GROUND SOURCE HEAT PUMP The overall hot water and space heating requirement of the dwelling is 8,500 kWh P.A. With the use of Solar thermal collectors this is reduced to 2579 kWh P.A. A ground source heat pump shall be used to cover the rest of the heating requirement WW3500 by Calorex provides a CoP of 3.64 when taking water from 10 degrees to 55 degrees. A conservative CoP value of 3 was taken in calculation. The heat pump can supply 2579kWh water heating for 859kWh of electrical energy P.A.
OVERALL ENERGY PROFILE Energy (kWh/day)JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember Heating Demand32.3621.869.10000003.0320.5232.4 Solar Thermal Energy Gain4.638.89.10000003.035.623.26 Heat Pump Demand9.244.35000000004.969.71 Electrical Appliance Demand7.6 Total Electrical Demand16.8411.957.6 12.5617.31 Solar Energy Gain1.352.53.564.815.675.465.174.934.082.71.630.95 Wind Energy Gain34.5034.545.9234.50 25.1534.50 25.15 Total Energy Gain35.8537.0649.4939.3140.1830.6139.6839.4438.5937.2336.1426.10 Excess Energy Gain19.0125.1141.8831.7132.5723.0132.0731.8330.9829.6223.578.78 The energy demand is shown in sequence per month. At no time does demand exceed gain.
The house can sustain a 3-7 days storage using a Raylite M-Solar 2V 1380Ah battery. This allows for building autonomy on days where there is no wind or sun. Storage Raylite M- Solar 2V 1380AhJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember Total Electrical Load16.8411.957.60 12.5617.31 Days of Storage Required222222222222 Battery capacity (kWh)66.24 Battery capacity at 80% DOD (kWh)53 No. Of Batteries Required0.630.450.28 0.470.65 No. Of Days Storage Achieved3.144.436.96 4.213.06
OVERALL ENERGY PROFILE Taking into account all heat and power generation technologies the demand of the house is 3635kWh/year. This is equivalent to 20 kWh/m2 floor area per year. Energy kWh/PA Demand3635.238035 Generated13679.30667 Excess10044.06863
EXCESS ENERGY In this house we generate much more energy than we need. Using the Feed In Tariff we can acquire wealth through generation and exporting energy. It is possible to calculate the pay back time of the renewable energy generation technologies given these average figures.
ENERGY SYSTEMS PAY BACK TIME The cost of all energy systems technologies within the house was totalled up and weighed against their savings. The pay back time for the energy systems within the building is 16.22 years After the technologies have paid for themselves they will generate £4000 income for the family through the Feed In Tariff and energy savings. Money Spent £ Energy Systems65750 Money Saved £/PA Materials272.45 Electricity402.43 Heating124.67 Energy Systems3252.02 Total4051.58 Buy back time (Years)16.22
BUILDING RATING BREEAM Ecohomes 2006 (replaced by CfSH in England/ Wales, still used in Scotland) Pre-Assessment Tool used Energy values obtained from SAP worksheet, 2005
BREEAM ASSESSMENT BREEAM Element Library INSULATIONCLADDINGPLASTERBOARD A+ A
WALL INSULATION PROFILE U-Value = 0.13 W/m 2 K Thermal lag time = 10-12 hours Advantages: Positive Carbon Value- straw bale absorbs carbon in growing process Thermal properties of a heavyweight structure (heat flux time delay) Low sound transmission (thickness of straw bale acts as excellent sound dampener Airtight and vapourtight as per PassivHaus standards
ASSUMPTIONS Zero-carbon emissions Drying space provided indoors All appliances (fridges, washing machines, etc.) A+ energy rating Efficient external security lighting with day-light/ motion sensing Cycle storage provided (garage) Surface runoff collected or attached to municipal drainage system Low-risk flood zone (95m elevation on hill) Finishing materials- locally sourced timbers Internal and external recycling bins provided High sound insulation value of straw bale Energy Efficiency User Guide supplied with home Construction contractor must work to Considerate Constructors Standard Security to PAS24-1 Standard and achieved Secured by Design (SbD) award
DRAWBACKS / IMPROVEMENTS Rural location- poor transport links. Ecohomes does not give consideration to use of electric vehicles Rural location on existing field- slight damage to local ecology Consultation must be undertaken with an accredited ecological expert to ensure minimising of ecological damage Consideration can also be given to techniques to enhance local ecological value Building footprint ratio 1:1 (single floor)