Will this heater idea work

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Will this heater idea work

This topic has 48 replies, 20 voices, and was last updated 26 September 2023 at 21:19 by DMB.

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22 September 2023 at 12:13 #661047
Andrew Smith 16
Participant
@andrewsmith16
Dear all

We tend to retrench to a small room in the house during winter months and have been pondering a low cost way to warm the room effectively without having to ramp up the gas central heating system.

Confident of my genius I have been scribbling ideas down but, as ever, I don't actually know what I am doing so before getting out the welding gear and investing in a solar panel I thought I'd seek some opinion. One of you guys will have thought of this already, or will have done it or something similar. Is it worth the effort?

The idea – internet abounds with 12V 200-300W immersion heaters (for cars or caravans??) and solar panels capable of producing that sort of of output. Some of the immersion heaters look essentially like kettle elements and some are totally enclosed in stainless steel tubes but cost is typically 20 to 30 pounds.

The solar supply options seem to be about 60 to 100 pounds including some sort of supply interface gizmo but, to my understanding, while the sun shines they spit out the required 12V and 300W.

If I was to weld, say, a 2" diameter steel tube within a small-ish 8kg propane cylinder full of sand would the heater transmit enough heat to create an overnight heat source? Some comments suggest don't let the immersion touch the sand or jacket it with water. I'm clueless but was aiming for a totally dry set up.

Hoping for something more effective than tea lights under a plant pot and the steel casing could/might allow for an easy increase in surface area by addition of fins or whatever. A guy on youtube has offered a design using a sand filled pipe heated by tea lights with the fumes vented through a charcoal filled chimney. I am not massively keen but if the floor decides that is better than the solar option I could go down that route.

Intention would be a discrete solar panel in the garden and a cable to the heater. No other items to be connected bar maybe some led lighting.

Am I being stupid? Might this work? I don't need fabulous levels of efficiency and am not after 1000C and enough energy to warm Finland or wherever the big boy version is. I am really only after a basic pot belly stove effect. Would this get to, say, 50C assuming decent sunshine? Would that heat a 15ft by 10ft room?

As a minor aside I had also thought about an additional hole to receive a simple billet that would be heated whenever the oven was used and transferred. Rather like heating a brick by the fire and taking it to bed (was that only us?). That would allow some sort of occasional top up.

If the approach is nonsense feel free to say so. I can take it! No experience of solar panels. Dubious welding ability. More reasons not to try than to attempt it – I could be working on that traction engine.

Andrew
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22 September 2023 at 12:13 #37366
Andrew Smith 16
Participant
@andrewsmith16
A solar powered sand reservoir for a small room
22 September 2023 at 12:21 #661049
Benedict White
Participant
@benedictwhite51126
They are trying it in Finland as you suggest.

Sand is useful because it can hold heat because it doesn't transmit it.

The issues are:

1 Getting the heat in.

2 Getting the heat out.

To do this you will need to run pipe in the sand from your immersion heater to warm it.

Run another circuit in sand to extract the heat.
22 September 2023 at 12:27 #661051
Tony Jeffree
Participant
@tonyjeffree56510
A couple of points…

Running immersion heaters of any kind without a water jacket is asking for trouble – they are designed on the assumption that they will be in contact with water and will potentially overheat if they are not.

Heating up a brick in your oven simply increases the amount of time it will take for the oven to heat up – there are no free lunches there I'm afraid.

If you get 300W worth of sunshine during the winter months (very far from certain I'm afraid), the best you will manage is about a couple of units (1 unit = 1 killowatt-hour) of stored heat – so equivalent to having a convector heater on for about an hour. Bear in mind that the heat will be given out over the full 24 hours. I doubt if you would see much benefit TBH.
22 September 2023 at 12:44 #661052
Robert Atkinson 2
Participant
@robertatkinson2
+1 on Tony's comment on using immersion elements without water. They are designed for fast heating so need the water to control the temperature.

Another issue is that solar cells don't work well with fixed resistance loads. For your sand heaters idea you could use some MOSFETs on a heatsink in the sand and a maximum power point tracking (MPPT) controller.
BUT
You would probably be better off using the solar cells to charge a 12 or 24V battery and then running a car or truck fan heater off the batttery when you actually need heat.

Robert.

