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I'm extremely skeptical that ARES will ever be cost efficient. Potential energy is proportional to mass * g * d_height - any reasonable grid storage option will
by krapht 10y ago
I'm extremely skeptical that ARES will ever be cost efficient. Potential energy is proportional to mass * g * d_height - any reasonable grid storage option will need to be moving truly enormous amounts of mass.
Back of the napkin here:
California consumes 9.54 * 10^17 Joules of electricity / year, or 1.09 * 10^14 Joules / hour.
Suppose we wish to hold in storage enough energy to supply to grid for twelve hours, since the sun does not shine at night. Assume we have a 100% efficient method of recovering potential energy stored on a train. Suppose we find a suitable mountain with a 1000 meter height differential. Then according to e = mgh, we would need to shift a load of 1.33*10^11 kilograms to supply twelve hours of electrical demand.
Let's assume we use the cheapest rock we can to fill this mass. I assume you can get wholesale pea gravel for $8 a metric ton.
Then the cost of gravel alone is $1.07 billion.
That doesn't sound so bad, but remember, this project will need ~1333500 100-metric-ton freight cars. Suppose they cost $120,000 / ea. Then suddenly, the cost of the train cars is 160 billion.
This is on the order of magnitude of the entire California yearly state budget. And also ignoring a bunch of other cost factors that will increase the total price by another 1-2 orders of magnitude.
Pumped storage hydroelectric is viable precisely because the reservoir holds your water for essentially free. Train cars are far, far more expensive.
- giarc 10y agoTrue, but all your math assumes that energy is used equally all 24 hours of the day. A large chunk of energy is consumed during the day, when the sun is shinning. Much less is used at night when the trains need to supply energy.
- krapht 10y agoIf anything I think my estimate is too conservative. Electrical storage must be adequate to meet demand in the worst case. The minute somebody's grandmother freezes to death because of brownouts due to wintry, overcast skies in December, and there will be riots in the state legislature.
- sitkack 10y agoNo, we are long over designing systems for the worst case. This is what got us where we are today. The smart grid is about keeping grandmother alive tonight while drying your clothes during the light cycle tomorrow.
- imron 10y agoAnd pray that worst case scenarios don't happen.
- leereeves 10y agoMost people work during the light cycle. Would this smart grid require that people only ever wash clothes on days they don't work?
- jefurii 10y agoThe desire to be able to do whatever you what, when you want, is part of how we got to this climate-changing situation in the first place.
- mzw_mzw 10y agoGood luck winning elections with that.
- rjvs 10y agoYou can wash clothes while you're not there. It's even possible to schedule the washing so that it's done near the end of the light cycle so they don't sit in the machine for long after they are clean.
- Someone 10y agoOne could argue that, if people freeze to death because of brownouts due to wintry overcast skies in December (weeks of freezing weather probably would be something different), there's something wrong with the way houses are built. Getting rid of oil addiction doesn't solely mean replacing oil with wind and solar; it also means thinking rationally about why we need so much energy.
- beamatronic 10y ago>> the reservoir holds your water for essentially free Once you build a dam, that is.
- Gustomaximus 10y agoI suspect the whole 'needs a hill' and amount if land taken becomes a problem as this cant be taken for granted as available. There are other solutions that seem effective and take so much space. Maybe something like this? http://www.gravitybattery.info/ http://www.gravitybattery.info/
- BurningFrog 10y agoI don't know anything about freight car pricing, but these cars should be 1-3 orders of magnitude cheaper than regular high speed for expensive cargo. The ideal one is basically a rock with wheels.
- tonyedgecombe 10y agoThe Flintstones model of energy storage.
- jfoutz 10y agoThere is a very good chance i've screwed up my math, but my silly back of the envelope calculation says, 9.54 * 10^17 Joules/ (3.6 *10^9 Joules/mwh) = 265000000 mwh. Levelized cost, [1] (operating + construction + financing) works out to around $72 per mwh, over 30 years. (going with the cheapest average option) So if we were to throw away everything today, and be required start fresh, I get about $570 billion. That's clearly a stupid thing to do. However, my big point is, if solar falls another order of magnitude (which is a pretty big if), we can afford to spend a lot on storage. I think solar is now competitive with coal, but it's not dispatchable. I'd argue solar would probably need 4x the amount of production of a similar coal plant, it's only going to work really well part of the day, and there are losses in storage (ares claims 20% loss, which is comparable to batteries) there's not much weight difference between gravel and packed dirt. I figured they'd just use whatever mass is handy when they're building the track. I don't know if $120k is a fair price. the cars have to have regenerative breaks, which are likely expensive. Just building something strong enough to support 100 metric tons can't be cheap. I don't know if there are any special features of regular freight cars that can be abandoned to cut down costs. On the other hand, if you're building a million of them, the costs would likely come down a bit. Perhaps solar has reached the end, and any improvements will be slow. I don't believe that, and i do believe some sort of efficient storage will be the big focus in energy going forward. [1] https://en.wikipedia.org/wiki/Cost_of_electricity_by_source#United_States https://en.wikipedia.org/wiki/Cost_of_electricity_by_source#...
