Thermodynamic Performance Investigation of a Trigeneration Cycle Considering the Influence of Operational Variables

A rational use of fossil fuels together with a growing concerning about environmental issues have led to many researches aiming at an improvement of energy systems performance, trying to develop more economical and also more eco-friendly solutions. A cogeneration system (Combined Heat and Power - CHP) is an alternative technique that produces heat and power consuming less of primary energy sources, especially fossil fuels. Recently trigeneration systems, also named Combined Heat, Cooling and Power (CHCP), have gained great interest for industrial and commercial applications, due to a better energetic efficiency when compared with CHP systems. CHCP is an economical and available technology, demanding a single source of primary energy, with the advantages of saving energy, money, and making a clever user of fossil fuels with benefits to the environment. The main objective of this work is to evaluate the thermodynamic performance of a trigeneration system, using a process simulation software, considering the influence of some operational variables: compression ratio in the compressor, expansion ratio and efficiency of the power cycle turbine; boiler operation pressure; and operational pressure of the absorption cycle in both sides (high and low pressure). Natural gas is used as primary energy source. In the absorption refrigeration cycle the pair solvent-refrigerant used is H2O-NH3. For the base case studied total thermal efficiency was 78% and COP of the absorption refrigeration cycle was 0.57, while for the optimized case these values are 82% and 0.48. The most important operational variables to improve efficiency of the cycle are compressor ratio in the compressor and expansion ratio in the turbine.