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Solar cells are well known as devices for sustainable electric energy generation. Nowadays the potential induced degradation has been brought up as an obstacle problem for practical use. In order to determine the cause of this kind of degradation, numerical simulation by a finite difference time domain method has been performed for computational electromagnetics in the case that the thunder attacks the solar modules. The results show that the dielectric breakdown in the glass covered over the solar cells triggered by the thunderstroke is critical. So it is helpful to protect the dielectric breakdown in the glass from the thunderstroke.

Solar cells are now widely used as a clean method for electric energy generation. Among various type of solar cells, we compared the ability between amorphous and tandem (amorphous and polycrystalline) silicon solar cells by means of simultaneous running test. This kind of comparison is of importance practically, because the comparison of only inherent characteristics cannot include environmental parameters such as temperature totally. It was concluded that both types of solar cells provided almost the same energy for one year. The amorphous silicon solar cell provided more energy in summer while the tandem solar cell was advantageous in winter. It is due to the fact that the decrease in energy conversion at the higher cell temperature is more noticeable in tandem solar cells.

Generally MPPT control (maximum power point tracking) is adopted to control of a thermoelectric generator. However, in the case of generation by use of a heat accumulator MPPT control cannot obtain maximum whole electrical output during the operation period. This is because the amount of heat stored in a heat accumulator is limited and easy to be exhausted rapidly by MPPT. Therefore MEPT (Maximum Efficiency Point Tracking) control should be developed to obtain maximum power from limited heat stored in the heat accumulator. When thermoelectric generator is used for waste heat recovery, conversion efficiency is quite difficult to be measured. This is due to time delay between the change of temperature profile in the thermoelectric generator and the change of heat medium temperature. Decrease of output current is desired to enlarge output because decrease of current decreases Peltier heat and improves efficiency of heat recovery. The experimental results indicate that current fluctuated by MPPT control causes loss of power output. We proposed the optimal control in which current is 10% smaller than one of MPPT control and evaluated it experimentally. We call this control scheme MEPT control. In this evaluation 500 W class thermoelectric generator, latent heat accumulator and the test facilities included 30 kW electric heater are utilized. Experimental result shows MEPT control exceeds MPPT in total electricity recovered from heat accumulator.

Processes to produce hydrogen from solar photovoltaic (PV)-powered water electrolysis using solid polymer electrolysis (SPE) are reported. An alternative control of maximum power point tracking (MPPT) in the PV-SPE system based on the maximum current searching methods has been designed and implemented. Based on the characteristics of voltage–current and theoretical analysis of SPE, it can be shown that the tracking of the maximum current output of DC–DC converter in SPE side will track the MPPT of photovoltaic panel simultaneously. This method uses a proportional integrator controller to control the duty factor of DC–DC converter with pulse-width modulator (PWM). The MPPT performance and hydrogen production performance of this method have been evaluated and discussed based on the results of the experiment.

Bi-Sb alloys were grown by means of an electrodeposition method using Cu electrodes. The alloys were studied with the help of an x-ray diffractometer and an electron probe microanalysis. The both investigations have shown no trace of Cu in the obtained alloys. It can be concluded that Cu electrodes can be used for the deposition of Bi-Sb alloys; which results in an advantage of availability of the electrode.

The capability of high-speed countercurrent chromatography (HSCCC) has been investigated for enrichment and determination of metal ions at trace levels. Separation of selected divalent metal ions was performed using a small coiled column. A hexane solution of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPA) was employed as the stationary phase. Loaded divalent metal ions such as Ni, Co, Cu, and Zn were chromatographically eluted in the order of increasing extractability by passing a mobile phase buffered at a desired pH. Individual metal ions showed good linearity between concentrations and chromatographic peak areas of the absorbance, as detected by postcolumn reaction with 4-(2-pyridylazo)resorcinol (PAR). Metal ions enriched into the stationary phase from a sample solution were separated into individual metal ions. The trace quantity of zinc in natural mineral water was determined by enrichment separation through an HSCCC column.

