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Posted: Sat Nov 08, 2008 10:40 pm
by ChrisB
NickJ wrote:
I think we may be straying off topic in this thread though! :oops:


Ah I wouldnt worry too much :wink:

While I can understand the whole no battery grid connected thing, I do have to question how many days in the year a grid connected system would acutally be viable in the UK :? and how much usable power and what the system would actually be powering during the day?

Is it more the case of supplying back into the grid rather than actually powering the properties that its installed in ??

It would really frustrate me having +1kw system sat on the roof and then after a sunny day having to use grid power because I havent been able to store any of the energy that the panels sucked up during the day :cry:

Not all batteries require topping up :wink:

I have just come home today from comissioning 4 off 1.3kW grid linked PV sytems on a group of social houses for rent, which would not have been installed by the housing association if they had involved all the hassle of batteries

The above sits very un-easy on me, and I have to wonder if its more a case of a certain .gov making it look like they are all green and clean, the fact that its not exactly that useful for the punters is irrelevant.

It would be interesting to know how many installs your doing for .gov or similar, compared to private individuals that are just plain grid connects with no storage ?


Posted: Sun Nov 09, 2008 1:47 am
by NickJ
A simple answer first... A PV system installed in the UK will give approx. 800kWh per kW peak in other works a 1kW system will deliver 800 units of electricity a year...a bit more in cornwall and rather less in scotland. In terms of what is powered and what is not it of course depends on your domestic usage. Most working people will probably export a small amount during the day and will of course absorb from the grid at night but two important points. Firstly most people with PV are on a tarrif which pays (usually around 10p) for every unit generated, irrespecive if this is used in the house or exported. Secondly the overall carbon efficiency of a grid linked system is higher than one with batteries (greater overall efficiency for various technical reasons). It may be the case that in future grid balancing issues will lead to systems with both grid and battery but this is not really beneficial at present.

As to the benefits to the tenants of the social housing I mentioned, they get a reduction of 100-200 pounds a year on their bill which is worthwhile I think. I have worked on many domestic systems which are not "goverment greenwash" including several 4kW systems (the largest practical system for most domestic users) which have been paid for privately.

Solar PV, however connected is not "cost effective" in cash terms in the UK at present and the pay back times are long. however it is "Carbon effective" and where grant aid is available , such as for social housing, it can deliver a substantial saving on domestic bills to people who need this most and whilst I agree there is much else that can be done in terms of energy efficiency we should not ignore the potential for both PV and solar thermal in the UK. I would refer anyone interested to "Zero Carbon Britain", a report from the centre for alternative technology. Woe I think this is my longest post!

Hope this helps allay some of your concerns Chris :)

Posted: Sun Nov 09, 2008 10:10 am
by qdos
NickJ wrote:Solar PV, however connected is not "cost effective" in cash terms in the UK at present and the pay back times are long.

That's the crunch really isn't it?

Solar hot water however can be done for free, OK maybe not the most efficiently but hey a set of scrap radiators painted black, an old water tank placed up high and hey presto! Free hot water for the milking parlour. Tweak this a bit more and you can heat your swimming pool for free too. I've seen both done by friends.

Sure we'd all love to have high efficiency solar heating, and electricity from PV cells and wind turbines on the garage roof but as you rightly pointed out, it costs money and there's precious little of it about these days. But as with computers the technology is gradually becoming more affordable and one day......... Image

Out of interest how close are PV cells to the cost of a roof slate? i.e. how much would it cost to have PV cells on the roof instead of slates? Are they durable enough to consider too?

solar hot water

Posted: Sun Nov 09, 2008 10:32 am
by robbymax
Hi the cost of your hot water system is still very high did they change your cylinder, are you on a vented system? a set of 30 tubes costs about £600, £100 for controller new vented solar cylinder with extra heat exchanger £700 the rest is pipework and lagging say £300, labour was a lot of money

Posted: Sun Nov 09, 2008 6:29 pm
by NickJ
The DIY solar heating route is great for anyone who is up for it. I did a system on my old house in leeds. The difficulty is of course that many people lack the skills etc to do the work and have to buy into a commercial system. I would however agree with robbymax that many systems for solar thermal are overpriced (this is less common with PV due to small profit margins and high cost on equipment supply). I am aware of solar thermal being installed for up to 10K following high pressure sales, for a system a freind of mine who is a heating engineer would put in for £2500 including a fancy new cylinder and all labour!

Living in wales and being aware of the price of slates (£2 each ish) PV panels can certainly displace the cost of slates, the problem is they then have to installed as "laminates" (ie frameless modules) into a glazing bar system, which is expensive! The Ubbink "Intersole" system ( ... 06FA5B.pdf ) allows slates to be replaced with a plastic tray system and allows the use of framed modules. It can save money if re-roofing is required on slate roofs but costs more than conventional "above the roof" solar mounting systems where fitted to an existing roof.

