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    I am just about to install a ground source heat pump in an industrial unit we are moving into. My aim is to install a system I can use to heat the offices and use as a demo site to obtain MCS accreditation. There seems to be a lack of decent information about and a distinct lack of response from suppliers. The best bit of useful info came from a guy called topher on this forum who posted a lot about an install in France (which is why I joined). So my idea is to install 2 or 3 boreholes just outside the office, under floor heating upstairs and a combination of other heat emitters downstairs. I would also like to install a solar thermal panel to somehow add warmth to the water coming out of the ground loop so I dont have to have such a big jump in temperature. I believe you can get some heat from decent panels even in the winter - anyway I've been told it wont work but not had a decent reason why. Any comments or advice would be good
    • CommentAuthortony
    • CommentTimeAug 24th 2013
    Solar thermal does produce warm water even in winter but nothing like enough to make any reasonable contribution to heating in winter. In all events you should consider adding insulation and for sure deal with all draughts and air leaks.

    One deeper borehole should be used if you have more than one they need to be quite far apart.

    It is important to size the borehole correctly and generally gshp systems are sized to meat the heating loads on all but the coldest days when additional heat added from a different source.
    Thanks I was just thinking of adding the solar heat to the ground loop - if it comes into the heat pump a little bit warmer the heatpump would surely have less to do
    • CommentAuthortony
    • CommentTimeAug 24th 2013
    Yes but not enough to make it worthwhile, better to spend on insulation.
    • CommentAuthorBeau
    • CommentTimeAug 24th 2013
    <blockquote><cite>Posted By: mikeambrose</cite>Thanks I was just thinking of adding the solar heat to the ground loop - if it comes into the heat pump a little bit warmer the heatpump would surely have less to do</blockquote>

    I met a chap who worked for one of the GSHP suppliers and he had added solar collector to his ground loop. His thinking was that during the summer months the heat from the panels was circulated into the ground loop to build up his energy store. He was convinced it was effective with ground loop temperatures at 20 c late summer. Might be worth looking at this blog as well. http://chargingtheearth.blogspot.co.uk/
    • CommentAuthortony
    • CommentTimeAug 24th 2013
    How would you stop it cooling the loop at night say?
    • CommentAuthorBeau
    • CommentTimeAug 24th 2013 edited
    Posted By: tonyHow would you stop it cooling the loop at night say?

    Can't quite remember but the circulation pump was switched on and off either by a timer or maybe a solar powered pump. This pump was an addition and not part of the GSHP itself.
    • CommentAuthorEd Davies
    • CommentTimeAug 24th 2013
    Wouldn't you just not put the fluid through the solar collector when the collector is cooler than the fluid coming out of the ground? One or two motorized valves and simple differential temperature controller would do it.
    • CommentAuthorBeau
    • CommentTimeAug 24th 2013 edited
    <blockquote><cite>Posted By: Ed Davies</cite>Wouldn't you just not put the fluid through the solar collector when the collector is cooler than the fluid coming out of the ground? One or two motorized valves and simple differential temperature controller would do it.</blockquote>

    That might be it Ed. To be honest it was some years back and can't remember all the detail.

    Some more opinion here http://www.yougen.co.uk/blog-entry/1743/Can+solar+panels+improve+the+efficiency+of+your+ground+source+heat+pump'3F/
    • CommentTimeAug 24th 2013
    I think you would be better of going a few feet deeper or having a few feet extra on a horizontal slinky.

    Should be easy enough to work out what contribution could be expected.

    If this is to sell systems then maybe use PV to heat a store (as Ed suggests on another thread) and show how this can perform better in the winter than ST.

    Like all these systems they have to be matched to the demand. It is no good just going 'big' in the hope that you scavenge enough energy as you lose overall efficiency.
    Mikeambrose said:

    ''So my idea is to install 2 or 3 boreholes just outside the office, under floor heating upstairs and a combination of other heat emitters downstairs.'

    Why not UFH downstairs?

