How is liquid used in active solar heating?

In active solar heating systems, a liquid is used as the heat transfer medium to absorb heat from the solar collectors and carry it to the storage tank or heat exchanger. The liquid, typically a mix of water and antifreeze, circulates through the system via pumps to transfer the collected heat efficiently to where it is needed in the building for space heating or hot water. Using liquid as a medium allows for more flexibility in system design and better heat distribution.