Solar panels on a Grade II listed house

[Nigel Watts]

I wrote to my Council planning department recently to ask how they would view an application to install solar panels on my roof (4 storey, Grade II, 2 bay 1840 stucco semi in a North London conservation area). The new Welsh slate roof, laid about three years ago, faces just east of south at the back.

The Council have said that they won't allow anything on the front roof but the back might be OK, so long as it doesnt stick out more than 8cm from the surface of the roof.

Sor far, so good.

Now I need to get a firm interested enough in the job to give me an estimate and do some drawings to submit to the CO. I am thinking of hot water, rather than electricity (my son's survey of our CO2 emissions shows that we cause more to be omitted through the use of gas than electricity - and in any event green electricty can be made off site, as it were). I am thinking evacuated tubes rather than flat panels.

I havn't been much of a tree-hugger to date so am quite new to this saving the planet lark. Any ideas on suppliers, systems, pitfalls etc gratefully received.

 

[skier-hughes]

http://www.greenbuildingforum.co.uk/newforum/
http://www.powerswitch.org.uk/forum/index.php

May be useful to you?

 

[Penners]

Nigel - sorry but I can't be of any help at all. However, I would be very grateful if you would keep this thread running throughout the project, and give us periodic updates on how you proceed, as I'm very interested in such a project for the future.

Among the many questions that are chugging around my head is: how do you attach the panels to the roof? Do you have to take mounting brackets through the roof skin and bolt them to the rafters? If so, this presumably carries the risk of leaks around the mounting points, if they're not properly constructed.

 

[AMc]

I have been reading up on Green stuff (The Green Builders Bible, numerous websites). A couple of things I've gleaned about solar...

There is more demand for 'green electricity' than supply so most green tarrifs are actually trading in carbon credits and investment in future production not actually using green power today. http://www.good-energy.co.uk is the only UK provider currently guarantying 100% renewable production (no connection other than my lights and hoover seem to work as well with their juice as EDFs).
So if your roof space will accomodate PV panels they do have some use in lowering your personal CO2 footprint.
As fuel prices increase you may find the cost is offset in the useful life of the cells (20 years) and the invertor (10 years) if you have the capital available. Solar PV is quite expensive so only really economically viable if you have the money handy - not worth borrowing for from an economic view IMHO.
Solar PV tiles look pretty interesting to me, but I'm about to reroof. If you've gone to that expense then the bolt on panels may make sense (roof lines and conservation considerations being equal).

With solar water heating, the evacuated tubes are more efficient than flat plate collectors but have read some concerns about the long term durability of the seals. If the seals fail then the system becomes a lot less efficient. I've never left a vaccum flask on my roof for 20 years to know if that is just nay saying or is a real risk.
The equivalent flat plate collectors are reputed to be more long lived and are cheaper because they are simpler albeit a bit less efficient. As one installer said on another forum "I don't think my roof tiles are that pretty so I just install a larger flat plate collector to make up for the loss in power".

If you have enough roof space to accomodate flat plate collectors you may find that it's cheaper to fit more panels to meet your hot water load than a smaller evacuted tube system. Of course your welsh slate roof is probably a bit different to my 1970's concrete reroof.

Just some things you might want to consider.

 

[Nigel Watts]

Thanks

The more I read about green electricity supply the more chaotic it appears. It seems that suppliers get some kind of green certificates from the Government based on the amount of renewable capacity they have. They seem able to sell their green electricity to customers (at a premium) and then sell the certificates for the same electricty to another supplier who can then use them to claim that more of their electricity is green than it really is and sell this (at a premium) to another set of unsuspecting customers. In other words green electricity can be sold twice. If Enron were still in business they would probably find a way of selling it a third or fourth time as well.

Notwithstanding all this, it is clear that in principle green electricity can be generated remotely and piped in (and it seems likely that this may be more efficient), but with heating fuel it is more difficult, especially for those of us in a tight urban envirnoment with limited space for bio mass boilers, heat pumps and the like.

The costs of installation may be fairly hefty for me because of the requirement for scaffolding (house is very tall and narrow). Maintenance will also be difficult for the same reason. Robustness therefore will be important. Your comments about flat panels vs evacuated tubes in this regard are helpful.

 

[Penners]

AMc may I ask you a few questions about your comments above (Nigel - I hope you don't mind)?

PV panels they do have some use in lowering your personal CO2 footprint. As fuel prices increase you may find the cost is offset in the useful life of the cells (20 years) and the invertor (10 years)

Has anyone done any kind of total carbon audit on PV panels? Do we know for certain that, cash payback aside, they do actually save more carbon than is created in their manufacture, installation and ultimate disposal?

Do you know of any website where I can see detailed information on how the various types of solar panel are designed and constructed? If there's information on DIY construction, so much the better.

Many thanks

 

[Mark]

Have you looked at the navitron site and forum ?

http://www.navitron.org.uk/solar_collector_panel.htm

http://www.navitron.org.uk/solar_panel_installation.htm

 

[Penners]

That's a really useful site. Thanks, Mark.

 

[biffvernon]

Ecotricity are different from the other 'green' electricity suppliers. They are a generation company as well as a distribution company. Profits go to building more turbines so your bill payments actually make a difference to the total renewable generation capacity.

