128 replies
1d22h
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!
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?
IANAMetallurgist. Arc furnaces for steel making already rely on cheaper off peak power, so utilization is already a factor.
I 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.
Arc 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.
there's some footage in the documentary i linked of coordinating the usage with their local grid before turning the arc furnace off for half an hour (because the next load of scrap was delayed)
[deleted due to severely condescending comment below]
it's good that you're starting to learn some of the basics of how real-time energy markets work, but most of the things you have said are unfortunately nonsense
What an exceptionally unconstructive and condescending comment.
Deleting yours removes any hope of a conversation.
Didn't seem like there was much hope of that with the response I got anyway. I'm not here to take condescending comments with no substance (i.e. pointing out why it supposedly was nonsense), so I decided it was better to remove the comment and move on.
Okay but this way it's hard not to treat it as if you did in fact post nonsense.
And whether you said something right or wrong I at least would have liked to see it. Especially when it gets a callout like that.
All the more reason for me to stop engaging, isn't it?
The gist of it was that nuclear power is insufficient in and of itself because it is hard to regulate output to match grid requirements, and therefore that we need both nuclear and renewable energy sources, not just one or the other. Maybe I'm wrong, maybe I'm not, I'm out of here either way.
No, I don't think so. The skepticism all comes from your initial comment, not the followups.
Oh well that specific point is wrong. Modern nuclear can adjust its output quickly and within a wide range if the operator wants it to. We could run a 100% nuclear grid. The fundamental issue at hand is price, not capability, because reducing output makes the cost per watt go up.
also modern nuclear is probably too expensive to compete with batteries; steam turbines aren't getting cheaper fast enough, while both batteries and power semiconductors are improving at a staggering rate. there's no reason to expect that nuclear power will constitute any percentage of the power grid at all 20 or 40 years from now. 10 or 100 years from now, yes
if you want to read plausible misconceptions about electric grid operations and stability you can get gpt-4 to generate an unbounded stream of them
oddly enough, that's what i thought about your now-deleted misconception-filled comment, but i thought maybe it was worthwhile to try to engage positively
guess i failed at that
the normal kind of arc furnaces are shut down many times a day; it's a batch process, not a continuous one
Do they operate 24/7?
Even if it is batch process, going from 24 hours to 8 hours is like tripling plant cost vs productivity.
tripling 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
They 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.
don'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
You 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.
thank 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
This 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-califor...
Did you miss the stat directly underneath that?
That's 2% for everything which isn't heating water. Pumping is some smaller fraction of that.
Great 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.
What about tankless water heaters? You can eliminate greenhouse gas emissions for heating and be more efficient with energy usage overall.
tankless heaters use slightly less energy, but they use it in a really annoying way. the optimal design for a heavily renewable grid is a heat pump water heater with a tank
The optimal design for a heavily renewable grid is solar water heating a tank in home whenever the sun shines, falling back on a heat pump water heater with a tank.
That's only optimal if you know you'll need 100% of the heated water (or have a way to store it). While photovoltaics are going to be less efficient than direct water heating, you can direct the energy to other uses if you don't need more hot water.
Large tanks of water are about the cheapest way we know of to store energy. Batteries store more energy, but are extremely expensive.
Yes, but that only matters if we can easily consume that energy. If we need the hot water, then that's easy—no conversion loss. Otherwise, it gets trickier, especially in a small-scale setting like a home.
All homes use at least some hot water for showers. In many climates they can use a lot of energy for heating which means a very large tank could be useful in winter.
I read a study looking at the difference between tankless and tank water heaters.
Summary the more hot water you use the smaller the win is for tankless.
Other thing I've read and seems true is gas and heat pump water heaters cost about the same to run. I installed a heat pump unit five years ago. Works okay for two people. If you had three teenage girls and a wife that likes baths a tankless would be a better choice.
That's for maximizing energy efficiency. Tankless I think might be a tad bit more easier and cheaper to implement than this.
Regardless the point is eliminating the use of natural gas in heating water is itself a benefit.
you 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.
There's been other responses here pointing out that municipal water delivery pumping probably isn't a large electricity consumer, but it's also worth noting that even if it was you can't voluntarily shutdown water-delivery in large distribution systems - you have to maintain pressure and flow to prevent back contamination of the system from leaks. It's why you get boil-water advisories when there's a general outage - because dirt and bacteria can get back into the pipes and it takes time to be sure they've been flushed out of the system.
i 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. 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
in that particular case they say it runs 24/7
"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?
it'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
I see they use water to cool the actual furnace encasing. They then lead out the warm water to big basins to let the water cool off. It would be good if they could use that warm water for remote heating of houses or create electricity or something.
