To develop indigenous alternative and renewable energy resources, long-term subsidy programs (1986-1991 and 2000-present) for solar water heaters have been enforced in Taiwan. By the end of 2010, the total installed area of solar collectors had exceeded 2 million square meters. However, over 98% of solar water heaters were used in residential systems for hot water production, with the areas of installed solar collector being less than 10 square meters. There were only 98 systems with area of solar collectors installed exceeding 100 square meters put into operation from 2001 to 2010. These systems were mainly installed for water heating in dormitories, swimming pools, restaurants, and manufacturing plants. In the present study, a comprehensive survey of these large-scale solar water heaters was conducted. The objectives of the survey were to assess the system performance and to collect feedback from individual users. It is found that lack of experience in system design and maintenance are the key factors affecting reliable operation of a system. Hourly, daily and long-term field measurements of a dormitory system were also examined to evaluate its thermal efficiencies. Results indicated that thermal efficiency of the system is associated with the daily solar radiation. Hot water use pattern and operation of auxiliary heater should be taken into account in system design.
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