There was a peculiar Advertisement about an energy drink some time ago on our television sets. The sun, with its wicked eyes, drains energy with a straw from a school boy playing cricket. An inverse of this animated advertisement: the human civilization sucking energy from the sun’s rays, is what is being seen as the solution to sustain mankind. While we were looking into fossil fuels in previous issue of this series, it’s time to explore solar energy now!
Cheap, clean power is the absolute necessity for the growth of developing nations. That’s what solar energy is here to deliver. What’s more inspiring is that most of the developing nations like India, China, and many African nations are all blessed to be between the Tropic of Cancer and the Tropic of Capricorn where the sunlight period is more generous and intense. The countries in this belt are termed as Sunshine countries by the International Solar Alliance which is an alliance of more than 121 countries which was first proposed by Indian Prime Minister Modi. India’s plan of 175 GW (cumulative installed capacity – 330 GW) renewable energy, of which 100 GW from solar is a testament to the commitment of our nation towards COP 21.
But let’s hold the horses. Can Solar energy be the silver bullet to the energy and environmental crises the world is facing? The experts argue that we can’t be over reliant on solar energy. Let us look into the constraints, the number one being land availability. It will be challenging to procure landmass to develop large-scale photo-voltaic solar power plants. A typical 1 MW solar power plant needs 5-6 acres. Therefore, it’s going to be an arduous task of site identification to house tens and hundreds of MW capacity solar power plants. Well, is it such a huge task? We can of course utilise all of the Thar desert, Sahara desert that lay barren receiving abundant sunlight and bid adieu to climate change, one may argue. But there is more to it than meets the eye!
Solar photo-voltaic technology banks on the energy of the photon from the sun’s rays for the excitation of electrons and not the temperature or thermal energy of the rays.
Solar photo-voltaic technology banks on the energy of the photon from the sun’s rays for the excitation of electrons ( read: current flow) and not the temperature or thermal energy of the rays. Actually, the efficiency of solar cells decrease with increase in temperature! Therefore, it’s not viable to erect solar panels in hot areas. Further, dust cover over panels is also a worrisome hindrance, which reduce the already low ( 20-22%) efficiency. At this juncture, we have to appreciate the then Gujarat Chief Minister Modi’s initiative of canal top Solar PV installation. It serves the three purposes of reducing the heat load on solar panels, a cover for reducing evaporation losses from running water bodies and the third purpose occupying less amount of land! It is indeed a very laudable initiative.
The second constraint in solar PV is its undulating nature. Solar insolation is not uniform and they vary throughout the day. As the source is variable, it is difficult to synchronise with the grid. One can’t expect 100 MW daily. It is a huge shortcoming in colder countries. Solar energy can contribute 100 MW on a sunny day when the demand is low but it’s not possible to match our demand in the peak time in a cloudy day. Solar energy can’t displace Thermal and nuclear power plants as they supply the base load power. Finally, the economic constraint. We are regularly seeing news of solar PV power hitting a new low in each auction. There is a fear that it may not be cost competitive to deliver power at such a low cost. Many companies which have won bids for very low solar tariffs are looking to the government and banks to rescue them financially now. Needless to mention, it adds to the already burgeoning Non Performing Assets (NPA), a euphemism for defaulters. Now, the government has levied a tax on Chinese solar panel imports to protect the interests of local manufacturers. It is a good move but solar power can see a slight increase in price hereafter.
Technology has also ventured into tapping the solar thermal energy. Innumerable applications like solar water heating, solar cooking, passive ventilation systems are all being successfully used. In fact, the Tirumala Tirupati Devasthanam hosts the world’s largest solar steam cooking system which can cater to the hungry mouths of 30,000 people a day. That is some record to hold! Solar thermal power production is also being developed. Just like burning a paper with lens, large reflective concave mirrors are used to concentrate solar rays to a tower, where a molten salt is used to absorb all the heat and reach temperatures of around 500 degree C. This salt transfers the heat to water which is used to run the turbine to derive power. This is more a stable approach where it is possible to retain the heat and still produce power even in evenings until the temperature of molten salts reduce appreciably. A power plant in Australia has been proposed as of now.
Thus, instead of looking to host large power plants, there should be a push for more rooftop installations in institutions, government and private buildings. The Kochi International Airport, the solar powered plane – Solar Impulse aircraft etc showcase the future use of solar energy. Innovative measures like covering wastewater treatment bodies, canals with solar panels will be a huge bonus. Now the onus is on offshore solar PV plants which float in the oceans. If this can be achieved, then there can be no question of real estate! Government should fund,experiment and research these kind of stuff a lot!
On the whole, it’s advantage India for setting renewable energy target and achieving them comfortably. We’ll draw a conclusion to solar energy with an old adage – “Make hay while the sun shines”. The future looks bright…
The search for sustainable energy will continue in the upcoming months…
(This article was originally published as a part of series ‘SUSTAINABLE ENERGY- FOR INDIA’S ENERGY SECURITY’ in ‘The Agraria’ e-Magazine. You can Subscribe it here)