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Who knows about a small Solar PV panel system?

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goldeneyedmonkey

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Ay up folks,

I'm just wondering roughly how much it would cost to buy this following system... I'm planning (sometime in the near or distant future) to have installed a small solar PV panel that will run an electric underfloor heating system situated below 12mm engineered Oak flooring. This is just the 'what if?' stage at the moment, just to see if my theory is realistic and achievable without too much expenditure. The floor area is roughly 20.0 m² and the electric underfloor heating system gives out up to 140w per/m² it requires 230v to run.

How do-able is this with a small PV panel running on a slight to moderately shaded roof that faces south east/ east (not sure exactly, but that's my guesstimation @ the mo). What Kw/H power panel would be needed. I'm in Buxton, Derbyshire.

The underfloor heating system costs £400, then cost of engineered Oak flooring on top of that, then the PV panel. This will be done when I eventually get round to doing the kitchen and knocking a wall through to make an open plan kitchen / dining lounge area. At the moment they are nearly open plan, as I've had 2 doors removed as they made the space very dark.

Let me know your thoughts, and I know this is very rough but it's all I've got swirling around in my head @ the moment. I'm also aware that the F.I.T is being dropped soon, but I don't plan on putting in a massive system and I don't have anywhere near the time and money right now to get it done in a month! :)

Cheers all. _Dan.
 

Dibs-h

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You mean 2.8KW panel\s? I'd say comfortably the other side of £10k. My personal advice would be to fit a Thermal Solar system - if all you want to do is UFH. Thermal Solar is very well suited to UFH. Someone I know spent <£5k and had his whole house fitted (admittedly new build) with UFH, thermal store and some evacuated tubes.

Yes, there is a feed in tariff - but if I was trading capital for income, i.e. an annuity, I'd rather buy one that had legally protected rates.

My 2p worth.

Dibs
 

goldeneyedmonkey

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I wasn't thinking as large-a-panel as that Dibs, I'm very nieve when it comes to knowing about how much energy the PV panel would have to generate to power the 230v needed for the UFH. The only reason I was leaning towards PV as opposed to Thermal Solar Heating panel was I am unsure whether you can put this underneath the flooring, but thinking about it I suppose there's not much difference.

I'm not after a whole system, I just want to do the 1 big open space. - Only reason is I don't want to link it to the boiler as it's a bit outdated (probably 20yrs old by the looks of it), and I don't know anything about the ease of integration between the Solar and current heating system and don't fancy replacing the boiler due to the expense. I'd use the boiler to heat the top floor (3 bedrooms and bathroom), and turn off the radiators in the main living area.

I'm basically after the minimum expense and invasive work to run a UFH system that will cover about 20 m².

Cheers for your tuppence Dibs :) _Dan.
 

Dibs-h

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goldeneyedmonkey":1iffdl3r said:
The floor area is roughly 20.0 m² and the electric underfloor heating system gives out up to 140w per/m² it requires 230v to run.
Dan

20.0 m² running at 140w per/m² gives 2800watts - i.e. 2.8Kw. That wouldn't be one panel - I suspect around 8 panels.

You could just extend the existing downstairs heating circuit and run a wet UFH system in the space.

I certainly wouldn't want to be spending 1000's to electrically heat a space - even if it was just capital costs with no ongoing costs.

Dibs
 

OLD

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Feed in tariff finishes 5-6 weeks i am told the price of the panel's will then reduce considerably so will it be worth it..
 

goldeneyedmonkey

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I don't think it's scrapped altogether, I think it's roughly halved, but it's not really an issue for what I'm after, I just want something to heat 1 x UFH system (if possible).

Ta. _Dan.
 

gregmcateer

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Dan,

Whatever your needs, if you aren't in a hurry, then wait - in fact if you are, then wait!
My brotehr and I have jsut gone into business with an electrician to install PV's - One week before our Lords and Masters in government cut the FiT from 43p/kW to 21p - with 6 weeks notice.
After untold phone calls, we have just (2 hours ago), secured what appear to be the last panels and inverters, (DC - AC transformers) in the country, as everyone is desperate to get installed before the 12 december deadline - our supplier sold £7million worth in 6 days!!

Broadly, a panel will produce MAX (note the emphasis) 200w - 250w depending on panel size, location, angle, shading....

Obviously only produce during daylight, (not nec sunlight, but brighter is better), so if heating eg floor - heat in day and use the concrete floor as a storage heater for night.

I would need to know more for clearer answer, though a ground source heat pump could well be a better option - definitely worth exploring.

Hope that helps - get in touch if you want anything further, (though may be a bit busy between now and 11th Dec!!)

Greg
 

AndyT

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Thinking about the suggestion to use hot water rather than photovoltaics... this does (if you want) open up a whole other world of options - including diy solar panels made from old radiators and glass - a quick google led to this example using bits of a fridge: http://www.thesietch.org/projects/solarthermalpanel2/index.htm
and what looks like a useful forum http://www.thegreenlivingforum.net/forum (but you probably already knew that).

It could give you the option of making something totally self-contained where all your costs would be known and under your control. But I don't have any knowledge of the practicalities and questions such as how much roof area you would need to have to get enough energy to warm your room in winter when you need to. I suspect that last bit might be a touch challenging!
 

gregmcateer

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Dan,
sorry, forgot to say - I'm putting in a 1.2 kW system on my roof, which including inverter, meter, 6 panels, wiring, wiring, installation, etc, is about £8,000 all in - hope that gives you some idea.
Greg
 

goldeneyedmonkey

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Cheers Greg and Andy, a ground source heat pump may be a bit limited as I have a small back garden, only 20m² ish. Though I am aware that you can can go vertically as well as horizontally. I like the idea of D.I.Y solar panels. I basically want the most economically and environmentally friendly solution to adding some underfloor heating in a large room. I haven't done loads of research to be honest, just bounced ideas off a few people. It's probably not the best time to be thinking about it really as it'll be a while till the project starts. I don't mind a decent capital outlay as long as it saves money in the future and or adds value to the house.