Edited By Robert Atkinson 2 on 22/09/2023 12:44:55
22 September 2023 at 12:58 #661055
HOWARDT
Participant
@howardt
Short of chopping up a tree with an axe there is no way to produce free heat. What needs to be done is reduce the heat loss as much as possible therefore reducing the amount of heat input to a minimum. All heat input costs money and in the UK even wood stove installation is controlled by local councils, not sure wether it is everywhere certainly is where I live. Without spending a great deal of money there is no way to heat most UK properties cheaply. I think the number of tea candles required to heat a room would cost far in excess of your normal electric supplier.
22 September 2023 at 13:00 #661056
Bill Davies 2
Participant
@billdavies2
If you considet the use of car batteries, calculate the tihe to run out of charge (battery amp-hours divided by current drawn). I ran down my car battery with one of those small 'fridge' coolers, which didn't have much current draw. A bit depressing when I went to retrieve my car later that evening, in the dark!

Bill
22 September 2023 at 13:08 #661060
duncan webster 1
Participant
@duncanwebster1
I wouldn't use car batteries, they don't like deep discharge, Leisure batteries are the thing. As others have said, 1 300W solar panel won't give anything like that on an overcast winter's day, and it's only daylight for around 8 hours per day in midwinter.
22 September 2023 at 13:27 #661061
John Haine
Participant
@johnhaine32865
A data point. We have a modern large storage heater in our kitchen/diner which is heated at night probably for 4 hours from cold consuming 3kw, so total of 12kwh. That keeps background heat in the room until evening. You might use one a third the size for a small room so 4kwh. I don't think a 300w solar panel will cut it in winter daylight.
22 September 2023 at 13:57 #661067
Andrew Smith 16
Participant
@andrewsmith16
Many thanks to you for the learned insight. I'll save my money for something more sensible.

Always grateful to have access to the combined knowledge on this site…
22 September 2023 at 15:26 #661074
Steviegtr
Participant
@steviegtr
If you look on youtube there a lot of folk who have fitted the chinese diesel heaters outside of there homes & ducted the warm air indoors with a lot of success. I fitted one to my workshop (i wont put a link to the video on utube ) But it's there. My workshop is 3M x 4M & it gets toasty warm in winter. I spent a total of £42 throughout winter on diesel. That was paying top price for fuel. I have since found the local flying club sells Kerosene much cheaper.

It is an alternative that works & a lot of forum members on this site use them i discovered.

These are what are fitted to most Campervans.

Steve.
22 September 2023 at 15:29 #661075
Macolm
Participant
@macolm
Bear in mind that a given solar panel in December will produce roughly one sixth of the mid summer output.

By the way, an excess of solar generation sounds like an excellent way to destabilise the electricity grid, since the plan seems to be to mandate heat pumps, whose COP will be a minimum at the same time as the solar output is also a minimum.
22 September 2023 at 16:04 #661077
Robert Atkinson 2
Participant
@robertatkinson2
Posted by Steviegtr on 22/09/2023 15:26:10:

If you look on youtube there a lot of folk who have fitted the chinese diesel heaters outside of there homes & ducted the warm air indoors with a lot of success. I fitted one to my workshop (i wont put a link to the video on utube ) But it's there. My workshop is 3M x 4M & it gets toasty warm in winter. I spent a total of £42 throughout winter on diesel. That was paying top price for fuel. I have since found the local flying club sells Kerosene much cheaper.

It is an alternative that works & a lot of forum members on this site use them i discovered.

These are what are fitted to most Campervans.

Steve.

NO NO, Hell NO!!!!!

These chinese diesel heaters are not well made, are not intended for use in dwellings and are not approved for this type of use. Most of them are not properly approved for ANY use. If it burns the house down you will probably find you insurance was invalidated by usin one.

Additionally Steve, assuming that the "kerosine" you bought at the flying club is aviation fuel, you have just admittedt to fuel duty fraud on a public forum. I can't see why you would by any other kerosine from a flying club. It is also illegal for them to sell it to you.

In contrast I buy Jet-A for my gas turbine engine from a responsible supplier and have to pay the full rate of duty. In theory as I'm using it to test an aircraft engine it should be duty free but the supplier, quite reasonably in my view, say that ANY sale that does not go into a aircraft or ground support equipment on the airfield is charged at full duty. The small number of sales is not worth the effort to ensure that it is not duty evasion given the consequences to their business if it is. If I don't like It I can go elsewhere as far as they are concerned.

