Utilising renewable energy sources such as solar and wind to generate clean power makes perfect sense. However, overcoming their intermittency problems (the Sun doesn’t always shine, and the wind doesn’t always blow), not to mention finding ways to reliably stockpile then release on demand the vast amounts of electricity required to maintain our modern lifestyles, has proven to be a real headache. In short, large-scale power storage is without a doubt the holy grail of renewable energy. Fortunately, California-based company Advanced Rail Energy Storage (ARES) could very well have got it right. Their answer: Utilise 100-year-old proven railway technology, and then let gravity take care of the rest.
Working much like a conventional pumped-storage hydropower facility, but without the water – the ARES system employs a fleet of electric traction drive shuttle-trains, operating on a closed low-friction automated steel network to transport heavy masses between two storage yards at different elevations.
During periods where excess energy is available on the grid, the shuttle-trains use the available electricity to power their individual axel-drives motors and transport their masses uphill to an upper storage yard. Then, when the grid requires energy to meet periods of high demand, this process is reversed. The shuttle-trains provide a continuous flow of masses returning to the lower storage yard with their motors operating as generators, converting the potential energy back into electricity. The end result is a reliable, highly capable system that approaches an 80 per cent charge / discharge efficiency.
The facilities are also highly scalable in power and energy, ranging from a small installation of 100 MW with 200 MW of storage capacity up to large 2 – 3 GW regional energy storage systems that boast capacities of 16 – 24 GW energy storage.
The ARES pilot plant, situated in Tehachapi, California was designed to even out intermittent power supply from a neighbouring wind farm and by all accounts works like a bomb. It features a pilot vehicle that weighs 5 670 kg and runs on a gauge track that’s 268 m in length.
The company is also busy constructing a full-scale commercial 500 MW plant that will extend the length of the track to 8 km and up the weight of the individual vehicles to 300 tons. It’s expected to operate 32 vehicles, each one being capable of absorbing or providing about 1.5 MW of power.
According to ARES co-founder William Peitzke, a number of viable sites in South Africa have already been identified and the company has applied for local patent protection. So watch this space.
For more information, visit www.aresnorthamerica.com
The following video illustrates an ARES plant in action: