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, EstoniaAll other parameters are the same like the old CHP 2.Main difference is the smaller range of performance.The remaining energy system left unchanged exceptfor the CHP-refund expiring the next year.The optimal operation mode considering the old(case III) and the new (case IV) parameters of theCHP 2 are determined. Case III serves as a referencecase. The calculated operation costs per week areshown in Fig. 4 for both cases.Total cost / 10 3 €35302520151050Operating costs per weekJ F M A M J A S O N DMonthOld CHP 2 (case III) New CHP 2 (case IV)Fig. 4 Operation costs per week (case III and case IV)In Fig. 4 it can be seen that the operation costs forcase IV are below the operation costs for case III inevery week, especial in the summer months becausethe smaller size of the new CHP 2 suits better to theheat demand. Altogether total operating costsamounting to about 27770 € (3.2 % of total costs) canbe saved (Tab.5). Main reasons are the huge fuelsavings which settle easily the decreasing proceedsthrough electricity sales. By given investment cost it isvery simple to check if the renewal of the old CHP 2 iseconomic reasonable.Tab. 5 Comparison annual operating costs and proceeds(case III and case IV)Annual operationcosts andproceeds / 10 3 €Old CHP 2(case III)New CHP 2(case IV)Costs fuel 1323.87 1208.79Proceedselectricitycontracts462.87 367.12Start up costs 7.72 1.20Costs networkaccess1.92 0.00Total costs 870.64 842.87As example the heat balance curve on one summerweek (168 hourly time steps) is shown in Fig. 5. Such acurve helps to determine the recommended operationmode.The red line marks the given heat demand which issatisfied at all time steps. The small-sized CHP 2operates continuous. When the heat demand is higherthan the output of the CHP 2 the heat plant is switchedon or the heat storage is discharged mostly. Chargingthe heat storage takes place in low demand times andby switching on one of the others CHPs (CHP 1 orCHP 3) for up to four hours. Using the CHP is moreeconomic than using the heat plant but start up costsand the size of the heat storage restrict the operation ofa second CHP.heat flow / kW18001600140012001000800600400heatplantHeatbalanceheat demandcharge ofstorageby CHP200CHP productiondischarge of storage00 12 24 36 48 60 72 84 96 108 120 132 144 156 168time / hCHP production storage load heat plant storage unload heat demandFig. 5 heat balance curve on one summer weekFinally it can be summarized that first experiences andcalculations show, how the FreeOpt allows in an easyand quick way to check beforehand if certain systemconfigurations are useful or contra productive.PROGRAM STEFANApplication fieldThe network optimization is a special case of theresearch-main focus „optimization of the technicalstructure of district heating systems―of the 5th energyresearch program of the German Federal Government.Due to the relatively high net costs of district heatingsystems it is necessary (beside the application ofactual piping systems) to optimize the nets concerningtheir design parameters, in particular the pipe diameterand the pipe routing.Therefore the software tool ―STEFaN‖ has beencreated for the combined pipeline routes and diameteroptimization. This Windows program for the support ofthe application of the district heating has interfaces togeographical information systems (GIS) and iscomplementary with these. Its application is possible in3 planning phases:321