Energy Storage

[Bill Phil]

@PB666

Huh.... You posted within the quote. And according to wikipedia methanol has 15.6 MJ/L, while LPG propane has 25.3 MJ/L. Compressing increases the amount per liter.

Edited December 6, 2015 by Bill Phil

[micr0wave]

Power storage on a larger scale only makes sense with a huge percentage of renewable 'free' energy.
So a super efficiency isn't the top priority at start, that will come with time.
In germany gas made from coal was used for long times, it was almost 50% hydrogen and there was some smelly stuff mixed in so you could notice it in even smallest concentrations.
Given some water and power and a bit of bioreactor you could make methanol pretty easy with hydrogen and the carbon components from the biochain.
So for larger scale stationary simple hydrogen based electrolyse/fuel cell doesn't sound too bad, or, like in the OP, for offshore windparks that aircompression seems to be good too.
I think there isn't a one-fits-all solution, a healthy mix should be the best approach.

[AngelLestat]

Ok I will not quote because there is many people saying the same thing.

Hydrogen volume:  too high to be used in normal vehicles..

Honda clarity:  Range 700km, space required (the same than any car), cost: 50000 EU,  but much cheaper in japan, tanks capacity: 150 liters (3 times more than gasoil tanks as I said)

http://www.cnet.com/products/2016-honda-clarity-fuel-cell/

http://www.forbes.com/sites/joannmuller/2015/10/27/hondas-new-hydrogen-powered-vehicle-feels-more-like-a-real-car/

Pictures:

Free space in the front - Trunk - from side - H2 Tanks

 

Hydrogen is hard to handle and not safety... 

Hydrogen systems are super safe, I will said more than any other stuff using fuel. They do it that way for the hysteria that people has around hydrogen.

Any leak is detected by tons of sensors and valves that measure how much hydrogen you charge and use it.  Windows open automatic if that happen.  And even if they dont.. hydrogen escapes anyway.

Tons of extra safety measures that I will not even mention.

Gasoil gases and liquid stays close to any leak and waits until the right moment to BOOM. Hydrogen leaks in seconds and always the flames goes up. Tanks are hard as rocks, they can hold hydrogen by a lot of time (they are not ballons) and they can not explote.  They can resist bullets.  And even if you use a barret, it will just leak fast without explosion.

Each fuel has their procedures,  measures and devices to be handled..  This is true for gasoline, gasoil, natural gas, jetfuel and hydrogen..  Of course you can not use a gasoline tank with a gasoline expenser to handle natural gas, neither natural gas devices to handle gasoline.. Is stupid.  The same happens with hydrogen devices and dispensers, they will be just different. 

There are new ways to detect hydrogen already test it but still shaping the final product like thermal cameras, and graphene oxyde that is cheap and can detect hydrogen % in the air with great accuracy.

 

Batteries are better:

Depends, if the car is light or does not need long range, then yes. But batteries are expensive, Why all  lithium batteries cars are luxury class? Because they need to camouflage some way the price of batteries.

Today Tesla car batteries cost around 25000 the whole pack, if we wait until 2020 when the gigafactory will be at full capacity the cost will drop a 30% --> 18000 dollars. But for that cost you can buy a whole new car. That cost will not drop until they arrive with a new battery tech (air battery which will take at least 8 to 10 years).
In addition, batteries has a lifetime, so eventually you need to pay for a new full pack of batteries or change the car.

Fuel cells in few years achieve a great improve in power density (4 times smallers for the same power), they also become cheap, and that taking into account that we need to wait 1 to 3 years to remplace platinum with cheaper materials without decrease efficiency.

 

Different ways to storage hydrogen.

Liquid cryo: In this form has the best energy density by volume, but you lose a 40% of the energy in the change of state and temperature lost.  Now there is a new way to liquify hydrogen using magnetic refrigeration that only lose 20% of the energy, this is not a problem with future h2 jet airplanes, because you use that cooling and you help to expand the gas with the heat product of your speed.

