Storing hot water in IBC tote tanks?

[Vance357]

I'm working on a system so that I can store both hot and cold water when power is available for use later on when power is not available. I'd like to have both an insulated cold and hot water tank, but these are quite expensive in any real size. I'm wondering if I could use a standard 275 gallon IBC tote tank wrapped in insulation to store hot water up to around 120-130 degrees? Possibly warmer?

Would they be able to withstand these temperatures for long periods of time? From the manufacturer websites they say you can fill them with chemicals at over 200 degrees, but doesn't say anything about keeping them there for very long. I know the plastic is technically capable of that temp, and the metal cage should help keep it from drooping too much I would think. Should be relatively simple to build a square box around one and add insulation.

Will they become old and brittle too quickly? I would not be using these for potable water, so not really worried about plastic chemicals leaching into the water.

[Harold in CR]

As a comparison I have poured boiling water into a blue plastic 10 gallon barrel that are becoming common replacing steel barrels and let it sit to cool. It transferred heat through the sides, but, never got soft enough to worry about. My plan was to mount it overhead above my shower stall.

This may not tell you much, but, I doubt insulating for 130 degree water will have any effect on the plastic. Breaking down over time, no idea?

[MagnetJuice]

Most likely these tanks are made of high-density polyethylene. That type of plastic is good for 150 F continuous. It would start melting at about 250 F. I'm sure that it would be some sagging at 130 F, but since they are caged it should be OK. But any plastic could crack, so if you use them to store water, make sure that the water don't do a lot of damage when it spills.

Polyethylene is considered safe for water but maybe ten years from now they find out that it is carcinogenic. It is difficult to conduct long term tests on cancer causing chemicals. I would not use that water for drinking or cooking.

If there is not direct sunlight hitting the tanks, they should last at least ten years.

Ed

[Vance357]

Polyethylene is considered safe for water but maybe ten years from now they find out that it is carcinogenic. It is difficult to conduct long term tests on cancer causing chemicals. I would not use that water for drinking or cooking.

Yeah, that's what scares me...it doesn't cause cancer until it does. I definitely will not be consuming any of the water directly. They'll be going outside in a space under a deck, so if they rupture it won't really be an issue.

I've heard that some manufacturers are making standard water heaters with plastic tanks now. Anybody know anything about the plastic they use? If it's HDPE that would sure make me more comfortable...

[Bruce S]

Here is Gary's website
https://www.builditsolar.com/
He's done quite a bit of building for long term storage of heated water.

You could also drop him a message on his website

He does jump on here from time to time and was a long time poster here.

One of the things he said to be wary of when storing heated water was mold and stratified water temps.

Hope this helps too

Bruce S

 

[OperaHouse]

My gut feeling is that this method for hot water technically has issues. Big tank may store for a while, but recovery also is a long time. By power I assume excess PV.  I heat water with PV and have a couple tanks in series with the primary only 6 gallon and secondary 10. That gives a really fast response time even with minimal sun. I run the heater off raw PV voltage in parallel with MPPT charge controller.  Heater control keeps it at power point for high efficiency using whatever batteries don't need.

[Mary B]

Polyethylene is considered safe for water but maybe ten years from now they find out that it is carcinogenic. It is difficult to conduct long term tests on cancer causing chemicals. I would not use that water for drinking or cooking.

Yeah, that's what scares me...it doesn't cause cancer until it does. I definitely will not be consuming any of the water directly. They'll be going outside in a space under a deck, so if they rupture it won't really be an issue.

I've heard that some manufacturers are making standard water heaters with plastic tanks now. Anybody know anything about the plastic they use? If it's HDPE that would sure make me more comfortable...

A little research says they are using polybutene plastic which melts at 190c...

[MagnetJuice]

Mary, to avoid confusion, when you say “they are using polybutene plastic” do you mean for the tote tanks or for the water heaters lining?

Ed

[Bruce S]

Vance357;
I'm also curious about the temps for cold and what you will be using to achieve those temps.

Plastics will as far as my knowledge goes will become brittle quicker in colder temps than hot.

Certainly UV rays will cause plastics to harden pretty quick, however, since you will be covering these with insulation ,,,

Bruce S

[bigrockcandymountain]

I have hot water in one and it works so far.

[bigrockcandymountain]

I am having trouble posting.  Thats why the short reply. 

[Vance357]

Vance357;
I'm also curious about the temps for cold and what you will be using to achieve those temps.

