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, EstoniaScenario 3 Same amount of heat produced than in scenario 1No storage; connected to large district heating gridScenario 4Solar fraction of 100% for a single family houseSeasonal thermal storage includedScenario 5 Same amount of heat produced than in scenario 4No storage; connected to large district heating gridGeothermal heat productionThe geothermal heat can be used in various ways forroom heating. Using the shallow geothermal heat isonly possible in combination with a heat pump.Therefore, for a large integration into heating grids thedeep geothermal energy is the favoured one.Furthermore in the upper valley of the river Rhein(Oberrheingraben) the geothermal heat can be used fora combined heat and power production because of itshigh temperature. In Germany this gives the possibilityto get a payment for the electricity based on the EEGwhich grows for 3 ct/kWh if the heat is used as well.For a comparison to the solar thermal heat ageothermal power plant in Landau, Germany is used asa reference.This project began in 2004 and at the end of 2007 thepower plant started its first electricity production. Thefirst heat output was planned for 2009.The power plant uses the ORC process (OrganicRankine Cycle) to generate electricity. A drill hole witha depth of 3000 m connects to thermal water with atemperature with up to 160 °C which is cooled downduring electricity production to 70 °C. The whole yearlyenergy output of the power plant is planned to be22.000 MWh electricity and 9.200 MWh heat. One ofthe major benefits of the geothermal heat production isthe base load which is always available. On the otherhand this gives the problem that the heat is alsoavailable in the summer time and needs to be cooleddown in other ways.The calculated emissions of the power plant are0 g CO 2 /kWh because the electricity production has noemissions and for the pumps the own electricity can beused. [6]Currently the power plant runs with a limited output dueto small earthquakes in the area of the drilling hole anddoes not deliver heat until now. Additional geologicalstudies are done right now and a heat output shouldstart after they are finished.Heat production with biomassThe heat production from biomass is technically verysimilar to the fossil fuel powered heating plants.Therefore the integration into existing district heatinggrids is the easiest way compared to the otherrenewable energy sources.The exact technology depends on the used fuels andtherefore the economic calculation is mainly based onthe price development of the biomass.The emissions of such a system are by way ofcalculation zero, because the emitted CO 2 was firstlybound by the biomass during its growing period. If thebiomass is planted in an area which was deforested forthat, the emissions are not zero any more. The formerforest was a CO 2 sink which does not exist anymoreand should be included in the calculation. Furthermorethe transport and processing of the biomass should beincluded. [19]Fossil fuels for comparisonIn our days the district heating grid in Mannheim is fedwith heat from a fossil fuel fired CHP plant. The heatprices from that system are much lower than therenewable heat. Looking into the future it mainlydepends on the price development of CO 2 emissionsand the coal price. [8]The emissions of such a system are very high, even ifthe used heat is more or less waste heat. To reducethose, a CCS technology can be implemented in thefuture.RESULTSThe results of the simulation are shown in Tab. 4 andFig. 2 and 3.In conclusion the heat price is lower if the collector areaincreases (economy-of-scale). Furthermore the use ofa district heating grid instead of a thermal storagelowers the heat cost extremely.For scenario 1 it is necessary to install a gross area of3080 m² solar thermal collectors. 1076 MWh heat canbe produced in combination with a 2820 m³ hot waterstorage. The heating costs calculated with the givenframework conditions are 11,2 ct/kWh. To operate thecollector area, pumps are needed which consumeelectricity. The emissions of that electricity are, basedon the produced heat, 7,9 g CO 2 /kWh.In scenario 2, 1916 m² solar thermal collectors need tobe installed. Combined with a hot water buffer storagewith a volume of 175 m³, 494 MWh of heat can beproduced. The financial calculation over 20 years lead136