700 bar: the most used today, you lost just 3% of the energy.

350 cryo compressed: New standard (germany used both), This has a little more density by volume than 700bar.

[Bill Phil]

Hydrogen's energy per volume is too low to just be used in any regular car, that's the point. And for any particular energy amount, a larger tank is needed. Thus more fueling time, and also more money than a similarly sized gasoline tank. Producing 1/4 the energy requires 4 times the tank size.

That's why hydrogen is hard to handle, it needs so many sensors and safety features while all you need for good old gasoline is a simple metal tank. Oh and that car, btw, probably had a venting mechanism, because hydrogen is so dangerous. The gas car had no such system, and thus the comparison is not valid. That's not to say it's true that it did have one, but it sure looked like it. And what instance caused that fuel to escape like that? What's the test? That's kind of important to know

Batteries are getting cheaper. What about the cost of a fuel cell, it's complexity, and hydrogen's cost. The running costs? Heck, some high performance engines (you're forgetting that's technically a performance battery for a luxury car...) cost upwards of 10,000 dollars as well.

Higher pressure ways are inherently more dangerous... And more expensive.

 

The problems can be solved, but they're expensive to solve. Hydrogen isn't practical as a mobile vehicle fuel. Except maybe large jets...

 

Anyone who is budget minded won't go for hydrogen. Anyone who is practically minded won't go for it, either. It's not a good choice. Electric cars are simply better. NO fuels involved. No tanks, no nothing. Enormously safer than both gas and hydrogen. And there energy densities and costs will improve to such a degree relatively soon that it'll become usable. Nissan Leafs already cost about the cost of an average car. It's range is much less, but it's there.

[AngelLestat]

On 12/5/2015 at 7:52 PM, Bill Phil said:

Hydrogen's energy per volume is too low to just be used in any regular car, that's the point. And for any particular energy amount, a larger tank is needed. Thus more fueling time, and also more money than a similarly sized gasoline tank. Producing 1/4 the energy requires 4 times the tank size.

Negating the reality?  I show you Honda Clarity pictures and properties, 700km, only 3 times more tank volume (not 4) but you save a lot of space with the engine.. So in resume.. It consume the same space.

Taking into account that h2 cars are just new and they will keep improving. They dont pollute and you save half of the money in fuel.  The fuelling time is 3 min.  Uh sorry, you need to wait 1 min longer.   

 

Quote

That's why hydrogen is hard to handle, it needs so many sensors and safety features while all you need for good old gasoline is a simple metal tank. Oh and that car, btw, probably had a venting mechanism, because hydrogen is so dangerous. The gas car had no such system, and thus the comparison is not valid. That's not to say it's true that it did have one, but it sure looked like it. And what instance caused that fuel to escape like that? What's the test? That's kind of important to know

Lol.. OMG so much rage against hydrogen... Sensors are cheap, and many of those are just there to increase the fuel cell efficiency that as bonus point also help to detect any leak, the same that you have a lot of sensors and a computer to manage all valves which is called the "injection system" in gasoline cars.

About hydrogen sensors: https://ec.europa.eu/jrc/sites/default/files/Hydrogen%20safety%20sensors_en.pdf

And there are more cheap and small sensors in the way using graphene oxyde for 2017 or before. You are also ignoring all the points where hydrogen is safer than gasoline. As I said, is not more dangerous, is just flamable as any fuel, it has different properties and you need special devices the same as any fuel. 

 

Quote

 

Batteries are getting cheaper. What about the cost of a fuel cell, it's complexity, and hydrogen's cost. The running costs? Heck, some high performance engines (you're forgetting that's technically a performance battery for a luxury car...) cost upwards of 10,000 dollars as well.

Higher pressure ways are inherently more dangerous... And more expensive.