- joshkpeterson 10y agoFactor in the cost of society collapsing due to carbon driven climate change, and see where that gets you :)
- patall 10y agoIF solar falls another order of magnitude, it will be far cheaper (which only has the conversion efficiency problem) to go for power-to-gas technology that has the additional advantage of being able to use gas (not gasoline) powered cars with normal range.
- reitanqild 10y ago
- erispoe 10y agoYou would need a lot less rail cars than that. Rails cars move the weights between the low and the high point, but they are re-used multiple times in a cycle, going back and forth constantly. It wouldn't be very efficient to have a mobile piece of tech sitting idle for 99% of the time. The main constraint would be to make the maximum use of cheap technology that is standard today. 100t freight cars are pretty standard.
- adwn 10y agoEdit: nevermind, I was wrong
- stuckagain 10y agoThat's not how the proposal works. Each car picks up a box of rocks on a hydraulic jack and hauls it up the hill and then sets it down again and gets another one. Maybe the railcar makes 10 or 100 trips during the day.
- adwn 10y agoYes, you're both right. My fault – I misunderstood the ARES concept.
- usrusr 10y agoAll three of you are right: Ares advertises two different concepts, only the one they call "grid storage" uses more ballast than they can fit on their rolling stock. The one they call "ancillary services", intended only for short term grid regulation/stabilisation", uses fixed ballast that is never removed from the trains during regular operation. This is what the first prototype will be.
- stuckagain 10y agoEverybody wins!
- 10y ago
- fsloth 10y agoIt's not a forest of Sisyphean gravel funiculars which your calculation presumes. According to the brochure on the site the Ares system seems to be an automated freight yard on a slightly sloping ground. Only a fraction of the total mass is on wheels at a time. The scaling issues might be a bit different.
- martythemaniak 10y ago>It's not a forest of Sisyphean gravel funiculars I strongly feel this expression belongs somewhere. I just have no clue where.
- Intermernet 10y agoSong lyrics, or poetry. I personally like the idea of turning really deep mines into literal potential energy wells. Use renewable energy to lift loads (water, gravel etc) and then power generators at night by dropping the load back down. Basically enormous cuckoo clocks.
- xchaotic 10y agoWhile I like the idea for its steampunk appeal, looking at potential/kinetic energy delta, you have two ways really: build overcapacity for solar, immovable, uses rare earth minerals, but other than dust, maintenance free and then that capacity will sit idle at night or you build capacity like these lifts at that capacity is going to sit unusued during the day, but it does require a lot more maintenance due to moving parts and potentially more resource heavy to build, but no exotic materials. I think the best way forward is to, of course use the least amount of energy possible - insulate from both heat and cold, make efficient CPUs and run everything you can in software and anything physical make it run during the day on solar. Once environmental costs are accounted for, it makes no sense to run things like cars and shops and washing machines at night.
- ljnelson 10y agoPaul Simon song.
- WalterBright 10y ago> will need to be moving truly enormous amounts of mass. Use the extra energy to increase the spin of the earth, then harvest the spin to pull off energy.
- marvin 10y agoIf that was easy and cheap to do, our problem wouldn't be climate change due to greenhouse gases - it would be climate change due to the earth rotating slower since we'd been using it as an energy source for 200 years!
- adrianN 10y agoYou'd speed it back up in times of energy surplus. It's a giant flywheel.
- WalterBright 10y agoRotational energy is already harvested using tidal power and wind power.
- dghughes 10y agoThere are band type "windmills" it's a taught band with magnets on each end when it flaps it moves the magnets to generate power.
- wcoenen 10y agoThis is what every flywheel already does (unless it is balanced by a second flywheel going the other way). Conservation of angular momentum: as a flywheel gains angular momentum, it must be compensated by the Earth gaining the same amount of angular momentum in the opposite direction. Usually this isn't referred to as "spinning up the Earth" though :-)
- duaneb 10y agoActually you made it sound pretty attractive. It's only $160 billion (plus a few for yearly maintenance why not) to get California entirely on renewable energy. That's amazing and gives me hope.
- simonh 10y agoYou still need to generate the energy in the first place.
- PietdeVries 10y agoAnd now you do the same with pumping water back and forth... I get it that trains are handy when you have plenty of space and lack water, but many, many places around the globe lack the space for the hughe amounts of train tracks running up a 1000 meter high hill. In addition, take into account the enormous amount of moving parts. Maintenance everywhere! Compare the tracks with carts to a large pump/generator and pipelines with water I guess the latter is much simpler to maintain and better looking to the eye. While train tracks should be kept clear of people you could easily see people using the lakes up & down the mountain for recreation.
