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Author Topic: Recharging the ground  (Read 20006 times)
Mikel
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« Reply #60 on: February 01, 2016, 04:08:39 PM »

In view of the fact that Roger is beginning to post some actual data and the various comments about not using heat pumps with radiators, I hope you won't mind if I post some of our actual performance for our GSHP working with oversized radiators.

Our property is a bungalow of hybrid origin. It was originally a 1984 2-bed timber-framed bungalow extended in 2006/7 by the previous owners to give a 4-bed bungalow. Total floor area 145 sq.m

We have replaced one bedroom to create a dining room which involved knocking down one internal wall. We have installed a ground mounted PV system, 5.7 kW solar thermal panels on the SSE facing roof and GSHP with 3*40m slinkies laid horizontally 1.2m wide, 1.2m depth. The GSHP does both heating and hot water to 50C. The hot water tank (new) is 305L.

We had a very long discussion with our installer on the pros and cons of slinkies versus continuous loop versus borehole. Our installer was strongly of the opinion that provided the ground collector was correctly sized then it didn't really matter which method was used from the heat performance perspective. The installer advised that boreholes were very much more expensive and slinkies avoided the need to join pipe work underground.

The GSHP and solar thermal system was completed in March 2013.

In January 2014, we joined a DECC sponsored trial of heat pump control systems. This meant that we had an electricity meter put on the heat pump, a heat meter installed on the heat pump and various temperature sensors put up around the house. There were a number of modifications made to the heat pump (made with the agreement of the manufacturer so that there would be no issue with warranty).

In August 2014, we would in a wood burner in the lounge, with prior consultation of the organisation running the trial.

So how does this all work in practice?

For the first year we set the room temperature to 18C and total GSHP electricity consumption was approximately 1600 kWh. For the second year, I set the room temperature to 0.5C above that which gave rise to complaints!! This has turned out to be 17C. GSHP electricity consumption for the second year is about 1400 kWh.

A major reason for the drop in electricity consumption for the second year has been this milder winter. For example, GSHP daily electricity consumption for Dec 2014 was 10.09 kWh and for Dec 2015 6.45 kWh.


The overall figures for electricity consumption for domestic hot water are:

2014
GSHP 179 kWh
Immersion 100 kWh (16 times at once per week to heat to above 60C to control legionella)

2015
GSHP 224 kWh
Immersion 94 kWh (15 times at once per week)

We find that we begin to use the GSHP regularly for DHW from about the fourth week in October until mid/late Feb and the Immersion for a similar period.

So how do the CoP figures work out?

It is not worth quoting figures for the CoP outside of Nov-Mar as the use becomes much more intermittent and there appears to be a pump running on occasion during the day over the Spring/Summer/early Autumn months even when the heat pump is not on and consumes between 0.1-0.3 kWh/day. We have put this down to some wiring with the solar thermal system being  on the same circuit as the GSHP electricity meter.

Since March 2014, the trial control system has been in operation. We had about one month of data under the original control system, which gave a CoP of 3.2. I haven't bother to quote the CoP for Mar 2014 because it was  right at the start of the trail.

2014-5 Monthly CoPs

Nov 2014 3.59
Dec 2014 3.50
Jan 2015 3.46
Feb 2015 3.47
Mar 2015 3.46

2015-6 Monthly CoPs

Nov 2015 3.52
Dec 2015 3.57

I don't think these figures are bad for a radiator system although I would expect an underfloor system to perform even better.

Incidentally, there was one week in November 2015 when we just used the heat pump for DHW. The CoP for that week was 2.98.

and now for some pictures

This was yesterday's run and the effect of the wood burner is quite noticeable (after 6pm)





And this was for the 28th January. We had been away for a few days and this shows how the house heats back up.






And this shows a month of heating


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Stuart Ian Naylor
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« Reply #61 on: February 01, 2016, 05:42:38 PM »

Thought I would post this as the elevated temps of DHW can cause problems with CoP output.

http://www.kensaheatpumps.com/new-hybrid-gshp-engineered-by-kensa/

Quote
Kensa’s twin compressor Hybrid heat pump harnesses the properties of two separate refrigerants in its compressors to deliver heat outputs similar to those provided by Kensa’s Standard models, along with hot water temperatures typically produced by their High Temperature models.

