solar water heater swimming pool heating system

in this active, closed-loop system,incoming potable water is routed to the solar storage tank, but never into the collectors. A water and antifreeze mixture circulates from the collectors through a coil of pipe in the solar tank,and then is pumped back through the collector.the potable water is warmed by heat transfer through contact with the pipe. In most climates,a 50/50propylene glycol and water mixture will keep collectors from freezing. These systems require an expansion tank and  a few other auxiliary components for filling,venting,and maintaining the system A definate advanage to antifreeze system is that the collectors can . be mounted anywhere.  these systems are pretty much the only choice in very cold climates.