 

With a [poor] range and waiting 20 min in recharge?  And all that with a battery cost equal to a gasoline car cost?  Batteries are not bad, but there are not being made for big and heavy cars, the cost is too much not just for production limitation, for a nature law give it by the energy density, weight and materials. Meanwhile hydrogen fuel cells or electrolysis are very close to get rid of the platinum, and they still need to reach the production rate that lithium batteries already had. That is why all the new hydrogen tech companies are showing higher cost of shares in the stock market.  

 

Quote

The problems can be solved, but they're expensive to solve. Hydrogen isn't practical as a mobile vehicle fuel. Except maybe large jets...

Anyone who is budget minded won't go for hydrogen. Anyone who is practically minded won't go for it, either. It's not a good choice. Electric cars are simply better. NO fuels involved. No tanks, no nothing. Enormously safer than both gas and hydrogen. And there energy densities and costs will improve to such a degree relatively soon that it'll become usable. Nissan Leafs already cost about the cost of an average car. It's range is much less, but it's there.

What you want I said?  is already happening.  Because countries needed as storage, car makers needs a vehicle with high range and low charge time with a future potential low cost. 

They also need a co2 free system for trucks, ships, and any other kind of vehicle. Even the army is testing tanks with fuel cells. 

Edited July 4, 2016 by Vanamonde
Language.

[PB666]

12 hours ago, Bill Phil said:

Hydrogen's energy per volume is too low to just be used in any regular car, that's the point. And for any particular energy amount, a larger tank is needed. Thus more fueling time, and also more money than a similarly sized gasoline tank. Producing 1/4 the energy requires 4 times the tank size.

That's why hydrogen is hard to handle, it needs so many sensors and safety features while all you need for good old gasoline is a simple metal tank. Oh and that car, btw, probably had a venting mechanism, because hydrogen is so dangerous. The gas car had no such system, and thus the comparison is not valid. That's not to say it's true that it did have one, but it sure looked like it. And what instance caused that fuel to escape like that? What's the test? That's kind of important to know

Batteries are getting cheaper. What about the cost of a fuel cell, it's complexity, and hydrogen's cost. The running costs? Heck, some high performance engines (you're forgetting that's technically a performance battery for a luxury car...) cost upwards of 10,000 dollars as well.

Higher pressure ways are inherently more dangerous... And more expensive.

 

The problems can be solved, but they're expensive to solve. Hydrogen isn't practical as a mobile vehicle fuel. Except maybe large jets...

 

Anyone who is budget minded won't go for hydrogen. Anyone who is practically minded won't go for it, either. It's not a good choice. Electric cars are simply better. NO fuels involved. No tanks, no nothing. Enormously safer than both gas and hydrogen. And there energy densities and costs will improve to such a degree relatively soon that it'll become usable. Nissan Leafs already cost about the cost of an average car. It's range is much less, but it's there.

I don't think hydrogen storage is the problem. Want to store hydrogen, take some tar sand oil, heat it up under pressure and add the hydrogen to it, it becomes oil. Lots of benzene in gasoline,oxidize it once with a good leaving group and hydrogenate it. You can even add hydrogen to metals. We have lots of things we can hydrogenate if that were and issue to increase density. 

But its not an issue. As far as hydrogen safety is concerned the synergy drive in a hybrid is far more cpmlex than the technology to safely store hydrogen. These issues being brought up are all red herring issues, just like the batteriy fears when hybrids first came out, nothing but noise. 

[PB666]

14 hours ago, Bill Phil said:

@PB666

Huh.... You posted within the quote. And according to wikipedia methanol has 15.6 MJ/L, while LPG propane has 25.3 MJ/L. Compressing increases the amount per liter.

The quote system in the new GUI is not working well, propane has a pressurization problem when working at high temperatures, nativel at stp+20' methanol is more stable to use. The other problem is that propane is in large demand, its a volatile that comes from fracking, which will eventually taper. Methanol can be synthetically made without any organic starting materials

1. Take sea water add hcl, CO2 evolves, heat and apply slight vacuum. 

2. condense and cool and add cold water, any number of reduction operations to form carbon monoxide

3. hydrogenate the carbon monoxide

4. the resultin formaldehyde is suitable for further reduction to methanol, it can also be pressurized for use as a fuel directly in closed systems. 

