Development of Smart Thermal Grids

Approximately half of buildings' energy demand is related to heating and cooling. At the same time, the amount of industrial waste heat available in Europe is estimated to be in the same order of magnitude as the total heating demand. District heating (DH) is a significant technology in that it enables efficient and economical utilization of energy sources that would otherwise be wasted to cover buildings' heating demands. By utilizing DH for heating purposes instead of electricity wherever possible, DH will enable reducing the load from the electric grid. DH will hence play an important role in the future fossil-free energy systems. However, today's DH system applies a high temperature level for the distribution of heat, which leads to high heat losses. In order to reduce the distribution losses, and to be able to utilize waste heat and renewable heat sources in an efficient manner, it is necessary to shift to lower distribution temperatures. In the project Development of Smart Thermal Grids (DSTG), a tool for modelling a local thermal grid for a building area has been developed. The tool allows the user to model and simulate a local thermal grid in detail, and to dimension and design the system based on hourly data. The tool has been applied to study the benefits and potential drawbacks of low-temperature heat distribution; as well as to study the utilization of waste heat from sources often present in urban areas, such as food retail stores and data centres, in the local thermal grid. The simulation results demonstrate that the heat losses in the network can be reduced by up to one third by reducing the distribution temperatures. Pressure losses will increase, which will increase the demand for pump work, but this increase is minimal compared to the savings in heat losses. Lower distribution temperatures reduce also the demand for peak heating devices, often running on fossil fuels, hence reducing the environmental impact of the DH system. The environmental impact can be further reduced considerably by utilization of local waste heat sources. To fully realize the potential of local thermal grids with waste heat utilization, thermal storage and efficient control strategies are needed. These topics will be studied further in two spin-off projects: LTTG+ and RockStore.

Abstract The underlying idea of the project is the evaluation and development of smart thermal grid solutions for building complexes and district centre. A smart thermal grid will include low-temperature heat distribution and, if needed, medium temperature cooling distribution; and the heating and cooling demands will be covered by local waste heat and renewable heat production, in combination with innovative thermal storage solutions. The smart thermal grid will be operated through an energy plant, which will deliver heating and cooling to all the buildings and which also coordinates possible exchanges with the district heating network. The evaluation of the components in the smart thermal grid will be based on life cycle cost analysis. Upon successful implementation, a smart thermal grid will be: flexible in adapting to changing circumstances in supply and demand in the short, medium and long term; intelligent in terms of planning and operation; efficient with regards to production and distribution of heat and cool; cost-effective so that operation is affordable from a societal perspective; and a secure energy supply at a local level. The overall project objective is to develop a tool for evaluation of energetic, economic and environmental benefits in utilizing a local smart thermal grid for a building complex or district centre. The project partners are the local district heating provider, Statkraft Varme, and the municipality of Trondheim.