Plastics will as far as my knowledge goes will become brittle quicker in colder temps than hot.

Certainly UV rays will cause plastics to harden pretty quick, however, since you will be covering these with insulation ,,,

Bruce S

It will mostly be a compressor based system...but it's also an ongoing experiment. My electricity cost 1/2 as much during the night than it does during the day. I will run the compressor all night (or as much as needed) and hopefully not need to make extra heat (or cold) during daytime hours. I'm also thinking about making this a fully geothermal system.

Additionally, I'm building a water cooled whole house generator (not unlikely to go a week without power here) and this could easily be used to heat the tanks, saving fuel over running the compressor from the generator. Using water for this system is great because I can add heat in several different ways quite easily. Having thoughts about something wood fired, too.

On top of that I'll be installing some PV panels, which will net meter during the day - when power is most expensive. I'll probably end up with some form of solar heat, also. My property isn't that great for solar, mostly shaded, especially the south side of my roof.

I'm not sure if it would be cost effective, but I'm thinking about building a plywood box to go around the IBC, and then fill with expanding foam. Not only would it insulate but provide even more structural support.

In a nutshell I'm just trying to shift my heat pump usage from during the day to during the night, as well as eliminate the electric water heater for DHW.

[joestue]

at only 150F i would think the polyethylene could last nearly forever. yes it will soften a bit but given that you have a hard shell it should not fail.

one thing i did notice taking apart some's water heater is the discoloration and brittleness of the polyurethane foam insulation that is injected into the gap between the steel tank and the shell. the newer hot water tanks seem to have a failure mode where water leaking from any fitting is captured between the tank and the insulation which accelerates corrosion from outside in. they probably had the water temperature set to 125 for about 11 years.


regarding heat pumps: there are some efficiency gains to be had from running R-22 compressors on R-410 and vise versa. you can use a compressor designed for r-410 on propane or r-22 or rs-44 or M099, and since it is so lightly loaded you can lower the voltage and the induction motor will run more efficiently.

or in the case of an R-22 compressor designed for high head pressure (400 psi) (such as what is found in a dehumidiifer) if you're only dumping heat into a 100F condenser, you can run that compressor on R-410 no problem and you won't hit 400 psi until 116F.

where i'm located propane has a boiling point of -30C and refilling an R-22 system with "propane" results in lower head pressures and compressor loading, this may or may not be acceptable to you given the risk of course. .


anyhow if you want an efficient heat pump you need to find a scroll compressor designed for the pressure ratio your system works at.. or get a reciprocating compressor and lower the voltage delivered to the compressor to get the optimum efficiency. if the compressor is lightly loaded there may be efficiency gains replacing the oil with a lower viscosity.

i have some 4000 btu r-22 reciprocating compressors, high pressure intended for dehumidifiers and at 40F they can hardly start up, drawing 200-300 watts until the oil warms up and they drop to 130 watts no load power consumption*. i was tempted to build a heat pump with them, but there would be no point if i'm burning up 150 watts of heat just churning oil.

*typical scroll compressor from a 30-45 pint per day dehumidifier at no load draws 280 watts no load. in fact the power consumption goes down when you plug up the output for some reason.

[Mary B]

Mary, to avoid confusion, when you say “they are using polybutene plastic” do you mean for the tote tanks or for the water heaters lining?

Ed

Water heater tanks, IBC totes are HDPE

[JW]

The last time I looked at a water heater it was insulated with fiberglass (rock-wool)  then a sheet metal cover. This  became interest to me because when using the burner it would rust pretty good. I then found a aerospace coating(aluminium based coating)  that would stop rust on steel surfaces at high temps. I didn't care about thermal loss. And the coated surface would actually turn red hot and still be decent when cooled off.

just being lazy will use a link, I use this on the outside, not sure what is used on the inside coating.
 http://www.cotronics.com/catalog/36%201529%20201%20Series.pdf

[joestue]

The last time I looked at a water heater it was insulated with fiberglass (rock-wool)  then a sheet metal cover.

probably none made that way since 10+ years ago

[frackers]

Water heaters here (NZ) are generally stainless steel with fibreglass jacket that is enclosed by either zincalume or some sort of styrene plastic if they are mains pressure, low(er) pressure tanks tend to use enamelled steel (i.e. glass coating) or copper (unusual now due to cost).

A major advantage of the stainless tank is that they are quite happy to run over 100c if pressurised.

