Heat Storage Idea

[Jafo]

So over the winter I have been thinking about a project for yurt camp this summer. One thing we rely on at my camp is propane for hot water. We use solar to pump it, but that is not practical to heat it using induction. I have a couple of ideas though, that I thought I might share and see what kind of feedback you guys have..

The main idea is to get a sealable, metal, 50 gallon drum. I would coil 1/2" copper tubing about 30 inches high around the inside of the barrel. Through the cap of the barrel, I would make water connections to the coil. I would fill the barrel with used vegetable oil.

Now there are a few ways I could go about

heating

this. One idea was to hook up a 12 volt water heater element to a wind turbine (which I have one laying around) and install that in the barrel. Another might be to hook up some sort of parabolic fixture so the suns rays are focused on the barrel. I figure the barrel will be jet black and outside so it should already be getting some of that heat naturally.

My thinking is, this veggie oil would hold and retain quite a bit of heat. Running water through the coil should in theory, transfer that heat to the water.

My concerns are, this would have to be regulated somehow.. It couldn't get TOO hot or otherwise the water would be useless if it melts your skin when you try to take a shower for example. Turbines require the load go somewhere at all times, so some sort of dump load arrangement would have to be figured out.

Thoughts?

[hierony]

Neat idea--I need to get me some hot water setup, too. I've worked some on thermal storage designs--often just straight water is used (insulated underground tanks). Absorbents/Zeolite can also be used (for

heating

& cooling). I've seen some wood-powered water heating setups, too.

Parabolic fixtures are neat--you'd want to align them east-west and adjust the inclination angle throughout the year (or not, so as to decrease efficiency in the summer). Small ones aren't too hard to make, either; but a fixture large enough to surround a drum might be tricky...

You can also get somewhat cheap fresnel lenses, set them up to direct sun onto your drum (not as a focused point though).

Solar heating tubes are also available--but if you already have the turbine & heating element, why spend money?

Like you mentioned, you don't want things too hot. A tempering/thermostatic mixing valve might be useful, but pressure requirements might be problematic. Depending on your setup, there might be a chance of overheating your oil during the summer... It would be good to check numbers for how much hot water you can expect to get out of your oil drum at different temps.

[froit1]

Five years later, where are we at?
Some ideas: insulate the barrel, and keep some energy overnight, pulls your shower-season wider. And insulate it well!
Which means, no need to paint it black, but does need to focus on external heat generation/collection. Through parabolics, or pool-heaters.
Second: not oil, but salty water. If your tech is all plastic, you can add loads of salt, to beyond the saturation point. It will make the water heavier, storing more energy.
Third: The overflow-energy from your windmill can be diverted to a pump in the barrel, just churning it around. Or to a secondary barrel. This will also heat it.

[Wintergreen282]

Wow. I can barely follow this conversation. Lol. Much less embracing it as an option (different strokes for different folks). If anything, I’ve gone simpler over my years of yurt living. From a 3 gallon camping solar shower, my go to “shower” is now heating a gallon of water to the temperature I want (hotter in the winter, cooler to cold in the summer). Strip down and with a bit of the warmed water in a bowl, soap up the stinky bits, walk out to the deck, rinse off. In the winter I will put a piece of close-cell foam down to stand on. And have the fire going to dry off and dress by. Fresh clothes hanging over the wood stove all warm and toasty.

I’m not against more elaborate systems, just find less is more. This reminds me of when the previous yurt owner sketching out some sort of heated floor plan by coiling pipes around the wood stove pipe and down through the floor. So many issues with this plan, IMO. Starting with fact the platform was already built and the yurt in place. And the wood stove was small. I mean, maybe it would’ve been easy, worked well for years, and captured excess heat efficiently. My solution to cold floors for 1/2 the year? Better slippers. ��

I’ve said it before. Half the fun of yurt living is finding off-beat solutions to be happy and comfortable with a smaller, cheaper, hopefully environmentally better footprint. And with multiple inhabitants, sometimes it is more efficient to automate.

Again. To each their own. More power to ya. For me, simple. But good luck to your efforts! That’s how societies advance. And I enjoy reading about all these ideas. Just wanted to make a case for the opposite.

[froit1]

Cool nice of you to get back on this. Indeed, sometimes less is just that, less.
As they say, every answer leads to the next question: how do you heat your gallon of water? And do you worry about the waste-water?

[Bob Rowlands]

I love the "Cold floor put on slippers." comment.

Start with obvious, easy and cheap solution. If that doesn't work you can try another route. Frequently easy and cheap and obvious ends up being the best. The old "When you are up to your ass in alligators..." adage comes to mind, because I have been there sooo many times.

[Wintergreen282]

Hey Froit1,

Sorry. All the “someone has responded to your comment” emails went to spam for some reason and I just now found them.

Anyway. I heat the gallon of water on a 2-burner Colman camping stove connected to a 20 gallon (pound?) tank that lives outside. The same as if I’m cooking or heating water to wash dishes or my hands. I guess, if necessary, I could heat the water on the wood stove, inside the solar oven, or maybe just a solar shower bag, but that would require the wood stove going or sun shining. And take forever. I guess that is where I hit my “less” limit. Lol. I don’t worry about the “gray water”. The wild plants that live around here do esp well under my small deck. They don’t seem to mind a bit of soap and people sweat. Again. To each his own. I don’t have neighbors to worry about. There aren’t multiple people living here. Much of what I do works because it’s just me. Like I explained to my (doubting) brother. If I’m cutting up just one carrot, it’s way more work to drag out the food processer. - Cindy

[skihuckster]

Jafo, you've probably learned a few tricks in 5y on heating, but since this thread is fun I thought I'd pass along some of my engineering knowhow.

First, oil doesn't hold more heat than water (few things do). The advantage of oil is that is boils at MUCH higher a temperature, so if you want to hold heat above 212F (100C) without having an expensive high pressure boiler, oil is your fluid. For hot water...hot water will soak up the most heat from the sun.

Second, what you're going after is capturing as much radiative heat from the sun as possible. Not all "black" paints are created equal. Find one with a really high emissivity (near 1 if possible) as that is a measure of how much solar radiation it will absorb. I think wood stove black paints are good ones.

Third, you'll be fighting heat loss at night, or really any time the fluid in your barrel is hotter than the air outside.

Insulation

will keep heat from leaving...but it will also keep heat from coming in.

For showers, you can't beat the cost to benefit ratio of those black plastic solar showers. You fill up enough water for the shower, leave it out in the hot part of the day, do your thing, and then fold it up and put it in the cabinet.

[Bob Rowlands]

The last four posts span almost two years. Man, this place is outta control! haha