Daniel and Shaked, an important fact used in hot water heating is that hot water rises as opposed to cold water.toggle quoted messageShow quoted text
How conventional, and or glass tubed, hot water systems generally work is that the hot water is below the tank, so it rises into the tank, generally entering in at the top, simply because it is lighter, and therefore leaves the hot pipes.
As it does that, cold water from the bottom of the tank sinks down to replace it, and finds itself in the entry to the hot pipes, - whereupon it becomes hot and rises in it’s turn, - this requires ‘no' energy but it does require that the pipes from the tank always rise, - no downward dips to block the flow, and likewise for the thermo syphon down to the bottom of the storage tank, +, being close helps.
When the water in the pipes warms, the process begins, - without any senses, switches etc,
So, for eg in a solar hot water domestic situation you often have the tank directly under the hot water solar panels,- up on the roof, the classic configuration, or the tank in the ceiling above the woodstove down in your loungeroom, kitchen etc.
The thermosyphon requires no pumps, instruments. temperature switches, etc. - the water in the pipe gets hot and rises,but of course one can make a system with those, - and often necessary, but not needing that extra level of equipment etc..
Hope that that muddies the water appropriatly. :)