Subdwarf B star Subdwarf B star A B-type subdwarf (sdB) is a kind of subdwarf star with spectral type B. They differ from the typical subdwarf by being much hotter and brighter. They are situated at the "extreme horizontal branch" of the Hertzsprung–Russell diagram. Masses of these stars are around 0.5 solar masses, and they contain only about 1% hydrogen, with the rest being helium. Their radius is from 0.15 to 0.25 solar radii, and their temperature is from 20,000 to 40,000K. These stars represent a late stage in the evolution of some stars, caused when a red giant star loses its outer
Power-to-gas reaction, or biological methanation resulting in an extra energy conversion loss of 8%. The methane /SNG may then be fed into the natural gas grid or further converted in to LPG by synthesising SNG with partial reverse hydrogenation at high pressure and low temperature. LPG in turn can be converted into alkylate which is a premium gasoline blending stock because it has exceptional antiknock properties and gives clean burning. The third method uses the output gas of a wood gas generator or a biogas plant, after the biogas upgrader is mixed with the produced hydrogen from the electrolyzer, to upgrade