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HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: neilydun on May 17, 2010, 08:01:47 AM



Title: Air or ground source + solar
Post by: neilydun on May 17, 2010, 08:01:47 AM
Hi, I am after some advice if possible.
I live in a converted barn (converted about 15 years ago), which is well over a hundred years old. We have wooden framed double glazing with heat reflective glass through the building, and the building is insulated, altough this could be improved.
The overall living space is about 280 Sq. M, with approx 90 Sq. M of underfloor heating on the ground floor. The underfloor, and our wood burning stove manage to heat our house, even through this years harsh winter. A lot of the heat produced travels up through the lounge to the 1st floor and loft room, as the landing is galleried.
There are rads throughout the 1st and loft rooms, but as I said, we did not need these on this, or any other years since we lived here (8 years).
I have a 3.6 Kw P.V system on the roof, and currently I am using an oil fired boiler.
I would like to take advantage of the grant available for either a ground, or air source heat pump, and maybe a solar collector.
My question is which one is the better system?
The research I have done on the net seems conflicting. Obviously the air source would be far easier and less disruptive to fit, but I hear horror stories of how electric consumption soars, and when the temp drops below freezing they are not much use.
So would ground source be the better bet, I have about 380 Sq. M of usable space to use, I don`t even know if this will be enough area to make use of a ground source.
What is the likely cost of either system?
I would also like to mention that hot water is an issue. My wife and I have 3 son`s so we use a fair ammount of hot water. Can a air source heat pump produce plenty of hot water, even in cold temps, and what temp is achievable in the cold weather.



My thanks in advance for any information you could share.


Title: Re: Air or ground source + solar
Post by: martin on May 17, 2010, 08:19:06 AM
The simple answer is that what you've heard is pretty accurate - air source can be expensive to run (at today's prices- if they escalate as they must, they will become even more so) and is at it's worst in the depths of winter when you most need it, of the two, ground source would be far better, but more expensive for the initial installation.
Using the "what would I do" way of looking at it, I wouldn't bother with heat pumps at all (electricity, unless home-generated = escalating and hefty costs to run), but would look instead at the incorporation of solar hot water, and possibly replacing the oil-fired boiler with some form of wood-fired device. :)


Title: Re: Air or ground source + solar
Post by: MR GUS on May 17, 2010, 09:37:30 AM
Sounds like you've got room for a MASONRY stove, I'm sure someone will be along to "bang on" about them (see his sig)  ;D ...

What size stove fo you have, location etc, maybe a pic? ..Billy & daftlad may be assistance there, but ther are plenty of threads to them if you utilise the search facility.


Title: Re: Air or ground source + solar
Post by: neilydun on May 17, 2010, 09:57:11 AM
Hi, and thanks.

I am not sure what rating my current stove has, but the opening at the hearth is about 1.8m wide x 1.3 heigh. Its located at the end of my lounge, just asjacent to the area which has an open ceiling, so a lot of the heat generated rises.
The only problem with using it with a back boiler or anything similar, would be that its completely surrounded by underfloor heating.
There would be no way to run any pipework from anything new to be located here, and the existing stove generates plenty enough heat, so much so, that when its hot you can`t get near it.
As for the haet pump, I do generate a little electric from home, as I have 3.6kw pv on the roof. I know thats not huge, but maybe a little offset?


Title: Re: Air or ground source + solar
Post by: knighty on May 17, 2010, 09:58:34 AM
do you have enough south facing roof space for lots of solar thermal ?


with under floor heating, I'd think this would be the perfect option ? (especially with a decent sized hot water tank)


maybe leave the oil fired boiler as it is, for if it gets really really cold...


Title: Re: Air or ground source + solar
Post by: MR GUS on May 17, 2010, 10:06:51 AM
neilydun, go & look for the backplate of your burner if not all browned out through heat, take a pic, if it was there when you bought the barn maybe it was simply thrown in there? as a cheap space filler, therefore innefficient (though i hope not) ..this will obviously affect the labouring & fuel expenditure, so bearing in mind the space to fill, i'd start by getting the make & model to work upon what's already in place maybe?


