6 ms·
Often 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 tha
by tempestn 2y ago
Often 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.