Reducing Water Footprint In Electricity Production

Manoj Misra

Often we talk of fossil fuel (coal and gas) and nuclear power as the source of electricity where coal, gas, and uranium are used as fuel.

The question is fuel to what end, for these power plants currently produce the largest (70 percent) amount of electricity on earth?

The principle of both these sources of energy (together called ‘thermal’) is to generate enough ‘heat’ – by either burning the fuel (coal and gas) or initiating a nuclear fission reaction involving uranium (in nuclear power plants) – to convert water into ‘steam’ that in turn move the turbines to produce electricity. So water to produce steam is an essential ingredient in the thermal power industry.

These power plants also use water as a coolant and medium to dispose of fly-ash in the case of coal-based plants. They also release contaminated water at high temperatures after use.

Clearly, the water footprint of electricity production through these means is huge (in the US some 133 billion gallons of water per day was used by them in 2015) but most of the time the focus of planners and decision influencers including NGOs had been more on the risks involved with the use of coal and gas as fossil fuels or uranium for nuclear energy with problems associated with the disposal of nuclear waste or nuclear accident. It is not often that the water cost of electricity production is seen as a serious issue. This attitude must change.

Let us first look at a few practices and statistics.

Till not long ago water for electricity generation by thermal power plants was seen as a given. State governments keen to install thermal power plants offered liberal terms for water use by them and the industries with captive power plants used water liberally. Many such power plants were located close to dams or barrages on rivers (for example the Rajasthan atomic power plant at Rawatbhata is on river Chambal and the Narora nuclear plant is close to the barrage on river Ganga) and no questions were asked about the amount of water used or the quality of water released by them.

It is estimated that industries use around 10% of all freshwater consumed in the country and about 90% of all the water used by industries is by the thermal power sector.

In water terms, there are two kinds of thermal power plants. One where water is taken in, utilized, and released (once-through plants) and the other kind where water is used, recycled and reused with the ultimate aim of becoming zero liquid discharge. The majority of 269 thermal power plants in the country currently belong to the first category.

It was only in 2015 that for the first time the ministry of Environment, Forests and Climate Change (MoEFCC) set futuristic norms for water use by these power plants. It was envisaged that by the end of 2017 all power plants shall consume no more than 3.5 cubic meters (1 cubic m is 1000 liter) per hour per megawatt (MW) of power generated.

So as an example, a 300 MW power plant over 24 hrs (1 day) could use some 25200000 (2 crores 52 lakh) liter per day. Further MoEFCC specified that new plants (installed post 1 January 2017) were to limit their water use to 2.5 cubic m per hour per MW and to become zero liquid discharge.

Against the above according to a NITI Ayog report the actual water use by the thermal power sector (with cooling towers) is 5-7 cubic m per hour per MW. Clearly, there is a long way to go for the thermal power sector to become water-efficient and compliant with the norms.

With climate change making rapid inroads into different parts of the country and water security both for food production and household consumption taking precedence over the rest, making enough water available for the generation of power is going to be an uphill task, to say the least.

A 2018 report by the World Resources Institute (WRI) found that 90% of India’s thermal power plants use freshwater; 40% of them are located in high water stress regions and between 2013 and 2016, fourteen of India’s largest 20 thermal power plants experienced one or more shutdowns due to water shortage. This is yet another reason why renewables like solar and wind that are not water-dependent must take priority over other sources of power like the thermal.

This article was first published in The Dialogue as Can We Reduce Water Footprint of Electricity Production? on 17 May 2022.