Satoshi Gamou

Parametric study on economic feasibility of microturbine cogeneration systems by an optimization approach

Economic feasibility of microturbine cogeneration systems is investigated by analyzing relationships between the optimal number of microturbine units and the maximum energy demands under various conditions. For this purpose, a method to obtain the maximum energy demand at which the optimal number changes is proposed by combining a nonlinear equation problem and an optimal unit sizing problem hierarchically. Based on the proposed method, a map expressing the aforementioned relationships can be illustrated. Through numerical studies carried out on systems installed in hotels by changing the electrical generating efficiency and the capital unit cost of the microturbine cogeneration unit as parameters, the influence of the parameters on the economic feasibility of the microturbine cogeneration system is clarified.

Optimal Operational Planning of Cogeneration Systems With Microturbine and Desiccant Air Conditioning Units

Economic and energy-saving characteristics of cogeneration systems with microturbine and desiccant air-conditioning units are investigated on system operational planning. An optimization approach is adopted to rationally evaluate these characteristics. In this approach, on/off and rated/part load status of operation of equipment and energy flow rates are determined so as to minimize the hourly energy charge subject to satisfaction of energy demand requirements. In this optimization problem, performance characteristics of the microturbine and desiccant air-conditioning units are modeled in consideration of the influence due to ambient air temperature. Moreover, the influence due to ambient air humidity is also considered in the desiccant air-conditioning unit using the psychrometric diagram. The implementation of the numerical analysis method, discussed in this paper, to two cogeneration systems, clearly shows economic and operational benefits of using desiccant air-conditioning.

An Optimal Renewal Planning of Energy Supply System From Economic Viewpoint

An optimal planning method of renewal planning for energy supply systems is proposed to determine the proper renewal year and selection as to what kind of equipment is suitable for several types of buildings from economic viewpoint. In this method, they are determined together with maximum contract demands of utilities such as electricity and natural gas so as to minimize the annual total cost in consideration of system’s annual operational strategies corresponding to seasonal and hourly energy demand requirements during every evaluation year considered. A numerical study is carried out for an office building with a total floor area of 15 000m2 , where the system is consisted of an electric refrigerator and a steam boiler. Through the numerical calculation, the influence of the following items are clarified on the optimal renewing year and selection of renewing equipment of the system by the parametric study; (a) upgrading technology of the equipment in the future; (b) initial capital cost of equipment; (c) renewing construction cost and trade-in value rate; and (d) interest rate.© 2005 ASME

Structural Synthesis of Energy Supply Systems by Multiobjective Optimization Approach

Based on multiobjective optimization approach, a planning method is proposed for structural synthesis of energy supply systems, by which types, numbers and capacities of systems equipment can be determined rationally from economic, energy saving and environmental viewpoints. Assuming a super-structure system for an office building, the economically optimal system is synthesized with the hybrid structure of electric and gas-consumed equipments. Through the trade-off analysis, it is also clarified that by permitting the total cost increase up to 4%, 22% primary energy and 18% CO2 emission reductions can be achieved, where high efficiency electric-consumed equipments are installed preferentially.

Analysis of Optimal Unit Numbers and Sizes for Microturbine Cogeneration Systems

The relationships between unit numbers and capacities to be installed for microturbine cogeneration systems are analyzed from an economic viewpoint. In analyzing, an optimization approach is adopted. Namely, unit numbers and capacities are determined together with maximum contract demands of utilities such as electricity and natural gas so as to minimize the annual total cost in consideration of annual operational strategies corresponding to seasonal and hourly energy demand requirements. This optimization problem is formulated as a large-scale mixed-integer linear programming one. The suboptimal solution of this problem is obtained efficiently by solving several small-scale subproblems. Through numerical studies carried out on systems installed in hotels by changing the electrical generating/exhaust heat recovery efficiencies, the initial capital cost of the microturbine cogeneration unit and maximum energy demands as parameters, the influence of the parameters on the optimal numbers and capacities of the microturbine cogeneration units is clarified.Copyright

