Sanshiro Yamanaka

Simulation of I–V characteristics of a PV module with shaded PV cells

The authors are studying a diagnostic method of a PV power generating system. We consider that the change of I–V characteristics can be utilized for the diagnosis. However, the report on the change of I–V characteristics is very little. In this paper, we investigate the relation between the output lowering due to shaded PV cells and the change of I–V characteristics, utilizing the computer simulation. It was proven from the simulation that I–V characteristics are changed by the condition of the shadow, which covered the module. The change of I–V characteristics of a PV module with shaded PV cells is discussed by the shift of the avalanche breakdown voltage of shaded PV cells.

Effect of filler concentration on electrical conductivity and ultralow-frequency dielectric properties

The effect of filler concentration on the dielectric properties in the ultralow-frequency region and on the electrical conductivity was studied for ethylene propylene rubber. First, we investigated the relation between the electrical conductivity and filler concentration: as the volume fraction of fillers q/sub a/ increased, the conductivity decreased in the low filler concentration region but increased abruptly in the high filler concentration region. The decrease and increase in conductivity can be explained with the action of carrier traps at the interface between EPR and fillers and with the formation of highly conductive paths of filler across the sample, respectively. Secondly, we studied the dielectric properties in the ultralow-frequency region which was obtained from the discharge current. As q/sub a/ increased, the relaxation time decreased in the low filler concentration region and then rose in the high filler concentration region. The polarization in the high filler concentration region can be explained by two-layer interfacial polarization between filler and rubber. >

Improvement of Dielectric Properties of Plasma Polymerized Styrene with Hydrogen Plasma Treatment

Capacitance and dielectric loss tangent of plasma polymerized styrene films are obtained as a function of temperature. The stability of these films is investigated with heating in a vacuum and in air. It was found that the hydrogen plasma treatment is effective in improving and stabilizing the dielectric properties of the plasma polymerized styrene films.

Diagnosis of a Power Output Lowering of PV Array with a (-dI/dV)-V Characteristic

It is reported that the volume of an estimated PV system installations in Japan must be set at about 4.82 [GW] up to 2010. As a result, it seems that PV systems must spread in the future in a general household, and therefore the maintenance and management of PV systems must become important keeping to the normal output performance of a PV system. However, it will be very difficult to locate the lowering factors to affect to output performance of the PV system installed in a residential rooftop. Besides, even if a cause of the output lowering of the PV system was found more, it will be very difficult to remove these. The authors paid attention to that shape of an I-V characteristic of a PV system changed by the output lowering caused by loss factors such as deterioration of a PV module, a shadow, and so on, and study the method to simply and automatically evaluate the output lowering of a PV system. In this paper, the (dI/dV)-V characteristic to be obtained from the I-V characteristic of a PV array is adopted as the standard characteristic for the automatic analysis. The (dI/dV)-V characteristic was simulated with an abnormal I-V characteristic of PV array covered in a shadow partially. A performance fall of PV array to be caused by a partial shadow is evaluated by an appearance of a peak of the (dI/dV)-V characteristic, and an appearance position of this peak changes by a condition of a shadow. From these results, it became clear that an appearance of a peak of a (dI/dV)-V characteristic must be means to be effective to diagnose the output lowering of a PV system

Ultralow-frequency dielectric properties of EPR with filler

The dielectric properties in the ultralow-frequency regions of ethylene propylene rubber with fillers are studied. These are important materials, especially for electrical cables and wires in nuclear power generating stations. The dielectric parameters alpha , tau /sub o/, and in /sub ro/- in /sub r infinity / in the Cole-Cole equation are obtained by fitting the theoretical curve with the experimental results on the discharge current. The present polarization is caused by the interfacial polarization between EPR and the fillers. Assuming that part of the filler clusters and takes the form of spheroids, the relaxation time is correlated with the shape of the spheroid. The observed distribution of relaxation times is interpreted as being due to the dispersion of various shapes of spheroids. As the concentration of filler increases in the low-concentration region, the characteristic relaxation time tau /sub o/ decreases. The decrement of tau /sub o/ can be understood with the variation of the cluster shape with the filler concentration. >

