Cheap beads offer alternative solar-heating storage
A cheap material that can store heat energy collected from the sun during the day that can be released slowly over night has been developed by researchers in the India. The material based on paraffin wax and stearic acid is described in a forthcoming issue of the International Journal of Renewable Energy Technology and could help keep homes warm in sunny parts of the world that get very cold at night without burning wood or fossil fuels.
Mechanical engineer Meenakshi Reddy of Sri Venkateswara College of Engineering and Technology, in Chittoor, Andra Pradesh, and colleagues explain how certain materials, known as phase change materials (PCM) can store a large amount of heat in the form of latent heat in a small volume. PCMs have a high heat of fusion and melt/freeze at a certain temperature. Heat is absorbed when the material melts and released when it freezes. Heated in the sun, the mixture of paraffin wax (which melts at about 37 Celsius) and stearic acid (a fat commonly used to make soap) becomes entirely liquid. However, as it solidifies it slowly releases the stored heat. The process is akin to the phase changing heating that occurs in hand-warmers that contain a PCM but in this case the material does not need to be boiled in a pan or heated in a microwave oven to absorb latent heat.
The team has now tested spherical capsules just 38 millimetres in diameter containing a blend of paraffin and stearic acid, which can be floated on the top of water in a tank. Stearic acid is a lot cheaper on the Indian market than paraffin and more readily available. The team found that costs could be held down without reducing the overall heating efficiency of the capsules by lowering the proportion of paraffin wax.
More information: Int. J. Renewable Energy Technology, 2012, 3, 11-23
Provided by
Inderscience Publishers
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Dec 02, 2011
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Dec 02, 2011
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Dec 02, 2011
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They should design a system that works with a hot water pipe floor heating system as well.
Dec 02, 2011
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A 1 cubic meter block of paraffin will hold about 160,000,000 Joules of energy as latent heat. In comparison one cubic meter o f natural gas contains about 40,000,000 joules of energy.
So in my case, one cubic meter of paraffin would store enough energy as latent heat to provide just enough heat to heat my house for a full average winter day.
3 kilos of parafin seems to cost about 30 bucks. So a meter cubed block will cost approximately $24,000
Dec 02, 2011
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I see $2USD per pound at www.amazon.com/Wa...sbs_ac_1
and at http://www.candle...-wax.php
That is of course a retail price for a craft item.
Does this reduce your meter cubed block cost by roughly a factor of 10 or am I missing something?
Colin Keizer
Dec 02, 2011
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With 34 cases per pallet and roughly $100USD per case, that would be about $3400USD plus shipping per pallet. OK, that's not exactly a cubic meter, but close, so not really a factor of 10 improvement, but something like one quarter.
I hope an industrial source for less than pristine pure parafin would give a cost lower than $2USD per pound, but I have not found that, yet.
Of course, I don't need a pallet load to experiment at home.
Must remember that liquid parafin is about as spark friendly as vaporized gasoline . . . .
Colin Keizer
Dec 02, 2011
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Dec 02, 2011
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Dec 02, 2011
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The stearic acid won't be cheap, either.
Colin Keizer
Dec 02, 2011
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Or this old Popular Science article:http://books.goog...eutectic salts solar&source=bl&ots=jjFmBESsFR&sig=Kv_L7oHmBzPW09NLfd0UKx1DOlw&hl=en&ei=U2nZTtvgD8iJ2AWht5C5Dg&sa=X&oi=book_result&ct=result&resnum=8&sqi=2&ved=0CGsQ6AEwBw#v=onepage&q=eutectic%20salts%20solar&f=false
Wonder why it hasn't been resurrected?
Dec 02, 2011
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Also, He forgot that the amount of water in the system will still be be primary heat carrier.
For example, heating 250 gallons of water 40 degrees celsius will also provide 160 million joules of energy.
Dec 02, 2011
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As for the cost, ya, I did check an on line source, but it was for small quantities. Bulk is 1/10th the cost apparently and that is great because it reduces the price for a cubic meter of wax down to $3,000.
So realistically a system with a wax heat reservoir about half a cubic meter can store enough heat for my house at a cost of $1,500 for parafin.
I might actually do this.
Dec 03, 2011
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Dec 03, 2011
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If the freezing point is properly tuned, the wax will freeze and radiate it's heat of fusion at say 70'C, tending to keep the room at that temp.
Dec 03, 2011
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As someone pointed out eutectic salt solutions are more stable, not flammable, cheaper in the long term (never have to be replaced, are biocidal in general, and probably lend themselves to cooling tasks in the summer more so than oil based products.
Dec 06, 2011
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