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Last Updated: Monday, 3 April 2006, 09:56 GMT 10:56 UK
Save the planet on the back of an envelope
GREEN LIGHT
Bright ideas from Magazine readers

There must be a national effort to bring about a "green revolution", said the government this week. But what simple things can we all do to save the Earth?

Each and every one of us could help save the planet by making just a few changes in our household energy use.

So we're inviting you to tell us how you think we could all be greener and more energy efficient at home, and that includes saving water.

Send us your ideas - whether they are technology innovations, new or improved gadgets or simply tips on energy-saving behaviour - to the Magazine using the form below. If possible include drawings explaining how your gadget or idea might work.

Each day we'll publish one of your ideas, with a brief assessment from an expert as to whether it might work. To get you all started here's one of the Magazine team's own suggestions - and what the experts thought of it.

A thermal kettle?

One of the biggest household energy guzzlers is the very thing few of us could countenance life without: the kettle.

The energy used to boil one kettle of water could light a room for an entire evening. On top of that, most of us heat more water than we need and sometimes boil kettles more than once before actually making that cup of tea.

Most people re-boil kettles when there's no need to
80C is hot enough for most drinks
So why not have a kettle-Thermos combination, thought the Magazine. Surely boiling the kettle once and keeping water hot throughout the day would be a much more efficient use of energy?

Possibly not, says Oliver Knight, Energy Policy Analyst at the Sustainable Development Commission.

"While it looks like a good idea it may lead to people boiling far more water than they need," he said.

"The best thing to do is to boil the right amount of water. It would be more efficient to boil just one cup of water seven times a day than boil too much and keep it hot."

Nicholas Morton, Innovation Unit manager at the Design Council, agrees that it is more effective to simply restrict the amount of water you boil than keep it hot for longer.

"People are erratic in their use of energy so you need to fit in with the way people do things. It is most efficient to avoid boiling water that is going to be wasted."

Environmental writer Donnachadh McCarthy, who featured in last week's It's Not Easy Being Green on BBC Two, is a bit more encouraging. "That's a brilliant idea," he says. "I'm jealous I hadn't thought of that.

Why doesn't someone make an oven that doesn't go cold?
Writer Donnachadh McCarthy
"But come to think of it, why doesn't somebody make an oven that doesn't go cold? Then instead of heating an oven to 400 degrees for two hours, you could heat it to 600 degrees, turn it off and let the food cook as the oven slowly cools down."

Shops should also be made to turn their lights off at night and weekends, he says, and escalators should not operate 24 hours a day, regardless of whether anyone is using them. A survey he did recently found 30% of shops and 60% of escalators going all day every day.

But even better than our insulated kettle, he says, would be for everyone to do exactly as Messrs Knight and Morton suggest - to boil only the amount of water that's needed.

Ah well. Nul points for the Magazine team then. Can you do better? Send us your suggestions by filling in the form below.


Send your idea using the form below. If you can, send us drawings explaining how your idea would work. Send these to the.magazine@bbc.co.uk, please making sure that the subject line is GREEN LIGHT.

Your comments

Re your over techie complicated idea of a Thermos kettle (is "Thermos" not a trade mark, by the way?), why not keep excess boiled water in a vacuum flask and use as required, or make one large vacuum flask of, for instance, coffee and use it throughout the day - pretend every day's a picnic!!
David K, Ilford, UK

How about the cup that heats the water for the tea. I also remember travel kettles that were just a small heating element that you clipped over the side of a cup. If these could be made more efficient and quick the problem could be solved.
John Sweeney, London UK

The idea of boiling just the right amount of water in your kettle is good - but most kettles are marked in Pints or Litres - few of us could be certain exactly how much water we needed for a particular purpose. What is needed is an adjustable scale (with say sliding plastic markers in a ratcheted groove) which you could set up showing how much water was needed for:

  • "My favourite Mug"
  • "The small Tea Pot"
  • "The Cafetiere"
  • "The Large Tea Pot"
No guessing after it was set up! The correct amount every time.
John White, Deal Kent

A little thing about the kettle - would it make a difference if the kettle was filled with warm water as opposed to from the cold tap? That way it wouldn't need to expend the same amount of energy getting the water to boiling point? Or is this just robbing Peter to pay Paul?
Alastair McMillen, Edinburgh, UK

"But come to think of it, why doesn't somebody make an oven that doesn't go cold? Then instead of heating an oven to 400 degrees for two hours, you could heat it to 600 degrees, turn it off and let the food cook as the oven slowly cools down." Get an AGA.
David Cartwright, Coventry UK

An oven that doesn't cool down is called a victory oven. Heat the food, put it in a crafte filled with straw and the straw keeps it warm. Great for slow cook dishes like stews.
sam, hull

Everybody in the far east already has an insulated kettle. With a keep warm facility and a pump so you don't have to pick it up. They've had them for decades.
Dave Howorth, Cambridge

A few obvious ideas from a humble physicist - no idea if they've already been done!

    1) A built in digital thermometer that shows the temperature of the water. If it is above 80C then its fine for making hot drinks. In fact, you could have preset to heat only to 80C. There is a lot of latent heat required to boil the water so it is very much more efficient to heat to a temperature of 90C not boiling point. The evidence of steam coming out of most kettles shows that energy is being wasted. A magnetic stirrer inside the kettle (driven by an AC current below) would help to even out the heat transfer from the element. 2) Fit a balance in the base element of the kettle (most kettles come in two parts these days). This could weight the kettle+water and hence give the volume of water in the kettle very accurately. 3) Use the temperature, and mass of water in the kettle to calculate and display energy consumption on the fly. You could have a read out in kWh's and hence monitor your usage.
David Jenkins

The thermos kettle gadgets are more common than normal kettles here. Every office and most homes have one. You can choose a range of settings from 60C up to 98C depending on what you need. Also another innovation here is the solar powered "catseye" in the street. I know, but they charge up in the daytime....
Alan, Nara, Japan

Er, for all those people who've refered to the insultated kettles in Japan (the famous "denki pot"), aren't they're actually one of the least environmentally friendly options? You still need to heat the water to boiling point in the first place, and then you need the electricity constantly to keep the water near boiling (and some of them periodically reboil the water to keep the temperature up). Not the best option!
Tom Burn, London

Fill your kettle last thing at night. By morning the cold mains water (particulary in winter!) has already risen to room temperature so the kettle needs to uses less energy to make that first cup of the day.
Keith Anderson, Musselburgh, Scotland

The Thermos kettle idea is like the myth that it's more economical to keep your central heating running all day long; heat loss is proportional to temperature differential, time sustained, and thermal conductivity (i.e. insulating ability) of the body. The only use for such 'insulated samovars' is where dozens of workers share a kitchen. Instead, I suggest John White and David Jenkins patent their ideas (especially the markers and lower-temp cutout). It never ceases to amaze me that people boil a full 1.5-L kettle for a 300-mL mug of tea!
Peter Barber, Melbourne, Australia

A simple but effective way of reducing energy consumption when boiling the kettle is to ensure that the kettle is filled with water after you have used it, rather than filling the kettle immeadiately prior to using it. This has the advantage of partially heating the fresh water in the kettle without further expending energy, also the water in the kettle will now be at room temperature or above when you next come to boil the kettle. As all the others have said only boil as much water as is needed - so any excess water can be removed from the kettle before it is boiled.
Bik Choudhary, Oxford, UK

Has everyone forgotten what our grandparents used to use for this type of situation? Tea Cosies! We just need to learn the fine art of crocheting.
Matt Bradley, Bromsgrove/UK

I knew a guy whose flatmate put excess boiled water from the kettle into a thermos each morning and then reheated that water each evening. This was many years ago and he was universally derided as being tightfisted with his cash. He did use a lot less gas than most other people however. Mind you, he also boiled eggs in the kettle while making his tea.
John Kelly, Florencecourt, Co. Fermanagh

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