Kazuhiro Soga

Influence of heat island phenomenon on building heat load

Urbanization causes the so-called heat island phenomenon that raises urban atmospheric temperature higher than that in the suburbs. The phenomenon leads to a decrease in heating load and an increase in cooling load in the urban buildings. In this paper, the effect of the heat island phenomenon on the heat load of buildings was analysed by year-to-year changes in the heat load both in the urban and suburban areas. Tokyo was selected as the target urban area and Choshi, as a less urbanized city, among 30 stations located in a range of about 100 km both east-west and north-south centering on Tokyo. Investigation on the relationship between the changes in heat load during the past 100 years confirmed that • The heating load of Choshi has decreased about 20% since 1900, whereas the heating load of Tokyo has decreased about 40% in the same period of time. Also • The cooling load of Tokyo has increased about 20% since 1900, but the similar increase can be seen in that of Choshi.

A Simplified Calculation Method for Seasonal Accumulated Solar Heat Gain through Windows

Abstract To estimate the energy performance of windows, the seasonal accumulated solar heat gain through the windows has to be calculated. A simplified method for calculating seasonal accumulated solar heat gain through windows with arbitrary azimuth and tilt angle is proposed. The method was tested using weather data from seven locations in Japan. The proposed simplified method provided good simulations of detailed hourly calculations.

Influences of Solar Incident Angle on Power Generation Efficiency of PV Modules under Field Conditions

In this report, we examined influences of solar incident angle on the power generation efficiency of photovoltaic (PV) modules based on a measurement, during winter, at Kagoshima in Japan (31.570°N, 130.545°E). It was indicated that the power generation efficiency of PV modules deteriorates with time depending on the solar incident angle, and that there are cases where the power generation efficiency sharply drops if the incident angle exceeds 60° and the reflectance of cover glass exceeds 0.2. Such drop of power generation efficiency dependent on incident angle clearly appears at clear time when the proportion of direct components of solar radiation increases. Furthermore, it was pointed out that the average value of power generating efficiency during winter including all weather conditions produces differences of 10% or so, depending on the difference of average value during the period of incident angle.