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Dump load, water heater, propylene (or ethlyene) glycol...

mvonw

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I have been toying with the idea of using a 240Volt water heater powered with the excess PV from my inverter dump load to store and release heat(more slowly than a resistive heater) in my workshed/power house.

My idea is to fill the system with propylene glycol and heat and pump that through a small heat exchanger. The reason to use antifreeze is that this would be a closed system and would not always get enough power to keep water above freezing. I don't need it to heat the shed up a lot, just keep it about freezing/more stable temperature in winter.

Is this a doable idea?
 
My idea is to fill the system with propylene glycol and heat and pump that through a small heat exchanger.
Why not just get a 55 gallon barrel and put a 2000W hot water heating element in it from the side?
Extra credit for a temp sensor to stop when near boiling point of your liquid.
 
Why not just get a 55 gallon barrel and put a 2000W hot water heating element in it from the side?
Extra credit for a temp sensor to stop when near boiling point of your liquid.
I'm considering that too, but my concern is that the barrel would need to be insulated to keep it from freezing (releasing it's heat too quickly). In winter, I may only get 3 hours of power after the batteries have charged, but I can harvest a lot of power during that short window (>15Kw/hour). Currently, my shed temperature is -14F.

My thought with a heat exchanger/pump is that I could control the release of heat. Maybe I'm an idiot
 
the barrel would need to be insulated to keep it from freezing (releasing it's heat too quickly).
Insulation is cheap and easy. Low incident of failure.

Pumps and electronics more expensive and prone to failure at -14F (i've been camping in -33F and stuff works differently when ridiculously cold).

A pile of hay, mud, ...
Partially (fully?) burry...

Lots of easy solutions i would try before pumping.
 
I'm considering that too, but my concern is that the barrel would need to be insulated to keep it from freezing (releasing it's heat too quickly). In winter, I may only get 3 hours of power after the batteries have charged, but I can harvest a lot of power during that short window (>15Kw/hour). Currently, my shed temperature is -14F.

My thought with a heat exchanger/pump is that I could control the release of heat. Maybe I'm an idiot
Sounds like a fun project. I enjoy brainstorming on and then doing these sorts of projects.

How big is your PV system and inverter? Are you saying you've got up to 15 kW to spare once your batteries are full? If that was the case I'd first start with something like a ceiling mount shop heater.

Related to your idea: I'm getting ready to set something up for a customer to tie into thier existing radiant in floor heating system. I'm going to use a 120 gallon water heater and rewire it so that both 4500 watt elements can run at the same depending on how much power they have to spare and thier heat load at the moment.
 
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Yes, you can do this. Actually, here in NL there are some pilots using various techniques to archieve this.

Examples are www.borg.energy -> a big insulated tank which can be installed in the ground (thus less affected by freezing since the ground temperature is pretty constant) which contains 4000 liters of water (1050 gallon)

Another example is www.solarfreezer.nl . In NL, most houses are build with concrete/stone and have a tiny 'basement' for sewage, pipes and so on. They use this space to put in a big 'bag' of water.

In the UK, there is a manufacturer who makes 'adjustable controllers'. A regular heating element is just a fixed amount of xxx watts. And instead of on/off switching, it automaticly adjusts the heater output. So if there is only 500W excess solar, it won't pull 1000W from the batteries/grid, but instead ramps down the heater to 500W. ( https://www.marlec.co.uk/product/solar-iboost/ )

In Belgium, in the past, they used storage heaters: Heat-up with cheap nighttime electricity, cool down slowly during day.

This might be adapted to your usecase as well, some have multiple resistive heating elements and by making something smart you can enable/disable elements to heat it faster or slower when there is less solar. And might be cheaper to source. At least in Belgium they are getting more available used since the prices have gone up and the night/daytime difference isn't sufficient anymore to make sense.
 
Sounds like a fun project. I enjoy brainstorming on and then doing these sorts of projects.

How big is your PV system and inverter? Are you saying you've got up to 15 kW to spare once your batteries are full? If that was the case I'd first start with something like a ceiling mount shop heater.

Related to you idea: I'm getting ready to set something up for a customer to tie into thier existing radiant in floor heating system. I'm going to use a 120 gallon water heater and rewire it so that both 4500 watt elements can run at the same depending on how much power they have to spare and thier heat load at the moment.
Fully off grid. I’ve got a Sol Ark 12K maxed out on PV and a separate Schneider 600 charge controller with 20kWp of panels and a 720ah battery (48v) . I’m grossly over-paneled, but it almost always charges the battery fully even on super cloudy/rainy days. I may just try the 240 volt heater, but it would heat the space quickly and then the extra Pv would go to waste. I think some kind of storage is the way to go..
 
Yes, you can do this. Actually, here in NL there are some pilots using various techniques to archieve this.

Examples are www.borg.energy -> a big insulated tank which can be installed in the ground (thus less affected by freezing since the ground temperature is pretty constant) which contains 4000 liters of water (1050 gallon)

Another example is www.solarfreezer.nl . In NL, most houses are build with concrete/stone and have a tiny 'basement' for sewage, pipes and so on. They use this space to put in a big 'bag' of water.

In the UK, there is a manufacturer who makes 'adjustable controllers'. A regular heating element is just a fixed amount of xxx watts. And instead of on/off switching, it automaticly adjusts the heater output. So if there is only 500W excess solar, it won't pull 1000W from the batteries/grid, but instead ramps down the heater to 500W. ( https://www.marlec.co.uk/product/solar-iboost/ )

In Belgium, in the past, they used storage heaters: Heat-up with cheap nighttime electricity, cool down slowly during day.

This might be adapted to your usecase as well, some have multiple resistive heating elements and by making something smart you can enable/disable elements to heat it faster or slower when there is less solar. And might be cheaper to source. At least in Belgium they are getting more available used since the prices have gone up and the night/daytime difference isn't sufficient anymore to make sense.
Those are just amazing! I wish we had those in the states. I have a lot of land and and excavator at my disposal. My wife is Dutch. I’m going to ask her to translate..
 
Fully off grid. I’ve got a Sol Ark 12K maxed out on PV and a separate Schneider 600 charge controller with 20kWp of panels and a 720ah battery (48v) . I’m grossly over-paneled, but it almost always charges the battery fully even on super cloudy/rainy days. I may just try the 240 volt heater, but it would heat the space quickly and then the extra Pv would go to waste. I think some kind of storage is the way to go..
Here's how I'd do the initial math if I was planning on pumping pure water into slant fin baseboards. Depending the concentration of glycol you'll have less BTU's but 90% of the below numbers would be a pretty safe starting place.


1675546073088.png
 

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