Solar technology, although pervasive and modern, was not invented overnight. It took more than two centuries to perfect the art of tapping energy from the sun. Yet the inspiration behind solar panels has not changed over time – that brightest of stars – the sun!
The sun’s unleashed energy gives us life. Plants use sunlight to make their own food, which in turn feed animals. Humans depend on plants and sometimes animals for nourishment.
Trapping this abundant and constant solar energy can also help channel its effects for specific needs. With the use of “solar collectors” such as photovoltaic (PV) cells on rooftops, children in remote places can study at night. With bigger PV panels on stadiums, fans can enjoy an uninterrupted game of sports, long after the sun has set.
It’s true solar technology has come a long way. But before shiny blue patches became a common feature on the top of houses and office buildings, there was a long and rich history of how the sun’s heat and light energy became a much needed power source.
As far back as the 7th Century BC, people used a magnifying glass to concentrate the sun’s rays to make fire. And they also burnt annoying ants! By the 3rd century BC, the Greeks and the Romans were frequently using burning mirrors to light torches during religious ceremonies.
Around 212 BC Greek scientist Archimedes used a cunning device to deter the Romans from besieging Syracuse. He used the reflective properties of bronze shields to focus the sunlight on the approaching wooden ships out at sea. Within minutes, they were on fire! No wonder Archimedes is credited as the father of concentrated solar power.
Over time people built homes and designed their living spaces to draw in as much sunlight as possible. Justinian l, the Byzantine Roman Emperor, saw it as a basic right for people to get sun exposure. He initiated “sun rights” in a set of laws called the Justinian Code (AD 534) to ensure that there were sunrooms in houses and public buildings to give warmth and natural light.
An invention by Swiss scientist Horace de Saussure in 1767 saw him build the world’s first solar collector. This invention helped sustain Sir John Herschel, a scientist, astronomer and explorer, as he used solar power to cook food during his 1830s South African expedition.
The Stirling engine as we now know it was the work of a minister in 1816. Robert Stirling, when not at the Church of Scotland, built heat engines at home that were later used in the Dish/Stirling system, a solar-thermal electric technology.
From glass and mirrors and solar collectors, the invention of solar powered devices was made possible only when the next hurdle was tackled – conductivity.
The 19th century saw a series of progressions made in improving conductivity so that more light energy could produce electricity.
In 1839, while experimenting with an electrolytic cell made up of two metal electrodes placed in an electricity-conducting solution, French scientist Edmond Becquerel discovered that electricity-generation capability increased when exposed to light. This is the first recorded instance of the photo (light) voltaic (electric current) or PV effect.
The pursuit of light-induced conductivity picked up pace in the later half of the century. In 1873, Willoughby Smith discovered selenium’s photoconductivity. Three years later, William Grylls Adams and Richard Evans Day discovered that selenium produced electricity when exposed to light. This was an eye-opener – something solid could convert light into electricity without the additional property of heat or the aid of moving parts!
Less than a decade later, selenium research reached a turning point. American Charles Fritts used a thin layer of gold to coat the semiconductor selenium. This brought about 1% conversion efficiency – direct from light to power. While the materials used were too costly for mass production, Fritts can be credited as the first person to conceive the idea of electrical solar energy.
This triggered a wave of photosensitivity improvements into the early 21st century. New materials such as copper and cuprous oxide were introduced that led to William J. Bailley of Carnegie Steel Co. to invent a solar collector with copper coils and an insulated box in 1908. This design still remains today.
Enter silicon. In 1918, Polish Jan Czochralski found a way to grow single-crystal silicon which led to a flurry of scientific research and experimentation.
In 1954, Daryl Chapin from Bell Telephone Laboratories sought to find a way to get telephones to work in remote places – 50’s era batteries could not thrive long in hot and humid areas. His colleagues, Gerald Pearson and Calvin Fuller, were working on building a solid state rectifier (one that transforms AC to DC) with crystalline silicon. As that time, PV cells were made of selenium, which could produce only five watts per square metre, or a 0.5% conversion efficiency. Chapin wanted 6%!
Over time, the researchers introduced gallium into the crystal matrix, and coated that in hot lithium. While shining a light on this crystal, Pearson discovered that the light energy induced an electric current! Another Eureka moment – Fuller vaporized phosphorus onto the ensemble, allowing for the target 6% efficiency! They now got their phones to work in far away places.
This signalled a new era of material improvement for the everyday use of solar PV cells.
Post War in the mid-20th Century, researchers saw the need for industry growth and social improvements, hence research revolving around the sun took on greater importance.
In 1964, NASA launched the first Nimbus spacecraft, which was a 470-watt PV powered satellite. Just a year later, Peter Glaser conceived the idea of the solar power satellite station. Thanks to this new development in space and PV technology, we can explore the unknown, predict the weather and connect ever faster with any part of the world.
The 1970s saw the growth of solar powered applications for everyday use, especially in remote places. In 1972, a village school in Niger received a gift from the French – a neat educational television powered by a cadmium sulphide PV system.
The University of Delaware in 1973 built the world’s first residences, called Solar One, using PV and thermal hybrid systems. Today, you can find amorphous thin film solar cells on windows and vertical walls – these make it possible for even greater sunlight collection. Coupled with lead acid or lithium ion battery advancements, storage of energy for electrical conversion is becoming easier and more feasible for off-grid living compared to a decade ago.
In 2006, the sporty Tesla Roadster became a game changer in the electric car space. Founders Martin Eberhard and Marc Tarpenning experimented with jaw dropping designs and state-of-the-art parts that included heated seats, satellite navigation and the lithium-ion batteries. The quiet vehicle had an incredible acceleration of 0 to 97km/h in under 3.9 seconds and could travel as far as 320km on a single charge.
Solar PV has also become commonplace on the high seas with hybrid electric-motorised boats and yachts using the sun’s energy for cruising power. The largest yacht, according to the Guinness World Records in 2010 was the MS TURANOR PlanetSolar, measuring 31m long and covered by 537 square metres of 93 kW solar panels. It also made the fastest transatlantic crossing at 14 knots tops completely under solar power in under 27 days.
Solar farms have also replaced fossil fuel dependency in many parts of the world, reducing pollution and carbon emissions as homes and offices enjoy clean energy. Ghana and neighboring countries will receive up to 100MW ground-mounted solar farms and a further 50MW of rooftop projects through a 2015 partnership between Yingli Solar and renewable energy developer Namene Energy.
Portable solar gadgets are now getting funky. Fancy a solar bikini? New Yorker Andrew Schneider’s solar bikini allows the sunbather to charge a smartphone or media player while lying on the beach. The 2011 invention has 40 thin and flexible PV strips sewn together by a conductive thread, ending at a USB port.
Now if that doesn’t wow you, maybe this will. Beijing’s proposed electric “hover bus” will be partly powered by PV panels, transporting 1,200 people to their end destination by gliding over cars stuck in traffic.
Now that is surely an invention on the move! In the words of eco-explorer Raphael Domjan of PlanetSolar, “We must motivate engineers and scientists to develop innovative technologies and show that the impossible can become possible.”