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[PVpost] Small-scale (home) generation
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PVPoster1



Joined: 24 Nov 2005
Posts: 385

PostPosted: Fri Jun 24, 2005 11:56 am    Post subject: [PVpost] Small-scale (home) generation Reply with quote

This is an edited re-post of a topic that existed before the forums were hit by a virus in June 2005. Please feel free to add comments at the end.

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Domestic wood-chip CHP burners, and such-like:

http://www.homepower.com/

Solar water heating, with built-in PV to operate the pump. Note their solution does NOT work with combi boilers:

http://www.solartwin.com/
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PVPoster1



Joined: 24 Nov 2005
Posts: 385

PostPosted: Fri Jun 24, 2005 11:56 am    Post subject: Reply with quote

I have no personal experience of this, but someone on the AECB site (www.aecb.net Association for Environment Conscious Building), suggested that perhaps Solartwin do not have the most efficient products,


Peter.
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PVPoster1



Joined: 24 Nov 2005
Posts: 385

PostPosted: Fri Jun 24, 2005 11:57 am    Post subject: Reply with quote

When I researched SHW, I decided on evacuated tube equipment over the standard pipes & insulated box set-up (like Solartwin). They cost half as much again but are supposed to be much more effective at lower temps and get more energy out of average to higher temps. Unfortunately the control system isn't nearly sophisticated enough to work out how much energy I've saved, but I'm expecting 800KWh+ per year.

Bandioz - do you really mean wood-chip CHP? I'd love to get one but aren't aware of any domestic units available.
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PVPoster1



Joined: 24 Nov 2005
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PostPosted: Fri Jun 24, 2005 11:58 am    Post subject: Reply with quote

So what SHW did you choose, then?


Peter.
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PVPoster1



Joined: 24 Nov 2005
Posts: 385

PostPosted: Fri Jun 24, 2005 11:59 am    Post subject: Reply with quote

Wood chip CHP. Yes indeed. I saw one in a home-builders magazine (I'll try to remember to dig it out). Try these:

http://www.enginion.com/products/products1.htm
http://www.ecopower.ch/index_en.htm
http://www.sigma-el.com
http://mariahpower.com

www.caddet-re.org
www.dmu.ac.uk
www.b9energy.co.uk
http://www.dmu.ac.uk/ln/DODGIER/renewableenergy.htm
http://www.promanenergy.co.uk/Press/PressSAMeng.htm
http://afbnet.vtt.fi
http://eetd.lbl.gov/ea/EMS/EMS_pubs.html

US Department of Energy www.eren.doe.gov/der/chp/chp-eval.html
International Energy Association? District Heating and Cooling www.iea-dhc.org
Cogen Europe www.cogen.org/projects/educogen.htm
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PVPoster1



Joined: 24 Nov 2005
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PostPosted: Fri Jun 24, 2005 12:00 pm    Post subject: Reply with quote

It's a Schott system installed by Rayotec. Cost ?3,250 installed after Clearskies grant and included a new tank aka. thermal store. It's fully automatic and just needs the pressure meter checking once a year. They come round once to do a survey (1 hour) and installation took about 7 hours.
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PVPoster1



Joined: 24 Nov 2005
Posts: 385

PostPosted: Fri Jun 24, 2005 12:01 pm    Post subject: Solar hot water and wood chip boilers Reply with quote

Hi Damian and Bandidoz,

Have just read your topic. I am a self-employed heating engineer who fits solar as well as the standard stuff. I install for Solartwin and Viessmann (German company) although intend to add more brands.

Solartwin and Viessmann are at the opposite ends of the spectrum, the former being low tech and the latter being high tech. Both however can be used with any system including combi boilers (you just fit an unvented tank to store the water that is heated by the panel and this pre-heated water then passes through the combi boiler as normal)

Solartwin is great for open vented hot water systems with loft tanks and is totally autonomous. High tech systems such as evacuated tubes are better with pressurised (unvented) systems although rely much more on external controls such as thermostats and programmers.

The solartwin option will provide about 50% of your hot water averaged out over the year. Evacuated tubes will offer about 65%. Both will give 100% in the summer months but Solartwin will be ineffective on winter days. Even a 50% return should save about 2500kwh, assuming average daily energy use for producing hot water is about 12 kwh. In todays money that will be about ?50 a year saving if gas is used and about ?125 if electricity is used as the back up power source. As you can see, you will never pay back a solar system since they only last 25 years maximum (excluding maintenance costs).

