
New technique stores summer heat until it's needed in winter - devinp
http://newatlas.com/renewable-energy-heat-storage-empa/47334/
======
willholloway
There is no need to store summer heat for the entire winter, which would
necessitate a far larger capacity system.

One would only need to store solar thermal energy that is available on any
sunny or partly sunny day for night time and cloudy days.

Where I live about half of all days produce abundant solar thermal energy even
in the depth of winter. Calculating in night time, you end up with about 12.5%
of total winter time having abundant free thermal energy.

So one would need to build a system of solar thermal collectors about 8 times
the size one would need to heat a house on a sunny winter day, and that is not
a very big system.

Space wise I think it would work for single family residential homes on .25
acre lots if the house was designed for it from the start.

~~~
mikeklaas
Why not just store that solar energy as electricity, and use the electricity
to power heat pumps when needed?

~~~
willholloway
That is a good question and the answer comes down to physics and the economics
of battery technology vs this technology.

~~~
mistermann
It might be that one or the other is better "in general", but I can see that
this technology could have benefits in certain scenarios, maybe long term
storage in remote, cold climates.

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peter303
The opposite of saving winter ice for the summer was popular in the 1800s
before mechanical refrigeration. Ice can last many months if insulated by
sawdust below ground.

~~~
EvanAnderson
Princeton had an "ice pond"[1][2] in the early 80's. The project was run by
Dr. Ted Taylor[3] (who worked on the Manhattan project and later the Orion
spacecraft-- huge nuclear bomb-powered spaceships!). Snow machines made slushy
ice that was stored in pond covered with insulation. Water was pumped through
the pond in the summer to provide cooling. It worked well and at the end of
the summer there was still ice in the pond.

I read about this as a kid reading Freeman Dyson's "Imagined Worlds"[4].
Dyson's commentary is definitely worth reading. (Anything written by Freeman
Dyson is worth reading.)

A cheese factory used ice ponds[5] for about 10 years, eventually abandoning
them because the ice didn't last through the summer and it was difficult to
maintain[6].

[1]:
[https://en.wikipedia.org/wiki/Ice_pond](https://en.wikipedia.org/wiki/Ice_pond)

[2]:
[https://www.washingtonpost.com/archive/opinions/1981/08/02/t...](https://www.washingtonpost.com/archive/opinions/1981/08/02/the-
ice-pond-age-cometh/51396081-09a8-4afe-b69c-1217b4700408/)

[3]:
[https://en.wikipedia.org/wiki/Ted_Taylor_(physicist)](https://en.wikipedia.org/wiki/Ted_Taylor_\(physicist\))

[4]:
[https://books.google.com/books?id=MOC8UJPuvO8C&pg=PA42](https://books.google.com/books?id=MOC8UJPuvO8C&pg=PA42)

[5]: [http://www.nytimes.com/1984/06/03/nyregion/dairy-
hoards-500-...](http://www.nytimes.com/1984/06/03/nyregion/dairy-
hoards-500-tons-of-ice-for-the-summer.html)

[6]:
[https://www.farmshow.com/a_article.php?aid=15129](https://www.farmshow.com/a_article.php?aid=15129)

~~~
londons_explore
What's the thermal conductivity of soil?

Wouldn't you have to insulate your pond from below as well as above?

------
WalterBright
Another way is to simply use the ground. Dig trenches, lay in pipe. The ground
is cooler than the air in summer, can warmer in winter. I read that using it
as a heat exchanger can cut HVAC bills by 30%.

~~~
curtis
These systems are pretty popular, even my dad has one. The problem is they're
also pretty expensive -- on the order of $20,000. At that price it could take
a long time to hit break even, at least in the U.S.

~~~
WalterBright
The main expense is digging the trenches. If this is done before the house is
constructed, i.e. you've already got the backhoe on site to prep the site, the
cost should be minimal.

~~~
petre
You can also bore wells.

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d_burfoot
I think this kind of technology has enormous potential to improve human life.
Bad weather is a huge, chronic problem that makes almost everyones' life
substantially worse. Just the other day my aunt broke her wrist after slipping
on a patch of ice.

One question though: why do they need a special high-tech material to do this?
Why can't they just bubble warm air through cold water in the summer and vice-
versa in the winter? Water has very large heat capacity, 400x that of air by
volume.

~~~
glibgil
It's not high-tech. It is low-tech. NaOH is lye. Anything in the 50% NaOH
solution that is not water is there to make it viscous, but not get it wet

~~~
lisivka
High-tech, by definition, is tech which can make high profit, i.e. c1 sand
into $500 processor. Sand is not low-tech or high-tech by itself.