Its great to get some figures and some brilliant data being posted. I am confused slightly to the figures we are getting as I thought there would be an initial sharp drop in temp and then a noticeable leveling of brine input temp.
What I expected is the static loop has stood still for some length of time and its at the same temp as the geology.
Its pretty damn cold at the moment so maybe a continuous run for 3 or 4 loop circuits, might give more resolution, have a Bali theme night or something Smiley

Would be good if you copied what the PV guys do and maybe post your monthlies from a group of GSHP enthusiasts. If you can in any way simulate local freezing by extended use, please do.     
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Fionn
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« Reply #62 on: February 01, 2016, 06:05:34 PM »

Great data Mikel, nice to hear that the oversized radiators are proving effective.

Ian, The stable input temperature just indicates that the ground loop is more than sufficient for the heat demand on it.
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Stuart Ian Naylor
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« Reply #63 on: February 01, 2016, 08:30:57 PM »

Great data Mikel, nice to hear that the oversized radiators are proving effective.

Ian, The stable input temperature just indicates that the ground loop is more than sufficient for the heat demand on it.

Marshman, Roger Smiley posted some mega details, that actually confused me.
What he did by deliberately cutting off loop sections was absolute gold in terms of info.

I said it earlier but if we got data from a bodged GSHP that returned data of freezing characteristics, then actually that would be really useful, even if a bit upsetting for the owner.

The brine cooled solar PV system Billie showed is a renewable symbiotic relationship where the cold and heat are shared and simultaneously benefit both systems.  

ORCs and Sterlings are the same and recharging the ground is very possible in a certain manner especially if instantaneous or of a short duration between charge and extraction.
« Last Edit: February 01, 2016, 08:34:45 PM by Stuart Ian Naylor » Logged
mike7
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« Reply #64 on: February 02, 2016, 12:57:41 AM »

Below 10m is geothermal as it is constant irrespective of seasonal air temp or as years pass by. So its the temperature of the geology and not the above environment (Unless climate change or distance to the sun...). Well GSHP sources say 10m, geological sources say 15m.
Deeper you go, it just gets hotter, but only 2.6'C per 100m.
Probably it matters not a cuss, but the reason it's constant at 10m or so is because that's deep enough to damp out the seasonal variations. If the seasons were longer you'd have to go deeper to find a steady temperature. The reason it is 10'C or so is because that's the average surface temperature over a year, allowing 0.26'C for the geo bit.
 
Staying in nerdmode, if the temp gradient is 2.6'C/100m and the conductivity is 3W/mK, geothermal heat will be escaping to the surface at 0.072 W/m2, which means 14000 m2 per kW. Phew - that's slow!. No wonder the world is still hot inside. You'd need a lot of borehole for true geothermal, so I'd say a real life one is mostly solar and only with a significant bit of geo if its really deep.

...And another thing.  The effectiveness of ground heatstores is dependent more on the diffusivity of the ground, or conductivity divided by the heat capacity per cube, rather than just the conductivity alone.
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billi
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« Reply #65 on: February 02, 2016, 03:57:24 AM »

Great data Mikel, nice to hear that the oversized radiators are proving effective.

Ian, The stable input temperature just indicates that the ground loop is more than sufficient for the heat demand on it.

Marshman, Roger Smiley posted some mega details, that actually confused me.
What he did by deliberately cutting off loop sections was absolute gold in terms of info.

I said it earlier but if we got data from a bodged GSHP that returned data of freezing characteristics, then actually that would be really useful, even if a bit upsetting for the owner.

The brine cooled solar PV system Billie showed is a renewable symbiotic relationship where the cold and heat are shared and simultaneously benefit both systems.  

ORCs and Sterlings are the same and recharging the ground is very possible in a certain manner especially if instantaneous or of a short duration between charge and extraction.


