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Could the Hoover Dam become a giant battery?

The Hoover Dam could be set to undergo a major retrofit to add a wind and solar-powered pump station, acting as an energy storage unit for the Southern California region. But how feasible is the plan?

The Hoover Dam was undoubtedly one of the greatest construction achievements of the 20th century. Built in the 1930s, this supersized arch dam measures 221m from top to bottom, and 379m across the crest. It generates an average of 4 billion kWh of hydroelectric power each year, enough to serve 1.3 million people.

The dam has always had multiple uses – flood and silt control, agricultural irrigation and domestic water supply, to name a few. Now a new project has been proposed, which would effectively turn the Hoover Dam into a gigantic battery.

Under the $3bn proposal, a renewable-powered pumping station would be built 20 miles south of the dam, serving to regulate the water flow through its generators. Water would be pumped from downstream back up to the top, and released for power on demand. In essence, the dam would be able to store renewable energy as well as produce it.

As advocates see it, the project could massively increase the dam’s productivity, adding at least 500MW of potential output. More than that, it would solve one of the West Coast’s trickiest energy problems: balancing energy production against demand.

“Solar energy is produced when the sun is shining and wind energy is produced when the wind is blowing, and we don’t have much of a say in when it’s produced,” says Peter Gleick, co-founder of the Pacific Institute think tank. “We’ve been trying to figure out how we can better integrate renewable energy into our bigger energy system, so that’s the idea here – if there was some way to store excess energy, then we can use it later when the demand is higher.”

If the Hoover Dam were used for this purpose, less of California’s energy production would go to waste.

Balancing the energy mix
Aptly nicknamed the Sunshine State, California is a major producer of renewable energy. Last year, renewables accounted for 27% of the state’s energy mix, and it looks to be on course to achieve its goal of hitting 50% by 2030. Solar energy especially is booming, surging from 0.5% of the mix in 2010 to 10% in 2017.

On very sunny days, however, the state’s solar panels produce more energy than is possible to use. For instance, on 5 March this year, production was 50% higher than demand. Much of it is passed on to neighbouring states to avoid overloading California’s own power lines.

Since the state has limited ability to store this power, other forms of energy production are still necessary. Perhaps counterintuitively for a state with an oversupply problem, it relies on imports for around a quarter of its energy needs.

The Hoover Dam proposal, then, would be instrumental in helping the state improve the reliability of its energy supply. This is a particularly loaded topic following the signing of the SB 100 bill, which saw California commit to 100% carbon-free power by 2045.

An economic white elephant?
Earlier this year, the Los Angeles Department of Water and Power (LADWP) pitched the concept to interested parties, including groups across the Southwest that receive power from the Hoover Dam. It has subsequently been reported in New York Times, prompting scepticism and excitement in equal measure.

This does not mean, however, that the proposal will necessarily go ahead. As Gleick points out, there is a big difference between considering an idea and moving forward with it.

“I think any proposal that tries to address Western US energy challenges is worth consideration, but this is really just an early-stage idea at this moment,” he says. “While I think it’s worthy of evaluation, I’m somewhat sceptical that it would address the core of the problems that we face.”

Read full article at Power Technology