History of solar energy, from the sundial to the Fritts solar cell

The sundial

The sundial does not actually use solar energy as a source of energy, rather it represents a historic milestone as it harnessed sunlight for the first time to operate an apparatus for measuring time.

The Egyptians were the first to use sundials, orienting their buildings in such a way that the shadow created marked the hours of the day. The ziggurats of Mesopotamia featured steps on which the shadow projected marked the time of the day. The Old Testament even included a mention of one of these clocks: the Dial of Ahaz.

In 1500 BC, during the reign of Egyptian pharaoh Thutmose III, the sechat was first used; this sundial measured time by looking at the length of the shadows generated. This sundial boasted the advantage of being portable, unlike when buildings or staircases were used.

Sundials have proved very useful to later civilisations. For example, in Rome, the solarium was a sundial located in a central area of the city, allowing all citizens to consult the time. It served as a meeting place in Roman cities, as is now the case of the clocks on city halls or bell towers in some European cities.

In terms of portable clocks, at the Archaeological Museum of Madrid, a veritable jewel is on display: the Schniep Sundial, owned by the Duke of Alba. This scientific instrument was developed in 1548 in Munich by a famous craftsman and optimised for the geographical location of the Iberian peninsula.

Archimedes' burning mirror

Around 214 BC the Roman fleet was trying to conquer the Greek city of Syracuse by sea. As legend has it, Archimedes placed mirrors at strategic enclaves to reflect sunlight and project it onto the flammable areas of Roman ships.

The concentrated heat started several fires that baffled the Romans and plunged them into a state of paranoia, in the belief that an invisible enemy was outwitting them. As a result, they were forced to abandon their attack and maintain the siege. This ploy to use the energy generated by the Sun and concentrate it through mirrors has been the source of debate since ancient times.

There is still no absolute certainty as to whether this episode in the history of solar energy has more to it than meets the eye. However, mirrors are still used to this day at certain types of solar plants to concentrate the sun's energy.

The Roman greenhouses

In Spain, we are more accustomed to hearing about the greenhouses in Almeria; however, when it comes to the history of solar energy, the pioneers in using this invention were the Romans.

Greenhouses harness the sunlight that passes through a translucent material (glass, plastic) to increase the temperature inside. This way, it is possible to increase the indoor temperature to improve the crops, especially at cold times of the year when certain plants would not be able to produce food.

While Tiberius was in power, the first greenhouses in ancient Rome were created. Tiberius consumed a wide range of vegetables, mainly cucumbers, at the recommendation of his doctors.

To improve the cultivation of these vegetables, portable greenhouses were conceived, made using sheets of glass (mica extracted from the mine, which let in sunlight) and alabaster. When the weather was good, or during the day, the pots containing the vegetables were taken out into the sun and at night or during cooler periods, they were placed inside the structure.

Based on this principle used by Roman greenhouses, the first static greenhouses were built in Italy and Spain during the sixteenth and seventeenth centuries to cultivate the new species transported from the Indies. The first major greenhouse, as we know them today, was L’Orangerie, in Versailles, built in the seventeenth century to grow oranges, a very expensive and precious product in Europe at the time.

Wilson's desalination plant

Everybody can imagine how difficult it is to obtain water in the desert today. Now imagine the difficulties experienced by the mining towns in the Atacama Desert (Chile) in the nineteenth century.

An ingenious solution to these problems was found by Charles Wilson in 1872 in another of the great milestones in the history of solar energy.

Wilson was tasked with the design and construction of a system that extracted salt water from a 40-metre-deep well, operated using a windmill. From there, water was driven towards a reservoir, where it was collected and stored in drawers with a black painted background and a glass lid.

When these boxes were left in the sun, solar energy facilitated the evaporation of water, which was stored in a drinking water container. The wind in the Atacama Desert also favoured condensation, as it is cold and constant.

The chronicles of the time assert that in the summer months, it managed to distil around 18,000 litres of water per day.

Becquerel's photovoltaic cell

French physicist Alexandre-Edmond Becquerel is considered to have discovered the photovoltaic effect, which involves capturing sunlight and converting it into energy. In 1838, at just 19 years of age, a young Becquerel, the son and father of notable scientists, also felt science calling.

When Becquerel was studying Faraday's laws of electrolysis using an electrolytic battery with platinum electrodes, he realised that the electric current produced by the battery was triggered in one of the electrodes when it came into contact with sunlight.

Just one year later, he published his study "on electric effects under the influence of solar radiation", opening the door to new ways of harnessing solar energy and improving efficiency. This represented a major step forward in the history of solar energy when it comes to promoting electricity generation.

Fritts' solar panel

Fritts' studies on solar panels, published in 1833, marked the birth of photovoltaic energy and the use of sunlight to generate electricity without the need to use fossil fuels.

Just 50 years after the discovery of the Becquerel photovoltaic cell, American inventor Charles Fritts created the first photovoltaic cell in history. His research, published in the article "On a New Form of Selenium Photocell", informed the world of the first way to transform solar energy into electricity.

Fritts used a glass box with a sheet of selenium placed between two sheets, one made of gold and one made of brass. The light received caused the electrons to move through the selenium and the electric current came out of a wire that Fritts had included at one end of the box.

Despite this major achievement in the history of solar energy and the promising advance represented by Fritts' solar panel, the high cost of the materials and the low use of sunlight (1%) meant that other energies took the lead when it came to generating electricity.

However, scientific and technological progress has made the production of efficient solar panels must more efficient, based on the same principles as Fritts' solar panel.

Each and every one of these inventions in the history of solar energy has made it possible for us to move towards a more sustainable world and towards the production of electricity using renewable sources.

Now, progressively more people choose to install solar panels in their homes to save on their electricity bills and form part of the world of self-consumption. Tariffs like Tempo Solar self-consumption help you to reduce your electricity bill with a very economical price for the times of the day when your solar panels are unable to provide you with the energy you need.

For people who cannot install photovoltaic panels, it is still possible to consume electricity in a much greener way, thanks to green electricity tariffs, as part of which you only consume sustainable energy generated by renewable sources like solar energy or wind energy.