6 upvotes, 3 direct replies (showing 3)
View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
Part of the problem with renewable sources of energy, mainly solar and wind is that energy production does not always coincide with usage.
Energy storage is difficult, pumped storage hydro sites are not very common and batteries aren't really up to the job yet.
We can burn iron to produce energy and then use renewable power to convert iron oxide back to iron.
Is this being investigated and how would it compare to other energy storage systems?
Comment by atomfullerene at 26/04/2023 at 17:55 UTC
18 upvotes, 1 direct replies
Why go with iron specifically? There are an enormous number of other oxidation reactions you could use, starting with converting CO2 to hydrocarbons and then burning them back again. My impression (though I can't find you a specific citation) is that these processes are much less efficient than batteries, pumped hydro, etc.
Comment by abcmeiro at 26/04/2023 at 17:53 UTC
4 upvotes, 1 direct replies
The problem is that you get a very low efficiency with thermal machines. A coal plant for example has a efficiency of around 40%. I suppose the process of burning steel would be similiarily efficient.
The maximum efficiency of thermal engines is deternined by the laws of thermodynamics, more specificially by the carnot efficiency. Basicially you need an indefinetely high burning point and a surounding temperarure of absolutely zero to have a efficiency of 100%.
In reality the surrounding temperature and the burning tenperature are not that far apart, wich results in a relativly low efficiency.
Comment by [deleted] at 26/04/2023 at 19:30 UTC
3 upvotes, 0 direct replies
Systems like that are being investigated, yes. The problem is, as other commenters have said, that thermal systems obviously lose heat. A much simpler system is given by hydrogen fuel cells (conversion between water and hydrogen and oxygen gas via a proton transfer membrane)