This paper presents an efficient computational algorithm for selecting the optimal generation mix considering CO₂ emissions. In order to demonstrate the effectiveness and feasibility of the proposed method, a fundamental study of the evaluation of the optimal generation mix for controlling CO₂ emissions is indicated. Furthermore, by using a parametric analysis which considers load characteristics as parameters, a general trend for the optimal generation mix which is affected by controlling CO₂ emissions can be derived.
The proposed method is based on an optimization method known as simulated annealing. In the method, solutions in a generation mix problem are eguivalent to states of a physical system, and the cost of a solution is equivalent to the energy of a state. The proposed method can easily accommodate not noly CO₂ emissions but also many practical constraints of generation expansion planning, such as integer solutions of unit capacities, condition of existing units and so on.
Case studies with various annual load patterns (combinations of annual load factors and the shapes of annual load duration curve) are presented and discussed. Consequently, a general trend for selecting generation technologies that should be added to a power system is derived; i. e., a useful guideline for studying generation expansion planning under controlling CO₂emissions can be provided.

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Electricity markets are experiencing widespread changes that are significantly altering the industry. The purpose of this paper is to analyze the economic consequence of various rules of purchased power pricing and wheeling fees of an electric utility by game theory.
A regulator, an electric utility and a cogenerator are included in this model as players of the game. Consider an extensive game model of an electricity market where a cogenerator sells excess electricity to an electric utility or an end user. The regulator behaves so as to maximize social welfare. The electric utility and the cogenerator intend to maximize their own profit. The wheeling fee between the electric utility and the cogenerator are decided to maximize the sum of incremental profits. We have found that a buy-back system (the utility purchases cogenerated power) and a cogenerator-customer wheeling system are equally efficient and are more desirable than a monopoly system. The buy back rate should be equal to (LP bargaining solution) or less than marginal cost of the electric utility (Nash bargaining solution). We also conducted an analysis of two-period electricity market.

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It is becoming more and more difficult to construct large scale power plants because of environmental problems. Under such circumstances, demand side management for electricity conservation is expected to decrease the demand. However, we need a theoretical framework to introduce electricity conservation technologies into the power system.
In this paper, we have developed a model of Integrated Resource Planning, in which both electridc power stations and the conservation technologies are evaluated as resource of the power system. The model determines the share of electric power plants and conservation technologies by maximizing the social welfare function. As a result, we have derivated the condition, under which conservation technologies could constitute the system. We have also shown simple numerical example, utilizing data of insulation material of house. The result indicates that the insulation material could be a cost-effective resource if the cooling of houses is intensively done.

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This paper proposes a new methodology to assess the economy on the photovoltaic power plant of utilities in an isolated island, where the photovoltaic power is of great advantage since the scale of power system is small and the generating costs of existing plants are high. For this purpose we have developed the method of calculating the capacity credit and the energy credit for photovoltaic power plant by the hourly computer simulation using the standard meteorological data and the daily peak load duration period of the island.
Further we have estimated the allowable generating cost of the photovoltaic power plant by using the capacity and energy credit described above. The economy of photovoltaic power plant is determined by comparing the allowable generating cost with the actual generating cost.
We lastly try to assess the economy of the photovoltaic power plant which would be installed in a certain isolated island in Okinawa.

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Recently, the global environmental problem is one of the most imminent subjects. Useful application of solar energy systems, especially for residences, is expected from the viewpoint of environmental protection.
In this study, on the basis of exergy theory, evaluation is made of a photovoltaic/thermal hybrid panel, which can be applied to household use. In this panel photovoltaic modules are set on a flat-plate type solar collector.
In the first analysis, instantanious exergy characteristics are treated for three types of panels, a solar collector panel, a photovoltaic panel and the hybrid panel. Exergy efficiency of each panel is compared. As a result, it is found that the hybrid panel keeps high exergy efficiency in the range of from low to high intensity of solar radiation. Also optimum conditions of use are examined to get electricity and heat.
In the second analysis, yearly exergy characteristics are treated for them. In the countries where climate changes by season, like Japan, it is necessary to evaluate how much exergy output is got throughout the year. Using HASP climate data (new Tokyo), exergy analysis is made in considering monthly distribution of intensity of solar radiation and atomospheric temperature. As a result, it is clearly shown that the hybrid panel is superior to others in yearly exergy output.

