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Would this be in a scenario where homes are producing more electricity than they need, and using the extra to reduce iron oxide? With solar getting cheaper and

Would this be in a scenario where homes are producing more electricity than they need, and using the extra to reduce iron oxide? With solar getting cheaper and cheaper, definitely a possibility. A system more similar to what we have in New England would be the opposite of what you describe: a truck drops off a load of fresh (elemental) iron, and it's oxidized over the winter to heat the house. Then, in the spring, someone comes back and removes all the rust for recycling. This plan would allow iron to replace a lot of propane and heating oil if the energy densities work out.

thinkcontext 4y ago
> Would this be in a scenario where homes are producing more electricity than they need, and using the extra to reduce iron oxide? There's no need for this to be done at a home, since the home is on the grid.
dragontamer 4y ago
> A system more similar to what we have in New England would be the opposite of what you describe: a truck drops off a load of fresh (elemental) iron, and it's oxidized over the winter to heat the house. Then, in the spring, someone comes back and removes all the rust for recycling. This plan would allow iron to replace a lot of propane and heating oil if the energy densities work out. I have severe doubts that iron has as much energy density as methane or propane. I also doubt that Iron is as easy to carry around as methane pipelines.
- foxyv 4y ago
  > I have severe doubts that iron has as much energy density as methane or propane. The heat of reaction of elemental iron oxidizing to rust is about 1648kJ per 4 moles Iron. Propane burning is about 2220kJ per mole. Also, Iron atoms are heavier than molecules of propane (55.8g/mol vs 44.1g/mol). This means that propane has an energy density of about 50 joules/gram while Iron has about 7 Joules/gram. So no, not very energy dense on a per kilogram basis. However, energy density is only relevant to cost of transportation. If elemental iron is stupid cheap compared to methane due to taxation of external costs associated with emitting carbon dioxide, then the additional cost to transport it would be less relevant. In addition, since it is renewable, the cost could be reduced further. But yeah, we are a long way from that since methane and propane are very cheap right now.
  - dragontamer 4y ago
    > then the additional cost to transport it would be less relevant I mean, if weight is the only issue, then maybe don't transport it ever? Its not like we try to "transport" the Bath County Pumped hydro station around (aka: the largest battery in the USA). We just let it sit in one location and convert from electricity (usually nuclear at night) into energy-storage (pump water uphill), and then convert it back later (release the water during daytime peak-electricity usage). --------- If the energy "needs to be transported", then convert the energy into another form (Ethanol fuel? Syngas Kerosene? ). Each conversion loses efficiency of course, but if Iron is cheap enough to use as "energy storage", then it can be our "energy storage of last resort", since any storage is better than waste. (IE: Never turn off your solar panels. We always have "something" to dump our excess electricity into)
    - foxyv 4y ago
      I was thinking on a residential basis where you would buy and recycle the iron powder. But yes, in a large commercial heat storage facility you would not need to transport the iron at all. Pretty cool!

thinkcontext 4y ago

> Would this be in a scenario where homes are producing more electricity than they need, and using the extra to reduce iron oxide? There's no need for this to be done at a home, since the home is on the grid.

dragontamer 4y ago

> A system more similar to what we have in New England would be the opposite of what you describe: a truck drops off a load of fresh (elemental) iron, and it's oxidized over the winter to heat the house. Then, in the spring, someone comes back and removes all the rust for recycling. This plan would allow iron to replace a lot of propane and heating oil if the energy densities work out. I have severe doubts that iron has as much energy density as methane or propane. I also doubt that Iron is as easy to carry around as methane pipelines.

foxyv 4y ago
> I have severe doubts that iron has as much energy density as methane or propane. The heat of reaction of elemental iron oxidizing to rust is about 1648kJ per 4 moles Iron. Propane burning is about 2220kJ per mole. Also, Iron atoms are heavier than molecules of propane (55.8g/mol vs 44.1g/mol). This means that propane has an energy density of about 50 joules/gram while Iron has about 7 Joules/gram. So no, not very energy dense on a per kilogram basis. However, energy density is only relevant to cost of transportation. If elemental iron is stupid cheap compared to methane due to taxation of external costs associated with emitting carbon dioxide, then the additional cost to transport it would be less relevant. In addition, since it is renewable, the cost could be reduced further. But yeah, we are a long way from that since methane and propane are very cheap right now.
- dragontamer 4y ago
  > then the additional cost to transport it would be less relevant I mean, if weight is the only issue, then maybe don't transport it ever? Its not like we try to "transport" the Bath County Pumped hydro station around (aka: the largest battery in the USA). We just let it sit in one location and convert from electricity (usually nuclear at night) into energy-storage (pump water uphill), and then convert it back later (release the water during daytime peak-electricity usage). --------- If the energy "needs to be transported", then convert the energy into another form (Ethanol fuel? Syngas Kerosene? ). Each conversion loses efficiency of course, but if Iron is cheap enough to use as "energy storage", then it can be our "energy storage of last resort", since any storage is better than waste. (IE: Never turn off your solar panels. We always have "something" to dump our excess electricity into)
  - foxyv 4y ago
    I was thinking on a residential basis where you would buy and recycle the iron powder. But yes, in a large commercial heat storage facility you would not need to transport the iron at all. Pretty cool!