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Thermal Potential in the Built Environment

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HVAC systems have traditionally used the local ambient air (heating and cooling) or fossil fuels (predominantly heating through combustion) as their heat source and heat sink. Thermal storage is still a relatively new application and typically requires large volumes of water or ice.

This paper explores the available thermal potential within the built environment and how the utilisation of this thermal potential can provide efficient heating, cooling and hot water as well as thermal storage. In some instances, this may be the local ambient air, less likely it will be fossil fuels.

More likely, it includes the thermal potential within the ground, water bodies and infrastructure such as subways, water, sewer, building foundations and other buildings as well as artificial thermal storage such as phase change materials.

The key is to identify the optimal thermal sources, sinks and storages for a given building at a given location and climate. Then, an integrated approach using optimised control strategies, including predictive capabilities, will enable a building to access these various thermal sources at the thermally optimal time to provide significant energy savings and enhanced operation.

Such an integrated approach also maximises the availability of on-site renewable power generation, further increasing energy savings, decreasing the typical cooling peak demand and increasing energy productivity.

Published in: Engineering
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Thermal Potential in the Built Environment

  1. 1. THERMAL POTENTIAL WITHIN THE BUILT ENVIRONMENT: Identifying locally available heat sources, heat sinks and thermal storage Yale Carden (M.AIRAH, M.IGSHPA) GeoExchange Australia Pty Ltd
  2. 2. Presentation Overview  Future of HVAC: Disruption or evolution?  Parallels with the energy sector  What is thermal potential?  Types of thermal potential  Case Study: Thermal potential and energy productivity  Summary
  3. 3. Disruption or Evolution?  Thermal is energy too – and it can be renewable!  Smaller systems per sqm using local thermal potential  Energy sector: Disruption as large centralized systems and organisations  HVAC sector: Evolution as smaller, decentralised systems and organisations
  4. 4. Parallels with Energy Sector Energy Sector HVAC Sector Decreasing Demand Decreasing Demand Local Energy Potential Local Thermal Potential Energy Storage Thermal Storage Decentralising Systems Centralising Systems Matching Electrical and Thermal Energy Profiles – Energy Productivity
  5. 5. Parallels with Energy Sector Decreasing Demand  Decreasing Energy Demand:  Higher efficiency appliances, including HVAC;  Behavioural changes;  On-site generation;  More efficient buildings;  Thin Grid Concept: grid is back-up to local (renewable) generation.  Decreasing HVAC Demand:  Improved Building Design;  Better Building Materials (insulation, glazing etc);  Building modelling for sizing systems;  Behavioural changes;  Controls and temperature set points;  However, offset by:  Higher design criteria for climate change; and  Higher volumes of fresh air
  6. 6. Parallels with Energy Sector Local Energy and Thermal Potential  Local Energy Potential:  Building or Regional Scale;  Solar Gain;  Wind;  Geothermal;  Hydro;  Wave / Tidal;  Cogen / trigen.  Local Thermal Potential:  Going beyond fossil fuels (heating) and ambient air (heating / cooling);  Understanding local environment;  Infrastructure (eg sewer, subways);  What are the neighbours doing?
  7. 7. Parallels with Energy Sector Energy Storage  Energy (electrical) Storage:  Batteries;  Building scale;  Utility scale.  Energy (thermal) Storage:  Hot / chilled water;  Ice storage;  Ground;  Phase Change Materials.
  8. 8. Parallels with Energy Sector (De)Centralising Systems  Decentralising Energy Systems:  Large, centralised (coal) being gradually phased out;  Smaller, regional, decentralized systems in areas of high energy potential;  Building specific energy systems;  District scale energy systems.  Centralising HVAC Systems:  Individual HVAC system per building is the norm;  Increase in district heating / cooling systems;  HVAC as a utility service at building or district scale.  Will we see similar scale systems in future?
  9. 9. Parallels with Energy Sector Matching Electrical and Thermal Energy Profiles  All electric systems;  Model hourly thermal load demand profile;  Model energy (electric) potential profile;  Identify local electrical and thermal sources;  Apply storage systems to provide gaps;  Theoretically - match thermal demand with energy potential.
  10. 10. What is Thermal Potential  Locally available thermal energy that can be used as:  Heat source (heating)  Heat sink (cooling)  Thermal energy storage  Is typically constant, stable, mostly renewable;  Includes the ambient air, ground, water bodies, sewer, building foundations, infrastructure, other buildings;  Mostly excludes burning of fossil fuels;  Optimal solution is likely a hybrid approach.
  11. 11. Ambient Air  Historically most common;  Most climate dependent;  Air sourced heat pumps;  Cooling towers (wet or dry);  Direct air exchange with heat recovery.
  12. 12. Ground and Water Bodies
  13. 13. Energy Piles
  14. 14. Sewer Heat Recovery  Also includes wastewater / treated effluent  Not just heating – cooling also possible  20-25C heat source / sink is common  Match ‘water’ flow to heating / cooling requirements  Local projects using treated effluent:  Hobart Aquatic Centre, Hobart  Grand Chancellor Hotel, Hobart
  15. 15. Aquifer Thermal Energy Storage Source: www.building.co.uk
  16. 16. District Systems
  17. 17. Case Study: Riverina Highlands Building  Riverina Highlands Building Energy Efficiency Project (RHBEEP) objectives:  Reduce energy expenditure  Reduce reliance on imported energy  Reduce GHG (Green House Gas) emission  Improve comfort levels in the building  What we did:  GeoExchange HVAC/GSHP system installed  Lighting upgrade  Sub metering  Ceiling insulation  Solar PV
  18. 18. Case Study: RHBEEP Results  Building energy savings: ~80 % and $94 000 per annum  HVAC energy savings: ~71 % and $85 000 per annum  Maintenance / tenancy savings: ~$80 000 per annum  Electricity demand reduction: 75 % (Geoexchange - 49 %)  GHG Reduction: 79 tCO2  Simple Payback: ~7.6 years  Return on Investment: 11-12 %
  19. 19. Case Study: Thermal Energy Storage 0 5000 10000 15000 20000 25000 30000 35000 40000 0 2 4 6 8 10 12 TotalLoads(kWhrs) Time (Months) Cooling (kWhrs) Heating (kWhrs) Short term storage: Simultaneous or diurnal Annual storage Heat Rejection Heat Extraction Heat Rejection
  20. 20. Summary  Interesting parallels between energy and HVAC Sectors;  Thermal potential is use of local resources whether natural or anthropogenic;  Thermal potential is heat sink, heat source and storage;  Ideal system balances thermal demand profile with energy potential profile  Objective is enhanced energy productivity
  21. 21. Thank You and Questions… Contact Details Name: Yale Carden Company: GeoExchange Australia Phone: 02 8404 4193 Email: ycarden@geoexchange.com.au Website: www.geoexchange.com.au

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