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Tuesday, 22 January 2008

Sustainable Cooking

I've been pondering the issue of energy for cooking - the various energy sources and the technology for using them in the kitchen. Got a few comments and a couple of conclusions to share.

First, burning gas. If we're talking about the fossil fuel kind of gas, I'm opposed to it on the basis that it's a non-renewable, polluting source of energy. Pragmatically speaking it may be an essential part of our transition to sustainability but in the long-term the use of "natural" gas in the kitchen has to stop. I should also mention that in absolute energy terms it's rather inefficient: lots of energy used to extract and transport it, then lots of heat wasted into the air without performing any useful work.

Second, burning wood (or other biomass). In some cases wood is probably the best choice, but I suspect that'll be a minority. Wood is renewable, of course. It's also somewhat polluting especially in areas with dense populations. It's inefficient in terms of being able to direct the heat energy into the cooking but in cold climates that becomes a benefit rather than a problem. Not a good choice for my home though.

Next, solar. Do a web search for "solar oven" and you'll find lots of innovation around the basic theme of using the sun's heat to cook food in an insulated vessel. Absolutely top marks for being clean and sustainable. Not so great for cloudy weather, though, and hard to control in terms of temperature and therefore cooking time. I could imagine this technology becoming more common in the future if other energy systems are struggling to deliver the needs of society... but probably not my own family eating sun-cooked roast veges this coming winter.

Finally, heat from electricity - it's a broad topic. You have to look at both how the electricity is produced and how it is used. The production part of the discussion is well-trodden ground... everybody knows coal is dirty and non-renewable while wind/solar/wave etc offer far cleaner and sustainable sources. No, the really interesting bit is in how the electricity is used.

Most of us have heard that using our microwave oven is a more energy-efficient cooking option than using the standard electric oven or hotplate. That makes sense at first glance. It's not as cut and dried as it sounds, though: consider the case of my own microwave oven.

It's rated at 900W cooking power, which means in theory that it can generate lots of heat directly inside the food instead of heating the materials and air surrounding the food. But if it's putting 900W into the food, why is it drawing 1400W from my AC socket? 500W of power - more than third of the total draw - is being wasted by the machine, lost as heat into my kitchen without touching the food. That's not really very impressive. I've no idea whether other microwave ovens on the market perform any better.

What I do know is that induction cooking is often touted as the safer, more efficient alternative to traditional electric hotplates or gas burners. The technology is vaguely similar to microwave cooking, but instead of using radio waves to transmit energy into the food it uses magnetic fields to transmit energy into the metallic cookware. Proponents like to point out the 85-90% efficiency of converting electrical energy into useful heat (ie heat in the cookware, in contact with the food). Sure beats the 65% that my microwave is capable of.

But I reckon there's an even better electrical cooking technology that's being overlooked. It's cheap, and simple, and already well established in the marketplace. It's your regular old electric frypan. An electric pan has an embedded element which converts 100% of the energy it consumes into heat in the cookware. A portion of that energy is lost as heat radiates away from the pan, but the same could be said of induction cooking technology.

With some simple design improvements - mostly focusing on insulation - highly efficient cooking vessels with embedded electrical heating elements could be the eco-friendly kitchen technology of choice in the future, powered of course using electricity from clean, renewable sources.

5 comments:

Crazy Mumma said...

What about crock pots (slow cookers)? Have you looked at them in any depth? They seem to be that little bit more efficient again than a frypan, although of course it depends what you are cooking.

TB said...

Good question.

It seems there are a whole bunch of designs, some of which are apparently less efficient than a good electric oven.

But I found one interesting product which is probably the smartest form of "slow cooker" around. You use a regular stove or burner to bring your ingredients to boiling point in a removable inner pot, then place that pot into a highly insulated, sealed vessel and leave it alone.

The beauty of this approach is that you get the food to a slow-cooker-like temperature with your initial energy expenditure, then it continues to cook without any additional energy input. Just to be clear: this cooker has no power cord.

And though that sounds innovative and high tech... it's just a variant on an old idea.

Iain said...

Natural gas beats electricity hands down, for two reasons:
1. It's more efficient (no brainer here).
2. Carbon dioxide is a "better" greenhouse agent to be releasing - being substantially less capable of holding heat - than methane, the principal agent in natural gas. Even considering the lifetime of each gas in the atmosphere, burning methane is better than venting it. (Should the hydrates in the various deep oceans or the siberian permafrost ever be released, we're in big trouble.)

My big whinge is that we don't commonly trap methane from natural sources, notably sewerage processing systems and garbage tips. This would be yet another way to reduce the impact we're all having; consider it a lesser of two evils.

Having said that, if we assume that coal will continue to be extracted (alas, it will for the time being) then I'm all for extracting the methane first as natural gas and burning it for cooking and heating. Again, while leaving it there would be better, it's not possible to extract the coal without releasing the methane and unfortunately the political will's not there to leave the coal seams alone in the first place.

Iain said...

A footnote: I'm assuming that coal - or, commonly these days, natural gas - is the primary method of electricity production. Converting either to electrical energy involves massive amounts of waste - 70% for coal (up to 50% for modern plants, but Australia doesn't have many of those), and around 40% for a good new gas turbine.

Which is always true in Australia, notwithstanding the small-but-increasing amount of renewable energy being generated here.

Renewable sources of electrical energy make this moot for those enlightened enough to pay the extra (though using the energy source directly will always be more efficient where it's possible :-) ), but unfortunately those who do so are in the minority and by definition must remain so given the low proportion of renewables feeding the Australian grid.

TB said...

Hey Iain,

Glad you added that second comment, I was about to beat you down ;-)

Yes, in present-day Australia, in comparison with coal-sourced electricity, gas wins easily on a number of fronts. But in the long term that comparison becomes meaningless because we have to stop burning both of them for various environmental and resource depletion reasons.

In the mean time there are city-dwelling, future-minded people like myself who want to get ahead of that curve. Since I'm already doing everything I can to support the renewable energy industry in this country (by reducing consumption as much as possible and then buying 100% GreenPower certified electricity) the comparison is a bit different. Should I be using gas, biomass or renewable electricity?

Seems to me that the answer for us, today, is the same as for most people in the future: plug it in instead of lighting it up.

I'm with you 100% on the issue of methane emissions from human activity, too. Waste equals food - or in this case a fuel which ought to be converted into useful energy and a far less harmful atmospheric gas.

Cheers,
Terry