Solar furnace to melt steel at 2000°C for Swiss recycler | Hacker News Reader

Solar furnace to melt steel at 2000°C for Swiss recycler

solarpaces.org

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Do I have this Napkin math correct?

400 tons produced per year (original article)

$1000 per ton (generous [0], current index at $770)

$400k per year revenue (calculated)

$25M Euro investment (original article)

~63 years payback on *revenue* (being generous again with EURSD=$1)

Do I have that right?

[0] https://www.cmegroup.com/markets/metals/ferrous/hrc-steel.ht...

Plus revenue from selling carbon credits. I don't know the value of that.

You have the math right, but the product wrong. They are looking for specific types of steel that are currently unavailable at almost any price. Their order size is too small to warrant returning a phone call from normal steel producers. Certain types of tool steel that are currently available sell for upwards of $3000/ton, but the type of steel they need is no longer a commodity, so the price is likely even higher.

They have 50 tons of scrap steel that is exactly what they need, but need a spot to melt it down for reuse. You can't (partially guessing here) just throw it in an existing smeltery while maintaining its purity. They have been collecting this scrap by talking to other users that also use the same material.

The article mentions they are in the Jura Arc. I didn't know this, but that is a reference to the watchmakers valley in Switzerland. If you're selling a $60k watch, it better be made from 99.999999% pure unobtanium.

I have seen similar situations before where when you start making a niche product, suddenly demand pops out of the background that wasn't there before because the product simply wasn't available. Even if it isn't profitable from day 1 it might eventually become profitable.

Are you sure about that "unavailable at almost any price" part? Their initial inputs seem to be be the scraps produced by the local manufacturers in a relatively tiny area over the last few years. If this grade of steel wasn't available, where did all these local manufacturers get a constant supply from? (I.e. there has to be an existing and supplied market, it's not like they're recycling the steel only from the scuttled German battleships in Scapa Flow or something.)

The use cases are quoted as "watchmaking and medical subcontracting", fwiw.

Yeah, I'm not sure about that unavailable at almost any price part. If you could put in an order for a million tons of steel you would get on the steel manufacturers order list, which is what I was thinking about when I mentioned almost any price. But it sounds like they have been working through their existing material for decades and are only now running out. The material may have last been produced a long time ago so the quantities they need are very small. That 50 tons of scrap may last them for another decade or two.

Wow, that is very interesting and informative. I had not realized that.

You would not be able to throw it in a ‘smelter’ and have it maintain its chemistry - smelters are huge mass production shops. A foundry could do this without problem. They exist to do small, chemically precise runs.

Ah, thank you. I didn't know what the difference was between a smelter and a foundry.

A few year ago, someone posted about designing a new stainless steel for ¿knives? Something about copying the properties of some well known iron alloy to a stainless version. IIRC you should add some chrome to make it stainless and vanadium to make it hard, and then some long explanation about the carbon content so there is not a lot of ¿chrome carbide? inside the steel. He hired a specialized foundry to make a small batch with very precise composition. It was very interesting but very above my metallurgy knowledge, so I don't' remember the details. And sadly I can't find the link now.

I believe it was this post? If not I'm curious about it if you remember. The link and discussion here was a fascinating look into another world for me.

https://news.ycombinator.com/item?id=29696120 https://knifesteelnerds.com/2021/03/25/cpm-magnacut/

It was that post. Thanks.

To decarbonize heavy industry, highly concentrated solar thermal is the best option. Heat is the form of energy most responsible for carbon emissions in industries like steel and cement. Solar thermal (duh) generates heat from thousands of "suns" of sunlight.

Solar may replace the heat component in some applications (as in this one), but in refining steel the carbon is required for the chemical process - it binds the oxygen from the iron. Carbon in that application can be replaced by hydrogen, but it can’t be just replaced by another heat source.

How is that carbon emissions? It sounds like carbon absorbed?

> How is that carbon emissions?

In goes iron ore, a mix of iron oxides and carbon, out comes iron and carbon oxides. The carbon moved from the ore to the atmosphere.

So if I recall correctly from HS chem, iron is being reduced in this case by the carbon in the coke. From a cursory glance at the electronegativity table, iron is at 1.83, carbon's at 2.5 and hydrogen is 2.1. Higher electronegativity = more attractive to electrons = better reducing agent so hydrogen will reduce iron but less efficiently? than carbon. I don't know if this means that more energy is required to get the hydrogen to reduce carbon, or if the reaction will just be slower, but the upside is that the only byproduct of this process is pure H2O.

You push a lot of carbon into the iron, most react with oxygen and go away as CO2. So the entire process emits CO2, and absorb pure carbon (usually from oil).

You can reduce iron by electrolysis, where you vent oxygen instead of CO2 or water. You'll just need a higher temperature and some quite robust electrodes (both of what are currently expensive).

What you just can't do is replace the carbon that is added into the steel. The process will always need a carbon source.

CSP is way more efficient than photovoltaics, but electricity is much more flexible and easier to control than heat.

I'll not be surprised if the industry decides to waste 70% of the energy and go with photovoltaics.

That, or there will be an optimal mixture. Eg, CSP may be akin to baseload and you'd draw from the grid for the rest

I’d be willing to bet this design is more expensive than solar panels and using an electric furnace which is common for recycling steel.

You still need some way to deal with rust, and carbon electrodes work great.

Steel is roughly $500 per ton, so they are looking at $200k a year in revenue. This is a cool research project, but the economics are not realistic anytime soon.

Yeah but the site already existed. So it's a very cheap way to test the idea.

As someone in the recycling supply chain, this is incredibly cool. The possible carbon reduction emissions are massive. This would need to scale up by factors of 100 (400 tons a year is nothing- a single sea borne cargo that is traded is often 32-40000 tons), but amazing to see the cutting edge.

> The solar furnace could melt up to 400 tons of recycled steel each year.

This is very little, it's about the amount of steel used in 450 cars.

My tiny country with 5 million people (New Zealand) recycles 300,000 tonnes of steel per year.

They're a "wristwatch component manufacturer"; so presumably they need much smaller quantities than a car manufacturer.

That looks like something from the future and the photo made me remember the Dune II windtaps - https://strategywiki.org/wiki/File:Dune_II_wind_trap.jpg

Much of the heavy industry in the future is likely to be in deserts near the equator.

Which would be nice except people don't live there, so they'd have to pay a premium to workers to relocate and live in an equatorial desert, as well as transport in all the food, water, and housing that they will need. Sort of like ocean oil platform workers.

Middle East already has a lot of workers from Asia. People follow the money, if the works is there the people will follow. The biggest problem is if it gets too hot to be able to live.

I live in a big, hot desert with millions of others right here in the USA. We are ready for this tech. Intel and TSMC think this desert is pretty awesome, as do I.

Sort of like Dubai, Abu Dhabi, Phoenix, Las Vegas? It has worked for the those places.

I always wondered why not use a system like this to heat water and use turbine to generate electricity. Shouldn’t this get much higher output efficiency compared to pv panels.

Systems like that already exist. They’re known as Concentrated Solar Power: https://en.m.wikipedia.org/wiki/Concentrated_solar_power

Thanks, that is awesome.

The problem is that it's more expensive on a levelized cost of energy basis than solar and wind.

It might be more competitive if it can be paired with thermal storage, but AFAIK that's not demonstrates at scale yet.

The thermal energy storage aspect of CSP is how the heat is accessed to run the power block - it not paired with- like some kind of bolt-on extra - is definitely demonstrated at scale. Just not in the US, which only tried out 5 CSP plants, only 2 with storage. China is currently building 30 CSP plants - all with storage. Here's how thermal energy storage in CSP works https://www.solarpaces.org/how-csp-thermal-energy-storage-wo...

The break even point might be near, currently every mirror is controlled by an open loop controller of some sophistocation to point exactly right relative to the sun, time of day and tower.

But the CSIRO has a system where a camera looks at the mirrors from the tower and estimates quite well the mirror angle from the shade of blue reflected.

This makes it closed loop control, one sensor for many mirrors and simple actuation like lead screw with raise/lower controls possible.

That's good, because from my recollection, the really expensive parts of CSP are the complex heliostats, a great many of which are needed in order to reflect sufficient light on the target.

The maximum efficiency of a steam turbine is just shy of 50%, by the time you have integrated the whole plant, 23-35% is typical. (so says wikipedia)

The sort of solar panels one would use in a large installation are around 23% efficient.

So they are close in "power/hectare". From there it is capital costs and cost of operation that will make the decision.

Thermodynamics, blah, blah. Buncha' people no doubt fun at parties.

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