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the dark side of cobalt
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Zero999:

--- Quote from: NiHaoMike on July 16, 2023, 07:42:28 pm ---
--- Quote from: tom66 on July 16, 2023, 03:35:43 pm ---Why not just transport electricity?  China has a 3,200km ultra HVDC transmission line (+/-1.1MV) built by ABB, it transmits up to 12GW.  Efficiency is in excess of 90%.  Going up to +/-1.5MV UHVDC could allow transmission beyond 5,000km with similar efficiency. 

--- End quote ---
The temperature difference between the hot and cold areas is an energy source that could theoretically be exploited. Probably not enough to make the whole system a net generator, but it could make the effective efficiency very high.

--- End quote ---
https://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion?useskin=vector
nctnico:

--- Quote from: tom66 on July 16, 2023, 03:35:43 pm ---
--- Quote from: NiHaoMike on July 16, 2023, 01:12:46 pm ---It seems like what would really solve a large part of the energy problem is some sort of heat transportation system interconnecting countries in southern and northern hemispheres. It's technically feasible, but nobody has found a way to make it economically feasible yet.

--- End quote ---

Why not just transport electricity?  China has a 3,200km ultra HVDC transmission line (+/-1.1MV) built by ABB, it transmits up to 12GW.  Efficiency is in excess of 90%.  Going up to +/-1.5MV UHVDC could allow transmission beyond 5,000km with similar efficiency.

--- End quote ---
Start including cost per kWh into these calculations and see how it may not be such a good idea! For the umpteenth time: efficiency is low on the list of what is important where it comes to energy transport. Or put differently: price per kWh is the only thing you need to worry about. Things like efficiency and utilisation are just parameters to make the economics of a transport system worth it or not.
tom66:

--- Quote from: nctnico on July 16, 2023, 08:12:28 pm ---
--- Quote from: tom66 on July 16, 2023, 03:35:43 pm ---
--- Quote from: NiHaoMike on July 16, 2023, 01:12:46 pm ---It seems like what would really solve a large part of the energy problem is some sort of heat transportation system interconnecting countries in southern and northern hemispheres. It's technically feasible, but nobody has found a way to make it economically feasible yet.

--- End quote ---

Why not just transport electricity?  China has a 3,200km ultra HVDC transmission line (+/-1.1MV) built by ABB, it transmits up to 12GW.  Efficiency is in excess of 90%.  Going up to +/-1.5MV UHVDC could allow transmission beyond 5,000km with similar efficiency.

--- End quote ---
Start including cost per kWh into these calculations and see how it may not be such a good idea! For the umpteenth time: efficiency is low on the list of what is important where it comes to energy transport. Or put differently: price per kWh is the only thing you need to worry about. Things like efficiency and utilisation are just parameters to make the economics of a transport system worth it or not.

--- End quote ---

Not sure why you think a 3,200km line is going to have high cost per kWh.  The cost of such a line is mostly capital expense and maintenance, but the line will easily last 100 years with just normal maintenance.  Chopping the trees back adjacent to the line, if any are present, is probably the biggest single bill.
TimFox:
A government report from 2018 estimated a range of about 1 to 8 million USD per mile for HVDC transmission lines.
https://www.eia.gov/analysis/studies/electricity/hvdctransmission/pdf/transmission.pdf
NiHaoMike:

--- Quote from: Zero999 on July 16, 2023, 08:12:05 pm ---https://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion?useskin=vector

--- End quote ---
Big difference between the hot and cold areas being separated by a few miles at most, as opposed to thousands of miles.
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