I should add that there are bacteria that can produce hydrogen directly, if you can couple a two cyst system you could produce pure oxygen and hydrogen in the same system, but unlike biofuel microbes you dont have to kill the microbes to extract the products. You just have to carefully separate hydrogen from oxygen. 

 

 

 

[PB666]

http://www.sciencealert.com/scientists-have-built-a-microbial-fuel-cell-that-works-without-external-power

This is the most unlikely technology, but ...........nah its a no-go. 

[todofwar]

On Sunday, December 06, 2015 at 11:43 AM, PB666 said:

I don't think hydrogen storage is the problem. Want to store hydrogen, take some tar sand oil, heat it up under pressure and add the hydrogen to it, it becomes oil. Lots of benzene in gasoline,oxidize it once with a good leaving group and hydrogenate it. You can even add hydrogen to metals. We have lots of things we can hydrogenate if that were and issue to increase density. 

But its not an issue. As far as hydrogen safety is concerned the synergy drive in a hybrid is far more cpmlex than the technology to safely store hydrogen. These issues being brought up are all red herring issues, just like the batteriy fears when hybrids first came out, nothing but noise. 

Hydrogenating benzene just gives you some cyclic alkanes, so basically back to gasoline (I know, not the same compounds but basically hydrocarbons). Boro hydride is pretty good in terms of mass density, but really a good tank will win out for storage. Granted, the tank will become brittle over time.

And of course, the vast majority of our hydrogen is from natural gas and coal, not the clean energy everyone thinks. 

As was already stated we will eventually move away from one size fits all tech. Some places will use gravity, either with water or with railway cars on a hill (my personal favorite). For jets there will be hydrogen, for cars most likely batteries, for rockets the EM drive obviously (that last one was a joke). It's pointless to force one solution for everything. 

Edited July 5, 2016 by todofwar

[Windspren]

3 words for green energy: Molten salt reactors.

[PB666]

52 minutes ago, todofwar said:

Hydrogenating benzene just gives you some cyclic alkanes, so basically back to gasoline (I know, not the same compounds but basically hydrocarbons). Boro hydride is pretty good in terms of mass density, but really a good tank will win out for storage. Granted, the tank will become brittle over time.

And of course, the vast majority of our hydrogen is from natural gas and coal, not the clean energy everyone thinks. 

As was already stated we will eventually move away from one size fits all tech. Some places will use gravity, either with water or with railway cars on a hill (my personal favorite). For jets there will be hydrogen, for cars most likely batteries, for rockets the EM drive obviously (that last one was a joke). It's pointless to force one solution for everything. 

Diborane is actually a gas that can be used as a fuel, its very unstable though, more so than hydrazine.

https://en.wikipedia.org/wiki/Diborane

And you need an oxidizer. ISP is pretty decent given the mass, and you don't need an igniter, its does that all by itself in the presence of a trace of water.

[passinglurker]

So on pump storage its basically all about gravity potential right? So what about taking an old electric light rail or subway car, parking it at the bottom of a hill, and have it roll up to the top under its own power to store energy, and then roll back down with regenerative braking to release it? That sounds a bit more environmentally friendly than carving out dams right? Not to mention it could be done in barren deserts where there isn't any water to begin with.

[todofwar]

43 minutes ago, PB666 said:

Diborane is actually a gas that can be used as a fuel, its very unstable though, more so than hydrazine.

https://en.wikipedia.org/wiki/Diborane

And you need an oxidizer. ISP is pretty decent given the mass, and you don't need an igniter, its does that all by itself in the presence of a trace of water.

