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What the thermodynamic principle says you can't do is to take Q units of heat energy from one body and transfer it all to a higher temperature body. The solar
by caf 8y ago
What the thermodynamic principle says you can't do is to take Q units of heat energy from one body and transfer it all to a higher temperature body.
The solar panel system is different - it's a heat engine that takes Q units of heat energy from one body, transfers a portion of it Q₁ to a higher temperature body and transfers the remainder of it (Q - Q₁) to a lower temperature body (the immediate surroundings). That's OK with thermodynamics, subject to upper bounds on the ratio Q₁/Q that depend on the absolute temperatures of the bodies involved.
This suffices to show that the perfect lens system can't work. The dusty lens system can't work because adding dust to a perfect lens doesn't turn it into a heat engine.
- jarfil 8y ago> you can't do is to take Q units of heat energy from one body and transfer it all to a higher temperature body Except it's not "heat energy", it's electromagnetic energy that's getting transferred. If the target object is smaller than the source object, you can have an amount of energy that will increase the target's heat above that of the source.
- schoen 8y agoI don't think it could remain above the source temperature in equilibrium, because it will radiate back toward the source!
- amelius 8y ago> Except it's not "heat energy", it's electromagnetic energy that's getting transferred. Thermal radiation == electromagnetic radiation.
- gowld 8y agoIt's impossible to aim the source at a smaller target because the source dissipates in all directions, unless you make something like a laser.