A solar-powered watch or light-powered watch is a

watch A watch is a portable timepiece intended to be carried or worn by a person. It is designed to keep a consistent movement despite the motions caused by the person's activities. A wristwatch is designed to be worn around the wrist, attached ...

that is powered entirely or partly by a

solar cell A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.

History

A model produced from 1978 by the Riehl Time Corporation was simply described as running on solar power, but having "silicon power cells" that "absorb energy from natural sunlight, daylight, or an ordinary light bulb". Some of the early solar watches of the 1970s had innovative and unique designs to accommodate the array of

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 ...

solar cells needed to power them (Synchronar, Nepro, Sicura and some models by Cristalonic, Alba, Rhythm, Seiko and Citizen). In 1996,

Citizen Citizenship is a "relationship between an individual and a state to which the individual owes allegiance and in turn is entitled to its protection". Each state determines the conditions under which it will recognize persons as its citizens, and ...

started to sell analog light-powered watches under the

Eco-Drive Eco-Drive is a model range of watches manufactured and marketed worldwide by Citizen Watch Co., Ltd., powered primarily by light. As of 2007, the company estimated the drive system had eliminated the disposal of ten million batteries in Nort ...

name. Since their introduction, photovoltaic devices have greatly improved their efficiency and thereby their capacity. Watchmakers have developed their technology such that solar-powered watches had by 2009 become a major part of their range. Several other watch manufacturers also use solar technology, such as

Orient The Orient is a term for the East in relation to Europe, traditionally comprising anything belonging to the Eastern world. It is the antonym of '' Occident'', the Western World. In English, it is largely a metonym for, and coterminous with, the ...

.Orient Light-Powered Watches (Global Market)
Accessed 28 September 2014Orient Light-Powered Watches & Movement Manual (Global Market)
Accessed 28 September 2014List of Orient Watch Manual & Movement (Global Market)
Accessed 28 September 2014Orient Light-Powered Watches (Japan Domestic Market)
, Accessed 28 September 2014Orient Light-Powered Ladies Watches (Japan Domestic Market)
, Accessed 8 October 2014List of Orient Watch Manual & Movement (Japan Domestic Market)
Accessed 28 September 2014

Junghans Junghans Uhren GmbH is a German watch and clock manufacturer. The company is located in the district of Rottweil, in a town called Schramberg, Baden-Württemberg, southwest Germany. History On 15 April 1861 Erhard Junghans created the compan ...

Casio is a Japanese multinational electronics manufacturing corporation headquartered in Shibuya, Tokyo, Japan. Its products include calculators, mobile phones, digital cameras, electronic musical instruments, and analogue and digital watches. ...

, and

Seiko , commonly known as Seiko ( , ), is a Japanese maker of watches, clocks, electronic devices, semiconductors, jewelry, and optical products. Founded in 1881 by Kintarō Hattori in Tokyo, Seiko introduced one of the first quartz watches and the ...

. Inexpensive solar-powered watches were first sold in the 1980s and were popular amongst children, often featuring famous fictional characters such as

Transformers ''Transformers'' is a media franchise produced by American toy company Hasbro and Japanese toy company Takara Tomy. It primarily follows the Autobots and the Decepticons, two alien robot factions at war that can transform into other forms, ...

or G.I. Joe.

Technological details

Typically, sunlight and artificial light are absorbed by a solar panel behind the crystal. The dial is either on a layer above or actually on the solar panel. This solar panel converts the light into electrical energy to power the watch. The watch will usually store energy in a rechargeable cell to power itself during the night or when covered such as a wearer's clothing (e.g., sleeve). Citizen's watches use

lithium-ion batteries A lithium-ion or Li-ion battery is a type of rechargeable battery which uses the reversible reduction of lithium ions to store energy. It is the predominant battery type used in portable consumer electronics and electric vehicles. It also se ...

to store sufficient energy to power the watch for up to five years without light exposure, by allowing the watch to enter a power-saving or hibernation mode during which the seconds hand stops until the watch is re-exposed to light. Not all have a power-save mode, yet will still hold a charge for typically six months, as with uncomplicated (date only) analog versions made by Citizen.

References

{{Photovoltaics Applications of photovoltaics Solar-powered devices Watches Photovoltaics