Potential for low temperature district heating system : Integrating 4th generation district heating system with existing technology

This project presents a feasibility study and an investigation of the potential for low temperature district heating system in Västerås. The investigation treats integrations possibilities for 4GDH (4th Generation District Heating) in Kungsängens area in Västerås, which is undergoing a large-scale building-up and construction. The study is conducted for the company Mälarenergi AB. The advantages of 4GDH technology are identified and analyzed, where energy effectiveness and economic benefits aspects were concluded. Problems with existing technology and higher cooling demand expectations drive 4GDH to be an interesting and necessary technology in the future. Four Different integration solutions between old and new networks are presented, analyzed and discussed. Quantitative analysis conducted where initial cost for the four technical solutions were estimated and compared. The results show that low temperature district heating could lead to reduction in the initial cost for the network by using PEX instead of steel as pipe material. The results show also that one solution using heat exchanger as exchange stations has the lowest cost between the four solutions. The results show that the cost for the retention flow that is linked with 4GDH stands for 20%-30% of the total cost. The importance of the retention flow pipe is investigated using two physical models in OpenModelica and Excel, where simulations were conducted. It is concluded that it is possible to provide Kungsängen area with low temperature district heating without having the retention flow pipe. Three parameters were identified to be critical which are, geographical placement of the consumers, pattern variation for the heat demand and heat systems installed inside consumer’s buildings. The results show also that it might be critical to have a variate and optimized supply temperature for the area, depending on the demand. The simulations of a fictive area that could present a future heat demand for Kungsängen area shows that a temperature of 55°C is satisfying during winter season where the demand is high and a temperature between 60-65°C must be available during spring/autumn seasons and specially during summer. The variation depends directly on the temperature drop through the supply pipes to the consumers. The temperature drop is directly linked with water velocity inside the pipes. The losses increase during summer nights when the heat demand is low which lead to low water velocities.