Methodologies for the evaluation of polygeneration systems

Polygeneration is widely recognized as one of the most promising technologies for the rational and efficient use of energy in industrial and civil sectors. Due to the simultaneous production of multiple outputs and the unsteady operating conditions observed in a number of applications, a systematic assessment of the economic, energetic, and environmental performance requires the use of appropriate indicators and approaches. In this chapter a brief overview of such evaluation methods is presented, clarifying the main strengths and weaknesses of each of them and providing a solid conceptual basis to address the controversial arguments. The overview necessarily covers the main assessment methods adopted in national and sovranational legislative frameworks, and it also includes some interpretive approaches such as thermoeconomic and exergoenvironmental analysis. Regarding the last point, a number of case studies discussed in the literature have been briefly presented to illustrate the proven capabilities and drawbacks of the different approaches.