[micw]

Thank you so much. It's the first time I do understand the _why_ of that fact.

But I could build up a lot of solar panels and use the electricity to heat up an oven more than the surface of the sun, right? Is that "cheating" in terms of thermo dynamics?

[p1mrx]

> I could build up a lot of solar panels and use the electricity to heat up an oven more than the surface of the sun, right?

Yes, this would be like using a hydroelectric dam to power a fountain that sprays higher than the initial reservoir. Machines can convert a large amount of low-quality energy into a small amount of high-quality energy, even when passive components (e.g. mirrors or pipes) cannot.

[micw]

So what is a "passive component"? I guess, a water wheel that drives a pump that pupms water way above the surface level would count as active?

What about a material that absorbs photons and emitts them at a higher energy level (emitting one after absorbing two)?

[hakonjdjohnsen]

Great question, and this shows why we could never get a 100% efficient solar panel. Otherwise your scheme would brak thermodynamics.

The most efficient possible way to convert sunlight to electricity is ~86% and is related to the second law of thermodynamics. So we use the heat flow from a hot reservoir (sun) to a cold reservoir (earth) and are able to convert some of that heat into work (electricity) which can then be used to heat something else to a higher temperature without breaking the second law.