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Water heating, in a vehicle

I have rethought saying that using an external heat exchange would add complexity. That is probably wrong and it would also make it easier to ensure you are only extracting heat from the cooling system when you are at operating temperatures.

If you cut in a bar and plate or a tube in tube style (both have their advantages and disadvantages) into the heater circuit, and just pump water to the heat exchanger from your storage tank you can easily integrate a thermostat so it only pumps water when the engine is hot and as you say coolant volume remains basically the same which is desirable.


Being that you may travel to freezing temperatures it would be good if the return line to the tank was above the waterline in the tank so that the fresh water traveling to the heat exchanger siphoned back to the tank and no fresh water remained in the lines. You would also want to ensure the heat exchanger could drain as well.


The main issue is line size. Ting into a 1.5 or 1.75" hose is a lot harder to find parts for than it is for regular 5/8" hose. The other thing is the coolant in the heater circuit is always full engine temp. The rad circuit will vary in temp and volume flowing through it.

Thanks! You are providing a lot of useful feedback/knowledge.

The way I've seen it done with the heat exchanger, is not to pump water from the tank directly through it, but to use a closed circuit with a non-toxic but non-water (glycol?) Liquid, so freezing would not be an issue I think, and if there were a failure, risk of contaminating the water would be mitigated.
 
Thanks! You are providing a lot of useful feedback/knowledge.

The way I've seen it done with the heat exchanger, is not to pump water from the tank directly through it, but to use a closed circuit with a non-toxic but non-water (glycol?) Liquid, so freezing would not be an issue I think, and if there were a failure, risk of contaminating the water would be mitigated.
Ethylene glycol vs propylene glycol.

Propylene glycol won't taste great but also won't kill you. Used a lot in cosmetics. It's not as effective as the other stuff and you need more by percentage for the same freeze protection but is effectively non-toxic.

I used to deliver both types at my last job way back a decade ago.
 
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Gotcha. That makes more sense based on what you had said earlier. Ethylene glycol is regular antifreeze. Propylene glycol would be a good isolator for the potable water circuit.

Food for thought: You can usually run propylene glycol in the cooling system so you could not have to go the the extra lengths of 2 heat exchangers to protect the potable water supply.

One more consideration: Glycol mixes have a lot lower specific heat than straight water does. You will lose 10-15% of the energy per unit mass.


 
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Everyone does and says stupid things at times. It does not make you inherently stupid or asinine. Myself included.

Edit: When you are wrong, the people around you have an obligation to point it out so you can stop making stupid mistakes.
Jordan Peterson
We have a difference of opinion. I’m ok with that.
Nobody is obligated to try my suggestion which was:
Another way of harvesting ’waste’ watts while driving could be a 120VAC alternator dedicated to a ~10gal electric water heater. As with coolant heat (watts, BTUs) there is a cost in fuel mileage albeit probably higher for mechanical energy creation. On the other hand, at steady-state and particularly flat-ground travels and “city” or urban travels internal combustion vehicles produce more horsepower (watts) than the load of maintaining speed. In other words the heat produced at low or mid part throttle exceeds the heat needed to drive at constantly varying levels. So an alternator load can ‘use’ that tiny difference, and when it requires horsepower to turn the alternator the percentage load is probably so small an effective difference may not even be noticed in fuel mileage.

You either didn’t read the post or you really like to argue
The argument is completely asinine.
Which is in essence A) not reading what I said, and B) calling me asinine.

Quoting Jordan Petersen doesn’t make you right. For one, you are not “the people around you” Petersen is referring to. This is a public forum of mostly - if not completely - made up of strangers you will never meet. Secondly, you don’t like my brainstorming idea. Fine. Even say so. But you don’t have to be a jackwagon. There’s been some suggestions posted here I like better myself. Move along.
is not a solar specific discussion, but I'd like to discuss solutions to the energy intensive act of heating water. What solutions have you found to be most practical or most efficient for your application?

I like the idea of having multiple methods, with the primary methods be methods that take advantage of excesses or 'free energy' when available. A "3 Way" (or 4 way) solution that makes use of excess solar power when available (using a DC heating element), and heat from the engine when driving, and a third method that is on demand (not necessarily in the sense of 'instant hot'/tankless, I mean on demand in the sense of it doesn't rely upon a surplus of solar or engine heat which is not always available). Diesel hydronic heater or Propane appliance of some sort would be the two alternatives that come to mind.

I'd like to just discuss / brainstorm ideas when it comes to water heating, so the convo doesn't need to stay restricted to my specific considerations outlined above.

^^^^ The original question: OP mentioned brainstorming. So I threw out an idea that came into my head as I remembered adding an 8000btu air conditioner on a 120V alternator installed a snow groomer being used in summer as a flail mower on the slopes. Just a wild hat idea maybe not even a good one and you want to take that idea and debate it like the Nobel Prize is on the line over creating or destroying energy.
As with coolant heat (watts, BTUs) there is a cost in fuel mileage albeit probably higher for mechanical energy creation…the percentage load is probably so small an effective difference may not even be noticed in fuel mileage
Whatever dude.

