Solar: the cell, the chain and the schemes

Prelims and MainsCurrent affairs on this: Solar energy

A solar cell is a wafer of silicon with a junction built into it: light knocks electrons loose, the junction pushes them one way, and a current flows, direct current that an inverter turns into the alternating current of the grid. Cells are soldered into a module, modules into an array, and a commercial module turns a little over a fifth of the sunlight on it into electricity, newer cell types a few points more and perovskite tandem cells more still in the laboratory. Because the sun sets, a solar plant delivers about a fifth of its rated capacity averaged over a year, which is why capacity and generation are different numbers. The chain runs polysilicon, ingot, wafer, cell, module, and China holds most of every link; India makes modules, is beginning to make cells, and has no polysilicon. The schemes are on their own subjects.

• The technologies: crystalline silicon in nearly all of the market, monocrystalline now standard, with cell designs named PERC, TOPCon and heterojunction rising in efficiency; thin film cadmium telluride as the main alternative; perovskite tandem cells past 30 per cent in the laboratory but not yet durable; concentrated solar power, which focuses sunlight to heat a fluid and can store heat for the evening, and which India built little of. Bifacial modules take light on both faces; trackers follow the sun.
• The numbers a question uses: the National Solar Mission of 2010 set 20 gigawatts by 2022 and was raised in 2015 to 100; the 2030 target is 500 gigawatts of non fossil capacity in all, with solar the largest share; the renewable capacity subject on the grid theme carries the installed figure. Bhadla in Rajasthan is the largest park, and the solar parks scheme of 2014 builds the land and the wires so that developers only bring modules.
• Making it at home: the Approved List of Models and Manufacturers, List I for modules and List II for cells, on which government supported projects must buy; the production linked incentive for high efficiency modules, ₹24,000 crore; basic customs duty of 40 per cent on modules and 25 per cent on cells since 2022; and a polysilicon scheme being drafted, on the manufacturing subject.
• Putting it on roofs, pumps and water: PM Surya Ghar, rooftop solar for a crore households with net metering, where the surplus runs the meter backwards; PM KUSUM, solar pumps and feeders for farmers; the Surya Sarovar scheme for floating solar on reservoirs; each on its own subject. Agrivoltaics grows a crop under raised panels; canal top solar shades the water it stands over.
• The world: the International Solar Alliance, launched by India and France at Paris in 2015, headquartered at Gurugram, a treaty body since 2017 with over a hundred members, the first international body based in India; and One Sun One World One Grid, proposed in 2018 and launched with the Green Grids Initiative at Glasgow in 2021, the idea that a grid spanning time zones always has the sun somewhere.

Mains: India's solar success is a procurement success and its solar weakness is a manufacturing one: auctions bought the world's cheapest power with the world's cheapest modules, most of them Chinese, and the schemes now paying for cells and polysilicon are the bill for that bargain.

Further reading: Solar Overview (MNRE)

See also: PM Surya Ghar: Muft Bijli Yojana · PM-KUSUM · Pradhan Mantri Surya Sarovar Yojana · Solar cell and module manufacturing · India's renewable capacity · Curtailment · How a battery works, and the chemistries in play · The grid: how power reaches a plug, who regulates it, and what renewables change