12th International Symposium on District Heating and Cooling

electricity production sector does not necessarily tolead to reduction of GECO2 [12]. But the marginalelectricity concept still has significance for futuremeasurement of and planning for future limitations ofCO 2 emissions and the future trading system.Table III. – Net emissions of CO 2 [10].FuelEmissions kg/MWhfuelOil 280Coal 330Waste 100Biomass 0Electricity 950Natural gas 2303.3 Description of chosen scenariosNine different scenarios have been analysedconsidering the possible future cases (Table IV), withspecial attention to economic and environmentalaspects.The existing district heating system (scenario 1) andthe system with three new CHP plants that are plannedto bee built according to the interviews and documents(scenario 4) have been analysed. Since the baseproductions in the networks differ, the differencesbetween the production‘s costs in different parts of thesystem are notable. Because of that, in both cases(scenarios 1 and 4) the influences of a betterconnectivity between networks have been studied(scenarios 2 and 5).Table IV. – List of the chosen scenarios.Sc.Plantsin thedistrictheatingsystemConnectivityElectricitypriceTGC1 existing existing Nordpool exist2 existing one Nordpool existnetwork 13 existing existing EU exist4 + new existing Nordpool existCHPP5 + new one network Nordpool existCHPP6 BCHP one network Nordpool exist7 BCHP one network EU exist8 BCHP one network EU do notexist9 NGCHP one network EU -1) Interconnections between the south-central and thenorth-west networks have been introduced as well asinterconnections between south-central and south-eastnetworks. Capacities for existing pipes have beenincreased.The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, Estonia290Since electricity generation will probably be the primaryproduction in all district heating companies in thefuture, when the Swedish electricity price becomes ashigh as the typical European price, in scenarios 6-9 ourresearch focuses on the cogeneration potential inStockholm's district heating system. Scenario 1 hasbeen used as a reference scenario for scenario 6.Scenario 3, where the influences of a higher electricityprice on the system with the existing plants have beenanalysed, has been used as a reference scenario forscenarios 7–9. Scenarios 6-9 are analysed as possiblefuture cases that may exist more than 10 years fromtoday. Because of that, all plants in the scenarios arenew so the investment costs for all plants areconsidered. While in the scenarios 6, 7 and 8 thesystem consists of 31 CHP plants fuelled by solidbiomass (BCHP), there are a total of 46 CHP plantsfuelled by natural gas (NGCHP) in scenario 9. Inscenario 9 it is assumed that the natural gas networkexists along the Swedish east cost.The characteristics of the CHP plants that have beenintegrated in the model of the district heating system inscenarios 4–9 are presented in Table V [13].Table V. – The characteristics of the new integrated CHPplants in scenarios 4–9 [13].Sc.4–5Technical characteristicsFuelElectricaloutputMWe %FuelefficiencyΑ*biomass 30 110 0.45waste 20 91 0.32biomass 80 110 0.466–8 biomass 80 113 0.519 natural gas 150 89 1.414–5Economic characteristicsProcessplant costOperating and maintenance€/KWe % of PPC €/MWh fuel2 745 1.5 2.455 440 3 9.312 110 1.5 2.456–8 2 110 1.5 2.459 715 2.5 0.9* electrical/thermal output3.4 Previous studiesTwo studies regarding Stockholm´s district heatingsystem were done in the years 2005 [10] and 2006[14], and the results showed that benefits for betterconnectivity between some parts of the system existed.