# Energy Storage Trains

1. May 23, 2016

### anorlunda

It can be depressing to reject so many ideas for power generation or bulk storage of energy. That makes it refreshing to read today's news about a new method that IMO sounds 100% credible in their claims, and that has a potential scalability that could far exceed pumped hydro.

The main reason that I find this easy to believe is that electric locomotives with regenerative braking systems have been in use for many years. No new technology needs to be researched or developed. The locomotive designs have already been refined over the years. Even their efficiency and cost claims can be backed by the records of extensive real-life experience, not just calculations or laboratory experiments.

The number of suitable locations for this scheme are far more than suitable pumped hydro locations. That's why I think they could really scale it big.

If I ever learn the names of the engineers who first proposed this, I would like to nominate them for awards.

2. May 23, 2016

### BvU

How about a posthumous award for this Sysiphus chap ?
Wouldn't it be a lot easier to pump water back over the Hoover dam into Lake Mead ?

3. May 23, 2016

### phyzguy

Where will you get the water? If we had the water to do that, then Lake Mead wouldn't be at a historic low point.

4. May 23, 2016

### anorlunda

Yes, you might be able to create a pumped hydro project there. But I'm sure that idea has already been studied and rejected by the engineers.

Pumped hydro is still a marvelous way to store energy. But the number of places geologically suited for that are very limited. Most of the best sites already have working pumped hydro projects.

Edit: Sysiphus would be an excellent name for the train project.

5. May 23, 2016

### anorlunda

You would have to build a second dam just downstream from the Hoover dam to make a reservoir pool. Water would be pumped from the pool to the lake at night, and allowed to flow back in daytime. The Hoover dam generators would also be the pumps. The capacity of the reservoir could be tiny compared to the capacity of Lake Mead. I would be very surprised if the basics of that idea have not already been looked. Since there is no proposal to go ahead, the idea was rejected.

Nevertheless, the Hoover idea could work, but the cost of a second dam should be compared to the cost of laying RR track up the mountain. I think the RR idea has lots of appeal.

6. May 23, 2016

### BvU

I was triggered by
Over here it's May already, but perhaps some digibetic journalist overlooked the date ?
So my first reply for the water was: unsold mineral water past the sell-by date .

Apparently however, this is a longer-lasting serious (?) effort to store "a few hours of energy supply for a medium-sized city".

If the US would waste ten percent less energy of their annual $10^{17}$ Joules (100 quadrillion Btu) that would be an awful lot better. Even better would it be if they bring their energy consumption to the level of civilized countries like France or Germany. But that would mean a whopping 40% reduction ! I wonder how much of Nevada you need to park all those trains ...

7. May 23, 2016

### Staff: Mentor

Erm - a hydro dam IS a pumped storage facility. The pump is the atmosphere and it is powered by the sun. You regulate it by lowering the flow at night and increasing it during the day.

Adding anew electric pump would just turn it into a failed Perpetual Motion Machine!

8. May 23, 2016

### anorlunda

Your cynicism is misplaced Russ. Take for example https://en.wikipedia.org/wiki/Blenheim-Gilboa_Hydroelectric_Power_Station built in 1973 in upstate NY. It has a pumped storage capacity of 5000 MWH, and a rating of 1100 MW. It uses the same turbines to both pump and generate. Water is pumped between lower and upper reservoirs. The storage efficiency is 73%. It is most certainly not perpetual motion.

In principle, the Blenheim-Gilboa project is not so different than pumping water back to the top of the Hoover Dam.

9. May 23, 2016

### Staff: Mentor

Oops, yeah, I misread the proposition - I thought the second dam would produce power to pump water back up the first!

10. May 26, 2016

### mheslep

I see the utility of the storage train via its low cost per unit of energy, though the scope is hopelessly limited in comparison to mainstream power sources.

For example, the Colorado River, which feeds the Hoover dam, has a flow rate of about 500 cubic meters per second, or 500 metric tons per second. Assume a storage train of mass, say, 1000 mt descends a grade with the same elevation change as the Hoover Dam over a track of perhaps 20 km, traveling 80 kph, for a run time of 15 mins (900 secs), or about 1.1 mt per second. The Colorado in this case provides nearly *500* times more power, and it doesn't quit to recharge after 15 minutes.

11. May 26, 2016

### anorlunda

@mheslep I admire a man who likes to do actual calculations. But your example is a bit undersized.

Long heavy trains take much longer than 20 minutes to climb/descend mountain passes, and those passes are much higher than 700 feet for the Hoover Dam.

The Fortescue train in AU is 40,000 mt which would require 16 VR Class SR2 locomotives to haul it. for a total electric rating of 96 MW. I couldn't find the vertical grade it navigates.

A simpler approach: 40,000 mt raised by 3000 m vertical height is work of 327 MWh. There are lots of places in the Rocky Mountains to do that. In the Appalacian Mountains, vertical lifts of 1000 m are common.

You are correct. A single train storing 100-300 MWh is much smaller than a pumped hydro storing 5000 MWh, but 20 miles of RR track are very much cheaper to build than a dam, and several trains per day could use the same track.

12. May 26, 2016

### mheslep

Sure there are greater elevation changes over longer runs. Power delivery is proportional to mass times the rate of climb (or descent), regardless of length. Power is in the tens of MW for train storage, and is still largely irrelevant for the needs of the power grid. One might as well run a big diesel genset.

Also, the geographical needs of track are not insignificant. Track may not take up that much area or submerge river valleys, but unlike pipelines and electric transmission, track does subdivide the land it crosses.

13. May 26, 2016

### anorlunda

Why do you say tens, when I just showed hundreds?

Edit: Whoops, you said tens of MW, I was saying hundreds of MWh. Sorry. Still, if tens of MW are insignificant, then all the kings solar and all the kings wind are insignificant.

Actually, the "right size" for grid storage is the size of a large solar or wind farm. If they want to compete with the base loads, let the investors who build the solar/wind farms also invest their money in the energy storage needed to deliver their product around the clock. In that context, RR storage is just about right sized.

Last edited: May 26, 2016
14. May 26, 2016

### mheslep

The relevant size for the US is the size of US electric capacity or about 1 TW if it is all to be replaced eventually with solar and wind as some would insist. All solar and wind output combined can be expected to drop to near nothing at times, so the backup capacity must be similarly sized, on the order of a TW, and several days deep. So no, tens of MW sized storage trains can not do much more than smooth over the gaps and bumps, which is in fact how utilities use storage presently.