Self-pumping solar heating system with geyser pumping action

US patent number 4,478,211

From the summary of the invention:

Important objectives include the provision of a solar heating system which is self-pumping by means of geyser pumping without use of electrical energy or pumps, yet which has the desirable features of a pumped loop system, namely optimum location of system components such as a storage receptacle located below the solar collector; the provision of a system which is self-regulating and operates on demand when the positive temperature difference between the solar collector and the storage receptacle is great enough, requiring no sensors, controllers, or valves; the provision of a system which does not thermosiphon or pump backward when not operating and, therefore, does not lose heat from the storage receptacle; the provision of a system which requires little or no maintenance, has a long lifetime and a low lifetime cost.

See  US patent number 4,478,211  here.