# Tri-generation plant on a Day-Ahead market

This project includes two gas fired CHPs, an electric chiller, an absorption chiller, gas fired boilers and a thermal storage. These production units must at all times cover both the cooling demand and the total heat demand which is divided into “Total sale of heat” and “Network loss”. Produced and consumed electricity is traded on a the EPEX Day-ahead market.

An overview of the model is given in the below picture.

energyPRO calculates the optimal operation of the units in the project, which in this model is achieved by minimizing the net heat and cooling production cost. The two CHPs should therefore be operated in hours with high electricity prices and the electric chiller in hours with low electricity prices. The absorption chiller must be supplied with heat in order to run, but this heat must be produced at the lowest possible price. For this reason, the absorption chiller should produce cooling when cheap excess heat is available from the CHPs in hours of high electricity prices. The storage tank will be used to support this strategy by storing excess heat from the CHPs to be used at a later time.

In the below figure, a graphical representation of the operation can be seen. The figure is composed of five graph windows: The top graph shows the EPEX electricity price in every hour. The second graph shows the heat production of the different units and the total heat demand including the heat consumed by the absorption chiller. In the third graph, the electricity production and consumption can be seen. The fourth graph shows the cooling demand and the cooling production from the two chillers. The fifth and last graph shows the storage capacity and its content.

From the figure it can be seen that the two CHPs (red and green colors) are producing in hours with high electricity prices. When excess heat is available and at the same time there is a demand for cooling, the absorption chiller (dark blue color) will consume heat and produce cooling. Since there is no cold storage in the model, cooling must be produced as it is needed and the electric chiller (light blue color) will cover the rest of the cooling demand. The gas boilers are operated only when the heat demand cannot be covered by the CHPs and the storage tank is empty.