PV roof tiles

[sarahj]

We live in a g2 stone cottage. We are planning ato put a pitched roof on the 180s flat roof extension and would like to include some kind of solar heating as part of a range of alternative energy supplies. does anyone here have any experience of using the solar roof tiles, and have there been any problems installing them on a listed property (albeit not on the front or the old bit). Some of the companies I've found say their solar roof tiles are suitable for listed/conservation area buildings - what do you think?

 

[Nemesis]

I'd say they would say that wouldn't they, and it would all depend on the listed building or conservation area concerned!

 

[NT]

Surely if its listed you cant replace the roof with a different structure. Or has this somehow got lbc?


There are 3 main types of solar systems.

1. PV - a total waste unless you live a long way from the nearest electricity mains

2. Solar DHW - some systems pay their way eventually.

3. Solar space heating - this is the one category that pays back well, and is worth installing on any building that will take it. However I cant see it going onto a listed bulding!


The only solar tiles I know of are solar PV cells, which will be of no use to you.


NT

 

[Stephen]

We are presently installing a system on a property and have done some research into this.

There are two forms of solar system: Solar Energy Panels creating energy in the form of heat and PV panels creating energy in the form of electricity. Both appear as a form of dark grey panel and should ideally face south or as close to south as possible.

If considering the energy output as kW hours - to deliver the same kWh ouput far more PV panels are required than solar energy panels. Realistically a roof covered with PV panels would be required to deliver meaningful output converted to electricity. However, to deliver output sufficient to provide 70%-80% of hot water requirements for a modest house 2 or 3 solar energy panels are required (because hot water requires far lower kWh energy). Further, the cost of solar energy panels is far lower (c. £4,000 - £5,000 for 2/3 panels) compared to over £20,000 for a lower kWh output in PV panels.

You must therefore consider carefully what you want to achieve. If you seek an alternative energy source for hot water solar energy panels would seem a practical and reasonably economic option.

If you are seeking energy for electrical output the number of PV panels and their cost is probably not realistic for most domestic situations.

When considering alternative energy sources also look at ground source heat pumps, wind turbines (they now come in 1m diameter 'kits' for domestic use), bio-diesel (in oil boilers or generators). Each source has its unique factors, but also disadvantages.

If you are looking for electricity consider wind and perhaps bio-diesel generators (although subscribing to a green supply company would probably be better). If looking for heating solar energy panels would be a poor option unless for underfloor heating (requiring a low temperature input); ground source pumps are again best used with underfloor heating. In both instances they work best with high levels of insulation. If installing in an existing building (especially a listed one) you have to question whether the levels of insulation required can be provided to make these systems effective.

If you are looking for an alternative hot water system solar energy panels are practical, do not require additional insulation, etc and are therefore a sound and effective option. The main problem is that they work most efficiently when facing south and with a short run between the panels and hot water cylinder.

The problem with most of these is the impact on appearance and in some instances you will need not only listed building consent but planning permission as well (e.g. for a wind turbine).

Perhaps an advantage of the panels (PV or solar energy) is that they look (from a distance) a bit like skylights.

The above comments are of course a very brief overview based on my recent research and thinking. I am very keen to look at alternative energy systems and with ever increasing costs of energy as well as impact on environment it is advisable that we seriously consider such matters. However, let us cut through the hype of some of those trying to sell these systems and consider realistically what they can and cannot do.

I would be very interested to read of the experience of others.

 

[NT]

Solar space heating costs are around a tenth of the prices quoted above. And deliver a good 10x the output of solar dhw.

NT

 

[worms]

Sounds good, NT! Can you explain more? Are we talking passive solar gain? ie big windows on south facing elevations? Or something more complex?

 

[L1zzy]

Just thought I'd mention that I was listening to a programme on radio 4 in the last 3 weeks regarding plans for introducing some sort of more relaxed approach regarding installation of energy saving devices such as Wind turbines in domestic situations. If I remember the Government is planning to waive the need for planning permission for these devices and I think its due to be in 2007. I'm sorry I can't remember more details but thought it worth mentioning

 

[Mark]

Gosh Stephen. You're paying quite a premium for those flat collector panels. Evac tube collectors are far more efficient and can be had for less than £500 per panel. I will shortly be fitting evac tubes and expect to spend less than £2000 for the complete system (hot water only) including replacement hot water cylinder with multiple coils.

NT - Im interested in your comments about the solar space heating - I thought that you needed to have huge collector areas for this if you want to keep hot in winter ? I thought gshp was a better bet - although I know that ice energy are talking about using the gs loop as a thermal store and linking solar collectors into it.

The planning side of things is a mess. the odpm ,or whatever thay are called this week, have said that solar panels etc should fall into the category of permitted development. The local planning authorities dont agree though. Ours are asking for sketches and have case law guidelines coveringh the size of the panel (very interested in how they sit on the roof) You might also need building regs approval. some panels are quite heavy.

 

[Stephen]

Mark

Tell me more.

I have seen solar energy systems (yes the eVac) where they have quoted £7,000 + and the ones we are presently having fitted for a client come in at £4,000 ish. This does include a dual coil insulated hot water cylinder plus pump, full fitting, etc.

Can you point me to a source for cheaper quality supplies, installation, etc.?

Stephen

 

[Mark]

Stephen,

the discount source is http://www.navitron.org.uk have a look in the online store at the package prices £1100 for tank and panel kit

Speaking to a couple of installers they say that the quality isnt up there with viessmann and such like (but its a fraction of the price).

There is a forum where you can contact installers and ask questions about the kit.

