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Incredible! They use a massive arc furnace (used for steel recycling) to recycle concrete. They suggest that solar power could power the arc furnaces, resulting
by dr_dshiv 2y ago
Incredible! They use a massive arc furnace (used for steel recycling) to recycle concrete. They suggest that solar power could power the arc furnaces, resulting in zero emission concrete. As concrete currently constitutes 7.5% of anthropogenic carbon emissions, this tech could make a big difference.
Arc furnaces are crazy energy intensive. But if solar power keeps doubling every 2 years, we will very soon have way more power than we know what to do with (at certain times in the day). Arc furnaces are a good way to suck up the negative electricity spot prices!
- tempestn 2y agoOften the problem with using excess solar capacity is that the capital cost of the thing that would use it (desalination plants are one example) is so great that it's not cost effective to leave them idle at other times of the day. Any idea whether that would be the case with these arc furnaces as well?
- ahi 2y agoIANAMetallurgist. Arc furnaces for steel making already rely on cheaper off peak power, so utilization is already a factor.
- s1artibartfast 2y agoI didn't think they varied their use pattern by time of day. They might rely on cheaper power to lower the average cost make financial sense, but that is a different than soley utilizing excess power. If they cant rationalize the opex running 8 hours a day, there is still a problem. My understanding is that many of these plants cant even shut down and be restarted.
- kragen 2y agothe normal kind of arc furnaces are shut down many times a day; it's a batch process, not a continuous one
- s1artibartfast 2y agoDo they operate 24/7? Even if it is batch process, going from 24 hours to 8 hours is like tripling plant cost vs productivity.
- kragen 2y agotripling capex vs. productivity, yes, but maybe if capex is small compared to opex, that's a worthwhile tradeoff. the one particular plant i was able to find the answer for does operate 24/7
- adgjlsfhk1 2y agodon't forget wind. there's lots of wind power and very low power consumption at night. it's probably more like 22 hours to 16
- bluGill 2y agoThey generally will run the cheapest electric rates. They commonly run only the overnight shift when electric is cheapest - it is worth paying the employees that extra money to work the overnight shift. They commonly shutdown the entire month of December for yearly maintenance - when Christmas lights add additional electric demand. They coordinate with the power company for other shutdowns.
- colechristensen 2y agoYou may be thinking of aluminum plants which can’t be shut down and restarted without significant damage, but they are indeed still throttled up and down. In that case it’s electrochemistry at high temperatures to strip the oxygen off of aluminum. If it gets cold the apparatus gets damaged, but it can be throttled down a significant percentage.
- kragen 2y agothank you, that is almost certainly what they were thinking of how much do they get throttled up and down, and how frequently? i'd like to read more about this
- avianlyric 2y agoArc furnaces tend to be first in line to voluntarily shutdown to deal with grid instability, or projected power shortages. Network operators will basically pay them equivalent amount of money as they would to buy electricity, if the furnace operator is happy to shutdown at a moment’s notice. After, to a power grid, removing large loads are functionally equivalent to adding additional generation. So if you’re operating an arc furnace, and can shutdown quickly (which arc furnaces can), then grid operators will pay you for privilege of being able to shut you down at moments notice, and then pay even more for the electricity you’re not consuming, if the grid is forced to call upon that additional “capacity” due other issues on grid. I’m not sure if arc furnaces today vary their usage in direct response to variable electricity prices through the day, rather than only acting as emergency ballast to be jettisoned in an emergency. But I would be very surprised if they didn’t, they’re a large enough load that they’ll have coordinate the usage with their local grid, and large enough that shifting the usage pattern to avoid high cost peaks would save them a very material amount of money.
- Gibbon1 2y agoThis is one of the reasons I believe 'base load' demand is more fungible than people assume. I think in California 6% of electricity demand is pumping water. I'm almost willing to go on record and say that's the California Aqueduct and the actual number is higher. Okay I'm going to look. https://www.ppic.org/publication/water-and-energy-in-california/ https://www.ppic.org/publication/water-and-energy-in-califor... > The water system uses approximately 20% of the state’s electricity and 30% of its natural gas for business and home use, according to data from 2001—accounting for more than 5% of California’s greenhouse gas emissions.
