What prevents us from turning heat into electricity with optical rectennas?

This is more about "if you can catch a radio wave with an antenna, why not an infrared photon".

We do since last year.

is this paraphrased moldbug?

efficiency is really poor.

We do?
You'd think that'd be big news.
Unless due to thermodynamical bullshit it STILL requires a heat gradient despite the fact that it's catching higher energy photons than a radio antenna.

sciencealert.com/world-s-first-optical-rectenna-converts-light-directly-into-a-dc-current

Neat, but can this be done for all frequencies of light?
Can I make a carpet of these antennas that will turn radio waves into a small amount of electricity, or the abundance of thermal radiation going around into a more substantial amount?

spectrum.ieee.org/semiconductors

Graphene

Materials science and nanofabrication probably. Probably switching speed of any nanodiode. Microwave radiation is already below a nanosecond period, and its wavelengths are in the mm-cm range. Reduce the wavelength by 6 orders of magnitude to get infrared and you reduce the wave period by 6 orders of magnitude too.

I'm just curious as to whether it's within the laws of physics to use those devices to turn the photons passed around in homogenous temperatures into electricity.

No, unfortunately - that IS a heat engine, and so second-law limits apply. (Solar panels also have fundamentally limited efficiency, for the same reason - it just isn't noticed very much, because the "thermal gradient" is the temperature difference between the solar panel and the photosphere of the Sun.)

Consider: If your antenna is at ambient temperature, it will emit as many photons due to thermal radiation as the room it's absorbing them from.

Emitting those photons is just radiating heat though; not electricity.

I'd save and reuse this if it wasn't for the part where he says Indonesia should be run by Islamist dictators, or infers that there's even a hint of them wanting that. That's just retarded.

You're talking about a multi-layered solar panel.

So the issue is that you can't extract useful energy (i.e. to perform work on a macroscopic scale) from simply heat. There needs to be a flow of heat from a warm reservoir to a cold reservoir. All heat engines work by harnessing this heat flow to produce useful energy output.

Can you clarify what you're asking? Are you proposing:

A) Using optical rectennas to convert heat into electricity? This is impossible due to my statement above.

B) Using optical rectennas to somehow convert a thermal gradient into electricity? It *is* possible to build heat engines that convert thermal gradients into electricity; however, I don't see how optical rectennas would accomplish this goal

C) Using optical rectennas to convert infrared radiation (e.g. from the sun) into electricity? This actually *is* possible in principle, although as far as I know, no one has yet fabricated such a device that is anywhere close to being efficient enough to be practical.

So can you please clarify what, specifically, you're asking?

awoo~!

A).
I haven't seen any proper explanation of why it's impossible though anywhere in the thread.

Have you ever heard of the second law of thermodynamics?

Do you even understand it or are you some retarded summerkid who pretends to know everything?

Have you read the thread?