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The following table shows a range of estimates of the levelized costs of gray, blue, and green hydrogen, expressed in terms of US$ per kg of H 2 (where data provided in other currencies or units, the average exchange rate to US dollars in the given year are used, and 1 kg of H 2 is assumed to have a calorific value of 33.3kWh).
J⋅kg −1 ⋅K −1: ... where δQ is the heat supplied to the system and δW is the work done by the system. ... Heat capacity (constant pressure) = ...
At an electricity cost of $0.06/kWh, as set out in the Department of Energy hydrogen production targets for 2015, [73] the hydrogen cost is $3/kg. The US DOE target price for hydrogen in 2020 is $2.30/kg, requiring an electricity cost of $0.037/kWh, which is achievable given recent PPA tenders for wind and solar in many regions. [ 74 ]
The SI unit for heat capacity of an object is joule per kelvin (J/K or J⋅K −1). Since an increment of temperature of one degree Celsius is the same as an increment of one kelvin, that is the same unit as J/°C. The heat capacity of an object is an amount of energy divided by a temperature change, which has the dimension L 2 ⋅M⋅T −2 ...
The SI unit of specific heat capacity is joule per kelvin per kilogram, J⋅kg −1 ⋅K −1. [2] For example, the heat required to raise the temperature of 1 kg of water by 1 K is 4184 joules , so the specific heat capacity of water is 4184 J⋅kg −1 ⋅K −1 .
The contribution of the muscle to the specific heat of the body is approximately 47%, and the contribution of the fat and skin is approximately 24%. The specific heat of tissues range from ~0.7 kJ · kg−1 · °C−1 for tooth (enamel) to 4.2 kJ · kg−1 · °C−1 for eye (sclera). [13]
However, for it to be in a fully liquid state at atmospheric pressure, H 2 needs to be cooled to 20.28 K (−252.87 °C; −423.17 °F). [5] A common method of obtaining liquid hydrogen involves a compressor resembling a jet engine in both appearance and principle. Liquid hydrogen is typically used as a concentrated form of hydrogen storage ...
Where F B = Buoyant force (in newton); g = gravitational acceleration = 9.8066 m/s 2 = 9.8066 N/kg; V = volume (in m 3). Therefore, the amount of mass that can be lifted by hydrogen in air at sea level, equal to the density difference between hydrogen and air, is: (1.292 - 0.090) kg/m 3 = 1.202 kg/m 3