Application of a cost-benefit model to evaluate the investment viability of the small-scale cogeneration systems in the Portuguese context

Increasingly, modern society is dependent on energy to thrive. Remarkable attention is being drawn to high energy-efficient conversion systems such as cogeneration. World energy sustainability depends on the rational use of energy, fulfilling the demands without compromising the future of energy supply. The market trends foresee the use of decentralized production and the increasing replacement of conventional systems by small-scale cogeneration units as solutions to meet the energy needs of the building sector. Analysing the influence of the variables that determine the economic viability of decentralized energy production systems has become more important given the scenario of energy dependence and high energy costs for the final consumer. A cost-benefit model was developed and presented to identify the potential of small commercial scale cogeneration systems in the Portuguese building sector, based on cost-benefit analysis methodology. Five case-scenarios were analysed based on commercial models, using different technologies such as internal combustion engines, gas turbines and Stirling engines. A positive value of CBA analysis was obtained for all the tested cases, however, the use of classic economic evaluation criteria such as the net present value, internal rate of return and payback period results led to different investment decisions. The model also highlights the influence of energy prices in the economic viability of these energy power plants. The inclusion of subsidized tariffs for efficient energy production is the most contributing aspect in the analysis of the economic viability of small-scale cogeneration systems in the Portuguese building sector. Only in that case, it would be possible for an investor to recover the capital costs of such technology, even if the technical and societal benefits are accounted for

Exergetic evaluation of psychrometric processes

This research had, as its principal objective, the application of the methodology to evaluate psychometric processes through the use of theory which combines the First and Second Principles of Thermodynamics into an adapted system of generating psychometric processes. With the Psychometric Processes System Generator (SIGEP) and other appropriate equipment, where air flow and electrical power from different systems of air conditioning were the most important variables. It was feasible to obtain data of dry and wet bulb temperature, from different locations of the SIGEP's control volume. These variables, plus the local atmospheric pressure, were enough to determine the state of the air inlet and outlet, which made possible the energetic and exergetic analysis. It was possible to conclude that the methodology based on the evaluation through the First and Second Principle of Thermodynamics was technically viable on the analysis of psychrometric processes. It can be observed that energetic evaluation, in almost every process generated by the SIGEP, provided less rigorous criteria than exergetic analysis. It can be also concluded that the equipments attached to the SIGEP had a high level of irreversibility due to the fact they were designed to meet a specific psychrometric condition, regardless of the level of efficiency at that time.Este trabalho teve como objetivo principal a aplicação da metodologia de avaliação dos processos psicrométricos utilizando os conceitos definidos pela combinação das 1ª e 2ª Leis da Termodinâmica, num sistema adaptado para a geração dos processos psicrométricos. Com equipamentos e instrumental adequados variaram-se, basicamente, em cada processo gerado pelo Sistema Gerador de Processos Psicrométricos (SIGEP), as vazões e as potências elétricas requeridas pelos diferentes sistemas de condicionamento do ar e as temperaturas de bulbo seco e de bulbo úmido de pontos estratégicos, dentro e fora do volume de controle, a fim de se efetuar as análises energéticas e exergética. Pode-se concluir que a metodologia de avaliação pela 1ª e 2ª Lei da Termodinâmica aplicada em processos psicrométricos é tecnicamente viável. Comprovou-se, ainda, através dos resultados obtidos, que a avaliação baseada exclusivamente na 1ª Lei da Termodinâmica (avaliação energética), em quase a totalidade dos processos gerados pelo SIGEP, é menos abrangente que a avaliação exergética. Pode-se concluir, também, que os equipamentos, acoplados ao SIGEP apresentaram um alto índice de irreversibilidade devido ao fato de terem sido dimensionados, exclusivamente, com a finalidade de atingir uma condição psicrométrica específica e não, de serem eficientes, do ponto de vista termodinâmico.421428Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Economic evaluation of dried banana production of the organic and conventional systems

