Cold climate solar water heater

Here’s a solar water heater setup that augments your home’s 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 home’s 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]


  1. farthead says:

    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.

  2. farthead says:

    in fact for a very simple heat exchager that works great.

    use glycol. because copper pipe conducts heat far better.

  3. Hackius says:

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

  4. Eric says:


    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 it’s 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.

  5. Going Digital says:

    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.

  6. Pierce says:

    Why not just make it a drain-back system? You don’t have to worry about freezing in that case, and it’s more efficient then adding glycol to the system. It’s also fairly easy to implement. An expansion tank might not be the worst idea either if you’re pressurizing.

  7. sol says:

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

  8. Taylor says:

    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 24′ x 8′ set of panels. I have also thought about constructing a “heat battery” to hold the heat from the summer months for home heating use.

  9. Manksteve says:

    This statement made me laugh “It is claimed that evacuated tube solar collectors are typically more efficient than flat plate collectors. This does not mean that evacuated tubes can produce more hot water” Spot the contradiction in his own sentences. Evacuated tubes are much better in cold climates

  10. Manksteve says:

    or this statement
    “Most evacuated tube systems require mains electricity for pumps, valves, controllers etc thus negating any gains over flat plate collectors. These complicated systems will almost certainly come with an annual service contract that will be linked to any warranty”
    The reason why his system can use a battery power pump is because it doesn’t produce that much heat compared to evacuated tube.

  11. _matt says:

    I think what he meant by that was that, it’s more efficient, but outputs less energy total.

    Example, Nuclear power plants are way less than 5% efficient, but output orders of magnitude more power than any other power source, despite being the most inefficient.

  12. David says:

    He is simply saying that removing the need for a heat exchanger you get higher efficiency then an evacuated tube + heat exchanger. I’d like to see some independent analysis of this. I can guarantee though that places like Minnesota this will not be more efficient then a evacuated tube + heat exchanger system. You also have the problem of mineral build-up in the system when using potable water.

  13. Manksteve says:

    You dont need a heat exchanger for Evacuated tubes. The reason why heat changers are used in solar panel is so that a mix of anti freeze can be sent though the panel to protect it from frost.

  14. Manksteve says:

    If an energy generator is more efficient it must therefore give out more energy for the same amount of energy input otherwise it wouldn’t be more efficient. in this case the input is solar radiation and the output is hot water.

  15. jay vaughan says:

    Design one that can be reprap’ed, somebody ..

  16. hawkeye says:

    “Not to scale” lol…

  17. stephen says:

    there is a cheap and easy home made solar heater solution using that plastic advertising board that has channels built into it for structural integrity, its easy to use a black plastic version of that some glue and pvc to make a water heater thats more effecient than the evacuated tubes! theres some documentation on it on the web somwhere around here.

    combine this with geothermal cooling, just some underground tubing a 6v water pump (closed circuit water does not require much to circulate) and a radiator style connector and you have cooling for your home too.

    throw in a sterling engine and you have electricity.


  18. stephen says:

    by the way, many solar systems can be run passivly at a cost of less heat output. if the consideration is energy in vers energy out just run a passive system. the only difference is the way you run the plumbing and pressure release valves.

  19. stephen says:

    this is the link of one person building this type of system and using it. done on the cheep this unit has potential. unfortunately the insulating box and possible degridation of the plastic weakening over time due to solar exposure might make it financially undesirable however i have not seen any long term usage posted of such an item, and this is used in road signs.

  20. stephen says:

    if this system is used for central heating and air then a closed system could be used, a bladder or storage medium for heat could be burried in the back yard with a pressure release valve eliminating the need for any pressure or temperature sensing circuits. a 12v 20 watt solar panel could be tied directly for a charging medium to a sealed lead acid battery or a charge circuit could be utilized. the battery can power the air circulation fan and the water pump, if any power supply changes need to be made to accomodate the fan or pump a small step up step down circuit or possibly just a transformer would be needed. the controlling factor is the thermostat which is presumed to already be on mains power and for switching needs can operate a very simple on off circuit to control direct power of the pump and fan. if this is used for more than just heating or cooling a switching box can be tied in.

    the requirements for a AC system of this nature is extreamly simple and energy conservative. it would hands down be more effecient than utilizing a heat pump currently claiming 300% effeciencies on websites. this system becomes more energy conservative if radient floor heating is utilized. for additional heating the system can pass through a tankless heater. solar heating of water does not have to be much to provide a profound savings, simply preheating water to 90f can heat a home and save a considerable amount of cash.

    if one looks at radiant floor heating you will see only a small temperature differential is required to keep a home toasty and solar has frequently been employed with this system to do just that.

    the only question one should be asking is, why dont more people take advantage of this? the answer is money, employing this system would eliminate the need for the AC industry because mantenence is significantly reduced with less electronic and mechanical systems involved and energy consumption is considerably lower.

    like the credit card industry where its better to keep you in debt, the energy and consumer industry finds it better to keep you buying. its just good buisness.

  21. Matt says:

    Stephen, you must keep in mind that the decisions HVAC companies make are dictated by the customers they serve.

    Any sort of solar water or solar house heating system will be augmented by an electric or gas unit which can typically supply, by itself, the maximum heating needs of the building or close to it. Thus there are two independent systems, and capital expenditure has increased by something probably on the order of >50%. So to make sense the additional capital expenditure and maintenance cost must be balanced by a greater reduction of operating expenses over the lifetime of the system. Furthermore, the customer has to be willing to spend the extra up-front cost. If they don’t have cash on hand and don’t want to carry the debt, then it may make best sense for them to get the regular gas/electric heater only.

    Solar water heating makes best economic sense in warm and sunny areas, which is probably why they were popular in my hometown (inland southern california).

  22. stephen says:

    well the beauty of a system like this especially if its coupled with radiant heating is that you can use a single 2.5 tankless heater as the supplimental heat, this unit is a meager $150 if i remember correctly. i have a whole house unit for $300. i think if one actually sat down and planned this out we would find its less than $5k total cost with radiant heat and perhaps $3k-$4k for regular central heat air radiator.

    there are 3 costs that will be high, digging the holes, purchasing solar heater panels, having the bladder purchased and installed. these 3 items will most likely be handled by a contractor above all other items due to the customers inability or lack of desire to do the work themselfs.

  23. stephen says:

    if you were to set up two independent systems then yes the cost would be prohibative, however with my current heat pump setup they do not have 2 independent systems they have augmented the existing system with a heating element so that if the heat supplied by the pump is not enough it can be added to by a electric heater element which keeps costs down by not having a seperate backup system to my heat pump. the same principle would apply to solar and geothermal heating except in the case of water based fluids you would now used a tankless heater or similiar unit. no need for a independent backup furnace thats just overkill.

  24. stephen says:
  25. stephen says:

    by the way to address bias of having solar water heating in sunny areas, well i hear canada loves solar water heaters.

  26. brain fart says:

    Hackaday, my ass! This is ridiculous. Shit like that is commercially available outside of the US for MANY years. Like 25, or more. I have one on my roof for over 10 years.

  27. stephen says:

    in 1982 the solar heating geothermal cooling was patented. yea, its been around a while.

  28. Jason says:

    Tankless water heaters are acualy more economical for alot of home owners. they only heat water when water is called for and for familys that have lots of kids they never run out of hot water.

  29. Certainly, but people need to appreciate that adding Solar in their property is an asset that will raise the future worth of their property if / when they come to a decision to sell. With the environment the way it is going we are not able to ignore any system that presents no cost power at no cost to both the consumer and more significantly the world!

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