12th International Symposium on District Heating and Cooling

The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, EstoniaMETHODDefinition of building and system build upIn this exemplified case, the main chosen building is anapartment building. This building category seems to bethe most representative concerning heat use amongthe building categories defined in the EPBD [1].In the shown example, the size of the building ischosen to be 1000 m² floor area since this size shouldbe rather representative and be a good compromisebetween the previous and the proposed new recast ofthe EPBD. [2]A building of these features corresponds to a threestoreys squared building with four flats of about 80 m²per storey.In this setting, the total heating system efficiency in thebuilding is built up based on the differentiation betweenthe three main parts of the system. It must be definedwhere the substation is located in the building, i.e.where the heat is exchanged from the distributionnetwork – DH stage in Figure 2. The heat supply to theheating system within the building from the districtheating system is assumed to be provided by two heatexchangers and hot water storage defined as thebuilding substation part of the system.Finally; once distributed, the heat is emitted accordingto the demand. For the present case, the heat isdelivered either by radiators (80/60 ˚C) in the basecase, floor heating (35/28 ˚C), or domestic hot water at60 ˚C. Figure 2 gives a further visual explanation. Forthe present paper, the supply of heat is just done by ahydronic heating system. The possible heat loss fromthe distributed air is neglected since the temperature ofthe air is assumed to be slightly lower than thetemperatures in the rooms.Categories of buildingThe presented analysis shows results for five kinds ofbuildings described in the EPBD which are: singlefamily house and apartment block, office buildings,hotel and restaurants, educational buildings andhospital buildings. When it comes to heat consumptionfor these buildings, the measurements performed inLinda Pedersen‘s PhD thesis [3] show that theconsumption of the apartment buildings is about116 kWh/m², while hospitals use 150 and officebuildings use 100 kWh/m². These measured valuesinclude the domestic hot water (DHW) and the spaceheating (SH) consumption.The calculated efficiency for the system will depend onthe size of the building as well. The present apartmentbuilding shows a higher efficiency value than a singlefamily house with the same consumption. This is due tohigher relative losses in the substation.Climate influenceThe calculations in the present paper are based on aclimate like in Oslo, Norway. This climate is defined tohave approximately 5100 degree days with 20 ˚C asthe internal reference temperature and an externaldesign temperature of -20 ˚C [8].Ventilationair+●•2010/05/RU+ +DHCWIn practice, the outdoor climate can vary widely fromplace to place. Owing to this, the outdoor climateaffects not only the heat consumption but also therelative losses. In general the relative losses areincreasing with an increased ratio between the degreedays and ΔT between the dimensioning internal andexternal temperature.Hot tapwaterdistrib.Roomheatingdistrib.SubstationsystemborderFigure 2 Sketch of the system elements for production,distribution and conditioning of the roomsFrom the substation, the hot water is distributed eitherfor air and space heating or as domestic hot water.Both uses are provided by their own heat exchangerand the necessary pipelines will now be referred to asdistribution pipelines.239The average outside temperature affects the heatconsumption and the temperature variations affect theregulation of the heat emitters. This means that duringcold periods, the temperature of the supply water tendsto be increased imposing an increase in the lossesrelated to the transport of water with highertemperatures. The design temperature for the radiatorsin the base case in this paper is 80/60, and in warmerperiods, this temperature is decreased in order toreduce losses and adapt the supply temperature to theoutside temperature. This affects the efficiencies in apositive way.