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Low Energy Building Design Presentation 3- Demand/Supply Matching Marc Smeed Edmund Tsang Graham Dow

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DEMAND REDUCTION START CIBSE ‘TYPICAL PRACTICE PRIMARY SCHOOL’ FOSSIL FUELS 164 kWh/m2 p.a ELECTRICITY 32 kWh/m2 p.a

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AIR TIGHT CONSTRUCTION Assumptions Heating Period External Temp= 8.6 ° C 1 Design Internal Temp= 21°C MetricInfiltration Rate (m 3 /m 2 ACH 2005 CIBSE Part L Regs Tight Building Very Tight Building Calculated Heat Loss, per m 2 per hour = 4.04W/m 2 h Calculated Heat Loss, per m 2 per hour = 1.61W/m 2 h Saving = ( )/4.04 * 100% = 60% Energy Saving = 27.2 kWh/m 2 p.a. 1. ESP-r data output: (Average external temp for heating season)

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DEMAND REDUCTION FOSSIL FUELS 164 kWh/m2 p.a AIRTIGHTNESS SAVING 27.2 kWh/m2 p.a SUB-TOTAL136.8 kWh/m2 p.a CIBSE ‘TYPICAL PRACTICE PRIMARY SCHOOL’

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HEAT RECOVERY Heat Recovered = 17.7 kWh/m 2 p.a. Assumptions External Temp= 8.6 ° C 1 Design Internal Temp= 21°C Exchanger ε s = 65% 2 Occupied days per year= Occupied hours per day= 8 Ceiling Height= 3m Total Building Ventilation Rate = 1.5 ACH q s = ε s *m min *C p *(∆T) = 65%*( *1.284)*1.014*11 = kW/m 2 Heat flow rate through sensible heat exchanger 4 Occupied hours in the year = ESP-r data output: (Average external temp for occupied hours) 2. CIBSE Guide F: Table 4.6,p ASHRAE Handbook 2004: Chapter 44

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DEMAND REDUCTION FOSSIL FUELS 164 kWh/m2 p.a AIRTIGHTNESS SAVING 27.2 kWh/m2 p.a HEAT RECOVERY 17.7 kWh/m2 p.a SUB-TOTAL119.1 kWh/m2 p.a CIBSE ‘TYPICAL PRACTICE PRIMARY SCHOOL’

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DEMAND REDUCTION FOSSIL FUELS 164 kWh/m2 p.a AIRTIGHTNESS SAVING 27.2 kWh/m2 p.a HEAT RECOVERY 17.7 kWh/m2 p.a BEMS 2 nd Sem. kWh/m2 p.a SUB-TOTAL<119.1 kWh/m2 p.a CIBSE ‘TYPICAL PRACTICE PRIMARY SCHOOL’

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79% FOSSIL FUELS LIGHTING CONTROL Assumptions 1. 21% ELECTRICITY

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LIGHTING CONTROL Assumptions 1. LIGHTING = 10/21 % OF ELECTRICAL LOAD = 47% = 15.2kWh/m 2 p.a.

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LIGHTING CONTROL Energy Saving= 5.33 kWh/m 2 p.a. 1. Occupancy sensors can reduce lighting load by 30-40% 1 This can rise to 75% if integrate with PSALI 1 Therefore we can assume that we could obtain at least 35% reduction. 35% X 15.2kWh/m 2 = 5.33kWh/m 2

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DEMAND REDUCTION ELECTIRICITY 32 kWh/m2 p.a PSALI / PIR 5.3 kWh/m2 p.a EFFICIENT LIGHTING 2 nd Sem. kWh/m2 p.a BEMS 2 nd Sem. kWh/m2 p.a LIGHT SHELVING 2 nd Sem. kWh/m2 p.a SUB-TOTAL<26.7 kWh/m2 p.a CIBSE ‘TYPICAL PRACTICE PRIMARY SCHOOL’

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ENERGY STORAGE

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FLYWHEEL A rotor is accelerated, maintaining the energy in the system as inertial energy Maximum Power rating of 2000KW for a multi-cabinet type Maximum Power rating of 500KW for a single-cabinet type Stored energy discharges at a maximum time of 2 minutes

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FLYWHEEL- FEASIBILTY ADVANTAGES –Flexible –Commercially available –High power outputs DISADVANTAGES –Safety concerns –Short discharge times –Expensive

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HYDROGEN STORAGE The 3 key elements are Electrolysis Mechanism Hydrogen Storage Fuel Cell Hydrogen stored via Pressurised storage Ammonia Metal hydrides

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FEASIBILITY High storage capacity- around 165 KWh /m 3 Only pressurised hydrogen storage is currently available for building use Other storage only commercially available for vehicles Expensive

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THERMAL ENERGY STORAGE TWO TYPES Sensible –A Tank underground, used for heat storage (25kWh/m^3) Latent –Higher energy density (around 100kWh/m^3) –Phase change materials (PCM) used where it solidifies during night then melts during the day

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Demand Shifting

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Purpose of Demand Shifting Demand shifting makes use of storage so that peaks and troughs of demand are levelled off Requires intelligent forward thinking Can be remotely managed system and use predictions to help shift loads

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What's to be gained Throttling a CHP system is not required Constant power generation can be attained, decrease maintenance problems Can help incorporate renewable systems

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DEMAND SHIFTING FOR RENEWABLES Demand shifting can be used to create demand when it suits a renewable supply. For Example- Solar works when there are higher levels of solar intensity- i.e. in the summer/midday.

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Energy Electrical Appliances (Fuel Cell/CHP) Lighting (Daylight Use) (Fuel Cell/CHP) Heating Space (None) Water (Solar Thermal) Energy Electrical Appliances (Fuel Cell/CHP) Lighting (Daylight Use) (Fuel Cell/CHP) Heating Space (Thermal storage/Solar Thermal Fuel cell/CHP) Water (Thermal storage/Solar Thermal Fuel cell/CHP) Energy Electrical Appliances (Fuel Cell/CHP) Lighting (Daylight Use) (Fuel Cell/CHP) Heating Space (Thermal storage/Solar Thermal Fuel cell/CHP) Water (Thermal storage/Solar Thermal Fuel cell/CHP)

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SHOULD WE DECOUPLE ? FORAgainst Seen as a flagship project towards decentralised supply Why decouple when we could have the grid as a backup Encourage the use of renewable systems It’s a city centre location any excess electricity could be sold Know where our energy comes from Grid Supply could be used to meet demand peaks Attract more grant money and better staff Auxiliary backup system could over complicate design

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VISION What is going to be different about our School ? –A ‘HYDROGEN’ school –A DECOUPLED school A NEW approach to school design

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Any Questions ?

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