Analysis of Energy-efficient Measures and Renewable Energy Technologies towards Net Zero Energy Building Designs

There is a growing concern about global energy consumption and its implications for the environment. Recently, the concept of net zero energy buildings (NZEB) has become an international goal to help alleviate the depletion of energy sources and the deterioration of the environment. The design strategies for a NZEB generally involve the minimization of energy use through more energy-efficient measures and the generation of renewable energy (RE) to meet the minimal energy needs. In subtropical Hong Kong, most of the energy used in commercial buildings is used to create a thermally and visually comfortable environment, specifically air conditioning and electric lighting. These two areas account for around three-quarters of most buildings’ total electricity consumption and therefore air conditioning and electric lighting are the two target areas for electricity savings in commercial buildings. Solar and wind energy have been identified as having the potential to generate sustainable, inexhaustible, clean, and safe energy in Hong Kong on a wide-scale. Strategies to limit summer heat gain and winter heat loss through the building envelope include thermal insulation, thermal mass, window/glazing, green roofs, raising the thermostat settings during the hot summer, and using natural ventilation in circulation areas. Some of the energy-efficient measures for reducing cooling loads are variable air volume air-conditioning systems, variable speed drives for fans and pumps, and high coefficient of performance chiller plants. Using energy-efficient light fittings with dimming controls and proper daylighting schemes can reduce the energy used in lighting. Natural light can help reduce the electrical demand and the sensible cooling load from electric lighting. For high-rise commercial buildings with limited roof areas, semi-transparent and opaque building-integrated photovoltaics (BIPV), small sun-tracking PV products, and micro wind turbines are appropriate RE facilities. Semi-transparent BIPV panels can be used as glazing systems that provide electricity, reduce solar heat gain, and enhance daylighting schemes. Solar trackers can turn the PV panels so that they always face the sun and receive the largest solar irradiance, thus maximizing the generation of electricity. Micro wind turbines installed in naturally ventilated areas can enhance overall performance. The proposed study will examine the use of all of these energy-efficient measures and RE facilities in creating NZEBs. The study will include field measurements, numerical approaches, and computer simulations. The benefits in terms of energy, the environment, and costs will be investigated. The findings will contribute to the establishment of a sustainable, healthy, comfort, and livable urban environment.