The 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.
California 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.
Call Mark Cuban, make the investments now!
It'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-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!
“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-powe...
A 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.
Wind and solar supplied 12% of global electricity in 2022 up from 10% in 2021 and things are still accelerating. You can’t keep this kind of growth rate up for long before things change. https://www.cnbc.com/2023/04/12/wind-and-solar-generated-a-r...
Your capacity factor numbers are also off ex: 29.7% capacity factor averaged over 3 years https://en.wikipedia.org/wiki/Mount_Signal_Solar.
Thermal is also much lower than your suggesting. China the world’s #1 coal consumer has capacity factors under 50% because they are using them for load following. France’s nuclear averaged ~70% for years for similar reasons. It’s only where the there’s excess natural gas and minimal solar/wind that thermal can keep high capacity factors but that’s becoming rare.
Grabbing one specific solar install and saying it's representative of all solar is absurd. If I take my rooftop solar in Sydney and generalize then I'd be saying it's 12.5%.
If I go by the CSIRO estimates[1] then that range is a reasonable middle for Australia (generally considered a sunny country) and would be optimistic for somewhere like Germany[2].
You're also misrepresenting capacity factors for thermal power plants: a thermal powerplant used to follow load operates below it's maximum capacity factor. Renewables can't follow load - capacity factor is the best they can do.
[1] https://www.csiro.au/en/research/technology-space/energy/Gen...
[2] https://en.wikipedia.org/wiki/Solar_power_in_Germany
I’m saying your range was incorrect and it only takes one example to show that. But here’s another 32.3% using single axes tracking: https://en.wikipedia.org/wiki/Mesquite_Solar_project. I can go over 35%, but the point’s clear. In the real world roughly half of grid scale solar power is generated from plants over 25% capacity factors and sub 15% is mostly just outdated solar thermal or very poor locations only in use because of subsidies. https://emp.lbl.gov/pv-capacity-factors
Thermal power plants pay for fuel and therefore real world capacity factors are lower as renewable generation increases. I could point to many coal power plants in the 40-50% range, but that feels pointless.
Anyway, rooftop solar isn’t representative of the grid scale solar because it’s doesn’t use ideal angles for the latitude let alone 1 or 2 axis tracking. It’s also frequently shaded by trees etc. People trying to make money selling at wholesale prices just care more about efficiency than someone offsetting retail electricity rates.
You are still not getting it. If someone says "we installed 1GW of capacity" then what does that mean?
It means you've either got 1GW of dispatchable generation on hand, or some proportionally much smaller amount of non-dispatchable generation on hand.
The number doesn't mean anything without correct context which was the entire point.
But "dispatchable" is key. Choosing to run a thermal powerplant at lower output due to market conditions is different to literally being unable to generate energy.
So talking about "X increase in renewables" doesn't tell you a thing, which was the entire point I was making.
If you build 100GW of solar then in temperate Australian regions it's actually like having 25, in Germany it's like having 10, and in the California desert I guess you maybe get 40. What you don't get, is 100GW on demand. And overnight you get zero.
All of which has a pretty substantial effect on whether "installed capacity" can move the needle on total CO2 emissions because the effect on grid production is much less linear then traditional thermal power plants.
“Wind and solar supplied 12% of global electricity in 2022” that’s the number I am tracking not how many panels they happened to use. Location and other details matter. Plopping down Solar in the UK, Germany, or southeastern Australia is a poor investment. So no I don’t give a fuck about hypothetical GW in dumb locations, it’s also irrelevant to the point I was making.
Batteries + Solar means is more linear than thermal not less.
Again just track renewables by kWh over the year not simply nameplate capacity if that’s what you want to know. It’s not some secret people actively tack and report it as useful information.
As to the rest of your points, market conditions exist before you install the power plant. Initially the question is wind or solar more useful needs to be addressed. Pick solar and many choices remain.
Install solar with 1 or even 2 axis tracking and you get more hours per day of generation from the same land and panels than fixed installation but higher cost per kWh. Install it X miles west and power comes on a little later each day. Add a battery and you can shift supply within the day. People don’t just plop down panels randomly there’s a huge amount of optimization up front to maximize long term gains.
