12 ms·

Huh, I'm less doubtful of this than I thought I'd be. Tower cranes are apparently surprisingly low-maintenance. I assume this is because they have to actively p

by saulrh 8y ago

Huh, I'm less doubtful of this than I thought I'd be. Tower cranes are apparently surprisingly low-maintenance. I assume this is because they have to actively participate in their own disassembly [1] and major breakages are super difficult to deal with because they're at altitude, so they need to operate reliably enough that they can always take themselves down at the end of a job or if they need a major repair (cracks found in main pivot ring, etc). Concretely (pun not intended), I found a document [2] saying that 10 tradesmen and $35k/month in parts (together a bit more than $1m/year) can keep a fleet of 70 tower cranes (15 metric ton lift capacity each) at ~80% utilization over a one-year period. So, yeah, I'd definitely believe that you could run these things at the quoted price. 1: https://www.youtube.com/watch?v=Nww6MN_Lxeo&t=24s https://www.youtube.com/watch?v=Nww6MN_Lxeo&t=24s 2: Annex 9, "Example of the Use of Key Performance Indicators for Maintenance", in this PDF: https://www.mantiscranes.ie/wp-content/uploads/2017/01/CPA-TCIG-0801-Maintenance-Inspection-and-Thorough-Examination-of-Tower-Cranes.pdf https://www.mantiscranes.ie/wp-content/uploads/2017/01/CPA-T...

