Cheaper Green Power Turns Seawater Into Drinking Water

January 28, 2025

Large parts of the world face a tough challenge: their populations are growing, and they need to find a way to provide water for them. Desalination, removing salt from seawater or salty groundwater, is the main source of drinking water for many countries. In many places, it is seen as a last resort because of high electricity costs. The energy required to operate a desalination plant often reduces the feasibility of those projects, especially when compared to other strategies.

The plummeting cost of renewable energy is changing those calculations.

“Desalination technology holds great promise for addressing global water scarcity and improving sanitation through several key advancements,” said IEEE Member Rafel Muniz. “Researchers are making strides in developing more energy-efficient desalination processes to cut down on overall energy consumption. By treating various types of impure water beyond just seawater, desalination can become more versatile and applicable in diverse regions.”

Desalination is Energy-Intensive

Water treatment plants are usually situated in places that take advantage of the natural flow of water. These site selection choices help lower the costs associated with pumping the water to the facility and to businesses and households that will use it.

Desalination plants don’t have that luxury. By their nature, they are usually located at sea level, and just about everything flows toward the sea. They need to pump water from the ocean and pump it out of the facility to the end user.

Plants rely on constant electricity to produce pressurized flows through the reverse osmosis membranes that filter salt from water. Energy often accounts for 36% of a desalination plant’s operating budget, according to the U.S. Department of Energy.

Using Renewables to Power Desalination

As renewable energy becomes less expensive, engineers face the question of how to use it smartly. Once the infrastructure is in place, renewable energy is inexpensive. But renewable energy sources aren’t always available: the sun doesn’t shine, and wind doesn’t blow at the same time people need power. Sometimes, there’s a surplus when demand is low; at other times, there might not be enough energy to meet everyone’s needs.

A recent study in the IEEE Journal of Modern Power Systems and Clean Energy explores this issue in depth, focusing on regions that rely on traditional power plants and renewable sources for electricity and desalination plants for water. When there’s more renewable energy than immediate demand, should we invest in batteries to store surplus electricity for later, or use that extra energy to produce and store freshwater in large tanks?

The study’s findings show that the ideal solution depends on the specific circumstances. Both batteries and tanks can help reduce costs by shifting energy use from busy times of day to quieter times. Generally, freshwater tanks cost less to implement than large arrays of batteries. However, batteries have the advantage of flexibility since they can supply electricity for any purpose, not just for producing freshwater.

In regions that are still partly reliant on renewable energy, building freshwater tanks often proves more cost-effective. But as the share of renewable energy grows, tanks and batteries become increasingly valuable tools for balancing supply and demand.

“To scale up these technologies effectively, it is essential to navigate crucial transformation stages and foster dialogue between developers, industry, government and civil society,” said IEEE Member Suélia Fleury. “True progress will come when all stakeholders collaborate, prioritizing the environment and human well-being in harmony.”