Energy storage trains are a fantastic idea to save energy. Energy grids supplied by renewable energy sources naturally benefit from energy storage of any kind. "Pumped" hydropower is one of the common "go to" solution for energy storage. As we are sure you are aware, water energy storage uses electricity off-peak to pump water. This more "traditional" method pumps water to higher elevations to take advantage of the power of gravity to power turbines downslope.
For instance, the Taum Sauk Hydroelectric Power Station, Missouri works exclusively using pumped storage hydropower. Yeah, "pumped" hydropower is great but a little dull. Why can't we replace water with something interesting, like say mini trains? That would be amazing, right?
Have we got your attention? Great, let's take a closer look at ARES' simple solution to energy storage.
Energy storage trains: Mini trains? Tell me more
A California-based company, Advanced Rail Energy Storage (ARES) have done just that. Their innovative land-based alternative to the "traditional" hydro-pumped storage method provides grid-scale energy storage using cute little trains.
These small electric locomotives use rail cars to push heavy concrete blocks to the top of an incline using excess power generated from renewable energy plants. As you'd expect, excess power is utilized during off-peak hours when grid draw-off is low. To release energy, when demand is higher on peak, you simply let the train roll back down the slope. The trains, under the influence of gravity, generate power through their regenerative braking systems, which is cool.
ARES claims that the system can respond to increase and decreases in demand in seconds. They also claim the system boasts charge/discharge efficiencies of 80 percent and can deliver constant power for periods of up to eight hours. Not too shabby. The energy might otherwise be wasted.
Energy storage trains: Testing the trains
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.
The system will comprise of 34 shuttle units and will operate on a combined 9.2 km track with elevation differences from top to bottom of 640 meters.
Company CEO Jim Kelly bigs up the system by saying that it can:- "be deployed at around half the cost of other available storage technologies. Just as important, ARES produces no emissions, burns no fuel, requires no water, does not use environmentally troublesome materials and sits very lightly on the land.”
This great idea is highly scalable with small installations of 100 MW with 200 MWh storage capacity up to large 2 to 3 GW systems with 16 to 24 GWh storage capacities. Not bad, and it uses little trains.
Energy storage trains vs. Hydropower
As the system doesn't require the use of water, ARES believes, their system 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. The company believes the system can respond to increased or decreased demand within seconds. William Peitzke, ARES' Director of Technology Development, says the system 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.”
ARES also add that the system boasts higher energy-to-power ratio than flywheels. They also have lower life-cycle costs when compared to batteries and faster ramp-up rates than pumped storage alternatives. Plus it has little trains, did we mention that?
Energy storage trains in more detail
The system borrows heavily from mining applications and uses software from computerized trains at airports. The technology, therefore, already exists and is nothing new.
Power is provided to the trains off the grid using a third rail that feeds the electrical motors.
This powers the trains for their ascent up the slope, here the energy is stored as potential energy. When the grid needs the power back the software allows the trains to run downhill at around 56 km/h "releasing energy all the way" explains Kelly.
The train motors become electrical generators that push the electricity back into the electrified rail and ultimately back to the grid. A large-scale deployment of this kind of system could handle 500 MW or more, which would require just under 13 kilometers of track. The stored energy can be "released" within the same hour, week or month after storage. What's better, with no loss over time.
Gravity, for all intents and purposes, doesn't decay. The idea is certainly a great idea and the basic principle is certainly sound.
The last word
So little trains, gravity, heavy weights and electricity, what could possibly go wrong? Accidents aside this innovative solution to energy storage is a refreshing take on some old principles. When compared to pumped hydropower alternatives this technology is certainly a great option. Especially for areas where water storage solutions are not practical.
Infrastructure construction costs will likely be a fraction of that compared to similarly sized systems and maintenance/life-cycle costs should be relatively modest in comparison. Maintenance downtimes could be easily scheduled with minimal disturbance to the system' performance given the use of several parallel track systems. Plus it uses little trains, which is just cool, to be honest.
How the market responds to this energy storage system is yet to be seen but the future is looking bright for ARES. We wish them good luck with their venture.
What do you think of ARES' proposal for an alternative to energy storage? Can you see any potential pitfalls with the system? Have you seen any similar systems that could be deployed on a micro-scale? Let's start a conversation.