nabla9 8y ago
The selling point of this is low relatively low capital cost and well tested technology. Power density is not that good, but if you have land that's not a problem. The use of space to store energy is maybe double of what typical damn reservoir uses to store the same amount of energy.
- acidburnNSA 8y ago
  Reservoirs have a tendency to emit biogenic methane though so they're not great at scale for climate change mitigation.
  - your-nanny 8y ago
    I'm assuming this is because of growth and decay between fill and release cycles. But in the long run wouldn't that be carbon neutral?
    - acidburnNSA 8y ago
      Not a true expert on the topic but from my reading it sounds like land is generally a carbon sink and water produces carbon so when you turn land into water, the net effect is additional carbon. Estimates have man-made reservoirs accounting for 0.5% of the total anthropogenic carbon emissions worldwide; fairly significant when we're considering the scale needed for energy storage with wind (blows 35% of the time, US avg.) and solar (shines 25% of the time, US avg.). http://documents.worldbank.org/curated/en/739881515751628436/pdf/122610-WP-PUBLIC-WFinalApplicationFilesWeBookW.pdf http://documents.worldbank.org/curated/en/739881515751628436...
    - strommen 8y ago
      It's carbon neutral when plants decay to carbon dioxide. But they need oxygen for this to happen - and when they don't (like when they're underwater), they decay to methane. And methane is a greenhouse gas 20-80x more potent than carbon dioxide.
  - tonfa 8y ago
    Isn't making concrete a large emitter of co2 as well?
    - akshatrathi 8y ago
      yep, hence the use of waste material wherever possible.
      - Gravityloss 8y ago
        Probably you could throw in a small amount of nanocellulose and it could improve the strength a lot. Especially tensile strength, which is not good for concrete.
    - onetimemanytime 8y ago
      they could make steel cages, fill them with crushed and vibrated limestone (or another aggregate). Good steel for the cage would last a lifetime but not sure if it's cheaper in $$ or CO2 emissions. Basically they need to lift /drop a heavy thing that last generations and stacks well. Concrete has the advantage of lasting "forever" in those conditions (rebar when wet ruins it, otherwise it last long, long time). Concrete also stacks perfectly as you can mold it however you want. Might bite the bullet and stick with concrete, just work on making it more efficient.
- ComputerGuru 8y ago
  Reservoirs are restricted in where they can be built, because water. And that real estate is in high demand for many other uses. I think it's a safe assumption that, in general, coastal properties (including those on lakes and rivers) are more than twice as valuable as inland property on average.
  - smolder 8y ago
    Reservoirs could probably be built underground. I could also see one of these block stackers existing in the sublevels of a big skyscraper. Cost and and difficulty of access for maintenance might make either thing impractical, though.
- michaelchisari 8y ago
  Each 35MWh system requires about 1.62 acres of land. That seems perfectly reasonable to me, especially since there are still optimizations to explore. Here's some totally useless back-of-the-envelope calculations on land requirements for this sytem. The United States, in total, used 1,819,393,805 MWh of energy in 2016. If one plant provides 35MWh of storage, that means 51,982,680 plants are required. That comes to 84,211,942 acres of land. There are 2.3 billion acres of land in the United States, so it would require 3.66% of the US. That's obviously a huge overestimate. The beauty of this is the simplicity. This is something we could have built 40 years ago. And unlike LIBs, there's much less worry about degradation and we can put these out in the desert near a solar power source without worry. Imagine it combined with solar thermal, which has dropped immensely in price per KWh. Also, concrete reabsorbs around 43% of the co2 used to create it over a period of time. https://www.nature.com/articles/ngeo2840.epdf https://www.nature.com/articles/ngeo2840.epdf
  - hawkice 8y ago
    In this hypothetical, you also need something like ten percent of Americans to be crane maintenance workers, wouldn't you? Based on the crane numbers above it might even be more.
    - rattray 8y ago
      If anything, that's a plus. But they'd probably be mechanized before long.
      - hawkice 8y ago
        >> ten percent of Americans to be crane maintenance workers > If anything, that's a plus. That's the world you want to live in, where there are more construction crane maintenance workers than teachers, police officer, food service workers, lawyers and doctors combined and then tripled? Is there no possible better use for human potential that fixing machines that lift bricks?
        8y ago
- xg15 8y ago
  < The selling point of this is low relatively low capital cost and well tested technology. I'm sceptical of that. As the sibling comment noted, the technology is well-tested, yes but for a completely different usage pattern. You don't know how reliably construction cranes are in lifting heavy loads in back-to-back cycles, 24/7. Additionally, I'd guess you will have to modify the cranes to realize the "recover energy" parts. I'm no expert, but I could imagine, traditional parts spend energy for both raising and lowering a weight because the design goal is reliable control of the load, not making energy. So you'd probably have to modify the motor assembly.
