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, Estoniafossil or other non-renewable or polluting energysources in the energy conversion system.The CO 2 production coefficient, K, shall include all CO 2 -emissions associated with the primary energy used.Furthermore, equivalent emissions of other greenhousegases, e.g., methane, may be included [4].According to Directive 2002/91/EC, indicators on theenergy performance of buildings shall include theconsumption of primary energy and the CO 2 emissionsresulting from the buildings energy usage. Factors forprimary energy consumption and CO 2 emissions havebeen calculated for various energy chains producingelectricity, and values for these factors are given inAnnex E of the standard EN15603 on the energyperformance of buildings. An overview of these factorsis given in Table 1.Table 1: Energy performance indicators for varioussources of electricity [4]Source ofelectricityHydraulicpowerNuclearpowerPrimary energy factors f p[MWh primary energy /MWh delivered energy]Non-RenewableTotal0.50 1.10 72.80 2.80 16CO 2productioncoeff. K[Kg/MWh]Coal power 4.05 4.05 1340ElectricitymixUCPTE3.14 3.31 617As seen in the standard EN15603:2008 [4] andTable 1, no indicators are given for geothermal power.The directive is under reconstruction and a recast hasbeen released, as mentioned before. Also, the tabledoes not give factors for sources of thermal energyused by buildings for space heating. Thus, there isclearly a need to calculate these factors for energychains that involve geothermal energy, since theyproduce both electricity and heat which is delivered tobuildings within the European Union and in countriesfollowing EU legislation.GEOTHERMAL HEAT AND POWER PRODUCTIONAT HELLISHEIDI CHP PLANTHellisheidi geothermal CHP plant is situated at theHengill geothermal area close to Reykjavik, the capitalof Iceland. A 90 MW electricity production started in2006 after several years of construction and research.In 2007, a low pressure turbine was added, increasingthe power generation to 120 MW. A year later, another90 MW were added, resulting in a power generationcapacity of about 210 MW (213 MW in February 2009).Further developments of the power plant includeadding heat production in 2010 for district heating andalso increasing the power production if possible.Estimated production capacity for the completedHellisheidi Plant is 300 MW electricity and 400 MWthermal energy [5].The plant today is a double flash power plant with highandlow-pressure turbines and separators as seen inFigure 1. The heat production facilities are currentlyunder construction with a planned 133 MW thermalcapacity at the end of year 2010. The technicalcomplexity is moderate and the plant makes a goodbasis for a LCA study to evaluate the primary energyefficiency and CO 2 emission of this type of geothermalpower plant. Since it is fairly newly constructed, accessto detailed background data for the inventory modellingis possible, making the study more reliable andaccurate. Environmental assessment for theproduction is available as well as measurements ofvarious environmental impacts of the power plant,providing data for the impact assessment of the LCAstudy.In this study, a steady production of 213,6 MWelectricity and 121 MW heat is used as a basis for theLCA model. The reason for this choice is that thenewest inventory data on the construction phase andmass extraction are built on these productioncapacities, and that the base thermal load is estimatedto be 121 MW and not the full capacity of 133 MW.PRIMARY ENERGY OF VARIOUS ENERGYSOURCESThere is a matter of inconsistency in primary energycalculations of various energy sources as manydifferent methods are in use and accepted by differentenergy authorities [6]. As an example, the primaryenergy factors for power produced from renewableenergy sources such as hydro power, wind energy andsolar energy are sometimes calculated by assumingthat the primary energy factor for the energyconversion system is one, which is the same asassuming that the energy conversion process is 100%efficient. The reason for this assumption is that theprimary energy is defined as the first usable stage ofthe energy flow, which in the case of wind, solar andhydro is the electricity itself produced from theseprimary sources [7]. For electricity production fromheat sources, the first usable stage of the energystream is defined as the steam input into the turbine,according to an energy statistics manual from the<strong>International</strong> Energy Agency (IEA) [8]. The methods185