Phase Change Thermal Battery Energy Storage

[@davidhickman3056]

I have a pot ( an old turkey fryer pot) of 40lbs of parafin wax on my wood stove in the shop. it takes about 8 hours to melt it and then takes about 24 hours to solidify and it is still above the ambiant temp for at least 48 hours from the last fire in the wood stove. I use it to balance out the temps over night when I let a fire die out.

[@SimpleTek]

very cool!!!!!!!! do you know how long a pot of just water would last? as comparison

[@Robertnight888]

Sounds great but what’s the fire risk ?

[@tecnology-today]

very interesting coment, but to be really useful I would like to know the ambient temperature , since te velocity of the "cooling" depends on it. Can you please share this info too?

[@xndrdvrs]

I have looked at this, but the problem is that the latent heat of parafin wax is actually not that large. Especially if you calculate per volume. I got a 60 kWh battery for an m3 of parafin wax. Compare that to what you get if you simply heat water to 90 C and use it until 50 C which is around 50 kWh for an m3 of water. Sure the parafin has the nice property of releasing its energy at around 60-70 C, but it is not as cheap as you think. If you want to scale up this system, it is way cheaper to just use a larger tank and water.

[@SimpleTek]

Can you suggest any other materials?

[@simonmasters3295]

I am with the original comment. The question, for me, is about the "cost" of insulating and moving the heat against a background of "minimising installation cost" to achieve ROI... That sounds complicated, and can be summarised as KISS

[@halfanacremom3967]

We have hot summers here in Virginia and cold winter! And the energy price is rocket high, thanks to all the wealthy politicians in DC. I always dream of storing in the energy in summer and use it in winter. Yeah definitely worth a try, I can even try that too!

[@SimpleTek]

Well said!

[@aleksandrsnaumovs4277]

Very much looking forward to the results

[@SimpleTek]

me too!

[@ryuuguu01]

Some numbers . Water's specific heat is 4kJ/kg per 1º. the energy to change water to steam is 2,548 kJ so to heat water from 36º -> 100º is 252kJ so it takes 10x as energy to boil it all away as to heat from 37~100. Now for paraffin wax to melt, depending on the wax, is around 250 kJ so each kg of wax is like heating water 60º. if you can heat the water from 50-> 80 then one kg of wax can store 2x the energy when it makes its phase change. the specific heat of paraffin is about 2kJ/kg per1º so going from 50-80 will store 0.5 as much energy as water for a total of 2.5x energy storage as water over this range. Is this worth the extra expense and handling? Where paraffin is very useful is if you have low-temperature range say 10º, that crosses the paraffin melting point, and is cheap over a long time. So for example a south-facing window with a black box filled with paraffin behind it. problem is this is a major fire hazard.

[@SimpleTek]

what about the non phase change energy in paraffin wax? you have to add the phase change to that for the total.

[@KingSteen]

Would using something like carnuba wax with a melting point of around 84ºC improve this at all or have I totally missed your point?

[@douglaspohl1827]

On demand hot water heater using a phase change material. Winner!

[@SimpleTek]

I'm making a test prototype soon!

[@Samuel-yi5eo]

Sous vide bags might work well to contain the wax. They work in hot water up to boiling and are flexible enough to contain any volume change

[@SimpleTek]

you mean vacuum seal bags?

[@Samuel-yi5eo]

@@SimpleTek That would be the one.

[@tecnology-today]

very exicting idea. My sugestion for the experiment is to use a common "oil radiator" used for house heating in winter (exchanging the oil by parafin wax). You can find it (at least in europe) at any shop for 50 euros (even better if you have an old one in the garage just taking dust ;-) . It is ready to work, and includes 1,5 Kw electric heater + termostat + safety temp cuttoff. The energy stored can be easilly measured and time-temp curve too. It can be sincronized with photovoltaic excedent production to store the excess collected energy keeping your PV panels at peak production! You can have individual energy batteries on each room instead a massive centralized expensive installation. My only question is: it it is so good and simple, why it is not sold in the shops?