I would honestly like   to have a better translation program .....    but this did not work  and they talk about an Ice storage idea with a CoP over 4  and the overall over 5.5   with the hybrid solar thermal  connected  and this all with system losses  excluded

http://www.agenda-energie-lahr.de/Ph2_SolarWP-GOT.html    paste it in guugle tanslate  , perhaps it makes more sense then


But i follow that since years and    perhaps  therfore i am a PV fan boy   cause its black, cheap and  works better if cold down by a heatpump 


Regards Billi
« Last Edit: February 02, 2016, 04:05:55 AM by billi » Logged

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Stuart Ian Naylor
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« Reply #66 on: February 02, 2016, 07:54:08 AM »

Below 10m is geothermal as it is constant irrespective of seasonal air temp or as years pass by. So its the temperature of the geology and not the above environment (Unless climate change or distance to the sun...). Well GSHP sources say 10m, geological sources say 15m.
Deeper you go, it just gets hotter, but only 2.6'C per 100m.
Probably it matters not a cuss, but the reason it's constant at 10m or so is because that's deep enough to damp out the seasonal variations. If the seasons were longer you'd have to go deeper to find a steady temperature. The reason it is 10'C or so is because that's the average surface temperature over a year, allowing 0.26'C for the geo bit.
 
Staying in nerdmode, if the temp gradient is 2.6'C/100m and the conductivity is 3W/mK, geothermal heat will be escaping to the surface at 0.072 W/m2, which means 14000 m2 per kW. Phew - that's slow!. No wonder the world is still hot inside. You'd need a lot of borehole for true geothermal, so I'd say a real life one is mostly solar and only with a significant bit of geo if its really deep.

...And another thing.  The effectiveness of ground heatstores is dependent more on the diffusivity of the ground, or conductivity divided by the heat capacity per cube, rather than just the conductivity alone.

I think its important to distinguish between vertical and horizontal GSHP coils. If it is geothermal or not is a bit of a pint half full argument as the average seasonal air temp is pretty constant or otherwise we get a bit panicky and call it climate change.
Deep bores => 15 - 200m+ can be said to have a constant ground temperature. Horizontal =< 15m follow the above air temperatures.
That is really important as the bore loop can be used to provide cooling to renewables to increase their efficiency. This differs from any previous seasonal heat store that used the used the bore for extracting warm energy which isn't that efficient.
So its important to differentiate between Vertical and Horizontal in design and data capture and Geothermal and Solarthermal pretty much describe what is going on with vertical and horizontal bore loops.

Ground source heat pumps work, they need long lengths of pipe and the depth of this pipe provides some very predictable temperatures over prolonged extraction periods.
You can see it works because ground source heaters works. Where it all goes wrong is when we start looking any further than the localised mass around that tube.

I think a separate thread for you GSHP owners would be interesting and extremely informative. I am using Geothermal and Solarthermal as a distinction as when posting datasets that info is important.
That way if you really wanted to get Geeky and do some calculations on the ground structure knowing depth is very important.
I am really not sure about Slinkies as because of the loops there is a much bigger mass of brine m2.
Reading through the other thread there is a debate about Slinkies and maybe that should be included in datasets.

Because of the information posted here you can go through and see that a GSHP has much effect on the ground in close proximity to the piping.
What effects it most is heat flux and time of use and there is a fine balancing act needed for pipe length.

That system Billi posted with the chilled PV is a direct system with the shortest amount of time and in terms of "recharging" is the most efficient in the "recharging" process.
The cold heat from the GSHP directly cools the PV system this is fed into the ground in a ground loop of appropriate size.
In summer because the ground is cooler than air even with the GSHP off (which is prob the norm) it receives cooling and bonuses in efficiency.
When the GSHP is on it has a huge direct cooling effect and the heat from the PV has a lot of brine mass over a small PV area and is very effective for both systems.

Roger posted some great info that over short periods of time you can effect the collected brine temperature and this can be mentioned in hours.
The longer you extract for in hours reduces the flux between brine feed and localised mass after a while the effect is diminished.
If you can freeze it for a few hours, you can heat it for a few hours and short term cycles of a few hours are possible.

You can get effective results for a few hours and in terms of usage profile that is quite a reasonable fit.
The recharging the ground argument always gets derailed when either the recharge camp start talking about huge quantities over extensive periods. Or the anti camp start quoting figures other than localised mass in terms of a couple of hours.