I meant as a hydrogen storage system, just add acid. Not for rocket applications

[todofwar]

56 minutes ago, passinglurker said:

So on pump storage its basically all about gravity potential right? So what about taking an old electric light rail or subway car, parking it at the bottom of a hill, and have it roll up to the top under its own power to store energy, and then roll back down with regenerative braking to release it? That sounds a bit more environmentally friendly than carving out dams right? Not to mention it could be done in barren deserts where there isn't any water to begin with.

I saw something on this very recently, I think they're building a test case somewhere. But yeah, you can fill the cars with solid lead, really bump up your energy density from water.

Not for individual homes, but how about this concept: attach really heavy lead weight to pulley system off the side of a skyscraper. Let it slowly descend as you use the pulleys to run generators. When you have a surplus you run the system in reverse to raise the weight again. By using lead you can get higher mass density and thus more stored potential energy per unit volume. If the building is high enough you can store quite a bit of energy this way. Of course, you wouldn't want them free floating out there, probably should encase them in some kind of shafts in case they snap and fall on someone. 

Even for an individual home, it would save space over a water pump system.

[passinglurker]

38 minutes ago, todofwar said:

Not for individual homes, but how about this concept: attach really heavy lead weight to pulley system off the side of a skyscraper. Let it slowly descend as you use the pulleys to run generators. When you have a surplus you run the system in reverse to raise the weight again. By using lead you can get higher mass density and thus more stored potential energy per unit volume. If the building is high enough you can store quite a bit of energy this way. Of course, you wouldn't want them free floating out there, probably should encase them in some kind of shafts in case they snap and fall on someone. 

so basically the old grandfather clock. technology has come full circle!

[todofwar]

13 minutes ago, passinglurker said:

so basically the old grandfather clock. technology has come full circle!

Very steampunk  but I think it might have some merit. 

[peadar1987]

1 hour ago, todofwar said:

I saw something on this very recently, I think they're building a test case somewhere. But yeah, you can fill the cars with solid lead, really bump up your energy density from water.

Not for individual homes, but how about this concept: attach really heavy lead weight to pulley system off the side of a skyscraper. Let it slowly descend as you use the pulleys to run generators. When you have a surplus you run the system in reverse to raise the weight again. By using lead you can get higher mass density and thus more stored potential energy per unit volume. If the building is high enough you can store quite a bit of energy this way. Of course, you wouldn't want them free floating out there, probably should encase them in some kind of shafts in case they snap and fall on someone. 

Even for an individual home, it would save space over a water pump system.

E=mgh, so if you had a block of lead the size of a lift car, say 2m x 2m x 2m as a rough estimate, it would have a mass of about 91,000kg. 100t cranes are a thing, so that shouldn't be a problem. If you lifted it up to the top of a 200m skyscraper, you would have 91,000 x 200 x 9.8 = ~180MJ (50kWh). The average energy consumption of an American home is about 1.2 kW, so 180MJ would provide one house with energy for 150,000 seconds (1 day, 17 hours).

Lead costs about $1.70 per kg, so the system would contain about $155,000 worth of lead. That works out at around $3100/kWh, just for the lead. Lithium ion batteries are hovering at about $200 per kWh at the moment. Dinorwig power station in Wales can store about 9GWh of energy, and cost £425m to construct in 1984 (about £4 billion in today's money, $5.2 billion). This works out at about $600/kWh (but with a significantly longer lifespan than a typical lithium battery)

The reason water works so well is because it is essentially free, and it's easy to work with. The technology scales very well too if you have somewhere with the right topography, it's relatively easy to make a container that can hold a huge amount of water for a relatively tiny pump and generating station. It's a lot harder to do the same with lead, or rail cars, or whatever, because it's a lot more expensive to increase the mass you have to play around with.

 

3 hours ago, Laythe Dweller said:

3 words for green energy: Molten salt reactors.

When we solve the problem of operating them long-term. Molten salt gives material scientists nightmares!

