Building Material Absorbs and Releases Heat

Zothecula writes "Researchers at the Ningpo, China campus of the University of Nottingham (UNNC) have created a new heat-regulating material that could be used to cut the heating and cooling costs of buildings. The non-deformed storage phase change material (PCM) can be fixed so that it starts absorbing any excess heat above a pre-determined temperature and releasing stored heat when the ambient temperature drops below the set point. The researchers say the material can be manufactured in a variety of shapes and sizes, even small enough so that it can be sprayed as a microscopic film to surfaces in existing buildings."

Comments

Absorbs AND Releases?

[Jeremiah Cornelius]

Whoa! Just like... matter!

Can I patent this thermodynamics stuff?

Re:Absorbs AND Releases?

[Richard_J_N]

If it performs a phase change at a specified temperature, it means that there is a lot of extra thermal "capacitance" at one particular temperature. If we can choose that temperature to be, say 20 degrees C, this is useful. It would be a bit like water ice. As the freezer temperature falls from +1 to -1 degree, the ice releases a *lot* of stored heat (latent heat of fusion).

So, yes, this is a bit like building a large stone structure, which stays at a constant comfortable temperature by averaging out cold nights and hot days...but we don't need so much mass, and we can choose the temperature we want.

No credibility

[MrQuacker]

After all the articles about plagiarized and outright made up research in Chinese universities, I have to take every "discovery" they announce with huge skepticism.

Limited utility

[rgmoore]

Note that this kind of material only works to increase the heat capacity of the building, so it will only work when the temperature fluctuates across the phase change temperature over the course of the day. You'll still need a heater if it gets cold and stays cold and an air conditioner if it gets hot and stays hot. The big benefit is that the heat capacity only applies across a narrow temperature range, so it's relatively easy to maintain that temperature passively.

Re:Limited utility

[sjames]

It has limits, but it can save a LOT of energy. In some environments such as a desert, the average temperature is quite nice, but unfortunately it swings from freezing to over 100, so you need a good thermal mass to enjoy that average.

In other cases, the average temperature will not be comfortable, but a thermal mass can still save energy. For example when heating is needed, you can run a heatpump during the warmest part of the day when it runs more efficiently and rely on the mass during the coldest part.

All that said, thermal mass is nothing new, but the phase change at a useful temperature is an improvement on it.

Unless...

[Vario]

Yes, every material absorbs and releases heat.

The interesting bit here is something different though. I have never seen that someone wants to use a phase change material for buildings, but why not? For coffee cups this already works nicely. The walls of the mug contain a material that is undergoing some phase transition (liquid to solid, different crystalline structure, magnetic, etc.) at a temperature that is slightly below really hot coffee but still a nice drinking temperature.

What happens is the following: the thermal energy of the coffee gets absorbed quickly by the material, therefore cooling it down fast from really hot to a lower temperature. The material can store a large amount of thermal energy and releases it slowly so that the coffee stays at a constant temperature for much longer (gizmag article).

For a whole building this makes a lot of sense as well. It more or less acts as a large thermal reservoir, so that your wall temperature does not increase during the day and falls too much during the night. You could achieve a somewhat similar effect by using 20 inch stone walls but this might be a bit easier to incorporate into modern buildings.

The important part is the phase change

[Relic of the Future]

Yes, quick-but-not-entirely-wrong posters, everything absorbs and releases heat. The only reason this is interesting is because of the "PCM" part. If you actually recall your high-school physics, as heat is absorbed by an object, its temperature rises, UNTIL it reaches a phase transition; then the temperature stays constant until the phase change is complete. You probably did this with ice and water. The temperature of a chunk of ice starts below 32, increasing linearly with time, then it stops right at 32 and stays there until all the ice was melted, when it begins increasing linearly again.

This is useful for maintaining a consistent temperature inside when the outside temperature is bouncing above and below the temperature of the phase change (say, between day-time and night-time) rather than always needing to heat when it's cold and cool when it's hot. The PCM "building material absorbs and releases heat" automatically, in theory lowering your energy bills.

The neat thing--and yes, this IS neat--is a) this material is tunable; you can set the phase transition temperature at time of manufacture and b) it doesn't turn into a liquid, but rather changes between two different solid phases, which is nice for things like, you know, walls, that you'd like to stay solid.

And you were all so excited by this idea when Wozniak was pushing it in 2007; he'd latched onto a certain species of wood whose sap underwent a phase change at 72 degrees. Build a house out of that, and it will tend to keep the inside temperature at a Woz-friendly 72 degrees.

Re:The important part is the phase change

[Relic of the Future]

Oh, this is the 2007 article I was referring to: http://hardware.slashdot.org/story/07/08/14/2210203/Woz-Details-His-Plans-for-Energy-Efficient-House. Search for "pine sap".

Re:large storage of energy, huh?

[WindBourne]

Not a problem. It is from China. They will be using asbestos to handle this.