Optimal Operational Planning of Cogeneration Systems With Microturbine and Desiccant Air-Conditioning Units

Economic and energy-saving characteristics of cogeneration systems with microturbine and desiccant air-conditioning units are investigated on system operational planning. An optimization approach is adopted to rationally evaluate these characteristics. In this approach, on/off and rated/part load status of operation of equipment and energy flow rates are determined so as to minimize the hourly energy charge subject to satisfaction of energy demand requirements. In this optimization problem, performance characteristics of the microturbine and desiccant air-conditioning units are modeled in consideration of the influence due to ambient air temperature. Moreover, the influence due to ambient air humidity is also considered in the desiccant air-conditioning unit using the psychrometric diagram. The implementation of the numerical analysis method, discussed in this paper, to two cogeneration systems, clearly shows economic and operational benefits of using desiccant air-conditioning.Copyright

Parametric Study on Economic Feasibility of Microturbine Cogeneration Systems by an Optimization Approach

Economic feasibility of microturbine cogeneration systems is investigated by analyzing relationships between the optimal number of microturbine units and the maximum energy demands under various conditions. For this purpose, a method to obtain the maximum energy demand at which the optimal number changes is proposed by combining a non-linear equation problem and an optimal unit sizing problem hierarchically. Based on the proposed method, a map expressing the aforementioned relationships can be illustrated. Through numerical studies carried out on systems installed in hotels by changing the electrical generating efficiency and the capital unit cost of the microturbine cogeneration unit as parameters, the influence of the parameters on the economic feasibility of the microturbine cogeneration system is clarified.Copyright

Economic Feasibility Study of Micro Gas Turbine Cogeneration Systems by an Optimization Approach

Economic characteristic of micro gas turbine cogeneration systems for commercial and public purposes is evaluated rationally by an optimization method. The number of multiple kinds of micro gas turbine cogeneration units, capacities of other pieces of equipment and utility maximum contract demands are determined so as to minimize the annual total cost in consideration of operational strategies for energy demand requirements. Numerical studies are carried out on systems installed in hotels or office buildings. Through the studies, the following are clarified: (a) the relationships between the number of the installed micro gas turbine cogeneration units and the maximum electricity demands of hotels and office buildings, and (b) the economic effects of the micro gas turbine cogeneration units.Copyright

Optimal Unit Sizing of Cogeneration Systems with a Fuel Cell in Consideration of its Failures.

Economic feasibility of cogeneration systems with a fuel cell is investigated in consideration of its failures. An optimal unit sizing method is extended to this case so that it enables to consider probability of the failures. Equipment capacities and maximum contract demands of utilities are determined so as to minimize an expectation value of the annual total cost by taking account of the systems operational strategy to satisfy hourly changing energy demands even if fuel cells failures happen. Parametric studies are carried out to investigate the influence on economy of the length of down time due to the failures, the repair cost of the fuel cell or annual average frequency of failures. Through the studies, it is found that the failures of the fuel cell greatly influence systems economy, and that the aforementioned parameters greatly change equipment capacities and economy of the fuel cell cogeneration system.

Comparative Analysis of Gas Turbine Cogeneration Systems for Designated Electric Supply.

Economic and energy-saving properties of simple-and combined cycle gas turbine cogeneration systems for use as a designated electric supply are compared. In this supply, the properties are influenced by an electricity supply obligation. An optimization approach is adopted to efficiently evaluate the influence on the properties. Using this approach, equipment capacities and a maximum contract demand of town gas are determined to minimize the annual total cost in consideration of operation strategies for energy demand requirements and of the electricity supply obligation. Numerical studies are carried out using the capital unit cost of a cogeneration unit and the unit cost of energy charge of town gas as parameters. The results show that the combined-cycle system is more suitable as a designated electricity supply, but the unit costs for electricity supply by both systems do not become lower than that by power company unless the parameters are very small.