It is imperative to improve water efficiency in India’s coal-fired thermal power plants
The extraction of huge amounts of water by coal-fired thermal power plants may affect the short-term availability of water in India’s river basins, a recent study has pointed out.
The study, titled Vulnerability assessment of thermal power plants in India under water stress conditions, has been co-authored by Anshuman Swain of the Central Electricity Authority under the Ministry of Power (MoP). The document, published in May 2023 in Science Direct, looked at the impact of water consumption by coal-fired thermal power plants on India’s growing water crisis.
The major power grids in India — eastern, western, northern and southern — are dependent on the 14 river basins, with more plants distributed in the Indus, Ganga, Mahanadi, and Godavari basins. The catchments in India are under ‘high water stress’ due to the post-2010 geographical shift in the construction of new coal-fired power plants favouring northern and eastern river basins.
The study estimated the vulnerability index of the power plants based on the average generation ratio (AGR) and water trend in the region. AGR is the ratio of average annual production (power) to maximum power generation from a power plant in ideal conditions.
Some 64 power plants with AGR below 0.5 were selected to understand the vulnerability of these plants to the depleting water trends in the respective river basins.
The western power grid has the highest installed capacity but most of these plants are located in regions of ‘low water potential’ in Maharashtra and Gujarat. The grid has the highest number of coal-power plants that are vulnerable to surface water resource availability.
About 19.5 per cent of the installed capacity of the power plants in the northern grid, drained by the Indus and the Ganga, is vulnerable. Giral Lignite Thermal Power Plant of 250-megawatt capacity is the region’s only plant that is extremely vulnerable to surface water availability. Any new plants installed in Rajasthan, Punjab and Haryana grids in the northern region are bound to face water stress as these states are located in water-scarce regions.
The southern power grid is mostly in a comparatively low vulnerability index. The distribution of power plants in the southern basin is compatible with freshwater availability. There are fewer plants in northern Karnataka and western Tamil Nadu, with annual water availability of less than 200 millimetres. The eastern power grid has 12 power plants that are highly vulnerable to freshwater availability in the region.
Impending disaster
Coal thermal power plants account for about 70 per cent of the industrial water withdrawal in India, the Delhi-based non-profit Centre for Science and Environment (CSE) found in 2021. The non-profit also revealed that 48 per cent of the existing coal-power fleet was located in water-scarce regions.
Though the new study projects a comparatively lower capacity of 30 per cent that is established in regions ‘showing negative trends of freshwater availability’, it is imperative that we invest in solutions to reduce water consumption by coal power plants.
At this pace, such massive water withdrawal for electricity generation will not only have repercussions on the watersheds across India but will ultimately interrupt the functioning of the power plant during the lean periods.
In 2015, the Ministry of Environment, Forest and Climate Change (MoEFCC) introduced a water consumption limit on coal power plants with stricter norms for plants commissioned post-2016.
However, in June 2018, the norms pertaining to water consumption were relaxed for plants installed after January 1, 2017. The specific water consumption for these plants was increased to 3 cubic metres per megawatt hour (m3/MWh) from 2.5 m3/MWh. The amendment also revoked the applicability of these norms on power plants using seawater.
Even India’s most efficient coal power plant consumes twice the amount of water than the world’s average.
To date, no information concerning power plants’ compliance with the water consumption norms is available in the public domain. The paper also recognises the unavailability of data regarding actual water withdrawal and actual water consumption at the plant level as one of its limitations.
It is surprising to note that the plant-level data on water consumption could not be procured despite an MoP official being one of the co-authors. Additionally, it is mandatory for the power plants to submit such information to the ministry quarterly.
In its 2021 study, CSE gathered water consumption data from coal power plans and found that “excluding seawater-based plants from the surveyed capacity, almost 50 per cent of the plants did not comply with the norms”.
The CSE 2021 study also noted that most ‘once-through cooling’ (OTC) plants had not upgraded their cooling towers as mandated in the 2015 notification. The pollution control board did not conduct any on-ground inspections to ensure zero-liquid discharge from the capacity commissioned post-2016, it added.
Way forward
Cooling tower is responsible for the consumption of 80 per cent of the input water for energy generation in a coal-fired thermal power plant. Addressing water consumption by the cooling towers can significantly reduce the power plant’s overall consumption. The air-cooled condenser is expensive but can reduce the water intensity to 0.45-0.65 m3/MWh.
Power generator and distributor National Thermal Power Corporation recently commissioned an air-cooled condenser that is based on a ‘dry cooling system’ in its 2GW coal power plant in Jharkhand.
Apart from technical upgradation, a more spatial distribution, sensitive to freshwater availability in the site proposed for coal power plants, can help prevent the crisis. Till then, we need to prioritise the implementation of norms in water-scarce regions and ensure zero-liquid discharge by the new plants to limit water consumption.
Some 22 billion cubic metres of freshwater are consumed by industries annually. Of which, 70 per cent goes for electricity generation by coal-based thermal power plants, said Nivit Kumar Yadav, programme director, CSE.
He insists that the government needs to take cognisance of this fact and act accordingly. Despite several other studies establishing the negative impact of coal-fired thermal power plants on freshwater availability and, eventually, water scarcity affecting plant operation, Yadav is hopeful that the new study will finally bring home the point because of the direct involvement of the deputy director, Central Electricity Authority.