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SUMMARYThe possibility of improvement of the energy performance and economic feasibility of a CHP plant by the use of hot water storage tank is analysed in the paper. An energy balance of a system consisting of a CHP module, a peak boiler and a heat storage unit has been built and the storage efficiency has been defined. Heat transfer in storage tanks and its influence on the energy balance is discussed. A numerical model of heat transfer in the storage tank is presented. The thermodynamic and economic optimum of the tank volume for a sample co-generation plant has been found. It has been eventually proved that the installation of a heat storage unit provides reduction of fuel consumption in the system.

Aspects of using the small‐scale combined heat and power modules in buildings is presented in this paper. At first the problems of energy demand analysis, which is the key point of a co‐generation plant sizing procedure, are discused. Then the demonstration project of a small‐scale co‐generation plant is presented. The plant is fuelled with natural gas, and it supplies energy to a group of three different buildings. Basing on this case, the problems of optimal sizing of a small‐scale CHP plant for a building energy supply system are presented and discussed. Calculation procedures are shown together with the results of sample analysis. The factors influencing the final configuration of the system are indicated.

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Identification of thermal resistance of the gas-gap between the ingot and mould during continuous casting of metals is the subject of the present article. Analysed parameter estimation problem of the steady-state heat conduction belongs to the group of inverse problems. The present work shows the possibility of applying the least square adjustment method with a priori data for identification of thermal resistance as well as the interphase location and the temperature field within the ingot and mould. The most important feature of the approach is that the unknown thermal resistance is identified by solving appropriate inverse problem from the temperature measurements at the number of sensor located in the wall of the mould. The validity of the solution of the inverse problem is checked by comparison with the results of direct problem. In the present work, a front-tracking method with an automatic mesh generation finite element technique (so-called deforming or moving finite-elements) for steady-state equation conduction-advection problems is developed to build the mathematical model of the heat transfer process. Such an approach makes us possible to find solid-liquid interface location, because it is the integral part of the solution of the considered problem. Due to the strong convective nature of the boundary problem (casting velocity, thermal parameters) the special up-wind technique is applied to avoid the oscillation of numerical results.

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Abstract. District heating technologies should be efficient, effective and environmentally friendly. The majority of the communal heating systems in Poland produce district hot water in coal-fired boilers. A large number of them are considerably worn out, low-efficient in the summer time and will not comply with forthcoming regulations. One of the possible solution for such plants is repowering with new CHP systems or new boilers fuelled with fuels alternative to coal. Optimisation analysis of the target configuration of municipal heat generating plant is analysed in the paper. The work concerns repowering the existing conventional heat generating plant according to eight different scenarios of the plant configuration meeting technical and environmental requirements forecasted for the year of 2035. The maximum demand for heat of the system supplied by the plant is 185 MW. Taking into account different technical configurations on one side, and different energy and fuel prices on the other side, the comparative cost-benefits analysis of the assumed scenarios has been made. The basic economical index NPV (net present value) has been derived for each analysed scenario and the results have been compared and discussed. It was also claimed that the scenario with CHP based on ICE engines is optimal.