Now if we had a extended dataset of 12 hours continuous run on say something like the one Roger supplied on the 1,2,3 loop capacity of the system the argument could be settled.

The figures you quoted Mike have a limited effect on the recharge cycle if its of a short duration.
   
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davec
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« Reply #67 on: February 02, 2016, 08:08:23 AM »

Quote
Probably it matters not a cuss, but...

Applause for diffusivity!
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Stuart Ian Naylor
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« Reply #68 on: February 02, 2016, 11:06:49 PM »

Great data Mikel, nice to hear that the oversized radiators are proving effective.

Ian, The stable input temperature just indicates that the ground loop is more than sufficient for the heat demand on it.

Marshman, Roger Smiley posted some mega details, that actually confused me.
What he did by deliberately cutting off loop sections was absolute gold in terms of info.

I said it earlier but if we got data from a bodged GSHP that returned data of freezing characteristics, then actually that would be really useful, even if a bit upsetting for the owner.

The brine cooled solar PV system Billie showed is a renewable symbiotic relationship where the cold and heat are shared and simultaneously benefit both systems.  

ORCs and Sterlings are the same and recharging the ground is very possible in a certain manner especially if instantaneous or of a short duration between charge and extraction.


I would honestly like   to have a better translation program .....    but this did not work  and they talk about an Ice storage idea with a CoP over 4  and the overall over 5.5   with the hybrid solar thermal  connected  and this all with system losses  excluded

http://www.agenda-energie-lahr.de/Ph2_SolarWP-GOT.html    paste it in guugle tanslate  , perhaps it makes more sense then


But i follow that since years and    perhaps  therfore i am a PV fan boy   cause its black, cheap and  works better if cold down by a heatpump  


Regards Billi

After having some terrible results pasting the link into google translate did a good enough job https://translate.google.co.uk/#auto/en/http%3A%2F%2Fwww.agenda-energie-lahr.de%2FPh2_SolarWP-GOT.html

Yeah nothing wrong with PV and the reason I reopened a dead thread is that generally the recharging concept looked at being the primary heat source.
I have read enough reports and followed seasonal heat sources from when they where initially posted on here.

Mike is right about the diffusivity as its extremely hard to store quantity over extended periods of time.
But be it PV, ORC, Sterling, GSHP efficiencies can be increased and just a couple of degrees can make a lot of difference.
The diffusivity of the mass near the brine loop can be seen in Rogers results where I guess if he runs for long enough with all three coils the same downward slope in heat collected will be shown.
Never had a long enough run on that coil loop to see when its affected.

It does look like you can change the temperature of the ground of a small localised mass near to the pipe by a couple of degrees for a couple of hours.
When you get two renewable technologies sharing the same ground loop with opposite effects of freezing and heating you can double up on the "recharging" efficiencies.
You can't expect much more than a couple of degree's that will last longer than a couple of hours, but you can.

Solar PV is cheap and it allows enthusiasts to quickly and easily generate CO2 free energy.
Currently Solar PV converts at approximately 16% whilst low tech Solar thermal can reach 70%.
That is really important for areas of low insolation as PV needs four times the space to produce the same amount of energy as SolarThermal.
Its just a shame that practically all solar thermal panel systems had a sole purpose of heating a singular heat store (cylinder) and this often limited the size to an extremely small area.
Also its a shame the solar thermal was also exclusively a direct heat system where collected temperature was heating temperature as this limits the amount of heat stored in a certain area.

I have a building shape that is my ideal solar optimised UK building, its a 3 storey single aspect terrace with a mono pitch roof that provides a good average living space.
8m wide, 10m to the rafters and 4m in depth with a 35' monopitch roof giving another  8m x 5m area. Its just some silly theoretical of a house totally cladded by solar panels on the south aspect.
With a total of 120m2 collection area where solar PV = 120m2 * 1kwh * 16% (area x average solar * efficiency) = 19.2kwh
Solar thermal = 120m2 * 1kwh * 70% (area x average solar * efficiency) = 84kwh.

