Lister Engine Forum

How to / DIY => Everything else => Topic started by: veggie on July 21, 2022, 03:30:06 AM

Title: Heat sand to 400F
Post by: veggie on July 21, 2022, 03:30:06 AM
I'm looking for ideas.
I can only heat stored water to 212f, but sand can be heated to to 800 degrees and used as a thermal battery.
I don't want to go as high as 800 yet, but I would like to fill a steel tank (maybe 50 gallon size) an try to heat it to 400f.
Then insulate it just enough to still allow for heat to radiate for X number of hours.

Application: Run the lister for x hours to electrically heat up the sand to 400f.
Observe the system to see how long the system can heat the garage in winter.
Start engine .... heat sand ..... Start engine .... heat sand .....Start engine .... heat sand .....
Automate later.
Power the engine with waste oil.

Problem:
How to electrically heat the sand to 400f ????
Basic water heating elements will probably burn up.
I can provide 2kw to 3kw of electricity at 120 volts or 240 volts.

Any ideas for an electrical device to heat fully heat several hundred pounds of sand ?    ???
Title: Re: Heat sand to 400F
Post by: veggie on July 21, 2022, 03:56:17 AM

... Was thinking 3 or 4 of these placed at different levels in the media.
Title: Re: Heat sand to 400F
Post by: broncodriver99 on July 21, 2022, 04:00:35 AM
Calrod heater would work as well. Very similar material to what you posted but can be shaped. Sand has some insulative properties so multiple heating elements would likeky be necessary.
Title: Re: Heat sand to 400F
Post by: dieselspanner on July 21, 2022, 08:17:39 AM
Hi Veggie

Cheap and easy - along with 'low tech' a pair of my favourite words! - would be to run the exhaust through the sand.

I realise that it won't provide all the heat you need if your sand box was say a meter square a 75mm pipe in a 'square spiral' 600mm on a side with three turns or so would probably help.

If you cut the pipe wirh a chop saw into 600mm lengths with a 30 degree angle a hexagonal 'spiral' wouldn't be too hard to fab up....

Perhaps run top to bottom with a water drain for condensate, or just vent it at low level out the back of the shed, as a bonus, it shouldn't be too loud either!

A little scrounging at a recycling plant could well provide the raw materials and a little over basic welding skills would do it. It won't have to be pretty, just gas tight, and if it was a dead end the pipe can go back on the scrap heap and the cost would be some electrodes and time.

Just thinkin'

Cheers

Stef

Title: Re: Heat sand to 400F
Post by: veggie on July 21, 2022, 03:39:21 PM
Calrod heater would work as well. Very similar material to what you posted but can be shaped. Sand has some insulative properties so multiple heating elements would likeky be necessary.
Bronco,
I looked up Calrod Heaters. Yes, that would probably work well.
That looks like a good solution. Thanks  ;)
Title: Re: Heat sand to 400F
Post by: veggie on July 21, 2022, 03:44:47 PM

Spanner,
Good idea. In addition to the sand thermal heat store, I can also use the exhaust to additionally heat the same sand, or build a sand heat exchanger by running the exhaust pipe with multiple passes through another sand chamber.
If electrical AND exhaust heat can be captured, then the system efficiency will be exceptional, since I am already capturing the coolant heat and using it to heat the area via radiator/fan.
Title: Re: Heat sand to 400F
Post by: mikenash on July 21, 2022, 07:39:21 PM
Substances such as compacted sand, stone etc will have known properties - the rate at which they will take up heat; and the rate at which that heat will bleed out into cold air - dependant on temperature, ratio of exposed surface area to bulk - and so on . . .

I mention this because a technique widely used here is stone/concrete walls which are exposed to/heated by sunlight during the day - and which slowly release that stored heat at night.  Near me there's a community centre which has massive concrete heat sinks at the back of north-facing (southern hemisphere) rooms which do just that.  They're warm to the touch during the day - and still warm to the touch in the middle of the night.

Obviously it's a new build with good insulation and triple-glazing etc etc - but the point I make is that this is a case of a BIG mass being raised just a few degrees above ambient, then slowly yielding its stored energy back into the room.  SIZE/MASS is the key here.  because it's big - the temperature differential can be small but still work well

Maybe a LOT of sand . . .
Title: Re: Heat sand to 400F
Post by: ajaffa1 on July 22, 2022, 07:54:04 AM
Hi Guys, I hate to be a naysayer but what is the point? You are going to have to go through all the effort of filtering, de-watering and centrifuging your waste oil. You are then going to burn it in your Lister to produce electricity, which you are then going to use to heat sand or something similar.
Why not cut out all the effort and inefficiency not to mention wear on your Lister and generator head by building a smudge pot oil burner? They are easy to build, they will burn untreated oil and produce enormous amounts of heat. You could always encase the flue in some sort of thermal mass if you want.

