Watt-hour per kilogram
| watt-hour per kilogram | |
|---|---|
| Unit system | Unit accepted for use with SI |
| Unit of | Specific energy |
| Symbol | W⋅h/kg |
| Conversions | |
| 1 W⋅h/kg in ... | ... is equal to ... |
| SI units | 3600 J/kg |
The watt-hour per kilogram (unit symbols: W⋅h/kg) is a unit of specific energy commonly used to measure the density of energy in batteries and capacitors.
Conversion to SI units
[edit]The watt, kilogram, joule, and the second are part of the International System of Units (SI). The hour is not, though it is accepted for use with the SI. Since a watt equals one joule per second and because one hour equals 3600 seconds, one watt-hour per kilogram can be expressed in SI units as 3600 joules per kilogram.
Typical values
[edit]As of June 2022, the highest peer reviewed and published results for an electric car battery is an energy density 350 W⋅h/kg, which has achieved 500 cycles with less than 20% capacity fade.[1] This compares to supercapacitors that are typically rated between 3 and 10 W⋅h/kg,[2] with the best commercially available supercapacitors as high as 47 W⋅h/kg.[3]
Nuclear batteries based on betavoltaics can reach up to 3300 W⋅h/kg, although over much longer time periods.[4]
References
[edit]- ^ Kim, Sangwook; Tanim, Tanvir R.; Dufek, Eric J.; Scoffield, Don; Pennington, Timothy D.; Gering, Kevin L.; Colclasure, Andrew M.; Mai, Weijie; Meintz, Andrew; Bennett, Jesse (2022-06-30). "Projecting Recent Advancements in Battery Technology to Next‐Generation Electric Vehicles". Energy Technology. 10 (8). doi:10.1002/ente.202200303. ISSN 2194-4288.
- ^ Hao Y, Santhakumar K (2013). "Achieving Both High Power and Energy Density in Electrochemical Supercapacitors with Nanoporous Graphene Materials". p. 3. arXiv:1311.1413.
- ^ Ronald Brakels, "Arvio Supercapacitor Energy Storage — Powerful Enough To Beat Batteries At Their Own Game?", Solarquotes.com, May 15, 2018. Retrieved 14 Oct. 2021
- ^ Prototype Nuclear Battery, phys.org, June 6 2018
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