Dynamic modelling of local low-temperature heating grids: A case study for Norway

Abstract

Today's district heating (DH) networks in Norway are 2nd and 3rd generation systems, with supply temperatures ranging from 80-120 • C. In new developments, it is desirable to shift to 4th generation, low-temperature district heating (LTHD) in order to reduce the heat losses and enable better utilization of renewable and waste heat sources. A local LTDH grid for a new development planned in Trondheim, Norway, has been modelled in the dynamic simulation program Dymola in order to study the effect of lowered supply temperatures to heat losses and circulation pump energy use. Different cases with supply temperatures ranging from 55 to 95 • C, lowered return temperature as well as peak shaving were analyzed. Real DH use data for buildings in Trondheim were employed. The environmental impact in terms of the total produced CO 2 equivalent emissions was estimated for each case, assuming a heat production mix corresponding to that of the local DH provider. The results showed that by lowering the supply temperature to 55 • C, the heat losses could be reduced by one third. The total pump energy increased significantly with reduced supply temperature, however the pump energy was generally an order of magnitude lower than the heat losses.

Local Heating Networks with Waste Heat Utilization: Low or Medium Temperature Supply?

“…The pipe diameters were selected assuming a maximum pressure drop of 150 Pa/m and using a relationship between maximum mass flow rateṁ max and inner diameter D i derived in [26]:…”

Life Cycle Assessment of Different Low-Temperature District Heating Development Scenarios: A Case Study of Municipality in Latvia

“…Another case study on DH in Sweden found that decrease of temperature from 80/40 °C to 65/30 °C and 50/20 °C increase the electricity consumption for pumps in DH in the case of reduced supply and return temperature. According to Kauko et al [39], such increase of electricity demand for recirculation flow due to decrease of temperatures in DH will be very low. Moreover, in case study the difference between supply and return temperatures did not change, thus the study considers that the electricity consumption for pumps will not change.…”

Future district heating systems and technologies: On the role of smart energy systems and 4th generation district heating

“…This perspective paper starts with four papers regarding the transformation of current systems into future 4 th generation district heating solutions with a focus on the district heating grid. These papers add to previous Smart Energy Systems and 4 th Generation District Heating research [4,16,[25][26][27][28][17][18][19][20][21][22][23][24] by having a focus on transformation processes into low-temperature district heating both in the north and in the south.…”