Reinventing the cooker

The role of technology is probably the most talked aspect of sustainability. But some technologies get more attention than others. Green tech blogs tend to be dominated by renewable energy, gadgets and electric cars. There are far fewer sites dedicated to the everyday technologies that we depend on – things like washing machines, toilets, or cookers.

I’ve written about the first two of those three before, but I haven’t looked at cooking in any detail. Inspired by Low Tech magazine, I thought I’d remedy that.

Everyone needs to cook. It is the most basic of energy needs. You can get by without a source of light if you have to, but you have to cook. When talking about universal energy access and reaching the rural poor, the first problem to address is cooking. Many poorer communities depend on wood or dung for cooking, which can be smoky and unhealthy, and bad news for trees. More efficient cookstoves mean cleaner air, lower greenhouse gas emissions, and more standing trees. Everybody wins, and there are many different NGOs working on cookstoves.

But what about us in the West? Interestingly, many of those ‘primitive’ cooking methods may actually be more efficient that some of the technologies we use in our modern homes. Once you factor in the energy generation and transmission, an electric hob is less efficient than an open fire. And yes, that includes ceramic or induction hobs.

cooking technologies efficiency

The reasons for this are obvious when you stop and think about it. You can cook on natural gas, if you have a gas cooker. If you have an electric stove, you need to burn that gas or something similar and turn it into heat. That heat is then turned into electricity, transmitted across the countryside and into your home, ready to be turned back into heat so you can cook on it. Energy is lost at every stage, making the process much less efficient than if you had just cooked directly on the gas. “Any electric cooking device” says Low Tech’s Kris De Decker, “is an insult to the science of thermodynamics.”

Generating the heat is wasteful enough, but we don’t use it well when it comes to the cooking either. Much of the heat is wasted out the sides of the pan or out the top, warming the air rather than the food. This applies to cooking on gas too. There is an absurdity here, just as there is with combustion engines or purifying water to drinking standard and using it to flush toilets. We are going to have to rethink how we cook.

There are better ways, and we used to use them much more frequently when energy was more expensive and less accessible. A haybox or ‘fireless cooker’ would have been a standard household device at one time – I posted some designs for one a while back. An insulated drawer or recess for slow cooking was often built into ranges and stoves until the 1950s or so. Presumably this fell out of use because we wanted the convenience of cooking things a little quicker.

A fireless cooker works by simply retaining heat. You heat the food thoroughly, and then pack it in hay, blankets or more modern forms of insulation, and keep the heat in until the food is cooked. Slow cookers do still have a heating element, but they apply similar principles and are more efficient than stove-top cooking. Again, it’s not quick.

If, like my house, you’re stuck with cooking on electricity, a microwave will save energy for some kinds of cooking, reheating, or getting things started. Research suggests that it’s not universally better though, and is best at smaller portions or cooking without water. There are other tips for speeding things up and saving energy – things like copper bottomed pans, choosing a fan oven, or using metal spikes to accelerate roasting and baking. But really, we’re in need of a bigger solution.

In some parts of the world, it’s possible to cook with the sun. I remember experimenting with the Malagasy sunshine as a child, with mixed results. A well designed solar cooker can be very effective, although it’s usually quite slow. More modern solar stoves, like this one, amplify the sun’s heat to cook much faster, but you are still committed to being outdoors and cooking in daylight.

Where does that leave us? Well, in Britain most of us have access to gas for cooking. A gas cooker, used efficiently, is probably the greenest option at the moment for most. But since gas is a non-renewable resource, and is a source of carbon emissions, it’s not a long term solution. Renewable energy, especially when generated locally, improves the case for cooking on electricity, but it’s still not very efficient.

De Decker concludes that technically, the best way to cook is a combination of rocket stove, pressure cooker and hotbox, which gets close to 90% thermal efficiency – compared to the 13% an electric hob might score.

I suspect that most of us want quicker ways to cook. In which case, there’s a wide open market for new cooking technologies.


3 Comments on “Reinventing the cooker”

  1. OmniRunner January 14, 2015 at 8:45 pm #

    We use a toaster over quite often. It is much smaller than the regular oven and we assume it uses less electricity.
    The inefficiency of electricity makes me wonder how much more efficient electric cars will be? Maybe burning the hydrocarbons is more efficient. I don’t know.
    In the winter we enjoy using the regular over as it helps keep the house warm. I guess that speaks to how inefficient our oven is!

  2. Neil January 14, 2015 at 9:01 pm #

    What a great article, its obvious when you think about it. I have used my wood burner to cook jacket potatoes a few times very nice and effective but uses aluminium (although we can recycle this). Generally cook using gas. I think electric cars are more efficient than petrol anyway although some of the very small diesels maybe better.

  3. henry1941 January 14, 2015 at 9:32 pm #

    Electricity generation in power stations results in the loss of around 60% of the energy due to thermodynamic losses. This is an issue wherever electricity is used.

    Thus the use of electricity for heating is always wasteful. This applies to domestic heating, and even more so to heating of cars, buses and trains.

    Vehicles can be heated by waste heat but trains are usually heated by electricity, less often by waste heat from the cooling system. The former constitutes a considerable proportion of the energy consumption.

    An effective way of reducing thermodynamic losses from electricity generation is by using the waste heat in district heating systems or through combined-heat-and-power (CHP), though this comes at the cost of complexity.

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