C.L. Tsang

Long term ambient temperature analysis and energy use implications in Hong Kong

Abstract Climate change issues and building energy use implications in subtropical Hong Kong were examined. A total of 40 years (1961–2000) of measured hourly temperature data were gathered and analysed. Three different parameters were examined, namely mean temperature, cumulative frequency of occurrence and cooling degree days (CDD). It was found that there was an underlying trend of temperature rise in recent years. Such temperature increase tended to occur more frequently during the winter period and mid-season than the summer months. The slight increase in CDD during the last 20 years suggested that cooling requirements and, hence, energy use for air conditioning might be affected if the trend persisted. The frequency of occurrence analysis, however, revealed no significant changes in the outdoor design conditions, and peak building cooling loads were expected to remain unchanged. This paper presents the work and discusses the energy use implications.

Mixed-Valence CuIICuI15I17 Cluster Builds up a 3D Metal−Organic Framework with Paramagnetic and Thermochromic Characteristics

Four cubane-like Cu4I4 units are assembled around an iodine atom to form the giant, mixed-valent Cu(II)Cu(I)15I17 cluster. The Cu(II)Cu(I)15I17 cluster and a bipyrazole linker form a 3D open framework with paramagnetic and thermochromic properties. This paper also touches on the resemblance of this cluster to the self-similar object of a Sierpinski tetrahedron.

Sensitivity analysis of building energy use in different climates

Abstract Key design parameters (in terms of their influences on building energy consumption) through sensitivity analysis for fully air-conditioned office buildings in five cities (Harbin, Beijing, Shanghai, Kunming and Hong Kong) representing the five major climate zones (severe cold, cold, hot summer and cold winter, mild, and hot summer and warm winter) across China have been identified. These include: i) building envelope - window shading coefficient, window U-value and window-to-wall ratio; ii) internal load – equipment, lighting and occupancy; iii) HVAC system - outdoor fresh air, summer and winter thermostat set points, fan efficiency and fan static pressure; and iv) HVAC plant – chiller COP and boiler efficiency. The influence coefficient (IC, a ratio of the percentage change in computed output (building energy use) to the percentage change in input design parameter was used to indicate likely energy savings. For instance, Hong Kong has a lighting load IC of 0.359, suggesting that a 20% reduction (e.g. from 18 to 14.4 W/m 2 ) in lighting load could result in more than 7% reduction in the total building energy use. Furthermore, Hong Kong also has a summer thermostat set point IC of -1.131, suggesting that a 5% increase in the indoor temperature during the summer (e.g. from 26 to 27.3 o C) could result in about 6% energy savings. Given the growing awareness of adaptive thermal comfort, this could be a no-cost energy-efficient measure with great energy saving potential.