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, EstoniaThe value of 5.33 for fp is obtained in the two lattercases, where the waste heat is either reinjected backinto the reservoir or used for heating of DH water. Inthose cases, the primary energy content of the wastestream can be subtracted from the primary energycontent of the geothermal fluid used for the electricityproduction, resulting in lower fp values. The share ofnon-renewable primary energy sources such as oil andgas used in the construction phase or in themanufacturing of various power plant components, onlyaccount for about 0.01 of the total fp value in all cases.The factor K for the CO 2 emissions is the same for allthree cases of electricity production as reinjection andutilization of waste stream does not have significanteffects on the total emissions due to the power forproduction. The origins of the CO 2 emissions can beseen in Figure 4. The largest contributor to the CO 2emission from the electricity generation over 30 yearsof production is the geothermal fluid, responsible 88%of the CO 2 emissions per kWh of electricity production.Table 2 – Results for the primary energy factor and CO 2 emission factor for electricity based on geothermal energySource of electricityPrimary energy factors f p[MWh primary energy / MWh producedenergy]Non-RenewableTotalCO 2 productioncoeff. K[Kg/MWh]Electricity from Hellisheidi geothermal powerplantElectricity from Hellisheidi geothermal powerplant, with reinjection0.01 6.33 290.01 5.33 29Electricity from Hellisheidi CHP plant 0.01 5.33 29A small share of 8% originates from the drilling ofgeothermal wells while the construction of the powerplant, along with the manufacturing of its maincomponents, is responsible for 4% of the CO 2emissions.GWP 100a for Electricity Productionin kg CO2 eq4%8%0.5%87.5%Geothermal fluid(87.5%)Power plant andcomponents (4%)Geothermal welldrilling (8%)Collection lines(0.5%)value reduces to 0.69. In both cases, the share ofprimary energy from non-renewable energy sources isless than 0.01. In both cases, the CO 2 productioncoefficient is 0.98 kg CO 2 equivalents per producedMWh.The origins of the CO 2 emission from the heatgeneration process can be seen in Figure 4. Thelargest contributor to the total emissions is the drillingof the geothermal production wells that were needed tosustain the electricity production while the heatproduction is at maximum load of 133 MWth. Themanufacturing of the district heating pipeline from theproduction area to the rural area of Reykjavík citycontributes to 15% of the total emission resulted fromthe heat generation process.Figure 3 – Origins of CO 2 emissions from the differentprocesses of the power generationEnergy Performance Indicators for ThermalProductionThe energy performance indicators for the productionof heat for district heating are given in Table 3. Twocases are presented for the heat production; heatproduction process with or without the effects ofreinjection of waste geothermal fluid. The highest valuefor f p is obtained in the case where reinjection is nottaken into account, with the value of 1.78 MWh primaryenergy/MWh produced energy. With reinjection, theFigure 4 – Origins of CO 2 emissions from the differentprocesses of the heat generation190