**1. Introduction**

The saving and usage of green energy have been an emphasized research topic in various nations including Taiwan: an island nation located in a subtropical zone with 90% of the population living in regions with mean sea-level elevations of 400 m or lower. Limitations of some geological factors and climatic conditions cause a large population to be crowded in buildings that are concentrated in metropolitan areas.

Hence, large buildings cover by a glass shell which must rely heavily on artificial central air conditioning systems to resist outside heat loadings had become popular. Such a building takes a heavy toll on energy consumption. These buildings experience the problems of poor indoor air circulation, an inefficient cooling system in maintaining a comfortable indoor environment, as well as excessive energy consumption. Ninety-eight percent the energy consumed in Taiwan is imported.

Recent worldwide concerns on global warming and emphases on environmental protection have made it urgently necessary to develop sustainable energy sources for replacing conven‐ tional petroleum energy. Solar energy [1–4] is renewable, inexhaustible and abundant. The Earth receives an incredible supply of solar energy. It provides enough energy in one minute to supply the world's energy needs for one year [5]. Hence how to effectively use solar energy is becoming an active research topic in various nations today.

Solar energy can be utilized as either heat or light, with the majority of the research and application focusing on photoelectrical conversion of light into electricity. Using solar cells made of special materials of semi-conductance, the incident solar beam can be directly converted into electricity. The efficiency of electricity generation depends on the clarity of the solar panel. Additionally, storage of the electricity generated for later use must be considered.

In recent years, the booming semi-conductor industry had led to rapid advances in manufac‐ turing and implementing solar energy projects more cost effectively. Hence, solar energy is expected to be an important and a major source of energy in the future.

In Taiwan, central air conditioning systems are used in large buildings that accommodate offices, hotels, department stores and hospitals. These buildings, which are considered as "airconditioned buildings", have fixed office hours, similar occupants and application modes, and hence comparable heat generated from illumination and occupants. Additionally, these buildings adopt a glass shell to shield the structure so that natural lighting is available during daytime for saving electricity.

The expected benefits of using solar panels on buildings include lowering building costs, reducing energy consumption, and providing a more comfortable indoor environment. The greenhouse effectiveness in glass buildings is also applied in cold zones for saving heating energy. Additionally, large glass windows also provide excellent views for occupants to assist in improving their moods and work efficiency. Hence, in recent years, buildings covered in glass panels are becoming popular in the US and some European nations. Influenced by the global trend, the architecture in Taiwan has adopted this type of buildings. However, when irradiated under direct sunlight, this type of building is considered to be badly insulated, so that a huge quantity of energy is needed to provide adequate air conditioning for resisting the outdoor heat loadings.

More intensive solar radiation causes either higher indoor temperatures, heavier loading on the air-conditioning unit, or higher consumption of electric energy. If solar energy is available, more intensive solar rationing means that more electricity can be generated. Hence, if the building is covered with solar panels instead of glass windows, the incoming solar radiation can be intercepted for generating electricity that will provide building cooling in addition to reducing the indoor air temperature caused by direct sunshine. The excess electricity can be sold back to the power company to offset the peak loading period. Hence, in this research, the energy audit for the buildings covered with glass panels and cooled with central air condi‐ tioners will be carried out for developing three types of "integrated solar panel" systems.

In this research, the results of analysing indigenous climates and examining building materials are used to propose the replacement of conventional glass plate by solar photoelectric panels to be an integrated part of the building shell proposed as the BIPV (Building-Integrated Photovoltaic) system in building architecture. Results of laboratory studies proved that in addition to providing electrical energy to the building, the BIPV building shell is also effective in thermally shielding and isolating the building.

The BIPV system proposed in this research will greatly alleviate the electricity burden during peak hours; its application will promote the development of sustainable energy sources. Comparisons of these solar panels to be used on buildings will be conducted based on their material, angle, temperature, and panel clarity. The results will be used to access the actual cost-effectiveness of installing and using these solar panels on existing buildings.
