A white Librem 5 for keeping it cooler?

I would like to discuss if a white L5 would have advantages compared to the black one.

So the black L5 will absorb the energy of the sunlight, while the white one will reflect it. Devices can get pretty hot by this and hence it is generally adviced not to use electronic devices under direct influence of sunlight.

I am not so sure how much energy can be transfered to the black L5 by other common sources of electromagnetic radiation like IR radiation of the human body or heaters, cookers and ovens.

Another thing is that sunlight attacks plastics. Over time they can get yellow and brittle. I wonder if a white L5 will suffer less from this effect than a black one.
Maybe this is not the mist important criteria but due to the high repairability and lifetime software updates the L5 has the potential to be in use in for many years and this effect might be considered. Anyway it would be interesting to know if black plastics break faster than whites.

From my understanding non black plastics break faster since their UV light absorber need to be of white color as well and there are no white UV absorber materials that last forever, where as one of the most common UV absorber for black plastic is carbon black which more or less lasts forever embedded within the plastic.

I still like the idea of a white anodized Aluminum body with a black front and back

So common white plastics don’t reflect UV radiation but absorb them?

Not exactly sure if the UV light is absorbed or reflected but from what i remember of university course 10 years ago at least a small percentage is absorbed and destroys the UV protection parts within the plastic and when they are degraded enough the plastic gets destroyed by the UV rays.
AFAIK that was one if the reason why most of the plastic on the outside of cars was black cause carbon black was the only UV protection available that lasted long enough. But those are just generalizations and there might be some miracle additives to plastics that enables them to resist UV light longer.



Wheeee! So cool! :open_mouth:

I was also watching some recycling youtube video, and in UK black plastics are unrecyclable. But then again it was talking about the black plastics holding fresh food on the vegetable aisle. Probably not the same problem.

That’s because the system they use to sort plastics into different types (polyethene, polypropene, etc.) works by shining infrared light through the plastic and reading the absorption spectrum. Black dyed plastic blocks that entirely.

I forget what it was (probably a yoghurt pot lid), but one piece of packaging advertised that it was recyclable “black” plastic (and it was: hold it up to the light and you could see through it, it looked very dark green)

I like the idea of a silver/grey-ish metal with black along the lines of the HTC One M8, for example.

While out in the sun on a hot day, how much of a difference does it really make if a device is white or black? If it’s hot in the environment, only AC can help.

Black and white things both absorb “heat”, white things will reflect some of the “heat” and will therefore take longer to reach the “maximum” temperature. But both the black and the white thing will get to the same temperature, and with something as small as a phone the time different will be negligible.

And when the white phone is in your pocket you get Schrodinger’s phone :stuck_out_tongue:

The maximum temperature when exposed to Sun radiation is about 6000K, so the time to get there makes a significant difference :slight_smile:

There is a limit to how much heat energy the phone can absorb and it will also be generating its own heat and dissipating heat energy into the surrounding air.

The limit is reached when it evaporates (or melts away from the ray beam) :slight_smile:

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Right… but you’re mixing up the temperature of the sun with the temperature of the sun’s energy on Earth. You may have noticed we don’t melt when we sit in the sun too long.

The phone, like us, can dissipate the relatively weak heat energy it receives from the sun more quickly than it absorbs more energy. Both the black and white phone will get to the same point of equilibrium in about the same amount of time.

If the phone is turned off then this level is determined by the surrounding air temperature, and if in direct sunlight we can expect the phone to be slightly warmer than the surrounding air. When the phone is turned on then it will also be generating heat and can get considerably warmer than the surrounding air, but the colour of the phone will have almost no impact.

You got me. The actual temperature limit is going to be the temperature of the sky sphere: about 50% contribution from the ground (280K -ish), almost 50% from the sky (actually not sure what the black body temperature is from the atmosphere), and the small contribution from the Sun (6000K). That’s the temperature equilibrium from black body radiation only, easily calculated. If it’s high enough, albedo will affect the time to reach it significantly.

Convection effects will dampen the heat exchange somewhat, but I don’t think enough to ignore the effect from albedo. Just touch white and black cars in the sun.

Just touch white and black cars in the sun.

Not a particularly scientific test. If you touch a black stone on a hot day the stone will feel cold, if you touch a white stone it will also feel cold. Both stones will be the same temperature as the ambient air but they absorb heat from our body when we touch them so they feel cold.

But I will try touching a white and black car on a hot day to see what the difference is. I imagine they will both be very hot to the touch :slight_smile:

Edit: Actually now I think about it some stones get pretty hot in direct sunlight, so that was a bad example… Either way a white or black phone case won’t make a useful difference.

Try sitting inside a white car, then inside a black one on a very hot day.

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Well, for a more scientific test, using the procedure I described is very easy to calculate the target temperature of the phone. Then to get how long it takes to come close to the target, you could use the fact that black body radiates according to the 4th power of the temperature difference and look up the relevant equation to get power from that (sorry :F).

I don’t have a solution for convection effects, I never properly learned that :frowning:

Have you actually tired that? Because it is plain false, at least with the stones in my area. Also, why do lizards rest on stones in early spring on a sunny day?

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I would imagine if the stone lays in the river (i.e. discharging the heat into the running water or any other cooling substance, eg damp soil or crispy frosty air) - this test will be true.