A sun valve (''Swedish: solventil'', "solar valve") is a

flow control valve A flow control valve regulates the flow or pressure of a fluid. Control valves normally respond to signals generated by independent devices such as flow meters or temperature gauges. Operation Control valves are normally fitted with actuators a ...

that automatically shuts off gas flow during daylight. It earned its inventor

Gustaf Dalén Nils Gustaf Dalén (; 30 November 1869 – 9 December 1937) was a Swedish Nobel Laureate and industrialist, engineer, inventor and long-term CEO of the AGA AB, AGA company and inventor of the AGA cooker and the Dalén light. In 1912 he was award ...

the 1912

Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...

. Subsequently other variants of sun valve were developed for various different uses.

Dalén's valve

The valve was the key component of the

Dalén light A Dalén light is a light produced from burning of carbide gas (acetylene), combined with a solar sensor which automatically operates the light only during darkness. Overview The technology was the predominant form of light source in lighthouse ...

used in

lighthouses A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a beacon for navigational aid, for maritime pilots at sea or on inland waterways. Lighthouses mark ...

from the 1900s through the 1960s, by which time electric lighting was dominant. Prominent engineers, such as

Thomas Edison Thomas Alva Edison (February 11, 1847October 18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation, mass communication, sound recording, and motion pictures. These inventio ...

, doubted that the device could work. The German patent office required a demonstration before approving the patent application.

Design

The valve is controlled by four metal rods enclosed in a glass tube. The central rod that is blackened is surrounded by the three polished rods. As sunlight falls onto all of the rods, the absorbed heat of the sun expands the dark rod, switching a valve to cut the gas supply. After sunset, the central rod cools down, contracting to become the same length as the polished rods and opening the gas supply. The gas is lit by the small, always-burning pilot light.

Reliability

Dalen's system of acetylene lighting for marine navigation proved very reliable, as exemplified by the lighthouse at

Chumbe Island Chumbe Island is a small privately owned island a few kilometres off the main island of Zanzibar, known for its ecological innovation and exceptional coral reefs. In 1992 the fringing reef west of Chumbe Island was officially closed to fishing, ...

off

Zanzibar Zanzibar (; ; ) is an insular semi-autonomous province which united with Tanganyika in 1964 to form the United Republic of Tanzania. It is an archipelago in the Indian Ocean, off the coast of the mainland, and consists of many small islands ...

. This lighthouse was constructed in 1904 and converted to unstaffed automatic acetylene gas operation in 1926. The acetylene lighting installation, controlled by a sun valve, remained in use until the lighthouse was converted to a solar-powered (

photovoltaic Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...

) system in 2013.

Other variants

In 1921 Francis Everard Lamplough (an engineer with AGA's rival firm in lighthouse provision:

Chance Brothers Chance Brothers and Company was a glassworks originally based in Spon Lane, Smethwick, West Midlands (formerly in Staffordshire), in England. It was a leading glass manufacturer and a pioneer of British glassmaking technology. The Chance fami ...

) patented an alternative 'light valve' in the hope of breaking Dalén's effective monopoly. In subsequent years it was installed on several lighthouses and beacons, but because of its dependence on liquid it could only be used in static locations (unlike Dalén's valves, very many of which were installed on floating buoys). Lamplough's 'valve' was a form of

rocker switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type ...

, on which were mounted two glass bulbs, one black, the other clear, part-filled with liquid ether and linked by a tube. During the day, heat from the sunlight would cause the air in the black bulb to expand, forcing the liquid into the clear bulb, the additional weight tipping the switch and cutting off the current to the lamp; at night, or at other times of insufficient daylight, the process was reversed, reconnecting the current. In 1935 one Edwin H. Pendleton was granted a

US patent Under United States law, a patent is a right granted to the inventor of a (1) process, machine, article of manufacture, or composition of matter, (2) that is new, useful, and non-obvious. A patent is the right to exclude others, for a limited ...

for a sun valve activated by a pair of

bimetallic strip A bimetallic strip is used to convert a temperature change into mechanical displacement. The strip consists of two strips of different metals which expand at different rates as they are heated. The different expansions force the flat strip to be ...

s.Patent No. US1997598
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References

{{physics-stub Valves