It is expected that power generation systems utilizing solar energy and technologies of capturing carbon dioxide (CO2) from stack gas should be introduced under constraints of CO2 emission in the future. In this paper, characteristics and economics of power generation systems utilizing solar energy are evaluated and compared with those of an integrated coal gasification combined cycle plant (IGCC) when carbon tax is imposed as an economic penalty for CO2 emission. The investigated power generation systems utilizing solar energy are as follows: a solar photovoltaic system (PV system) and a hybrid power generation system utilizing solar thermal energy (HB system) which has been proposed by the authors. The cases of capturing CO2 for the HB system and the IGCC are also investigated. The location of the systems is assumed to be Ottawa where the total horizontal solar radiation energy is approximately as same as the world average. It has been shown that the unit cost of the HB system without capturing CO2 is lower than that of the IGCC when the carbon tax is 3_??_4×104 yen/t-C. The CO2-capturing HB system can be economically preferable when the carbon tax is raised to 4_??_5×104 yen/t-C. The economics changes considering the uncertainty of system construction costs and fuel cost have also been investigated in the paper.
For the optimum design of photovoltaic power generation systems, it is important to estimate their annual electric power output. Annual electric power output of photovoltaic arrays are affected by the environmental factors such as cell temperature, intensity and spectral distribution of solar radiation. But we don't keep the annual data for spectral distribution of solar radiation at all the districts in Japan In this study, we propose a theoretical method to estimate the spectral distribution of solar radiation by using air mass, clear index and precipitation. The calculated values of seasonal output for the photovoltaic modules are compared with the experimental ones measured in our campus. Moreover we calculate the electric output of photovoltaic systems by using the proposed method with the environmental factors at 14 districts in Japan. As a result, it is found from viewpoint of annual electric power output that photovoltaic power generation systems constructed by amorphous silicon solar cells are effective in southern part of Japan, on the other hand, polycrystalline silicon solar cells are useful in northern part of Japan.
The surplus electricity generated in the residential photovoltaic (PV) system is sold by a customer and purchased by a utility. So the purchase and the sale prices influence the diffusion of PV system. In this paper, the purchase price and the sale price are calculated from the utility and the customer sides, respectively. Parameters are future years (2005, 2015, 2025) and the diffusion ratio of PV system (0, 2, 4, 6, 8, 10%). First, from viewpoint of the utility side, the optimum mix of electric generation sources and the generation curves are calculated using the linear programming method. The result leads to the purchase price at which the utility makes a profit. A representative result shows the purchase price has to be lower than 8.2 yen/kWh in case of the diffusion ratio being 10% and the year being 2025. Next, from viewpoint of the customer side, the PV system cost and the electricity charge are calculated supposing that the PV system cost decreases with increasing of the annual productivity of PV module and the existing electric charge system remains to 2025. The result leads to the sale price at which the customer makes a profit. A representative results show that the sale price has to be higher than 13.8 yen/kWh at the same parameter as above. It is concluded that a carbon or environmental taxes are necessary to fill up this big gap between the purchase (utility) and the sale (customer) prices.
It is important to power system designers and operators to grasp conditions of a power system operated. In order to grasp the power system condition, the new method using a Superconducting Magnetic Energy Storage (SMES) has been proposed. This method is one of new usage of SMES. Since SMES is a controllable power source with quick response, it can give a power disturbances for power systems with arbitrary patterns. The transient response occurred by the SMES power disturbance is analyzed by FFT. From the peak of the power spectrum, the natural frequency of the power system is pointed out. In the conventional method for diagnosis of the power system by SMES, the power disturbance is a continuous sinusoidal oscillation. In this paper, we propose to use the one-period sinusoidal wave as the power disturbance. This method is superior because its analyzed data almost comes from the natural oscillation and the disturbance periodicity is not appeared in the analyzed power spectrum. In this paper, we make clear that the natural frequency of power systems can be measured by use of the proposed one-period sinusoidal SMES oscillation.
Pumped hydro storage power stations have been developed as a peaking and reserve power plant. As capacity of pumped storage stations recently tend to get larger compared with their reservoir capacity, their maximum duration of full-power operation becomes shorter and availability of pumping energy sometimes presents difficulties. This increases possibility of reducing effective power of pumped storage in case of stringent supply-demand-balance in a power system. Although many studies have examined a role of pumped storage in generation system, few studies have explicitly dealt with the reduction. This paper proposes a new linear programming model that incorporates the reduction of effective power of pumped storage. The model, by employing hypothetical daily load curves and dispatching load to the curves, simply takes the reduction into account. The model also includes LNG combined cycle power generation plants that are intensively developed in these years. The developed model is applied to a model system. The sample study reveals that the reduction of effective power considerably varies among seasons and the reduction highly affects optimal generation mix-optimal share of pumped storage.
The combination of a Superconducting Magnetic Energy Storage (SMES) and High Speed Phase Shifter is considered to be a unified power system controller. The combined system has been named as SuperSMES from the viewpoint of its capability. A new control scheme of the SuperSMES for the power system stabilization with a simple control sequence by using both generator signals or local signals has been proposed. This paper shows the results of a new stabilizing control scheme of the SuperSMES for power system stabilization based on experimental results with a 10kJ superconducting magnet and 10kVA model transmission line.