Thermal on the other hand has fewer levers, shifting the power plants location doesn’t help match the demand curve and there’s no option for cheaper but less reliable output. The economics also completely kill the idea of having batteries to cover the after work spike in demand etc etc. Right now people are trying to decide if they want a power plant that’s only going to provide 45% of hypothetical capacity while still being forced to pay the full construction costs. Net result an absolutely massive increase in how much wind and solar generation is used not just installed each year.
Literally the quote I was responding to, with a source, before you ran off on this tangent, I presume because you can't read.
You've continually failed basic reading comprehension here.
Look up the user name on that comment before you dig yourself in deeper. The very first sentence of my initial response to you specifically countered that argument, but you just want to keep repeating it as if it was somehow meaningful.
But I hardly care at this point so I’ll leave with a more simple rebuttal:
Grid scale Solar’s global capacity factor has been flat over the last several years. So kW vs kWh only matters at the local level, globally the difference is a rounding error in terms of climate change and it’s going to remain that way for at least a decade.
This logic does apply to fossil fuels because fossil fuel plants cannot compete on cost with renewables when they’re running at full capacity. In terms of actual production, many fossil fuel plants are running at lower than their potential production.
That's the entire point: a proportional increase in renewables isn't a 1:1 reduction in thermals. You don't replace 1GW of thermal plant capacity with 1GW of solar. You replace some fraction of its output, but it still runs overnight, or at times of low production or whatever.
So installed capacity increasing doesn't directly tell you much about the future composition of the grid, particularly in the absence of significant storage or overnight capable sources like wind (which after still variable).
Well, sort of. You’re likely going to use 100% of possible production for wind and solar. That’s much lower than “capacity”, true. But you’re going to use it.
Fossil fuel sources on the other hand are being rapidly downscaled. And if it’s not operationally profitable to run a gas plant at reduced capacity, the plant will have to shut down entirely. This is happening to peaker plants due to battery power coming online.
the economics of gas plants become much, much worse quickly. The cost of energy from a gas plant that’s run a small portion of its planned output is much higher due to the fixed costs.
This should push up the price of off-renewable time power, which will increase the business case for batteries. It’s a bit of a death loop.
Gas will be here for a long time yet but I predict mainstream forecasts are underestimating how quickly the tides will turn to the share of renewables
For some reason that I don't understand, the IEA mostly reports the amount of capacity added to energy systems per year and the changes in that amount. So that 50% number isn't the growth rate of solar PV energy capacity, it's the growth rate of the growth rate. OP is talking about the growth rate of the percentage of the system that is solar.
It's the equivalent of if they identified something's velocity and you tried to contradict them by pointing to its acceleration.
Probably because the base is changing fast enough that it’s hard to compare percentages of the total population over time. Geometric growth is kind of hard to follow.
Meaning it increased from 3.3% to 5% in 2023?
which mean we can produce close to 3000T of steel in a year with renewable. (1,888 millions tons were produced in a year).
The 5% is for all electric sources. I don't look at renewable only but any sources (and coil&gas makes a solid 60% of it).
I love math like this. It makes things sound doable. 144 TWH is a lot of power. The world produces about 25000 TWH per year currently. So, we're talking less than a percent here of global electricity generation. Which over the course of the next decades is going to shift to be mostly/entirely generated by renewables.
This obviously won't happen overnight. But it suggests a few long term trends for steel production to move close to where renewable power is cheapest and most plentiful. E.g. Australia is a renewables power house and exports a lot of mined but unrefined materials. Long term it makes more sense to produce aluminium, steel, etc. locally instead of exporting the ore to China, India, etc. and then re-importing it the upcycled materials.
Thank you. I actually have to point that 25,000 TWh (I have the number of 29 PWh) is electric production only. global energy consumption is ~180,000TWh (a drop of 10,000TWh during covid, yay!), 85% of it is (c)oil&gas.
My numbers might be slightly out of date. It makes sense for energy generation to have grown recently.
For oil and gas energy usage, you should take into account that usable energy and energy consumption are two things. When electrifying, you typically end up needing less energy overall. The notion of replacing oil twh with solar twh is simply wrong. This is something the IEA gets wrong in most of its reports. Which is one reason why their estimates and predictions keep having to be corrected by them every few years.
