Is there such a thing as a material that lets sunlight and heat through in only one direction, and reflects it back in the other direction.

I was thinking of a large pot or small tank of water with a lid made of this substance. Fill it with salty water, let it sit out in the sun for a few hours. Eventually it gets so warm inside that the water boils. Collect the steam and condense into fresh water.

Does such a material exist?

party_pants said:

Is there such a thing as a material that lets sunlight and heat through in only one direction, and reflects it back in the other direction.

I was thinking of a large pot or small tank of water with a lid made of this substance. Fill it with salty water, let it sit out in the sun for a few hours. Eventually it gets so warm inside that the water boils. Collect the steam and condense into fresh water.

Does such a material exist?

Yeah. Silvered on one side, black on the other.

¿ so a mirror ?

SCIENCE said:

¿ so a mirror ?

It’s called a “half-silvered mirror”.

There is also the “greenhouse”. Let’s high frequency electromagnetic waves through (light from the Sun) and stops low frequency electromagnetic waves (thermal infrared)

In civil engineering we use what is called e-glass which has tailored thermal transmission.

A non-reflective (half wavelength) coating selects specific wavelengths to transmit.

I also suspect that what is called a layered dielectric material can be used for this purpose.

vacuum, bit old fashioned but used in vacuated tube solar hot water

It already exists

Old types of solar hot water systems I used to use in the Negev desert would heat the water so much you’d have to turn the shower on, step back and watch steam coming charging out of the nozzle.

You don’t need some perfect vessel

Just metal painted/ tinged black water pipes sat under glass sheet.