Renewable energy resources are known to have two critical problems—fluctuation and low density. The authors have already demonstrated the worldwide potential of wind energy within a previous study. In this study, we describe the problem of the fluctuation of renewable resources and its solution. The authors applied “system energy technology” to renewable resources as a relatively long-term solution to the fluctuation problem. System energy technology is a concept for producing new value without new development and it was named by one of the authors of this paper, Prof. Masaru Hirata. This concept is adapted to renewable resources such as a combination of solar and wind energies. The output, which is transformed into hydrogen, is estimated for three different cases—1 kW wind turbine, 1 kW solar cell, and a combination of both in order to study the effect of combining the two resources. The computation is carried out for 840 AMeDAS sites in Japan. The authors observed that the effect of combination is particularly strong in the area along the sea of Japan. In these areas, the monthly fluctuation in the power supply could be reduced by the combined system. On the other hand, the daily output of renewable energy varies. In order to solve this problem, the authors propose that the electric output should be changed to hydrogen. This system is called as the Hythane (hydrogen + methane) pipelines. The authors will discuss the Hythane pipeline systems in the following system study.

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According to the third conference of parties (COP3), Japan has set a target of reducing greenhouse gas emissions by 6% by the year 2010. Cogeneration system is a recently potent method which its environmental benefits, through the highly efficient utilization of fuel that is related to reduction emissions. The particular purpose of this paper is to support the selection of cogeneration technologies by acquiring the optimal useful thermal energy and electrical power from system with well-efficiency balance method and fuel saving approaching method. When a micro gas turbine (MGT) is operated under ambient condition, the discharged hot gases from the MGT may be expanded at its exhaust stage and cooled by an exhaust heat exchanger which composes with a single stage absorption heat exchanger. The performance and annual total fuel saving amount of cogeneration plant will be investigated and compared with separated production of heat and power system. Eventually, this cogeneration plant will be reduced the fuel consumption rate in operation that will be also reduced the emissions and fuel cost when the system will gain highly efficiency of thermal energy and electrical power.

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A neutron radiography three-dimensional computed tomography (NR3DCT) system was developed to visualize the void fraction distribution of boiling flow in tight lattice heated-rod bundles. This paper chiefly reports on the data processing and the error estimation method of NR3DCT. Practical γ-ray noise reduction and image correction techniques were studied to improve the reliability of the experimental data. Using the system and a directly heated 14-rod bundle test section, the behavior of boiling flow in a tight lattice rod bundle was clearly visualized. The effect of each data processing step on the result was also discussed. By this development, the three-dimensional vapor distribution of boiling flow in a heated bundle is made clear, and void fraction databases can be provided for verification of a thermal-hydraulic simulation code.

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Three-dimensional (3D) void fraction distributions in a tight-lattice of heated 7- or 14-rod bundles were measured using 3D neutron tomography. The distribution was also studied parametrically from the thermal-hydraulic point of view in order to elucidate boiling phenomena in a fuel assembly of the FLWR which is being developed as an advanced BWR-type reactor. 7-rod tests were carried out to obtain high void fraction data. 14-rod tests were conducted for visualization and discussion of the 3D distribution extending from the vapor generation region to the high void fraction region at one time. Experimental data were obtained under atmospheric pressure with mass velocity, heater power and inlet quality as the test parameters. It was found from the visualization of data that the void fraction at the channel center became higher than that at the periphery, high void fraction spots appeared in narrow regions at the inlet, and a so-called 'vapor chimney' was generated at the center of a subchannel.

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According to the third conference of parties (COP3), Japan has set a target of reducing greenhouse gas emissions by 6% by the year 2010. Many believe that the bulk utilization of fossil fuel influences to the damaging environmental effect. The objective of this paper is to propose an effective method for this goad which is possible to clarify a noticeable utilization of renewable fuel in a micro gas turbine cogeneration system in cold region. Moreover, analysis of renewable fuel, biogas production indicates that production amount becomes largest in hot season, while the total heat energy demand is lowest on during three years. Biogas storage is also adapted for the delay between peak energy supply and demand. Biogas hydrate formation is examined by resource from laboratory experiments and simulation of integration into an existing cogeneration arrangement. The proposed system can be successfully supported the use and reuse of renewable fuel for providing to substantial emission and clean development mechanism for reducing greenhouse gas emission.

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An actual renewable energy house, equipped with a geothermal heat pump (GHP)-powered floor heating system was investigated and analyzed. Daily annual monitoring between February 2005 ∼ February 2006 and real-time continuous system monitoring within selected periods during the winter season between November 2006 ∼ January 2007, were carried out in order to establish the actual performance of the system. It emerged that the GHP-powered floor heating system is sufficient for space heating, with the maintenance of near-uniform room temperatures even during the coldest days in a very cold region like Hokkaido, Japan. About 37% average of the floor heat losses are recoverable and more than 50% of the ventilation heat losses are recovered due to various innovative energy-saving techniques built into the system. Annual heat loss from the house estimated by the numerical simulation showed good agreement with the measured annual thermal demand for room heating. The simulation also estimated that annual running costs and Green House Gas (GHG) emissions reductions of 47% and 49% respectively, can be realized with this system compared to an equivalent conventional system. A detailed cost analysis for the GHP-only system revealed that if the cost of fuel oil increases by about 50% from the current value of ¥80/L, then the payback period for a GHP-powered renewable energy system is about 14 years. This payback period reduces to about 10 years if 30% of the initial cost of the GHP-powered system is externally funded.

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