The system works by storing energy as potential energy driving by gravity. Boxcars heavy with gravel are driven up a 7% grade by electric motors.
Renewable energy production is often intermittent and isn’t produced when there is demand for it, which is why energy storage solutions are being researched so fervently.
There are various approaches to energy storage, especially in conjunction with renewable energy. Solar power is only produced when the sun shines, which means cloudy days and nighttime a a no-flow.
Hydroelectric power depends on rainfall, and wind power is also dependent on the weather. Inconsistent renewable power generation can be met by energy storage solutions, to which there have been a number of approaches.
The idea is to change excess or intermittent energy into another form, effectively storing for later use. Batteries store energy chemically, but are notoriously expensive and have a short lifespan.
Compressed air stores energy under compression, but is only up to 70% efficient. Hydroelectric storage, pumping water behind a dam and releasing it later, depends on weather just as much as hydroelectric power does. Flywheels are nearly 85% efficient and can last for decades, but are also very expensive. We’ve covered gravity-driven systems before, and a new boxcar energy storage solution could be nearly 90% efficient.
Advanced Rail Energy Storage is going to build a prototype next month to test the theory. Since gravity doesn’t degrade over time, the heavy boxcars store this potential energy for hours, days, even years, and then release it when needed.
When energy is needed, the boxcars are released and run down the hill up to 35mph, generating electricity the whole way. ARES believes the energy storage system could be 90% efficient and expects 500 MWh of storage to take about 8 miles of track.