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, EstoniaSLIMNET: AN INNOVATIVE INTEGRAL APPROACH FOR IMPROVINGEFFICIENSIES OF DISTRICT HEATING NETWORKSM. W. P. van LierStadsverwarming Purmerend B.V., the Netherlandsm.v.lier@svpbv.nlABSTRACTThis paper describes the innovative integral approachimproving district heating network efficiency, SlimNet.SlimNet consists of five phases which lead to annualenergy savings of about 227.000 GJ and almost 37.000ton CO 2 savings for the city of Purmerend in 2015.INTRODUCTIONCompany situationIn 2007 the new company StadsverwarmingPurmerend B.V. (SVP) took over the responsibilities ofthe district heating network from the municipality inPurmerend, the Netherlands. With 25.000 customersthe grid is the fourth largest grid of the Netherlands.District heating Purmerend started in 1980. Thenetwork expanded organically following the cityexpansions. While daily operations were outsourced toexternal and changing partners, the final responsibilitystayed with the municipality.A comprehensive business analysis performed by thenew management in 2008 showed severe problems. Inthe present state the company would remainstructurally loss giving, (future) heat delivery was notensured, and sustainability and customer satisfactionwere below benchmark standards. Fall 2009 a newbusiness plan was presented that sets course for afuture proof company, based on sustainable, costeffectiveand 80% renewable heat. On the technicalside this is achieved by two major project programs, a.improving network efficiency, SlimNet, and b.incorporation of sustainable energy sources, theEnergy transition. The company mission is to becomethe most sustainable district heating company of theNetherlands.installations. Specific to the secondary network are thepost-insulated steel distribution pipes and connectionsto customer installations hanging in narrow crawlspaces under blocks of buildings.In the distribution process no heat exchangers areused except from the production of hot tapping water inthe houses.Hydraulics are controlled by decentralized pressurizingvalves, differential pressure valves and pumpscompensating for hydraulic deficiencies.The supply temperature from production is directlyrelated to the ambient temperature (i.g. 95 C atT a =-10 C and 75 C when T a =15 C). The maximumsupply pressure to the primary network is 6,8 bars andto the secondary network 4,5 bars.NETWORK CONDITIONPart of the business analysis was an extensivetechnical research program covering all technicalaspects of the grid and finally entire district heatingchain. The main conclusions were:1. The network characteristic had becomeuncontrollable: Network builds out has occurredwithout a master plan. Effectively SVP had nocontrol on the characteristics of customerinstallations. Furthermore, hydraulic problems inthe grid had been masked with decentralizedpumps and control systems.2. Heat production capacity was critical, reaching acritical limit under the conditions of the winter of2008. There was certainly no spare capacity tofacilitate the planned expansion of the grid andthus the heat demand as shown in Fig 1.Network descriptionThe 520 km district heating network is fed by a CHP(CCGT) plant of 65 MWth and seven natural gas firedauxiliary boilers with a total power of 131 MWth. Duringthe last 6 years 64% of the total heat production camefrom the CHP plant. The heat sources are operated bya third party.The production units feed the heat to the network viabuffering tanks to the primary network. The heat is thendirectly transported through substations and asecondary network to the 25.000 customerFig. 1 Required heat production53