A cogeneration plant with a small gas turbine was installed in a pharmaceutical factory and instrumented for acquiring all the values necessary to appraise both its energetic and cost advantages. The plant was designed and built as a demonstrative project under a program for energy use improvement in industry, partially financed by the European Union. The system comprises as its main components: 1) a gas turbine cogeneration plant for production of power and thermal energy under the form of hot water, superheated water, and steam; 2) a two-stage absorption unit, fueled by the steam produced in the cogeneration plant, for production of cooling thermal energy. The plant was provided with an automatized control system for the acquisition of plant operating parameters. The large amount of data thus provided made it possible to compare the new plant, under actual operating conditions, with the previously existing cooling power station with compression units, and with a traditional power plant. This comparative analysis was based on measurements of the plant operating parameters over nine months, and made it possible to compare actual plant performance with that expected and ISO values. The analysis results reveal that gas turbine performance is greatly affected by part-load as well as ambient temperature conditions. Two-stage absorber performance, moreover, turned out to decrease sharply and more than expected in off-design operating conditions.

The aim of the paper is to study the performance of a power plant for the combined production of electrical, thermal and cooling thermal energy. The exergy analysis was developed from the system’s operating conditions measured in a previous experimental phase, and allowed description and quantification of causes of efficiency loss in the plant. The following thermoeconomic analysis, based on the exergy balance, allowed appraisal of the actual costs of each component and possible optimization of the plant for higher efficiency and cost saving. The thermoeconomic results lead to a better understanding of the influence of off-design operating conditions on the performance of the whole plant and on this basis further improvements and modifications are envisaged. Three modifications of the plant layout are described and discussed, in greater detail for the most promising of them, i.e., compressor inlet air cooling with absorber excess cooling power production. Results show that this solution is particularly effective in the present case, not only from the energetic point of view, but, as is not always the case, also form the economic one. The application of thermoeconomic analysis to the pharmaceutical factory under study has the aim of identifying those components which have the highest cost quantifying losses in cost terms.