This work reports an economic evaluation of the dried banana production from an agroindustry located in Guaraqueçaba - PR State, Brazil. The conventional and the organic banana processings were evaluated by comparing the economic viability pointers. The dried organic banana is exported to the Europe and the dried conventional banana is commercialized in the region of Curitiba - PR. Both processings presented positive economic viability, however the dried organic banana presented better indices (TIR 94%, VPL R$486,009.39 and benefit cost relation of 2.11) than the conventional dried banana (TIR 14$ 34,668.00 and benefit cost relation of 1.17). The dried organic banana presented a cost of production of R$3.64, being 50.1$ 3.21, being 45.3% for insumos and 31.2% for labour.Neste trabalho, foi realizada a avaliação econômica da produção de banana-passa de uma agroindústria localizada no município de Guaraqueçaba - PR. Foi avaliado o processamento da banana-passa convencional e da banana orgânica produzida na região, comparando-se os indicadores de viabilidade econômica. A banana-passa orgânica é exportada para a Europa e a banana-passa convencional é comercializada na região de Curitiba - PR. Ambos os processamentos apresentaram viabilidade econômica positiva, apresentando a banana-passa orgânica os melhores índices (TIR 94%, VPL R$486.009,39 e relação benefício-custo de 2,11) do que a banana-passa convencional (TIR 14$ 34.668,00 e relação benefício-custo de 1,17). A banana-passa orgânica apresentou um custo de produção de R$3,64, sendo 50,1$ 3,21, sendo 45,3% para insumos e 31,2% para mão-de-obra.47348

Synthesis and parameter optimization of a combined sugar and ethanol production process integrated with a CHP system

The combined sugar and ethanol production process from sugar cane is a paradigmatic application for energy integration strategies because of the high number of hot and cold streams involved, the external hot utility requirement at two temperature levels for juice evaporation and crystallization, and the electricity demand for juice extraction by milling. These conditions make it convenient to combine the sugar-cane process with a CHP system fuelled by bagasse, the main by-product from juice extraction. The strategies, tools and expertise on energy integration developed separately by the research teams authoring this paper are applied here jointly to optimize the synthesis and the design parameters of the process and of the total site starting from the basic idea of dissociating the heat exchanger network design problem from the total site synthesis problem. At first the minimization of the external heat requirement for the process alone is pursued and results show that a one third reduction can be achieved by optimal heat integration. Then the use of the by-product bagasse for on-site power generation is considered and two bagasse-fuelled CHP systems are optimized along with some parts of the sugar and ethanol production process in order to obtain maximum total site net power. Results show a variety of interesting scenarios of combined sugar, ethanol and electricity production plants with considerably high electricity output

Avaliação exergética de processos psicrométricos

Este trabalho teve como objetivo principal a aplicação da metodologia de avaliação dos processos psicrométricos utilizando os conceitos definidos pela combinação das 1ª e 2ª Leis da Termodinâmica, num sistema adaptado para a geração dos processos psicrométricos. Com equipamentos e instrumental adequados variaram-se, basicamente, em cada processo gerado pelo Sistema Gerador de Processos Psicrométricos (SIGEP), as vazões e as potências elétricas requeridas pelos diferentes sistemas de condicionamento do ar e as temperaturas de bulbo seco e de bulbo úmido de pontos estratégicos, dentro e fora do volume de controle, a fim de se efetuar as análises energéticas e exergética. Pode-se concluir que a metodologia de avaliação pela 1ª e 2ª Lei da Termodinâmica aplicada em processos psicrométricos é tecnicamente viável. Comprovou-se, ainda, através dos resultados obtidos, que a avaliação baseada exclusivamente na 1ª Lei da Termodinâmica (avaliação energética), em quase a totalidade dos processos gerados pelo SIGEP, é menos abrangente que a avaliação exergética. Pode-se concluir, também, que os equipamentos, acoplados ao SIGEP apresentaram um alto índice de irreversibilidade devido ao fato de terem sido dimensionados, exclusivamente, com a finalidade de atingir uma condição psicrométrica específica e não, de serem eficientes, do ponto de vista termodinâmico

Avaliação econômica da elaboração de banana-passa proveniente de cultivo orgânico e convencional

Neste trabalho, foi realizada a avaliação econômica da produção de banana-passa de uma agroindústria localizada no município de Guaraqueçaba - PR. Foi avaliado o processamento da banana-passa convencional e da banana orgânica produzida na região, comparando-se os indicadores de viabilidade econômica. A banana-passa orgânica é exportada para a Europa e a banana-passa convencional é comercializada na região de Curitiba - PR. Ambos os processamentos apresentaram viabilidade econômica positiva, apresentando a banana-passa orgânica os melhores índices (TIR 94%, VPL R$486.009,39 e relação benefício-custo de 2,11) do que a banana-passa convencional (TIR 14$ 34.668,00 e relação benefício-custo de 1,17). A banana-passa orgânica apresentou um custo de produção de R$3,64, sendo 50,1$ 3,21, sendo 45,3% para insumos e 31,2% para mão-de-obra