Bob
Title: Re: Heat sand to 400F
Post by: dieselspanner on July 23, 2022, 08:51:20 AM
Hi Veggie

Interesting point Bob makes. I'd not considered it, but when you add that to Mikes comments and have more mass at a lower temperature you get to to about where I am in my barn.

It's a single open plan room, two floors high, 9m long x 5 m wide with a poured steel reinforced concrete floor that rests on 60mm of polystyrene insulation, the depth varies but it must be about 200mm on the average. On top of that is a screed with around 130m of 16mm bore plastic pipe (PEX) in 4 different runs, around the room, none of which is in the areas under the cabinets ect. on that is the flooring, 15mm of good quality concrete tiles (with a very realistic concrete floor

So, probably an eight cubic meters mass.

I ran it in the winter, of a wood burning Rayburn cooker, which was also supplying two large cast iron radiators, two bathroom type heated towel rails  and, with first call on the hot water, a 110 litre tank,

I ordered lots of aquarium type thermometers, with a 1m tail on the sensor (3/4 Euros each) and put them everywhere on the circuits so I could tell where the heat was going, not exactly, as I have no flow meters but enough to give me a good stating point for balancing the system. I also made great use of an infra red thermometer.

To cut a long story short I started with the building stone cold (February, - 10 degrees c outside, +2 inside - I was putting water under the at  +30 degrees c and at the return to the boiler it was coming out at 8 / 10 degrees c. after 3 days of day time running it was coming out at around 20 c

I moved in (a domestic rebellion by me.....) and after a week I was going to bed with the downstairs at 18 degrees ans upstairs in the bedroom part at 21.

By morning downstairs was around 12 / 14 degrees, still - 10 outside. Obviously the larger part of the rise in temperature was caused by the rest of the system.

A far smaller cube of sand at 400f - around 200c, and 10 times hotter than my floor slab would do it do it but you'd have something like a large piece of furniture in the room and have to have system for recovering and distributing the heat later.

I installed the underfloor heating to 'dump' remaining heat from the water rather than as a primary heat source and it's set up in such a way that should I get around to building a small hydro generator I have a dump for the power in the early morning hours when the batteries are topped up.

In conclusion, I'd say that if you wish to use electric to build up a store of heat then I'd look at an under system for the mass and lower temperatures. Not an easy thing to retro fit I know!

The one thing I have realised from this thread is that if I do another barn conversion involving a diesel generator the exhaust will be in a trench filled with concrete under the ground floor!

I hope this gives you some real world information to work with

Cheers
Stef
Title: Re: Heat sand to 400F
Post by: veggie on July 23, 2022, 03:04:43 PM
Hi Guys, I hate to be a naysayer but what is the point? You are going to have to go through all the effort of filtering, de-watering and centrifuging your waste oil. You are then going to burn it in your Lister to produce electricity, which you are then going to use to heat sand or something similar.
Why not cut out all the effort and inefficiency not to mention wear on your Lister and generator head by building a smudge pot oil burner? They are easy to build, they will burn untreated oil and produce enormous amounts of heat. You could always encase the flue in some sort of thermal mass if you want.

Bob

Hi Bob,

The Lister is already there. It sits idle waiting for a power outage, I don't see using it for garage heating and greenhouse lighting as a bad thing.
There is NO WAY I'm going to build an oil burner to leave in my garage unattended. I don't trust my Oil Burner building skills enough to go down that road which would also require chimney holes and stove pipes cut through the roof.   99% of the DIY oil burners I have seen on YouTube would never pass any kind of safety regulations.

Also, my wiring and cooling system is already in place. All that's needed is a sand reservoir and some electric elements.
The system I am pondering uses my operational machine that all is ready to go.
If I wait for power outages to use my system, it may still be like new 20 years from now   :)  so it could now earn it's keep by offsetting the current heating costs.
And when winter temps here in Canada dip to -25C, it could make a substantial difference according to my calculations.
Using the cooling system, generator (sand heat) and possibly capturing some exhaust heat in a heat exchanger, the system may approach 70% in thermal efficiency.
This project does require further research and it would not be difficult to program a model where different amounts of sand and different bed temperatures can be tried in order to get the optimal reservoir size.
If the res is too big, the Lister has to run too long to get it up to temperature.
If it's too small, the res looses most of it's heat too soon causing excess engine run cycles.
So the goal here is to have the Lister run 4 hrs in the AM and 4 hrs in the late PM.
Who knows, maybe the model will show that the number don't work. But if they do work, I am interested to build it.

