Innovation and watchmaking: photovoltaic tests in the 1950s

Many innovations were introduced in Basel Fair on 1953. The most interesting was a revolutionary clock, the Pendulette Solaire, that proposed Patek Philippe as an historical Maison able to face the challenges of technological evolution. The innovation beyond the Pendulette Solarie was patented as “Énergie photoélectrique”.

Where does this clock come from? Watchmakers always looked for a free source of energy, but light has a relevant limit: rarely it’s available 24 hours per day. The firts photovoltaic clocks were able to stock energy mechanically, charging a spring able to power the clock during the night. Patek Philippe idea was to introduce an additional electric stock, through an accumulator, to provide the energy to wind the spring. Photovoltaic cells can thus allow to stock energy both elettrically and mechanically: when the spring is fully wound, a switch send the new energy to the accumulator.

Patek Philippe introduces in this way a peculiar technical combination: on one hand, the most advanced electronic innovation of the age (among which the very expensive photovoltaic cells), on the other hand the tradition of a mechanical manual winding watch movement. The photovoltaic cell, placed on the top of the clock, gives energy to the accumulator that, trough a switch, activates an engine that charges the movement.

Despite the brand new technology, results were excellent: solar panels guarantee a rapid charge, the accumulator has an autonomy superior to a month and the average daily variance is lower than a second.