  - camtarn 8y ago
    I've recently started working with wave and tidal energy projects. From what I've been told, the magic isn't in the generators (almost every project I'm working on is just using a standard industrial motor as a generator) but in the smart regenerative drives which both supply and harvest power from them. Harvesting power from industrial processes to keep costs down seems like it's a very common thing to do, so these drives are available off the shelf, and are designed to plug into a variety of existing motors.
hliyan 8y ago
Question: can't we significantly reduce the number of moving parts by using a lever system to raise a single, giant weight, preferably from the bottom?
- deleted 8y ago
  [deleted]
- gonvaled 8y ago
  You can not use standard cranes, and there are obvious limits: motor power, cable strength, stability of the system with a high center of gravity, ...
  - hliyan 8y ago
    Could we not do this with a medium powered motor on the ground, pushing up the load through a system of gears and levers?
- Gravityloss 8y ago
  There was a project to carve a huge cylinder, kilometers wide, out of bedrock and raise and lower it with hydraulics. You could keep whatever's on top mostly intact. I don't know what's the latest status.
  - markvdb 8y ago
    http://www.authorstream.com/Presentation/heindl-958931-hydraulic-energy-store-system/ http://www.authorstream.com/Presentation/heindl-958931-hydra...
coolso 8y ago
> Concretely (pun not intended), I found a document [2] saying That's definitely a really awkward choice of word in that context for it not to be intended, so I'm thinking pun was, in fact, intended. You can try to convince me otherwise but in order to do so I'll need to see some concrete evidence (pun not intended)
- morog 8y ago
  Not sure why the downvotes, I thought the exact same thing
- saulrh 8y ago
  Not sure why you're being downvoted, it's a fair question. Maybe your post reads a bit abrasively? ¯\_(ツ)_/¯ Anyway, I really didn't intend the pun! My reaction to the article was to try to get a rough estimate of how reliable tower cranes are, at which point I realized that they must be very reliable to work at all. But I only had that broad hypothesis of "very reliable", so I went looking for evidence to confirm it, and if so, what that broad hypothesis ended up looking like in practice. For whatever reason I found "concretely" when I went looking for a word for the segue. Probably concrete on the brain and a bit of luck.
- bakhy 8y ago
  "Pun not intended" should definitely be among the top 10 most common lies, along with the likes of "I'm starting tomorrow", or "I'll pay you back" ;)
jaclaz 8y ago
That kind of cranes is very reliable, but in the real world they are used maybe 10% of their capacity [1]. In a normal building site they either do very few cycles per hour (at heavy loads) or a decent number of cycles per hour at a tiny fraction of their load capacity. Even when you use them intensively (with concrete buckets) to lift/pour concrete, that happens for a relatively short time (a few hours) each day. A typical cycle is 5-10 minutes and you don't actually have 12 or 6 of them per hour, each hour in a normal 8 hour shift and - with some exceptions you normally have 1 shift per day, 5/7 (it is rare that a site working with cranes operates 24/7). Besides, in a building site you don't work when it rains, and you cannot work with cranes if there is a not-so-strong wind blowing (for safety reasons). [1] no reference, you will need to trust my word for it, coming from some 30+ years experience in building sites
- saulrh 8y ago
  No need for a reference; now that you mention it it's obvious that the duty cycle will be totally different. In fact, I'd bet that cycle time is the limiting factor - the graphic [1] shows about 100 cylindrers per layer, 18 layers already stacked, and the system looks to be around 60% loaded, so total count could be around 3k cylinders to move for a full load. Six arms, then each is doing 1000 cycles a day. Assume 4 hours down a day, 20 hours up, 50 cycles an hour, a bit less than a cycle a minute. Yikes. I did notice that the cylinders were around twice the quoted capacities for tower cranes I was finding. It also sounds like they're building a much more expensive crane; that many cylinders, at 35 metric tons per and $90 for a yard of concrete, is upwards of $5m, and the article says that the concrete "could" be the most expensive part. Aaaaand random googling is giving me price tags for tower cranes that can't possibly be right - <$300k?! So the quoted system might be using a crane that's ten times the cost of a "normal" tower crane? I can... sort of seeing that buy a six-armed crane with twice the lift capacity but permanent construction, no need for a counterweight assembly, and better continuous performance. But now I feel like these numbers are lining up too well and I have to have done something wrong. 1. https://cms.qz.com/wp-content/uploads/2018/08/energy-vault-landscape_colorcorrected.jpeg https://cms.qz.com/wp-content/uploads/2018/08/energy-vault-l... 2. http://www.wolframalpha.com/input/?i=3000+*+($90+%2F+cubic+yard)+*+(35+metric+tons+%2F+(2400+kg+per+cubic+meter) http://www.wolframalpha.com/input/?i=3000+*+($90+%2F+cubic+y...)

