4 ms·
I know I'm missing something obvious here, can someone close to this tech help me out? What problem does this solve? For reference, I'd like to compare this to
by Udo 4y ago
I know I'm missing something obvious here, can someone close to this tech help me out? What problem does this solve? For reference, I'd like to compare this to a hydrogen cycle, which is apparently already a subsystem of the proposed process used to reduce the spent iron. I went to the "Why iron?" section of the web page and got the following points:
'CO2 free' - H2 cycle systems are also CO2 free
'Compact' - the energy density of iron is already pretty low and the proposed machinery also doesn't seem very compact. Maybe storing uncompressed H2 would be somewhat inconvenient depending on your location, but you can always compress it. And if you need longer term storage, you can actually make hydrocarbons from it, although that wouldn't technically be CO2 free (only CO2 neutral if you use captured carbon)
'Cost-effective' - this system seems way more expensive, per kWh and in absolute terms, than gaseous cycle concepts.
'Easy to store and transport' - the iron is certainly not easy to transport, nor is the machinery using or recycling it. It is easy to store safely, just not efficiently.
'Scalable' - while iron is abundant on Earth, most of our iron is actually at inaccessible depths, so we're stuck with traditional mining. If you think iron is cheap, you haven't tried to use it as a building material recently. Cheap and abundant metals would be calcium or potassium. Even cheaper, again: H2.
'Safe' / 'Commodity' - true, but how relevant are these, really?
- bdamm 4y agoH2 is most certainly not CO2 free. It is quite energy intensive to produce it, and currently is produced from oil & gas products. The cleaner alternative is to use clean electricity to produce it from water; but if you're going to do that, it turns out that just using the electricity is almost always more efficient.
- Udo 4y agoAny of these criticisms you levy against H2 would by extension also apply to iron, only more so. > It is quite energy intensive to produce it We're talking about a cycle that is supposed to store and release energy. "Quite energy intensive to produce" would be a plus in this context. It would matter though if it was inefficient to produce, which is not the case. On top of all that, H2 is actually a part of the proposed iron cycle system. > and currently is produced from oil & gas products It would obviously not be produced from oil and gas products in the case we're discussing here. If you're going to have an H2 cycle, it makes zero sense not to start with water. > but if you're going to do that, it turns out that just using the electricity is almost always more efficient. As far as I'm aware, the iron cycle system also does not claim to produce energy in order to compete with solar or wind. It claims to be a good and portable storage solution. Thermodynamics absolutely assures that any such system will always be less efficient than using the electricity right away. It is absolutely ridiculous to use an argument of inefficiency against an H2 cycle system while speaking in favor of an even more complex other cycle system!
- jacquesm 4y agoThe big advantage afaict is that storing hydrogen for a long time inevitably leads to losses so you can't for instance do seasonal offset with it, and using hydrogen at grid scale for combustion is tricky whereas using metal as a fuel should be very scalable. The true test will be the economics.