New alternatives for the fermentation process in the ethanol production from sugarcane: Extractive and low temperature fermentation

Ethanol is produced in large scale from sugarcane in Brazil by fermentation of sugars and distillation. This is currently considered as an efficient biofuel technology, leading to significant reduction on greenhouse gases emissions. However, some improvements in the process can be introduced in order to improve the use of energy. In current distilleries, a significant fraction of the energy consumption occurs in the purification step distillation and dehydration since conventional fermentation systems employed in the industry require low substrate concentration, which must be distilled, consequently with high energy consumption. In this study, alternatives to the conventional fermentation processes are assessed, through computer simulation: low temperature fermentation and vacuum extractive fermentation. The aim of this study is to assess the incorporation of these alternative fermentation processes in ethanol production, energy consumption and electricity surplus produced in the cogeneration system. Several cases were evaluated. Thermal integration technique was applied. Results shown that the ethanol production increases between 3.3% and 4.8% and a reduction in steam consumption happens of up to 36%. About the electricity surplus, a value of 85 kWh/t of cane can be achieved when condensing extracting steam turbines are used. (C) 2014 Elsevier Ltd. All rights reserved

Design of Evaporation Systems and Heaters Networks in Sugar Cane Factories Using a Thermoeconomic Optimization Procedure*

Abstract Sugar cane production in Brazil is one of the most competitive segments of the national economy, producing sugar and ethanol for internal and external markets. Sugar production is done basically in several steps: juice extraction, juice clarification and evaporation, syrup treatment and sugar boiling, crystallization, centrifugation and drying. Much heat exchange equipment is used in this process.. An optimized design of the evaporation system with the correct distribution of the vapor bleed to attend other parts of the process may contribute to exhausted steam demand reduction. This paper presents a thermoeconomic optimization of the evaporation system and the heaters network of a sugar factory, aiming at minimum investments and operation costs. Data from Brazilian sugar factories were used to define the process parameters. The methodology proposed is used to evaluate the cost of the steam consumed by the factory and the optimized design of the equipment

Double-effect distillation and thermal integration applied to the ethanol production process

A double-effect distillation system allows a significant reduction in energy consumption, since the condensers and reboilers of different columns can be integrated thermally. To achieve this goal, some columns operate under a vacuum, while others operate close to atmospheric pressure. These pressure levels bring about different temperature levels, allowing energy recovery. Thus, the aim of this study is to assess the incorporation of double-effect distillation in ethanol production, and its impact on energy consumption and electricity surplus production in the cogeneration system. Moreover, because double-effect distillation and thermal integration involve an increase in equipment costs, an economic assessment was done. Several cases were evaluated and a thermal integration technique was applied, in order to integrate the overall process. The thermal integration study showed that it is possible to integrate the juice concentration step (multiple effect evaporation system) in the overall process without additional thermal consumption, through the selection of a suitable set of pressures in the evaporation system. The results showed a reduction in steam consumption of between 17% and 54%, in comparison with the Base Case. Regarding the electricity surplus, this increased by up to 22% when extraction condensing steam turbines were adopted. (C) 2015 Elsevier Ltd. All rights reserved

Synthesis and Parameter Optimization of a Combined Sugar and Ethanol Production Process Integrated with a CHP System, Part 1: Minimization of the process external heat requirement

The combined sugar and ethanol production process from sugar cane is a paradigmatic application for energy integration strategies because of the high number of hot and cold streams involved, the external hot utility requirement at two temperature levels for juice evaporation and crystallization, and the electricity demand for juice extraction by milling. These conditions make it convenient to combine the sugar cane process with a CHP system fuelled by bagasse, the main by-product from juice extraction. The strategies, tools and expertise on energy integration developed separately by the research teams authoring this paper are applied here jointly to optimize the synthesis and design parameters of the process and of the total site starting from the basic idea of dissociating the heat exchanger network design problem from the total site synthesis problem. In the first part of the paper the objective is the minimization of the external heat requirement for the process alone. Results show a one third reduction of the process hot utility requirement