Energy Storage

[johnhemming2]

http://www.theguardian.com/environment/ ... eakthrough

An interesting article even if the journalist gets confused between energy and power.

[fuzzy]

The rail mass lifting storage system seems obvious, scaleable, modular, with few critical failure points. Perhaps we will be the last country to adopt it, along with the functional tidal barrage we designed for the Severn about 80 years ago.

http://www.notechmagazine.com/2013/08/r ... orage.html

[PS_RalphW]

I seriously doubt that a rail mass storage system would be cost effectitve, efficient or practical.

1. The cost of building for each KWh of potential energy storage would be huge.

2. The land needed would be absolutely massive.

3. The rolling resistance and energy losses would be very high. I can imagine that the efficiency would be a tiny percentage figure - 10 KWh in for 1 KWh out.

Small scale, it might be more practical. Gravity potential energy is
0.00136 Wh / M Kg

So 1000KG raised 10 Metres has 13.6 Wh of potential energy. A block of iron 10M on a side is 7,874 tonnes. Raised 10M would have potential
energy of 13.6 * 7.874 = 107 kWh . Lead acid batteries would be a lot smaller and a lot cheaper.

Of course, any old rock would be a lot cheaper and nearly as dense. However. the space storage and building costs would be huge. Reliability and lifetime, if carefully maintained, could be measured in centuries.

Edited for calculation error.

http://www.energystoragenews.com/Energy ... eights.htm

Edit 2

Our house is on a plot of land of about 1000 M2.

Dig out the plot to 20 M deep. Keep half the rock as your weight, sell the other half . Build your lifting frame into the hole, add the motors and control system, put back the weight rock. Relay your garden and rebuild your house.

Rock density 2.5. g/cm3
Potential energy of system is 3,400 KWh or about my annual domestic consumption. (including some electric car charging).

Or it would offset renewable energy variability for about 100 - 1000 homes (depending on the level of cover you need).

[adam2]

I seriously doubt that a rail mass storage system would be cost effectitve, efficient or practical.

1. The cost of building for each KWh of potential energy storage would be huge.

2. The land needed would be absolutely massive.

3. The rolling resistance and energy losses would be very high. I can imagine that the efficiency would be a tiny percentage figure - 10 KWh in for 1 KWh out.

Small scale, it might be more practical. Gravity potential energy is
0.00136 Wh / M Kg

So 1000KG raised 10 Metres has 13.6 Wh of potential energy. A block of iron 10M on a side is 7,874 tonnes. Raised 10M would have potential
energy of 13.6 kWh . Lead acid batteries would be a lot smaller and a lot
cheaper.

Of course, any old rock would be a lot cheaper and nearly as dense. However. the space storage and building costs would be huge. Reliability and lifetime, if carefully maintained, could be measured in centuries.

Yes, and also what about the NIMBY factor !
Look at the hysteria surrounding the building of HS2 or even about electrifying an existing railway line.

Now consider the scale of objections to building a few dozen rail lines up inclines in national parks, together with the overhead electrification and high voltage grid connections.
Daft idea, at least in the UK.

[emordnilap]

The rail mass lifting storage system seems obvious, scaleable, modular, with few critical failure points. Perhaps we will be the last country to adopt it, along with the functional tidal barrage we designed for the Severn about 80 years ago.

http://www.notechmagazine.com/2013/08/r ... orage.html

Notwithstanding Ralph & Adam's objections, this is similar to the project posted about some time ago by Biff - the notion of pumping water out of a 'hole in the ocean' using excess renewable energy, letting it drive turbines on its way back in when the energy is required. I can't remember how feasible the idea was or how far it had been investigated but but how does that one compare?

[johnhemming2]

Entropy is always the big issue.

[Pepperman]

Here's an interesting alternative to the (potential) rail energy storage solution linked to above: (kinetic) rail energy storage...

https://www.ecn.nl/news/item/floating-t ... ectricity/

It tackles some of Adam's criticisms of the potential energy approach.

To compare the two I make it that a 1000 tonne train being lifted 1000m would have the same potential energy as the kinteic energy in a 1000 tonne train moving at 140m/2 (a bit over 300mph).

[mikepepler]

Sounds like a challenging project to build, given the train has to run in a vacuum... It would be interesting to see a comparison with flywheels. I wonder what the round trip efficiency would be?

[Pepperman]

Yeah I have no idea about the engineering feasibility of this. I just like the fact that it's underground, so not taking up land space, and comfortably GW-scale and I assume highly dispatchable.

It would be interesting to know what sort of power per tonne is required for levitation but I haven't found the answer to that yet. I imagine in a conventional maglev train it's probably relativley small compared to the power required to move the train at high speed but in a partial vacuum it would become dominant.

[adam2]

Cant see this being feasible.
Tunnelling costs about a million pounds a meter on the Jubilee line extension, expected to be more for Crossrail.

And remember that these trains have to run in a vacuum, making large tunnels vacuum tight sounds a hugely costly undertaking.

And again consider the NIMBY factor, plenty of objections to extension of conventional underground railways, despite them being er underground.

And we are still some way away from needing costly and untried energy storage.
I suspect that we could DOUBLE UK wind power capacity and still make use of the electricity as it is produced, without any need for storage.

Sensible use of international power interconnectors could allow still more wind power without needing storage.

[Pepperman]

Can't be a million a metre. Crossrail cost about £15 billion and has 26 miles of tunnels (plus twice as much surface track and a load of new and reconstructed stations).