The theoretical limit for your thermal efficiency is going to be based on the temperature of whatever you are cooling and the temperature of the environment you exhaust the waste heat into. Minimizing the latter is what he seems to be talking about here.
Since these equipment cannot
operate with perfect efficiency, they will need to eliminate waste heat.
Who says it has to operate at perfect efficiency? I would imagine that any slight improvement you get by incorporating a black hole into your cooling system (however the hell that would work) would be negated by the fact that a cooling system that involves a black hole is probably a bit expensive.
It might not be. Assuming you could find a black hole which is not actively engaged in swallowing something (and hence spewing out huge amounts of heat and relativistic particle jets), you could surround it with mirrors to create an internal volume with a very low photon temperature at relatively (in astronomical terms) mild expense.
Obviously a spherical shell would be unstable, but you don't need a contiguous shell to lower the internal temperature. A rotating ring (or easier, an orbiting series of small, overlapping satellites) would be stable (not in the orbital sense, but in that they wouldn't need to hold themselves up) and could use the thermal gradient between their sides to power their station-keeping. You could construct additional rings at greater distances, each with a different inclination, to cover more of the angular area.
This was actually explained in the article, which is about cooling things down close to absolute zero. I haven't thought about this enough to see if it makes sense, but the claim is that:
It's not too difficult to cool a system down to the temperature of the cosmic background radiation. All you need to do is build a radiator in interstellar space with a very large surface area, and connect it with the system you're trying to cool with some high thermal-conductance material.
However, even at the cosmic background temperature of T=3K, erasing a bit still costs a minimum of kTln 2 = 2.87e-23 J. What is needed is a way to efficiently cool a system down to near absolute zero. I think the only way
to do it is with black holes.
The black hole is colder than the average temperature of space. Computation costs less at low temperatures, because temperature is defined as the ratio between the change in the energy and the change in the entropy of a system.
But assuming your radiator is going to be hot anyway (we've got a Dyson sphere to produce all this problematic energy, right?) then surely it's not that big a deal?
Still, it gets me thinking science-fictionally. Are there any stories where aliens invade the Earth just to use it as a heatsink? Travelling around from star to star, dumping all your waste heat into whatever planets you can find -- sounds like a great lifestyle.
Agreed. Indeed, if you follow the concept of Matrioshka shells or brains (http://en.wikipedia.org/wiki/Matrioshka_brain), when energy is released as heat after computation another layer sitting outside the previous one takes advantage of the heat to power further computation. By placing enough shells going outward, you effectively release very little energy. Possibly less than or equal to the CMB.
Comments
I'm confused. How is radiating your heat into a black hole better than radiating your heat into space?
The theoretical limit for your thermal efficiency is going to be based on the temperature of whatever you are cooling and the temperature of the environment you exhaust the waste heat into. Minimizing the latter is what he seems to be talking about here.
Since these equipment cannot operate with perfect efficiency, they will need to eliminate waste heat.
Who says it has to operate at perfect efficiency? I would imagine that any slight improvement you get by incorporating a black hole into your cooling system (however the hell that would work) would be negated by the fact that a cooling system that involves a black hole is probably a bit expensive.
It might not be. Assuming you could find a black hole which is not actively engaged in swallowing something (and hence spewing out huge amounts of heat and relativistic particle jets), you could surround it with mirrors to create an internal volume with a very low photon temperature at relatively (in astronomical terms) mild expense.
Obviously a spherical shell would be unstable, but you don't need a contiguous shell to lower the internal temperature. A rotating ring (or easier, an orbiting series of small, overlapping satellites) would be stable (not in the orbital sense, but in that they wouldn't need to hold themselves up) and could use the thermal gradient between their sides to power their station-keeping. You could construct additional rings at greater distances, each with a different inclination, to cover more of the angular area.
This was actually explained in the article, which is about cooling things down close to absolute zero. I haven't thought about this enough to see if it makes sense, but the claim is that:
It's not too difficult to cool a system down to the temperature of the cosmic background radiation. All you need to do is build a radiator in interstellar space with a very large surface area, and connect it with the system you're trying to cool with some high thermal-conductance material.
However, even at the cosmic background temperature of T=3K, erasing a bit still costs a minimum of kTln 2 = 2.87e-23 J. What is needed is a way to efficiently cool a system down to near absolute zero. I think the only way to do it is with black holes.
The black hole is colder than the average temperature of space. Computation costs less at low temperatures, because temperature is defined as the ratio between the change in the energy and the change in the entropy of a system.
But assuming your radiator is going to be hot anyway (we've got a Dyson sphere to produce all this problematic energy, right?) then surely it's not that big a deal?
Still, it gets me thinking science-fictionally. Are there any stories where aliens invade the Earth just to use it as a heatsink? Travelling around from star to star, dumping all your waste heat into whatever planets you can find -- sounds like a great lifestyle.
Agreed. Indeed, if you follow the concept of Matrioshka shells or brains (http://en.wikipedia.org/wiki/Matrioshka_brain), when energy is released as heat after computation another layer sitting outside the previous one takes advantage of the heat to power further computation. By placing enough shells going outward, you effectively release very little energy. Possibly less than or equal to the CMB.