... capacity150L-300LHeat preservation72 hoursDay efficiencymore than 45%Heat collectorall glass vacuum tubeQuantity of vacuum tubes16,18,24, 30,Absorption rate93%thermal ... before using, in order to avoid scalding Working PrincipleSolar vacuum tube was evacuated into the tank; the coating ... sunshine, consumer can enjoy comfortable bathe anytime. 200L Heat Pipe Vacuum Tube No Pollution Solar Water Heater