... transfer medium liquid2) Temperature preservation is equipped with standard electric water heater setting,automatic temperature control exchanger, and increased anode magnesium ... 3.37) Solar working station8) With heat pipe: anti-freezing > -35 degrees centigrade9) Water capacity: 150L, 200L, 250L, 300L, 500L ... in winter)12) Heat preservation: 72h to 80h Heat pipe solar collector for solar water heater