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Author Topic: One year in... some GSHP numbers  (Read 21944 times)
davec
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« on: February 01, 2014, 09:57:59 AM »

When we started looking into ground-source for our house renovation, it was difficult to find any 'real' examples to help specify a system and estimate expected performance. Now we've been living with it for a year, here's some numbers.....

The original building is stonebuilt, renovated with -200mm wood-fibre EWI and modern wood-clad extension; roof insulation also -200mm wood-fibre. Ground floor around 160sqm with 150mm kingspan, wet UFH and -170mm screed; upstairs around 125sqm with just normal-sized radiators run at the same temp as the UFH. We have 300 litres unvented DHW with 40*ET solar thermal, 55degC Heat-pump feed and 60degC immersion inputs. We also have 2kW of PV. EPC shows estimated annual heating = 16552kWh, DHW = 1749kWh.

Heat pump is rated 9kW with a 2kW draw; source is a single borehole; there's a 100L buffer tank. We have an Economy-10 supply and fitted extra meters to monitor immersion and GSHP.

Total import 8631kWh (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....

I hope this will help others trying to do realistic sums....

Davec.
 
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regen
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« Reply #1 on: February 02, 2014, 09:33:29 AM »

Hi Dave,

Are you achieving about 4 to 1 on the GSHP and heating a 285m2 house for about 500 or is my interpretation a bit out.  If so seems an excellent result. 

Regen
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3.92w freestanding PV with sb3300 +Imersun
21kw Stratford T70 woodburner
 300litre thermalstore with 3kw and 1kw immersions
 Wall star 25kw oil boiler
  Spring water supply with uv and ro membrane
 Sheep, poly tunnel and approx 80 sq m of raised veg beds.
daserra
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« Reply #2 on: February 02, 2014, 11:52:00 AM »

The renovations sounds like the perfect type for a heat pump, highly insulated, large thermal mass in the UFH and ground source not air source. How deep and wide is the borehole?
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Rammed earth/ytong PassivFrankenHaus.
In the hills in Southern Portugal.
Borehole, on-grid.
Home made pool solar.
davec
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« Reply #3 on: February 02, 2014, 04:47:04 PM »

Quote
Are you achieving about 4 to 1 on the GSHP and heating a 285m2 house for about 500 or is my interpretation a bit out... 

Aye, annual efficiency over 3.5, if the EPC estimate is accurate... total electricity cost for last year was 1075; heating accounts for about 550.

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How deep and wide is the borehole?

220m deep, 115mm wide with 40mm flow and return pipes.

Davec.

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dhaslam
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« Reply #4 on: February 02, 2014, 07:25:01 PM »

What range of input temperatures are you getting?
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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
clockmanFR
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« Reply #5 on: February 02, 2014, 07:32:35 PM »

Hi davec.

Really interested in:-

Maintenance costs and offset budget for replacement?
Embedded costs, ie cost of install if done commercially.?
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oliver90owner
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« Reply #6 on: February 02, 2014, 08:31:47 PM »

Wow, that is some deep hole!

Or did you mean 67m?

RAB

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davec
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« Reply #7 on: February 02, 2014, 09:03:51 PM »

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What range of input temperatures are you getting?

HP displays return temp rather than input temp. This shows 9degC at rest and 5degC when running. I've not noticed any seasonal variation.

Quote
Maintenance costs and offset budget for replacement?

So far no maintenance except check pressures which I can do. Heat pump should be good for 20 years, replacement cost is not too scary; borehole is more scary but should be good for 50.

Quote
Embedded costs, ie cost of install if done commercially.?

Can't really disconnect these costs from the overall renovation job which was very much driven by the renewables.

Quote
did you mean 67m?

No, 220m, see "Boring" in this topic for more info.

DaveC




 
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daserra
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« Reply #8 on: February 02, 2014, 09:25:05 PM »

Very deep (and expensive) hole I should imagine. Did they line it with anything? The deepest water borehole I've organised here was 320m and that cost the price of a new car !
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Rammed earth/ytong PassivFrankenHaus.
In the hills in Southern Portugal.
Borehole, on-grid.
Home made pool solar.
clockmanFR
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« Reply #9 on: February 02, 2014, 09:44:32 PM »

"Can't really disconnect these costs from the overall renovation job which was very much driven by the renewables".

