José Luz Silveira

Thermoeconomic analysis of an evaporative desiccant air conditioning system

In this paper, a thermoeconomic analysis method based on the first and second law of thermodynamics and applied to an evaporative cooling system coupled to an adsorption dehumidifier, is presented. The main objective is the use of a method called exergetic manufacturing cost (EMC) applied to a system that operates in three different conditions to minimize the operation costs. Basic parameters are the R/P ratio (reactivation air/process air) and the reactivation air temperature. Results of this work show that the minimum reactivation temperature and the minimum R/P ratio corresponds to the smaller EMC. This result can be corroborated through an energetic analysis. It is noted that this case is also the one corresponding to smaller energy loss.

Study of fuel cell co-generation systems applied to a dairy industry

Sao Paulo State Univ, Dept Energy, Coll Engn Guaratingueta, BR-12516410 Guaratingueta, SP, Brazil

FUEL CELL COGENERATION SYSTEM : A CASE OF TECHNOECONOMIC ANALYSIS

Fuel Cell is the emerging technology of cogeneration, and has been applied successfully in Japan, U.S.A. and some OECD countries. This system produces electric power by an electrolytic process, in which chemical substances (the most utilized substances are solid oxide, phosphoric acid and molten carbonate) absorb the components H2 and O2 of the combustion fuel. This technology allows the recovery of residual heat, available from 200°C up to 1000°C (depending on the electrochemical substance utilized), which can be used for the production of steam, hot or cold water, or hot or cold air, depending on the recuperation equipment used. This article presents some configurations of fuel cell cogeneration cycles and a study of the technical and economic feasibility for the installation of the cogeneration systems utilizing fuel cell, connected to an absorption refrigeration system for a building of the tertiary sector, subject to conditions in Brazil.

Analysis of aluminum plates under heating in electrical and natural gas furnaces

This paper analyzes the thermal storage characteristics of aluminum plates in furnaces during their heating for lamination under two sources of heat: an electrical resistance bank and a combustion process carried out with natural gas. The set of equations to model the furnace under operation with electrical energy, for air as the fluid, is presented. This supports the theoretical analysis for the system under operation with natural gas combustion products. A numerical procedure, using the software ANSYS, is applied to determine the convection heat transfer coefficients for heating by the air flow. Temperatures measured in a plate inside a real furnace are used as parameters to determine these coefficients. Then convection and radiation heat transfer coefficients are determined for the natural gas combustion products. Results are compared, indicating a possible gain of 5.5 h in relation to a 19.5 h period of conventional electrical heating per plate.

Thermodynamic Analysis of Direct Steam Reforming of Ethanol in Molten Carbonate Fuel Cell

Sao Paulo State Univ UNESP, Coll Engn Guaratingueta, Dept Energy, BR-12500000 Sao Paulo, Brazil

Hydrogen Production Processes

This chapter discusses the state-of-the-art in terms of hydrogen production processes. At first, the steam reforming reactions of ethanol, biogas, and natural gas are introduced. A study on the catalysts being used in the selected reforming processes is also presented with their respective operating temperatures, feed molar ratio, and conversion rates of reagents. Afterwards, the electrolysis process and types of electrolyzers are presented with the renewable energy sources required for such, as well as the settings adopted for this type of hydrogen production processes. This chapter is concluded with the presentation of the biological hydrogen production process from green algae, with the description of the alga strain and methodology for determining the amount of hydrogen produced.

Thermoeconomic Model Considering the Environment Impacts on Thermoelectric Power Plants: Natural Gas Versus Diesel

In this paper a comparative analysis of the environmental impact caused by the use of natural gas and diesel in thermoelectric power plants utilizing combined cycle is performed. The objective is to apply a thermoeconomical analysis in order to compare the two proposed fuels. In this analysis, a new methodology that incorporates the economical engineering concept to the ecological efficiency once Cardu and Baica [1, 2], which evaluates, in general terms, the environmental impacts caused by CO2 , SO2 , NOx and Particulate Matter (PM), adopting as reference the air quality standards in vigour is employed. The thermoeconomic model herein proposed utilizes functional diagrams that allow the minimization the Exergetic Manufacturing Cost, which represents the cost of production of electricity incorporating the environmental impact effects to study the performance of the thermoelectric power plant [3,4]. It follows that it is possible to determine the environmental impact caused by thermoelectric power plants and, under the ecological standpoint, the use of natural gas as a fuel is the best option compared to the use of the diesel, presenting ecological efficiency values of 0.944 and 0.914 respectively. From the Exergoeconomic point of view of, it was found out that the EMC (Exergetic Manufacturing Cost) is better when natural gas is used as fuel compared to the diesel fuel.Copyright

Estudio técnico del uso de energía solar y biogás en vehículos eléctricos en Ilhabela-Brasil

Actualmente, los sistemas hibridos de generacion de energia se han mostrado como una excelente oportunidad para la generacion de electricidad. En este trabajo se presenta el estudio de uno de estos sistemas considerando dos fuentes de energia disponibles (solar -- biogas) en la isla Ilhabela en el estado de San Pablo -- Brasil, con miras a dotar de energia a vehiculos electricos. Este estudio se basa primeramente en el calculo de la demanda de energia de los vehiculos electricos en esta isla. Luego se determina la capacidad de produccion de biogas en Ilhabela. Posteriormente se efectua un analisis energetico de la planta con una microturbina a biogas para conocer la energia producida y la demanda de biogas. Como ultimo paso, se calcula la cantidad de energia necesaria a ser generada con la planta fotovoltaica. Los resultados muestran que, considerando un indice de insercion de mercado del 4 de los vehiculos electricos, la demanda energetica media es de 46 327 kWh/mes. Por otro lado, la capacidad de produccion de biogas en la isla es dos veces mayor a la necesaria para generar 16 200 kWh/mes. Finalmente, la planta fotovoltaica producira 30 127 kWh/mes.

Economic Studies of Some Hydrogen Production Processes

There are more than ten methods for an economic analysis of energetic systems. Each researcher chooses their own suitable methodology. In the case of hydrogen production processes, there is the need to use a method that permits a comparison of the cost of hydrogen production considering all the processes studied in the previous chapter.

Thermodynamic Analysis of Hydrogen Production Processes

In this chapter, thermodynamic studies are conducted for determining the energy efficiencies of each type of hydrogen production process. In the case of the steam reforming processes, a physicochemical analysis was previously conducted, which was based on the concepts of Gibbs free energy, equilibrium constant, and degree of advancement. In light of pressure and temperature conditions, the energy efficiency levels of such processes are determined. In the case of hydrogen production from renewable electrolytic processes, it was based on the electrolyzer’s efficiency and the average efficiencies of wind, photovoltaic, and hydroelectric power plants. In the case of algae, it was considered the energy contained in the hydrogen being produced and the energy consumption levels during the periods of growth, adaptation, and hydrogen production.