19.02.2019 | Alexandre Edmond Becquerel and the story of photovoltaics

How the solar cell found the spotlight

Photovoltaics is still a rather new industry although its underlying principle, the photoelectric effect, had already been discovered by Alexandre Edmond Becquerel in 1839. However, it was only after the oil crisis of 1973 that solar energy really took off. Switzerland played an important role in this development.

Photovoltaics transforms incoming light into electrical energy. Its underlying principle, the photoelectric effect, was discovered in 1839 by Alexandre Edmond Becquerel (1820 - 1891). While experimenting with electrolytic cells to which he attached an anode and a cathode made of platinum he measured the current flowing between these two electrodes. He noticed that there was virtually no difference in the amount of current under luminous or dark conditions. He had discovered the basis of photovoltaics, although practical implementation would only take place generations later.

Alexandre Edmond Becquerel
Fundamental research

Various engineers and researchers worked in this area during the 19th century. The New Yorker Charles Fritts built the first module from selenium cells in 1883 and in doing so created the precursor to the photovoltaic module. This prompted various fundamental research on the photoelectric effect.

However, it was not until 1907 that Albert Einstein provided a theoretical explanation for the photoelectric effect: Light was not only wave-like radiation, but could also be interpreted as the flow of tiny energy packets with characteristics similar to material. In 1921, he was awarded the Nobel Prize in Physics for his light-quantum hypothesis.

In 1940, Russell S. Ohl determined that electricity could be generated through the illumination of silicon. At Bell Laboratories in New Jersey (USA), Ohl was also involved in the discovery of the mechanism to change the electrical properties of semiconductors by precisely adding impurities to the material. The first round 2-centimetre, crystalline silicon solar cell with an efficiency of over four per cent was manufactured at Bell Laboratories and presented to the general public in 1954. Today most solar cells are made of silicon crystals.

In use: Solar energy in space
Deployment in space

Only four years after this breakthrough photovoltaics took off for the first time. The US satellite Vanguard 1 was equipped with 108 solar cells.

The success with this small satellite motivated scientists to continue developing this virtually unknown and very costly solar cell technology for aerospace. The cells proved to be the ideal power supply for satellites and space probes – and they still are to this day.

Switzerland at the forefront

However, these photovoltaic modules were still much too expensive for terrestrial use. They were very rarely implemented and only in remote areas far away from the next energy grid. The oil crisis of 1973 changed all this. In particular, the USA focused strongly on research in this area, and continued to develop the modules until they were launched for initial commercial use. No wonder the US share on the worldwide photovoltaic market was about 21 per cent in 1983, although these were often large-scale photovoltaic plants.

The idea of using numerous, smaller decentralised systems instead of large-scale systems originated in Switzerland. The ETH professor Pierre Fornallaz recognised the "charm of decentralisation". The Swiss engineer Markus Real also focused on this area after seeing photovoltaic systems in use in the USA. In 1979, he built the first such system in Switzerland on the roof of a tool shed in Würenlingen (AG), connected it to the power grid, and achieved another record: The first grid-coupled solar plant in Europe. In the summer of 1986, he launched a major project for the construction of 333 decentralised solar plants (3 kWp plants) and found enough home-owners who were prepared to pay CHF 41,000 to have a plant installed on their roofs. (What this costs today and how it works here). 

The campaign for photovoltaics in Switzerland was promoted further with the Tour de Sol (a solar vehicle race through Switzerland/1985 to 1993) and in 1992 Elektrowatt AG and BKW achieved a milestone on the Mont Soleil – a solar plant with a capacity of 500 kWp, the largest plant in Europe at that time.

Later on political subsidies became the main drivers for the installation of photovoltaic plants. In particular, the EEG levy in Germany. Today our neighbour along with China, the USA and Japan is among the countries with the highest installed photovoltaic capacity, totalling over 4000 GWp worldwide (see graphic/2017).

Source/Graphics: IEA/Volker Quaschnig

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