In order to resolve serious global environmental problems such as the greenhouse effect and acid rain, the key lies in the development of clean energies. Solar cell, which converts sunlight directly into electricity through the photovoltaic effect of semiconductors, is a key technology to overcome global environmental problems. This paper will review recent advances in solar cell technologies and their application technologies. Finally, future prospects are also reviewed, including a new global energy supply system called the GENESIS.
CRIEPI started the Ogachi project in the northern part of Japan in 1986, to determine the feasibility of an HDR geothermal power plant based on a multi-layer reservoir. During the past fifteen years we have developed technologies for surveying underground resources, forming multi-layer reservoirs and evaluating those reservoirs in a 1.7 billion yen study. Future plans include the development of a lifespan evaluation method, the improvement of production rates and finally, the establishment of an actual HDR power plant.
We investigated the relation between the noise form and the corrosion form by means of the potential noise measurement for the crevice corrosion, SCC and SCC in crevice of type 304 SS in 3.5% NaCl solution at 80°C. The generation mechanism of potential noise is discussed through the scratch test, where corrosion current and potential were measured simultaneously at various corrosion potential, paying attention to the noise direction which changed depending on the corrosion potential. The potential noise took place in the less noble direction at the higher corrosion potential and at the higher pH, while it took place in the noble direction at the lower corrosion potential. It was found that the form of potential noise depends on the corrosion potential and pH, instead of corrosion form. Experimental results indicated that this dependency was resulted from the increased current on the bare surface, which current could be anodic or cathodic depending on the corrosion potential and pH of test solution.
It has been known that the open-circuit potentials of stainless steels exposed to natural seawater are ennobled and that there is a possibility of ennoblement caused by hydrogen peroxide in biofilms formed on the surfaces of stainless steels. In this study, hydrogen peroxide detected in biofilms formed on SUS 316L specimens exposed to natural seawater for a month was resolved by means of enzyme (Catalase or Peroxidase), and the open-circuit potentials of the specimens were simultaneously measured for the purpose of explaining the relation between hydrogen peroxide and the ennoblement. The activity of the enzyme depends on the temperature and was controlled with adjusting the water temperature. At room temperature (23°C) the enzyme was inactive, and the open-circuit potentials of the specimens covered with biofilms formed by microorganisms in natural seawater reached approximately 0.6V vs. SHE. At the elevated water temperature (33°C) the enzyme was still more active than at room temperature, and the open-circuit potentials of the specimens in enzyme-dosed seawater fell to values equal to those without biofilms (0.2V vs. SHE), while those with no enzyme remained nobler than 0.5V vs. SHE. These results revealed that the enzyme resolved hydrogen peroxide in biofilms at 33°C and that the displacement of hydrogen peroxide reduced the open-circuit potentials to values as negative as those with no biofilm. The open-circuit potentials were ennobled again according to the drop in water temperature. This result indicated that experimental procedures mentioned above had influence on neither the activity of microorganisms nor the structure of biofilms, and that the microorganisms in the biofilms continued to produce hydrogen peroxide. Therefore, it is concluded that a major cause of the ennoblement induced by marine microorganisms is the presence of hydrogen peroxide in biofilms.
Direct observation of the specimen was applied on slow strain rate technique (SSRT) test in high-temperature water to investigate stress corrosion crack initiation of a stainless steel. Cracks larger than 100μm were detected by the optical behavior. The strain, at which a crack initiation was detected (crack initiation strain) decreased with decreased dissolved oxygen (DO) concentration, although the number of cracks did not have any correlation with DO concentration. The crack initiation strain was proportional to the maximum stress of the SSRT test specimen, but had no relationship with the IGSCC ratio on the fractured surface of the specimen. Thus the maximum stress was considered to be a good indicator of crack initiation.