Wojciech Kostowski

Thermoeconomic Evaluation of Biomass Conversion Systems

The chapter presents the application of thermoeconomics to the analysis of a sample biomass energy conversion system. Thermoeconomics is aimed at the analysis, optimization and diagnosis of energy conversion systems; it is based on the concept of exergy which is constantly gaining more popularity among engineers and researchers, and the concept of cost. The case study chosen for demonstrating the usefulness of the methodology concerns an integrated biomass gasification and utilization system with an atmospheric fluidized bed gasification unit and a gas turbine unit fed with the produced gas. Definition of fuel and product flows allows one to identify key components responsible for conversion of the largest amounts of exergy. Further concepts of thermoeconomics, such as exergy cost and its formation process allow one to determine the quality of each component of the plant. Attention is paid to the explanation of methodology rather than to particular technological issues, which are explained in the cited references, and are also subject of other chapters of this book.

Effectiveness of the Hydrogen Production, Storage and Utilization Chain

The paper evaluates the effectiveness of a power-to-gas hydrogen chain, comprising the production, storage and utilization sections. The production section is based on alkaline electrolyzers producing about 18.6 kg hydrogen per MWh supplied electric energy derived from renewable (wind) sources. Next, hydrogen is transported to an underground storage facility (UGF), assuming that the pressure of the produced hydrogen is sufficient to provide its transportation to the storage site. Energy demand required for hydrogen compression to the UGF is accounted for, and the maximum level of hydrogen losses is evaluated. Finally, three options for hydrogen utilization are considered: (1) hydrogen is co-fired in a gas turbine, (2) it is supplied to hydrogen vehicles, (3) it is used for process purposes replacing the existing production based on steam methane reforming. Moreover, energy effects related to the replaced oxygen production are optionally taken into account. It has been shown that the choice of a scenario (co-firing//vehicles/process application) and, to a lesser degree, the possibility of using the generated oxygen strongly affects the overall process performance which may vary between low values of 20% (energy generation), 70–80% for process application (replacement of steam methane reforming) and more than 90% for vehicle application (replacement of diesel fuel). In conclusion, the process may provide excellent energy performance for dedicated hydrogen users, and a less favorable yet still considerable option for energy storage for renewable sources.

Exergo-ecological Assessment of Multi-generation Energy Systems

This chapter provides three examples illustrating the usefullness of the concepts of exergy, exergy cost and thermo-ecological cost. The first example is related to exergo-ecological evaluation of adsorption chiller system. System consisted of cogeneration, solar collector and adsorption chiller are analyzed using the concept of thermo-ecological cost. The second example is devoted to thermo-ecological assessment of combined cold-heat-and-power plant CCHP plant supported with renewable energy. The aim of this analysis is to apply the exergo-ecological analysis for selected CCHP trigenaration system based on two renewable resources (biogas/solar radiation). The third example concerns the recovery of exergy from pressurized natural gas. The recovery system comprises a two-stage turbine expander integrated with a co-generation module. The example demonstrates the usefulness of exergy analysis, which, in contrast to energy analysis, provides tools to indicate and quantify the origin of the generated electricity. Finally, the studied case provides a numerical example for the calculation of unit exergy cost and of the thermo-ecological cost along the productive structure of the system.