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A green role for dirty coal

11 Sep 2019

In the last couple of years, a quiet revolution called ‘flexibilisation of coal’ has been gaining ground, whereby coal plants supply power only when required, to fill the gaps left by wind and solar, says M Ramesh 
A little more than half of India’s 356 GW of installed power capacity, and three-quarters of electricity generation of 1.3 trillion units, are based on India’s major energy resource — coal. The problem is, we don’t want it.
The problems with water-guzzling, globe-warming, polluting coal plants are, by now, too well-documented to merit detailed discussion. Tomes of data and literature declare coal to be an enemy. Some data points are scary. For example, a study has discovered that 37 GW of India’s thirsty coal-fired plants lie in extreme drought areas.
However, India is now forced to sleep with the enemy, having “substantially over-built” coal power plants (in the words of a report on “Risks Growing for India’s Coal Sector”, by the Institute of Energy Efficiency and Financial Analysis, a US-based energy research think-tank.)
Alongside, despite the headwinds that India’s wind and solar energy sectors have been facing in recent years, the renewable energy story is expected to be a happy one. Even if the targets —175 GW by 2022, 275 GW by 2027 and 500 GW by 2030 — are not met, the country will end with respectable numbers. And, renewable energy is cheaper than coal, substantially so when compared with newer coal plants — around ₹2.8 a kWhr, compared with, for example, ₹4.5 a kWhr for the 1,980 MW Ghatampur plant in UP.
The issue is showing up in red colour. Last year, the power secretary said that a fifth of India’s coal power capacity couldn’t earn enough to pay interest to banks; Credit Suisse estimated the value of such ‘stressed assets’ at $35 billion. So now, the burning — smoking — question is, what do we do with the coal plants we are stuck with?
For an answer, India has turned to — what else? — renewable energy. Ironically, renewable energy’s problem is coal’s solution. Renewable energy’s negative is its fickle nature. Clean it may be but it is intermittent, unpredictable. Coal (as also gas and nuclear) is steady. Till a few years ago, before renewable energy got mainstreamed, renewables used to be a chip-in-and-help player, while coal was the king. Now the roles are getting reversed. The emerging normal is to use coal-based power to fill the gaps left by wind and solar. Problem is, coal is a slow-starter — it takes time to get a coal plant up and running, and equally, to shut it down.
But in recent years, engineers and economists have found a way to get around this problem. In doing so, they have added a new word to the English dictionary — ‘flexibilisation’.
In the last couple of years, a quiet revolution called ‘flexibilisation of coal’ has been going on, and is now gaining ground. ‘Flexibilisation of coal’ refers to the process of enabling coal plants to supply electricity only when(ever) asked for.
There are two parts to it — technical and economic. On the technical side, the Central Electricity Regulatory Commission (CERC) has assessed that it should be possible for a coal plant to operate at 55 per cent of its capacity with only deft management; to go down further, some retrofits might be required. VGB Powertech, an international technical association, which has studied NTPC’s Dadri and Simhadri plants, says that “no investment is required for 50-55 per cent minimum load operation and it can be achieved with modifications in operational practices alone”.
In a paper on “Flexibilisation of Conventional Power Plants — The Indian Experience”, presented at the ‘2nd International Grid Integration Conference’ held in New Delhi last week, the author, AK Sinha, says that to go further down to 40 per cent can be done “with minimum retrofits”. At NTPC’s Dadri Unit 6, just by retrofitting (a condenser throttle), the unit’s “fast primary response has been proven beyond doubt”.
As for the economic part of it, it is just a question of compensating the coal plants for asking them to shut down and stand by, for which the CERC has come up with a formula, applicable for central coal power units. For States, it is left to the respective state electricity regulator. The burden of compensation will be borne by the discoms.
Buying coal’s silence works out cheaper. Sinha’s paper details out tariff compensations in various scenarios, the costliest of which is asking an efficient, 660 MW supercritical plant to ramp down to 30 per cent of its nominal capacity — the tariff in this case works out to 40.8 paise. Buying wind power at, say, ₹2.84 paise a kWhr is cheaper even after a 40.8 paise compensation, than coal power at ₹4.50. Much cheaper, even before counting in social costs such as pollution and water.
According to Prof S K Soonee, an expert who is today advisor to the government-owned Power System Operation Corporation (POSOCO), a coal power plant can ramp up or down by 1 percentage point of its rated capacity in one minute.
Now flexibilisation is moving from the pilot stage to implementation. Sinha estimates that 82 GW, across 302 units of India’s coal power plants “can be made available”, but Prof Soonee has told BusinessLine that a lot more is possible.
To flexibilise 82 GW of capacity you’d have to spend about ₹14,000 crore, just once. Of course, playing see-saw with a power plant, asking it to produce more or pipe down as ordered, will mean more wear and tear. How much, depends on the specifics. A US consulting company, Intertek, which studied NTPC’s Ramagundam and Jhajjar plants, estimated the value of wear and tear at ₹28.7 lakh/MW for a 210 MW plant, and ₹19.22 lakh/MW for a 500MW plant, at 2016-17 prices.
 
Changing roles
 
The biggest obstacle to flexibilisation of coal, as various speakers at the Delhi conference pointed out, is neither technical nor financial, but one of culture. A coal power plant operator, used to having a horde of eager electricity purchasers waiting at his doorstep, is bound to find it repugnant to be asked to play second fiddle to renewable energy.
But that is the reality — and the future — of coal. The coal power plants that will be built in future will have to be both highly efficient, clean and flexible. A typical plant is a 1,000 MW ultra supercritical coal power plant in Karlsruhe, Germany, a country in which renewable energy accounts for 54.5 per cent of the total installed capacity. (India aims to reach 40 per cent, including hydro, in 2030.) This plant operates at (very high) efficiency of 47.5 per cent and pollutes and emits very less. Yet, it derives life-assurance from its ability to operate at 20 per cent of its nominal capacity. If a coal power plant operator feels slighted at being asked to be a stand-by, he will have to swallow his hurt and play along. Even the most efficient of coal units can only be renewable energy’s deputy, not boss.
 
Source : https://www.thehindubusinessline.com