[bigrockcandymountain]

Try this again.  My IBC tote is hdpe.  I run it at 140f no problems so far.  I use an immersion coil heat exchanger so the water in it is just stagnant sludge. 

[bigrockcandymountain]

Your system you have in mind seems complicated.  Have you actually pencilled the money you will save vs cost and complexity? I would just adjust my habits to use power when it is cheap.  I also live off grid so that is normal for me.

I am curious how the numbers work on this? I am not saying your wrong, just asking for more details on the money end. 

[Vance357]

Your system you have in mind seems complicated.  Have you actually pencilled the money you will save vs cost and complexity? I would just adjust my habits to use power when it is cheap.  I also live off grid so that is normal for me.

I am curious how the numbers work on this? I am not saying your wrong, just asking for more details on the money end.

The vast, vast majority of my energy bills are heating, cooling, and hot water. Otherwise it's just some LED lights, a nearly new fridge, and a laptop. Average tank style electric water heater uses $500-800 per year. In North Carolina we run the air conditioning 6-8 months per year. A normal heat pump just blows all that hot air outside, instead this will give me a nearly unlimited supply of hot water completely free. At the same time it will make the air conditioner cheaper to run, because it won't be fighting as much hot air in the summer during the middle of a hot day. And, while the system is significantly more efficient, it also allows me to use electricity that cost half as much. You can't just "adjust your habits" to stop running the A/C during the hottest part of the day with the most expensive electricity.

In the winter I will have waste cold air to blow outside, but using a heat pump will still make hot water significantly cheaper than a regular electric element. It will also be easy to integrate free sources of hot water such as solar, wood, and waste generator heat. Even garbage - I can probably nearly heat the house with Amazon boxes!

If it only saved me $50/month it would pay for itself quite quickly. And now I have a secondary backup system with my existing standard heat pump and water heater, which will stay in place, just shut off. You don't go without A/C in NC - even for a day! Plus, if I add enough PV panels I can net meter back to zero every month, the payback period would be a bit longer with those, but even if it's 10 years, I consider that a good deal.

Also, as joestue mentioned, compressor systems can be tweaked to be much more efficient than the standard EPA approved mass produced garbage they sell as appliances. I will likely be using propane as the refrigerant, (AKA R209) which is definitely more efficient running at lower pressures than modern refrigerants - and not that bad for the environment either. Since the entire compressor system will be outside, I don't ever have to worry about propane leaking in the house.

And, on top of all that - it adds a good chunk of equity to my house! I would pump my well water at night if I could too, but I can't imagine the fit the HOA would throw if I tried to build a water tower. The reason electric companies offer time of use billing is to give people an incentive to do things like this and reduce their overall load during the hot part of the day.

Forgot to mention - I will be adding on a garage with a large master suite above it in the near future. Given this I'll have to add capacity to the heating/cooling system anyway.

[MattM]

Don't kid yourself about motivations of electric companies.  The smart meters allow them to bill on average 25-33 percent more from the average customer.  People that go through the insane hoops to revert back to analog meters see firsthand big reductions in their bills.  It's always been a scam, those smart meters, pushed overnight simultaneously across Europe and North America.  And nobody paid much attention.

The propane replacement of R22 sounds intriguing.  Is there a diary entry on this?  I have excess heat in Florida, with cold days maybe two weeks in the year.  This sounds like a brilliant way to warm the house on the 2-3 months where the thermal pumps run at night to maintain temps.

[bigrockcandymountain]

Ha ha we could almost heat with Amazon boxes too. 

Air conditioning is something i seem to never think about.  Most people have it here, (the hottest part of canada) but it is pretty unnecessary in my opinion. 

How efficient are we talking with propane?  I looked hard into geothermal with a cop of 4 as the very best.  Can you beat that?  That would be awesome and you would have me dreaming up more projects.

You may want to run brine on the cold side.  The evap coil will freeze water pretty easily. 

[joestue]

Ha ha we could almost heat with Amazon boxes too. 

Air conditioning is something i seem to never think about.  Most people have it here, (the hottest part of canada) but it is pretty unnecessary in my opinion. 

How efficient are we talking with propane?  I looked hard into geothermal with a cop of 4 as the very best.  Can you beat that?  That would be awesome and you would have me dreaming up more projects.

