Project Hot Box

If you have no other choice you can provide some heat using something called thermal mass and this is basically heating something up which holds the heat and releases it slowly and concrete, bricks, tiles, and most masonry are thermal mass as they can be quickly heated up and release heat slowly over a long period of time and this is what we need. Is this proven? Actually yes as the old electric storage heaters used this principle to provide heat for a long period as they used an electric heating element in an oil filled chamber filled with rocks and the element heated the oil which in turn heated the rocks and this was done overnight on cheap rate electricity called Economy 7. Early models used low powered heating elements which were switched on using a timer and they stayed on overnight for several hours and just before Economy 7 ended it switched them off again and the oil was heated up for a long period and heated the rocks. Later versions were thermostatically controlled and the heating element was larger and consumed more electricity and heated up much quicker and once to temperature, switched off again and kept switching on just to keep the oil at temperature and these later models were much more efficient and used less than half the electricity.

Now we have our three elements; heat, thermal mass, and a container to hold it all.

If we have a fire we have heat and if we have decent sized rocks, bricks, or other thermal mass we have the means to provide heat for hours and if we have a metal container we can hold the rocks as metal is a conductor and emits the heat.

This can work simply and you can modify my suggested idea to suit your requirements and I would begin with a concrete slab in your room at floor level as heat rises and place a brick under each corner and one in the middle so your slab sits on them and this gives convection currents of heat and a gap underneath your slab.

Take your bricks or other thermal mass and put them on the ground or in a pit and make a fire on them and in around 30-60 minutes they will be increasingly hot and if you catch them at the peak of their heat and put them in a metal box which is sealed they will emit lots of heat over hours, so put them into your metal box and ensure nothing else enters as it may burn and smoke. Fit a removable handle to your box and carry it inside and place it onto your concrete slab with a leather gauntlet on and it will emit heat for a long period of time and the larger the thermal mass, the more heat it will emit. Can you use only one container? No as you can use as many as your concrete slab will hold and if you light your fire outside two hours later than your first fire you can heat a second wave of rocks and put them alongside your already heated rocks which will be cooling by now and keep your heat going; or you can fill more than one box and put them all on your concrete slab and you will have a lot of constant heat.

Thanks again Assassin.