Title: Re: Heat sand to 400F
Post by: ajaffa1 on July 24, 2022, 10:35:47 AM
Hi Veggie, I wasn`t aware where you live. Minus 25 in winter is seriously cold, where I now live, we hardly ever get a frost. I used to be an extreme skier and have experienced temperatures below minus 40 centigrade. The water on your eyeballs start to freeze over at between minus 25 and minus 30, makes for serious visibility issues, the faster you are going the worse it gets!
My initial thoughts were that you should fit a reverse cycle heat pump but that is never going to work with outside temperatures that low.
Another option would be a ground source heat pump but these are very expensive and cost a lot to install.
Going back to my skiing days, I spent a lot of time in Austria where a lot of bars and restaurants are heated by a thermal mass heater. These look like and are the same size as a wood fired brick pizza oven without any openings. I have no idea as to how they are heated but I would guess they are connected to a boiler of some sort. They have an surface temperature of around 30 centigrade and usually have a round seat built around them so tired skiers can warm themselves.
So going back to your idea, I think it could work but I am worried about how many electric heating elements you are going to burn out trying to get this to work. Back in the 1970`s electric night storage heaters were all the go. These had electric elements cast into concrete, with a fan blower to distribute the heat when you needed it. They were very heavy and not very efficient. If you could find a whole lot of them in a junk yard you could probably stack them, wire them and bury them in sand or gravel.
Looking forward to what you come up with.
Bob
Title: Re: Heat sand to 400F
Post by: veggie on July 24, 2022, 03:32:50 PM
Bob,
Yes, your comment about elements burning out is well noted.
I was thinking it may be necessary to control the ramp-up of the heating time so that the sand has a chance to absorb the heat from the elements.
Something like low frequency Pulse Width Modulation using a relay. (On..off..on..off..on..off).
If the elements cannot shed their heat fast enough (as they would in water) then they may fail.
So I have to do more research on what methods are available to heat sand with electricity.

cheers
Title: Re: Heat sand to 400F
Post by: veggie on July 24, 2022, 03:58:22 PM
I came across these heating strips which look interesting.
They are made by Wattco.
240 VAC
750 watts
Max. Temp of 1000F
Length = 23"

So 3 or 4 of these would use the 2250 to 3000 watts from a listeroid.
Title: Re: Heat sand to 400F
Post by: ajaffa1 on July 25, 2022, 11:54:50 AM
Hi Veggie, been thinking about your project today, rain stopped me doing what I had planned. I quite like the look of those heating elements but I have grave doubts about how you are going to safely connect this to the electric supply. At the temperatures you are seeking to achieve the insulation on the feed wires will melt with catastrophic results. To make this work you are going to need custom made ceramic insulators which could be expensive.
I did come up with a simple way to make a test rig, if you go to your local scrap metal merchant or council tip, you should be able to find and old air compressor cylinder. These come in many different sizes, you should be able to find one that will easily contain one or more heating elements. Find a safe way to fit the elements then cut a hole in the top and fill it with sand, cover the hole with a piece of steel and weld/screw it in place. Do not try to achieve a perfect seal, we do not want to build a pipe bomb! It is vital that steam from wet sand and the any rise in internal air pressure can escape.
If the experiments work out you could probably build bigger units using steel hot water cylinders.
I still think you are out of your mind, I`d be going for a thermal mass chimney system and smudge pot oil burner, but what do I know? Good luck and keep us informed.
Bob
Title: Re: Heat sand to 400F
Post by: veggie on July 25, 2022, 03:29:44 PM
ajaffa1,
Hi Bob, thanks for the suggestions.
I have 20 gal and a 60 gal compressor air tanks.
They both have threaded connections added for heating elements.
Was planning to use the smaller one first.
Title: Re: Heat sand to 400F
Post by: veggie on July 25, 2022, 04:56:19 PM
*** PROJECT CANCELLED ***

After modeling the idea, the numbers do not make sense for a micro system.

Summary....
==========

Specific Heat:
Water = 4182
Sand = 830
Sand holds only 20% of the BTU content capability of water for a given volume.

Raising a 50 gallon tank of water from 68f --> 180f requires ~46,725 BTU's
To store the same amount of heat in 50 gal of sand would require a temperature rise of approx. 900f

Heat transfer factor
Water = 13
Sand = 0.06
Roughly 200 times slower transfer rate in sand. (It holds heat very well ! )
But heating the sand bed would take a considerable amount of time.

