Posted: Thu Apr 20, 06 9:12 am Post subject: Re: Why aren't tea urns insulated?
Bernie66 wrote:
Too much time on your hands or a very curious mind young sir!
Nah, just thought of the waste incurred by letting all the heat escape.
dougal
Joined: 15 Jan 2005 Posts: 7184 Location: South Kent
Posted: Thu Apr 20, 06 10:07 am Post subject:
Well, as with compost heaps, the bigger the scale of the thing, the less (heat losing) surface there is in comparison to the volume (and hence the amount of stored heat).
Tea urns really shouldn't be keeping stuff hot for any great length of time... by tradition tea should be made with freshly drawn (hopefully well-oxygenated) water, and once made shouldn't be 'kept hot' before serving as it 'stews'.
Then there's the question of whether any insulation might make cleaning the thing more difficult, bringing hygene risks.
And then there's cost. Making a 'metal thermos flask' (metal to avoid hygene problems & to be robust) of that sort of size is going to be considerably more expensive. And, from the first point, there's maybe not much saving to be made...
In order to use the renewable energy generated through our PV system in a variety of ways we are currenly experimenting with a homemade lagged tea urn.
It has a 1600 watt element and during a sunny day we produce this amount of electricity easily. 4099 watts has been the highest so far.
The urn is lagged with an old hot water cylinder jacket and a fire blanket. The outside of the tea urn can get very hot.
The 10 litres of water boils in about 15 - 20 minutes and then goes into a tick over mode where by it uses 160 watts. We have this set up on a timer which switches on and off every 15 mins. When the tea urn is lagged the water does not have to reboil again using 1600 watts; the tick over of 160 watts is fine to maintain the temperature. When it is not lagged the tea urn a great deal of heat and has to reboil.
OK, this is not the most efficient way to create hot water using a solar system but we create 'boiling' water and its near boiling until we decide to use it for tea, washing up, cooking vegetables, rice etc that evening
If we don't use it all that night it is still easily hot enough for a wash in the morning.
Presently we are being paid 5p per kwh for the elecricity we generate so we are getting paid to make boiling water.... not bad!
Have a commerically available tea urn that's lagged would make some sense to us.
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