[@SimpleTek]

Great information!

[@robcuthbert8257]

was there any consideration for hydrated salts mixed with mineral oil as a PCM storage fluid. Choosing optimal transition temperatures can smooth charge and discharge processes with multiple phase changes. These PCM(s) would be supported by sensible heat structures like ceramic tiles/plates. Looking forward to your observations.

[@SimpleTek]

No idea, sounds interesting

[@robcuthbert8257]

@@SimpleTek 'www.osti.gov/biblio/1468092' A paper about different PCM properties and costs (from 2018).

[@natsagnyamnamkhai749]

Fantastic thanks for letting us know what it is

[@SimpleTek]

You’re welcome

[@ing.pagano]

It's something that's always been lingering in the back of my mind... But I've never got to run the math to determine how much you would need

[@SimpleTek]

I’m going to do an experiment soon! Stay tuned

[@paksaoify]

Why not flip it? submerge a finned radiator or series of radiators in the wax then flow the hot water through the radiators. Maybe stacked aluminum flashing and pex? Aluminum for better transfer. Maybe could use perforated steel sheets since it's in wax not water. Do you know how far the heat will transfer in paraffin at a given temp? Do you need water you could use a canner and can paraffin, stack the cans then blow hot air through the stacked cans? Airs less efficient but it's just a thought. Looking forward to the next video on this.

[@SimpleTek]

we'll see when I make the prototype!!!!!

[@tobyneufeldt5763]

That would solve the problem of having to seal the wax into the aluminium cans & a cooling radiator has heat transfer fins which makes the heat transfer to the water from the wax more efficient. If you can repurpose an old water radiator, it may be more cost effective than adapting alumium cans?

[@sultanast]

Hi @Simple Tek, any update on this Phase Change Thermal Battery Energy Storage?

[@SimpleTek]

Hopefully next month!

[@djstraylight]

You ever try the experiment with parrifin wax? Seems like pouring the wax in the soda cans and then sealing them with silicon caulk would be pretty easy. Something like sealable glass jars would also be an option for keeping the wax contained.

[@SimpleTek]

Soon. I got the wax recently!

[@jimw125]

question? Is wax volumetrically stable. Isn't this the same wax they use in pistons for automatic vent openers because it expands? Would these containers break?

[@SimpleTek]

@@jimw125 I plan on using open cans to compensate

[@derektolley623]

IVT a German Company Have be selling a storage system which using Parifin Wax as a Phase Change chage material for at leasr ten years

[@SimpleTek]

Thank you I’m going to look into that! Never heard of them

[@ing.pagano]

Beware of thermal expansion, that could explode the cans if not accounted for

[@SimpleTek]

I’ve thought about that actually, I have the cans upside down with the tabs open and filled 4/5. Wax floats. That way it can expand and not destroy anything.

[@tobyneufeldt5763]

That solves the need to seal the wax into that cans, very clever.

[@BB-sm8ey]

Hi, did you ever conduct the aluminum can experiment? I couldn't find a video... Cheers!

[@SimpleTek]

Not yet but thank you for asking!

[@BB-sm8ey]

@@SimpleTek Looking forward to it!

[@user-vq4mt4zd4e]

great content thanks

[@SimpleTek]

Thank you for the kind words

[@timrothgeb416]

Using aluminum cans won't work very well because the thermal conductivity of paraffin is low which will make it hard to melt the center of the can. Your design should be a counter flow design with thin layers of paraffin. This will allow energy to be stored or extracted without having to change the flow arrangement. Also, remember to allow for the expansion of the paraffin which is about 10%.

[@SimpleTek]

What about red bull cans?

[@timrothgeb416]

@@SimpleTek They would be better and I haven't done any calculations but I think they would still be a little thick. My gut feeling is something no thicker than about a 1/2 inch. As you remove energy from the system the hardening paraffin will make it harder (slower) to get the energy out. Something like an auto radiator would be good but it is not set up for counter flow.

