The water-energy nexus

Posted: August 13, 2024

Many municipalities put 30–40% of their energy use into processing drinking water and wastewater. Globally, the water sector used almost as much energy as the country of Australia in 2014, according to a 2016 report from the International Energy Agency (IEA). Meanwhile, the energy sector consumes 10% of all the water we extract globally. Because they are so interdependent, water and energy utilities are going to have to start sharing both resources and data with one another to cope with climate change.

Energy for water

The water sector uses electricity to extract water, distribute it and treat wastewater. It also uses thermal energy to pump groundwater for agriculture and for desalination. By 2040, the global water sector will have doubled the amount of energy it uses. 

Most of that increase will come from desalination in the Middle East, where fresh water is scarce, but energy is plentiful. Oman, for example, doesn’t have any year-round rivers to quench the thirst of its growing population, which has doubled in the last 25 years. Instead, some 60 desalination plants dot its coast, some even floating off shore.

But, desalination is particularly energy-intensive. Even though it contributes less than 1% to the global water supply, it’s responsible for nearly a quarter of the water sector’s energy footprint. In 15 years, it will be contributing 4% of the global water supply, but be responsible for 60% of its energy footprint.

Water for energy

Different energy technologies require vastly different amounts of water. Obviously, hydropower requires great quantities of water. Zambia relies on hydropower as its main energy source. But, severe and frequent droughts caused by climate change have caused blackouts and required Zambia to ration electricity in recent years.

Thermal power generation—from fossil and nuclear fuel—also requires large quantities of water for cooling. Its capacity has also been constrained recently by water scarcity. Ninety percent of India’s thermal power generation relies on fresh water for cooling—and as a result, the country lost 14 terawatt-hours (TWh) of power generation in 2016 due to water shortages—about half the annual energy consumption of Cyprus.

Many renewable energy sources, such as wind and solar photovoltaics, require very little water. But, other low-carbon energy technologies also consume significant water, namely biofuels, concentrated solar power and carbon capture technology.

Some energy generation merely withdraws water—that is, it extracts it from its source, uses it, and then releases it so it can return to the source, Others don’t merely withdraw the water—they consume it. That is, they use it such that it evaporates, incorporates into biomass or becomes contaminated so that it cannot easily return to its source for re-use. 

While low-carbon energy technologies will likely reduce water withdrawals by 20%, they will nevertheless increase water consumption by 50%. With low-carbon energy generation consuming more water, it may have less and less available to sustain energy generation over the long term.

Data-sharing solutions

The world needs both water and energy for nearly every activity—so simply reducing our use of these resources is not an option. Instead, the IEA recommends collecting more data so we can coordinate our use of the two resources—making sure we have enough water to generate electricity and enough energy to process water. 

One relatively easy fix is for local wastewater utilities to use the energy in the wastewater they process to power their own facilities. The IEA predicts that by ramping up this technology across municipal wastewater treatment plants, they could produce over 55% of their own energy by 2040. As an example of what’s possible, the Marselisborg wastewater treatment plant in Denmark produces 50% more energy than it needs by both using advanced process optimization and SCADA to run efficiently while generating power with biogas engines and a heat exchanger.

If different industries start cooperating with each other, they could also start sharing water. For example, power plants could re-use water from nearby oil and gas operations for cooling rather than pumping their own. Creating a circular energy-water economy like this will require industries to share data. They need to share how much water they need and how it needs to be treated to create re-use cycles that will minimize energy and ensure it doesn’t corrode, scale or otherwise foul pipes and equipment.

Even without these more ambitious cooperative solutions, the IEA says that water processes can reduce the amount of energy they need by 13% just by improving operations efficiency. It recommends that industries start just by collecting data so they can benchmark and track their progress on energy and water efficiency. Water utilities, it says, need to treat efficiency with the same importance they give to health and quality standards.