Now that is based on some silly solar optimised house where walls and roof are completely clad and this is the huge problem in the UK domestically as many of us have extremely limited space applicable for any type of solar.
Solar thermal is still much more likely to produce usable energy levels seasonally on the average available space and create a summer excess, whilst looking at the Dec/Jan PV results this isn't so.

I am still a big fan of Solar Thermal coupled to a daily heat store (not of the ground type) coupled to an ORC backed up by a GSHP.
The heat store acts as a buffer where generation time is delayed by a couple of hours which helps massively in balancing.

Solar PV in areas of low insolation is a really great consumer renewable but for bigger commercial and community concerns its returns are not great and much less than Solarthermal / ORC or Solarthermal / ORC / GSHP systems in terms of space available.

Bugs me we never got the right type of panels and innovation / investment was so skewed to a singular type of solar technology whilst maybe a more appropriate complementary technology was available.
Having a generation lag between a solar PV and solar thermal PV makes for a much better UK solar profile. Much of the skew has been caused by having approved technologies rather than rewarding recorded energy profiles of a more open market.

http://repository.tudelft.nl/assets/uuid:2e17121a-d138-4c14-bf1f-421799602beb/PhDTesis_ECasati.pdf
« Last Edit: February 03, 2016, 02:28:55 AM by Stuart Ian Naylor » Logged
billi
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« Reply #69 on: February 03, 2016, 03:27:00 AM »

in the end  or better on the long run     PV 

what a success  story   ,


 sure thermal solar as well  , not a doubt


But   if people  here report  of about 1400 kWh  electricity  for the whole house heating  whistlie x 0.17pence .......................... bike


So 200 -£300  per year    even if its more 




Why should i charge the ground   ?  and not the Grid with Units ?


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Stuart Ian Naylor
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« Reply #70 on: February 03, 2016, 05:40:51 AM »

If we don't get a balance in generation profile like germany we could very well end up where the grid charges us.

There might be a few homes that only use 1400 kWh electricity for whole house heating.

The average UK home isn't really changing much with the majority of new builds being the EPC rating C (which I totally disagree with)

https://www.ovoenergy.com/guides/energy-guides/the-average-gas-bill-average-electricity-bill-compared.html

Recharging just helps make other processes more efficient to lessen the grid charge to you, whilst helping with balancing because of delayed energy storage.

In solar thermal it is only the waste heat in the cooling process that recharges the ground, but as a CHP system is massively more efficient over PV alone.

If we all adopted PV with maximised coverage we would have huge problems in balance, cost and storage.

Its fine to point at a singular system and state what it does alone is fine and dandy, but for it to work as a whole for the UK it ain't going to work and we need diversity.

Complementary systems to PV are not better ways of doing things but have equal importance because diversity of energy profile.

Non centralised heat grids in CHP combinations are far more efficient and there are many technologies that can radically make difference in conjunction with PV.

Anything that can bring balance with storage costs at the moment has high value and worth more than a unit that can not.   
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dhaslam
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« Reply #71 on: February 03, 2016, 11:37:02 AM »

It seems that that of buildings tested in England and Wales  two thirds  are below level C.    However what seems to happen is that the  less well insulated houses are heated to a much lower temperature.      In  a larger proportion of houses are new  and proportionately more self builds   

http://www.lcea.co.uk/epc-ratings-explained/

In Ireland a larger proportion of houses are new  and proportionately more self builds.  One half are C or better    and only one quarter worse than D.

http://www.seai.ie/Your_Building/BER/BER_FAQ/FAQ_BER/General/BER_Statistics.html

However what seems to happen is that the  less well insulated houses are heated to a much lower temperature. If that wasn't the case the heating cost for older houses would be  astronomical.    I doubt if anyone in old farm houses spends  €8000 per annum on heating.   The usual thing is a few  loads of turf costing  less than €1000 per annum.           

http://www.seai.ie/Your_Building/BER/Your_Guide_to_Building_Energy_Rating.pdf


Unfortunately the energy ratings don't mean very much because they mix up the  heat requirement with the heat source 
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« Reply #72 on: February 03, 2016, 09:17:36 PM »

Nice lot of data Mikel. Unfortunately I don't have a heat meter fitted, I now wish I had for my own curiosity. (another project!).

