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Title Efficiency assessment of conventional district energy system and alternative CO2 based solution
Author Madsen, Christian Vang
Jacobsen, Christian Nørr
Supervisor Elmegaard, Brian (Thermal Energy Systems, Department of Mechanical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Ommen, Torben Schmidt (Thermal Energy Systems, Department of Mechanical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Hvid, Jørgen
Capion, Karsten (Rambøll Danmark)
Institution Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
Thesis level Master's thesis
Year 2011
Abstract This project aims at comparing the efficiency of the existing Danish district heating system with a proposed new energy system, constructed around the idea of creating a network of CO2 throughout the city, which can be used as a refrigerant to supply any thermal energy service within common temperature levels of heating and cooling. The potential advantages of the propose system includes easy integration of low temperature sources, the ability to deliver all temperature services in a single system and in addition create a synergy effect, where consumers of one thermal energy service would become producers of the other, thereby decreasing the systems overall need for energy input. Through the project the two energy systems are initially modeled on a unit scale, the results of which is then utilized in the development of a comprehensive system model containing a simplified version of both energy systems. As a basis for comparison, a case is constructed containing four different consumer types, each with a set of four different energy service demands that are then combined with a projected electricity demand to form the final case. The amount of primary fuel input of both systems, used to cover demand throughout the year is calculated using the simulation model, and finally used in an efficiency comparison. The results indicate that the existing system uses 8 % less energy than the proposed system when considering the energy system and demand patterns of today. When considering a 2050 scenario, the proposed system still cannot match the efficiency of the existing system, using 3 % additional primary fuel, mainly due to the extensive implementation of large scale heat pumps in the H2O system, enabling the easy integration of excess electricity production from wind turbines into the district heating network. To determine the impact on the efficiency of the two systems, resulting from a variety of potential changes in the energy system and consumption pattern, a range of sensitivity analysis are carried out. The most interesting results indicate that if more than 35 % of the electricity is produced without heat production then the CO2 system will be more energy efficient. In addition it is determined that the building distribution in the simulated area has a pronounced effect on the results, mainly in connection to the building type’s contribution to the mentioned synergy effect. Finally a qualitative assessment of the investment and maintenance costs are conducted, which indicates that the proposed system is clearly more expensive in operation than the existing water based solution. The final recommendations of this report is, that the CO2 system could potentially play a central role in the future energy system if the area of implementation only includes limited CHP production and the building distribution is varied. However before commercial operation can be reached, a number of issues related to safety, control and economics must be further investigated.
Imprint DTU Mechanical Engineering
Pages 198
Series MEK-TES-EP-2011-14
Original PDF prod21323243759457_MasterThesis_Collected_Final_1.pdf (9.20 MB)
Admin Creation date: 2011-12-14    Update date: 2011-12-14    Source: dtu    ID: 314446    Original MXD