Impact of Different Design Guidelines on the Total Distribution Costs of 4th Generation District Heating Networks.

Abstract When it comes to the design of new district heating networks, different design guidelines of different countries and pipe manufactures occur. All guidelines are aiming to restrict the specific pressure drop per meter pipe length to avoid uneconomic network operation. This paper evaluates the impact of different design guidelines from Sweden, Germany and Austria, as well as pipe manufacture recommendations on the total distribution costs. The analysis was conducted for a 4^th generation district heating network for a new housing development (3 km trench length). The resulting district heating networks were compared in terms of total distribution costs. The results state that designing small networks at maximum heat load by allowing high specific pressure drops of 300 Pa/m shows the most economic results in terms of capital costs and variable costs. Compared to 70 to 100 Pa/m recommendations, 6 – 8 % investment costs for transportation pipes can be saved designing the network with 300 Pa/m pressure drops of short duration. Regarding distribution heat loss costs, the smaller the average diameter of the network the lower the heat distribution losses. Optimal network design leads to a 7 % heat loss reduction for the whole network. Furthermore, the paper compares total costs of the networks designed for two different design temperatures: 70°C supply with 40 °C return and 40°C supply temperature with 25 °C return. In terms of total distribution costs, both networks are very similar, which shows that ultra-low temperature networks have no economic disadvantages compared to state of the art 70°C networks, as often believed. [ABSTRACT FROM AUTHOR]