José Joaquim Conceição Soares Santos

Otimização Operacional de um Sistema de Trigeração para Atender Demandas Variáveis

LOVATI, C. V. (2015), Operational optimization of a Trigeneration System to Meet the Demand Horosazonal Variation, Vitoria, 141 p. Dissertation (Masters in Mechanical Engineering) – Technological Center, Universidade Federal do Espirito Santo. This paper aims to present and discuss the procedures and results of the optimization of the operational strategies of a trigeneration system of a research center to meet horosazonal demand for electricity, steam and chilled water by minimizing the operating cost of the plant. Nowadays more and more the thermal systems are more complex. Thus, it seeks to better use in order to have better production and minimizing production costs. The research center analyzed consists of a cogeneration system that produces electricity and also heat (steam and hot water) to drive two absorption chillers (one fulled by steam and one by hot water). This center also has other generators and additional chillers. Besides the equipment also has the option of use an additional electrical demand with the dealership. The main goal of optimization is to determine how to operate the trigeneration system of the center and when or how to use the contracted electrical demand. To achieve this result, all data of the equipment and plant costs, and also the data demand of the center, were raised and the mathematical model was developed. In this point of view there are many optimization methods that can be employed. In this paper the mathematical optimization is used through the generalized reduced gradient method with the help of the Solver in Excel Microssoft. The results show that the optimization method is very effective giving favorable results.

Application of Thermoeconomics for CO2 Allocation for Net Power and Useful Heat in a Gas Turbine Cogeneration System

Thermoeconomics is a discipline that connects Thermodynamics and Economics concepts, usually used for rational cost assessment of the final products of a thermal plant, by means of a model which describes the cost formation process of the overall system. Generally, exergy or monetary costs of the external resources are distributed to the final products. However, environmental consideration can be incorporated in the models to calculate the environmental costs, such as specific CO2 emission of each final product. This work aims at demonstrating how the thermoeconomic models can be adapted or modified in order to allocate the overall CO2 emission of a gas turbine cogeneration system to the final products (net power and useful heat), in order to determine the specific CO2 emission (g/kWh) of each product. This subject is an important step in the applications of Life Cycle Assessment in plants with two or more products and also to quantify the environmental cogeneration advantage. It also reveals that any thermoeconomic model can be adapted for allocation of the overall CO2 emissions or any other pollutant to the final products of a multi-product plant.

Exergy Analysis and Fuel Exergy Allocation in a HTGR Direct Combined Cycle

An exergy and a thermoeconomic analyses are carried out to a high temperature gas-cooled reactor (HTGR) direct combined cycle. The thermoeconomic approach used is the H&S Model, which is based on the disaggregation of physical exergy into its enthalpic and entropic terms. This approach allows the isolation of dissipative components of the productive structure, as condensers. The goal is to calculate the irreversibilities of each subsystem and the exergetic unit cost of each internal flow and product of the system.Results show that the H&S Model yields consistent results, because exergetic unit costs of internal flows are greater than one and product-fuel ratio of each productive unit are less than one. Besides the allocation of external fuels of the plant, i.e., the nuclear fuel and the fossil fuel, it is shown that the H&S Model can be used in order to quantify both internal and external irreversibilities, as well as the conventional exergy analysis, because the differences between the defined fuels and products of each unit or subsystem of the productive structure are equal to the sums of the exergy destruction and exergy loss values of each unit of the physical structure evaluated by the exergy balance.Copyright