Title: Re: Air or ground source + solar
Post by: neilydun on May 17, 2010, 10:29:50 AM
Yes I do still have some roof space left, but the PV has taken up a fair chunk of space, I have maybe 25 Sq. M of roof space left.
The stove was fitted by us when we moved in. I am more than happy with the ammount of heat we get from it.

I can take some pictures, how do I attach them?










Title: Re: Air or ground source + solar
Post by: martin on May 17, 2010, 10:33:05 AM
as long as they're under 128k a piece, just click on "additional options" at the bottom of the reply box, and follow your nose, or use the "img" tags and cut and paste the internet url of the pics if you have them stashed with Flickr or the like............. :)


Title: Re: Air or ground source + solar
Post by: neilydun on May 17, 2010, 10:46:16 AM
Hmmm O.k Ive not done this before, but I will try


http://www.flickr.com/photos/50303149@N06/

That should be the link. Maybe?


Title: Re: Air or ground source + solar
Post by: Billy on May 17, 2010, 10:51:18 AM
Worked for me.   ;D ;D ;D


Title: Re: Air or ground source + solar
Post by: MR GUS on May 17, 2010, 10:53:14 AM
Jeez that looks a beast of a burner!

Encore woodburner by Vermont castings...

Product Specifications
Ash Pan YES 
Log Length (Max.) 20 in.
EPA Emissions Rating 1.6 (grams/hr)
BTU/hr Range EPA Test Method 8,700 to 41,700 BTU/hr
Cast Iron Construction YES 
Heat Circulating Fan NO 
Flue Collar Size Oval 8 in.
BTU/h (Max.) 47000 BTU
Efficiency 76 %
Burn Time (Max.) 9 hours
Combustion Technology Catalytic 
Firebox Lining Cast iron 
Firebox Volume 2.1 cubic feet
Heating Area (Max) 1900 sq. ft.
Rear clearances (with optional shields) 19 in. to combustibles 
Weight 435 lbs.
Unit Depth 21 3/8 in.
Unit Height 25 7/8 in.
Unit Width 27 in.


Title: Re: Air or ground source + solar
Post by: neilydun on May 17, 2010, 10:56:56 AM
Yep, it was the biggest we could get at the time. Anything smaller would have been a bit lost in the space I think.
It really kicks the heat out!!


Title: Re: Air or ground source + solar
Post by: neilydun on May 17, 2010, 10:58:35 AM
And thanks for the spec`s


Title: Re: Air or ground source + solar
Post by: MR GUS on May 17, 2010, 11:29:10 AM
Makes sense to list em, others can use the overall effect of your combined components to guage things.


Title: Re: Air or ground source + solar
Post by: dhaslam on May 17, 2010, 12:59:26 PM
If you are using solar heating then you need to be able to store heat  for a long period.    There are some sunny days in winter that would heat the house  but the ratio is only about one day in six and they tend to come a few days at a time.    I am starting to construct a seasonal store.    For  cost reasons this is going to be  clay based because  the insulation used (straw) is  cheap   and it can be heated by warm air which is easier to heat than water.   The heat will be transferred to the house by two water pipes.  One will be used to preheat the air intake to the air to water heat pump and the other direct to the buffer tank that feeds the underfloor heating.  The collector area will be about 24 square metres and the  volume of clay inside the insulation about 200,000 litres but the heat requirement is quite low.   Heat was supplied this winter by the nominal 5kW  heat pump  but it had to run almost round the clock in the cold weather because performance is poor at low intake temperatures.  With the preheat system it should be back to  using the off peak hours only, costing about one euro per day in winter.           


