over 4kW - as the output of the whole installation cannot exceed 4kW.
2.21 also says that derating a system is in principle possible.

http://www.ofgem.gov.uk/Sustainability/Environment/fits/Documents1/Generating%20equipment%20decision.pdf - states that both inverter and solar panels are the 'generating equipment'.

The first link also gives a handy email address - which someone should probably contact first.

penrhyn

There is nothing ethical in reaping Fits from solar, resulting an increase in energy costs for the rest of the population.

Wh05apk

penrhyn wrote: »

There is nothing ethical in reaping Fits from solar, resulting an increase in energy costs for the rest of the population.

Thankyou for your contribution.

penrhyn

You are more than welcome. Nothing wrong with getting a decent ROI, on solar, but its just as exploitative as any other scheme, calling it ethical is just green wash.

Wh05apk

penrhyn wrote: »

You are more than welcome. Nothing wrong with getting a decent ROI, on solar, but its just as exploitative as any other scheme, calling it ethical is just green wash.

Totally agree, I am sure the energy produced will never replace the energy used to manufacture them either, but governments like to feel they are reducing CO2 emissions, the reality is that CO2 production is displaced to china where the panels are produced, but in the meantime I get a 15% return on my investment guaranteed for 20 years (subsidised by everyone else without panels) it is a total con, but while it is legal, I will do it!

penrhyn

Very well stated.

Martyn1981

Wh05apk wrote: »

Totally agree, I am sure the energy produced will never replace the energy used to manufacture them either, but governments like to feel they are reducing CO2 emissions, the reality is that CO2 production is displaced to china where the panels are produced,

Energy payback is estimated at between 3 and 7 years depending on the type of panel and location (California v's UK). Carbon payback times are tricky, but similar. Compared to panel life expectancy of 30+ years.

http://www.nrel.gov/docs/fy04osti/35489.pdf

http://info.cat.org.uk/questions/pv/what-energy-and-carbon-payback-time-pv-panels-uk

Mart.

sugarwalsh

Thanks for your help.

Martyn1981

sugarwalsh wrote: »

Thanks for your help.

Sorry Megan, I never did get back to you.

Right quick run through.

2,789kWh's pa works out as

FIT income 15.44p*2789 = £431
Export income is estimated as 50% of generation, so 4.64p*1395 = £65
Leccy savings estimate of between £80 to £160, but as you'll have a long generation of East and West, plus your leccy consumption looks a little high, so lets guess at £150, but please, it's only a guess, don't shout at me if it's wrong!

Total £431+£65+£150 = £646pa


Cost, I reckon you need to get hubby on the case and try to get it down to £6k or less. Until recently I'd have said try for even lower, but prices may be going up a little with the current Chinese panels v's EU problems. Plus if two roofs, the scaffolding costs may be a little higher.


8 panels east and west, as mentioned by Roger, you shouldn't need two inverters, there are lots of top quality inverters that can run 2 roofs separately. Inverters have a thing called a MPPT which tracks the best voltage levels, for two roofs with different orientations, you'll need an inverter with dual MPPT's. Sorry for the jargon, but this is important. When you get a quote just post the specific make and model of the inverter on here and I(or others) will find a link to the tech sheets and show you whether it has the necessary MPPT's.


Payback, this gets tricky now, it will depend on the final cost, and on the cost of the finance. Happy to have a go for you, but might be better when you have a few more details.

At the moment, if the cost was £6,460 and the interest rate 10%, then your £646 would only finance the interest, and never pay off the debt.

Or, if the cost was £6,000 and financed through a mortgage extension at 5%, then (simply) in year one £300 would go as interest, and £346 to repay the debt. With a reducing debt, payback takes about 12 to 13 years. But you may need a replacement inverter around that time too at a cost of about £800-£1,000 pushing payback towards year 14.

Hope this is a start, sorry for the delay, any questions just ask away.

Mart.

Martyn1981

rogerblack wrote: »

In principle, you could use a 4kW limited inverter which can cope with two banks of panels, and two 3kW arrays (12 panels) on east and west.
You will never (?) get the sun directly shining on both the east and west at the same time - so the inverter will never reach 4kW (or very very rarely), but the generation will be better spread over the day.

Hiya Roger, can I add some real life experience. This isn't meant as a criticism, more a follow on from our chats about going over 4kWp and the pro's and con's.

Firstly, a year ago I would have agreed with:

"You will never (?) get the sun directly shining on both the east and west at the same time - so the inverter will never reach 4kW (or very very rarely),"

When I was considering my WNW extension last year, I wasn't able to run all systems (2 existing + 1 proposed) through a single inverter, so wasn't able to fall back on an inbuilt 3.68kW limit. Hence why I had to get DNO permission (Western Power Distribution).

I was able to chat with Brad, the local PV contact for my area, and he was absolutely brilliant, a great help. We both agreed that the systems would hardly ever reach 3.68kW, especially as I have a large chimney straddling the middle of the semi roof, and to the South of all panels.

But .... WPD rules were that they can't take orientations, roof pitches, shading etc into account as it's almost impossible to calculate/estimate even on a one by one basis.

So, I was shocked the day after the extension (end of July 2012) to see generation hit 4.2kW sustained from 12 to 2pm (11am to 1pm GMT). Approx numbers went from 3.2kW ESE + 1kW WNW around noon, to 2.8kW ESE + 1.4kW WNW around 2pm.

I did phone Brad and had a chat about those surprise numbers, and we both agreed early days for PV, still living and learning.

System started hitting 4.2kW again late Mch, and has hit a semi-sustained 4.5kW recently, with short spikes of about 4.9kW.

I still can't quite get my head around how the WNW system can start to hit 1kW, when the sun is barely skimming their surface, and mostly shining on the upper frame edges (if that makes sense?).

I suspect the system will be able to sustain 4.5kW throughout the 2 hr period (on a good day) somewhere within the 6 weeks either side of late June. I shall be watching with interest.

Whether or not the losses of capping to 3.68kW are significant, gets tricky, but I'd assume little to no concerns up to 4.5kWp (split E/W), and acceptable losses up to 5kWp. But growing losses from there up, on good days during BST 6 month period.

I don't know if this would cause offence to a DNO, but one idea might be to slap 5 or 6kWp across E/W with a suitable inverter, say 5kW and a 3.68kW cap. Then apply for permission to un-cap it later on. Or review in future if supply changes - prior to Mch 2012 I wouldn't have got permission, but our area was re-cabled and houses are no longer on a loop with a neighbour (my basic understanding!), so this could happen to others in the future, and shouldn't(?) affect FITs since the system will have been registered at the kWp rating.

Steeper roof pitches (mine are 30deg main roof and 20 deg smaller, lower roof) would minimise capping, but steep off south roofs don't generate as much per year.

As I said, not criticising your assumptions, I had exactly the same (as did those I discussed my ideas for an extension with), but real life experience surprised me.

Loads of numbers, info and musings if you want more.

Mart.

PS Current gen 10.35am 3.4kW ESE + 0.57kW WNW. With spikes of 3.6kW + 0.7kW. M.