Small low-temperature district heating network development prospects

One main obstacle to the implementation of low-temperature district heating is the existing infrastructure along with consumer heating devices that were usually designed for higher operating temperatures. If a DHN is installed for a new urban area, these obstacles can be avoided. This study presents an analysis of alternative heat supply scenarios for the newly developing city subdistrict of Kopli (Tallinn, Estonia). The following scenarios were analysed from economic and environmental aspects: scenario A-connection to the existing DHN (supply/return temperatures 95 °C/55 °C, gas-fired boiler house); scenario B-small local DHN (80 °C/40 °C, small gas-fired boiler house); scenario C-small local LTDHN (60 °C/35 °C, small gas-fired boiler house, integrated large-scale heat pump using seawater as heat source). The results of the study have shown that the primary energy consumption per 1 MWh of heat consumed is 1.33 MWh for scenario A, 1.15 MWh for scenario B, and 0.71 MWh for scenario C. To achieve IRR = 7%, a 4 year discounted payback period was calculated for scenario B, with the NPV of 1.000.000 EUR after the period of 10 years. For scenario C, the payback period is more than 5 years, and the NPV is 2.600.000 EUR after 10 years.