A thermoelectric generator has been manufactured and evaluated for the purpose that the behavior of heat conduction and power generating performance can be clarified when the thermoelectric generator is powered by a high-temperature heat transfer medium oil over 500 K. The thermoelectric generator needs a compression fitting mechanism which holds heat sinks and thermoelectric generating modules so tight that desirable heat conduction can be maintained for thousands of heat cycles. The pressure required for the compression fitting mechanism was experimentally investigated with a trial manufactured thermoelectric generator. As an experimental result the compression fitting mechanism of the modules requires 0.28 MPa compressive load, which is 80% less than the recommended value by one of the module manufacturers. Electricity obtained by the trially manufactured thermoelectric generator with bismuth telluride-based modules increases in proportion to the square of the logarithmic mean temperature difference between the heat transfer medium oil and cooling water and attains 165 W at the logarithmic temperature difference of 180 K. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(1): 36–44, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10042

Separation of selected lanthanoid elements was performed by high-speed countercurrent chromatography (CCC) equipped with a small coiled column of a 10 cm3 capacity. A hexane solution of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPA) was retained in the tubing column as the stationary phase. The stationary phase retention increased with increasing rotational speed and with decreasing flow rate of the aqueous mobile phase. Mixtures of lanthanoids (Gd, Tb and Dy) were chromatographically eluted in the increasing order of extractability by introducing the buffered mobile phase, and excellent separation of lanthanoids was achieved. Lanthanoids (Sm through Er) and yttrium were simultaneously enriched in the stationary phase from a large volume of a sample solution, and then separated from each other with reasonable resolution.

An acidic organophosphorus compound, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPA), has been applied to reversed-phase high-performance liquid chromatography (RP-HPLC). The reversed-phase stationary phase was dynamically modified with EHPA by flowing the mobile phase of an acetone-water mixture containing the extracting reagent. The retention of lanthanoid elements was widely varied by changing the conditions of the mobile phase, i.e., the pH, the EHPA concentration and the acetone content. The selectivity of EHPA is well reflected to the chromatographic systems, and a precise separation of lanthanoid elements was achieved with sufficient resolution. The determination of Sm was examined in the presence of a large amount of Nd. A linear calibration graph was obtained for Sm at the level of 10-7 mol dm-3, in the presence of 1 × 10-4 mol dm-3 of Nd.

The selective transport of Am across a supported liquid membrane (SLM) has been investigated by using bis (2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) as a mobile carrier. This extractant containing soft donor atoms exhibits strong affinity for actinoids, giving a large separation factor between trivalent Am and Eu. Separation of Am from Eu was achieved by an SLM containing highly purified Cyanex 301. Americium was preferentially transported across the SLM and concentrated in the product solution, while most of Eu remained in the feed solution.

The selective transport of yttrium(III) in the presence of iron(III) through a supported liquid membrane (SLM) has been investigated by using di(2-ethylhexyl)phosphoric acid (DEHPA) as a mobile carrier. Yttrium(III) with fast kinetics was preferentially transported from the feed solution of dilute acid into the product solution of 1M H2SO4, while most of iron(III) with slow kinetics remained in the feed solution. The effective separation of yttrium(III) from a large amount of iron(III) was accomplished by the selective transport of yttrium(III) through the SLM.

Separation of selected lanthanoid elements was performed by high speed countercurrent chromatography (CCC) employing a support–free stationary phase of 2–ethylhexylphosphonic acid mono–2–ethylhexyl ester (EHPA) in toluene. Middle lanthanoids (Sm, Eu, Gd, Tb, Dy) were chromatographically eluted in their increasing order of extractability by passing the aqueous mobile phase of pH buffers. The mixtures of lanthanoid elements of different concentrations were isolated into individual elements of high purity by one–step chromatographic operation.

Preferential solid phase extraction of ultratrace metal chelate from the excess of its ligand has been succeeded in the case of cobalt, 4-(2-pyridylazo)resorcinol (PAR), ODS-Silica, and H2O system, applying the reverse order of them found in reversed-phase HPLC with aqueous methanol and ODS-SiO2. This finding makes it possible to concentrate the 1-ppt level of cobalt chelate in the presence of excess PAR from aqueous samples using kinetically selective HPLC.