Robert.
22 September 2023 at 16:09 #661079
Michael Gilligan
Participant
@michaelgilligan61133
Years ago, in a TV series … Dick Strawbridge showed a thermal energy store using a pit full of crushed glass

But I think it was only supplying night-time warmth for his greenhouse

MichaelG.
22 September 2023 at 16:18 #661081
Benedict White
Participant
@benedictwhite51126
If you intend on buying kerosene or red diesel, buy it from a petrol station that sells it. You do have to fill in a form. Using it for heating is a permitted use. (For either red diesel or kerosene). About 80-90p a litre.
22 September 2023 at 16:19 #661082
Steviegtr
Participant
@steviegtr
Posted by Robert Atkinson 2 on 22/09/2023 16:04:12:

Posted by Steviegtr on 22/09/2023 15:26:10:

If you look on youtube there a lot of folk who have fitted the chinese diesel heaters outside of there homes & ducted the warm air indoors with a lot of success. I fitted one to my workshop (i wont put a link to the video on utube ) But it's there. My workshop is 3M x 4M & it gets toasty warm in winter. I spent a total of £42 throughout winter on diesel. That was paying top price for fuel. I have since found the local flying club sells Kerosene much cheaper.

It is an alternative that works & a lot of forum members on this site use them i discovered.

These are what are fitted to most Campervans.

Steve.

NO NO, Hell NO!!!!!

These chinese diesel heaters are not well made, are not intended for use in dwellings and are not approved for this type of use. Most of them are not properly approved for ANY use. If it burns the house down you will probably find you insurance was invalidated by usin one.

Additionally Steve, assuming that the "kerosine" you bought at the flying club is aviation fuel, you have just admittedt to fuel duty fraud on a public forum. I can't see why you would by any other kerosine from a flying club. It is also illegal for them to sell it to you.

In contrast I buy Jet-A for my gas turbine engine from a responsible supplier and have to pay the full rate of duty. In theory as I'm using it to test an aircraft engine it should be duty free but the supplier, quite reasonably in my view, say that ANY sale that does not go into a aircraft or ground support equipment on the airfield is charged at full duty. The small number of sales is not worth the effort to ensure that it is not duty evasion given the consequences to their business if it is. If I don't like It I can go elsewhere as far as they are concerned.

Robert.

Oh Dear.
22 September 2023 at 16:37 #661083
Steviegtr
Participant
@steviegtr
Posted by Benedict White on 22/09/2023 16:18:37:

If you intend on buying kerosene or red diesel, buy it from a petrol station that sells it. You do have to fill in a form. Using it for heating is a permitted use. (For either red diesel or kerosene). About 80-90p a litre.

I tried that last year. Red diesel is what I was using. It was not much cheaper. From the higher up posting it seems the flying club may not let me have any. There is a place at Brighouse not too far from me that does sell Kerosene in small amounts . Most want you to buy 400 litres at a time. I should only need around 50 Litres for the winter.

Steve.
22 September 2023 at 16:48 #661085
Robert Atkinson 2
Participant
@robertatkinson2
Posted by Benedict White on 22/09/2023 16:18:37:

If you intend on buying kerosene or red diesel, buy it from a petrol station that sells it. You do have to fill in a form. Using it for heating is a permitted use. (For either red diesel or kerosene). About 80-90p a litre.

Correct. The problem with Aviation fuel is that it is not marked (dyed) so they can't easilly tell if it is used in a road vehicle (highest taxation class). This means there are stricter regulations and controls on it.
The reason it is unmarked is because the marker could interfere with correct operation of the aircraft systems. Even if it didn't the specifications for the fuel do not allow the addition of markers.

The laws were changed fairly recently with more restrictions on reduced duty fuel. You can no longer use it in transport refrigeration units and pleasure boats can only claim a rebate for the portion of fuel used for heating rather than propulsion.

Robert.
22 September 2023 at 16:48 #661086
Benedict White
Participant
@benedictwhite51126
Steviegtr, I live in a semi rural area where we have petrol stations which serve the farming community and have pumps for red diesel and kerosene. You know have to fill in a form first giving your address and what you are going to use it for.
22 September 2023 at 16:52 #661087
Benedict White
Participant
@benedictwhite51126
Posted by Robert Atkinson 2 on 22/09/2023 16:48:01:

Posted by Benedict White on 22/09/2023 16:18:37:

If you intend on buying kerosene or red diesel, buy it from a petrol station that sells it. You do have to fill in a form. Using it for heating is a permitted use. (For either red diesel or kerosene). About 80-90p a litre.