- ptero 10y agoAs others said, you can reuse cars (if a car does 100 1km journeys per charge interval the materials cost for cars and gravel become comparable) and a custom built car can be cheaper, too. The volume may be another challenge though: 1.33*10^11 kg is roughly 0.1 km^3 of gravel/dirt. So we need to move a cube of dirt ~450m in size up and down 1km each day. Not impossible, but presents bit challenges on its own imo.
- ChrisjayHenn 10y agoI would think the idea has merit if rather than purpose-built rails, the existing rail infrastructure is retrofitted (and built out) to act as a storage mechanism with freight that already has to move anyway. If that's done though, a proof of concept would need to be built first. So I wish these guys all the best, despite the fact that the economics look kind of silly on the surface.
- ChrisjayHenn 10y agoI would think the idea has merit if rather than purpose-built rails, the existing rail infrastructure is retrofitted (and built out) to act as a storage mechanism with freight that already has to move anyway. If that's done though, a proof of concept would need to be built first. So I wish these guys all the best, despite the fact that the economics look kind of silly on the surface.
- evgen 10y agoJust a few minor nits, you are off by a bit in your calculation of the cost of the train cars. A 5800CF open-topped hopper car will hold a little more than 200 metric tons of gravel and will cost less than 50K for the car and the gravel to fill it. Now you need 600000 cars at a cost of 50K each so the cost has dropped to around 33 billion. If you were buying rail cars at this sort of quantity you can probably also get a much better deal :) I also seriously doubt there are going to be cost factors that add one or two orders of magnitude to the price here, but it is possible. The rail itself is very cheap and land to site the project is similarly easy to find since the rail line does not actually need to go anywhere and you can run lines in parallel instead of needing a long distance. Definitely not cheap, but pumped hydro storage is in no way "free" and there are really no places you can do pumped hydro in any large scale that are not already used for existing dams and rivers. The lack of significant environmental impact is also a win for something like ARES.
- jsymolon 10y agoWhat's the maintenance cost of the lines and equipment vs the hydro ?
- evgen 10y agoProbably much much cheaper for rail lines. Rail doesn't leak. The entire infra is open to direct maintenance, and you can easily take segments of the system out of production for repair without having any significant impact on the productivity of the whole. You can extend or lay parallel track while your main system is still operational without too much bother so expansion is also easier.
- jartelt 10y agoI wouldn't be so quick to dismiss the maintenance cost for a ARES-type rail system. For pumped hydro, your ongoing maintenance is largely going to be maintaining a pumping system (to send water up) and a generator system. Hopefully you build your reservoir properly so that it lasts for 30 years. For rail, you have to have to maintain a large number of moving parts. It won't be cheap to insure all the parts are greased and good to go. I think it's a lot easier to maintain a set of pumps and generators than it is to maintain what is essentially a rail fleet filled with gravel on a mountain.
- gshubert17 10y agoContinuing the back of napkin calculations, to compare train cars with batteries: Rail cars costing $10^5 can hold 100 metric tons or 10^5 kg each. Cost is $1/kg. This will be amortized over the system's useful life. 1000 meter height differential at 10 m/sec^2 stores 10^4 J/kg. System stores about 10^4 J/$. Tesla's Powerwall stores 10 kWhr for $3500. That's about 10^4 J per $ (since an hour is 3600 seconds). What surprises me is that these order-of-magnitude costs are about the same -- 10^4 Joules per dollar.
- evgen 10y agoA 5800CF open-topped hopper can hold 200 metric tons of pea gravel (at least according to the people selling them) so you just doubled the J/$ of the Powerwall. This is also using new rail cars, if you buy used then the price for the same rail car drops down to the 20K range according to online rail car brokers. Now we are looking at 1/4 the price for a train car solution.
- mars4rp 10y agoCalifornia state budget is $167B.
- dannypgh 10y agoUnless the state budget pays for the entire energy industry, that seems like a curious comparison to make. You started with the total energy (I presume electrical) usage of the state. About how much do Californians pay for all that electricity per year?
- kalid 10y agoFriendly calculator if you want to play with the various assumptions: https://instacalc.com/50110 https://instacalc.com/50110
- mortehu 10y agoFor reference, 133,350,000 metric tons is 1.81x the mass capacity of the US strategic oil storage, another grand energy storage scheme. http://www.wolframalpha.com/input/?i=(133,350,000+metric+tons)+%2F+(727+million+barrels+*+850+kg%2Fm%5E3) http://www.wolframalpha.com/input/?i=(133,350,000+metric+ton...