Energy grids supplied by renewable energy sources benefit from energy storage of any kind. “Pumped” hydropower is one of the common solutions, pumping water to higher elevations to take advantage of the power of gravity to power turbines downslope.
A new rail system on the west coast of America, designed and manufactured by a Californian company, Advanced Rail Energy Storage (ARES), offers storage which doesn’t require the use of water and is suitable for a wider variety of areas with minimal environmental impact.
No valleys need to be flooded or large scale excavations undertaken to make reservoirs. It is basically a “grid-scale flywheel or battery, but one which is able to “lock into direct synchronization with the grid providing heavy inertia for added grid stability” according to William Peitzke, ARES’ Director of Technology Development. The system is said to have a higher energy-to-power ratio than flywheels and lower life-cycle costs compared with batteries and faster ramp-up rates than pumped storage alternatives. Francesca Cava, an ARES spokeswoman, claims an 85% efficiency “That’s what you get with steel wheels on steel track.” More detail here.
Wired explains that when the local utility has surplus electricity, it powers up the electric motors that drag 9,600 tons of rock- and concrete-filled railcars up a 2,000-foot hill. When it’s got a deficit, 9,600 tons of railcar rumble down, and those motors generate electricity via regenerative braking – in the same way as the Toyota Prius. Effectively, all the energy used to move the train up the hill is stored and recouped when it comes back down.
In 2016, ARES conducted a pilot system test in Tehachapi, California on a 268-meter track. After this test proved the concept, the company was granted permission to construct the grid energy system in Nevada. The fleet of automated 300-ton electric traction drive shuttle trains are due for completion anytime soon. These shuttles will travel up and down a 7.2% grade slope and should provide 50 MW of rapid response power to help stabilize the Californian electrical grid supply, responding to increased or decreased demand within seconds.
Or as the local Pahrump Valley Times puts it: “Using a solitary railroad track placed on a gentle grade, multiple electric locomotive cars can move up the track as they receive excess power from solar and wind power plants during sunny and windy days. The train cars will be active and will be dispatched slowly downhill, using their motor-generators to return power to the electricity grid as needed”.
At the turn of the millennium, California routinely suffered blackouts and power shortages. Since then billions of dollars have been invested in renewable energy and now its problem is not too little power but too much. Wet weather last winter and a windy, sunny spring have contributed to record hydro, wind and solar output and on numerous occasions in recent months the state has been producing more power than it needs.
Following the success of the test on a 268-meter track, ARES was granted permission to construct the grid energy system in Nevada, receiving approval from the Bureau of Land Management for its 5.5-mile track, and construction of the energy train is starting now: Spring 2017.