navitron
 
Renewable Energy and Sustainability Forum
Welcome, Guest. Please login or register.

Login with username, password and session length
News: Anyone wishing to register as a new member on the forum is strongly recommended to use a "proper" email address - following recent spam/hack attempts on the forum, all security is set to "high", and "disposable" email addresses like Gmail, Yahoo and Hotmail tend to be viewed with suspicion, and the application rejected if there is any doubt whatsoever
 
Recent Articles: Navitron Partners With Solax to Help Create A More Sustainable Future | Navitron Calls for Increased Carbon Footprint Reduction In Light of Earth Overshoot Day | A plea from The David School - Issue 18
   Home   Help Search Login Register  
Pages: 1 2 3 [4] 5   Go Down
  Print  
Author Topic: One year in... some GSHP numbers  (Read 22209 times)
dhaslam
Hero Member
*****
Offline Offline

Posts: 6775



« Reply #45 on: December 19, 2016, 03:46:39 PM »

Where  heat pumps go wrong  is when they are used  for  jobs they are not equipped to do.   In Northern Ireland there was a group of houses  fitted with ASHPs  that were set to heat  DHW first  but the problem was that in cold weather  they were running constantly trying  to get the water up to  temperature and didn't heat the houses properly.  It  seems that this is a fairly common. 

http://forum.buildhub.org.uk/ipb/topic/507-another-cheap-12kw-kingspan-aeromax-ashp/

A typical ASHP can  produce  4 to 5  kW  with an input of  1 kW in  7/35  conditions  and  about 50% more input when colder  so   if running for 12 hours the most it should cost on average is about  1.25 X 12 X  15p  = £2.25 per day.   However you have to add the cost of bringing DHW from  35C up to 55C  which would take about 2.5 kW of  heat per 100 litres.   
Logged

DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
DonL
Hero Member
*****
Offline Offline

Posts: 570


« Reply #46 on: December 19, 2016, 05:49:39 PM »

Mikel Very interesting about your control system - it's particularly good that you have monitoring equipment to measure the real COP. I would love to know what my system really achieves but without heat measuring equipment I can only guess. Having said that I'm entirely content with the controls I have since I changed the bog standard thermostat for an accurate and programmable one. I drop the setpoint a degree or two over night and the ASHP generally stays off unless weather conditions are extreme. The setpoint is raised again at 6:00 am and the heat pump runs continuously part of the day to get back up to setpoint and then the temperature sits on setpoint until the woodburner lifts the temperature in the evening and the heat pump switches off. Finally, by having a heat pump with inverter drive, it is relatively good at matching heat demand without multiple start/stops and when it does start it is "soft start".

dhaslam I think heat pumps, like any other technology, have to be well designed and operated. Installers may not be very familiar with the technology and the house owners may expect to do things that the system is not designed for. Unfortunately there are quite a lot of bad experiences around which, in my view, is a pity as it may put people off a good solution. A new housing estate just down the road is being built with ASHP's and I look forward to seeing the results. First signs are promising as they are chosing between premium brand heat pumps and the rating looks sensible for a well insulated new build.
Logged

Schuco solar hot water - 3300kWh/annum, 16 BP 4175N PV panels - 2.8kWp, log burner and back boiler and 18 Ying Li 235 PV panels - 4.2kWp, 42kW ground mount PV, 9kW Panasonic ASHP, 40kWh Nissan Leaf
ringi
Full Member
***
Offline Offline

Posts: 162


« Reply #47 on: December 19, 2016, 06:14:58 PM »

Shame that A2A heat pumps are not allowed under RHI, as they give the quick response that lots of people want from a heating system.
Logged
rogeriko
Hero Member
*****
Offline Offline

Posts: 1421



WWW
« Reply #48 on: December 19, 2016, 08:53:46 PM »

[A typical ASHP can  produce  4 to 5  kW  with an input of  1 kW in  7/35  conditions  and  about 50% more input when colder  so   if running for 12 hours the most it should cost on average is about  1.25 X 12 X  15p  = £2.25 per day.   However you have to add the cost of bringing DHW from  35C up to 55C  which would take about 2.5 kW of  heat per 100 litres.   
[/quote]



When it gets cold outside ie 0-2 degrees or your ground loop has cooled to 3-4 degrees, despite what all the manufacturers claim, in the real world you get a cop of 2. If you are heating DHW with a return loop around the hot taps and 6 bedrooms with the thermostat on 22 your electric bill will be more than anyone here can imagine.
Logged

davec
Sr. Member
****
Offline Offline

Posts: 282


« Reply #49 on: December 22, 2016, 06:50:04 PM »

The RHI for heat pumps is only available where mains gas is unavailable.

I remember this being a rule once upon a time but not sure this is still the case. Could you give a reference please?
Logged
BruceB
Hero Member
*****
Offline Offline

Posts: 1044


« Reply #50 on: December 23, 2016, 07:45:15 AM »

I do not believe it was ever a rule.  My recollection is that it was in a consultation, but never implemented.

Certainly now, whether you have gas available or not does not feature in the questions asked when registering domestic or non-domestic rhi. I have installed HPs in gas areas, and rhi is claimed.
Logged
titan
Hero Member
*****
Offline Offline

Posts: 531


« Reply #51 on: February 09, 2017, 08:59:37 PM »

I do not believe it was ever a rule.  My recollection is that it was in a consultation, but never implemented.


Thread is a bit old now, just noticed it !. It was certainly part of my application processes no mains gas was a criteria although that was four years ago and the various schemes seemed to be forever changing. I was a self build that may have been a factor. I had given up on claiming RHI and did the install anyway only to find I actually qualified  for the then latest scheme as my commissioning date was three days after the start of the latest scheme, for once the bureaucracy worked in my favour.
Logged
titan
Hero Member
*****
Offline Offline

Posts: 531


« Reply #52 on: February 09, 2017, 09:04:39 PM »

Figures for 2016  2084 kWh that is 240 m2 heated area and dhw. Heating is on 24/7 30 weeks a year not needed for DHW the other weeks as it is provided by solar.

That is Kensa 8 kW GSHP
Logged
davec
Sr. Member
****
Offline Offline

Posts: 282


« Reply #53 on: December 23, 2017, 11:18:08 AM »

And, five years in....

Year1, Dec-2012/3 was:-
Quote
Total import 8361kWh (3412 high-rate, 4949 low). GSHP heating accounts for about 50% of this (4420); DHW about 10% (Immersion 650 plus heat-pump 216); the remaining 40% is cooking, light, appliances, kettle....

Year2, Dec-2013/4 was:-
Quote
Total import 7845kWh (3226 high-rate, 4619 low). GSHP heating accounts for about 50% of this (3725); DHW about 10% (Immersion 636 plus heat-pump 144); the remaining 40% is cooking, light, appliances, kettle....

Year3 Dec-2014/5 was:-
Quote
Total import 7862kWh (3324 high-rate, 4538 low). GSHP heating accounts for about 50% of this (4221); DHW about 6% (Immersion 343 plus heat-pump 128); the remainder is cooking, light, appliances, kettle, MineCraft....

Year4 Dec-2015/6 was:-
Quote
Total import 8841kWh (3871 high-rate, 4970 low). GSHP accounts for about 50% (4504); DHW about 7% (Immersion 563 + heat-pump 97); remainder much as before.... So, Y4 numbers up on Y3 but not massively out of kilter given that the kids are staying up longer nowadays, leaving lights on and doors open...

Year5 Dec-2016/7 was:-
Total import 8678kWh (3824 high-rate, 4854 low). GSHP accounts for about 50% (4633); DHW about 8% (Immersion 512 + heat-pump 170); remainder much as before.... So, Y5 numbers fairly flat with Y4; slightly more DHW could be because of constantly showering daughter...

DaveC.
Logged
JohnS
Hero Member
*****
Offline Offline

Posts: 2022


« Reply #54 on: December 23, 2017, 02:47:07 PM »

Have you tried comparing your heating energy usage with heating degree day numbers?

http://www.degreedays.net/

Without knowing heating demand, it is impossible to know if you are improving or regressing.

At one stage I contributed weekly gas and electricity consumption data to Oxford University's climate project and they introduced me to degree days.  I used the data to verify that insulation projects and better control systems produced savings.  However, I also found that there were lots of noise in the data.  Eg home with in-laws for Christmas (extra heating) or away for Christmas and then kids off to university - small reduction in demand as their bedroom heating was turned off but reduced free heat from body warmth etc.  And then my retirement meaning I am at home more and therefore heating on more during the day plus feeling the cold more as I age etc.
Logged

2.1kWp solar PV
titan
Hero Member
*****
Offline Offline

Posts: 531


« Reply #55 on: December 23, 2017, 04:47:53 PM »

 I did my initial energy demand projections for our new build  using degree days but and it is a big but it depends on how the nearest weather station  data correlates to your location. Now we live onsite I regularly check the local weather station with my own figures and the weather station (Just 5km away) is consistently 2-3 deg C min temp lower than  we get. Fortunately using their historical figures made the error in the right direction. Degree days are fine but  not foolproof.
Logged
davec
Sr. Member
****
Offline Offline

Posts: 282


« Reply #56 on: December 23, 2017, 07:19:11 PM »

Quote
I did my initial energy demand projections for our new build  using degree days but and it is a big but it depends on how the nearest weather station  data correlates to your location. Now we live onsite I regularly check the local weather station with my own figures and the weather station (Just 5km away) is consistently 2-3 deg C min temp lower than  we get. Fortunately using their historical figures made the error in the right direction. Degree days are fine but  not foolproof.

