6 ms·

The thing is a pound of copper has a pretty significant specific heat, and that’s a feature rather than a bug. A thin graphene film may be more conductive, but

The thing is a pound of copper has a pretty significant specific heat, and that’s a feature rather than a bug. A thin graphene film may be more conductive, but what is it thermal capacity? If it’s just a thin film that gets blazing hot it’s not necessarily useful in that way.

ineedasername 8y ago
True. It looks like they made a few square centimeters of this stuff. If they make a bit more and slap it on a coffee mug & eliminate the need for a microwave, there could be some very interesting applications. Though also consider their applications weren't limited to desalination and other "macro" applications, but also electronics, sensors and such. It sounds like this might be significantly cheaper than current monolayer graphene on substrate.
- Zenst 8y ago
  Only if the thermal transfer is one way, otherwise you may find your coffee getting colder quicker as surfaces that capture heat, equally have a penchant to radiate it. For example two metal balls, one painted white, one painted black. Whilst in the sun the black one will heat up more than the white one, at night it will radiate heat much quicker - even if they start at the same temperature. Though the prospect of sending a coffee mug that only works in the sun to some geeks I know, does bring with it some wry humour opportunities. As for other uses, agreed, much potential if it has an edge over alternative offerings.
  - meruru 8y ago
    That example sounds wrong. My understanding is that the black ball will heat up more quickly because it's converting a wider range of light frequencies into heat. The color isn't affecting heat conductivity and thus shouldn't affect how quickly it cools down at night.
    - phonypc 8y ago
      Not conductivity, but emissivity. In theory anyway, I'm not sure if plain black paint would make a difference.
    - ethbro 8y ago
      https://physics.stackexchange.com/questions/159856/why-is-black-the-best-emitter https://physics.stackexchange.com/questions/159856/why-is-bl...
      - meruru 8y ago
        I used to think that the darker the object, the more light it was turning into heat. Is that idea just plain wrong or is there some correlation? Are dark objects dark just because the light they emit are in an invisible frequency range?
        Zenst 8y ago
        The colour of an object we see is based upon light refracted back. So if an object is black it is absorbing most of the light, and the classic grass - which appears green is actually absorbing the red and blue spectrum and reflecting back the green light - appearing green. "Are dark objects dark just because the light they emit are in an invisible frequency range?" the light they reflect back may well encompass the non visible spectrum, after all that's how radar works and the drive for radar absorbing materials by the military. So not all objects that for us in out limited light spectrum visual senses are equal, even if they look the same - black. May be one reflects back UV, one may absorb it. So for a true picture you would need to see an absorption graph of the full spectrum (visible and non visible). Crux is - objects we see via refracted light - we are seeing in negative. So whilst we see green grass, it's true colour is everything but green.
        phonypc 8y ago
        >So whilst we see green grass, it's true colour is everything but green. I've never liked this phrasing. In what sense is the "true" color not green if we perceive green? It is the color it reflects, it's just a little counter-intuitive when you first learn of the physics behind it.
andrewflnr 8y ago
Water has a much higher specific heat. If you just want to heat up water anyway, wouldn't you just transfer the energy to it as fast as possible?
- x86_64Ubuntu 8y ago
  Specific heat and thermal conductivity are two different properties.
  - thaumasiotes 8y ago
    Sure, but this is a terrible answer to the question "why do we care about specific heat? Wouldn't thermal conductivity be more relevant?" That question already assumes that specific heat and thermal conductivity are different properties.
    - awakeasleep 8y ago
      With copper you have 'heat battery' and can heat additional water by running it through the system without waiting for an equivalent amount of sunlight.
keerthiko 8y ago
this makes copper a great heatsink but not a very good solar heater medium

ineedasername 8y ago

True. It looks like they made a few square centimeters of this stuff. If they make a bit more and slap it on a coffee mug & eliminate the need for a microwave, there could be some very interesting applications. Though also consider their applications weren't limited to desalination and other "macro" applications, but also electronics, sensors and such. It sounds like this might be significantly cheaper than current monolayer graphene on substrate.

Zenst 8y ago
Only if the thermal transfer is one way, otherwise you may find your coffee getting colder quicker as surfaces that capture heat, equally have a penchant to radiate it. For example two metal balls, one painted white, one painted black. Whilst in the sun the black one will heat up more than the white one, at night it will radiate heat much quicker - even if they start at the same temperature. Though the prospect of sending a coffee mug that only works in the sun to some geeks I know, does bring with it some wry humour opportunities. As for other uses, agreed, much potential if it has an edge over alternative offerings.
- meruru 8y ago
  That example sounds wrong. My understanding is that the black ball will heat up more quickly because it's converting a wider range of light frequencies into heat. The color isn't affecting heat conductivity and thus shouldn't affect how quickly it cools down at night.
  - phonypc 8y ago
    Not conductivity, but emissivity. In theory anyway, I'm not sure if plain black paint would make a difference.
  - ethbro 8y ago
    https://physics.stackexchange.com/questions/159856/why-is-black-the-best-emitter https://physics.stackexchange.com/questions/159856/why-is-bl...
    - meruru 8y ago
      I used to think that the darker the object, the more light it was turning into heat. Is that idea just plain wrong or is there some correlation? Are dark objects dark just because the light they emit are in an invisible frequency range?
      - Zenst 8y ago
        The colour of an object we see is based upon light refracted back. So if an object is black it is absorbing most of the light, and the classic grass - which appears green is actually absorbing the red and blue spectrum and reflecting back the green light - appearing green. "Are dark objects dark just because the light they emit are in an invisible frequency range?" the light they reflect back may well encompass the non visible spectrum, after all that's how radar works and the drive for radar absorbing materials by the military. So not all objects that for us in out limited light spectrum visual senses are equal, even if they look the same - black. May be one reflects back UV, one may absorb it. So for a true picture you would need to see an absorption graph of the full spectrum (visible and non visible). Crux is - objects we see via refracted light - we are seeing in negative. So whilst we see green grass, it's true colour is everything but green.
        phonypc 8y ago
        >So whilst we see green grass, it's true colour is everything but green. I've never liked this phrasing. In what sense is the "true" color not green if we perceive green? It is the color it reflects, it's just a little counter-intuitive when you first learn of the physics behind it.

andrewflnr 8y ago

Water has a much higher specific heat. If you just want to heat up water anyway, wouldn't you just transfer the energy to it as fast as possible?

x86_64Ubuntu 8y ago
Specific heat and thermal conductivity are two different properties.
- thaumasiotes 8y ago
  Sure, but this is a terrible answer to the question "why do we care about specific heat? Wouldn't thermal conductivity be more relevant?" That question already assumes that specific heat and thermal conductivity are different properties.
  - awakeasleep 8y ago
    With copper you have 'heat battery' and can heat additional water by running it through the system without waiting for an equivalent amount of sunlight.

keerthiko 8y ago

this makes copper a great heatsink but not a very good solar heater medium