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, EstoniaEFFECTIVE WIDTH – THE RELATIVE DEMANDFOR DISTRICT HEATING PIPE LENGTHS IN CITY AREASUrban Persson 1 , Sven Werner 11 School of Business and EngineeringHalmstad University, PO Box 823, SE-30118 Halmstad, SwedenABSTRACTOne key concept when assessing network investmentcost levels for district heating systems is the linear heatdensity. In contrast to a traditional way of expressingthis quantity entirely on the basis of empirical data, arecently developed analytical approach has made itpossible to estimate linear heat densities on the basisof demographic data categories. A vital complementingquantity in this analytical approach is the concept ofeffective width.Effective width describes the relationship between agiven land area and the length of the district heatingpipe network within this area. When modellingdistribution capital cost levels by use of land areavalues for plot ratio calculations, there is a potentialbias of overestimating distribution capital cost levels inlow dense park city areas (e < 0.3).Since these areas often include land area sectionswithout any housing, avoiding overestimations ofnetwork investment costs demand some kind ofcorrective mechanism. By use of calculated effectivewidth values, a compensating effect at low plot ratiolevels is achieved, and, hence, renders loweranticipated distribution capital cost levels in low densepark city areas.INTRODUCTIONOne key concept when estimating investment costlevels for district heating systems is the linear heatdensity, i.e. the quota of annually sold heat in a districtheating scheme and the trench length of the pipingsystem in this scheme (Q s /L) [1]. In contrast to atraditional way of expressing this quantity entirely onthe basis of empirical data, a recently developedanalytical approach has made it possible to estimatelinear heat density on the basis of demographic datacategories [2]. A vital complementing quantity in thisanalytical approach is the concept of effective width.BACKGROUNDEffective width is a stand alone concept within districtheating theory, describing the relationship between agiven land area, A L , and the length of the districtheating pipe network, L, within this area. Hence, theeffective width becomes the width of an analogousrectangle with the trench length as the length andwhere the rectangle area is equal to the given landarea.The concept was introduced by Werner [3] and hasbeen further elaborated recently in model estimationsof distribution capital cost reactions to decreased heatdemands in four north European countries [2].Essential for calculations of anticipated investment costlevels for future district heating systems, the effectivewidth constitutes an important model parameterindicating levels of network extensions in given landareas.Since the concept of effective width itself is rather new,with no previous analytical or statistical use, data oneffective widths are in principal non attainable withinnational statistical sources. Effective width might beregarded as an innovative model quantity with noprevious representation in the field of district heatingresearch.AIMThe aim of this paper is to describe the concept ofeffective width and outline the basic properties of thisquantity. On the basis of, although sparse, empiricalobservations, preliminary statements concerning theproperties of effective width are made. The aim isfurther to enlighten the theoretical environment in whicheffective width contributes when applying demographicquantities for estimations of district heating networkinvestment costs.LIMITATIONSDue to a limited amount of empirical data, in principalless than 100 observations, the specific result valuesand relationships accounted for in this paper must beconsidered as preliminary. Although thorough in theory,the concept of effective width needs to be supportedfurther by extended empirical data gathering. In orderto be able to produce solid and reliable estimations ofeffective width values in different kinds of city areas,such information is considered vital for future use of theconcept.128