[todofwar]

7 minutes ago, peadar1987 said:

E=mgh, so if you had a block of lead the size of a lift car, say 2m x 2m x 2m as a rough estimate, it would have a mass of about 91,000kg. 100t cranes are a thing, so that shouldn't be a problem. If you lifted it up to the top of a 200m skyscraper, you would have 91,000 x 200 x 9.8 = ~180MJ (50kWh). The average energy consumption of an American home is about 1.2 kW, so 180MJ would provide one house with energy for 150,000 seconds (1 day, 17 hours).

Lead costs about $1.70 per kg, so the system would contain about $155,000 worth of lead. That works out at around $3100/kWh, just for the lead. Lithium ion batteries are hovering at about $200 per kWh at the moment. Dinorwig power station in Wales can store about 9GWh of energy, and cost £425m to construct in 1984 (about £4 billion in today's money, $5.2 billion). This works out at about $600/kWh (but with a significantly longer lifespan than a typical lithium battery)

The reason water works so well is because it is essentially free, and it's easy to work with. The technology scales very well too if you have somewhere with the right topography, it's relatively easy to make a container that can hold a huge amount of water for a relatively tiny pump and generating station. It's a lot harder to do the same with lead, or rail cars, or whatever, because it's a lot more expensive to increase the mass you have to play around with.

 

When we solve the problem of operating them long-term. Molten salt gives material scientists nightmares!

I went with lead cause it's dense, but sand could also work and that's nice and cheap. And dont forget, Li systems dont recharge infinitely, while a lead ball will be a lead ball forever if you keep it oiled. 

The advantage over water is you get a denser system that is simpler to assemble and maintain vs hydro. Let's say you quarry out a big ditch and use the bulk of that material to also make a big ramp and the rest as material for your carts. So far you're at zero materials cost.  You can set up a system that only requires a track and the generators instead of two large reservoirs and the pumps. If there's some natural terrain to take advantage of all the better, and all you need is a steep hill. Heck, you can go mountain scale which is infeasible for water based systems due to freezing. 

[cantab]

Dinorwig Power Station in Wales and Cruachan Power Station in Scotland both store about 10 million tonnes of water in their upper reservoirs. (And by the way both are in mountainous areas). That's an equivalent weight to fifty thousand heavily-loaded freight wagons. A moving vehicle system is not anywhere near as scalable as the established pumped storage systems.

As far as output goes, Dinorwig will do 1650 MW and maintain that for six hours. Cruachan's turbines max out at 440 MW but it has the water for 22 hours of running. A railcar or similar regeneratively braking is going to make just a few megawatts, and is going to descend any reasonable slope pretty quickly.

[shynung]

5 hours ago, PB666 said:

Diborane is actually a gas that can be used as a fuel, its very unstable though, more so than hydrazine.

https://en.wikipedia.org/wiki/Diborane

And you need an oxidizer. ISP is pretty decent given the mass, and you don't need an igniter, its does that all by itself in the presence of a trace of water.

Diborane is nearly useless as far as rocket propellants go. Not only it doesn't release much energy on combustion, it deposits boron trioxide (B2O3) on pretty much any cool surface.

[todofwar]

47 minutes ago, cantab said:

Dinorwig Power Station in Wales and Cruachan Power Station in Scotland both store about 10 million tonnes of water in their upper reservoirs. (And by the way both are in mountainous areas). That's an equivalent weight to fifty thousand heavily-loaded freight wagons. A moving vehicle system is not anywhere near as scalable as the established pumped storage systems.

As far as output goes, Dinorwig will do 1650 MW and maintain that for six hours. Cruachan's turbines max out at 440 MW but it has the water for 22 hours of running. A railcar or similar regeneratively braking is going to make just a few megawatts, and is going to descend any reasonable slope pretty quickly.

Still, as you or someone else said, you need those reservoirs. What about somewhere like Norway? Rugged terrain, not allot of lakes, need to damn off or otherwise ruin large chunks of the landscape, and half the year your reservoir will be frozen. Or a desert, where water is a bit more precious than sand. Where you have the landscape to set up reservoirs they are the better option. But the railcar system is deployable anywhere. 