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The stand alone PV power generating system usually has a lead acid battery for the loads during the night or a rainy day. The operating voltage of the lead acid battery widely changes from 1.9 to 2.8V. On the other hand, the optimal operating voltage of the high efficiency PV cell is close to the open circuit voltage of the PV cell. The operating voltage of the PV system is not coincident to the one of PV cell in the stand alone system which has the lead acid battery. The system performance is influenced by the I-V characteristics of the PV cell. So, it is clarified by the annual simulation that the I-V characteristics of the PV cell influence the system capacity as well as the operating voltage of the system.

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Tohoku Electric Power Company constructed a wind park composed of five 275kW windturbines (WT) at a cape TAPPI in AOMORI prefecture in 1991, and has begun an actual proof test from April 1992. A WT has a very unique point compared with other conventional electric power plants that the power of a WT is always fluctuating following the cube of wind speed and start-stop operation in very frequent. On the other hand, an induction generator is widely used for a WT, because it is very cost effective in manufacturing, maintenance and is very reliable. But the induction generator has a weak point producing high voltage fluctuation when connected into grid.
Utility company has an obligation to keep voltage fluctuation within an allowable value, so we have to examine the performance of a WT previously. If there is any ploblem, we must take a suitable conter-measure. In order to evaluate the wind generator performance, simulation seems to be the best way. Hence, we made simulations on transient and normal characteristic of a WT, and found the simulation corresponded with the measured results very well.

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This paper represents the basic studies on the application of SMES (Superconducting Magnetic Energy Storage) to the energy storage for WECS (Wind Electric Conversion System). The WECS assumed in this study is the combination of a self-excited induction generator and DC link system (AC-DC-AC interconnection). By introducing a superconducting coil into the DC portion of the link system, it becomes possible that the fluctuation of the output power from the wind generator due to the wind speed variation is suppressed with the angular velocity of the wind turbine controlled at the maximum output point. Also, the proposed circuit can be used as a normal SMES when the WECS is out of operation.
First of all in this paper, the excitation characteristics of the self-excited induction generator is calculated, and it is made clear that the adjustment of the capacitance is necessary for the high efficiency operation of WECS. Next, the calculation of energy storage to the superconducting coil from the induction generator is done, and a step-down chopper is found required in order to adjust the generator current to the coil current. Furthermore, the conditions are derived for the proposed WECS + SMES to be operated at the maximum output angular velocity under the given wind speed.

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When combined with a magnet having a magnetic field gradient (for example, a permanent magnet), a Y-based oxide superconductor is capable of forming a non-contact bearing with a strong levitational force. Since this bearing exhibits low rotational loss, it is very likely to form a highly efficient power storage system in combination with a flywheel. In this study, an 8 MWh power storage system utilizing a flywheel was conceptually designed to examine its applicability and the possible effects of its introduction. In this study, it was found that this system was an effective power storage.

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Experimental studies and analytic theories are presented on a steam share between exhausted air and exhausted fuel from phosphoric acid fuel cells.
The steam share depends on a fiow rate of air and fuel. The share characteristics can be explained by a steam transport mechanism in which steam carried with air and fuel are combined with steam permeated through an electrolyte layer.
The mechanism is applied to the published analytic theory for fuel cell performance. The revised theory can calculate steam share between air and fuel at each part of a cell. The calculated steam share between exhausted air and exhausted fuel at typical operating conditions of a fuel cell plant is presented.
A simplified method for calculating steam share is developed and shown to give almost the same results with the detailed theory for fuel cell performance.