Diagnostic method of performance of a PV module with estimated power output in considering four loss factors

Recently, PV systems are rapidly spreading. It is necessary to establish a diagnostic method for maintenance of the PV systems. The authors are studying diagnostic methods of PV systems. Even if a PV module is normally operated, the generated power is less than the rated power. It means that the normal PV module has some kinds of loss in the generated power. These losses are caused by irradiance, reduction of sunlight transmittance on glass of module, temperature and series resistance. The generated power can be estimated by considering these four kinds of loss. The estimated power is calculated by subtracting these power losses from the rated line. As the results, the diagnostic method is devised by using the estimated power. And it is clear that the method can diagnose bit degradation of generated power on the module.

Loss factors affecting power generation efficiency of a PV module

The authors are studying the diagnostic method of a PV system. In order to diagnose a PV system in detail, it is necessary to separate the loss factors affecting power generation efficiency. In this paper, we are investigating the influence of the solar irradiance and the incident angle on power generation efficiency of the PV module installed at tilt angle of 90 degree and azimuth angle of east and west, respectively. Especially, the influence of the incident angle on power generation efficiency is estimated in detail by separating direct and diffuse component of solar irradiance. We investigate the comparison between the measurement and the calculation results related to the change of power generation efficiency with time. The calculation value considering solar irradiance and incident angle of direct and diffuse solar irradiance almost corresponded to measurement value. As a result, it is clear that the change of power generation efficiency with time can be estimated by separating the influence of solar irradiance and incident angle of direct and diffuse solar irradiance and considering these loss factors.

Electrical properties of EPR with filler

The authors have investigated the electrical properties, especially the conductivity and the dielectric characteristics in the ultraflow-frequency region of EPR with hard clay. They first investigated the relation between the electrical conductivity and the content of filler. It was found that, as the content of filler was increased, the conductivity decreased initially and then increased abruptly. The authors have explained the decrease and increase in conductivity by the action of carrier traps at the interface between the EPR and filler and the formation of highly conductive paths of the filler between the electrodes, respectively. Secondly, the authors studied the dielectric properties in the ultralow-frequency region which was obtained from the discharge current. The observed variation of the relaxation time with the filler can be interpreted as being due to the variation of cluster shapes in the composite materials.<<ETX>>

Residual Voltage in Low-Density Polyethylene Film Containing Antioxidant

A polarity effect of the residual voltage was found on applying a high bias voltage of more than 1000 V to a 30 µm-thick low-density polyethylene film containing antioxidant. It is shown in this report from ESCA data and surface treatment that the antioxidant bleeds out onto the outer surface when films in the form of two laminated layers are stored. The injected space charges are also estimated from the isothermal depolarization current and TSC measurements under a collecting voltage. It is further demonstrated that the polarity effect can be consistently understood by assuming that the lowering of the blocking barrier by the antioxidant bled out to the surface is more effective in the discharging process than in the charging process.

Thermally stimulated currents of ethylene-propylene rubber with filler

We are studying the effect of filler on the electrical properties of Ethylene-Propylene Rubber (EPR). In this paper we have measured the Thermally Stimulated Currents (TSC) of EPR with hard clay to investigate the distribution of the relaxation time, and obtained the variation of TSC curve with the temperature T/sub b/ at which the sample is polarized. When the temperature T/sub b/ is lower than room temperature, the TSC curve has only one peak. But for higher values of T/sub b/, the TSC curve exhibits three peaks (P/sub H/, P/sub M/, and P/sub L/ peaks in the order of descending temperature). Assuming two layer interfacial polarization between rubber and filler having a distributed thickness of rubber layer, we have calculated the relation between the TSC curve and the polarizing temperature T/sub b/. From these calculation we think that the P/sub M/ peak is caused by two layer interfacial polarization having a distributed thickness of rubber layer.