Correct. The problem with Aviation fuel is that it is not marked (dyed) so they can't easilly tell if it is used in a road vehicle (highest taxation class). This means there are stricter regulations and controls on it.
The reason it is unmarked is because the marker could interfere with correct operation of the aircraft systems. Even if it didn't the specifications for the fuel do not allow the addition of markers.

The laws were changed fairly recently with more restrictions on reduced duty fuel. You can no longer use it in transport refrigeration units and pleasure boats can only claim a rebate for the portion of fuel used for heating rather than propulsion.

Robert.

Kerosene isn't marked. It also looks like and smells a lot like diesel. (It will ruin a diesel pump and injectors if you use it for such though).
22 September 2023 at 16:55 #661088
Steviegtr
Participant
@steviegtr
Posted by Benedict White on 22/09/2023 16:48:21:

Steviegtr, I live in a semi rural area where we have petrol stations which serve the farming community and have pumps for red diesel and kerosene. You know have to fill in a form first giving your address and what you are going to use it for.

Last winter I rang all the local to me stations & none sold Kero. Some had done but no longer did. I will try a few more just to see.. Thanks for the info though.

Steve.
22 September 2023 at 17:36 #661095
SillyOldDuffer
Moderator
@sillyoldduffer
The amount of heat needed depends on room size, how well insulated it is, and how warm the occupant wants it to be. In a typical UK home, between 1500 and 8000 BTU. A heating engineer typically puts the biggest radiator in the living room (a large room we like to be cosy in), and a small one in cool places like hallways and workshops.

If Andrew's room has a 10 foot ceiling, he's looking to heat a space of 1500 cubic feet. With poor insulation, this will take about 8000BTU. 8000 BTU is equivalent to about 2.3kW, so a 300W solar panel or several tea-lights won't touch the sides. Frost protection rather than comfy.

Difficult to beat gas central heating on cost if the goal is to save money. That suggests the answer is to run the central heating system with most radiators switched off. Insulation makes a big difference, as does facing south. Avoid serious leaks like chimneys and patio doors.

Health permitting it may be possible to reduce temperatures in the home significantly. In winter I run my heating for only 6 hours a day at up to 18°C in the hottest room. I dress warmly. Got used to it and now I find buildings warmer that 18°C downright uncomfortable!

An electric radiant heater might be the answer. They throw heat at people rather than warm the whole room up, and then people don't notice it's cold until they move. Arguably a better way to use a small amount of heat. Foot warmers work in the same way – heat where it makes the body happy.

Dave
22 September 2023 at 17:44 #661097
duncan webster 1
Participant
@duncanwebster1
We have a high efficiency gas fire (balanced flue) in the room we use most. It claims 90% efficiency. Central heating goes on for a short time each day in really cold weather just to take the arctic chill off the rest of the house. I agree with SOD, if you put a jumper on 18C is plenty warm enough. I also wear my woolly hat, but then I'm bald on top so lacking insulation.
22 September 2023 at 18:01 #661103
Robert Atkinson 2
Participant
@robertatkinson2
Posted by Benedict White on 22/09/2023 16:52:00:

Posted by Robert Atkinson 2 on 22/09/2023 16:48:01:

Posted by Benedict White on 22/09/2023 16:18:37:

If you intend on buying kerosene or red diesel, buy it from a petrol station that sells it. You do have to fill in a form. Using it for heating is a permitted use. (For either red diesel or kerosene). About 80-90p a litre.

Correct. The problem with Aviation fuel is that it is not marked (dyed) so they can't easilly tell if it is used in a road vehicle (highest taxation class). This means there are stricter regulations and controls on it.
The reason it is unmarked is because the marker could interfere with correct operation of the aircraft systems. Even if it didn't the specifications for the fuel do not allow the addition of markers.

The laws were changed fairly recently with more restrictions on reduced duty fuel. You can no longer use it in transport refrigeration units and pleasure boats can only claim a rebate for the portion of fuel used for heating rather than propulsion.

Robert.

Kerosene isn't marked. It also looks like and smells a lot like diesel. (It will ruin a diesel pump and injectors if you use it for such though).

Unmarked kerosine is sold at the full rate of duty.

Robert.
22 September 2023 at 20:15 #661118
Bazyle
Participant
@bazyle
Most of the adverts for '200w solar panels' on ebay won't even produce 10W if you work out the area of them. I don't know how they are allowed to get away with such lying. In theory you can get about 200W/m2 at midday, but probably not.
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