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, EstoniaTable 5: parameters for economical operationScenario 1 Scenario 3Heat costs 3,5 ct/kWh 3,4 ct/kWhIRR 5 % 5 %Capital cost 70 % 90 %Financial support 40 % 30 %Heat pricedevelopment8 % p.a. 8 % p.a.Fig 4: influence on the heat costs of different factorsFigure 4 shows the influence of the different factors, ifthe others stay the same. But it also shows, that bychanging just one aspect, a reduction of the heat costto 3,5 ct/kWh is only possible with lowering the capitalcosts by 50% of the scenario without a thermal storage[scenario 3].Therefore a combination of different factors was done.The capital costs are also influenced by the financialsupport und were calculated separately.In order to reduce the heat costs down to about3,5 ct/kWh in scenario 1, a reduction of the capital costby 40% combined with financial support of 50% isnecessary, if the heat price will rise with 8% per year.This is higher than shown in figure 4 and is based on ahigh price assumption as reported in [10].If a lower IRR is assumed (5 %), the capital costs haveto go down to 70 % and a financial support of 40% ofthe investment is necessary.For scenario 3, a rise of the heat price and the lowerIRR (5 %) just need a reduction of capital costs of 10 %to achieve heat costs of 3,4 ct/kWh. In this case theassumed financial support of 30% stays the same. Thisshows that an economical use of solar thermal energywithin district heating could be achieved. The financialsupport of 30% can be possible based on a KfWprogram, the capital costs of 90% of the baseinvestment is possible within a feasibility study and the5% IRR is an average figure for building loans.The high requirements to make the solar heat profitableshow, that this technology is not advisable if otherrenewable energy sources are available. Furthermorefor the technical integration a low temperature heatinggrid is necessary.For the near future it might get more interesting to lookon the biomass and geothermal heat, particular if theheat is needed in a region where high temperatures inthe depth could be exploited or cheap biomass sourcesare available. Further research in the solar collectortechnology is needed to lower the capital costs andequally within the thermal storage technology, as itmight get interesting in the future to include those evenin district heating grids with fossil fuels as heat sourceto cover peaks in the demand and transfer a surplusheat production from the summer into the winterseason.NOMENCLATUREW [J]∆Q [J]∆p [Pa]∆T [K]cp [J/(kg*K)]ρ [kg/m³]ηREFERENCESwork of pumpheat flowpressure difference (flow / return)temperature difference (flow / return)heat capacitydensitypump efficiency[1] Begerow, P.; Integration von erneuerbarenEnergien in Fernwärmenetze – Eine technischeund wirtschaftliche Analyse aus Sicht einesFernwärmeversorgers, Diplomarbeit an derUniversität Flensburg, MVV Energie AG,Mannheim; 2010.[2] Bodmann, M.; Mangold, D.; Nußbicker, J.; Raab,S.; Schenke, A.; Schmidt, T.: Solar unterstützeNahwärmeversorgung und Langzeit-Wärmespeicher; Forschungsbericht zum BMWAVorhaben; Universität Stuttgart; 2005138