 

[plumbers mate]

This seemed an easy system for heating water by solar.

http://www.solartwin.com/easy_to_plumb_in.htm

It requires little internal work and the external panel on the roof is *supposed* to be OK for a listed building because it can be removed without leaving any trace.
(Like the temp wooden ramps you see outside some museums etc. ).

Last I saw they were about £2½ grand.

 

[sarahj]

I wasn't going to replace the current roof on the old part of my listed building - it is in beautiful condition bar a few chipped slates - I was going to put a pitched roof on the 1980s flat roof extension which is at the back of the property (40% of the footprint), and therefore I was looking at using solar tiles for the new roof. see here: http://www.solexenergy.co.uk/solarslates.htm Just about all of the properties around us have pitched roof extensions at the back so I think that would be allowed, its just finding a good looking solar roof tile to satisfy co/national park officer.

We are in national park and listed building so wouldn't get permission for wind turbine. Also two foot down and you hit solid granite in our hillside garden so I don't think groundsource heat pumps are an option either. They could be great for the village though in the field that runs the full length of it. We are however also considering sheeps wool roof insulation and a thick curtain for the front door!

 

[NT]

Here's a picture of some solar space heating:
http://www.builditsolar.com/Projects/SpaceHeating/solar_barn_project.htm
this should answer several questions.
For non-listed buildings these can also be constructed as not part of the building and the hot air piped in, but I doubt they'd get LBC.

The much larger collector area and much higher efficiency than water panels means far greater energy return. The fabric of the building, if dense like brick or stone, will provide partial heat storage, so the panels indirectly contribute heat after dark too, though less.

The construction cost is low, and ROI is excellent.


Sarah, IIUC you still need LBC to do what youre doing.

 

[NT]

Re evacuated tube solar hot water, there are 2 points of interest.

1. if youre fitting cheap vac tubes professionally, be aware that a power failure could cause tubes to shatter. No circulation plus concentration plus vacuum insulation equals very high stagnation temps, and low price equals glass that cant take the shock of a sudden return of cold water after 3 hours baking stagnant in the sun.

2. ROI is the critical issue with solar dhw, and ROI can be improved by use of lower cost technology where it will deliver effectively. If your hot tank is sufficiently stratified, you can heat the bottom section with flat plate collectors and the top with vac tubes, thus obtaining more energy at lower cost. Bear in mind omitting a small amount of vac tube buys you a lot of flat plate, and that means more energy harvest at the lower water temps at the bottom of the tank. Flat plates are poor performers for the top of the tank, but probably the best performers for the bottom.


Got to run, will check out the solar slates later.


NT

 

[NT]

Glass slating forming solar collectors is an idea I've found of some interest for a while. Its certainly a way to provide a large area of collector without compromising roof appearance, and it avoids the cost of a separate bolt on structure.

The downside is the slating wont be airtight, so its a poorly single glazed collector. Also the wood beams will react to the higher temps with more movement than normal.

The solex site has made some decisions I would question. First example is use of toughened glass rather than laminated. Lam performs much more satisfactorily under breakge conditions and is much cheaper, yet they chose toughened. The next questionable imho is the use of a water collector for space heating. Water collectors are much less efficient, and introduce a bunch of extra setup costs which are simply not needed for space heat.

If I were doing a new build I'd look into a laminated glass solar roof. I'd make it or specify it myself, cant see any reason to get an overpriced company involved.

Wired glass is a much cheaper alternative to laminated, but it does crack and doesnt look good once cracked. Fine for factories, but not the best option for a nice house. Cracked slates can be replaced, but in practice tend not to be.

Have you costed the glass slating? The viability of the scheme hinges on the cost, which I've not calculated.


NT

 

[sarahj]

I haven't costed anything yet! I'm waiting for the sale of my parents house (yet again fallen through) to get the capital to fund the renovation works. Most of the renovation is the 1980's extension - bathroom kitchen - although when I can face the mess I want to remove the blown vinyl covering lots of lumps and bumps to see what lies beneath. I'll be booking myself on on a SPAB course to help with this as I think I would like some of the stone revealed and limewashed.

Over the coming autumn and winter I plan to draw up plans and submit these for consent, I just need to have some idea of what is realistic. The hardest part is deciding what order to do everything eg wiring, plumbing, heating etc as I am trying to do these piecemeal as we can't afford to move out and I have a really 'helpful' three year old!

 

[plumbers mate]

Northumberland National Park has no problem with the Army taking pot shots at bastles etc (I know historic and archaeological features are marked with a star suggesting they should not be fired at but, this is the military .....) so why they should baulk at a small wind turbine is a bit of a mystery. It's incredibly sparesly populated, so there wouldn't be thousands of them popping up everywhere.

Northumberland also has some wind farms - not big ones, true but they may consider a small one-house sized turbine if sited so that it isn't too obtrusive?

 

[Nemesis]

I think you need to look at what is actually proposed with wind farms in rural Northumberland...

 

[NT]

Well, you need to draw up a rough design for your solarthermal roof and cost the materials. This will let you know if its an option or a non-starter.

Start with a quote for the lam glass, you can cut it yourself into slates. Glass area will be about 2x roof area for slate style. No need to grind the edges.

Fixing the glass slates with tingles would be a lot less work than drilling them, or you can drill hundreds of holes if you want.

then theres insulation under the roof structure. Then 2 air channels top and bottom for air in and out, a fan and 2 CH thermostats, and some boxing from roof to ground floor to create a ground floor outlet for the hot air.

What would it cost you?


NT

 

[Nemesis]

Then there's the hope that we get sun in Northumberland... and the thought that even on a new roof, it may not be considered suitable on a listed building.