Title: Re: Air or ground source + solar
Post by: tony. on May 17, 2010, 01:22:02 PM
couldnt the PV /offset the GSHP/ASHP energy consumption. i assume that you have a large thermal mass,being a old barn, with stone walls and possibly concrete floors.

tony


Title: Re: Air or ground source + solar
Post by: neilydun on May 17, 2010, 02:21:27 PM
Yes the PV would offset the energy consumption of either, but I have read of huge electric bills from air source pumps, and during the coldest periods, not a lot of heat being generated by them.
If this is the case they are not really for me, but I only know what I have read on the net, and wanted to get as many people`s opinions before I make a descion.
I do like the idea of being able to extract heat from the ground, for little cost, but would an air source and solar themal combined do the job just as well, without having to dig up my garden?


Title: Re: Air or ground source + solar
Post by: martin on May 17, 2010, 03:09:38 PM
The Law of Sod prevails-  when you most need heat (midwinter) you'll be getting diddly squat out of the solar, an ASHP will be clanking away full tilt at it's most inefficient (COP of "1" is not unusual at that point) , so you're using electricity to effectively  "directly" heat your home, might as well have a few electric fires.... Ground source will work better in winter, but installation is pricey, upheaval to install considerable......... :-\
If you're already "exporting", everything depends on the deal you have with your power company, but I'd suggest with the size of array that you have, you're probably pretty much "evens" in import/export, so I'd tend to avoid heat pumps altogether..........
The other thing to bear in mind is that if you're miles from nowhere, if the mains connection fails and you're dependant on heat pumps, you'll be pretty parky, whereas with wood........... ;)

Having "done the sums" several times for this sort of thing I will utter complete heresy - if you  have an existing oil boiler in good nick, you may be better off to keep it and supplant where needed with wood/solar..........(keep the oil boiler for "emergencies") - solar for DHW Spring to Autumn, wood to take over in the colder months........


Title: Re: Air or ground source + solar
Post by: neilydun on May 17, 2010, 04:02:19 PM
Thanks for your thoughts Martin.


Title: Re: Air or ground source + solar
Post by: daftlad on May 17, 2010, 04:11:08 PM
How much is wood costing you (in time as well as money). If it is free then maybe sticking with that or expanding it slightly would maybe be the best option.
The main advantage of Masonry stoves is that they are very efficient 90+ percent and a lot of there heat is given out as radiated heat which would be better for you because it would not travel straight upstairs (which is what hot air does).
Often barn conversions don't have so much thermal mass because they are insulated on the inside of the walls.
ta ta


Title: Re: Air or ground source + solar
Post by: neilydun on May 17, 2010, 04:38:02 PM
Hi daftlad, Ive no insulation on the inside of my walls, they are solid and thick, up to 2 feet thick in some places. When we bought the place the walls were full of damp, so I hacked off the plaster, D.P.M injected and then rendered.
I gather up my own wood, so in a way its free, except I have to travel for it, petrol and chains for my saws, and then there is my time??? Maybe it cost more than I thought !


Title: Re: Air or ground source + solar
Post by: billi on May 17, 2010, 08:37:41 PM
Hi neilydun

An old Barn needs a woodburner  ;D ,  and there are good , very efficient ones on the market


I helped about 4 years ago to install this one in an old  cottage in Ireland  , in combination with a 1000 litre thermal store and 10 m2 solar thermal panels

http://www.youtube.com/watch?v=2LWtwPe6T88&feature=related

I still think that is the ideal combination for people who have access to firewood , to go for wood burning and solar thermal as a combination , and as Martins says use the "Dirty" sources as a emergency (like oil ,gas, heatpump  :-X )

Sure if you have the space and the calculations are right (compared to a ground source heatpump costs  ) then i would go for an outside log burner that take meter lengths  of (un)splitted wood  and a 5000 litre store  (just a geustimate ) and cover the remaining 25 m2 with (some or all) solar thermal panels on your roof ... to reduce work /firing-up


Billi



Title: Re: Air or ground source + solar
Post by: brackwell on May 18, 2010, 09:53:54 AM
Hi Neilydun,

You ask the $1000 question as the saying goes and to be honest i do not think the definitive answer to this exists.  In many cases people quote examples/facts without any hard data to back this up and it may be out of date figures or figures chosen to suit their argument.    People talk about it being useless/expensive in winter but where is the facts to counteract the professional/manufactures saying it is OK. down to -15C.   To be honest only listen to those who have one.

