© Fraunhofer IBP Auf Wissen bauen Energy vs exergy use in buildings Fraunhofer Institute for Building Physics (IBP) Department Energy Systems Christina Sager Tekn. Dr. Dietrich Schmidt

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 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

Maximum energy efficiency in buildings ZUB in Kassel Good insulation standard Solar-optimized facade Effective sun protection Thermo Active Building Systems Passive cooling Demand regulated ventilation Good comfort Low energy consumption © Konstantin Meyer

Thermo Active Building Systems ZUB in Kassel Two systems Heating and cooling with concrete core activation or floorheating system Each circle individually controllable Heating with district heating Passive cooling via ground slab © Fraunhofer IBP

70 39 Endenergy: heating [kWh/(m²a)] Endenergy: electricity Typical office building Target value EnBau Consumption ZUB Maximum energy efficiency in buildings ZUB in Kassel © Konstantin Meyer © Fraunhofer IBP These result have been obtained because of EXERGY thinking

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

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:

© Konstantin Meyer