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

watch A watch is a timepiece carried or worn by a person. It is designed to maintain a consistent movement despite the motions caused by the person's activities. A wristwatch is worn around the wrist, attached by a watch strap or another type of ...

that is powered entirely or partly by a

solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

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 membership and allegiance to a sovereign state. Though citizenship is often conflated with nationality in today's English-speaking world, international law does not usually use the term ''citizenship'' to refer to nationality ...

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 referring to the East in relation to Europe, traditionally comprising anything belonging to the Eastern world. It is the antonym of the term ''Occident'', which refers to the Western world. In English, it is largely a meto ...

.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 the town of Schramberg, Baden-Württemberg, southwest Germany. In 1903, Junghans was the largest watch factory in the world an ...

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. It ...

, and

Seiko , commonly known as Seiko ( , ), is a Japanese maker of watches, clocks, electronic devices, and semiconductors. Founded in 1881 by Kintarō Hattori in Tokyo, Seiko introduced the world's first commercial quartz wristwatch in 1969. Seiko is ...

. 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 Tomy, Takara Tomy. It primarily follows the heroic Autobots and the villainous Decepticons, two Extraterrestrials in fiction, alien robot fac ...

G.I. Joe ''G.I. Joe'' is an American media franchise and a line of action figures owned and produced by the toy company Hasbro. The initial product offering represented four of the branches of the U.S. armed forces with the Action Soldier ( U.S. Army), A ...

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 that uses the reversible intercalation of Li+ ions into electronically conducting solids to store energy. Li-ion batteries are characterized by higher specific energy, energy ...

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.

Advantages and disadvantages

The solar-powered watches has a number of advantages: *Eco-friendly: solar-powered watches reduce dependence on disposable batteries, helping to conserve the environment and reduce e-waste. *Low maintenance requirements: because solar-powered watches use rechargeable batteries, they need to be charged less frequently than traditional battery-powered watches. *Continuous operation: with the right light, the solar-powered watches can maintain a constant supply of energy, allowing continuous operation without the need for manual recharging or battery replacement. *Charging indicators: many solar-powered watches are equipped with charging indicators that show the charge level or when the watch is actively charging, providing users with information on the state of charge. Overall, the solar-powered watches combines the functionality of accurate timekeeping with eco-friendly technology. Disadvantages of solar-powered watches: *The initial cost may be higher than traditional watches. One of the biggest disadvantages of solar-powered watches is their initial cost. These watches tend to be more expensive than their traditional counterparts because of the advanced technology used in their manufacture. *Requires sufficient exposure to sunlight to maintain charge. One of the most significant disadvantages of solar-powered watches is their dependence on sunlight. Without sufficient exposure to sunlight, this watch will not be able to charge the batteries and therefore will not work.

References

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