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Molten carbonate fuel cell (MCFC) power plant is expected to be one of the most promising future power generaton system for the electric utilities because of its high efficiency, environmental suitability and capability of using coal as fuel. To get such attractive performance, it is necessary for the plant to adopt the gas recycling operation system. The authors tested a 6 kW class MCFC stack with three types of gas recyclings such as cathode, anode and carbon dioxide ones, including pressurized conditions.
This paper describes the test results and the effects of the gas recycling operations. Cathode gas recycling is proved to be able to control the stack temperature and give the flexibility for setting oxygen utilization. Anode gas recycling is proved to be able to suppress the methane formation and decrease the deviation of the stacked cell voltages. Including the starting-up process, it is proved that the electricity can be generated from the stack without supplying carbon dioxide from outside the system by carbon dioxide gas recycling. In such a process using burner for carbon dioxide gas recycling, burner temperature must be controlled in the certain value. It is important to adjust the fuel supplying rate, load current and cathode gas recycling ratio each other. At load change process, constant gas utilization operation is effective not to change the burner temperature.

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Zinc/bromine batteries were developed by Meidensha Corporation for load leveling under the “Moon Light Project” by Ministry of International Trade and Industry (MITI). One of problems in the bipolar cell assembly of zinc/bromine batteries is shunt current loss which causes not only a decrease in electrical efficiencies but also non-uniform zinc metal deposition. Computer simulations based on an equivalent circuit model were carried out for estimation of charge and discharge characteristics of a string of the 1MW scale zinc/bromine batteries. The round-trip efficiencies, the residual zinc metal after discharge, the stack currents and the terminal voltage were estimated. The effects of battery configurations and the fluctuation of cell parameters on charge and discharge characteristics are discussed.

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The authors proposed a power consolidation-inversion-control system for the Faraday MHD generator and have already made clear by numerical simulations that the system shows an excellent performance of power consolidation, inversion and control. In the system, the DC power output from each electrode pair is, at first, inverted through the PWM inverter and the AC power outputs are then consolidated by the transformers. The authors newly propose to use the DC consolidation circuit between the MHD generator and the PWM inverter and to consolidate several electrode currents before inversion. In the present study, performance of the power consolidation-inversion-control system along with DC consolidation circuit is investigated in the case the master/slave consolidation circuit is adopted as the DC consolidation circuit. Numerical simulations are carried out and it is confirmed that the system does not degrade the performance of the Faraday MHD generator and has the same excellent performance of power consolidation, inversion and control as the system without DC consolidation circuit.

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The objective of the present paper is to examine predictable cycle efficiency and performance of direct-coal-fired MHD-steam combined power generation system, where coal is burned with oxygen including partly circulated CO₂ and the produced CO₂ is compressed, liquified, and recovered. The performance of the MHD generator of this cycle becomes poor compared with ordinary MHD channel, since the circulated CO₂ reduced electrical conductivity and sound velocity. Even so, predicted cycle efficiency is 41.1% for 1, 000 MW thermal input and 46.4% for 2, 000 MW thermal input, taking into account liquired power for CO₂ liquefaction, resulting in good performance of the cycle.

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We report on the results of the optimization of the cross-sectional shape of a magnet coil system including an MHD channel. This optimization was carried out for a 200 MWe supersonic Faraday-type MHD generator. It was shown that the channel length can be shortened more than 30%, without the decrease of the enthalpy extraction, by the optimization of the coil shape from the crescent shape coil producing a uniform magnetic field. It was also estimated that the capital cost for a commercial MHD/steam combined plant can be decreased more than 6% by this coil shape optimization.

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In the present paper bifurcation phenomena in a supersonic MHD generator are analyzed. The shock-fitting method is utilized for efficient analysis of steady state behavior of the supersonic MHD generator with the supersonic diffuser. The equation to determine the steady state behavior of the generator is derived from the Rankine-Hugoniot conditions at the shock and the relation between load current and load voltage. By solving this equation numerically, the location of the shock in steady state is determined so that the boundary conditions are satisfied at the shock, at the inlet of MHD channel and at the exit of diffuser. The stability of the steady shock is analyzed with the assumption of quasi-steady behavior. During the analysis of a supersonic diagonal type MHD generator we have found bifurcation behavior of the generator such as the jump behavior of the power output and the coexistence of several stable steady states.

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