MCS Based Design for GSHPs –
“Horses for Courses” GSHPA Energy Expo – Stone – Sept 2017
Robin Curtis – GeoScience Ltd
Dog ‘n Pony Show
Robin – on “MCS”why / how / what / when / where
Chris – on “not‐the‐MCS” approachwhy / how /when /where
Objectives
‐ Background setting‐ Underlying reasoning & approach‐ The MIS‐3005 design “products” ‐ Focus on the ground loop sizing &‐ Hydraulics
New ground loop sizing toolsfor Domestic GSHP installationsin the UK
Robin Curtis & Tom Pine ‐ GeoScience Ltd. Chris Wickins ‐ UK Dept. of Energy & Climate Change
EGC – Pisa June 2013
1st UK Closed Loop GSHP Domesticinstallation
1995 Devon (~8kW)
22 years ‐ 1st routine maintenance/inspection this year. (apart from air‐filter changes)
Revise guidance for all domesticheating heat pumps (MIS 3005) For all heat pumps (ie ASHPs and GSHPs):
Improve building heat loss estimation
Produce a Heat Pump Emitter Guide
Require ~ 100% heat pump sizing(for mono‐energetic systems)
Ground parameters
ffBuilding thermal loads
Available space Heat pump / SPFFlow rate / min EWT
Total ground loop length+ spacing
Code ‐ for say, 20 years
Hydraulics – SPF2?
Costing
Energy assessment for closed loop GSHPs–“THE” fundamental
difference(compared to all fossil fuel boilers, direct electric, and ASHPs )
Your worryNot dealing with it here ‐
Other than:
1) FLEQ’s
Annual kWh / heat pump size kW
Ground impact ?
2) Estimated SPF (heat emitter guide)
Ground impact
Underlying philosophy
• Conservative• Simple – available to all• Paper based – no HW/SW version issues• Domestic heating + DHW only (<45kW)• To obtain acceptable SPFs• Not the best or cheapest
Previous methods ? Some use of software, eg EED, GLHEPRO, GLD, CLGS
European manufacturers’ software
VDI 4640
The well known ROT method
Concerns ? Relevance to UK conditions ?
“Ground” rules
100% sizing – for mono‐energetic systems
Minimum entering water temperature(EWT) O°C(after 20 years) – to maintain SPF
Boreholes Fixed parameters:single 32mm U‐tube, specified borehole resistance, minimum spacing defined
Variable parameters:
Ground equilibrium temperatureThermal conductivityAnnual thermal loads (Run hours / FLEQ)
Boreholes
Over a (UK relevant) range of k, ground temperature and FLEQ
Run: EED, GLHEPRO
Make some check comparisons with VDI 4640 and GLD.
Ground loop sizing….
Geo En er gy
NB – for domestic sub 45kW ONLY – heating only
Draft Issue 1.0 (24/08/2011)
5.0
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2.0
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Mean annual air temperature for UK regions (oC)
14
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Maximum power to be extracted per unit length of borehole heat exchanger (W/m) with 3600 FLEQ run hours
Conditions for use:Heat extraction only (inc. hot water)
6m minimum borehole spacing. Only valid for boreholes arranged in a line; not applicable for a large number of systems in a small areaTable created assuming: 130mm borehole diameter; single U-tube; 32mm OD SDR-11, PE100 pipe with thermal conductivity = 0.420W/m/K; 52mm pipe centre-pipe centre
shank spacing; 25% Mono Ethylene Gylcol thermal transfer fluid; Re > 2500 in the borehole active elements; thermally enhanced grout with thermal conductivity = 2.4W/m/KAssumptions result in borehole thermal resistance = 0.1 m.K/W at 12oC mean ground temp. and 2.5W/m/K average ground thermal conductivity
Horizontal systems Conventional EU style loops (Serpentine) , and SlinkiesFixed parameters: Geometrical layouts and pipe sizes defined.
Variable parameters:Ground equilibrium temperatureThermal conductivityAnnual thermal loads (Run hours / FLEQ)+ Temperature “swing” and depth
Horizontal systems Over a (UK relevant) range of :k, ground temperature and FLEQ
Run: CLGS
Make some check comparisonswith VDI 4640 and GLD.
Hydraulics ‐Pressure dropcomponents:
1) Active element(s)2) Headers3) Heat pump4) + contingency/fittings
Hydraulics ‐fixed parameters
• Heat pump flow rate • Non‐laminar – (transition zone)• min % Anti‐freeze
Hydraulics ‐the variables
• Borehole/loop lengths vs number• Pipe diameter • Borehole pipe configuration (1U / 2U)• Header arrangements
Flow Rate (l/s)
P r e s s u r e D r o p ( k P a / m o f P i p e )
0.00
0.05
0.10
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0.20
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0.50
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0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
00.1
0.20.3
0.40.5
0.60.7
0.80.9
11.1
1.21.3
1.41.5
1.61.7
1.81.9
22.1
2.22.3
2.42.5
2.62.7
2.82.9
33.1
3.23.3
3.43.5
3.63.7
3.83.9
4
SDR11 Header Pipework -Ethylene Glycol (-10°C)
System curve + pump curve
0
5
10
15
20
25
30
35
0 2 4 6 8 10 12Flow rate
Pre
ssu
re d
rop
or
Hea
d
System curvePump curve
The deliverables:
1) flow charts
2) pressure drop charts
3) accompanying design guide
for: 2 pipe types2 antifreezes2 freeze protection limits@ various pipe diameters
Links to all of these resources are given in the paper.
Methodology should be applicable to any other country / region.(?)
Awaiting incoming criticism /comment/exocets >
>>>> Revision / update
Design Day vs Monthly Loads
Design Day (EqFLH)CoolingkW
HeatingkW
0800‐1200 0 142.0
1200‐1600 0 59.7
1600‐2000 0 59.7
2000‐0800 0 59.7
EqFLH 0 2,896
Monthly LoadsHeat Gains Heat Losses
Month Total kWh Peak kW Total kWh Peak kW
Jan 0 54,628 142
Feb 0 52,137 Mar 0 48,869 Apr 0 40,931 May 0 28,791 Jun 0 19,141 Jul 0 0 13,693 Aug 0 14,160 Sep 0 18,207 Oct 0 29,258 Nov 0 41,242 Dec 0 49,491
Heat Pump Properties
MIS 3005• Assumes you calculate the COP at the design condition and apply that to the building load
• So it returns Heat of Extraction
• No corrections for flow rates
Design Software• Holds data for,
• Source temperatures• Load temperatures• Source flow corrections• Load flow corrections• Heat Pump limits
• Extrapolates & Interpolates from published data
Ground Conditions
MIS 3005• Inputs,
• Undisturbed Ground Temperature
• Conductivity
• Fixed,• Diffusivity
Design Software• Inputs,
• Undisturbed Ground Temperature
• Conductivity• & Conductivity Averager• Diffusivity• & Diffusivity Averager• TRT Data & Processing
Pipes & Pumps
MIS 3005• Basically all fixed,
• 130mm bores• 32mm pipes• 25% MEG• Limited horizontal options
• Turbulent• 2.4 W/mK grout
Design Software• Inputs,
• Circulation Pump Loads• Fluid Properties• Pipe Diameter• Placement in Bore• Horizontal geometries
• 6 pipe, 4 pipe etc• Grout properties• Flow Conditions
• Laminar ‐ Transition ‐ Turbulent
The Effect….
• Block of Apartments• 142 kW, 2,896 EqFLH• MIS 3005
• 24 x 169m• 6m spacing
• Actual Design• 24 x 193m• See layout right• BUT it will work!