You may want to run brine on the cold side.  The evap coil will freeze water pretty easily.

propane is a mixture of isobutane butane and propane, where i live it boils at about -30C. how much lower pressure at room temperature it is compared to pure propane, i don't know.

regarding the cop of a heat pump: replacing r 22 with "propane" is going to lower the pressure a bit. this may or may not make it more efficient.

a small 1 ton compressor has an induction motor in it.. that i'm guessing is 70% efficient. the scroll is isothermally 90% efficient (same as a reciprocating) but only at the (suppose it is) 3:1 pressure ratio it was designed for.  at a 2:1 pressure ratio the compressor may only be 70% isothermally efficient which means that with your 70% efficient induction motor.. you're doing twice as much work on the gas as you need to in order to push it through your heat pump.

reciprocating compressors are far better at scroll compressors below the optimum pressure ratio.

if you build a high efficiency heat pump system you need to find a low head pressure compressor designed for a lower pressure ratio.. the motor is smaller than the compressor.

alternatively, you can use a high pressure reciprocating compressor (such as the example i gave with my 4000 btu dehumidifier compressor) change the oil out for a lower viscosity. and, reduce the voltage to the motor. (rather than reduce the voltage to the motor you can use a vfd to drive the motor faster than originally intended.)

regarding vfds and permanent split capacitor compressors.. build a scott T transformer and drive the motor from a 3 phase vfd.

[Vance357]

Don't kid yourself about motivations of electric companies.  The smart meters allow them to bill on average 25-33 percent more from the average customer.  People that go through the insane hoops to revert back to analog meters see firsthand big reductions in their bills.  It's always been a scam, those smart meters, pushed overnight simultaneously across Europe and North America.  And nobody paid much attention.

Sorry, but I add those people to the flat earth and "we didn't land on the moon" club. There is no proof what so ever of what you say by any respected professionals. Only people that generally don't know what a kilowatt is and are scared of new technology. They absolutely DO NOT bill the average customer 25-33% more. *sigh* And no, I never saw an increase in the bill when they installed mine. Most of the morons are scared of the radio waves, while they stand in front of the microwave and talk with a cell phone strapped to their head.

Anybody could install an old school spinny meter downstream of their smart meter and see if the numbers add up, most likely, they will. There are some cases where the old spinny meter was just worn out and inaccurate (how many decades had they been in service?) and installing a new meter could result in a higher bill if your old meter wasn't reading properly. It's not that anybody started charging them more, but rather, they lost the uncounted discount they were getting previously. The average homeowner has no idea what a kilowatt is or how their meter works, and your bill will never be the same month to month unless your power is switched off.

Back to the time of use issue, yes, they give discounts for night usage because the US simply doesn't have enough capacity during the summer to feed everybody. We import electricity from Mexico and Canada. This is why California and other places have blackouts and brownouts. Time of use metering was offered long before smart meters came along. This is much less of an issue in North Carolina, for that matter the lake I live on is one of the largest hydro power sources in the country...but it's still bad for the power company to have high use during the day and low usage at night. Everything runs most efficiently when the usage remains mostly average.

It *IS* possible for a smart meter to use power factor correction and charge you more, but, I'm not aware of a single power company doing this, and, they're still only charging you for the power you used. They just couldn't measure that part before. It only makes sense that in 2019 we have digital meters, just like every other kind of meter. Why should we be using technology from the early 1900s? Because some weirdo on the internet told you the new thing is bad?

[Vance357]

How efficient are we talking with propane?  I looked hard into geothermal with a cop of 4 as the very best.  Can you beat that?  That would be awesome and you would have me dreaming up more projects.

You may want to run brine on the cold side.  The evap coil will freeze water pretty easily.

Geothermal with propane will certainly be more efficient than geothermal with R410 or some of the new stuff that is even higher pressure. You shouldn't really use it in a system where the refrigerant is pumped into an indoor air handler, if the propane leaks that could be very bad. An interesting side effect of the line filters used on A/C equipment is that they will remove the scent from propane, and you'll never know it is leaking.

If the refrigerant coils/compressor are entirely outside and thermal energy transferred by water, then it's not that big of deal, very unlikely to cause an explosion or fire.

[MagnetJuice]

Vance357 said:

You shouldn't really use it in a system where the refrigerant is pumped into an indoor air handler, if the propane leaks that could be very bad.


Vance357, I'm glad that you said that. I have been following this thread and I was afraid that someone reading this who is unfamiliar with the dangers of explosive hydrocarbons, would think that it is OK to replace the refrigerant in their air conditioner with propane.

