Photovoltaic power generation system is attracting attention as a clean and environmentally friendly power generation and has been applied to many buildings. On one hand, various researches into its power generation efficiency have been practically conducted. On the other hand, its relevancy to air-conditioning power consumption has not been so much verified yet. It would be necessary not only to examine the system itself but also comprehensively to evaluate it in terms of reduction in air-conditioning power consumption, power load shifting, and so on. In this thesis we have discussed the effects the system has on air-conditioning load in a building model equipped with photovoltaic power generation system. We have studied air-conditioning load reduction and peak shift resulting from solar insolation shielding brought by photovoltaic power generation panels, and verified load reduction effects produced concurrently by photovoltaic power generation panels.

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New type of storage electric water heater has been developing these a few years, which supplies hot water through the heat exchanger located in a vacuumed steam space. Although the structure of this type of water heater is durable and profitable to keep the sanitation clear, the high level of noise has occurred when the low temperature boiler water has been heated up. The noise reducing methods have been expected strongly, however the influence of boiling behavior in the vacuumed boiler body on the above big noise have not been reported enough. Therefore, in this report, the causal relationship between the boiling behavior and the noise was made clear and the following indexes were proposed as the noise reducing methods. (1) The structure of boiler body with decreasing the water head forced on a heating surface. (2) The shape of heating surface to make the vapor bubble minute. (3) The installation of the control mechanism near around the heating surface to control the degree of subcooling sectionally.

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Flow and temperature distributions were measured for natural convection in a rectangular enclosure filled with water. One of the vertical walls of the test space was cooled to keep the surface temperature almost constant and the bottom wall surface was uniformly heated. Assuming a scale model of a residential room with a floor heating system, experiments were performed at the Rayleigh Number 1.8×10^<10>〜3.9×10^<10>. PTV (Particle Tracking Velocimetry) method was applied to measure very slow flow fields, and a thermocouple device was employed for temperature field measurements. At near wall regions, detailed data were obtained mainly in a center vertical plane under several heating conditions. These data may be applicable to validate numerical methods for the numerical predictions of flow fields and thermal environments in floor heating rooms.

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One of the authors, of Kajima Corporation, began a long-term observational study in January 1993 as part of IDMP (International Daylight Measurement Programme) of CIE (Commission Internationale de l'Eclairage). The present comprehensive study provides information for interior design by determining correlations among external meteorological factors such as solar radiation, illuminance, luminance, night radiation, temperature, humidity, wind direction and wind velocity. This paper (Part 3) reports estimation of direct and diffuse solar radiation from measured global horizontal solar radiation obtained by using minute-by-minute data of solar radiation for the period of eight years through discussion by solar altitude, by cloud ratio and by cloud ratio in solar altitude.

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To evaluate cooling-heat-load in apartment houses, it is important to assume the application of Air-Conditioning by inhabitants. We studied on usage of cooling in apartment houses in Tsukaguchi, Hyogo-pref. First, We found 5 standard patterns of cooling time-zone from questionnaire collected from all houses. Then, by analysis of energy consumption of cooling in 9 selected houses, we found strong relation between cooling-application and outdoor-air-temperature, and usually cooling is applied when outdoor air-temperature is over 24-27℃. Also there are two time zones on daily application, cooling-time-zone and no-cooling-time-zone. It might be useful to determine the condition of cooling application in simulating cooling-heat-load.

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The authors investigated latent heat storage by materials with phase change temperature of 60℃〜90℃ in order to utilize waste heat from modern urban energy supply systems. Here, they focused on a mixture of magnesium nitrate hexahydrate as a base material and magnesium chloride hexahydrate as an additive to modulate the melting point. Addition of 5〜10wt% of the latter resulted in a modulated melting point of about 80℃ and a heat of fusion of about 150kJ/kg. Increasing the mix ratio had little effect on heat of fusion, but allowed the melting point to be modulated to about 60℃. Repeated melting and solidification tests showed that the heat of fusion and melting point retained their original values even after 500 iterations. Heat charging and discharging experiments were done using a heat storage cistern with a vertical heat exchange unit. These showed that effective use of the phase change temperature region resulted in an available enthalpy of 2.0〜2.5 times that of water heat storage.

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Hybrid cooling system, utilizing wind induced cross ventilation and radiation cooling panel in an office setting is investigated. In order to reduce the energy use for HVAC system of buildings, utilization of wind induced cross ventilation seems to be promising. However, in hot and humid regions such as in Japan, utilization of natural ventilation only is not sufficient for exhausting the heat generated in offices. Some additional auxiliary cooling system is required. Here, a radiation cooling system and an under-floor air-conditioning system are compared. The characteristics of the indoor environment are examined using CFD (Computational Fluid Dynamics) simulation coupled with a radiation heat transfer simulation and with HVAC control in which the PMV value for the human model in the center of the room is controlled to attain the target value. The system is devised on an energy-saving strategy, which utilizes stratified room air with the vertical temperature gradient. The cooled air settles down within the lower part of the room while the hot and humid air passes through the upper region of the room, sweeping out the heat and contaminants generated indoors. The radiation panel cooling system is found to be more energy efficient and provide more thermal comfort than an under-floor air cooling system in the case of introducing natural ventilation in mild climate.

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This paper presents a feasibility study of a fresh air load reduction system by using an underground double floor space. The fresh air is introduced into the double slab space and pass the opening bored through footing beam. The air is cooled by the heat exchange with inside surface of the double slab space in summer, and heated in winter. Then the heat is transferred to the adjacent soil through foundation slab and wall and to the room just above the mat through floor slab. The initial cost of the system can be reduced, because it doesn't need a pipe or duct in the ground as does the cool-tube system. A simulation model based on the simple 2-dimensional heat conduction equation was developed to simulate characteristics and performances of system. Validity of thermal simulation model was confirmed by comparison with field measurement. Using this simulation model following three issues were examined. Firstly, three factors that have effect on the system performances were investigated. It was shown that almost same annual thermal performance was obtained regardless the depth of earth-tube (examined for 0.7, 1.4 and 2.8m of depth, these are considered as realistic depth for actual building). The difference of annual cooling/heating rate by changing the room temperature just above floor slab as realistic range was below 8%. As air velocity become faster (0.05〜0.5m/s), annual cooling/heating heat rate increase from 5GJ/year to 420GJ/year for effective heating surface of 35〜7000m^2. Secondly, effect of fresh air load reduction was investigated. It was confirmed that this system is very effective to reduce fresh air load at different air velocity and effective heating surface, by annual fresh air reduction rate in different air velocity is 0.6〜37% for effective heating surface 35〜7000m^2. Finally, method and chart for judgment of introducing this system by comparison with the performance of total enthalpy heat exchanger was shown.

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