172 research outputs found
The Gouy-Stodola Theorem and the derivation of exergy revised
No full textThe Gouy-Stodola Theorem is the theoretical basis for allocating irreversibility and for identifying the maximum possible efficiency for any kind of energy conversion system. The well-known theorem is re-obtained in this paper, relaxing the hypothesis about a constant value for temperature and pressure of the reference environment. The equations that have been derived taking into account the variation of reference temperature and pressure show that two additional terms appear in both reversible and irreversible maximum useful work output, besides the well-known terms. These additional terms take into account the potential useful work (exergy) destruction related to the variation of the ambient condition during the considered time interval. In this way the Gouy-Stodola Theorem still holds, but the allocation of exergy destruction is generally different from that calculated in the usual hypothesis of constant temperature and pressure of the reference environment. The Gouy-Stodola Theorem is also used in various textbooks for defining the flow and the non-exergy of a control volume. The same approach is applied in this paper, highlighting the differences and the difficulties related to the variation of the reference pressure and temperature in the reference environment
The future of Thermoeconomics: from industrial cost minimization toward cumulative resources accounting and sustainability assessment
No full textThermoeconomics has been developed with the main object of first identifying, and then reducing the costs of the energy produced by industrial power plants. More recently, the same approach formalized in the Exergy Cost Theory has been recognized as a useful tool also in a wider field, like industrial symbiosis and sustainability assesment. To do this, exergy supply chains have been tracked backward and backward, to include in the primary resource consumption a more and more complete inventory of the indirect consumption. In Authors' opinion, the future of Thermoeconomics is to go on in this directions. If a very complete inventory of all indirect consumption were obtained, the sustainability assessment of a production process could be performed (at least in principle) by applying the idea that the lower its consumption (direct and indirect) of scarce primary resources, the more sustainable a production process is. In this paper, the idea of the Thermoeconomic Environment (TEE) is summarized, to highlight as it is a consistent ultimate boundary of the exergy cost accounting, where the origin of the exergy supply chains can be properly placed. Then, the frame of the TEE is used to discuss some possible options for obtaining a more complete inventory of all indirect consumption, and to outline possible perspective connections with some relevant environmental models, coming from Biology, Dynamic of Populations, or Climatology
Applicazione della simulazione termoeconomica allo studio dei parametri di progetto della sezione a vapore di un impianto combinato. Parte B: Influenza della valorizzzione dell'energia elettrica prodotta sul costo di produzione dell'energia termica.
No full text
L'approccio termoeconomico allo studio e all'ottimizzazione degli impianti di conversione energetica
No full textEnergy production through distributed urban cogeneration systems: preliminary definition of lay-out, units size and operation
No full textORC technology for waste-wood to energy conversion in the furniture manufacturing industry
No full textExploitation of low and medium temperature thermal sources, in particular those based on biomass combustion and on industrial residual heat recovery, has been increasingly investigated in the last decades, accordingly to the growing interest towards reduction in primary energy consumption and environmental issues. Organic Rankine Cycle (ORC) technology allows designing power plants that are less demanding in terms of auxiliaries, safety systems, maintenance and operating costs when compared to conventional water steam power plants.
To support the preliminary technical and economic design of this kind of plants in different contexts, a simulation code of part load and off-design operation of an ORC unit for Combined Heat and Power (CHP) has been developed. In the paper, taking the real situation of a furniture manufacturing factory as a starting point, it is shown how all energy flows occurring all year long inside the CHP plant, can be estimated on the basis of the thermal user duty time profile, the available biomass flow rate and the adopted operation strategy. This information is the basis in order to correctly evaluate the energetic, economic and environmental advantages of the proposed technical solution, with respect to a particular context, as it is shown in the concluding part of the paper
Optimization of a distributed Cogeneratio System with solar District Heting
No full textThe aim of the paper is to identify the optimal energy production system and its optimal operation strategy required to satisfy the energy demand of a set of users in an industrial area. A distributed energy supply system is made up of a district heating network, a solar thermal plant with long term heat storage, a set of Combined Heat and Power units and conventional components also, such as boilers and compression chillers. In this way the required heat can be produced by solar thermal modules, by natural gas cogenerators, or by conventional boilers. The decision variable set of the optimization procedure includes the sizes of various components, the solar field extension and the thermal energy recovered in the heat storage, while additional binary decision variables describe the existence/absence of each considered component and its on/off operation status.
The optimization algorithm is based on a Mixed Integer Linear Programming (MILP) model that minimizes the total annual cost for owning, maintaining and operating the whole energy supply system. It allows to calculate both the economic and the environmental benefits of the solar thermal plant, cooperating with the cogeneration units, as well as the share of the thermal demand covered by renewable energy, in the optimal solutions.
The results obtained analyzing different system configurations show that the minimum value of the average useful heat costs is achieved when cogenerators, district heating network, solar field and heat storage are all included in the energy supply system and optimized consistently. Thus, the integrated solution turns out to be the best from both the economic and environmental points of view. (C) 2014 Published by Elsevier Ltd
L’ottimizzazione locale dei componenti di un sistema energetico; Parte II°: Applicazione ad un impianto a vapore
No full textTermoeconomia,Fuel Impact,Ottimizzazion
- …
