Induction v halogen

[otherclive]

Whilst the price per kWh of the various energy sources are of course important, but the way the energy is converted in to heat and its applied to the substance you want to heat is also very important.

With Gas rings (Nat Gas or LPG) to maximise heating efficiency you should carefully match the size of the flame to size of the pan. Having the fame turned up too high means there is an increasing amount of gas used that is effectively wasted as it pass up the sides of the pan/kettle. There will always be some hot bypass gasses which means efficency is low.

Similarly with Halogen and the earliest coiled contact elements, if you can see any of the halogen light or the contact surface of element, that mean heat produced in those visible areas is wasted.

Induction hobs react to the presence of the magnetisable base of a saucepan, and the energy is concentrated to it, so its less wasteful than almost any other system.

Just as an indicator, if you heat a pan of water, on an induction hob, you will see water vapour rising above the pan well before it actually boils. Put te same pan on a gas ring, and you will barely see any water vapour until its boiling. The reason is with an induction hob, the heat is only entering through the reaction of the pans bas to the hobs emitter, and there is very little warm air rising around the pan. This means the air around the top of the pan remains considerably cooler which allows water vapour to form into its visible phase much sooner.

Gas hobs have so much hot exhaust gas bypass that the air around the sids and above the pan is much warmer, which does two things, it increases the airflow velocity above the pan diluting any water vapour, and its heating it which prevents the water vapour from condensing into visible vapour so early.

The inefficiencies of high exhaust bypass from gas rings, and to slightly lesser extent of halogen and electric rings when using under sized pans, might well change the overall cost effectiveness of all the energy sources by quite a lot.

Yes but in cooler weather your gas heating backs off because of the excess heat from the gas hob. Similarly since fitting LED bulbs around the house our electric costs have fallen whilst our gas bill has risen. 🙈

 

[Sam Vimes]

Pan sizes on gas burners do have to be correctly sized but flames up the side will still heat the pan sides. Too large a burner where the flames are just lost up the side without making contact with the pan would be inefficient.

Even so with gas 1/3 or 1/4 the cost of electricity the efficiency difference would still make gas hobs cheaper to run.

Pan sizing on induction hobs is equally important. Too large a pan on a small induction burner will not be as efficient as one the same size. Ditto a smaller pan on a large burner.

 

[Hutch]

I miss a gas ring on our home cooker as when using a WOK the heat doesn't get up the side of the Wok. But the Cadac we have works well for the Wok

 

[ProfJohnL]

...
Pan sizing on induction hobs is equally important. Too large a pan on a small induction burner will not be as efficient as one the same size. Ditto a smaller pan on a large burner.

I'm not certain that true, becasue the energy is transferred to the base of the pan, and it can only transfer the energy produced by the emitter. If the pan is over sized, it will still only receive the emitters rated output but spread over a larger area so the watts pr sq unit will be down but total amount of energy transferred will be the same. The problem may be the total heat loss from a larger pan may be greater which might slow down the rate of temperature rise, and possibly reduce the maximum temperature that can be achieved, but the same would apply to a small gas burner under a large pan.

 

[Sam Vimes]

Its getting technical.....

An oversized pan, as you say will receive the majority of the induction current and heat up through the base. As you go onto say the problem arises that the larger the pan has a greater surface area and is therefore liable to act as a radiator of heat making the process take longer. The same applies to what ever type of hob being used. So if you measure efficiency in terms of how long it takes to heat a fixed amount of water, for example, the figure will vary depending on pan size for the same volume of water. Since we pay for energy which is time based then this could be important - although I suspect the differences are minimal as to not be noticeable.

A smaller pan will obviously not be able to make use of all the available energy from the induction hob. So that is wasteful - again the degree to which this is true is probably not significant to most people.

Of equal importance is the right type of pan. Materials vary. Many pans these days are made of aluminium and have an iron spreader in the base. I've found the extent to which this iron spreader works is variable. We have frying pans of equal sizes but different materials and the heat distribution is different between them. For example, and omlette cooked in one is much more evenly cooked than when using the other pan.