Fernkälteversorgung zur Vermeidung von Grundwassererwärmungen und Nutzungskonflikten am Beispiel der Stadt Linz - Bewertung auf Basis ÖWAV-Regelblatt 207 und qualitativer Nutzwertanalyse

Groundwater investigations in Linz have shown, that the temperature in the groundwater reservoir has increased significantly compared to the temperature of the environment. To investigate whether the existing groundwater facilities for cooling have a quantifiable impact on groundwater temperatures all given permissions regarding groundwater usage for cooling premises were analyzed in detail. Therefore data on the yearly amount and type of groundwater usage were collected and sorted for further analyses. Based on these data the length and the width of the temperature flags in the groundwater reservoir were calculated with the thermal formula of Ingerle (1988), modified by Rauch (1992) and corresponding to the ÖVAW technical rule 207. The temperature flags of every groundwater user with cooling purposes were visualized with the software ARCMAP 10.1 and compared with real data from field measurements. Furthermore an analyses of uncertainty for the length of the temperature flags was involved in the study. With this method the areas where a thermic impact to the groundwater reservoir is of a high likelihood because of existing groundwater usage for cooling purposes were identified. Based on this in a next step different alternatives for district cooling were developed involving both central (covering all existing groundwater users) and semi central (covering only parts of existing users) solutions. To compare and evaluate the difference an efficiency analysis was undertaken. In this article the calculation and results of the thermal flag analysis of all relevant groundwater users are presented. Two of the seven alternatives for district cooling are then introduced more detailed. Further the efficiency analysis of the different alternatives is described using economical, ecological and social criteria.