The economics of solar pv does rather depend on the future price of energy, as AMc pointed out. The Germans clearly think it's worth it. There are 37 factories making solar pv cells in Germany and 2 in Britain - and those two sell most of their production to Germany! The Chinese, of course, are the world's largest producer of pv, Japan and USA being third and fourth. Pv production is expanding at an amazing rate but the high price looks set to be maintained by demand outstripping supply for several years to come. Don't expect the price to drop next year.

Navitron seem to be the bargain basement end of the Chinese imports but may give good value for money even though some of the stuff may not be the highest spec.

 

[Mark]

I know navitron are at the cheap end with their Chinese imports - but the chinese did invent evac tube units. And their prices are *very* cheap compared to many of the suppliers.

I have to say that I find the info available very confusing - you have to know who funded the studies and know what is sold by whom. The flat panel people say that evac tubes loose vacuum, the evac tube people say that efficeincy of flat panels is so poor that you get no benefit for much of the year in the uk.

There is a swiss (I think) body that certifies solar thermal and pv equipment, but the only things I have seen from them has been certificates - we do really need a comparison of real world useage.
Worrying as well how many solar energy suppliers seem to be done by trading standards for overstating the benefits and overcharging.

I agree with Penners on the PV issue - I'm sure they have improved but I remember reading that the energy used to make them was more than you could expect to get out in their lifespan.
Do I remember that there is a CO or BCO somewhere with a PV roof ? £30000 worth of solar tiles ?


I am told that most solar kit is cheaper in France - lots of people in very rural locations are either off-grid or connected to a very unreliable ggrid means that there is more call for the kit.

 

[Flyfisher]

I agree with Penners on the PV issue - I'm sure they have improved but I remember reading that the energy used to make them was more than you could expect to get out in their lifespan.

That must surely be the crunch issue; all the financial savings in the world don't really matter if the technology cannot repay its embedded energy costs.

I've heard similar things about wind turbines. It must take huge amounts of energy to build an offshore windfarm, I only hope the designers can be sure this energy investmet will be repaid.

 

[biffvernon]

I remember reading that the energy used to make them was more than you could expect to get out in their lifespan.

No. Energy payback for pv is a very few years and getting better. This is, I think, a pretty reliable source:
Energy Bulletin

Modern large wind turbines are even better, repaying their embodied energy in well under a year.

 

[NT]

I have to say that I find the info available very confusing - you have to know who funded the studies and know what is sold by whom. The flat panel people say that evac tubes loose vacuum, the evac tube people say that efficeincy of flat panels is so poor that you get no benefit for much of the year in the uk

Both are correct in some cases, but there is more to it, particularly re the flat plate comment, there it depends entirely on design. Many designs do make use of flat plate output in winter, and in fact make more use of it than vac tubes. Each is better than the other in some respects.

Worrying as well how many solar energy suppliers seem to be done by trading standards for overstating the benefits and overcharging.

Major problem imho

Energy payback for pv is a very few years and getting better.

No... if only. Panels and systems are 2 different things, and the systems struggle to ever pay back, either energy wise or money wise. Nigel's right to steer well clear of PV.

Modern large wind turbines are even better, repaying their embodied energy in well under a year.

yes, just a shame it doesnt translate to small turbines in inhabited areas though. Wind speed is far too low.


NT

 

[NT]

this answers some of the questions and more:
http://wiki.diyfaq.org.uk/index.php?title=Solar_Thermal

NT

 

[biffvernon]

No... if only.

Perhaps you'd like to back your contrarian opinion with a reference to a peer-reviewed paper like I did?

My reservation about the Energy Bulletin paper is that it was published almost a year ago and reports earlier research. Pv technology is moving at a stunning pace and it is hard to keep up with the developments but one can be confident that change is in the direction of greater EROEI as cell production moves away from being a byproduct of the computer chip industry and into large scale dedicated pv lines and as film technology takes up a significant share of the market.

NT, you're right to warn about the cost of 'systems'. Adding the price of inverters and sophisticated control gear to hook into your mains supply changes things. When pv is used for low voltage DC lighting, for example, the economics are more favourable.

 

[Craig]

Tell you what, I am going to do this - we are replacing our tanks, so now is the time to put a pair of these wtaer heating tub arrays on the roof (we have a central valley gutter facing west/east).

 

[AMc]

Good luck Craig, take a bit of time to research the systems available as there are significant differences in people's reported experiences and some variation in technology - 1 hot tank, 2 hot tanks, flat plate collectors, evacuated tubes...
Please post your experiences too!

 

[Moo]

Pv technology is moving at a stunning pace and it is hard to keep up with the developments

So it's probably a good idea to wait a year or so before investing in it.

 

[Penners]

Modern large wind turbines are even better, repaying their embodied energy in well under a year.

The pub about 300 yds down the road from us has just put up a 6kW wind turbine. It's been fairly whizzing round during the last few days.

Of course, planning consent to erect is was a nightmare for the publican. NIMBYs up in arms all around the place. Neighbours were dropping notes into our letterbox urging us to protest, because the thing was going to slaughter the local bird population, deafen us with its noise, and scar the skyline, so depressing property prices throughout the village.

The result? You can only glimpse the thing from certain nearby viewpoints; you can barely hear it; no stack of bird corpses; etc. etc.

 

[skier-hughes]

no stack of bird corpses

But has Pie just gone on the menu :lol: