Navitron Renewable Energy and Sustainability Forum

SOLAR THERMAL => Solar Cooking (using vacuum tubes or more conventional methods) => Topic started by: Ivan on August 07, 2007, 09:37:16 PM



Title: Save Electricity with Solar Kettles
Post by: Ivan on August 07, 2007, 09:37:16 PM
Most people tend to drink several cups of tea a day. For several months of the year, all (or most) of this water could be produced by Navitron solar kettles. You can also pour the heated water into saucepans used for cooking in the evening, reducing the energy required to get the water from ambient temperature up to cooking temperature.

I don't drink any tea/coffee, but even so, we generally use 1.5litres to 3litres of solar-heated hot water each day.
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Example:

Let's say there are 3 people in the house, all of whom drink 6cups of tea each day. (say 6x 0.3litres=2litres). Let's also suggest that evening meal requires 2litres of hot water for cooking pasta/vegetables etc. Let's also say that the cook does not want to mess about with pioneering cooking techniques!

So the household can utilise 4litres of solar-heated water each day (3 tubes would heat 4.5litres....actually, if the weather is good, you can heat water up to 3times in each tube =13.5litres/day)

The energy required to heat 4litres of water from 15C to 100C is calculated thus:

Temp rise (C) x Volume of water (litres) x 4200 (heat capacity in JKg-1K-1)= 85 x 4 x 4200 = 1.428MJ =0.4kWh

Assuming the water would be heated electrically (it usually is if it a kettle, and if it is heated on a gas hob, it is so much less efficient that it might as well be heated electrically), then this is equivalent to 0.2kg CO2 (assuming the powerstation runs on gas - if it runs on coal, it would be twice as much)

Over half a year, this is equivalent to 73kWh or 37kg of CO2. Or put it another way, 8 worth of electricity.

If all of our 10million households did this, we'd save 730GWh of energy (365 000 tonnes of CO2) and 80million



Title: Re: Save Electricity with Solar Kettles
Post by: NickW on August 08, 2007, 12:53:33 PM
Ivan - I think your Maths is going a bit off course. I trust you employ an accountant to do your books at Navitron ;)

If 10 million households in one year save 146 kwh of electricity each then this equates to about 628,000 tonnes of Co2

The typical fuel mix for UK electricity gives a CO2 output of 0.43kg per kwh.

Anyway it would be interesting to see if navitron can come up with a practical solar kettle that can sit on my south facing kitchen window.

Regards

Nick


Title: Re: Save Electricity with Solar Kettles
Post by: Amaterasu on August 08, 2007, 03:12:31 PM
as we have proved the solar kettle can work.

Would it be possible to make one that is ............... kettle shaped or at least jug shaped.

Yes I know there are all sorts and shapes of jugs but I'll leave that discussion to martin and his BGG photos.

A truly kettle shaped solar kettle would sell by the bucket load


Title: Re: Save Electricity with Solar Kettles
Post by: Joules on August 08, 2007, 06:54:20 PM
Or even a Solar MUG   :)


                 Joules


Title: Re: Save Electricity with Solar Kettles
Post by: Ivan on August 08, 2007, 08:08:54 PM
Thanks Nick - I've revised the CO2 calculation - should be correct now. There were too many zeros on the end. Luckily, Navitron profits don't have so many zeros on the end


Ivan


Title: Re: Save Electricity with Solar Kettles
Post by: Jonzjob on August 11, 2007, 04:59:03 PM
Not quite solar cooking, but I have a tube, water filled, leaning against a wall in the garden. It was put there yesterday to show some French friends how they work and how efecient they are. It took about 2 1/2 hours to heat the water to boiling in the 58mm tube. I had a copper insert tube stoob beside it and as it was windy it was quite cool. I picked it up and started to show our friends how it fitted in the tube. I got it about 12 inches into the tube and had to get it out quickly or let it go. It took about 5 seconds to get as hot as the water AT THE BULB which was still better part of 3 feet from the water! I was shocked at how quickly it got hot... The temp in the shade was about 29 dec C and the sun index was 7 going on 8, so nice and warm...

I have been thinking of how it could be used in that way, but my brain cell has gone on strike. The heat probably woke it up? :o


Title: Re: Save Electricity with Solar Kettles
Post by: Ivan on August 11, 2007, 07:03:50 PM
It is quite amazing how fast heatpipes transfer heat - much much quicker than simple heat conduction alone


Title: Re: Save Electricity with Solar Kettles
Post by: CeeBee on September 14, 2007, 12:59:14 PM
Would it be possible to make one that is ............... kettle shaped or at least jug shaped.
...
A truly kettle shaped solar kettle would sell by the bucket load

Has anyone tried mounting a kettle-like thing, with a suitable recess in the base, on the end of one of the heat-pipes? I haven't yet had hands-on an actual solar tube (perhaps I'll get some installed soon), but I imagine they're not the most convenient things to use as kettles, and prone to being broken. I guess one would have to insulate the 'kettle' for this to work, since unlike just having the water inside the tube itself, it would cool down at the rate which kettles normally do.

Unless I'm missing them, I don't see single tubes (with/without heat pipe) on the price list.


Title: Re: Save Electricity with Solar Kettles
Post by: rhys on September 14, 2007, 03:10:19 PM
In the mean time we could all use eco kettles, only boil what you need. - I've got one and it works - a simple idea all kettles should be like this.
http://www.ethicalsuperstore.com/products/product-creation/eco-kettle/?gclid=CJ2Yx82Pw44CFQXnlAodmgaoCA


Title: Re: Save Electricity with Solar Kettles
Post by: Ivan on September 14, 2007, 04:55:18 PM
How about this one, from Navitron? Boils EXACTLY what you need, on-demand and in 3 seconds

http://c-zero.co.uk/page.php?73


Title: Re: Save Electricity with Solar Kettles
Post by: paul on September 14, 2007, 05:01:09 PM
How does it fare for de-scaling if used in hard water areas?

Paul


Title: Re: Save Electricity with Solar Kettles
Post by: Ivan on September 14, 2007, 05:15:43 PM
Difficult to know. I don't think it has been on the market long enough to find out. I imagine that it might be clean-able, but can't say for sure.


Title: Re: Save Electricity with Solar Kettles
Post by: room101 on September 16, 2007, 09:47:47 AM
Do you know the output temp..... ???


Title: Re: Save Electricity with Solar Kettles
Post by: rhys on September 17, 2007, 08:23:09 AM
Sorry Ivan - didn't know you had a product!! Must keep checking the new website. I can't see that these types of kettles should be any different from an ordinary kettle in terms of descaling. Use descaling solution or good old citric acid once in a while.


Title: Re: Save Electricity with Solar Kettles
Post by: Ivan on September 18, 2007, 12:46:03 AM
Output temperature is .......boiling!


Title: Re: Save Electricity with Solar Kettles
Post by: room101 on September 18, 2007, 06:58:14 AM
Thanks Ivan....


Title: Re: Save Electricity with Solar Kettles
Post by: Jonzjob on September 28, 2007, 05:40:27 PM
I have just had a look at the Tefal (or T-Fal in the USA and Japan?) and it has a filter to stop clamming up in hard water areas. Quite interesting, but as we have just bought a kettle designed by Porche how quick do we want to go!!

Very interesting!!


Title: Re: Save Electricity with Solar Kettles
Post by: Capcave on October 02, 2007, 05:44:16 AM
I bought the Tefal a little while ago. The output tempertature is not as hot as a kettle (about 95 degrees as opposed to 100) but the power savings are good (down to 0.4Kwh from 2Kwh per day for boiling water in this house). It's a bit noisy though and as I get my cup of coffee about an hour before she gets up I get a flea in the ear. Have to finish the sound insulation one day soon.


