The Story of Solar Energy

We think of solar power as a relatively new field of study. But human beings have been harnessing the power of the sun for not just hundreds, but thousands of years.

As early as the 7th Century BC, humans were using sunlight to light fire using the material in magnifying glass. Ancient Egyptians used the power of the sun to heat their homes. Roman buildings were built such that they would trap the sun’s heat and store it during the day, and release the energy at night. Roman bathhouses were “sun rooms”, where they used massive windows to direct sunlight into one concentrated area.  

LEARNING TO CONVERT ENERGY TO MOTION

Like with most forms of energy, humans earlier didn’t know how to convert solar energy into motion. The conversion of energy to motion has taken a long time to develop. Wood was used as a heating and fuel source for homes and was the primary source of energy. It took time and deficiency of wood for mankind to adopt to using coal as a method to generate heat. Although coal was readily available, it took some time for us to learn to use coal to heat water to produce steam, converting heat into motion. 

USING HEAT ENERGY FOR MOBILITY

The first of these machines were steam-run water pumps used to pump out water from flooded mining tunnels. The steam would be generated by heating water using coal. Then came the invention of the steam engine. In 1825, a British engineer connected a steam engine to a train of mine wagons full of coal. The engine drew the wagons along an iron railway line about 20 km from the mine to the nearest harbour. This was the first ever steam-powered locomotive in history. In 1830, the first-ever commercial train ran between Manchester and Liverpool. But once this was discovered, it only took 20 years for the British to build thousands of kilo-meters of railway tracks in Britain and their colonies worldwide.

CONVERTING MASS TO ENERGY

Then came Einstein’s popular discovery (the equation e=mc^2) that any mass could be converted into energy. In mere 40 years since the discovery, nuclear bombs were dropped on Hiroshima and Nagasaki. We are clearly making scientific progress at a far greater pace than ever before. We should be headed towards a future where renewable sources of energy are the norm and petrol and coal are considered archaic sources as wood is currently.

PROGRESS IN SOLAR SCIENCE

Research on solar energy and the photo voltaic effect has only made progress in the recent few decades. If not for the ready availability of petroleum throughout the world, research in renewable energy would’ve been swifter. The good thing is, it is never too late. 

The photovoltaic effect was first observed by the French physicist Alexander Edmond Becquerel in 1839. At age 19, in his father's laboratory, he placed silver chloride in an acidic solution and illuminated while connected to platinum electrodes. During the experiment, Becquerel saw that a voltage had developed when light struck the electrode. The photovoltaic effect is also known the Becquerel Effect. 

In a paper published in 1905, Einstein postulated that light had an attribute that had not yet been recognised. Einstein said light contains packets of energy which he called light quanta (now called photons). He suggested that the amount of power that light quanta carry varies according to the wavelength of light (shorter the wavelength, higher the power). 

In April 1954, a slightly modified layer of silicon, called a "solar cell", that converted sunlight directly into electrical energy was unveiled by Bell Telephone Laboratories in Murray Hill, New Jersey. In the year 1956, the first solar modules were available commercially. The cost, however, was far from the reach of everyday people. At $300 for a one watt solar module, the expense was far beyond the common man’s means. Solar cells have become less expensive over time, and now is the best time to be adopting renewable sources of energy. 

GOING SUSTAINABLE WITH ENERGY

The world is heading towards a day where we will invariably run out of fossil fuels. We will have burned it all, but the story of humanity teaches us that we are always going to find new and better ways to generate energy. Only a tiny proportion of the sun’s energy reaches us, yet it amounts to 3,766,800 exa-joules of energy each year (an exajoule is a billion billion joules). In addition, we are surrounded by other enormous sources of energy, such as nuclear energy and gravitational energy. Gravitational energy, in the form of tides are used to generate electricity in tidal power plants. 

Solar energy can be utilised in many forms and solar cells convert solar energy into electrical energy. At SunPedalRide, we have a solar panel above our tuk-tuk and on a bright sunny day it adds approximately 30% to our energy requirements. Our experience on the highways of India have taught us that without a solar panel, we are just wasting the free energy thats available to us. It has definitely  given us a boost we need to reach us destination and still have enough range to give out test drives and for our local commute. 

MORE ON SOLAR CELLS

Solar cells, also known as photovoltaic cells are devices that convert solar energy to electrical energy through the photovoltaic effect

Photovoltaic effect is a process in which materials exposed to sunlight generates voltage and electric current. 

Photoelectric effect, which is closely related to the photovoltaic effect is the process in which light causes the material exposed to eject electrons from its outermost shell. 

Voltage - aka Voltage difference, is the potential difference between two points in space.  In simpler terms, Voltage is the pressure from an electrical circuit's power source that pushes charged electrons (current) through a conducting loop, enabling them to do work such as lighting a bulb. 

Solar Panels are arrays of solar cells aligned in a series connection. A solar panel has a protective casing made using butyryl plastic(the stuff used to make car windshields) or transparent silicon rubber and a backing made of polyester film such as mylar. Conductive metal contacts are places to carry the charge. 

Solar cells are made using semi-conductor materials, typically Silica (an oxide of silicon) most commonly found in sand. Silicon is a semiconductor. It has 4 electrons in its out outer-shell and it forms a stable crystal structure. 

When Boron (which has 3 electrons in its outer shell) is added to silicon, it creates a hole (positive charge) in the structure. This creates a p-type semiconductor (positive-type) since there are positively charged holes running around inside the silicon-boron structure.  

If Phosphorous (which has 5 outer electrons) is added to silicon, it bonds tightly in with the silicon structure but leaves an electron to roam free thus leaving it with a negative charge. This is called a n-type (negative-type) semiconductor. 

When a p-type semiconductor is laid on a n-type semiconductor, some of the holes in the p-type bonds with the electrons in the n-type and create an electric field which repels the electrons in the n-type and holes in the p-type to cross over. This electric field is called as a n-p bridge. 

When sunlight falls on this p-type, n-type semiconductor, photons provide the energy required for the n-p bridge to break and electrons and holes are set free. If we connect both the layers with a conductive circuit, the electrons will be forced from the n-type and flow through the circuit to the p-side thus providing us with electric current. 

CONCLUSION

Renewable sources are here to stay. 

Solar cells currently have an average efficiency of about 15-20% and research on them continues.

However, the public adoption of the technology has stalled because of the high cost of manufacturing the cells and the consumer’s inhibition to invest a large amount of money. 

Government subsidies, public outreach programs and awareness campaigns like ours are necessary to get people moving and investing in solar tech. The initial high cost of solar cells and panels are offset when we realise that the lifetime of a panel is approximately 25 years, and they almost always pay back every penny we invest in them.

Ruthvik Arya