- samatman 2y agoDid you miss the stat directly underneath that? > Heating and other energy-intensive water uses in homes and businesses make up almost 90% of water-related energy use, while treatment, pumping, and conveyance of water and wastewater account for the rest. That's 2% for everything which isn't heating water. Pumping is some smaller fraction of that.
- abakker 2y agoyou are right. The thing that is interesting is that pumping loads overall take a lot of the grid's energy, it's just that most pumps are refrigeration loads, not water transport.
- avianlyric 2y agoGreat thing about heating water, is that it stays hot after you’ve heated it. Water heating is basically the poster child for “demand-response” technologies. You can easily heat your water a few hours earlier than normal with basically no consequences to the user. But you need to get reasonable smart about modelling people water usage, as people don’t tend forget or forgive a cold shower.
- practicemaths 2y agoWhat about tankless water heaters? You can eliminate greenhouse gas emissions for heating and be more efficient with energy usage overall.
- kragen 2y agoi didn't know what ahi said (that minimills already depend on cheap off-peak power) but intuitively i would expect an arc furnace to be pretty cheap compared to the power it uses; it's just a water-jacketed chamber lined with castable refractory with a lid with three big carbon electrodes lowered through it, and all of those are cheap materials and low-precision (tight tolerances won't withstand white-hot flaming steel for long). the machinery is large and heavy, but only in proportion to the volume of material it processes. the electrical energy consumption, on the other hand, is comparatively enormous (admittedly maybe the capex for running the power lines to the facility is significant, but in the same proportion to the cost of the energy used as running transmission lines anywhere else) there's a nice video illustrating the process at https://www.youtube.com/watch?v=T1CJ5NPW8MU https://www.youtube.com/watch?v=T1CJ5NPW8MU. don't be alarmed, the part that looks like a major industrial accident is just what happens normally when they turn it on. a more detailed documentary with explanations, though unfortunately of an atypically large arc furnace, is in https://www.youtube.com/watch?v=eZRuVEfxIVI https://www.youtube.com/watch?v=eZRuVEfxIVI in that particular case they say it runs 24/7
- UberFly 2y ago"the part that looks like a major industrial accident is just what happens normally when they turn it on" That was better than most fireworks displays. I checked the second video but don't understand the German explanation. Is that just the initial effects of the massive amounts of voltage?
- kragen 2y agoit's pretty moderate amounts of voltage actually, only about 300-900 volts, just a little higher than i plug my phone charger into. it's just massive amounts of current, resulting in massive amounts of heat, which sets fire to the impurities and/or boils them off. you need low voltage because the arcs are pretty low resistance, so getting the necessary power requires tens of thousands of amps, about the same as a lightning strike. an hour-long lightning strike (the power of a lightning strike is much higher than that of a steelmaking arc furnace because it has much higher voltage, possible because the conductive path through the plasma is kilometers long instead of centimeters long) youtube has automatically translated subtitles which worked pretty well here. the relevant yt-dlp flags are i think --write-sub --write-auto-sub --sub-lang en,es (season to taste) and then the j key in mpv cycles through the languages you chose. this is also possible from youtube's web ui but enormously more awkward
- roughly 2y agoThe desalination debate is always a little interesting for me - first, I’m curious what they’re pricing in as the lifetime of the plant, because I always hear the capital costs are too high, but that’s a function of total water produced, and second is that the demand for water is pretty friggin’ inelastic, and as a Californian, I’m pretty sure the supply is constrained. I’m convinced that at some point we’re going to be very, very sad that we talked ourselves out of building those plants.
- krallja 2y agoCall Mark Cuban, make the investments now!
- pjc50 2y agoCalifornia has plenty of water, it's just dedicated far too much of it to farming in what would naturally be arid areas. It would be politically impossible to make farmers pay the real price for desalinated water, so what might happen is retail customers have to pay the high price for desalinated water while the remaining ""free"" water is routed to agriculture.
- abdullahkhalids 2y agoThe important thing here is that it only recycles concrete. Most of the 7.5% emissions are from new concrete constructions - new roads and new buildings - as we increase the total concrete in use. Very little is from old buildings/roads being destroyed and then replaced by something else. This will make a small dent in the 7.5% at scale.
