Split PV arrays

[Glen Powell]

My big problem with storage heaters is they have not moved on in decades, in most properties they are actually being ripped out rather than installed, we all know electricity is the future, this is why we are in this forum. Other forms of energy are equally viable, wood burners or other similar technologies are sneared on by the uneducated for causing polution, for being inefficient, la, la, la.

Burning wood or coal for electricity is not efficient if the power source is 50 miles away with outdated turbines, however heating the home is very efficient, if you get loads of junk mail more efficient still (with a bit of time and effort), smoke / polution means you are burning rubbish and not the recommended seasoned fuel with little moisture content or you have not maintained your flu as well as you should.

Airsource requires oversized radiators but buy a good airsource designed for the UK then you will be a happy bunny, providing you have insulated to the best of your ability first.

 

[Gavin A]

Yes, but being on E7 means that any power they use in the daytime is more expensive.

From memory of what they said, it's 7p night rate (1am-6am) and 15p day rate. Not being on E7 would be a flat rate of 13p.


Solar might not make a big contribution to their winter usage, but they can "get their money back" during the summer when the solar panels will be working hard. They also won't have as much higher-priced daytime power, such as for cooking, mowing the lawn, watching TV, and many other things which can't be done on E7.

At 21p FiT (and 3.1p export), 3000kWh is £677 per year of payments, plus some reduction in their daytime-usage bills. The "investment" in PV would probably give them an annual return of RPI+3%, plus some bill savings, which isn't bad.

My "usual" electricity payment is a direct debit for just under £40 per month, but that looks like it'll soon be reduced to £20 per month based on my usage so far. So, by being reasonably energy-conscious, I actually appear to be able to use half of what I have generated since mine was installed a few months ago.

makes a difference, but also bear in mind that a significant proportion of the north sides generation will be between around 3am-6am in summer, which may well negate the impact of that extra 2p daytime rate.

I'd not totally discount this idea, but would say you need someone to work up some pretty detailed output and performance projections for various times of day at various times of year to prove the concept, as well as the costing side of things.

We have done north east / north west facing roofs to compliment eg south east / south west roof installations on dual MPPT inverters, and the decrease in the cost per kWp, combined with increased inverter efficiency from using eg Aurora or SMA TL dual MPPT inverter vs a single smaller inverter (1-2% advantage), can in some circumstances outweigh the reduced output for the North East / North West facing array in percentage terms, but each situation is different and it's usually fairly marginal.

 

[FB.]

If I cost it at "best guess" retail prices with low-middle range panels........

2kWp North + 2kWp South.
Fixed costs: £5k (inverter, scaffold, wages etc)
Panel costs: £4k
Total cost: £9k.
Total annual generation: 3000kWh
Cost per annual kWh: £3.00

2.5kWp South
Fixed costs: £4k
Panel cost: £2.5k
Total cost: £6.5k
Total annual generation: 2200kWh
Cost per annual kWh: £2.95

So the split array seems to be practially as cost effective as the single array. The bonus being that the split array has a longer period of reasonable generation each day, will cope better with cloudy days, plus a higher total annual generation; therefore more to offset against bills at 15p per kWh and higher FiT payments.

I guess the main reason for this topic is that it's such a close call from what I can see.

.

 

[sedgy34]

I would go with south and using 8 suntech 280w modules 2240kw system or find a 300 module.

 

[Earthstore]

If panel choice is the problem, I would use sunpower, as you can produce far more from a smaller area,
But then I would as I can supply these, they are not on the open wholesale market.

 

[jupestar]

Hi FB.

It seems you've done the analysis (assuming correct performance figures) and now you've come to a decision which is a client decision not really an installer decision. Now it comes down to other considerations.

Capital outlay.
Aesthetics.
Possible alternative use of roof space.
Weight on roof.

The only thing i would say is that you are considering first years returns only, i know this is correct from a sales view, but it is worth considering your return 5/10 years down the line if you think power prices are going to increase quicker than RPI then a system producing more electricity will start to give extra returns as a higher proportion of the total return will be savings (if they use the energy).

 

[sedgy34]

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