So how do the new commercial sand heat storage systems get around these obstacles.
1] They heat the sand to 1800f or more by circulating molted nickel or molten salt through exchanger tubes in the sand bed.
2] With super high differential temperatures, they can rob heat from the bed at greater rates than my proposed 400f project.

For smaller heat reservoir systems water in king. It has the highest specific heat value and storage properties of any readily available media.

Title: Re: Heat sand to 400F
Post by: veggie on July 25, 2022, 06:57:34 PM
"I`d be going for a thermal mass chimney system and smudge pot oil burner, but what do I know? Good luck and keep us informed. Bob"

Hi Bob,
The biggest issue I have with used oil heaters is that everything I have seen on youtube has been cobbled together with metal scraps. The units glow cherry red when running, and don't have any form of safety shutdown incorporated. They look fine as experiments, but running one in a garage every day (winters) in a residential area looks risky.
I would love to build a small (20K BTU) oil burner system if I could find a reliable and safe design to follow.
If anyone knows a good forum on this subject, or a good design example, please post it.
Title: Re: Heat sand to 400F
Post by: dax021 on July 26, 2022, 04:31:33 PM
Contact He Who May Not Be Named    (Rhonda & David Smith [glort@hotmail.com])  He had some awesome burners going
Title: Re: Heat sand to 400F
Post by: mikenash on July 26, 2022, 07:38:55 PM
"I`d be going for a thermal mass chimney system and smudge pot oil burner, but what do I know? Good luck and keep us informed. Bob"

Hi Bob,
The biggest issue I have with used oil heaters is that everything I have seen on youtube has been cobbled together with metal scraps. The units glow cherry red when running, and don't have any form of safety shutdown incorporated. They look fine as experiments, but running one in a garage every day (winters) in a residential area looks risky.
I would love to build a small (20K BTU) oil burner system if I could find a reliable and safe design to follow.
If anyone knows a good forum on this subject, or a good design example, please post it.

I know a little bit about drip-feed and other low-tech oil-burners.  I have made six or eight prototypes and currently have one running.  My short conclusion is that they aren't safe for unattended running and that the only reason I'm happy to have one running in my shed is that it has a small oil reservoir and sort of a "bund" (four or five times the capacity of the reservoir) on top of a concrete hearth just in case it has a brain fart & drops a half-litre of hot oil out the bottom

If you search online - there are good ones using dosing pumps metered by things like little arduinos, with thermostats, oil shut-off solenoids and the like.  BUT, I haven't seen one like this that runs reliably that doesn't use an electric fan . . .

In short I haven't seen one that is good and safe that doesn't have several moving parts

Good luck
Title: Re: Heat sand to 400F
Post by: dieselspanner on July 29, 2022, 07:17:37 AM
Hi all

There might still be a little bit left in the project.......

If you built a 'reservoir' of concrete blocks, laid dry, along on wall, say 6' long x 4' high x 2'thick, run the exhaust through it 2 / 3 times, fill the blocks with sand and insulate the back, ends, top and bottom with a few slabs of polystyrene, you'd have something very similar to the old 1970's storage heaters.

Relativity cheap to build, free to heat, and run. If it didn't work out you could take it apart, buy a bag of cement and make a coal bunker!

It would depend on the layout of your workshop / garage and how many hours a day you ran the genny but there might be something in it.

Cheers
Stef

Title: Re: Heat sand to 400F
Post by: ajaffa1 on July 29, 2022, 08:40:24 AM
I still believe it is possible to build a safe waste oil burner. Many years ago I installed and commissioned a series of steam boilers that ran on diesel or kerosene. They were used to heat huge vats of pig swill that was then pumped to 5000 hungry pigs. These boilers had a fuel tank with a spring loaded shut off valve outside of the building. The valve was opened by a stainless steel wire with a very low melting point metal coupling in it. In the event of excessive heat/fire the coupling would melt and the valve would automatically close.

A second option would be to try and find a vaporizing oil burner out of an oil fired Aga, these are tricky to set up but once adjusted are pretty bomb proof, I ran one for years on all sorts of oils.

Failing all that you could contact Lord Volderglort and ask him how to make an oil burner that will heat a large mass of concrete or sand very quickly, so you can fire it up for 15 to 30 minutes while you are present and then turn it off. The thermal mass should keep you warm for a few hours and then you can fire it up again.
Bob
Title: Re: Heat sand to 400F
Post by: mikenash on July 30, 2022, 12:01:51 AM
I still believe it is possible to build a safe waste oil burner. Many years ago I installed and commissioned a series of steam boilers that ran on diesel or kerosene. They were used to heat huge vats of pig swill that was then pumped to 5000 hungry pigs. These boilers had a fuel tank with a spring loaded shut off valve outside of the building. The valve was opened by a stainless steel wire with a very low melting point metal coupling in it. In the event of excessive heat/fire the coupling would melt and the valve would automatically close.