    If the flow temp of the ''of the other heat emitters'' is > that of the UFH you drop your CoP.
    Hi Nick
    I have been trying find good info on GSHP etc. I am convinced it is a good idea and there is a decent market for this stuff together with the RHi for commercial properties. The trouble is the people selling the stuff dont seem to now much about it and the people installing it have all got their own views not all based on fact. So what i want to do is install a system that can demonstrate the benefits of different approaches. I think its the only way I'm going to find out I wouldn't want to experiment on a customer. Our unit is similar to thousands, reception and workshop downstairs and offices upstairs. As the ground floor might have heavy stuff dropped on it, pallet trucks etc I want to have oversized, fan assisted radiators etc. Also for existing buildings it would less disruptive. The UFH upstairs is going on existing concrete floor - and so I think insulation wont be a problem as it is over the heated area downstairs. The first thing to do in will be the UFH pipework i' think I'm going to use the polystyrene preformed slabs with the spreader plates attached and cover it with laminate flooring. I dont want tall people scraping their head on the ceiling and this way I'll see if it works without screeding over the top
    My thought about the method to use solar thermal heating to heat the ground loop water was to run the flow or return through a cylinder like one used to supply domestic hot water with a heating coil supplied by the solar thermal panel. If the solar panel was colder than the water in the loop and therefore the cylinder the solar circulator would be off. if the solar panel was warmer then the circulation pump would run, transferring heat to the ground loop. I dont know how to calculate how long it would take to heat up the water going back into the ground and what material I would have to have for the cylinder to cope with the antifreeze we need in the ground loop
    • CommentTimeAug 25th 2013 edited
    Posted By: mikeambroseThe trouble is the people selling the stuff dont seem to now much about it and the people installing it have all got their own views not all based on fact.
    Too true. I had to size an ASHP after our salesman had promised the Earth. Was not that difficult but took time and care.

    Posted By: mikeambroseI dont know how to calculate how long it would take to heat up the water going back into the ground
    Fairly simple calculation, just the mass of water, the specific heat capacity of water and the temperature difference between the water and the ground. So you will need to know the ground temperature and the water temperature.
    Then comes the tricky bit. How much solar energy can you reasonably expect to collect and when can you collect it. The stochastic nature of cloud cover causes problems here, as does seasonal temperature variation.

    You may be better off designing a system that uses 2 or 3 GSHP or maybe one GSHP and an ASHP or 2 that can be used to 'boost' when needed.
    If the larger system is sized so that it is below the peak demand (say 70% of peak demand), then a smaller system can be used to 'fill in the gaps'.
    It is what happens already except that supplementary heating is used (usually electrical resistance).

    I do think that there a false worry about using resistance heating when needed. The thing about resistance heating is that is is very cheap to install and if used in conjunction with off peak electricity no more expensive than gas.
    There is a company here in Sweden which does an integrated Solar/Heat pump system, here is a link to Google translation of their website.


    I'm rather skeptical as to the financial benefit of installing such a system, for the small increase in efficiency you are looking at a very sizable investment in solar panels.

    I believe the system is sometimes used in a situation where a borehole into bedrock has been undersized or the heat load is greater than anticipated so that the borehole cannot replenish itself naturally during the summer so solar energy is used to assist in replenishing the bore hole. In such a case it would be very expensive to drill a new borehole so solar assistance of the existing bore hole could be the better financial option.

    On the other part of your idea about raising the brine temperature here is an extract translated from another Swedish company Sol & Energiteknik AB.

    "Solar heating for brine circuit / charge collector / emergency cooling
    Raising the temperature of the heat pump brine circuit is very effective. An increase of 3 ° C increase heat pump efficiency by approximately 10%. This is done by means of plate heat exchangers with div accessories. This can be done on all pumps in one way or another, one should be careful with this guide so you do not destroy the heat pump. You should be aware that it takes a lot to raise brinekretsens temp, it has been for small solar thermal system there is no point to do this. Also becomes quite expensive solution. Should be added that several manufacturers produces prefabricated solutions that make it both cheaper and easier to install. When you have this solution can be when there is surplus of solar energy to recharge borehole / ground loop - in a good drill holes where you have good water flow, one should not expect anything more exchange of this, but most see it as a way to solve the excess heat - emergency cooling. If you have a bad borehole / ground loop that does not recharges itself, the bigger idea. On gray days can not solar heat supply heat for example hot water but usually there is then little to give to the brine circuit."