PS.

Quote from Wikipedia for downvoters:

High tech is often viewed as high risk, but offering the opportunity for high
profits.

[https://en.wikipedia.org/wiki/High_tech](https://en.wikipedia.org/wiki/High_tech)

~~~
astrodust
Definition: "Technology that is at the cutting edge".

Fact: Chemically produced lye dates back to at least 1791 with the Leblanc
process:
[https://en.wikipedia.org/wiki/Leblanc_process](https://en.wikipedia.org/wiki/Leblanc_process)

~~~
lisivka
Fact: green energy/renewable energy/energy saving technologies are cutting
edge now.

Fact: your processor is made from sand which was discovered by first human
ever.

~~~
astrodust
Yes, it's a little known fact that Babylonians were casting huge perfectly
pure silicon crystals. They were also pioneers in x-ray lithography!

Processors are made from sand in the same way people are made from carbon.
You're skipping a few important steps.

~~~
lisivka
Skipped steps are called "high-tech".

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seiferteric
This sounds pretty cool, but are there any numbers on energy density?

~~~
petre
Wikipedia says 44.51 kJ/mol, so that should be 309 Wh/kg, for _dry_ NaOH
dissolved in water. The amount of energy needed to heat 1 kg of water with 1 K
is 1.16 Wh. So the heat released from dissolving 1 kg of NaOH in water will
heat 10 liters of water with about 26.64 K.

[https://en.wikipedia.org/wiki/Enthalpy_change_of_solution](https://en.wikipedia.org/wiki/Enthalpy_change_of_solution)

With the heat released from 20 kg of NaOH dissolved in water you could heat
100 liters of water with 53,3 K, enough to take a hot bath.

~~~
chmod775
It is also more than twice as dense as water, so the amount needed to heat 100
liters of water with 53,3 K will only have 1/10th the volume of said water. So
even if you only use a small area in your basement for energy storage, it
should be enough to have hot baths all winter...

~~~
dpark
20kg of lye for a bath seems like a lot. That's 2000 kg just to get through
the coldest 3 months. Multiply that by the number of people in the house. And
then remember to add space for all the water you'll have to mix with the lye
to extract the heat. And actually double the water space if you're going to
keep it after recharging instead of dumping it.

That sounds like a huge amount of space.

~~~
chmod775
2000kg of NaOH has a volume of less than one cubic meter. And I don't get for
what reason I would have to store the water needed for the reaction instead of
just connecting the device to whatever water supply the house uses.

~~~
dpark
A cubic meter per resident. For just 3 months of the years. And each unit is
diluted 50% already.

As for the water, you're going to basically dump a bunch of water into this
thing to generate heat. And when you're done, your NaOH will be more dilute
and need a bigger storage vessel. So you need enough room to store all the
water you'll ever add.

When you recharge, you'll produce a bunch of water, too. You either dump it or
you store it for the next use. If you store it, then you double the amount of
storage that you need for water because you have room premix and postmix.

~~~
petre
You could use a cubic meter of solution and store the heat underground then
use a heat pump to extract it. But that could be also done directly by heating
the ground using excess solar. Lye seems better suited for daily storage -
store during the day, extract at night. Mostly useful in the desert or during
the spring/fall when day/nught temperature variations are high and solar
irradiation is good enough.

------
politician
(Wikipedia:) Worldwide production [of sodium hydroxide] in 2004 was
approximately 60 million tonnes, while demand was 51 million tonnes.

So it might be relatively cheap to acquire the working material.

~~~
Mizza
It's pretty horrible stuff though. I really don't think I'd want pipes full of
that in the basement of my home.

~~~
jaclaz
Personally I would have no problem to have that stuff in the basement, whilst
having it circulating in pipes just under the floor (you know, the heated
kind, where likely you go around barefooted) might be an issue. Also, consider
how on multi-storey houses the ceiling is nothing but the underside of the
upper floor. ;)

~~~
geon
I dont think the lye itself is supposed to circulate in the floor/radiators.
There would be a heat exchanger.

~~~
jaclaz
Sure, I do hope that those scientists are not totally irresponsible.

Still another heat exchanger will further lower the efficiency of the system.
In my experience (maybe a tad bit dated) common heat exchangers (water/water)
are difficult to maintain as - generally speaking - the most efficient ones
have smaller passages for the liquid and they tend to become clogged and it is
"normal" to clean them periodically.

I have no idea how large must be a heat exchanger (where one of the fluids is
lye) to be efficient enough, considering also that the temperature is
relatively low, but most probably it won't be exactly "compact".