My feeling is that using a solar thermal ( i have one ) for the hot water is the clear sure bet . It has to be a good investment whichever way you look at it and soon you will be able to get say 400 against your elec bill and my hobbyhorse is that you tie this in with a electric inline heater as a insurance policy against poor sun.

Ken


Title: Re: Air or ground source + solar
Post by: martin on May 18, 2010, 10:06:33 AM
or the "prejudice" may come from those of us who've seen innumerable people to whom heat pumps have been grossly oversold, and talking to those who have had them installed and really wish they hadn't! ;)
I'll reiterate - I've "done the sums" many times (using real life performance, not hyped claims), and I have never been able to make them "add up" unless you have something like a hydro plant churning out gobbets of power (which few of us are fortunate enough to have) ::)


Title: Re: Air or ground source + solar
Post by: neilydun on May 18, 2010, 10:45:05 AM
Yes, everyone seems to agree that solar themal is the way forward. If this is the case do I fill my roof space (approx 25 Sq M) with them? and keep my existing oil fired system?
Altough I like the idea of a woodfired burner I don`t really want to spend any extra time collecting wood, and the supply which I have at the moment is limited, as is a space to fit a woodburner.
If, for example, I were to fit 25 Sq M of solar thermal and it was mid winter, 0c outside temp, but a bright sunny day, what temp could I hope to achieve ?
I have approx 85 Sq M of underfloor to heat and hot water.
Does anyone have any toughts on the RHI ? and the rates they have set out ?


Title: Re: Air or ground source + solar
Post by: dhaslam on May 18, 2010, 11:26:26 AM
This winter was very good for solar thermal because it was frosty with  clear skies.    November was the worst month but then it was warmer.

This graph in kWh  is for just under six square metres.  From a system four times larger there would be enough heat most days to warm the floors.  Output is greater if the system is set up to transfer heat at lower temperatures.      To get the full benefit you ideally would need to add some seasonal storage.   In any case you would need to dump a lot of heat in summer, more that 75% of the heat produced most days.   


Title: Re: Air or ground source + solar
Post by: djh on May 18, 2010, 11:52:14 AM
do you have that data as a CSV file? Just for fun.


Title: Re: Air or ground source + solar
Post by: Countrypaul on May 18, 2010, 03:47:07 PM
or the "prejudice" may come from those of us who've seen innumerable people to whom heat pumps have been grossly oversold, and talking to those who have had them installed and really wish they hadn't! ;)
I'll reiterate - I've "done the sums" many times (using real life performance, not hyped claims), and I have never been able to make them "add up" unless you have something like a hydro plant churning out gobbets of power (which few of us are fortunate enough to have) ::)

Martin,

Is there an element of those that have had problems shouting loudest in this case, and those that are happy, keeping quiet and busy with other things so not looking round discussing things etc?

I am sure that they will have been grossly oversold, especially by salesmen on commission one way or anothertoo much "won't be my problem when it doesn't perform cos I'll be gone by then.."

Paul


Title: Re: Air or ground source + solar
Post by: billi on May 18, 2010, 06:32:41 PM
Quote
Yes, everyone seems to agree that solar themal is the way forward. If this is the case do I fill my roof space (approx 25 Sq M) with them? and keep my existing oil fired system?