I have no problem being corrected when I’m wrong. It’s happened on this forum probably three times that I can think of anyway. I don’t even know why I’m arguing with you anyway. It’s not your thread, it was started by a moderator, and you want to moderate the thread. Carry on.
 
Holy hell, I am actually starting to feel bad for you at this point. The attempt to save face is doing the opposite.

It is never a good idea to use an internal combustion engine to generate electricity to produce heat. Ever. There is no exception to this.

Do the math. ICE= 30% efficient Automotive alternator+ 50-60% efficient. You are down to utilizing ~15% of the energy you input and no, there is on free energy you can practically recover from the drive train with out implementing some kind of additional monitoring and control.

Saying that, it does not mean that in some circumstances it is not the best option. I am going to be using ICE generated electricity for heat.

My vehicle will be used in the winter and may encounter -40 temps. I have to have some kind of block heater. I looked into a hydronic heating system but the fact that I will need to use this 0-5x per year for an hour, the cost and complexity of the system did not make sense. I have decided to go with 2 600w block heaters and 1 120w oil pan heater.

The alternator in a generator is a bit more efficient than an automotive alternator but you are still in the 20-25% total efficiency range to produce AC power, converting it to DC and then back to AC you will take another hit so you want to avoid that as much as possible. I have a yamaha ef2400 right now but am going to be downsizing to an ef1000 ( I want a physically smaller and lighter generator) which will leave me with 900 watts. Because I have a multiplus it will pass the 900 through and add the additional 450 watts required by the heaters so I am only paying the conversion penalty on 1/3 of the heating current.

Its a garbage solution and doing this on a regular basis would be straight up stupid from the perspective of efficiency but since I only need to do it occasionally, if ever, for an hour, capital cost is $30 for a second block heater and oil pan heater, install time is 30 min and I already need a generator anyway, sucking up the horrendous efficiency loss vs the cost of a hydronic heating system with its plumbing, 2nd tank and different fuel IMO makes this the best option.
 
Yes, the "small one" has no thermostat located anywhere in it and it is isolated from the "big one" by a thermostat. Making the water heater loop part of the "small one" with out any control built in will increase the time it takes the engine to reach operating temperature. It is just a fact about mass you can not deny. The amount of time is dictated by how much water you are trying to heat.
For most of my projects I was paralleling the interior heater with the heat exchanger. So it's not a single loop anymore - basically you have 2 small loops parallel. Now you get yourself a inline thermostat (fully mechanical) which opens at 160 or 180 if you like.
So the heat exchanger loop only gets hot coolant when the engine is hot.

and by the way - when you got a Chevy truck, from 2000 and later - those things don't even let coolant flow to the interior heater before the engines emissions system go to ready. They got a electronic or vacuum valve which closes even the small coolant loop.

While I agree with the mass issue you are mentioning.

But - That problem is solved, modern engine control is pretty effective at keeping the block at operating temperatures, you are more likely to freeze in the cabin then the block is not getting up to temp. (which is common complaint in modern cars)
 
Thanks! You are providing a lot of useful feedback/knowledge.

The way I've seen it done with the heat exchanger, is not to pump water from the tank directly through it, but to use a closed circuit with a non-toxic but non-water (glycol?) Liquid, so freezing would not be an issue I think, and if there were a failure, risk of contaminating the water would be mitigated.
you can just run the coolant through a cooper tube and wrap that around whatever container you are going to use.
Blanket that construction in plenty of insulation and the heat will go into your drinking water - through the shell of housing. No risk of contamination.
 
For most of my projects I was paralleling the interior heater with the heat exchanger. So it's not a single loop anymore - basically you have 2 small loops parallel. Now you get yourself a inline thermostat (fully mechanical) which opens at 160 or 180 if you like.
So the heat exchanger loop only gets hot coolant when the engine is hot.

and by the way - when you got a Chevy truck, from 2000 and later - those things don't even let coolant flow to the interior heater before the engines emissions system go to ready. They got a electronic or vacuum valve which closes even the small coolant loop.

While I agree with the mass issue you are mentioning.

But - That problem is solved, modern engine control is pretty effective at keeping the block at operating temperatures, you are more likely to freeze in the cabin then the block is not getting up to temp. (which is common complaint in modern cars)
That is interesting, I was not aware. My 2018 golf r, 2017 tiguan and 2018 CRV certainly do not operate that way. I have to manually turn the HVAC system off to get the engines to warm up faster and it makes a very noticeable difference, especially in the golf.
 
When i purchased my base vehical it came with a diesel heater so i used a heat exchanger inline with the blown air heater pipe and heat my water that way (i use a flap valve to direct heat to either the exchanger or blown air outlet), next up is a 12V immersion element to use as a dump load for the solar, only really usefull if you already have a diesel heater but it was the cheapest instal option in my case due to simplicity and initial outlay.
 
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