PV Modules have a 30+ year electrical lifespan but as waterproof elements in a fully glazed roof would last as long as any tempered glass.

For commercial buildings PV systems can often be cost effective compared to other cladding systems.

The bike shed at work has a curved roof made of PV laminates..Looks very nice!

Posted: Sun Nov 09, 2008 6:40 pm
by robbymax
I own a battery vehicle a berlingo electrique
I also own a battery home and I will tell you about it.Three years ago I started to get concerned about the rising cost of electricity.
And using the internet I researched solar energy, and thought I would have a go at designing a system for my bungalow the basic requirement being a south facing roof no problem got that.
How big would it have to be? Was sorted buy monitoring consumption daily for a month?
I decided to engineer an off grid system for maximum economy
And I will explain why, we don’t get enough sunshine all year round to run everything and when the batteries don’t get enough charge during the day I wanted to use economy 7 to provide any short fall and by using a time clock and my own switching system everything would work.
Three years later having spent £17,000 pounds the system is working fine. From March to September on good days the house is off grid and self sufficient but the difference between a good day and a bad day is enormous pv panels need unbroken sun light the smallest cloud makes a big difference on the charge readout so on a good day the best recorded was 523amps and the worst cloudy day gave just 32amps when the weather is bad I can set economy7 charge times To always allow
the batteries to start the day ¾ charged, but if I see the batteries becoming fully charged I just plug in the berlingo
Can’t waste any can we
This has been a learning experience and there were times when I thought I had bitten off more than I could chew, I have made some mistakes and if anyone wants to now I will tell them but there was nothing major.
Was it worth it?
All I have to do is save more on electricity
Than the money would have made in the bank
And what do you know interest rates have just dropped to 5%
And electricity has gone up.


Posted: Sun Nov 09, 2008 6:57 pm
by robbymax
Enlarge Image Retail Price: £ 1,319.15 (excl. Vat)
£ 1,550.00 (incl. Vat)
pitched roof mounting kit
twin coil hot water cylinder (up to172litre double insulated, grade3 with grade2 base) :-larger tanks incur additional cost
Tdc3 solar controller
circulation pump + isolation valves
anti-syphon valve
pressurised system kit;
10m armaflex ht high temperature - please select pipe size and wall size
(10m of 10mm copper pipe...if the 10mm option is selected)
5 litres antifreeze
Cylinder Size 1050x400 1200x400 1300x400 1400x400 1500x400 1800x400 +£60.00 1050x450 1200x450 1300x450 +£30.00 1400x450 +£55.00 1500x450 +£65.00 1800x450 +£115.00 Copper Pipe Option 10mm +£35.00 15mm 22mm +£7.00 Pipe Insulation Thickness 13mm 19mm (n/a with 10mm pipe) +£18.00 Compatible Productssolar flashing (for slates or tiles)
pitched roof mounting kit for 10 & 20 tube solar panels
filling kit (for antifreeze) - hand-pump
solar antifreeze
armaflex insulation 15mm (13mm wall)
over-voltage protection

Posted: Mon Nov 10, 2008 12:11 am
by qdos
Three years later having spent £17,000 pounds the system is working fine.

That's going to take a long time to pay back! And I doubt you'll be able to take them with you when you come to move house either.

So basically as a new or replacement roof it's worth considering but otherwise you have to really be a bit of a tree hugger to spend that sort of money on them. But maybe people could consider them as a roof for a new garage or extension?

Posted: Mon Nov 10, 2008 7:46 pm
by robbymax
qdos wrote:
Three years later having spent £17,000 pounds the system is working fine.

people spend £17,000 on a kitchen and it never pays you back and if you sell the house the new people dont like it and want a discount at least a solar system is an asset to the property and would help you get the asking price if you want to sell

Posted: Mon Nov 10, 2008 9:37 pm
by qdos
robbymax wrote:people spend £17,000 on a kitchen and it never pays you back and if you sell the house the new people dont like it and want a discount at least a solar system is an asset to the property and would help you get the asking price if you want to sell

Hmmm yes people do spend on new kitchens though I'm not sure I know that many who've spent that much on one and I do know some folk with million pound houses. Does it pay them back? well I suspect not though the TV programs would have you believe it does. It certainly makes it easier to sell a house though.

Would a Solar system do that well? That remains to be seen, the only people I know personally who had one are one of the folks with the million pound house and I'm pretty sure it made no difference to the sale. Their next door neighbours fitted a home made solar heating system for their swimming pool and that might add a bit on to the value but hey they built the solar system for naff all out of old plastic pipes so it's not hard to get your money back on that.

With fuel prices going through the roof and with the energy efficiency reports on houses well yes I can see people taking some note of free energy but will they pay £17k for something? You tell me you're the one selling them. I won't be in the queue though I'll be off to get my own hose pipes :wink: