I have electric baseboard heating know my home, but I do not live their in the 4 coldest months. During that period I maintain heat only in one room. The room is 8' x 12' and is well sealed and insulated well with insulation in walls, floor and ceiling

The issue is that in rural Ontario in the winter we are often hit with power outages. I am looking for some way to provide alternative electric heat when this happens. I wondered if would be practical to use solar panels to store electric in large batteries that could provide electricity to the baseboard heater.When the power is off.

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    Hello, and welcome to Stack Exchange. So, you want to keep the room warm while you aren't there in the coldest months, correct? Is it for plants, or to keep pipes from freezing, or something else? – Daniel Griscom Dec 1 '18 at 2:36
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    How long are the power outages? – batsplatsterson Dec 1 '18 at 12:53

The fundamental problem is that electricity is a positively terrible way to store heat. First, electricity doesn't store much heat energy. Second, converting solar heat to electricity in a PV panel has a positvely terrible exchange rate of like 5%, to say nothing of 20-30% losses in and out of the battery, with the battery itself being prohibitively expensive. It's just thermodynamically impossible unless you have a million dollars to spend.

Far better to store the sun's heat directly - using a solar-thermal panel to collect it, and a big hyper-insulated tank of rocks to store it. Rocks are cheaper than batteries, and solar thermal panels are a heck of a lot more efficient than PV. Truth be told, water is a far better heat-storage mass, actually the best available... but you have a risk of that freezing, so you want antifreeze at least in the transfer loops.

However, I gather none of this is practicable for you. In that case, burning stuff makes the largest amount of heat by far, though, it's not green.

An Empire style wall furnace

I'm not supposed to tell you about these. These are electricity-free furnaces which work on a millivolt thermostat. So you have a normal thermostat on the wall, it's just millivolt and doesn't require any power.

They come in sizes ranging from 10,000 to 50,000 BTU. The 50,000 mounts on an interior wall and heats rooms on both sides. These units run on natural gas or propane.

The reason you've never heard of them is they are exclusive to the sunbelt. I have no earthly idea why; having sat through many rust belt blackouts with the house freezing, vs. a few sunbelt blackouts with the heater going "ka-thunk wooosh" at normal intervals.

I suppose there's a risk, in a poorly insulated house, that if you closed off a room too well, the heat might not reach through and freeze pipes. But in your case, your aim is to heat one room, so it's perfect.

You can also parallel the normal 'stat with a Nest or other 24V stat, just add transformer and relay; the Nest will fail when the power fails, but that's why you leave the normal 'stat in place as a fallback and set it to 50F/10C to prevent freeze.

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  • Although I agree there is no good way to store electrical energy at this time many solar and wind powered systems do this in different ways. The most common is using batteries not very efficient at this time. The millivolt thermostats the most common type being a simple glass vile with a drop of mercury that last 50 to 90 years have been outlawed requiring other means that actually cost more because they require power to operate. So if I read your response correctly or at least in part I disagree. – Ed Beal Dec 1 '18 at 2:11
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    @EdBeal You hardly need mercury to make a switch close. Millivolt thermostats are readily available that do not use power, are Calif./RoHS rated, and will work on my furnace. Care for anAmazon link? Also while I thank you for your feedback, the DV is unfair. Please withdraw it. – Harper - Reinstate Monica Dec 1 '18 at 2:24
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    Perfect solution. It does require significant install work but no more invasive than some complex battery setup. These heaters are ubiquitous in warmer climes, I think because they perform well for occasional/incidental use but are not efficient for continuous whole-house heating compared to ducted forced-air systems.. – Jimmy Fix-it Dec 1 '18 at 14:43
  • @harper I said the mercury stat is the most common style (also the longest lasting) I did not say it was the only way. – Ed Beal Dec 1 '18 at 16:41
  • @EdBeal it isn't the most common style anymore, as they are no longer made... and thus, irrelevant to a new build. I am unclear whether you downvoted me because mercury thermostats are better (I didn't say anything about type of 'stat) or because you believe all the non-mercury ones require batteries or thermostat power (that is not true). What is wrong with my answer that it needs a DV? (Or was it a tablet induced error as mine often does, if so click it again, it'll come off). – Harper - Reinstate Monica Dec 1 '18 at 21:27

As mentioned in @Harper's answer it's hard to store enough electricity to make a dent in heat.

The Tesla Powerwall battery stores an impressive 14kWh of electricity. It's not cheap. If the electric heat is the only load on the powerwall battery, I am betting it would heat a reasonably well insulated 8' x 12' room to a tolerable temperature for 24 hours. That's just a ball park guess.

If the power outages are short enough that the Powerwall can cover you and recharge before the next outage, it's a fairly simple solution.

Another consideration: If you're just heating that room to keep pipes from freezing, you could retrofit heat tape on the pipes, and just back up the heat tape power. It would take less power to keep the pipes from freezing than to keep that room heated.

Finally, whatever you do, I'd consider some notification system to let you know when power goes out, when it comes back on, and when the temperature dips below a certain level. This way you can arrange to have someone come over and set up temporary heat if there's a problem.

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store electricity from the mains in batteries, or use solar to heat the room directly.

or perhaps just store a large quantity of water in the room, the water will store heat keeping the heat in the room up.

Phase change heat storage is another option chemicals like formic acid, acetic acid, and glycerin are liquid at room temperature but will freeze above the freezing point of water before water meaning they can provide a lot of heat as they cool

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