A Californian company proposes using weighted electrically-driven rail vehicles on inclines to store energy. At times when the capacity of electricity supply exceeds demand the vehicles would be driven up inclined tracks, and when demand exceeds generation they are allowed to run down, generating electricity as they fall.
This link includes a video that shows a prototype vehicle (which appears to be built on a conventional locomotive chassis), an interview with a promoter, and an animation of a "farm" of these devices. There is a shortage of hard data, such as how much energy could be stored, for how long, and how steep the tracks are, etc., but a quick calculation shows that some thousands of these vehicles would be required for them to be useful. The control panel for this prototype has a power dial that appears to go up to only 20 kW. The promoter in the interview focuses instead on how the construction material can be recycled at end of life.
(Score: 2, Interesting) by dmanny on Tuesday July 03 2018, @09:00PM (1 child)
Of course rolling stock costs more than water, pound for pound.
The Wikipedia list misses some facilities by having a threshold of 1000MW.
I remember when this operation failed. The story today made me look into the current status, it appears to be online. It operates at a head of approximately 850 foot.
https://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_Station [wikipedia.org]
I also found the WP list of hydroelectric failures interesting.
https://en.wikipedia.org/wiki/List_of_hydroelectric_power_station_failures [wikipedia.org]
But your point is clear. That is a lot of trains, 2815. Making them each have 3e6 kg mass would be nearly impossible. Water in a reservoir stacks much nicer than trains. The energy efficiency is one thing, the maintenance costs for that much rolling stock would be prohibitive.
(Score: 3, Interesting) by bitstream on Tuesday July 03 2018, @11:52PM
In Australia, BHP in June 2001 had a trial with 682 ore cars and eight distributed GE AC6000CW locomotives with a total weight of 99 734 tons (99e6 kg). So just 85 train sets, but there are other complications like having to use a cog railway, wires with metal fatigue, wear, oil, sand etc. So I'll suspect the investment and maintenance will make it unfeasible.
If one could use magnetic energy storage. It may be way more efficient.