Sammendrag
Low-temperature district heating (LTDH) grids extend the options for using local low-grade waste-heat sources. Such sources may exhibit a high variability in available heat and temperature level. This is the case for a local LTDH under development in Trondheim, Norway, which will receive waste heat from an ice-skating rink with large daily and seasonal variations. The LTDH will be connected to the city's primary DH grid for covering the remaining heat demand. Demand-side management (DSM) can be used to shift or curtail flexible heat loads of buildings connected to the LTDH grid and hence for saving peak-heating costs by means of the heat withdrawal from the primary DH grid. We compare operations with and without DSM for the LTDH with aggregated demand profiles for the planned residential and commercial buildings in the area and consider yearly savings in heating costs through a seasonal representative-days approach. For the DSM, we present a Modelica-based optimal-control scheme which connects the least-cost heat-supply problem of the LTDH operator with the buildings' optimal response through a price signal generated by the operator. We quantify results on the case study and present sensitivity analyses on demand and peak-heating cost volatility.