[peadar1987]

8 hours ago, todofwar said:

Still, as you or someone else said, you need those reservoirs. What about somewhere like Norway? Rugged terrain, not allot of lakes, need to damn off or otherwise ruin large chunks of the landscape, and half the year your reservoir will be frozen. Or a desert, where water is a bit more precious than sand. Where you have the landscape to set up reservoirs they are the better option. But the railcar system is deployable anywhere. 

Reservoirs tend not to freeze solid. Ice is a good insulator, and it floats, so you'll get a thick layer on top of your lake, but you'll still have the majority of it existing as a liquid beneath that layer. The solution is just to put your intake deep enough in the reservoir.

For areas where the topography is bad, or water isn't available, compressed air storage still probably comes out as a more economical way of doing things, at around $1500/kWh. A railcar-based system is going to be very hard to scale. I dug up some numbers on railway construction costs, and it looks like we're talking about a minimum of $10 million per km of line for large projects. Let's say $20 million/km, because that's what the Cairngorm funicular railway cost. Railway cars cost about $50,000 for a freight car The steepest funicular railways have gradients of about 45 degrees, so for every metre of ascent, you're going to need about 1.4 metres of railway. A railway car (4m*3m*20m) filled with sand would have a mass of about 640,000kg according to Wolfram Alpha.

If we look at a system that rises say 500m up a hill, the track is going to cost about $14 million. A car is going to cost a further $50,000. Let's assume whatever you fill the cars with is free. Generators are going to cost about $350,000 per MW (shameless plug of own journal article).

Pulling a car up to the top of that incline is going to store 3.14GJ (900 kWh). Assuming you want about the same discharge time as Dinorwig (about 4 hours), you're going to need a generation capacity of about 200 kW (okay, this is a lot smaller than I was expecting). That's another $70,000 per car in regenerative braking capacity. This is a massive fudge by the way, true regenerative braking is going to be much more expensive than a simple generator.

So each car is going to cost $120,000, which gives $133/kWh contribution from the cars.

Overall cost is now going to depend on how many cars you have on the track. If you have 10 cars, you split the cost of the railway 10 ways, so the contribution is another $1.4 million per car, or $1500/kWh.

That's a lower estimate for the cost, as I've left out a load of things like purchasing the land, grid connection, planning, tax, and R&D costs.

Where I could see this being actually viable is if you actually had a pre-constructed railway, maybe a mining railway or disused funicular. If you didn't actually have to construct the rails, you would absolutely slash your costs.

[todofwar]

http://www.gizmag.com/ares-rail-energy-storage/28395/

@peadar1987 decided to find the article on this, because I knew I didn't come up with it. Looks like they're actually building it in Nevada. I don't know about how they're getting around track costs, I only quickly skimmed the article and they claim cost savings so maybe they are using existing track. 

[peadar1987]

2 hours ago, todofwar said:

http://www.gizmag.com/ares-rail-energy-storage/28395/

@peadar1987 decided to find the article on this, because I knew I didn't come up with it. Looks like they're actually building it in Nevada. I don't know about how they're getting around track costs, I only quickly skimmed the article and they claim cost savings so maybe they are using existing track. 

That scheme cost $55 million, and can store 12.5GWh of energy, which works out at $3,418/MWh. (https://www.wired.com/2016/05/forget-elons-batteries-fix-grid-rock-filled-train-hill/)

Prices will probably come down with economies of scale, but I doubt by much, as railways are pretty mature technology, and the same economy of scale savings would also apply to any competitors. I still think compressed air is going to work out cheaper, but would be very happy to be proven wrong. Large scale, cheap energy storage is something we need badly.

We've got a new PhD student starting in my research group in October working on compressed natural gas energy storage (natural gas can be liquefied more easily than air, meaning you can save a lot on storage volume). It'll be interesting to see what he comes up with