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Adequate Water for Thermal Power Plants could be a problem, Shri R V Shahi, Former Secretary, Ministry of Power

This summer we have often come across the news that electricity generation at our hydro electric power stations is likely to be significantly less than last year, during which itself the generation was lower than the previous year, because of low water levels in reservoirs in view of inadequate monsoon. In a cyclic way every 4 to 5 years we do face water shortage of varying degrees in different hydroelectric stations thereby leading to reduced electricity generation. Water is an issue indeed for hydroelectric projects. In this Article, however, what we are going to discuss is not about the inadequacy of water for hydroelectric plants but for likely water shortage for thermal power plants.

As we know, thermal power plants also do require large quantities of water. Water in general is becoming an issue in many parts of the world, but in India availability of water has already started posing serious problems. There are hardly any large towns and cities including metros which do not suffer shortages of water supply. Drinking water and water for irrigation, not only when we face drought situation but also in other periods, are becoming scarce. Every summer we hear of water riots and Municipal Authorities have to organize emergency management systems to tackle the situation. Thermal power plants are going to compound this problem. We have the following challenges to address in coming decades in so far as the issue of water in relation to thermal power plants is concerned :

  1. Inspite of our best intentions and efforts, power plants based on coal will continue to increase in terms of capacity requiring larger amount of water. When we are going to scale-up, during every Fiver Year Plan, the capacity addition programme of the order of 70,000 to 100,000 MW, as compared to less than 25,000 MW in the past, coal based capacity is going to occupy the largest share.

  2. At present, coal based plants account for about 90,000 MW of the 150,000 MW capacity. When by 2032, the total capacity would rise to 800 GW, it would be inescapable to have coal based plant less than 400 GW. This means requirement of more coal and of more water, almost five times of the present volume.

  3. Though the planning stipulates locations of a number of Load Centre power plants, including a chain of coastal power plants, the largest proportion of power plants within the coal group would come from the pithead locations. Since coal reserves in India are located in select pockets such as Jharkhand, Chhatisgarh, Madhya Pradesh, Orissa etc. the pressure of large capacity additions in these States would be much more. Obviously, the water availability for the requirements in the nearby area will be under tremendous pressure and in many cases such an availability may not exist. For example, in Chhatisgarh alone almost 50,000 MW of new capacity is proposed to be set up by various developers. Though technically water linkage has been assured by the State Government, there are also questions and concerns whether all these plants will have adequate water.

  4. In the States like Gujarat and Rajasthan there have been instances of serious problems faced even by the existing power plants due to scarcity of water. As a result, the plants had to face partial or full dislocation of power generation.

Though providing energy and electricity is becoming an important requirement, the need of water by these power plants cannot obviously be placed at a higher priority than for the purposes of drinking and irrigation. If we integrate, at a macro level, the water requirement for different purposes, which we need to for a proper planning, we will find that the country will have insufficient water for any of these important segments of consumption. We need to economise in each of the areas - Municipal supplies, agriculture and industry, particularly power sector. The issue is not just one of conserving for an efficient use. Such a requirement is absolute in itself. Because, even if we have sufficient quantity of a commodity, efficiency in utilization and consumption has to be an important consideration, because wasteful consumption would not only be not cost effective but would be unsustainable. This is true for all the commodities. In case of water, while that consideration is equally valid, the point that is being made is that water is just not going to be available for the type of expansion of various economic, social and industrial activities that we are embarking upon. Thermal power plants are one of the large consumers of water. It is, therefore, essential that all possible steps are taken to minimize the need of water in these power plants. This approach would need to be viewed from two angles - (a) keeping the technology as it exists in operation, minimizing and eliminating the wasteful consumption, and (b) evolving new technologies which minimize and, if possible, eliminate the need for water. It is here where we have to focus. In the last week of May, I had an occasion to listen to a Presentation made by GEA - EGI of Hungary and Energo (India) in a well attended meeting organized by CEA. The Presentation covered the subject of "Reduction in Consumptive Water in Thermal Power Plants." The salient features of the presentation are outlined below:

  • Larger portion of earth has water, yet, it is estimated that not more than 2.5% of the water in the world is fresh water, and only a small fraction (0.007%) of even this is accessible for direct human usage.

  • Wet Condenser Cooling for a typical 1,000 MW thermal power plant requires approximately 3,000 Cubic Meter per hours which is equal to the water required by almost one million rural population.

  • According to Central Pollution Control Board (CPCB), among the industrial users, power sector consumes about 88% of water. The following Table presents the annual water consumption in different industry sectors.