I wouldnot rush , if you are the character that likes thinking of ideas ....
There are lots of ideas/thoughts  to be combined to a clever heating idea
But you could end up like me , to have too many ideas without a plan  :norfolk


Anyhow a customer of mine here (ireland)  asked me 10 years ago to built a lined Pond , so i did built his pond ( me am a Pond builder since i am 2 years of age  ;) )

He asked me to bury  ca. 800 metres of 1 " Pipe underneath the Pond/liner  for his heatpump idea

He has about 20 m2 solar thermal on the roof and the controller/ plumbing  control the flow ...

So if solar is doing enough for hot water and heating (in a 750 litre store ) , the controller sends the extra heat from the solar panels back under the pond, or in his case under the foundation into an earth store as well  , the heatpump just connects to the warmest source first , so measures  the temp under the pond , if that is colder , it switches to the stored heat under the foundation  and back to the pond 

Sounds complicated , but  all i want to say is that a heatpump can benefit from the overproduction of bigger solar thermal Idea if that heat from summer/or sunny days  is captured some how !

Billi 

thats the pond


Title: Re: Air or ground source + solar
Post by: dhaslam on May 18, 2010, 07:11:40 PM
do you have that data as a CSV file? Just for fun.

Xls file attached.   CSV  format doesn't seem to be allowed by the system

There doesn't  seem to be much data available on long term underground storage.  I will bury some temperature sensors into  mound and monitor the temperature  over the year.  It will be another few weeks before it is setup but I want to have it start heating before the end of June.  This winter has given more confidence that the  temperature can be topped up even in winter months.     

The greenhouse overnight store is   not working that well in warmish weather.     The exit air is getting up to  about 16C by the end of the day and dropping to around 10C  by morning.  So the store is varying by about  six degrees  but perhaps adding only about one degree to the greenhouse temperature.    The heat transferred is something like 2.7kWh, assuming that the two fans are moving 300cu metres of air per hour and average differential of 3 degrees.   But the greenhouse has practically no heat retention,   U-value is about 4 and surface area 32 sq metres so  over  nine hours the heat loss should be about 1.2kwh per degree differential but there is also  some ventilation loss as well.      I think it should work better in very cold weather when the temperature difference is greater.  Fitting auto vents has reduced the input temperature to the mid 20s C most of the time.   There is no temperature control on the fans yet, just time. 


             OutMin In_Min    Min Exit   MaxExit
09/05/2010      3       5                    Before fans used
10/05/2010   4   6.5      8      
11/05/2010   1   5      9      16
12/05/2010   2   6      10.6      15
13/05/2010   5   8            
14/05/2010   5   6      10.2      
15/05/2010   6   9            
16/05/2010   5.5   6         12      
17/05/2010   6   7        12      
18/05/2010   8   10.5        10.8      





Title: Re: Air or ground source + solar
Post by: neilydun on May 18, 2010, 07:50:00 PM
Thanks billie, not forgeting I don`t really know what i`m talking about, and thats why I originally posted on here---

If I was to have about 25 Sq. M of solar thermal on my roof, in the winter that (might) be enough to heat my underfloor, and water.
In the summer that would be oversize, and someone posted earlier I would probably have to dump up to 75% of heat produced.
So, if I dug out for a GSHP, during the summer months could the process be reversed, and the excess heat produced from the solar, be dumped back into the earth?
Either via running the GSHP in reverse ??? or running another pipe alongside the collecter???

Like I say I don`t know if i`m talking out of my a*** its just I hate to think of 75% of what is produced during the summer months going to waste, and I dont have enough room to build a lake in my garden, it looks lovely by the way !


Title: Re: Air or ground source + solar
Post by: martin on May 18, 2010, 08:24:20 PM
There are all sorts of arcane schemes to use solar to heat homes in winter, to be frank, it's all usually a colossal expenditure for very little return (it's that "law of sod" again) - when you  most need the heat, it ain't there......... Most people end up with a pragmatic April - October heating of domestic hot water by solar... ;)


Title: Re: Air or ground source + solar
Post by: dhaslam on May 18, 2010, 09:01:49 PM
Thanks billie, not forgeting I don`t really know what i`m talking about, and thats why I originally posted on here---
So, if I dug out for a GSHP, during the summer months could the process be reversed, and the excess heat produced from the solar, be dumped back into the earth?
Either via running the GSHP in reverse ??? or running another pipe alongside the collecter???