Title: Re: Save Electricity with Solar Kettles
Post by: GlobalWarning on October 19, 2007, 11:35:47 AM
Tefal says it reaches 90 degrees, which sounds fine for all uses except tea (if you're fussy)... think I might get one of these as I can think of lots of uses, eg for a small amount of washing-up or pre-heating water to go into a saucepan (we tend to use what's left in the kettle, but people often put the kettle on specially).  I hate to run hot water through long cold pipes just to get a small amount... I quite often microwave it instead.  One thing I invented which I quite like: if you need a hot cloth for wiping work surfaces, damp it with cold water and microwave it for a few seconds.  Might be a thread-jack, but gotta be energy-efficient!

Jenny



Title: Re: Save Electricity with Solar Kettles
Post by: SteveH on October 19, 2007, 12:01:04 PM
 Just to continue the thread-hijack (sorry... :-[)... I've always wondered how much more efficent the microwave is at heating water... :-\

 If it is much more efficent... Then maybe a special Kettle for it would be the better option... It would, with new materials avalible, be possible to make a Thermos style container with a none metalic reflective component to make a supper eficent boiling device for the domesti MASER (Had to get that in... :laugh:) All you would need is a wistle, pop-up indicator or both to let you know it was boiling... might need some thought to avoid super heating problems mind... maybe a couple of small spheres that stay inside permanantly & bob about in the water...

 Sorry for the continued high-jack.... ::)

 


Title: Re: Save Electricity with Solar Kettles
Post by: GlobalWarning on October 19, 2007, 12:08:00 PM
That's an idea that's been ticking over in my brain, too, for a few years...

OnT: Several Tefal One-Cup users here http://www.hippyshopper.com/2007/08/video_review_te.html (http://www.hippyshopper.com/2007/08/video_review_te.html) seem to be able to tell 90 degrees from 100 degrees as far as their tea-bags are concerned!  Posts about returning said appliance to vendors.... and it's noisy in use apparently.  Still tempted, though.

Thread-jacking again:  I also do the vacuum flask trick which someone else there has described.  Put the remainder of your kettle-hot water into a vacuum-pump (coffee-thing) flask and it'll do for most things.  I have two flasks; you can make tea for everyone for a complete day and (as long as you remove the tea itself, to stop it brewing) it stays good until it runs out.  To save volume you can even make it double-concentrated if you want, and then heat it in the microwave with water added. 

Oh, the lengths we go to in our quest for green....  :angel: ;)



Title: Re: Save Electricity with Solar Kettles
Post by: Capcave on October 19, 2007, 03:55:30 PM
My One cup was condemmed by her nibs within 5 minutes because the water was not hot enough to make tea (her father ran some tea plantations) and uses the kettle. It seems 90 degreees does not dissolve the oils in the tea which need to be at boiling point. Filling it up from the hot top does get the temperature up a little bit. However it seems fine for coffee and saves a load of power. It is quite noisy.


Title: Re: Save Electricity with Solar Kettles
Post by: Ivan on October 20, 2007, 03:23:54 PM
We did some fairly extensive tests, with the Navitron Zero-emission kettle over the summer and found that most people couldn't tell the difference if (teabag) tea was made with water at 80C or higher


Ivan


Title: Re: Save Electricity with Solar Kettles
Post by: Billy on March 20, 2009, 11:52:43 AM
Wasn't it more to do with the tea leaves floating if the water wasn't boiling, in the olden days of course.  During my apprenticeship they always new when I had failed to boil the water just right.  Once brewed the pint of milk went into the kettle (large) and the tea dispensed.  It's where I developed my arm muscles.

 ;D


Title: Re: Save Electricity with Solar Kettles
Post by: MR GUS on March 20, 2009, 12:54:59 PM
there is apparantly a breville version that DOES boil the water! ..however is still noisy.
29.95 @ makro so vat has to be added.

called breville Hotcup



Title: Re: Save Electricity with Solar Kettles
Post by: sunshinekid on March 20, 2009, 06:26:11 PM
as we have the woodburner running much of the time, I bought one of these:

http://www.originalcookware.co.uk/le-crueset-16l-kone-kettle-assorted-colours-2075-p.asp

Got it for 20 quid or so as it was an ex-demo.

