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If a comet with this speed fell to the Earth it would gain another 63 MJ/kg, yielding a total of 2655 MJ/kg with a speed of 72.9 km/s. Since the equator is moving at about 0.5 km/s, the impact speed has an upper limit of 73.4 km/s, giving an upper limit for the specific energy of a comet hitting the Earth of about 2690 MJ/kg.
(MJ/kg) Energy density (MJ/L) Specific energy Energy density (W⋅h/L) Comment Antimatter: 89 875 517 874 ≈ 90 PJ/kg: Depends on the density of the antimatter's form 24 965 421 631 578 ≈ 25 TW⋅h/kg Depends on the density of the antimatter's form Annihilation, counting both the consumed antimatter mass and ordinary matter mass Hydrogen ...
Specific energy (MJ/kg) Energy density (MJ/L) Peak recovery efficiency % Practical recovery efficiency % Arbitrary Antimatter: 89,875,517,874: depends on density:
This thermal energy input of 1 kWh = 3.6 MJ = 3,412 Btu; Therefore, the heat rate of a 100% efficient plant is simply 1, or 1 kWh/kWh, or 3.6 MJ/kWh, or 3,412 Btu/kWh; To express the efficiency of a generator or power plant as a percentage, invert the value if dimensionless notation or same unit are used. For example: A heat rate value of 5 ...
In all, the higher heating value of hydrogen is 18.2% above its lower heating value (142 MJ/kg vs. 120 MJ/kg). For hydrocarbons, the difference depends on the hydrogen content of the fuel. For gasoline and diesel the higher heating value exceeds the lower heating value by about 10% and 7%, respectively, and for natural gas about 11%.
A kilowatt is a unit of power (rate of flow of energy per unit of time). A kilowatt-hour is a unit of energy. Kilowatt per hour would be a rate of change of power flow with time. Work is the amount of energy transferred to a system; power is the rate of delivery of energy. Energy is measured in joules, or watt-seconds.
1.0 TJ (280,000 kWh) gigajoule: GJ GJ 1.0 GJ (280 kWh) megajoule: MJ MJ 1.0 MJ (0.28 kWh) kilojoule: kJ kJ 1.0 kJ (240 cal) hectojoule: hJ hJ 1.0 hJ (24 cal) decajoule: daJ daJ 1.0 daJ (2.4 cal) joule: J J 1.0 J (0.24 cal) decijoule: dJ dJ 1.0 dJ (0.024 cal) centijoule: cJ cJ 1.0 cJ (0.0024 cal) millijoule: mJ mJ 1.0 mJ (0.00024 cal) microjoule ...
[citation needed] Electric pedal-assisted bikes run on as little as 1.0 kWh (3.6 MJ) per 100 km, [55] while maintaining speeds in excess of 30 km/h (19 mph). [ citation needed ] These best-case figures rely on a human doing 70% of the work, with around 3.6 MJ (1.0 kWh) per 100 km coming from the motor.