Detection signals obtained under the application of commercial AC voltage can be explained by two kinds of current mode, namely generation mode which is correspond to void discharge and transmission mode which is composed of conductive path and signal source contained in the line voltage of the operating cables. By the circuit restrictions of cable shielding layer capacitor earthing and also to avoid the effect of DC stray current, detection frequency for in-service measurement needed to select lower than AC frequency and also higher than DC. At the water tree deteriorated cable specimen, 1Hz (lower than commercial AC voltage) signal was obtained by transmission mode under the operating voltage stress. Furthermore, existence of the generation mode was suggested by the dried water tree deteriorated cables, because the micro discharge seemed to be existed in the non-conductive dried micro void of deteriorated cables.
Experiments and analysis were carried out on the wear due to arcing on copper electrodes in air over a range of average currents from 100 to 1000 A in AC 60Hz. The experiments showed that the anode wear is larger than the cathode wear, and average arc current influences the cathode wear more strongly than the anode wear. The experiments also showed that the wear of a pair of electrodes is proportional to the power of 1.67th of the average arc current. These results were analyzed by the use of an energy balance equation at the cathode and anode. The analysis revealed the following. The energy loss due to electron emission, and the large heat conduction loss causes little cathode wear. As the average arc current increases, the ratio of the energy loss, except for the vaporization energy, to the input energy at the cathode increases considerably. This leads to the strong influence of the arc current on the cathode wear.
Imaging of lightning channel in three dimensions is realized by UHF interferometer observation at two stations. These interferometers are operating at the center frequency of 327MHz and the time resolution of 1μs. The three dimensional observation is carried out at Darwin, Australia in November 1996 and we perform accurate calibration in order to obtain clear lightning images in three dimensions. This paper shows imaging results of progression of a negative leader and subsequent dart leaders of multiple-stroke flashes. This paper presents case study of multiple-stroke flashes and comparative study between discrete and hybrid flashes. The analysis shows the evidence that the system is able to locate lightning channels in three dimensions and the advantage of three dimensional analysis using interferometers.
Interferometric observations of cloud-to-ground flash in Darwin have been analyzed to investigate some features of the lightning. Our study focuses a comparison between multipoint and multiple negative cloud-to-ground flashes. We estimate the speed of leaders with submillisecond resolution for both multipoint and multiple strokes. The leader that precedes first stroke for mutiple flash progresses in a stepped fashion, and its behavior seems to be similar to that for multipoint flash. The speed of the leader is estimated at the mean value to 105m/s order, and the mean step length is found to be 96 meter with a mean pause time of 73 microsecond. The running time of the leader analyzed here takes the mean value of 89 microsecond. The duration of UHF radiation of leader which traces the former channel ranges from 0.2 to 55.3 millisecond with a mean of 7.5 millisecond. To the contrary, those preceding multipoint strokes ranges 21.1 to 90.6 millisecond with a mean value of 47.5 millisecond. The time interval between strokes which strike the same point as the former stroke ranges from 22.5 to 330.6 millisecond with a mean of 75.1 millisecond, and those for multipoint strokes ranges from 55.6 to 633.7 millisecond with a mean of 149.1 millisecond. All of the leaders preceding multipoint strokes starts at the same region inside the cloud.
The response of an impulse voltage measuring system is numerically analyzed by extensively using the Numerical Electromagnetic Code (NEC-2). The dynamic electromagnetic field around an impulse voltage measuring system including a resistor divider and a lead line is calculated to produce the output voltage waveform of the divider. The accuracy of the calculation is proved satisfactory by comparing the calculated waveforms with measured ones. The influencing factors of a measuring system on the USR (Unit Step Response) parameters are discussed based on the results of the numerical analysis.
A method using steady-state solution is proposed for theoretical calculation of lightning overvoltages at a substation. The system condition which has maximum overvoltages at a substation is estimated from the frequency responses of lightning surges entering a substation and substation impedance applying this method. This paper describes the investigation of phenomenon of the resonant, oscillating overvoltage in a transformer winding which is occurred in recent years using steady-state calculation. From tie results, it is found that this phenomenon occurred when the component of overvoltages at transformer terminal, which is coincident of tap winding frequency, is high. And the system condition which has large overvoltages depends on the length of each element of power system equipment which has periodical function. The calculated results by this method agree reasonably with the transient solutions calculated by the EMTP. The method is quite useful for lightning surge analysis which needs many calculations such as the study of relation between the length of power system equipment and an overvoltage generated.
Lightning strikes have been observed to study the lightning phenomena particular to a system in which both UHV designed and 500kV designed transmission lines coexist. This observation covers the lightning phenomena through lightning strikes, surge propagation on transmission lines and generation of overvoltages in substations. This paper describes the study of the lightning phenomenon of a shielding failure to a UHV designed line and the analysis result by the EMTP, which are based on the observation result of the lightning surge at a substation.
As an analogy to ultrasonic-irradiating promotion of plating, it is possible to lessen the activation and concentration polarization in electrochemical process by ultrasonic irradiation. We measured polarizations and current-voltage characteristics, irradiating ultrasonic on polymer electrolyte fuel cell, solid polymer water electrolysis cell, and Lithium ion secondary battery. It was shown experimentally that the ultrasonic effect appeared only in Lithium ion secondary battery, and that its activation polarization decreased by only 4% when the power supplied to an ultrasonic generator was the same order of magnitude as that of secondary battery. This ultrasonic effect decreased when the battery temperature increased.