A good example is ICE cars vs. EVs. A gallon of gas represents about 33.7 kwh of energy. A Tesla can do over 4 miles per kwh. Most ICE cars get nowhere near 120 miles per gallon. Anything over 1 mile per kwh of gas is actually pretty good. Especially for bigger cars. So, an ICE car wastes about 70-80% or more of its energy (heat, noise, vibrations, friction, etc.). You see the same pattern in other sectors where electrifying usually also means improved efficiencies. Most Teslas only have 2-3 gallons worth of kwh in the car. An ICE car with a tank that small would have a terrible range.
So, a doubling or tripling of electricity generation might actually be good enough to replace most fossil fuel usage.
You are correct, but conversion from thermal to electricity is quite inneficient. and it represent 60% of global electricity production. So driving a tesla is more efficient IF it comes from renewable.
That's one of the neat things about heat pumps. In my province in Canada about 25% of our energy is used as electricity and 75% is used as heat. This is ignoring cars, looking at residential, commercial, and industrial. The majority of our electricity generation comes from coal and natural gas, with some hydro and some wind/solar. People are very keen to close down the polluting power plants but are generally quite quiet on the topic of converting our residential and commercial heating to electric even though that covers 75% of our energy use.
But with heat pumps (backed up by resistive heating since we get cold enough to need it), we can still get a win there. Natural gas and coal generation can be ~30% efficient, but heat pumps can readily have a 4:1 COP or better. Even factoring in the inefficient generation of electricity we can still heat our homes with net less energy and then focus on replacing our electricity generation with less polluting sources (eg a mix of nuclear baseload, wind+solar+battery, and natural gas as a fallback)
EVs (and heat pumps) do not require renewable grids to be more efficient than ICE cars (and gas boilers)
They are sufficiently more efficient (roughly 4x) than even adding the 60% inefficiency of gas turbines and electricity transmission, charging losses etc. do not destroy their inherent efficiency advantage.
I loved this, especially because when I read comments that start with "It's math time", usually they go on to show how some "nice in theory" idea would never scale, but that's the complete opposite in this case!
Also, another thing that's good about these types of energy intensive industrial operations is they can essentially act as a sort of battery - it's a large load on the grid but (I'm guessing, someone correct me if I'm wrong) could potentially be more flexible with respect to time shifting: if it's a bright sunny day, crank up the furnaces to full speed, but if it's cloudy, back off. That helps make solar installations more economical if there is a good chance something will be there to take up extra power.
You're correct that the power required is quite big. It's actually one of the dead-spot in my comment. Supplying 135MWh for 37min is a lot. For example, the Jichuan Solar Park – China is "1,000MWh" and 90km^2 wide (I assume the number is the optimal output).
So, if we want to produce 1,888 millions tons of crude steel with solar panels, and assuming we can supply with Jichuan solar park 10 plants producing 300T of steel:
1,888/3 = 630 steel factory = 630 Jichuan Solar park = 56700km2. It's a bit larger than Croatia. For steel only. And it's assuming ideal production, only solar panel surface...So it could be Ireland actually.
As for the "nice in theory", my small demonstration is actually in this ball park, because the other dead-spot is that I account for electric production. It represent ~30PWh and worldwide consumption of energy is ~180 PWh (85% of those are from fossil).
So this 5% increase of renewable energy, of total electricity production, is actually swimming in those 15%.
There's another catch to your calculation: arc furnaces use scrap steel, which is only enough to supply 30% of the world's demand at this time. That's why 30% of steel is from electrical power. AFAIK most of the furnaces are already built in places with plentiful renewable power to take advantage of negative power prices. There are furnaces in Europe that operate only when the power is free.
Most of the world's steel is produced from ore, which not only requires three times the energy of recycling scrap but also vast quantities of carbon from fossil fuels to incorporate into the alloy. I believe there's a relatively new electrolytic process for the ore but at far smaller scale and it requires even more power.
Northern Africa has a lot of cheap land and a lot of sun. Wind, too. Steel can be then transported (it is already shipped across large distances). You would have to solve maintenance, but that should be doable.
The main obstacle for investment is political stability and alignment.
That's actually a lot less than I thought it would be. My smallish (6kW) solar system on my garage has generated 20MWh in the ~3.5 years it's been operating. I'm sure 50 tons (in theory) of steel isn't huge by industrial standards, but that's more than I'd expect from a residential array in Michigan.
It's a little bit more than the energy of a "normal" lightning, according to wikipedia^T^M
One of the side problem is energy density. Your garage can deliver 6kWh at best, but it can't deliver 12kWh for 30min.
you don't happen to play factorio do you?
I did played to shapez. But I realized it's programming for kids and I'm not a kid anymore ahah, so better programming for usefull things.
The heated metal can act as a battery. Another post on HN says they can recover 40% of energy from a heat source over 1000C. Seems like everyone wins here.
Every one has a plan until reality strikes. Or as Mike Tyson put so eloquently, “Everyone has a plan until they get punched in the mouth."
The 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.
I 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.
Home 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/9b...
old concrete is not in high demand. unfortunately, when i try to follow your link it just says 'fuck you, wetback scum', like every home depot page, so i'm not sure what your evidence is. are they offering you money for your old concrete? how much are they paying?
something like 15% of the material that gets carted to landfills is old concrete
generally speaking, old concrete is used in new concrete as (very) coarse aggregate. alternative coarse aggregate is mostly angular crushed stone, like the track ballast you see around railroad tracks. this is made by dynamiting deposits of limestone, granite, or basalt and feeding it through a rock crusher. while this sounds violent and energy-intensive, it's nothing compared to running a cement clinker kiln. most of the cost of coarse aggregate is from the cost of shipping it, not the cost of the energy needed to crush it; as wp says
Every link to homedepot.com calls you a racial slur?
It rejected my advances as a corked hat wearing kangaroo chaser ... it appears to be heavily geofenced and insular.
It rejected me like the potato eating stout drinking bare knuckle fighter that I am.
mar ná beidh ár leithéidí arís ann
Can confirm; told me to go shag some sheep.
at greater length, what it says is 'Access Denied You don't have permission to access "http://www.homedepot.com/c/ah/how-to-dispose-of-concrete/9ba..." on this server.', as it always does when you access a homedepot.com page from argentina; i summarized it for your benefit
Home depot left south america in 2001. I think you may be hallucinating persecution.
https://vmsd.com/home-depot-leaves-south-america/
I 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.
But it's already transported. You can't demolish an old concrete structure and just leave the rubble there. Old concrete is already moved to sites to crush it down to gravel for re-use in other applications.
The issue is whether the extra transport would offset any benefits - which I'd say is unclear. i.e. even if you had to truck this stuff to ports and put it on ships...that could be worth it, because we already truck every component of concrete around.
Using demolished concrete rubble in roads is pretty much the lowest form of recycling possible. Up-cycling it so you can make new cement and ultimately new concrete which can be used structurally at a huge carbon advantage is far more valuable - most certainly from a carbon perspective and likely from a financial one as well.
So what will they use for roads if they run out of rubble? It has to come from somewhere?
Road grit has basically no constraints. They put in whatever is cheap to dilute the expensive cement or asphalt as much has possible. Old concrete is used because it's cheap, not because it's special in some way.
If old concrete can be turned into new cement, that is extremely valuable compared to using it as grit.
There are some logistics and energy questions, though. Transporting old concrete to the nearest steel plant could be too expensive to be worth it. And arc-furnace steel plants are still the exception, not the rule.
My question about these things is always, "what are we not thinking about?"
There's a lot more to environmental responsibility than just carbon. Killing all the fish to reduce carbon isn't an answer. Of course we're not talking about doing that, but aren't we? How do we know?
History tells us that government has repeatedly destroyed ecosystems while trying to repair or preserve them. The Grand Canyon, African elephant, countless small lakes and canyons around the US.
All of these were well meaning projects to preserve, protect, and repair ecosystems.
Responsible environmentalism is far more important than reducing carbon, is my point. So let's do both by asking questions.
Putting old concrete into roads loses almost all of its value and is a pretty atrocious form of downcycling; notice that the linked article is literally about “disposing” of concrete, not re-using it meaningfully. Most of concrete’s primary use case is as a structural material in buildings/infrastructure - beams, columns, slabs, etc, and we unfortunately have very little by way of re-using concrete structurally, partly due to demolition processes, documentation, rebar etc etc. While pre-cast concrete is potentially more up-cyclable, again, it’s not really designed for disassembly, re-assessment, etc, and there are very few actual use-cases/projects that have done anything of the sort, though some very cool research is being done on this at places like MIT and EPFL, including novel pre-cast concrete systems specifically designed for dis-assembly and re-use.
