Solar energy has been touted as the answer to rising energy woes around the world for what seems like ages now. But it is only recently that we have seen a significant effort from various countries by harnessing the power of our local star. And it’s about time because life on our planet is itself powered by the sun. The food chain, that we are so proud of being on the top of, exists due to the sunlight harnessed by chlorophyll in plants. In fact, practically everything around you – ranging from the fossil fuel guzzling machines to essential natural phenomenon like the water cycle – happens because of the sun’s energy. And fortunately, it isn’t running out or falling short anytime soon.
According to the United Nations Development Programme estimates, the total annual solar potential of earth ranges between 1,575–49,837 exajoules (EJ), where even the lower estimate is more than twice the annual consumption of the planet – around 500 exajoules. Interestingly, that is just 0.0000013th of the total energy produced by the Sun each second. To be honest, that does not include the 3000 exajoules that plants consume by photosynthesis annually. Sadly, we hardly use any of this for generating electricity, yet.
Unlike what some world leaders would have you believe, our own country is also significantly invested in the future of solar energy. The Kurnool Ultra Mega Solar Park and the Kamuthi Solar Project are two of the world’s largest solar power projects with a combined capacity of more than 1500MW. In fact, India and China combined have the five largest solar projects currently in the world. Although, getting here wasn’t easy. Solar energy, or rather the interest in using it as a direct source of power, reportedly go way back to the 7th century BC. But actual literary evidence of it being used comes much later.
In second century BC, Greek scientist Archimedes reportedly used giant reflective bronze shields to focus sunlight onto incoming Roman ships, in order to set them ablaze. While no concrete evidence of this feat exists, the Greek navy repeated this experiment in 1973 and were successfully able to set a wooden boat ablaze at a distance of 50 metres. But even before that, people have been using reflected sunlight to illuminate corridors and doorways, especially in Egyptian tombs. This also enabled them to trap the heat from the sunlight for lower daytime and higher evening temperatures.
Apart from this, energy concentrated by reflecting sunlight was also associated with a religious significance, mostly because most civilisations considered the sun as a religious entity. Eventually, the benefits were pretty evident – so much so, that the Romans mandated a sun room in every house by law before 600 AD in the Justinian code.
Taking energy from the heat of sunlight was later applied to more extensive concepts like the solar oven. Swiss inventor Horace de Saussure made the first Solar Collector in 1767. The design consisted of an insulated box with a glass top and a couple of smaller boxes inside. In the sun, the internal boxes reached temperatures around 100 degrees Celsius quite easily. This design was later improved in the 1800s by Sir John Herschel by introducing a black inner-lining and sand into the design. While work in this area continued until the first world war, with innovations like the parabolic trough, it was the advent of photovoltaic cells that changed solar energy forever.
The exact invention of the solar panel is under debate because of the number of iterative contributions it took for a modern practical solar design to come around. Some associate the invention to French physicist Edmond Becquerel due to his discovery of the photovoltaic effect in 1839, which he explained as “the production of an electric current when two plates of platinum or gold immersed in an acid, neutral, or alkaline solution are exposed in an uneven way to solar radiation.”
It was the discovery of photoelectric effect in selenium by William Grylls Adams and his student Richard Evans Day that kickstarted the modern concept of a solar cell. Within the next decade, in 1883, Charles Fritts actually made the first solar cells from selenium wafers. This led to the credit for the invention of the solar cell majorly going to Fritts over time. Modern solar cells, however, are made of silicon, not selenium. The silicon solar cell was developed by Daryl Chapin, Calvin Fuller, and Gerald Pearson at Bell Labs in 1954. This was the first time photovoltaic cells were able to produce enough electricity to reasonably power small electronic devices. The New York Times was perhaps the most accurate in summing up the public sentiment around this discovery by calling it “the beginning of a new era, leading eventually to the realisation of harnessing the almost limitless energy of the sun for the uses of civilisation.”
But a major restriction in its initial days was the cost. In 1956, the commercially available solar cells would cost around $300 per watt. In spite of this, certain novelty items like toys and radios were beginning to include solar cells into their builds. In fact, another area where solar saw rising usage was satellites. The Vanguard 1, launched in 1958, was the first satellite to use solar power – it contained a small one-watt array to power its radios. Due to the ample availability of direct sunlight in space, this implementation picked up and later that year, the Vanguard 2, The Explorer 3 and Sputnik-3, all went to space with solar arrays on board. By 1964, NASA had launched Nimbus, a satellite powered entirely by a 470-watt solar array, into a sun-synchronous orbit to make most of the solar power available in space. Encouraged by the success of these launches, NASA launched an Orbiting Astronomical Observatory, powered by a one-kilowatt array, in 1966.
If you think that Tesla (The Elon Musk-led automobile, power and solar company) was the first to implement the concept of a solar roof, you would be wrong. Although they are one of the companies that have made the idea commercially viable as a product, the University of Delaware had incorporated this idea into the design of their “Solar One” solar building in 1973. The building ran on a hybrid of solar-thermal and solar-photoelectric power. Even with these developments, solar energy was little more than an experiment in the labs that was reserved for advanced implementations like the satellite. It was the oil and energy crisis in the 1970s that woke the world up to the need for an alternate, renewable energy source and solar energy was the one readily available. Gradually, focus shifted towards increasing the efficiency of generating solar energy.
It wasn’t until 1985 that an efficiency of 20% was achieved. M. A. Green, A. W. Blakers, S. R. Wenham, S. Narayanan and M. R. Willison formed the team that demonstrated the achievement of 20% efficiency under terrestrial conditions. The next time this was improved upon was in 1999 by the National Renewable Energy Laboratory in collaboration with SpectroLab Inc. by achieving an efficiency of 33.3%, which was again surpassed in 2016. Researchers from the University of South Wales once again improved upon solar cell efficiency by achieving a conversion rate of 34.5%.
|DID YOU KNOW|
|The Solar Orbiter 2 is the most powerful solar powered aircraft out there – it has even circumnavigated the globe and registered the first zero-emissions flight to do so!|
Today, the world is interested in solar power like never before. Companies like SolarCity (now a part of Tesla) have brought solar power into the hands of people around the world. Offering products like the solar roof, electric vehicle chargers, battery packs and commercial solar installation services, companies like these have played a huge role into bringing the cost of solar power down to the nominal $0.50 (anywhere between Rs. 30 – 50 per watt in India, depending on the size and efficiency of your solar setup) that it costs today.
We might be looking at a time where solar power supersedes other power sources, especially non-renewable energy. Going by the current support behind it, both from the government and the industry, that time might be sooner than later.
This article was first published in the August 2017 issue of Digit magazine. To read Digit’s articles first, subscribe here or download the Digit app for Android and iOS. You could also buy Digit’s previous issues here.