Good to know that your system works well with radiators. It sounds as though your installer, like mine, realised the importance of correct ground collector sizing.

I didn't see it in your post but do you run your system 24/7 or is it on a timer?  Also is there a room stat to control the temperature?

Mine runs 24/7 and the temperature inside the house is remarkably constant apart from a mild uplift if we light the wood burner - which my wife finally admitted the other night was more for the nice effect of the flames rather than because she was cold! See graphs below (last 3 days recorded by my weather station) - indoor temp is in maroon on the bottom graph.



I love the relatively quick response of your system after you came back from holiday. My place would probably take the best part of 24 hours to stabilise due to the enormous thermal mass - but then again that's probably why the internal temp stays fairly constant.

One last question. Do your CoP figures come from the monitoring system or have you calculated them from the heat meter reading & electricity meter?

Roger
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« Reply #73 on: February 03, 2016, 09:36:56 PM »

Nice lot of data Mikel. Unfortunately I don't have a heat meter fitted, I now wish I had for my own curiosity. (another project!).

Marshmans Christmas prezzie sorted!
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Mikel
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« Reply #74 on: February 04, 2016, 03:53:56 PM »

Roger, thanks for your comments. I'll provide short answers and more informative answers to your questions.

You asked:

"One last question. Do your CoP figures come from the monitoring system or have you calculated them from the heat meter reading & electricity meter?"

The figures are calculated from the electric and heat meter readings.

You asked:


"I didn't see it in your post but do you run your system 24/7 or is it on a timer?  Also is there a room stat to control the temperature?"

The short answers is : Yes, yes and yes!!  I'll explain.

When originally installed we had a timer fitted and weather compensation turned on and no room thermostat. We generally don't need any heating on during the day living in West Cornwall unless it is very damp. I didn't see much point in putting the timer on for the DHW, as we are at home during the day and can operate it manually to benefit from the solar thermal system.

When we opted for the DECC sponsored control system trial, they made a number of additions to our setup as follows:

Their communication box was connected to our router and various sensors and meters setup to send data to the communication box;
Four temperature sensors were installed, one in the lounge, one outside of the kitchen, one in another hallway and one in the guest bedroom;
One temperature sensor is designated as the control sensor. Originally this was in the lounge but designation was moved to the hallway sensor when the wood burner was put into the lounge;
Electricity meters were fitted to the heat pump and to the main meter;
A heat meter was fitted to the heat pump;
Additional parts were installed on the heat pump (all done with the agreement of the manufacturer and does not invalidate the warranty);
The heat pump was wired so that it could be switched from trial mode to original mode minus the weather compensation;
A wireless enabled timer/scheduler was installed;
Control software updates could be applied remotely to the heat pump;
A copy of the monitoring data is sent to me weekly and I use this to calculate the CoP.


So how does this operate in practice?

Whilst we have set a daily and weekly timed schedule with differing temperatures set for In, Out and Asleep, in practice the only variables from the user's perspective that control the system are the temperature setting and the holiday times. The control software would initially learn how our property responds to heating and then it selects the best method for achieving the set temperature (best method also includes an overnight heating time for those to be able to benefit from a lower tarrif) and it also takes into account the external temperature and the forecast temperature. It also brings the house back up to temperature for when we return from holiday.

One very significant difference between this trial control system and the original is that the heat pump tends to run continuously for longer periods and up to quite high flow temperatures (45-50C) with the trial system. Originally, it would cycle about 5 times an hour with lower flow temperatures.

In terms of measured performance, the calculated SPF for RHI purposes comes out at 3.1. I have data for Feb 2014 only under the original system and that gave a CoP 0f 3.2 and under the new system we are regularly getting between 3.4-3.5 plus the heat pump is cycling far fewer times.

I did originally start to record the incoming and outgoing temperatures to the ground loop but now only look at these occasionally (last week during a mid-run the incoming temp was 10.7C and the outgoing 3.1C).

It was interesting to see your graphs. I do not record any weather data. We are only a few miles from a Met Office station that records local weather.

Mike
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