Sun valve
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A sun valve (Solventil, "solar valve") is a form of flow control valve, notable because it earned its inventor Gustaf Dalén the Nobel prize in physics.
The valve formed part of the Dalén light which was used in lighthouses from the 1900s through to the 1960s by which time electric lighting came to dominate.
The valve is controlled by four metal rods enclosed in a glass tube. One rod is blackened, while the others are highly polished. As daylight passed through the glass tube, exposing the rods to the rays of the sun, photons are absorbed by the dark rod causing it to expand and cut off the gas supply.
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