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OKIsItJustMe

(19,933 posts)
Tue Jan 10, 2017, 08:18 PM Jan 2017

Summer heat for the winter

https://www.empa.ch/web/s604/naoh-heat-storage
[font face=Serif][font size=5]Summer heat for the winter[/font]

Jan 10, 2017 | RAINER KLOSE

[font size=4]Can thermal solar energy be stored until wintertime? Within a European research consortium Empa scientists and their colleagues have spent four years studying this question by pitting three different techniques against each other.[/font]

[font size=3]We are still a far cry from a sustainable energy supply: in 2014, 71 percent of all privately-owned apartments and houses in Switzerland were heated with fossil fuels, and 60 percent of the hot water consumed in private households is generated in this way. In other words, a considerable amount of fossil energy could be saved if we were able to store heat from sunny summer days until wintertime and retrieve it at the flick of a switch. Is there a way to do this? It certainly looks like it. Since autumn of 2016, following several years of research, Empa has a plant on a lab scale in operation that works reliably and is able to store heat in the long term. But the road to get there was long and winding.

The theory behind this kind of heat storage is fairly straightforward: if you pour water into a beaker containing solid or concentrated sodium hydroxide (NaOH), the mixture heats up. The dilution is exothermic: chemical energy is released in the form of heat. Moreover, sodium hydroxide solution is highly hygroscopic and able to absorb water vapor. The condensation heat obtained as a result warms up the sodium hydroxide solution even more.



The other way round is also possible: if we feed energy into a dilute sodium hydroxide solution in the form of heat, the water evaporates; the sodium hydroxide solution will get more concentrated and thus stores the supplied energy. This solution can be kept for months and even years, or transported in tanks. If it comes into contact with water (vapor) again, the stored heat is re-released.



“This method enables solar energy to be stored in the form of chemical energy from the summer until the wintertime,” says Fumey. “And that’s not all: the stored heat can also be transported elsewhere in the form of concentrated sodium hydroxide solution, which makes it flexible to use.” The search for industrial partners to help build a compact household system on the basis of the Empa lab model has now begun. The next prototype of the sodium hydroxide storage system could then be used in NEST, for example.[/font][/font]
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