A second option would be to try and find a vaporizing oil burner out of an oil fired Aga, these are tricky to set up but once adjusted are pretty bomb proof, I ran one for years on all sorts of oils.

Failing all that you could contact Lord Volderglort and ask him how to make an oil burner that will heat a large mass of concrete or sand very quickly, so you can fire it up for 15 to 30 minutes while you are present and then turn it off. The thermal mass should keep you warm for a few hours and then you can fire it up again.
Bob

See pic?  Crap image but the salient bit is the pipe that's glowing red hot.  It's either 150mm or 125mm (I forget which) and it's a mild-steel weld-bend with a 5mm or 6mm wall.  The burner heats it from ambient (maybe 6 degrees C in this case) to glowing in about ten mins using oil at the rate of maybe a couple of litres an hour?  It's about as safe as you're gonna get for a drip-feed with no moving parts that can be used domestically

I can send pics/details/plans if needed

Certainly if you extended that pipe by a couple of metres and put fins all over it and ran it through a bathtub full of sand . . .

Cheers
Title: Re: Heat sand to 400F
Post by: veggie on August 02, 2022, 07:04:52 PM
Thanks mikenash,

"Certainly if you extended that pipe by a couple of metres and put fins all over it and ran it through a bathtub full of sand . . ."

I think if I could build a reliable, small, safe waste oil burner, I would not need the sand at all.
Just run the burner constantly along with some safety shutdowns which cut the fuel supply if needed.
I do agree that  an oil burner/heater is the most efficient way to heat with used oil.
Also needed would be a method of rapid/easy cleaning since waste oil leaves a lot of ash and crap in the burn pot.

Does the burner in that picture have a forced air supply or is it self-drafted?

Title: Re: Heat sand to 400F
Post by: mikenash on August 02, 2022, 08:02:15 PM
Thanks mikenash,

"Certainly if you extended that pipe by a couple of metres and put fins all over it and ran it through a bathtub full of sand . . ."

I think if I could build a reliable, small, safe waste oil burner, I would not need the sand at all.
Just run the burner constantly along with some safety shutdowns which cut the fuel supply if needed.
I do agree that  an oil burner/heater is the most efficient way to heat with used oil.
Also needed would be a method of rapid/easy cleaning since waste oil leaves a lot of ash and crap in the burn pot.

Does the burner in that picture have a forced air supply or is it self-drafted?

Hi Veggie

I'm keen on "keep it simple" so the burner has no fan.  Really, of course, the flue - which is about four metres long - is the secret to a good draft as you will understand

It's a lousy pic, sorry

The burn pot is just that, a stainless steel, copper-bottomed pot I bought for $2 at the Salvation Army store.  There is a couple of lugs sticking out above it, and a bit of 50X10 flat underneath it with a couple of 13mm holes that match the holes in the two lugs.  There are two shorth lengths of M12 galv rod & some nuts that run from the lugs down to the flat and hold the pot in place. 

The pot is perfectly-sized to fit into the O-ring groove of a NB200mm profile steel flange - so, as it sits up into the groove, it makes quite a good "seal" and is positively located.

I guess it takes about 2 minutes to take it off to clean (loosen the nuts, drop it down, slide it out).  Beneath the whole thing there's a giant stainless bowl about 500mm in diameter and about 200mm deep that just slides in and out.  It's both a "bund" and an easy way to catch any mess when it gets a scrape-out/clean.  I paid $15 for it on FB marketplace

There's no denying they are dirty, messy things

I have a couple of boxes of throw-away gloves and a few cans of brakleen - and I figure they're just the cost of running the thing.  Maybe $10 a month?

I'm fortunate in that I have a source of a great deal of "used" oil which is effectively "new" oil contaminated with metal particles but no combustion byproducts or random automotive fluids.  It's an industrial gear oil from a specific application.  If I let it stand in 200 litre drums for a year or two - then just the bottom few inches is sludge and the rest is effectively "clean" - so my fuel is 100% consistent, free, readily-available and as "clean" as it can be

FWIW I'm just making some changes to the design to improve the "cook-top" function of the top of the burner and to increase the size of the reservior to maybe two or three litres.  But I'd never leave it burning unattended

Happy to help with details or drawings if needed.  Cheers