Aye, thank you, didn't know about degree days; every day is a school day!

I had a look at that website and the nearest 'real' weather station is Edinburgh Airport, only 20miles away but unfortunately at 120m lower elevation, which possibly makes a difference to the threshold temperature? However, I guess from their figures I'll get an indication of any variation from year to year to help interpret any trends in my own data (I'm getting a bit lazy nowadays... used to take readings every few weeks, now 3 months or so).

What I'm seeing in my numbers is that they're pretty consistent over 5 years, whole house demand about 9,000 KWh, about half of which is heating; and that there's no obvious 'creep' that might be a sign of something deteriorating: GSHP, borehole, external insulation, etc.

DaveC.
Logged
gnarly
Full Member
***
Offline Offline

Posts: 146


« Reply #57 on: December 24, 2017, 09:02:33 AM »

Thanks for all the data davec/titan.  What % of the time do these gshp systems run on the very coldest days?  (And do you feel warm enough? - appreciate it is a bit subjective and depends how you have the thermostat set).  Iím asking because I wonder if, in general, the heat pumps themselves are a bit oversized for 24hr operation on the coldest days and in fact you could get away with something smaller. (As long as you have the right approach with leaving it on continuously and not trying to heat up house from cold when you are in it!)
Logged
marshman
Hero Member
*****
Offline Offline

Posts: 948


WWW
« Reply #58 on: December 24, 2017, 10:04:47 AM »

My GSHP has just completed it's second year since install.  1st year consumption was 2330kWh. 2nd year much better at 1599kWh.  10kW Thermia heatpump, UFH, 300 ltr DHW tank.  Heat pump gets the DHW hot enough (55 deg) on its own with no help from immersion heater. I do have a solar diverter which does the hot water in the "summer" months -but is next to useless at this time of year. System runs 24/7. House is old  detached farmhouse (circa 1700's mainly)  but has been substantially renovated with UFH. It is 240 sq m

Much of the improvement has come from triple glazing and installing MHRV so I could stop all the unwanted draughts. We are in an exposed windy spot close to the English Channel.

Ground loop temps seem to be similar to last year at the moment but we shall see as the season progresses.

Gnarly, on the coldest days, recently had a couple of days where temp was -4 deg C over night and 0 deg C in the day (I know it's not as cold as up t'north, but cold enough for us southern softies), the heat pump was running for around 20 mins every hour. I suspect I could get away with a smaller pump but it is nice to have the "grunt" to heat the DHW when everyone is home having showers (4 grown up kids and their partners!).

Roger
Logged

3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
davec
Sr. Member
****
Offline Offline

Posts: 282


« Reply #59 on: December 24, 2017, 10:24:24 AM »

Thanks for all the data davec/titan.  What % of the time do these gshp systems run on the very coldest days?  (And do you feel warm enough? - appreciate it is a bit subjective and depends how you have the thermostat set).  Iím asking because I wonder if, in general, the heat pumps themselves are a bit oversized for 24hr operation on the coldest days and in fact you could get away with something smaller. (As long as you have the right approach with leaving it on continuously and not trying to heat up house from cold when you are in it!)

The longest I've seen the GHSP compressor run is about 7 hours out of 24 when we had several weeks of sub-zero outside. There's a 100litre buffer tank to reduce cycling and it's interesting to note that the circulation pump operated about 17/24 at that time. Downstairs we have ufh and  it feels v. comfortable at 17degC, with 18 in the living room and 20 in the bathroom; upstairs is mostly heated by convection; we just have standard rads at ufh temperature.

But, the way I see it, the rating of the heat source is all about responsiveness... e.g. your normal gas boiler might be rated about 60,000 btu, way more than the running requirement, just so you can bring your rooms up to heat in a short timescale. Heat pumps that are left on all the time, are only required to replace insulation losses so can be rated less. Ours can deliver 9Kw while drawing 2Kw of electricity, which is obviously plenty for our usual needs (I think the next unit down would _just_ have provided for the building design with no contingency, e.g. wind-chill) but would likely take a couple of days to bring the whole structure up to temperature from cold... we just leave the whole system running all the time, supervised by a stack of timing and thermostat settings that churned a lot at first but haven't changed in over three years.

DaveC
Logged
Pages: 1 2 3 [4] 5   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.20 | SMF © 2013, Simple Machines
SMFAds for Free Forums
Simple Audio Video Embedder
Valid XHTML 1.0! Valid CSS!