Single-tube integrated collector storage systems with tansparent insulation and involute reflector

Integrated collector storage (ICS) systems, consisting of a pressure-resistant single tube absorber in front of an involute reflector and covered by highly transparent insulation material, have been developed. Compared to the earlier multiple-tube design the system performance has been improved. For an absorber area of 4.2 qm in Freiburg (W.Germany) and a hot water demand of 160 liters/day, the annual solar fraction of the system is 65% with an annual efficiency of 32% (required hot water temperature is 45 degree C) There is no risk of freezing. Detailed computer simulations for the ICS and the back-up heating system have been made and show the influence of various parameters on the system performance. Compared to conventional solar domestic hot water systems the performance of the ICS systems is almost as good as that of systems with vacuum tube collectors but ICS systems require much less complicated technology.