Karl Drage
Chairman
Ground Source Heat Pump Association
Operations Director
Geothermal International
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Coefficient of Performance
Coefficient of Performance
- What is it?
- What can be expected?
• What is CoP?
– Efficiency by any other name
– The refrigeration cycle
– CoP versus SPF
• What is to be expected?
– Dynamic System
– Measuring CoP
– Standard data points
• How to get better Economy
– Insulate. Insulate. Insulate.
– Use Less. Use a Lower Temperature.
– Control
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Efficiency by any other name
Efficiency by any other name
• Input = Petrol
• Output = Miles
• Input = Gas
• Output = Heat
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Coefficient of Performance
• The steady-state performance of an
electric compression heat pump at a given
set of temperature conditions.
Coefficient of Performance
• “How much heat do you get out per unit
electricity in?”
Output = Heat
heat capacity
COP =
electrical power
• Or:
Input = Electricity
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Ground Source Heat Pumps
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The Refrigeration Cycle
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Seasonal Performance Factor
Coefficient of Performance
versus
Seasonal Performance Factor
• The operating performance of an electric
heat pump over the season.
Sum of the delivered heat
SPF =
Sum of the electricity consumption
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What is to be expected?
Important running parameters
•
•
•
•
Evaporation pressure
Condensation pressure
Superheat in the inlet to the compressor
Hot gas temperature at compressor
discharge
• Sub cooling after condenser
• In and out coolant temperatures
• In and out ground loop temperatures
• Dynamic System
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Factors effecting performance
Measuring COP
• Climate
– Annual heating and cooling demand
– Maximum peak loads
• Auxiliary energy consumption
– Pumps, fans, control
• Sizing of the heat pump
• Trying to capture a steady state in a
dynamic system
– Fix as much as possible
– Dual temperature probes
– Pressure drop conversion to flow rate
– Heat demand
– Operating characteristics
• Heat Pump and building control systems
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Example COP Data Points
Measured COPs
• WaterFurnace EKW17 – Heating mode
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St Catherine, Near Bath
How to get better Economy
• Large barn conversion
• Take ‘normal’ building design measures
first
• 1 x EKW06 & 1 x EKW17
heat pump units
• 4 x 80m trenches
– Insulation. Insulation. Insulation.
– Windows and doors
– Solar gain
• Underfloor, radiators &
domestic hot water
• Annual fuel savings – up to
£2000 against an oil system
• Commissioned 2005
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Gearrannan Black House Village,
Isle of Lewis
• 50 C underfloor temp COP = 3
• 40 C underfloor temp COP = 3.5
• 30 C underfloor temp COP = 4.6
It is not linear. Every degree C lower is more
percentage points of cost savings on annual
fuel bills.
• 3 x EKW17 heat pump units
• 6 x 90m bore holes
• Underfloor, radiators &
domestic hot water
• Annual fuel savings up to
£4200 against a gas system
• Commissioned 2005
•
•
•
How to get better Economy
• Use Less! Use a Lower Temperature!
• Renovation of 6 houses & Café
•
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Gloucester Police HQ
How to get better Economy
• Control
System:
– Vertical, Closed Loop
Size:
– 860kW Cooling
– 640kW Heating
Collector type:
– 150 boreholes
– Depth 98m
Completed:
– 2005
– ‘Off’. The UK is a mild Country.
– ‘On’ for longer at lower temperatures is
generally better.
– Understand the Heat Loss dynamics of
your building and design controls to suit.
– Balance heating and cooling if possible.
– Avoid complexity.
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Eastbourne Terrace, London
Conclusion
• System:
– Open Loop
• What is CoP?
• What is to be expected?
• How to get better Economy
• Size:
– 1.0MW Cooling
– 1.0MW Heating
• Collector type:
– 4 boreholes
– Depth 121m
– Some case studies
• Completed:
– 2005
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Plas Maldwyn Developments,
Newtown
Osleston, Derbyshire
• New build
• System:
– Vertical, Closed Loop
• Size:
– 35 x 8kW
– Heating & Cooling
• Collector type:
– 35 boreholes
– Depth 98m
• Completed:
– 2006
• 1 x EKW12 heat pump unit
• 2 x 64m bore holes
• Full underfloor heating &
domestic hot water
• Annual fuel savings – up to
£1200 against an oil system
• Commissioned 2005
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County Cork, Ireland
• New build
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Walsingham Church,
Norfolk
• 1 x EKW17 heat pump
unit
• 1 x EKW12 heat pump unit
• 7 x Horizontal ‘slinky coil’
trenches
• 3 x 90m bore holes
• Full underfloor heating
• Full underfloor heating &
domestic hot water
• Run costs less than 1 Euro a
day
• Annual fuel savings –
up to £1300 against a
gas system.
• Commissioned 2001
• Commissioned 2006
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Chelsea Building Society HQ
Alexandra Park School, London
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•
•
•
System:
– Vertical, Closed Loop
Size:
– 120kW Cooling
Collector type:
– 20 boreholes
– Depth 100m
Completed:
– 2004
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•
•
•
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System:
– Vertical, Closed Loop
Size:
– 490+380kW Cooling
– 190+290kW Heating
Collector type:
– 108 boreholes
– Depth 98m
Completed:
– 2006
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Eaton Place, London
• System:
– Open Loop
• Size:
Questions……….
– 120kW Cooling
– 120kW Heating
• Collector type:
– 2 boreholes
– Depth 120m & 18m
• Completed:
– 2004
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