page giving #energy-density of different kinds of #lithium-ion #batteries #materials.
on 02025-06-17#video from a month ago saying lithium iron phosphate #lithium-ion #batteries had fallen in #pricing in December to US$115/kWh (US$32/MJ), quoting BloombergNEF. Says raw materials are 70% of batteries’ cost [citation needed], and that LFPs have #energy-density of 90–160Wh/kg (320–580kJ/kg), much worse than NCA (230–260Wh/kg) or NMC (250–320Wh/kg), citing a page on batterydesign.net. #energy
on 02025-06-17#energy-density of #springs: 2.3 Wh/kg (8.3 kJ/kg) for AISI A11 tool steel, 1.1 Wh/kg for rubber (4.0 kJ/kg), 6.0 Wh/kg for carbon fiber (21.6 kJ/kg). By David MacKay, who died shortly afterwards.
on 02015-11-19figures on the #energy-density of different #flywheel designs. Discussion of #energy storage for I guess #solar?
on 02015-11-10#energy-density of a composite #flywheel can be up to about 400 Wh/kg, although the shape factor typically limits you to about 0.6 of that, about 900 kJ/kg.
on 02015-11-10This “micro” “MEMS” gas #turbine runs at 500krpm on, obviously, an #air-bearing (they achieved a record speed of 1.2Mrpm), with a 20mm rotor (in a total 100mm×110mm casing) producing 1kW. The turbine itself is die-sink-EDM-machined conductive ceramic (composite #silicon-nitride and titanium nitride) to withstand the 1200 K gas; supposedly 20% overall efficiency with the 74.5%-efficient recuperator. This seems like overkill on the efficiency front for mobile-power uses (cellphones, laptops, drones), where the big issue is that batteries have an #energy-density of about 500kJ/kg, while hydrocarbons are at almost 50MJ/kg, so any efficiency over about 1% would be a victory condition for microturbines over batteries.
on 02015-08-14