Thursday, March 8, 2012

Hobs and Choice, something to get steamed up about?

We have been researching new kitchen appliances in preparation for replacing our kitchen.  Technology has really moved on since last time we designed a kitchen 20-ish years ago.   We did not really know the extent of this until we started looking.

The first innovation we had heard about is induction hobs.  The technology is actually quite straight forward and quite old being based on a medium frequency transformer where the base of the pan acts as a shorted turn.  The thermal inertia is very low which means it heats up quickly but the best part is that when the pan is removed, so is the load so the hob only draws power when actively in use which means its also very safe.  It does require special thick bottomed cast iron pans but our cookware is ready to be replaced in any case.

Our current hob is gas fired so I was interested in the relative carbon footprint compared with Induction cooking? From an efficiency point of view Induction hobs are claimed to be 84% efficient compared with around 40% for gas (Source Wikipedia).   The salesman also quoted the benefit of not requiring ventilation for induction hobs though I would think the excess heat from the gas would more than compensate for this.  Natural gas produces 0.29Kg of CO2 per kWh versus grid based electricity of 0.52Kg per kWh (UK average).  The maths points to induction hobs being the winner at 85% of the CO2 of the gas hob.  Cost wise its slightly behind as electricity is over twice the price of gas but overall its a thumbs up for induction hobs.

Last weekend we went to Batibouw 2012; the annual “ideal home” show of Belgium where everyone seemed to be showing off steam ovens.  Again steam cooking is not new;  I remember my mother using a pressure cooker when I was young.   It was a bit of a faff  though.  It seems steam is now back in vogue and we saw built in combi-steam ovens from Neff, AEG, Bosch and Siemens and others.  Again, interested in the potential carbon savings, once home I searched for information comparing steam oven efficiency versus conventional cooking.  After an hour all I could find was a mention of “around 50%” energy savings.  This seems reasonable as it’s a closed system not dissimilar to a kettle.   Indeed I’ve always been humbled by the simple lossless efficiency of an element directly heating water :o).   Steam ovens seem to require about 1.5Kw which supports the assertion of a 50% saving.

Both induction hobs and steam ovens seem to have excellent eco-credentials but you certainly pay for the privilege.  Typical prices were over €1000 for the hobs and up to €3000 for a combi-steam oven which is nearly 20x the price of the cheapest conventional oven. Hmm. … food for thought!

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