[@SimpleTek]

@@timrothgeb416 interesting… I disagree but we’ll find out and I appreciate the input

[@timrothgeb416]

@@SimpleTek disagree with what exactly?

[@Robertnight888]

How would you seal the coke cans and how full of wax

[@SimpleTek]

gravity upside down, and 5/6 full of wax

[@kelleymcbride4633]

Keep your hands in the dirt! 👨‍🌾🇺🇸🤙

[@SimpleTek]

One needs to keep their dirt warm in the winter when you live in Canada!

[@GoatZilla]

There's little point in doing this when you consider you could just collect a LOT of rainwater for free and then use a solar collector to heat it up. Run the cost calculations and they're not in the same ballpark; they're not even the same sport. The trick is insulating the container and then getting that heat to a heat pump.

[@SimpleTek]

It comes down to space, thus is more energy dense

[@GoatZilla]

@@SimpleTek Ah, OK then you want lithium ion batteries then.

[@SimpleTek]

@@GoatZilla space and cost

[@GoatZilla]

@@SimpleTek As soon as you factor in cost, paraffin is wiped out by water. This is the kind of thing you do if you happen to have a ton of paraffin laying around and don't know what to do with it. At best you'll get like 2-3x more density. The problem is getting the heat in/out of the paraffin. You can't physically move the paraffin across its useful range because of the phase change. That means you have to use a heat transfer fluid, which is an immediate penalty as you will require a larger temperature gradient in order to get anything done in either direction and lose effective range both ways. I don't think the paraffin will cool evenly either -- I think it will solidify from the outside-in and at that point essentially become its own insulator against the core. So you'll have heat trapped in there that not only can't make it through its own solid paraffin insulator, but it also can't make it across the heat transfer fluid. There go your dreams of 2-3x more density. With water, the transfer medium is the same as the storage medium. You pump it up to to a solar collector to heat it up, and then you pump it over to a heat pump to move the heat indoors. That right there is the answer, staring you in the face.

[@SimpleTek]

@@GoatZilla I’m address much of that in a future video actually

[@offgridwanabe]

Buy a thousand hot pockets warmers and boil them in solar heat then warm yourself in winter. They have a house size one in Britain.

[@SimpleTek]

Omg too funny

[@ing.pagano]

They are made of 14-hydrate sodium acetate, actually not so hard to obtain. I haven't done the math, but dissolving baking soda (sodium bicarbonate) in white spirit vinegar (6% acetic acid) should not be too far. It's even better than wax because it stores the phase change energy even at room temperature as a supercooled liquid, then releases it when you introduce a nucleation point for the cristallisation to begin. (Some more math needed to determine energy density and efficiency)

[@offgridwanabe]

@@ing.pagano Controlling the release for an amount needed is the major problem. Sunamp has a heat battery used in Britian.

[@ing.pagano]

You would need many small containers, with the ability to activate them individually as needed

[@SimpleTek]

@@ing.pagano or maybe wax in aluminum pop cans submerged in water ?

[@offgridwanabe]

Bees wax is cheaper and better look around you can get 25lbs cheap

[@SimpleTek]

Cheaper than paraffin wax???

[@offgridwanabe]

@@SimpleTek Bees wax is a byproduct of honey production some farmers will give it away

[@SimpleTek]

@@offgridwanabe good point

[@offgridwanabe]

@@SimpleTek Apparently the heat gain is also better than parafin

[@SimpleTek]

@@offgridwanabe interesting - there's actually two things to consider - the melting/freezing temperature point and the energy to achieve the phase change.

[@tobyneufeldt5763]

It would be interesting to find a low-cost material that would got though both phase changes (solid-liquid-gas) in the temperature range needed (20-90deg. C)

[@SimpleTek]

parafin wax

[@SimpleTek]

@Will Swift online!

[@douglaspohl1827]

@@SimpleTek Start with some Vaseline...

[@SimpleTek]

@@douglaspohl1827 lol