If that propane is indoors and there is a leak, that gas goes to the bottom of your floor because propane is heavier that air. It stays there until there is a spark to create a KABOOM!!!

I don't need to say anything else. To those reading this, just know what you are doing and be very careful.

Ed

[joestue]

R410 is a few percent worse thermodynamically than r22 but at practical/reasonable power densities, its lower viscosity and higher thermal conductivity make it more efficient... in household sized air to air heat pumps.

For geothermal you have massive heat exchangers usually, if you have it setup that way. If you are pumping glycol and have a small heat exchanger, r410 may be better than propane

[Vance357]

R410 is a few percent worse thermodynamically than r22 but at practical/reasonable power densities, its lower viscosity and higher thermal conductivity make it more efficient... in household sized air to air heat pumps.

For geothermal you have massive heat exchangers usually, if you have it setup that way. If you are pumping glycol and have a small heat exchanger, r410 may be better than propane

Thats why I call this an ongoing experiment, I'm sure I will be playing with it for a while with different refrigerant charges, compressors, coils, etc. Will probably use two compressors, a smaller one and a larger one, and/or VFD to control speeds. I might try an open loop geothermal system where I just use my well water to cool it, but I'd have to balance the cost of running the well pump vs fans or whatever. Also considering closed loop with underground coils, it would be a lot of work but I have a buddy with a tractor I can use for trenching. Using water will make it easy to calculate BTU outputs.

I suppose I'm better off to keep the "hot" water as cool as possible, just store more of it. The hotter it gets, the more watts the compressor will use. Something just above shower temperature would work, maybe with a small booster under the kitchen sink for hotter water.

Also considering a stainless steel 55 gallon drum or two to keep really hot water in, like might come from a wood fired source. They're not cheap, but should last the rest of my life...

Not an HVAC tech but I have stayed in numerous holiday inns. 

[MagnetJuice]

Holiday Inn Express that is.

Younglings don't know what that is unless they've seen it on yourtube, or theirtube. I don't have a tube, but when I grow up I want to have a tube. A big tube. I don't know what I'm going to call it yet.

[DamonHD]

Completely agree with all of the above.

Another big reason for ToU charging in the UK is to try to eliminate the need to send actual people out to read meters, and the mess that comes from estimated usage when that can't happen.

(For example, a professional female friend for mine is always at home on her own when the meter readers happen to call.  Legally a meter reading has to be taken every year or two, but clearly the single male reader knows perfectly well why my friend doesn't want to let him in.  The CEO of the energy company is also understanding when I have discussed it with him.  I'm sure my friend supplies good readings over the phone, but everyone is breaking the law here.  The current system is expensive and doesn't work very well in places.)

I was actually asked by the UK's energy minister and his chief scientific advisor to look at some smart metering issues and I am as sure as I can be from hearing what *did* worry them (and what I said afterwards was going to suck about them) that hiking charges is absolutely NOT what they had in mind.

Rgds

Damon

[Mary B]

My bill spiked up 30%, old spin meters couldn't measure power factor, smart meters can and it increases the bill.

[DamonHD]

UK domestic smart meters continue to measure and bill for real power, no pf, just like the analogue ones.

Rgds

Damon

PS. Note also that EU domestic appliances now generally have to have by law a power-factor very close to 1, so that even if such a change happened the chance of a nasty billing surprise is low.

[Vance357]

UK domestic smart meters continue to measure and bill for real power, no pf, just like the analogue ones.

Same in the US. Anybody that thinks their bill went up simply doesn't understand how it works. Or their 30 year old antique meter wasn't reading properly and got changed out for one that did.

It's possible with smart meters in the future they could charge for power factor, but they are NOT currently doing this anywhere.

Here in NC state law requires an option to opt out of the self reading meters, however, you still get a digital meter, not an old spinning meter. They just have to send somebody out to read it and now everybody has to pay more because you're paranoid...

I strongly encourage anybody who thinks their smart meter is charging them more to install a standard old style spinny meter directly after your PoCo meter. The numbers on both meters will agree. You can buy an old style meter on ebay for almost nothing. If the meters don't agree, now you can call the power company, the news, your lawyer, and the tinfoil hat society and show them proof of what you say.

While we're talking about it, I do plan installing an individual digital power meter for most of my larger power circuits, so I can easily monitor independently what the well is using, the heat pump, water heat, etc.