The sun’s energy has been utilised by humanity since around 7 B.C. when the Greeks used glass to start fires and mirrors to concentrate solar radiation to set enemy ships on fire. They also began to build their houses taking the sun’s rays into consideration however it was the Romans who used glass in windows to trap solar heat in their homes. The Romans were also the first to build greenhouses, which allowed for the growth of exotic plants and seeds, recognising the efficiency of solar energy.

It wasn’t until much more recently that the true potential of solar energy was recognised. Edmond Becquerel is credited with the discovery of photovoltaic energy when in 1839 he discovered that shining light on an electrode submerged in a conductive solution created an electric current.

In the 1870s, Willoughby Smith, an electrical engineer, discovered photoconductivity in solids using selenium and soon after William Grylls Adams and his student Richard Day discovered that when exposing a selenium and platinum junction to light, a photovoltaic effect occurs. However, it was US inventor Charles Fritts who gave solar power its potential. He created the first functioning solar cell in 1883 which was the first device to ever convert solar energy to electricity. Using coated selenium as a semiconductor material with a thin layer of gold, these early solar cells only produced a conversion efficiency rate of 1% however the principle was instrumental in the development of solar power.

In 1887, Heinrich Hertz’s observations of the photoelectric effect and production and reception of electromagnetic waves led to further research being done. Aleksandr Stoletov, a Russian physicist, studied the photoelectric effect and discovered the direct proportionality between the intensity of light and the induced photocurrent as well as discovering the fatigue of solar cells. Both these discoveries helped further the understanding of solar energy’s potential.

Einstein published a paper in 1905 on the theory behind the photovoltaic effect which he won a Nobel Prize for in 1922.

A huge development in solar energy came in 1954 when physicists at Bell Labs exhibited the first high-power silicon solar cell that increased energy efficiency by using silicon rather than selenium. This led to the commercial availability of photovoltaic panels in 1956 and the use of solar as the main source of power for orbiting satellites. Initially, the cost of solar panels was high however by 1970 it had dropped by about 80% which allowed for alternative uses of solar panels to be researched and adopted.

early solar panel powering a radio

In the 90s, Germany and Japan were the first countries to introduce subsidy programmes for solar roofs which helped propel the development of solar energy being used for residential purposes. Since then, solar panels have become increasingly efficient, lightweight and flexible with continued innovation happening in the solar power market. In the late 2010s the cost of PV modules fell which led to the beginning of large solar production factories and affordable residential solar systems. Nowadays, China, the US and Germany are the top three nations that use the most solar energy. With the increasing urgency to create a sustainable future, research and investment into solar power will no doubt continue and help the transition from fossil fuels to renewable energy.

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