Water Use in Indian Industry

Industrial Sector

Annual Wastewater Water Discharge (Million Cubic Meters) Annual Water Consumption (Million Cubic Meters) Percentage of water consumed in industry

Thermal Power Plants

27000.9 35157.4 87.87

Engineering

1551.3 2019.9 5.05

Pulp & Paper

695.7 905.8 2.26

Textiles

637.3 829.8 2.07

Steel

396.8 516.6 1.29

Sugar

149.7 194.9 0.49

Fertilizer

56.4 73.5 0.18

Others

241.3 314.2 0.78

Total

30729.2 40012.0 100.0

Source : CPCB/CSE CII/FICCI 6th Feb, 2007

  • Though there are a number of coal based power plants as also gas based power plants in the world which use Dry Cooling System, and in some cases Hybrid (combination of wet and dry) system, in India we have been used to only Wet Cooling System.

  • Situations in which Dry Cooling System would be relevant include (a) when water is not available at all, (b) scarce water is available, (c) water is available but the distance is so long that the cost becomes excessive, (d) use of available water is unfavourable, (e) the plant is in densely populated area, (f) there are serious environmental constraints and social issues.

  • The main features of the Dry Cooling System include (a) it supports power cycle with greater operational flexibility, (b) power cycle water chemistry is made easier and comfortable, (c) it improves power cycle reliability and availability and reduces need for maintenance, (d) it offers greener and cheaper opportunity for flue gas exhaust, and (f) it is cost efficient taking into account the long term cost of making adequate water available in a conventional Wet Cooling System.

  • A properly designed Dry Cooling System would also eliminate the need for a separate chimney. The functions of chimney are adequately performed by the Cooling Tower, even though the height of the tower would be shorter.

The Presentation was followed by detailed interactions during which the experts on the subject asked for clarifications and raised their queries. Some of the points which need further examination including the following:

  1. In the Dry Cooling System, as also in the Hybrid System, there is a marginal loss in the generation of power as compared to the conventional Wet Cooling System. However, it was clarified that if we take the totality of the issues into account, including likely partial availability of water, increasing cost of water and other relevant factors concerning environment, the marginal loss in generation will be more than offset by the overall benefits. This point will need to be examined in detail. Prima facie it appears that the Dry or Hybrid System may be relevant to the Indian power industry because in the years to come neither the cost of water would continue to be as low as it has been so far nor would there be enough water for all the power plants that we wish to build in the future.

  2. At present, the Ministry of Environment has prescribed specific heights of chimneys to take care of wider dispersal of emissions to dilute the effect of concentration of these emissions. If the cooling tower under the new dispensation has also to handle the functions of chimney, with reduced heights, we will need to justify that the purpose of chimney in no way is getting diluted. This would require the necessary change in the norms set up by the Ministry of Environment. This is a valid concern. However, the justifications of the new arrangement should be able to be put across with the Environmental Authorities for the required change in the Guideline.

  3. As mentioned earlier, Dry/Hybrid Cooling Systems would entail marginal loss in power generation. This means that for the same amount of coal the electricity generation would be somewhat less. Does it go counter to the concerns about carbon emissions? On the face of it, CO2 emissions per unit of electricity may appear higher but overall environmental concerns, when we start evaluating a criticality created out of water consumption, may provide a positive answer in favour of Dry/Hybrid Cooling Systems. There is a need to examine the need for conserving water, as there is a greater need for examining the implications of excessive consumption of water. Higher CO2 emission is being rightly projected. Higher water consumption, for the same reason of environment, needs also to be projected. The equation of CO2 emissions and water consumption needs to be properly structured and worked out.

  4. If this technology is to be deployed - there seems to be evidence in favour of doing so - the Electricity Regulatory Authorities may have to be appropriately brought on board. There would be capital cost implications in the short run and there would be marginal loss in generation. These will need to be evaluated and compared with the concerns arising out of water usage.

It is gratifying that Central Electricity Authority has set up a Team to examine all the issues concerning water consumption in thermal and nuclear power plants. It is now widely recognized that the business - as - usual approach in respect of water consumption in a conventional way in our power plants would be difficult to continue in a sustainable manner. This is true not only for the existing power plants, but more true for our expansions. We need to revisit the technologies for new plants as well as think of right retrofitting even in the old plants, so that the ambitious expansions of Indian power industry, which will need to rely predominantly on coal plants and nuclear plants, are realized in the time frame that has been set out and not get adversely affected on account of unavailability of water.