by saulrh 8y ago

nabla9 8y ago

The selling point of this is low relatively low capital cost and well tested technology. Power density is not that good, but if you have land that's not a problem. The use of space to store energy is maybe double of what typical damn reservoir uses to store the same amount of energy.

acidburnNSA 8y ago
Reservoirs have a tendency to emit biogenic methane though so they're not great at scale for climate change mitigation.
- your-nanny 8y ago
  I'm assuming this is because of growth and decay between fill and release cycles. But in the long run wouldn't that be carbon neutral?
  - acidburnNSA 8y ago
    Not a true expert on the topic but from my reading it sounds like land is generally a carbon sink and water produces carbon so when you turn land into water, the net effect is additional carbon. Estimates have man-made reservoirs accounting for 0.5% of the total anthropogenic carbon emissions worldwide; fairly significant when we're considering the scale needed for energy storage with wind (blows 35% of the time, US avg.) and solar (shines 25% of the time, US avg.). http://documents.worldbank.org/curated/en/739881515751628436/pdf/122610-WP-PUBLIC-WFinalApplicationFilesWeBookW.pdf http://documents.worldbank.org/curated/en/739881515751628436...
  - strommen 8y ago
    It's carbon neutral when plants decay to carbon dioxide. But they need oxygen for this to happen - and when they don't (like when they're underwater), they decay to methane. And methane is a greenhouse gas 20-80x more potent than carbon dioxide.
- tonfa 8y ago
  Isn't making concrete a large emitter of co2 as well?
  - akshatrathi 8y ago
    yep, hence the use of waste material wherever possible.
    - Gravityloss 8y ago
      Probably you could throw in a small amount of nanocellulose and it could improve the strength a lot. Especially tensile strength, which is not good for concrete.
  - onetimemanytime 8y ago
    they could make steel cages, fill them with crushed and vibrated limestone (or another aggregate). Good steel for the cage would last a lifetime but not sure if it's cheaper in $$ or CO2 emissions. Basically they need to lift /drop a heavy thing that last generations and stacks well. Concrete has the advantage of lasting "forever" in those conditions (rebar when wet ruins it, otherwise it last long, long time). Concrete also stacks perfectly as you can mold it however you want. Might bite the bullet and stick with concrete, just work on making it more efficient.
ComputerGuru 8y ago
Reservoirs are restricted in where they can be built, because water. And that real estate is in high demand for many other uses. I think it's a safe assumption that, in general, coastal properties (including those on lakes and rivers) are more than twice as valuable as inland property on average.
- smolder 8y ago
  Reservoirs could probably be built underground. I could also see one of these block stackers existing in the sublevels of a big skyscraper. Cost and and difficulty of access for maintenance might make either thing impractical, though.
michaelchisari 8y ago
Each 35MWh system requires about 1.62 acres of land. That seems perfectly reasonable to me, especially since there are still optimizations to explore. Here's some totally useless back-of-the-envelope calculations on land requirements for this sytem. The United States, in total, used 1,819,393,805 MWh of energy in 2016. If one plant provides 35MWh of storage, that means 51,982,680 plants are required. That comes to 84,211,942 acres of land. There are 2.3 billion acres of land in the United States, so it would require 3.66% of the US. That's obviously a huge overestimate. The beauty of this is the simplicity. This is something we could have built 40 years ago. And unlike LIBs, there's much less worry about degradation and we can put these out in the desert near a solar power source without worry. Imagine it combined with solar thermal, which has dropped immensely in price per KWh. Also, concrete reabsorbs around 43% of the co2 used to create it over a period of time. https://www.nature.com/articles/ngeo2840.epdf https://www.nature.com/articles/ngeo2840.epdf
- hawkice 8y ago
  In this hypothetical, you also need something like ten percent of Americans to be crane maintenance workers, wouldn't you? Based on the crane numbers above it might even be more.
  - rattray 8y ago
    If anything, that's a plus. But they'd probably be mechanized before long.
    - hawkice 8y ago
      >> ten percent of Americans to be crane maintenance workers > If anything, that's a plus. That's the world you want to live in, where there are more construction crane maintenance workers than teachers, police officer, food service workers, lawyers and doctors combined and then tripled? Is there no possible better use for human potential that fixing machines that lift bricks?
      - 8y ago
xg15 8y ago
< The selling point of this is low relatively low capital cost and well tested technology. I'm sceptical of that. As the sibling comment noted, the technology is well-tested, yes but for a completely different usage pattern. You don't know how reliably construction cranes are in lifting heavy loads in back-to-back cycles, 24/7. Additionally, I'd guess you will have to modify the cranes to realize the "recover energy" parts. I'm no expert, but I could imagine, traditional parts spend energy for both raising and lowering a weight because the design goal is reliable control of the load, not making energy. So you'd probably have to modify the motor assembly.
- camtarn 8y ago
  I've recently started working with wave and tidal energy projects. From what I've been told, the magic isn't in the generators (almost every project I'm working on is just using a standard industrial motor as a generator) but in the smart regenerative drives which both supply and harvest power from them. Harvesting power from industrial processes to keep costs down seems like it's a very common thing to do, so these drives are available off the shelf, and are designed to plug into a variety of existing motors.

hliyan 8y ago

Question: can't we significantly reduce the number of moving parts by using a lever system to raise a single, giant weight, preferably from the bottom?