- marcosdumay 2y agoOnce you solve energy producing and handling, 100% of the remaining is composed of tiny little problems. This one is large enough for several companies to make a living. What means it's large enough to care about.
- s1artibartfast 2y agoI dont understand your point. Are you saying there isnt enough recyclable concrete to meet the demand for new construction? If we create half as much concrete waste as demand, that 7.5% could drop by half.
- trimethylpurine 2y agoHome Depot seems to suggest that old concrete is already in high demand. If we need it for roads and we can't get it because concrete is more valuable, now we have to go find road building materials. Is the manufacture of road building materials cleaner than concrete? https://www.homedepot.com/c/ah/how-to-dispose-of-concrete/9ba683603be9fa5395fab90139b31d64 https://www.homedepot.com/c/ah/how-to-dispose-of-concrete/9b...
- s1artibartfast 2y agoI dont think that suggests there is a high demand for used concrete. It does however highlight the fact that there may be insurmountable transportation and handling costs for recycled concrete. It is hard to imagine it being cost effective to transport it to recycling centers.
- 3abiton 2y agoWhat's the catch
- mechhacker 2y agoNuclear has a large heat source (or can make a large heat source instead of converting to electric first) to do a lot of things like this.
- Animats 2y agoNope. Nuclear isn't hot enough. Only about 315°C at the output end. Electricity, though, has no thermodynamic upper limit on what temperature can be generated.
- Dylan16807 2y agoThat's not a thermodynamic limit, that's a design limit for light water reactors. Molten salt reactors are generally around 700C but they can go hotter.
- Animats 2y agoSteelmaking takes place around 1650C. Getting up to molten steel temperatures is hard. Yes, you could potentially use waste heat from a reactor to preheat the tundish, and maybe the scrap and ladle. Nucor preheats using natural gas to save on electricity. No need to bring everything up from room temperature on electric power. A nuclear reactor immediately adjacent to a steel caster is probably not a great idea.
- bruckie 2y agoIs there a cost effective way to move that heat to where it could be used? Nuclear reactors can produce very high temperatures, but in most reactors the heat is moved to turbines using water. Are there ways to move the heat at the high temperatures required to melt steel? (AFAIK, even molten salt is too cold.)
- vilhelm_s 2y agoPeople have been talking about this since at least the 1970s, but no existing reactors have high enough temperatures. There are various concepts on paper that could do it. https://world-nuclear.org/Information-Library/Non-power-nuclear-applications/Industry/Nuclear-Process-Heat-for-Industry https://world-nuclear.org/Information-Library/Non-power-nucl...
- seventyone 2y agoHow does this address the emissions of concrete's curing process? There's no way you can have "zero emission concrete". I've seen proposed additives that will reduce the emissions during the curing process but that chemical reaction is going to have to happen regardless.
- bobfromhuddle 2y agoConcrete absorbs co2 while curing. It's the calcination process, where we heat limestone up until the co2 burns off, that has unavoidable emissions. Since this concrete is recycled, that's already happened.
- kragen 2y agosee https://news.ycombinator.com/item?id=40461810 https://news.ycombinator.com/item?id=40461810 for a correction
- meindnoch 2y agoWhat are you even talking about? CO2 is absorbed during curing.
- logtempo 2y agoIt's math time, let's look what wikipedia say about electric arc furnace: - 1.44 gigajoules (0.4MWh) is required for 1 ton of steel. In theory. - 300T of steel needs 132 MWh, and a "power-on time" (the time that steel is being melted with an arc) of approximately 37 minutes. ---- wikipedia end ----- From https://ourworldindata.org/grapher/electricity-prod-source-stacked https://ourworldindata.org/grapher/electricity-prod-source-s...: total world electricity from renewable was 10,700TWh in 2021. 11,600 TWh in 2023. 1.5 billions (metric) tons of crude steel were produced in 2023. 30% of it by electric power. ------------------------ (A) Let's assume that 20% of those 30% already come from renewable (which is not the case, anyway). 30x20% is 6%. It means 24% of the 1.5 billions tons are looking for renewable. It means 360 millions of tons needs its green energy. It means we need to find 360 millions x 0.4MWh = 144 TWh. If we don't assume (A), we get 152 TWh. It means we need to dedicate ~1.5% of renewable worldwide energy to replace 24% of crude steel "e-production". In theory... We observed +5% of renewable energy production worldwide. If we wanted to make the steel *production* go green (1.5*3.33 = 5%), in theory it could be possible in one year...in theory. Tbh, I expected a more crazy conclusion. I'm quite sure the number is off by more than 10% though. But even if it was off by 100%, it would mean it's possible in 2 years. On a side note: it's useless anyway if those 5% are not coming with a decrease of 5% of coil&gas consumption. Which is not what's happening... Feel free to redo the math, I can make a mistake!
