PURPOSE: To contrive to reduce the operating cost of the heat collecting pump and improve the heat collecting efficiency by constituting a heat collecting pipeline from a regenerating tank to a heat collector by one pipeline and controlling the heat collecting pump and the switching valve by the difference between the temperature of a high- temperature side senser of the heat collector and the temperature of a low-temperature side sensor of a regenerating tank.

CONSTITUTION: Hot water the temperature of which has been raised in a solar heat collector 1 collecting solar heat, is accumulated in a regenerating tank 2, and the regenerating tank 2 and the heat collector 1 are connected to each other by means of one heat collecting pipeline 3. A heat collecting pump 5 and a switching valve 8 are disposed in this pipeline 3, and a high-temperature side sensor 12 is provided at the lowest temperature part of the heat collector 1. On the other hand, a low-temperature side sensor 13 is provided in the tank 2. That is, the pump 5 and valve 8 are controlled by the temperature difference between the sensor 12 and the senser 13 whereby the water in the tank 2 is supplied to the heat collector 1, and hot water the temperature of which has been raised in the heat collector 1 falls in the tank 2. Accordingly, the pump 5 is intermittently driven, and the operating cost of the pump 5 is made low. Further, since one pipeline 3 is provided, and hot water flows intermittently, radiation loss is greatly reduced.