Study Shows How Water Systems Could Deliver Grid Flexibility

Analysis from Stanford University shows how water systems such as desalination plants and wastewater treatment facilities could help deliver grid flexibility.

The study, which was published in the journal Nature Water, was focussed on the development of a unified framework assessing the value of energy flexibility from water systems from the perspectives of electric power grid operators and water system operators.

Specifically, water asset flexibility was represented using grid-scale energy storage metrics, i.e. round-trip efficiency, energy capacity and power capacity, with assessment of the technoeconomic benefits of energy flexibility at the water facility scale, i.e. levelised cost of water and levelised value of flexibility.

It compares these values to other grid-scale energy storage solutions, such as lithium-ion batteries, and also takes into account a range of factors, such as reliability risks, compliance risks and capital upgrade costs associated with delivering energy flexibility using critical infrastructure systems.

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With water systems using up to 5% of electricity in the US, the potential for helping to balance power grid supply by adjusting their operations to align with real-time energy needs should be significant.

Applying the framework to case studies of a seawater deslination plant, a water distribution network and a wastewater treatment plant, the researchers found that these systems could shift up to 30% of their energy use during peak demand times.

The greatest potential was found for desalination plants, with tweaking how much water they recover or by shutting down specific operations when electricity prices are high.

“If we’re going to reach net zero, we need demand side energy solutions and water systems represent a largely untapped resource,” said study lead author Akshay Rao, an environmental engineering PhD student in the Stanford School of Engineering.

“Our method helps water operators and energy managers make better decisions about how to coordinate these infrastructure systems to simultaneously meet our decarbonization and water reliability goals.”

The researchers also found that upgrading facilities to improve their energy flexibility is often a good investment and is usually cheaper than adding battery storage on-site.

Assessment of the effect of different tariff structures and electricity rates from utilities in California, Texas, Florida and New York indicated that different pricing systems have the biggest impact on whether these upgrades will be profitable.