------
ZeroGravitas
This reminded me of a similar system that uses the same tech as those hand
warmer things that have a chemical that changes state, either absorbing or
releasing energy. They also talk about absorbing heat and physically
transporting it. The example they have was waste heat from industrial
processes being shipped via canal to a district heating system.

[http://www.sunamp.com/](http://www.sunamp.com/)

------
mirimir
> The heated water generated in the process of condensation is then
> transferred to a geothermal probe (generally loops of pipes embedded
> vertically in the ground) for storage and retrieval.

That is a neat approach. It works well for solar-heated water. Where winters
are very cold and summers hot, one can also have cold-storage loops for summer
cooling.

I'm not sure about the NaOH thing, however. I get that it enables heat
transport. But as scotty79 notes, transporting concentrated NaOH is hazardous.
It's already done, of course. But the scale for heat transport would be much
greater than as chemical feedstock, I think.

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tmaly
I wonder how efficient this process is. The article did not state that figure.

~~~
failrate
Plus, the 50% recharge rate indicates that the medium would need to be
replaced every couple of years.

~~~
ars
I think you misread the article, that figure is the concentration diluted with
water.

------
ars
I usually find these types of new green technology to be impractical, and
obviously not going anywhere (store energy by dragging a train uphill for
example).

But this actually looks like it would work!

~~~
aaronbwebber
Why wouldn't storing energy by dragging a train uphill work? It's basically
the same as pumped hydro storage, and that's being used right now.

~~~
detaro
Let's assume a large example: trains weighing in sum 20 000 tons (e.g. 200
freight cars, each weighting 100 tons, probably distributed across a few
trains), and an incline with a _height difference_ of 1 km (which is going to
be _very_ long to be usable with heavy trains).

that's 20 000 000 kg * 9.81 N/kg * 1 000 m = 196 200 000 000 Nm or 55.4 MWh
stored energy (without efficiency factors, so not the usable energy at the
end).

In comparison, a stored-hydro plant typically has between 200 MWh to 3 GWh
capacity.

Maybe you could stack even more trains on it? But that again adds complexity
and costs (more locomotives needed). I'm not convinced it will work out in all
that many locations. And how fast can you transfer power in and out, with
limited train speeds and overhead wiring?

Stored hydro is simpler and at least just needs space to scale the capacity,
so you can make it a lot larger, even if it also only works in selected
suitable locations.

(Sorry for editing this so much, should have written it out in a text file
beforehand ;))

~~~
luminiferous
My understanding of the idea is that they plan to move the weights up the hill
by train, but then unload the weight. That way, with just one car, you can
move multiple cars' worth of weight up the hill. Now, this bottlenecks you on
how quickly you can store/release energy, and you have to store a lot of cargo
containers in a possibly small space, but even moving 4+ cars' worth of weight
per car brings the total stored energy capacity up to that of a smaller
stored-hydro plant. Not to say this is necessarily cheaper than stored hydro,
but it at least costs a lot less in terms of excavation.

------
btbuildem
Is this something that could be used in a dense urban residential setting?

Is the reaction extremely volatile? Does this require a high-tech ultra-low-
tolerances system, or can it be DIY-ed?

I can see having a setup on a condo balcony (esp. if you're facing south /
west), with heat exchangers on an otherwise-unused wall, and a few cylinders
of NaOH. As long as the kit doesn't blow the wall off the building if it leaks
or some such disaster..

~~~
klodolph
I'm not sure what you mean by "volatile reaction". NaOH is not super dangerous
but I wouldn't trust a DIYer with large quantities, since it's so alkaline.
You can find out more online by just searching for "MSDS sodium hydroxide" and
you'll find phrases like "very hazardous in case of skin contact".

A leak in some DIY setup would easily have horrific / disfiguring
consequences.

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steffenfrost
If the system scales based on the fluid, the $/kwh could get pretty low. Would
be interesting what a MWh amount of heat storage would cost.

~~~
petre
Assuming the 50% NaOH solution releases half the amount of heat released from
dissolving dry sodium hydroxide in water, to store 1 MWh you would need about
6.5 tonnes of sodium hydroxide. The price for NaOH pearls 99% is 300-400$ per
1 metric tonne.

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ChuckMcM
This is a really neat system. I wonder how many BTUs per liter you can store
...

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pdog
A simpler method is to grow crops and eat them.

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a-b
Is this about the global warming?

~~~
grzm
The article describes a method using NaOH for long-term storage and transfer
of heat, taking advantage of excess heat in the summer to use it during the
colder months of winter.

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sebyddd
There is a better solution already implemented..

[https://youtu.be/sbX6K7ky9LQ](https://youtu.be/sbX6K7ky9LQ)