Greg- That sounds like something I may consider in my next property, or maybe even this one if business picks up a bit, got some projects that may take off. But how much will that setup have to be supplemented by other forms of power? And how big is your house?

Also, I had realised that there would be a mad rush right now for people getting solar systems fitted! I hope you get a nice rush in before the Christmas break mate.

Cheers all. _Dan.
 

RogerS

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Dibs-h":3572ukmv said:
With electric UFH,it's the thin mat stuff, that reminds me of exercise\yoga mats.
Actually you reminded me that I put some underneath some ceramic tiles in a bathroom. Seem to recall it was damn expensive.
 

dickm

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I think the problem with this whole idea is the trade-off between getting heat OUT of the floor into the room, and getting heat stored IN the floor for nightime, which is when you need the warmth. Difficult to get the right compromise that doesn't leave you with an overheated house in the day or a cold one at night. Another disadvantage of the PV idea is that their inherent efficiency of conversion from solar to electricity is not that high (perhaps 15-20% at best). That's OK if you want to generate a premium form of energy, but a waste if what you want is heat. Solar thermal should give you quite a lot better efficiency, and will cost a lot less.

One possibility that my son-in-law is considering is installing some form of heat store (either a dirty great insulated tank, or one of the more sophisticated latent heat stores) and either feeding heat into that from solar panels (PV or thermal) or from a log boiler that needs to be run flat out for short periods. Then the heat can be tapped of when required.

One last consideration - Mike Garnham, who used to post on this forum and designs/installs heating systems warned me that installing underfloor heating is really only effective in a new solid floor. With a suspended floor, or an old solid floor you end up heating the space or the earth underneath.

If you want PV, use it to generate electricity and sell it to the grid. Even at the new FIT, it may still make more economic sense.
 

goldeneyedmonkey

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I think I may need to do a bucketload more research! :D

It will be sat on a solid floor above my garage (whole ground floor is garage), but it's not concrete so I will need to insulate a fair lot before installing everything.

I'll look into it all in depth and get back on here and report what I've found.

Cheers for all advice given, it's much appreciated.

Ta. _Dan.
 

misterfish

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Your 'slight to moderately shaded roof' can make a major difference to output and you need to have this properly assessed which a decent reputable supplier should do as part of the survey. It is difficult to find information of the effects of shading and cloud - in summer we have produced over 20Kw/hr in a day yet a couple of days later when wet and cloudy only 4Kw/hr. This month so far we have a maximum daily production of just over 7Kw/hr dow to only 0.33Kw/hr on a really miserable day.

Second concern is will your floor have a large thermal mass to 'store' the heat as (obviously) any solar system will only work well with decent sunlight levels - precisely when the heat requirement is at its lowest.

As for panel requirements - we have 3.2Kw of panels that actually produce about 2.9Kw output at maximum during the height of summer. This actually ends up at 2.6Kw of actual mains equivalent power (as measured on the production meter).

Misterfish
 

Losos

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dickm":2u7ctq7l said:
Another disadvantage of the PV idea is that their inherent efficiency of conversion from solar to electricity is not that high (perhaps 15-20% at best).
15 to 20% at best and if I may add ONLY when the PV panel is exactly at 90 degrees to the the sun.

I did some experiments with a small PV panel and could not believe how quickly the efficiency drops off as soon as the sun moves.

I completely agree that for heating PV panels (of any size) are NOT the way to go, think about it, if people like Siemens can't make it viable what hope have any of us.

As dickm mentioned PV panels can produce useful electricity which can be used to charge batteries etc. but heating :?: I don't think so.
 

goldeneyedmonkey

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I had only thought about maybe going down the route of PV as opposed to thermal solar water heating because companies where wary of putting them underneath wooden floors and suggested electrically heated UHF, but I think if there's enough room for the timber to expand then a normal UHF system would be fine. Engineered flooring would definitely be safe I reckon.

It's crazy how much this stuff costs to do.

Anyway, I'm going back to the drawing board.

Cheers _Dan.
 

9fingers

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Dan,

Some major drawbacks you need to look into.
1) The power from PV is only available during the day - a good thermal mass in your UFH could cope with this with luck
2) The output drops off radically during the autumn and winter months just when you will need the heat. No realistic slab is going to be able to store heat from the summer months and release in the winter let alone one you can suspend over your garage!!
3) The PV systems that attract the FIT must be grid connected otherwise they shut down ( however bright the sunshine is)
this means that most of the time your UFH will be running on grid power which you will be paying for. Unless you have an intelligent control system which only enables the UFH when the PV system is generating

This is the power generated by my south facing 10 panel 2.35kWp PV system for November

You can see it varies wildly from day to day

DD/MM/YYYY;kWh
01/11/2011;2.106
02/11/2011;2.091
03/11/2011;1.848
04/11/2011;1.729
05/11/2011;1.319
06/11/2011;3.447
07/11/2011;0.516
08/11/2011;0.736
09/11/2011;2.405
10/11/2011;2.097
11/11/2011;1.023
12/11/2011;2.735
13/11/2011;2.509
14/11/2011;0.505
15/11/2011;2.957
16/11/2011;0.902
17/11/2011;1.954

if you want more data from earlier months you can connect to my system
ftp://solargeneration.myftp.org/SBEAM/
Ignore any password requests just hit return and you can see monthly and daily generation files.

Bob
 
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