Cool power plants with salt water to preserve freshwater supplies, scientists say

Salty groundwater has the potential to replace fresh water to cool coal and natural gas-fired power plants, an analysis led by University of Wyoming researchers has found.

With freshwater supplies threatened due to drought, climate change and rapid socioeconomic growth, water competition is increasing between the electric power sector and other sectors.

Further, efforts to decarbonise fossil fuel-fired power plants by carbon capture and storage would significantly increase water consumption.

“Non-traditional water sources can be deployed to help cope with climate-induced water risks and tackle the increasing water demand for decarbonisation of fossil fuel-fired power plants,” the researchers wrote.

“Treatment of brackish groundwater for thermoelectric generation cooling can help alleviate potential competition for freshwater resources among various sectors in water-stressed regions.”

Removing excess dissolved salts and minerals from brackish water can itself be energy intensive and produce concentrated brines requiring disposal. A method known as ‘zero liquid discharge’ minimises the environmental impacts of desalination, but is also particularly costly.

The researchers examined the technical and economic feasibility of multiple desalination processes and also estimated how much fresh water would be saved as a result of treating brackish water for power plant cooling.

They concluded that retrofitting power plants to treat brackish groundwater could nearly eliminate the use of freshwater, but would increase the cost of electricity generation by 8 per cent to 10 per cent.

“Our study reveals trade-offs in freshwater savings, cost and generating capacity shortfalls from desalination deployment,” said researcher Zitao Wu.

The team called for further development of technologies to treat brackish water, along with exploration of using other nontraditional water sources for cooling of power plants.

Those include treated municipal wastewater, as well as water produced from oil and gas extraction and carbon dioxide storage reservoirs.

In January, Japan approved plans to start releasing 1.5 million tonnes of treated water from the Fukushima nuclear power plant into the ocean as storage space runs out.

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