At the Fraunhofer Institute UMSICHT a nonlinear model has been developed facilitating the dynamic optimisation of combined heat and power production systems. The strategy called “dynamic supply temperature optimisation” is a very promising approach to use the DH-network itself as a large heat storage causing no additional investment cost. The pipeline system of a district heating system has a huge potential for the storage of energy. Especially for the application of renewable energies the optimal use of these storage capabilities will increase the overall efficiency. In particular for CHP systems with fixed heat and power coupling (back pressure turbines), this approach could enable a reduction of operating heating plants and the displacement of expensive peak power plants. It will reduce electrical power peaks and enables a better utilisation of tariffs. The supply temperature optimisation aims at finding the operating point at which the power requirements (heat and electrical energy) of the consumers can be covered with minimum operating cost. In order to determine the optimal values of the variables, the system performance as well as the technical and contractual restrictions have been considered in the mathematical optimisation model. These are e.g. the energy purchase contracts, the characteristics of the energy conversion plants, the power requirement of the consumers and the dynamic behaviour of the DH network. These connections have been described by equations and inequations, in which optimisation variables and model coefficients are linked together. On the basis of configuration and calculation data an optimisation model has been formulated under application of modern optimisation procedures. As results of these optimisation model the optimal courses of the supply temperatures of the individual suppliers, the electrical and thermal input powers as well as the storage powers etc. can be received.
Report No. 1 Institution: Fraunhofer Institut für Umwelt-, Sicherheits- und Energietechnik UMSICHT Address: Osterfelder Straße 3; D-46047 Oberhausen; Germany 11/02