Objectives Energy savings and reduction of CO 2 -emissions: By the use of low valued and environmentally sustainable energy sources for heating and cooling of buildings. Through utilization of the EXERGY concept
Low temp. supply 55 °C 0 1 Space heating Domestic hot water Sauna Appliances, Lighting 1 0 Fossil fuels, electricity Energy demandEnergy supply District heating 115 0 C Low temp. supply 55 °C Ultra low temp supply 40 °C Source Source: VTT Energy quality q Why exergy? - Matching of the energy quality of demand and supply
Approach: Exergy concept matching the Quantity AND Quality levels of supply and demand Quantity Energy savings Quality use of low quality sources e.g. solar thermal heat, ground/air heat
Analyses tools for LowEx systems Software tools for an energy/exergy assssment 7% exergy fraction of the energy
Biomass, floor heat. Cond. boiler, radiators. GSHP, floor heat. Power primary energy Non renewable Benchmarking of system solutions
Power primary energy Biomass, floor heat. Cond. boiler, radiators. GSHP, floor heat. Non renewable Renewable Benchmarking of system solutions
power primary energy / exergetic fraction exergy fraction energy Biomass, floor heat. Cond. boiler, radiators. GSHP, floor heat. Renewable Non renewable Renewable Non renewable Benchmarking of system solutions
Limit LowEx ideal Exergetic fraction of the primary energy power WP Exergy demand of zone Biomass, floor heat. Cond. boiler, radiators. GSHP, floor heat.
Low Exergy Buildings? Match quality levels of supply and demand by exploiting low quality, waste or environmental sources...but LowEx buildings are not Passive House buildings...no combustion in buildings Air heat recovery unit Q end = 70 kWh/m 2 a Q end = 16 kWh/m 2 a Q H = 15 kWh/m 2 a Q H = 60 kWh/m 2 a Source: ETH, Meggers Passive house
...no combustion and minimum high exergy (primary energy) input minimize primary energy: by exploiting low quality, waste or environmental sources Passive houseLowEx house Air heat recovery unit Ground source heat pump Q end = 16 kWh/m 2 a Q H = 40 kWh/m 2 a Q end = 6 kWh/m 2 a Q H = 15 kWh/m 2 a 40% solar fraction Q H = 40 kWh/m 2 a Source: ETH, Meggers Low Exergy Buildings?
Heat/cold emissioning systems and storages Building systems: Examples
Building systems: Example Ground heat exchanger (mainly for cooling) Energy poles Bore holes Horizontal heat exchanger Horizontal heat exchanger with capillary tubes Source City of Kassel, Germany Source WH Zwickau, Germany
Steady state exergy assessment of buildings A parameter study Buildings: 2 office buildings Simplification: Office use only Supply systems: district heating and heat pump Heating case only Method: Building data collected via developed templates Steady state analysis via EBC Annex 49 tool User profiles, climate data, energy demand: estimated via the German DIN V 18599-10
Energy- und Exergyflows 25. February, 10:00, T env. =-4,6°C, No Shading Primary- energy conversion Generation Storage Distribu- tion Room air Building envelope Emission Spec. energy/exergy [W/m²]
Primary- energy conversion Generation Storage Distribu- tion Room air Building envelope Emission Energy- und Exergyflows District heating (non renewable) Heat pump (ground coupled)
Concluding remarks 1.Exergy demands for heating/cooling are very small - Energy demands are high. 2.Supply as low exergy as possible to the room space avoid combustion processes and minimize electricity input 3.Find suitable low-exergy sources in the immediate/local environment. 4.Development of system-components and their smart integration are necessary
Why exergy? 1.Exergy is not an “universal” indicator! But: based on thermodynamics 2.Gives it differences in building design? Yes: compared to forced air systems No: if low temperature hydronic systems considered 3.Good news: Not all existing buildings need to be passive houses! Therefore:
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