    This company is owned by the heat pump manufacturer NIBE and some of their heat pumps are pre-prepared for this type of installation.

    I'd suggest you contact Nibe UK and ask them about it and if no joy then contact Sol & Energiteknik AB directly.
    Thank you Chris that's really useful stuff. I left a message with NIBE UK after reading a great series of reports from guy on this forum who installed one of their heat pumps in France - I do hope they come back to me most of these people just ignore me - maybe its me. Anyway I need to install a solar thermal panel to get MCS accreditation for it, the thing is there is not much use for hot water in an insdustrial unit but I heard you can get a surprising amount of heat from evacuated tube arrays even in winter and one of the problems you might need to overcome is the overheating of the collectors in the summer. If we use the extra heat generated to warm up the area around the boreholes we can get some of the energy back in the winter and if we can say temperatures above say 10 in the winter we might still be able to help with the heat pump. If all else fails I guess I'll have to have a hot tub in one of the offices !!
    OK so now we're getting somewhere i knew a combination of ground and solar thermal could be good so i hope I hear from Nibe very soon. Next question I want to install the manifold connecting the 2 or 3 boreholes so I can show potential customers what it looks like. My original idea was to have a manifold cover made out of plate glass. We could have this in the middle of the grassed area where we are drilling the holes. I was then going to cover the trench between the manifold and the heat pump as it entered the building in glass. Does anyone know if I would have trouble with condensation if I mounted the manifold on the wall inside the building . I want to be able to show people exactly how it all works together so it cuts out all the nonsense and misinformation. I am going to install data loggers on just about everything so we have a real life example.
    We are at Long Crendon near Oxford, HP18 9RW is our old place HP18 9EJ is the new one but the postcode doesn't seem to work.
    so now I am meeting the guy form Nibe on site on Tuesday I'm going to see if he can give me any information on the Solar thermal connection to heat the brine lets hope he can find out of he doesnt know and then we can get on with things - hopefully I'll hear from Wavin about the underfloor heating stuff for the first floor. The MCS people say to size the heat pump using the ventilation heat loss plus the U values X material area X temp diff between the temperature you want inside and the temperature you get higher than outside for more than 99% of the year. So all that comes to 13.436 KW then in the BS EN 12831 it says to add the reheat energy at 13 watts per square metre ( no real explanation for the source info) so adding that in gives me 15.344 KW. (at 1 degree difference I get at total of 1018 watts without the extra for heatup. For the MCS application process I have to calculate the annual energy requirement among other things so can anyone help me here. I have the monthly mean air temps - I want heat at least 18hrs per day. It shows how things are going wrong with this stuff. The guy that came to sell me a Danfoss system calculated a heat pump size at 8.9KW so if I installed that it would be running out of its comfort zone and give me rubbish COP. One other question if I cant get enough heat from the underfloor in a couple of exposed rooms what would be the problem adding a couple of radiators to beef up the heat output so i can still run at 35 degrees any thoughts?
    At that flow temperature, radiators would need to be very large to make any difference to heat output unless fan assisted. The usual approach is to reduce spacing between pipes where you need more heat output.

    • CommentAuthortony
    • CommentTimeSep 9th 2013
    Or more usually to increase insulation levels.
    • CommentTimeSep 9th 2013 edited
    Have you got the performance charts for the different heat pumps. Then the size of your thermal store (assuming your using one).
    The Weather side of it is pretty easy if you can get decent data, trouble is that generally the monthly data is calculated from min and max range, which tells you very little. If you can get daily data that becomes a lot more accurate. Hourly is better still.