deleted 8y ago
[deleted]
gonvaled 8y ago
You can not use standard cranes, and there are obvious limits: motor power, cable strength, stability of the system with a high center of gravity, ...
- hliyan 8y ago
  Could we not do this with a medium powered motor on the ground, pushing up the load through a system of gears and levers?
Gravityloss 8y ago
There was a project to carve a huge cylinder, kilometers wide, out of bedrock and raise and lower it with hydraulics. You could keep whatever's on top mostly intact. I don't know what's the latest status.
- markvdb 8y ago
  http://www.authorstream.com/Presentation/heindl-958931-hydraulic-energy-store-system/ http://www.authorstream.com/Presentation/heindl-958931-hydra...

coolso 8y ago

> Concretely (pun not intended), I found a document [2] saying That's definitely a really awkward choice of word in that context for it not to be intended, so I'm thinking pun was, in fact, intended. You can try to convince me otherwise but in order to do so I'll need to see some concrete evidence (pun not intended)

morog 8y ago
Not sure why the downvotes, I thought the exact same thing
saulrh 8y ago
Not sure why you're being downvoted, it's a fair question. Maybe your post reads a bit abrasively? ¯\_(ツ)_/¯ Anyway, I really didn't intend the pun! My reaction to the article was to try to get a rough estimate of how reliable tower cranes are, at which point I realized that they must be very reliable to work at all. But I only had that broad hypothesis of "very reliable", so I went looking for evidence to confirm it, and if so, what that broad hypothesis ended up looking like in practice. For whatever reason I found "concretely" when I went looking for a word for the segue. Probably concrete on the brain and a bit of luck.
bakhy 8y ago
"Pun not intended" should definitely be among the top 10 most common lies, along with the likes of "I'm starting tomorrow", or "I'll pay you back" ;)

jaclaz 8y ago

That kind of cranes is very reliable, but in the real world they are used maybe 10% of their capacity [1]. In a normal building site they either do very few cycles per hour (at heavy loads) or a decent number of cycles per hour at a tiny fraction of their load capacity. Even when you use them intensively (with concrete buckets) to lift/pour concrete, that happens for a relatively short time (a few hours) each day. A typical cycle is 5-10 minutes and you don't actually have 12 or 6 of them per hour, each hour in a normal 8 hour shift and - with some exceptions you normally have 1 shift per day, 5/7 (it is rare that a site working with cranes operates 24/7). Besides, in a building site you don't work when it rains, and you cannot work with cranes if there is a not-so-strong wind blowing (for safety reasons). [1] no reference, you will need to trust my word for it, coming from some 30+ years experience in building sites

saulrh 8y ago
No need for a reference; now that you mention it it's obvious that the duty cycle will be totally different. In fact, I'd bet that cycle time is the limiting factor - the graphic [1] shows about 100 cylindrers per layer, 18 layers already stacked, and the system looks to be around 60% loaded, so total count could be around 3k cylinders to move for a full load. Six arms, then each is doing 1000 cycles a day. Assume 4 hours down a day, 20 hours up, 50 cycles an hour, a bit less than a cycle a minute. Yikes. I did notice that the cylinders were around twice the quoted capacities for tower cranes I was finding. It also sounds like they're building a much more expensive crane; that many cylinders, at 35 metric tons per and $90 for a yard of concrete, is upwards of $5m, and the article says that the concrete "could" be the most expensive part. Aaaaand random googling is giving me price tags for tower cranes that can't possibly be right - <$300k?! So the quoted system might be using a crane that's ten times the cost of a "normal" tower crane? I can... sort of seeing that buy a six-armed crane with twice the lift capacity but permanent construction, no need for a counterweight assembly, and better continuous performance. But now I feel like these numbers are lining up too well and I have to have done something wrong. 1. https://cms.qz.com/wp-content/uploads/2018/08/energy-vault-landscape_colorcorrected.jpeg https://cms.qz.com/wp-content/uploads/2018/08/energy-vault-l... 2. http://www.wolframalpha.com/input/?i=3000+*+($90+%2F+cubic+yard)+*+(35+metric+tons+%2F+(2400+kg+per+cubic+meter) http://www.wolframalpha.com/input/?i=3000+*+($90+%2F+cubic+y...)