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Heatpumps
For every 1 unit of electrical power the heatpump provides on average 3 units of heat output by moving heat from the air, water or ground into the building.
Carnot COP = (T_condencing+273) / ((T_condencing+273) – (T_evaporation+273))Practical COP = 0.5 x Carnot COP
Average home today
Lighting, Appliances and cooking 10.6 kWh/dSpace heating gas input: 34 kWh/dWater heating gas input: 5.8 kWh/d
Provided by a mix of gas and present grid electric = ~ 5 tonnes of CO2//year
Average ZeroCarbonBritain home
Lighting, Appliances and cooking4.5 kWh/dSpace heating electric input: 4.2 kWh Water heating electric input: 2.3 kWh
Provided by renewable electricat zero carbon
83% energy saving from insulation+ draught proofing + heatpumps
Open source zero carbon energy system modelhttp://openenergymonitor.org/energymodel/
1) Model the heat loss rate of your house
MyHomeEnergyPlanner, open source home energy assessment software, collaboration with Carbon Coop in Manchester who carry our home retrofits saving households 70% on their energy use.http://github.com/emoncms/MyHomeEnergyPlanner
How to design and install a heatpump system
Heat loss rate: 109W/K
When its -1C outside and I want it to be 21C inside it willneed a heat input of:
22K x 109W/K = 2398W
Average requirement is:11K x 109W/K = 1200W
2) Calculate heat emitters required: number of radiator or under floor heating to provide max heat output demand at an efficient heatpump COP
- Radiator datasheets
- Heatpump flow temperature needsto be ideally ~ 35C to 40C to run efficiently
- 1703 W @ 35C- 2231 W @ 40C- 2878 W @ 45C
1x Dimplex smart rad SRX180
0.9 kw @ 10C (30C MWT)1.2 kw @ 15C (35C)1.5 kW @ 20C (40C)1.9 kW @ 25C (45C)2.3 kW @ 30C (50C)2.7 kW @ 35C (55C)3.0 Kw @ 40C (60C)
1x Standard double panel convector
http://www.screwfix.com/p/kudox-premium-type-22-compact-double-panel-convector-radiator-700-x-1200mm/30717
2407W @ 50K503W @ 15K (35C)731W @ 20K978W @ 25K
heat output = rated heat output x (deltaT / rated_deltaT) ^ 1.3
3) Select a heatpump
Many available
5 kW mitsubishi ecodan, more than I need for stage 1 but enough for expansion into other rooms.
One of the smallest heatpumps on the market, has a good record.
3) Misc components:
- Efficient circulation pump- water filter- expansion vessel
Energy monitoring
Total installation cost ~£3000
How well does it work? … open source heatpump monitoring
- EmonPi electricity monitoring
- Kamstrup multical 402 billing grade heat meter, connected to emontx via mbus and open source mbus reader implemented on emontx
- EmonTH internal and external temperature monitoring
From October 17th to November 10th: 24 daysElectric input: 88.9 kWhHeat output: 260 kWhAverage COP 2.92
Average COP of 23 test runs: 3.451 unit of electric in
3.45 units of heat out
Heat cost at electric rate of 16p/kWh = 16 / 3.45 = 4.6p/kWh
Seasoned wood: 5.41p/kWh, Propane gas: 12p/kWh
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