    For the MCS you have to do a room by room as well as an overall building heat loss.

    Had a quick look at the temp data for Oxford, anything below 0°C accounts for 0.6% of the data, below 1°C accounts for 1.5% of the data.
    • CommentAuthortony
    • CommentTimeSep 9th 2013
    HDD data would do I think (heating degree days)
    I need to recheck my figures but assuming they are correct I can get a 3 phase 15KW heatpump from NIBE which can / may have internet reporting and remote control functions and give me a decent COP at 40K flow and 30K return. The guy had not heard of the solar thermal heating of the ground loop water but it appears that the COP calculations are worked out on a theoretical zero K ground loop supply temperature with a 35K average flow & return temp for the heating circuit - no mention of hot water at all no wonder people get it all wrong. I don't understand where all the figures tie up because depending on the efficiency of the ground loop and the running time of the heatpump ( which will change with the weather) you will get all different temperatures going through the ground loop and therefore all different COPS. With the RHI giving 4.8p per KWh with a stated aim of providing purchasers a 10 percent return on investment it doesn't seem to work. Say the install comes to 35K including the boreholes you would need £3500 per year I don't know how many 4.8 pences that is but i'm going to work it out - more later when my head gets better
    • CommentTimeSep 10th 2013
    Or 73 MWh.year^-1

    15 kW run continuously for 12 months is 131.4 MWh.

    Those are seriously low temperatures. I doubt your ground loop will get to zero Kelvin (or -273 degrees Celsius) in our lifetime.

    Even more pedantically: K = Kelvin; k = kilo.

    • CommentTimeSep 11th 2013
    The problem with heat pumps is that there are 3 variables, the ground loop, the heating loops and the heat pump COP, change one and you change the other two, change two and you change the other one in a non-linear way (should be an exponential growth or decay with the exponent being e^t*system properties).
    Without thinking too hard about it I think that the COP is affected more by the ground temperature and the overall efficiency by the heating loop temperature difference
    The ground loop temperature is, in effect, the energy supply and the heating loop governs the amount of time the system runs.
    • CommentAuthorJonG
    • CommentTimeSep 11th 2013
    Hi Mike,

    We are installers of NIBE amongst other units, if you get in touch with your local NIBE rep as opposed to tech, they will produce what is called a VPDIM which is a software model that they have for predicting various parameters based on the design requirements you give them.

    Don't confuse COP with SPF (Seasonal Performance Factor), COP is a one off measure at a single point in time, SPF is measured over a heating season and includes additional peripherals like pumps and immersions, but there are different standards and criteria of what is included all over Europe!

    Heat pump design is relatively simple when you know how, but the there is a great deal to learn to get it right.

    In terms of what I have picked up from a quick prasee of your post, the following high level stuff might help;

    Boreholes have to be dimensioned based on the heat load of the property, run times annually, the brine you intend to use, whether you want hot water too and the geological substrata.

    They have to be at least 5m apart and flows have to be balanced across them, so interconnecting pipe runs to the manifold need to be considered carefully along with header size.

    The heat distribution circuit has to be designed to run at the lowest potential temperature which generally means UFH at very close centres and reduced loop lengths, screed and tile or stone, laminate over spreader plates will require too high a flow temp to be sensible given that you are at start up. Oversized rads are an option but need careful dimensioning.

    In a commercial it is not unusual to use larger diam UFH pipework than domestic say 18mm at wider centres, you could use a supplier but even those who say they are familiar with renewable design often get it wrong in our experience which is why we tend to do our own.

    The property needs to be air tight and preferably well insulated, but definitely air tight.

    Solar thermal does help but the costs do not always stack up in terms of payback. It is feasible to use it to heat the ground loops, which helps the ground recover over the summer, but if you do have DHW, it will be a difficult set up to control and install, because you would have to disconnect 1 while the other was in operation.

    To feed ST to the ground you will need to spec PB pipework to take the heat as opposed to the probes you will get from most places. Go Geothermal can supply these for you, if you want them.

