Technical and economic analysis of the reconversion of an existing biogas plant to biomethane production: a case study.

The paper deals with the technical and economic analysis of a project aimed at transforming an existing plant, used for the anaerobic digestion of zoo-technical and agroforest biomass and including a CHP system of about 1 MW of electric capacity, into a facility producing bio-methane for automotive and/or stationary power applications. A comparison of different biogas upgrading technologies is performed, aimed at selecting the technology most appropriate to the size and typology of application under evaluation. Similarly, an analysis is performed to evaluate the opportunity of installing a bio-methane liquefaction facility, to simplify the management and transportation of the fuel, to be used in vehicles. The economic analysis is performed by considering the incentives presently available in Italy for bio-methane producers. Different scenarios are analyzed and discussed, and it was concluded that the conversion of the existing plant into a facility to produce bio-methane to be liquified and sold as fuel for vehicles represents at this moment a very attractive and profitable option

Thermoeconomic optimazation of the condenser in a vapour compression heat pump

In the paper, the design optimisation of a heat exchanger is discussed, using a thermoeconomic approach. The investigation is referred to the tube-in-tube condenser of a conventional vapour-compression heat pump, with a twophase refrigerant flowing in the inner tube and a single-phase fluid flowing in the annulus. A cost function to be minimised is introduced, defined as the sum of two contributions: (i) the amortisation cost of the condenser, related to the heat exchange area;(ii) the operating cost of the electric-driven heat pump in which the heat exchanger will work, depending on the overall exergy destruction rate in the system. In the paper, this latter contribution is related to the local irreversibility rate in the condenser, using the so-called structural approach. The optimal trade-off between amortisation and operating cost is therefore investigated, by minimising the above-mentioned cost function. A numerical example is discussed, in which, for a commercial heat exchanger, the design improvements needed to obtain a cost-optimal configuration are investigated. The analysis is carried out for three different refrigerants: R22, R134a and R410A

Development of a fully explicit matrix inversion free finite element algorithm for the simulation of high temperature fuel cells

Viene presentato un modello 2 e 3-D per l'analisi e la simulazione di celle a combustibile ad ossidi solid

Thermoeconomic optimization of a renewable polygeneration system serving a small isolated community

During the last years, special attention has been paid to renewable polygeneration technologies, able of simultaneously producing thermal, cooling, electrical energy and desalinated water from seawater. This paper focuses on an innovative polygeneration system driven by renewable energy sources, including the following technologies: hybrid photovoltaic/thermal collectors, concentrating parabolic trough (CPVT), a biomass heater, a single-stage absorption chiller and a multiple-effect distillation desalination system. The system is designed to cover the base load of an isolated small community. In previous papers, the dynamic simulation model about plant operation is discussed. In this paper, a detailed exergy, economic and environmental analysis of the plant is presented. In addition, the plant was optimized using different objective functions, applying the Design of Experiment (DoE) methodology which evaluates the sensitivity of the different objective functions with respect to the selected design parameters. The results show that an increase of the storage volume is generally negative, whereas increasing the solar field area involves an increase of the exergy destruction rate, but also an improvement of the CPVT exergy output provided; the final result is an increase of both the exergy efficiency and the economic profitability of the polygeneration system