The Optimal Energy Dispatch of Cogeneration Systems in a Liberty Market

This paper proposes a novel approach toward solving the optimal energy dispatch of cogeneration systems under a liberty market in consideration of power transfer, cost of exhausted carbon, and the operation condition restrictions required to attain maximal profit. This paper investigates the cogeneration systems of industrial users and collects fuel consumption data and data concerning the steam output of boilers. On the basis of the relation between the fuel enthalpy and steam output, the Least Squares Support Vector Machine (LSSVM) is used to derive boiler and turbine Input/Output (I/O) operation models to provide fuel cost functions. The CO2 emission of pollutants generated by various types of units is also calculated. The objective function is formulated as a maximal profit model that includes profit from steam sold, profit from electricity sold, fuel costs, costs of exhausting carbon, wheeling costs, and water costs. By considering Time-of-Use (TOU) and carbon trading prices, the profits of a cogeneration system in different scenarios are evaluated. By integrating the Ant Colony Optimization (ACO) and Genetic Algorithm (GA), an Enhanced ACO (EACO) is proposed to come up with the most efficient model. The EACO uses a crossover and mutation mechanism to alleviate the local optimal solution problem, and to seek a system that offers an overall global solution using competition and selection procedures. Results show that these mechanisms provide a good direction for the energy trading operations of a cogeneration system. This approach also provides a better guide for operation dispatch to use in determining the benefits accounting for both cost and the environment in a liberty market.

Automation Control Method of Time-Varying in Heat Conduction Coefficient and Pure Steam Output Interference

The relation curve of the raw water flow and main steam pressure under different main stream temperature is established by off-line experiments and expert experiences. For the time-varying in heat conduction coefficient, which is resulted by scaling and so on, water level need to be detected by installing float level gauge in every effect, and the curve can be corrected according to water level, so effective separation space of gas and water is ensured to avoid dry or flood pot. Because medical water distiller need to provide pure steam, by detecting the output flow of pure steam, correct the curve and inhibit the interference of production process due to pure steam output, then the production process of distilled water can be finished by automatically controlling the adjustable valves of raw water flow and main stream pressure. The method will improve the robustness of heat conduction coefficient time-varying and pure steam output interference.

Cogeneration - Interactions of Gas Turbine, Boiler and Steam Turbine

A gas turbine cogeneration plant produces power and process steam. Under the PURPA law, surplus electric power can be sold to the local utility. Since process steam generally cannot be exported, it is better to have an excess of power than an excess of steam. Because of low rates offered for surplus power, or for other possible reasons, an owner may not wish to sell power, so it may be necessary to operate at a power-to-steam ratio that does not match the outputs of a gas turbine with a simple heat recovery boiler. If more steam is needed, supplementary firing may be included in the heat recovery boiler. If the need is for more power, a back pressure steam turbine can be included. This reduces the steam output by requiring higher steam pressure. Further power increase and steam reduction can be obtained with a condensing steam turbine. If neither the full steam output nor additional power is required, capital cost can be reduced by inclusion of a smaller, less-efficient heat recovery boiler. This paper compares these means of adjusting the power and steam outputs of a gas turbine cogeneration system to obtain the most cost effective system.