- dr_dshiv 2y ago> We observed +5% of renewable energy production worldwide “The amount of renewable energy capacity added to energy systems around the world grew by 50% in 2023, reaching almost 510 gigawatts (GW), with solar PV accounting for three-quarters of additions worldwide, according to Renewables 2023” https://www.iea.org/news/massive-expansion-of-renewable-power-opens-door-to-achieving-global-tripling-goal-set-at-cop28 https://www.iea.org/news/massive-expansion-of-renewable-powe...
- XorNot 2y agoA sector can grow by 50% and still be a small fraction of the overall mix. This is in fact the common problem with growth figures: going from 0 to 1 unit is literally infinity % growth, going from 1 to 2 at the same rate is 100%, but 1 to 3 is now only 50% etc... But you've also got the problem that capacity versus production is important to renewable energy in a way which doesn't apply the same to fossil fuels. Build a 1GW thermal power plant, you'll get about 0.8GW across the year. Build a 1GW solar plant, you'll get 0.1 - 0.25 GW across the year. But in terms of capacity you theoretically have 1GW, and at times on any given day, will.
- Hooray_Darakian 2y ago> But if solar power keeps doubling every 2 years, we will very soon have way more power than we know what to do with How soon is soon to you? https://www.eia.gov/todayinenergy/detail.php?id=50357 https://www.eia.gov/todayinenergy/detail.php?id=50357
- XorNot 2y agoAlso the problem that a sigmoid curve looks exponential if you only observe a small part of it[1]. [1] https://www.researchgate.net/figure/Successive-S-curves-in-technological-development-The-dotted-line-shows-the-overall_fig2_340525808 https://www.researchgate.net/figure/Successive-S-curves-in-t...
- dr_dshiv 2y agoAll material exponential curves are sigmoids, no? It’s a question of when things stop accelerating.
- XorNot 2y agoOf course, but in cases where there's a defined endpoint we also know that the decay from the exponential looking phase is going to happen well before we get there. i.e. the solar industry won't start installing solar panels at an ever higher rate if the amount of solar penetration is almost 100%. In fact the relative value of installing panels will decline as we get nearer to it. Arguably that's already happened - i.e. power prices going negative scrapes a lot of the shine off private industry funding them. Versus say, a natural process where while this might happen, the bounds aren't limited by humans making economic decisions for themselves (which of course, when you think about it also implies dangers in extrapolating effects of natural processes like climate change - the rate of some downstream parameter going up and looking linear and shallow could just be a very large system in the middle of moving into an exponential phase which extends well beyond our ability to manage it).
- kragen 2y ago
- bufferoverflow 2y ago> we will very soon have way more power than we know what to do with Only short term. Humans quickly find ways to use power. There are so many energy-intensive tasks, humankind will not have enough power for a long time. You can desalinate water or mine crypto. And if we have robots that are comparable to human capability, you can just scale production of everything endlessly.
- quaintdev 2y agoWhat if we are successful with Nuclear Fusion?
- hackerlight 2y agoImpact would depend on cost per kWh of the fusion energy
- prawn 2y agoI imagine we'll be air conditioning bigger spaces and more liberally, in a lot of places.
- doikor 2y agoArc furnaces are also expensive so realistically you want to have one running as close to 24/7 as possible.
- chakintosh 2y ago> we will very soon have way more power than we know what to do with https://english.aaj.tv/news/330362080/germanys-solar-boom-leads-to-negative-energy-prices https://english.aaj.tv/news/330362080/germanys-solar-boom-le...
- CatWChainsaw 2y agoJevons Paradox will take care of any surplus created.