Heres a solar water heater setup that augments your homes water heater instead of replacing it. The system monitors a solar collector panel on the roof for temperature. If the temperature is warm enough a photo voltaic cell powered pump circulates cold water through the system. The heated water returns to the top of the homes water heater. Unlike the warm-climate solar heater we saw earlier this one can withstand freezing because it uses silicone tubing in the collector.

[Thanks Marius]

You do know that if you use a Heat exchanges and a closed loop you can make any design a cold weather design.

I built one a very long time ago that simply used car antifreeze and a heat exchanger. worked great.

Posted at 8:16 am on Jan 11th 2010 by farthead

But if the outside weather is freezing = no more hot water.

Posted at 8:26 am on Jan 11th 2010 by Hackius

@Hackius

Usually these systems augment but not replace. You can put the hot water through a mixing valve and an on demand system. If the water is already hot enough the on demand does nothing if its not warm enough the on demand system will kick on and bring up the temp.

The mixing valve is also important as half of the problem with solar collectors is during the warm months the water can be far too hot for domestic use.

Posted at 9:00 am on Jan 11th 2010 by Eric

The problem with the design is that water is going through the solar collector so you can not add any anti-freeze to it so it will freeze. Secondly because the water is a constant supply of new water it will soon get clogged up with mineral deposits.

Ideally you need a second coil in the hot water storage tank that is below the one that is heated by your normal furnace/boiler.

Posted at 9:24 am on Jan 11th 2010 by Going Digital

Why not just make it a drain-back system? You dont have to worry about freezing in that case and its more efficient then adding glycol to the system. Its also fairly easy to implement. An expansion tank might not be the worst idea either if youre pressurizing.

Posted at 9:24 am on Jan 11th 2010 by Pierce

socialist brothers at wikipedia and a time cube website template? Hilarious.

Posted at 11:02 am on Jan 11th 2010 by sol

I live in Minnesota. We routinely get below zero farenheit temps out here. Drain-back systems are of limited use when water will freeze in ten seconds(ever thrown a cup of coffee out and have it freeze before hitting the ground&I have). A separate heating loop with antifreeze is a much better choice. With a fairly simple circuit you can also control how hot it gets in the summer. Just shut the flow off for a bit when it gets to hot. You need to ensure that the hot side can take the pressure or is vented.

I have been kicking around building a system for my new house here. I have great southern exposure for a 242 x 82 set of panels. I have also thought about constructing a heat battery to hold the heat from the summer months for home heating use.