Part of what makes the article and methodology linked here interesting is that it a) uses waste heat which b) is already theoretically able to come from renewable sources and c) can be used to to support manufacturing of structural components further upstream in the lifecycle of cement/concrete.
One of the problems with calculating CO2 emissions from concrete is the process involves cooking off the CO2 out of a carbonate mineral, but when you actually use it to construct something, the chemical reaction to make it involves pulling that same CO2 back out of the atmosphere into the concrete as it cures. A big chunk of it in the first few days of curing, and in theory all the rest in a long tail of curing which takes decades (in practice not actually all of it).
So how do you account for this – temporary – CO2 emission when doing your calculations?
Often it depends on the story you're trying to tell... lying with statistics and all.
this is true of lime cement, but it is not true of portland cement. portland cement absorbs much, much less carbon dioxide from the atmosphere than the lime used to make it released when it was calcined. (i think the figure i heard was 15%?)
this is one of the reasons that green building promoters are advocating a return to lime cement for cases where it's applicable
Once 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.
How soon is soon to you? https://www.eia.gov/todayinenergy/detail.php?id=50357
Also 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-t...
All material exponential curves are sigmoids, no? It’s a question of when things stop accelerating.
Of 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).
100% of what?
to look at it another way, when will we have so much solar energy production that it's hard to find a market for more solar energy at costs similar to present plant costs? right now a megawatt-hour of solar power costs usually about 25 dollars, half to a third of the cost of a megawatt-hour of power from coal or oil. the energy transition has, roughly speaking, cut the cost of energy in half. in sunny places, it's even cheaper. that means many energy-intensive industrial processes that were previously unprofitable have just become very profitable. how will that reshape the economy?
it's hard to say in detail, but clearly, as those ramp up, energy demand will increase
if you think the answer is '100% of current world electrical generation' or even '100% of current world marketed energy consumption' you've imported the implicit assumption that this seismic change in the energy market, unprecedented since the early days of the steam engine, won't reshape the economy at all and won't increase energy demand at all. this seems like a very implausible assumption
a more plausible endpoint is '100% of the sunlight that hits the earth'—once we start approaching that endpoint, we'll have problems like oxygen-producing algae dying off in the ocean because it's not getting any sun. that starts to become a problem at roughly 1000× current world marketed energy production, 10 doublings, so, around 02050
Space is a way to expand solar capture beyond the surface area of the earth.
agreed
The shape of the curve is a bit of a red herring, unless additional context is considered. Decay could mean we have succeeded in decarbonizing the entire power sector, which is a signal of success. Or decay could mean California has finally built all the solar it needs but no other states are following in California's footsteps, which is a signal of failure. Both are instances of decay that signify very different situations.
You are correct though that a naive prediction of constant doublings is definitely wrong. China is showing signs of slowing over the last month due to transmission and storage bottlenecks in a few locations. BNEF has an article about this.
We have 1 TW of installed capacity today. In 6 doublings, that is 64 TW. If it doubles every 2-3 years, that’s in about 20 years.
Thats more power than coal+oil+nuclear today.
https://ourworldindata.org/grapher/installed-solar-pv-capaci...
According to your own chart, it doubles every 4 years, so 24 years.
And it's not guaranteed to double like that.
They fit a linear line to a phenomenon that is currently moving exponentially, and has no signs of slowing down.
From 2010: https://youtu.be/MAFoqo3Jbro?si=tg11Iunaclk2L2uH.
That's a 2021 prediction for 2050 which has 20% as the main reference case (some go up to 27% if gas is expensive, for example).
The 2023 prediction updated the reference case to closer to 40% in 2050 (again some go higher).
That's a big jump in two years.
Nuclear 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.
Nope. 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.
That'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.
Steelmaking 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.
Is 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.)
People 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-nucl...
How 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.
Concrete 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.
see https://news.ycombinator.com/item?id=40461810 for a correction
What are you even talking about? CO2 is absorbed during curing.
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.
What if we are successful with Nuclear Fusion?
Impact would depend on cost per kWh of the fusion energy
I imagine we'll be air conditioning bigger spaces and more liberally, in a lot of places.
Arc furnaces are also expensive so realistically you want to have one running as close to 24/7 as possible.
https://english.aaj.tv/news/330362080/germanys-solar-boom-le...
Jevons Paradox will take care of any surplus created.
What's the catch