    You could use ST to heat the HW over the summer and rest the ground but we have never been able to make the costs stack up to make it worthwhile.

    In our experience the best heat pump systems are the simplest, especially if its your first. There is also good evidence that the commercial tariff will be upgraded soon, I haven't got the figure to hand at the moment though.

    If you struggle to get in contact with your local NIBE rep, let me know and I'll ask ours who it is.


    Thanks for your help guys its really useful. First of all thanks David I'll use degrees C from now on !!! I'm going to ask Steamy Tea to do the maths when I can work out what I need calculating and Jon your input is great. Going back to the main reason I started on this particular mission of madness, the government introduced the RHI as one of the things they are doing to help them reach their 2020 carbon reductions targets. The stated aim was to give business a 10% return on investment made installing renewable heat stuff. So I arranged a 10 year lease on a typical late 80's industrial unit - 3800 sq foot warehouse 1500 sq foot office / workshop. Now we can install a system, get the benefit of the RHI payments, get MCS accreditation and have a system to train or guys on and demonstrate to potential customers - so its absolutely got to work. I am convinced there is huge potential for this sort of installation - but primarily we need to make sure that the heat pump is running at maximum efficiency all the time because that is where the damage gets done. So surely there must be an optimum increase in temperature between the ground loop input and the heating flow output that gets you the most bangs for your bucks. If there is then perhaps you could have invertors controlling the compressor speed, the brine pump speed and heating pump speed you could have a "cruise control" system - perhaps that's what they do. The very nice man from Nibe could get his software to demonstrate that if you increased the temperature of the brine by a few degrees it increased the efficiency (he said COP) of the system - but all their calculations are based on a brine temperature of 0 degrees C (told you David). My question was if the efficiency increases by so much why don't you have a bigger bore hole that will recover temperature quickly enough to ensure the supply temperature is going to be 3 degrees C not zero I didn't get an answer. I'm going to get there in the end!
    • CommentAuthorJonG
    • CommentTimeSep 13th 2013
    Hi Mike, the VPDIM software can be set up to various parameters, including the differential in brine temps and also the average brine temp. However as you allude the best way to achieve greater efficiencies is to modulate the ancillaries around the compressor.

    We import a heat pump that does just this, the compressor, expansion valve brine pump and heating circ pump all modulate in concert with each other, they also twin pass the refrigerant to pre-heat the return via another heat exchanger before it returns to the condenser.

    It is not uncommon for manufacturers to use modulating pumps now, but very few GS in the UK modulate the compressor, even though it is common on ASHP's. NIBE have a version in Sweden but not here yet.

    The units we import have achieved COP's of 7-9 but not on brine, but they do outperform fixed speed compressor heat pumps.

    The best performing heat pumps are DX where refrigerant is circulated through pipework in the ground or water to water, where 1 well pumps through the heat pump and then out to another well, the water temp is consistently higher than the ground. These are uncommon in the UK and DX does not qualify for the RHI, we are researching branching out into water to water at the moment.

    I have just returned from training in Austria with the modulating units and can size and spec one for you but we would have to install it if you were interested, but they are typically £5-6k above what the regular units cost in the UK. If you wanted to sell them though you would need to be accepted by the manufacturer as a partner.

    We start our first one next month just south of Manchester if you wanted to visit and see it in more depth, failing that ask away and I will fill in the blanks for you as much as I can.

    With any unit though the golden rule is that the source and sink have to be as close to each other as possible, but the economics have to stack up in terms of the return and outlay.

    I saw a case study in Austria where a 1.5km bore hole is being used as the source, and the SPF's are 9, but at what drilling cost! The Swiss have also mastered a system using just water in a closed loop, but again it is tricky to do without ending up with a frozen circuit. CO2 probes are also incredibly efficient but we don't have the expertise or knowledge in the UK to deploy these, we are still just scratching the surface in comparison with Europe (if you pardon the pun).

    PM me for my number if you want to talk.

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