Active Solar Thermal

Just wondering if anyone uses and active solar thermal system to heat their greenhouse. If so, how many panels and how big a storage tank for what size of a greenhouse?

active solar is moving water or air with pumps or fans, to storethe heat. i use fans to move heat on sunny days to rock storage under growing beds. works great.
moving heat to storage is planned by studying solar heat gain, building heat loss at night, and sizing the passive and active solar heat system to meet the building's needs. a good solar design book will give the formulas