It's always full and I keep it on an old fire grate on top of the stove.  That way it's always pretty hot and moving it off the grate onto the top of the stove and it's boiling in a minute or so.

Now I only use the leccy kettle in the morning as I can't wait the hour or so to get up to initial temp!

If the fire's not quite hot enough to heat the water in the kettle, I bung it on the gas stove to finish it off.



Title: Re: Save Electricity with Solar Kettles
Post by: MR GUS on March 20, 2009, 08:22:18 PM
you often get the Kone kettle from tk maxx for around 14 if you ever ding it too badly!
 do you ever stick a coffee perc or similar on the burner?


Title: Re: Save Electricity with Solar Kettles
Post by: alfie on March 20, 2009, 10:16:41 PM
Ivan,
  The link doesnt work  ???


Title: Re: Save Electricity with Solar Kettles
Post by: sjaglin on April 05, 2009, 07:34:02 PM
Hi,

As an alternative, I use my recently acquired kelly kettle ( Kelly  (http://www.kellykettle.com/)) and it's great if you don't mind spending 10 minutes to boil your water.

The wood I use is all from my last  2 years of pruning my garden, I kept and dried all that wood, I knew it would come handy some days. I boil 1.5 L in the morning, make my half liter of strong black stuff and keep the rest in a thermos.

It works really well and is really fun!

I also tried to boil water in my solar oven (http://sjaglin.homelinux.org/Joomla/index.php/component/content/article/37-energy/81-solar-oven), but it's only April and the best I did was 90 degrees, too hot to carry the pan but not quite enough to boil. bike:

Stef

 linux:


Title: Re: Save Electricity with Solar Kettles
Post by: Ivan on April 05, 2009, 10:44:52 PM
Solar Ovens are good - and can reach very high temperatures with direct sunshine. However, the Navitron Solar Kettle idea doesn't need to be lined up with the sun (one of the problems of solar ovens). I haven't checked the temperatures, but we've been using the water from the solar kettle most days recently for making tea and for pre-heating the water for cooking dinner. If we planned ahead, we could cook many of the things in the solar kettle, but as it is, it saves about 5minutes of heating the water on the hob each night.

P.S I couldn't access your solar oven page - error read 'document contains no data'


Title: Re: Save Electricity with Solar Kettles
Post by: wookey on April 06, 2009, 12:43:04 AM
I got my tea/coffee tube out this weekend for first time (prompted by an interested visitor) and it's producing tea already.


Title: Re: Save Electricity with Solar Kettles
Post by: Greenbeast on June 12, 2009, 11:56:58 AM
If i was to use a tube from my existing install, I wonder whether it would be worth leaving the heatpipe in the manifold?
Obviously it would need supporting at the bottom but it might still provide some usable heat while you also use the tube at ground level for water.


Title: Re: Save Electricity with Solar Kettles
Post by: crispy on June 12, 2009, 12:29:39 PM
We've just got a nice simple Philips kettle with clear water gauge (that is more or less accurate) and this has helped us to reduce our electricity consumption for boiling to a minimum...

But it would be great if we could go solar for Tea - the problem is that the better half needs something that is as easy as filling the electric kettle. Has anyone managed to put together a no-hassle and kid safe solar water boiler?



Title: Re: Save Electricity with Solar Kettles
Post by: Ivan on June 16, 2009, 12:20:36 AM
Unfortunately, it takes a bit of practice - both filing and decanting, but it's really quite easy when you get the hang of it. Our solar tube gets used most days - for making tea and for using pre-heated water in pans to cook dinner.

It's never going to be as easy as a kettle due to its shape and size. At one point I wondered about making a pouring spout, but for safety reasons, decided that this was a bad idea.