Creating A Heating System For Our Offgrid House


Karrie SteelyOur off-grid house building is on schedule. The goal by the end of this year was to have the structure and outside completely finished, and we reached that this fall. We've also gotten the inside insulated using spray-on insulation, and the last step this year was to install hoses for in-floor radiant heat.

A lot of time has been spent thinking about how we're going to heat the house. We will be off-grid, but will have solar and propane and wood.

working on our house   thermometer

With the philosophy that too much is better than too little, we’ve gotten plenty of solar panels for our electricity needs. We built the house with the roof slanted rather than peaked so that they will be at a south-facing angle. There should be lots of power and then some as long as the sun shines. The excess power will be put to good use after the batteries have been fully charged. It will be diverted to heat salt water in a 2,000-gallon insulated milk tank (that we happened to have laying around the farm, a great way to repurpose!). This tank will be used as a heat exchanger, which will have pipes running through it, heating the water running through them. The electrical elements running from the solar panels will keep the water between 180 and 200 degrees. We'll also build a wood burning unit into the tank to heat the water if the sun doesn't shine for several days.

We did some experiments with salt water, and found that in addition to freezing at a much lower temperature, it retains heat better and longer than just plain water, and has a slightly higher boiling temperature. Because the tank will be completely enclosed and constantly heated, the convection motion of the water will keep it agitated so we're hoping the salt won't crystalize. We’re also going to need to buy a lot of salt to get it as saturated as possible.

 flooring and insulation

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