That's a shame.

 Would liked to have known true embedded costs and therefore true heating costs. Cost of bore hole?, cost of pipes and fittings?, circulation pump and its motor kW,? the heat pump unit itself and its power draw?, tanks that are needed and other embedded costs.?

Would be nice to compare to my underfloor 3kw electric heating matts that heats my main house, it has minimum embedded costs of about 400, including thermostats and my auto circuits. Electric is from my Turbines and PV.
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titan
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« Reply #10 on: February 03, 2014, 01:10:23 PM »


 Would liked to have known true embedded costs and therefore true heating costs. Cost of bore hole?, cost of pipes and fittings?, circulation pump and its motor kW,? the heat pump unit itself and its power draw?, tanks that are needed and other embedded costs.?

Would be nice to compare to my underfloor 3kw electric heating matts that heats my main house, it has minimum embedded costs of about 400, including thermostats and my auto circuits. Electric is from my Turbines and PV.

What about the embedded cost of your PV  and 2 ( or three) turbine installations and your time of course building your turbines and trackers plus the equipment needed welding machines  and consumables etc. Getting a true cost comparison would be difficult. Electric mat heating is efficient but expensive if mains electricity is needed.
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clockmanFR
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« Reply #11 on: February 03, 2014, 06:25:57 PM »

Here we are titan,

5kW PV Sharpe seconds, 2kw Yingli, 2,600.
3 trackers 1800 for the 5kw PV. (includes all cables etc)
2 Mppt PV controllers, 750.

3off. 3.7m turbines at total 3,200.

1300ah 48v batteries, 1400.
3.7kW Inverter, 150.

u]Grand total just under 10,000[/u]

Commercially, depends on the greed and profit margins.

All stuff is available and is DIY and absolutely no need for specialist equipment. Aldi do a welder Tod and Biff have one , somewhere at 50?

My time? no I send the Mrs CM out to work nowadays.  Grin
« Last Edit: February 03, 2014, 06:28:01 PM by clockmanFR » Logged

Everything is possible, just give me TIME.
titan
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« Reply #12 on: February 03, 2014, 07:21:28 PM »

I can give some costs for my GSHP and UFH

GSHP + 125ltrs antifreeze  4500, 500M of 40mm geothermal pipe 500 fittings for manifold 150, Sand for surrounding pipe 600 ( not normally needed but my ground is mudstone UFH pipe manifold, controls, pump etc 2500 grand total 7750. I have my own JCB.

Energy  to run GSHP 1st Jan to 31st Dec 2013 providing heating all year and DHW 8 months 2507 kWh house is 240m2 within the heated envelope, Heating is only on ground floor but heats whole house. There is also 60m2 insulated but unheated basement where GSHP and utilities are.
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davec
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« Reply #13 on: February 03, 2014, 08:22:17 PM »

Do you have any EPC or MCS numbers that would let you work out the annual efficiency of the Heat Pump?

Davec.
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titan
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« Reply #14 on: February 04, 2014, 09:48:20 AM »

Do you have any EPC or MCS numbers that would let you work out the annual efficiency of the Heat Pump?

Davec.

I don't think the  EPC or MCS figures would be accurate enough to calculate a COP from. The EPC was needed for a PV installation, it gave 17,290kWh for heating. The MCS figure for the GSHP gives 14.400 kWh and my calculations give 16,229kWh for heating. I based my projected yearly figure on degree days from the local met office weather station ( 6km away)  but having checked their temperatures daily over the last 18 months find in winter that they are quite often 1-3 deg C colder than I see at night which may account for my higher calculated figure. The only way to calculate COP is with a heat and electric  meter, anything else is a guess. The figures above would give COPs between 5.7 and 6.9 which is clearly unrealistic.
This year has started well, the milder weather and ( possibly) some adjustments I have made to the GSHP have resulted is a 42% reduction over last January's figure.
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