“Rail cars are pushed to the top of a grade using excess power from renewable energy plants or when electricity demand is low. Then, when the wind drops, the sun stops shining, or electricity demand rises, the rail cars are released back down the hill, generating electricity through regenerative braking. The technology integrates recent advantages in motor/generator traction drives and power control technologies with proven rail technology to produce a reliable and highly capable system that approaches an 80% charge/discharge efficiency.”

The company, founded in 2010, is operating a pilot project in the United States. More information can be found at the ARES website and in this Gizmag article, which has more pictures. Videos of the system can be found here, here, and here. ARES is a great low-tech project that deserves praise for its sustainable thinking. One problem might be that climbing slopes is not what trains are good at, while it is the vertical distance travelled that matters. The consequence is that the method requires a lot of space. A 50 MW rail energy storage system needs an eight kilometre track on an eight percent grade with 32 vehicles, each weighing 300 tonnes.

There exists a low-tech method that needs less space. Energy Cache, an American firm founded in 2009, has been testing a method of gravity energy storage which is based on aerial ropeways. When it comes to transportation of passengers and goods in hills and mountains, aerial ropeways are more efficient than railways in terms of energy and space, and they are much cheaper to build. Ropeways might have the same benefits for energy storage.

KDD (edited by Alice Yaxley)

Low-tech Magazine editor Shameez Joubert spotted this cash ropeway in Grahamstown, South Africa.

Cash ropeways were used in shops from the 1880s to the 1960s. They worked in a similar manner to large-scale cargo ropeways. Bicable cash transportation systems were powered by a catapult device or by separation of the wires, monocable systems were operated by a small electric motor.

The Cash Railway Website is dedicated to cash ropeways and similar systems, but it does not mention any ropeway still in use. The system in the South African shop was installed in the 1960s and it still works. Thank you, Shameez!

In principal the goods coming downward from the up-station must to be thrice as heavy as the up-going load. The sliding down of the trolley and its speed depends upon the angle of elevation made by the cables installed with the horizontal ground.

A flywheel with bearing and bracket is used as a brake to control the landing speed of the trolley at the bottom-station. Communication between top and bottom stations is done by tapping the wire rope. The operator at the top-station strikes the wire rope with a stick to send a wave signal through the wire rope to the operator at the down-station. The operator at the down-station then applies the hand brake to control the flywheel.”

Read more (building plans included). In-depth article: “Aerial ropeways: automatic cargo transport for a bargain“. Related: Water powered cable trains & (for those lacking mountains) Electric road trains 1901-1950.