The solar-powered water-heating system was attached to a tank of 1.96 m in diameter and 2.1 ms in height, which could contain 6 t of water when filled up. Driven by the temperature gradient, water circulated in the tank and allowed incoming cold water to be warmed up constantly. To reduce the heat loss from the water-heating system, an insulating cover was constructed using rubbery and plastic materials reinforced with glass fiber and aluminum foils. The system consisted of 18 groups of solar energy collectors, each of which included 56 individual collector tubes. The total system occupied an area of 100.8 m2. The outer diameter of each solar energy collecting tube was about 48 mm, the inner diameter about 38 mm, the wall thickness about 1.5 mm, and the length about 1.5 m. The mean daily efficiency of these solar energy collecting tubes was 51%.