Obviously though, tomorrows energy prices will mean very much bigger savings and payback within a few years. The saving on CO2 to the planet is also a valid reason.

Evacuated tubes are great because they can be replaced individually if faulty or physically damaged; a Solartwin panel will have to be replaced entirely. But evacuated tubes need anti-freeze which is usually propylene-glycol, a chemical which often needs replacing regularly and is prone to leaking from even the best installed systems so maintenance costs can be high. Evacuated tubes also require a heavy duty pump to overcome friction losses and are not cheap to replace (about ?180 just for the pump). Solartwin pumps are more simple and are guaranteed for 5 years.

Personally, I feel the simpler the better - I prefer Solartwin for that reason. You could of course just make your own for about ?100 which would work very well.

As for wood chip boilers they are available as domestic models in the UK (although I've not seen any domestic CHP versions). Check out the likes of www.3genergi.co.uk/index.htm and www.bioenergy.org/

Viessmann also manufacture wood chip boilers (and every other type of boiler and heat pump imaginable) see www.viessmann.co.uk

Interestingly I went on a course by Viessmann to install heat pumps. The first two hours of the course were about the decline of oil and gas and the world wide threat to the ecomony this will have. Incidently, Viessmann are phasing out CHP. It's been on the continent for years but has proved a loss leader. The development of energy rated fridges and washing machines was funded by British Gas back in the 80's in anticipation of all UK homes having CHP since the electricity portion from a CHP boiler is limited and so efficiency of appliances is key to the success. It still hasn't happened here despite some companys still trying to market it. British Gas lost a lot of money.

Cheers,

Ben Combe
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PVPoster1



Joined: 24 Nov 2005
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PostPosted: Fri Jun 24, 2005 12:02 pm    Post subject: solar again Reply with quote

Sorry, I should have mentioned that a typical hot water solar system (with a Clear Skies grant) is about ?3000. Therefore, the costs I said you would save become more relevant.

Damian, the price you paid for your evacuated tube system was very good - I must check them out

Sadly, Clear Skies may not be around forever. Once the Government pot is gone they will probably withdraw it. This could be in a year or two. You might want to voice your opinion with the DTI at http://www.number10.gov.uk/output/Page1495.asp#2 or with your MP.

Ben Combe
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PVPoster1



Joined: 24 Nov 2005
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PostPosted: Fri Jun 24, 2005 12:03 pm    Post subject: Reply with quote

Ben,

Very interesting information.

Building for a Future magazine (vol 13, no. 3) has some interesting stuff about CHP (http://www.newbuilder.co.uk/bffmag/winter03/13_3%20Cover_story.pdf).

Even with the grants, I think that there's a major capital cost of trying to heat your house non-fossil fuel. As you say, solar thermal heating comes in at 2 - 4,000, but unless you have an exceptionally insulated house, you need heating in the winter (and probably for hot water whatever the insulation), which means a wood (log, chip, pellet)-fired boiler, which seems to cost 7 - 11,000 including installation.

Which means that you're looking at the best part of 10K at the very least, which would take a very long time to claw back,


Peter.
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PVPoster1



Joined: 24 Nov 2005
Posts: 385

PostPosted: Fri Jun 24, 2005 12:04 pm    Post subject: Reply with quote

Ben

Thanks very much for your post - I hadn't realised the potential maintenance costs of evacuated tube systems were so high - fingers crossed! 'm pleased with my system and I've already had (guessing) 20 or 30 days this year when I've had some lift - I'm not quite as obsessed at looking at the controller these days!

I'm quite well versed on wood-fired boilers (being an advocate for them here in Dorset via my local Agenda21 organisation) and was 99% certain there were no domestic CHP versions.

Can you advise me on wood-fired CHP set-ups? I can't seem to get a clear answer from the experts on whether they should be configured for max electricty generation or max heat output in order to get the most energy from the source ie. energy profitability rather than economic profitability.

And another question if I may? Do you have an opinion on retro-fitting underfloor heating if there's no major rebuild planned? I have an 1863 cottage with one 1950s extension and one 1970s extension and have been dissuaded by the two companies I've contacted. I was planning to do most of it myself, room-by-room, connecting up as I go.