I think that the problem with the  GSHP coils is that they are normally spread over a large area this allows the pipes to pick up some natural heat from the ground in winter.   The problem is that being spread out they would also lose heat as well.    It would be better to have a more compact storage area separate from the  normal collector.    I am using above ground store because the ground is very rocky but it would be possible to store the heat underground if there is insulation, at least on top.   


Title: Re: Air or ground source + solar
Post by: daftlad on May 18, 2010, 09:15:16 PM
There are all sorts of arcane schemes to use solar to heat homes in winter, to be frank, it's all usually a colossal expenditure for very little return (it's that "law of sod" again) - when you  most need the heat, it ain't there......... Most people end up with a pragmatic April - October heating of domestic hot water by solar... ;)

Except if your house is designed to work as a passive solar heater, they work very well, even in the UK.
It is possible to heat your home with virtually no fuel, even in the UK.
ta ta


Title: Re: Air or ground source + solar
Post by: MR GUS on May 18, 2010, 09:15:39 PM
Went to avail myself of mispriced goods @Tesco's (spit) yesterday basically buy 1 get 14 free  whistle
The tarmac in the carpark was sizzling, shame theres no  GSHP layed down in Englands car-parks, they DO HAVE ROOM after all to at least make a contribution.


Title: Re: Air or ground source + solar
Post by: billi on May 18, 2010, 09:16:02 PM
Billi

neilydun  ... nearlydone  

It is the same pipe work , the surplus of the overspec solar  is pumped into (example) ground store and then the heatpump  benefits in higher COP of the preheated ground , or the heatpump does not need to work at al cause solar is providing heat


Billi

PS :
Quote
There are all sorts of arcane schemes to use solar to heat homes in winter
 that work fine  ;)


Title: Re: Air or ground source + solar
Post by: neilydun on May 18, 2010, 09:30:36 PM
Can`t knock Tesco (spit spit) at the mo. My HiLux runs on veg oil and Tesco has been punting it out at 42p a litre.
Happy days !


Title: Re: Air or ground source + solar
Post by: MR GUS on May 18, 2010, 09:37:13 PM
That's it though use em & abuse em, we simply take advantage of specific deals then Heinz off to waitrose for a proper shop with quality food.

 However the deal on cartons of chopped  (multi flavour) tomatoes are working out ideal for  batch cooking spags for the nipper & vacuum sealing.
System glitch, that gives you a moneyback reduction too, thought it had been fixed.
 If I see a cheap veg oil deal I'll remember to put it here!


Title: Re: Air or ground source + solar
Post by: billi on May 18, 2010, 09:40:20 PM
Quote
My HiLux runs on veg oil and Tesco has been punting it out at 42p a litre.
Happy days !


 ;D have to check prices here again cause my Pick-up is converted as well


Title: Re: Air or ground source + solar
Post by: neilydun on May 18, 2010, 09:44:17 PM
Offer finished yesterday I think. I will post any others I hear of.
Was on a BOGOF


Title: Re: Air or ground source + solar
Post by: martin on May 18, 2010, 10:21:14 PM
I'll reiterate what I said - despite the best efforts (via Tesco) to go completely off track, yes it is possible to concoct schemes involving hundreds of solar tubes, thousands of litres of insulated storage, heat pumps, and doubtless several donkeys in treadmills too......... yes, it's possible to heat a home using solar in the UK -it's also possible to build a passivhaus, and use virtually no input of energy all winter.......... BUT, down here in the real world, we have someone with a barn conversion, with not an enormous plot of land, who's looking for possible, practical ways to heat his home............. ::)
I always take questions like this seriously, and apply "what would I do in his shoes" to it.... I doubt there are bottomless pits of money to be wasted, and we're "starting from where we are"....... to that end, my recommendations to minimise outlay, both on putting in the system and running it would be along the lines of solar DHW for the summer months, wood/oil for the winter, having taken all reasonable measures to insulate as well................. simple, relatively inexpensive, reasonably "future proof" - boring but pragmatic! ralph:


Title: Re: Air or ground source + solar
Post by: billi on May 18, 2010, 11:21:06 PM
 
Quote
boring but pragmatic!
Pragmatic in my point of view is  10 kwP of PV installed  for 25000 $ and a heatpump then  ;D

Billi


And get the grants or the FIT  :P  , and why should i need any solar tubes then  ::) , just joking  :laugh:

But  even without any cash help and of grid i think of that

Billi


Title: Re: Air or ground source + solar
Post by: Bodidly on May 19, 2010, 08:58:22 AM
A word of warning on underground thermal storage with heat pump.
I have a 6kW ground source heat pump. I regularly monitor the temperature of  the incoming ground loop. During the winter this temperature will tend to slowly drop away due to cooling of  the ground near the loop but after periods of heavy rain the ground  temperature will return to near 10degrees in a mater of hours. This is great in winter but if you had raised your underground storage to 15degrees and this went down to 10degrees in a mater of hours not so good.

So I would recommend that any underground heat store is protected from the ingress of ground water.


Title: Re: Air or ground source + solar
Post by: rt29781 on May 19, 2010, 12:44:49 PM
We have 150 tubes on a sw facing roof in SW France and get heat into the house most of the time.  We top up with heat from an air to water heat pump and this next year we will have our woodburner working.  On the really cold cloudy days there is obviously no solar and there is very little heat coming from the heat pump (anything below freezing and the heatpump struggles).  So on real cold cloudy days use the woodburner or take a hit on the electricity cost.  On cold clear days (even in a howling gale) the solar thermal heats the house no issues.  It depends where you live and how much cloud you have as to whether solar thermal will be worth it for you.  If I were to start again, and was bothered about the cost, I would just make the whole roof a solar collector.  Simple black plastic tubes with a polycarbonate cover and take the output straight into the floor using a variable speed pump controller to get the temperature constant (40C) for the floor.  I cannot fault the Navitron solar tubes but they are expensive and we have a massive roof area so we have choices.  However the solar heating system is very easy to manage.  In summer there is excess heat and that continues to be an issue.  We were also in a dilemma about choosing an air or water source heat pump.  We inherited 2 air to air heat pumps and they work well but don't heat the floor area so you end up with a warm head and cold feet.  We went for an inexpensive Trianco air to water heat pump which although rated at 12kW only puts out 6 to 9 kW when it is required.  It does munch electric (2.6kW/hr) but it was a breeze to fit and complements the solar heating.  We also like the house warm (23C) as we live in SW france we are used to being warm now. Use the house floor as the storage system as much as you can.  We have a storage tank which is a 500lt plastic bucket in 1 tonne of concrete and this captures excess heat from the system in the day and puts it back into the house in the evening.  We did try seasonal storage by pumping excess summer heat into the ground under our pool but killed one of our trees so stopped doing that.  We spend very little ongoing on heating now but have to recoup about 6000 for the heat pump and solar tubes.  I doubt we will use the woodburner for more than a month in winter.  We will probably use the heat pump for another month and the rest of the time we will use solar.  It is a long term investment even in the south of France.  However today it is cool and windy outside but very cosy inside for 170m2 house.  It is quite cloudy but there is enough sun to heat the house.  I hope this helps.


Title: Re: Air or ground source + solar
Post by: neilydun on May 19, 2010, 04:21:27 PM
I just wanted to say thanks to everyone who`s posted a response.
I`m not sure i`m that much clearer, but its good to hear different people`s opinions, experiances, and I will try and take as much as possible on board.
Thanks again !