Thanks in anticipation,
Damian
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PVPoster1



Joined: 24 Nov 2005
Posts: 385

PostPosted: Fri Jun 24, 2005 12:06 pm    Post subject: Reply with quote

Bandidoz wrote:
Wood chip CHP. Yes indeed. I saw one in a home-builders magazine (I'll try to remember to dig it out).


It was from "Self Build & Design" magazine April 2005. The article is called "Pellet Power". You local Borders/WHSmith/Tesco may still have copies.

www.selfbuildanddesign.com
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PVPoster1



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PostPosted: Fri Jun 24, 2005 12:08 pm    Post subject: Heating Questions Reply with quote

Hi Damian,

Sorry if I concerned you about your solar panel. I'm sure that you will have no problems. I was just trying to give a broad outline of the points to be aware of - for any other readers of this forum. I haven't yet obtained solar for myself. I'm still trying to work out the best long term solution to heating my home. You've certainly done the right thing and should be proud. I'm all for using wood chip heating along with solar and wind, although I haven't told my wife yet.

I don't have much information on CHP boilers, wood or fossil fueled although they are normally configured to give the best thermal requirement first and to use whatever is left for electricity. A ratio of 2 or sometimes 3:1, thermal to electricity is often quoted. If I find out anymore then I'll let you know. Again, any information I do have is for commercial situations. However, Baxi are developing a domestic fuel cell which should produce about 18kw of heat and 1.5kw of electricity although the cell only provides 4kw of this, the rest coming from gas.

see, here and here.

Underfloor heating can be a tricky area. I've installed a fair amount of it. Without seeing your property it is hard to advise. I am near Frome, Somerset and often come to Dorset so can visit your house if you want more advice. Just let me know. It would also be nice to meet a like minded person for a change.

It is possible to retrofit underfloor heating. If you have suspended wood floors then there is usually no problem. If you have solid floors then the issue is with the provision of insulation. I suspect that your property like my house (which dates from 1690's) has no insulation in the ground floor. In which case you must add it and that I'm afraid will raise your floor level, perhaps by 2 or 3 inches (50 - 75mm). It can be done but there are several ways to achieve the same result and so hard to offer full advice here. Once decided, the installation of the pipe work is very easy, just a little time consuming sometimes.

You mentioned that you have a thermal store for you solar panel. I don't know if you have any spare tappings on that but if you do then you can connect the underfloor circuit to those. By tappings I mean the flow and return connections. Sometimes you have 2 or 3 sets of flow and return tappings - one set for the main boiler, one for a solar panel, one set for a heating circuit. Again it is hard to advise here but I'll help if I can.

Regards,

Ben

The illusion of freedom will continue as long as it's profitable to continue the illusion. At the point where the illusion becomes too expensive to maintain they will just take down the scenery pull back the curtains and you will see the brick wall at the back of the theater."
-- Frank Zappa"
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PVPoster1



Joined: 24 Nov 2005
Posts: 385

PostPosted: Fri Jun 24, 2005 12:10 pm    Post subject: Re: Heating Questions Reply with quote

mrkinnies wrote:
I'm all for using wood chip heating along with solar and wind although I haven't told my wife yet.


I'm in a very similar situation. Got any ideas about breaking the news? Rolling Eyes


Peter.
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PVPoster1



Joined: 24 Nov 2005
Posts: 385

PostPosted: Fri Jun 24, 2005 12:10 pm    Post subject: Reply with quote

My 'Mrs' is all for it - she grew up with solid fuel heating and is an expert with the wood stove. She even re-wired the pipe thermostat after my installer had done it wrong!

Getting the solar in the next few weeks. She likes her baths, so free hot water is going to go down well as far as the bills go!

Lucky me! Smile
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billbrooks



Joined: 08 Jun 2009
Posts: 2
Location: suffolk

PostPosted: Mon Jun 08, 2009 3:12 pm    Post subject: solar water heating Reply with quote

We have looked inot the cost of running the solar water heating pump on mains and it is very low. Firstly the pump only runs intermitantly when ther is 6 degree temperature difference between the solar heating collector and the hot water cylinder and because ther ar no retrisctions in tthe circuit (which you usually find in a central heating circuit) the pump has to do a lot less work and can be left on the lowest power setting see
http://www.aztec-solar-water-heating.com/
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