What’s the chemical energy content of the 100,000 kg of liquid hydrogen that was stored in the space shuttle’s external fuel tank?

Question

How long could this energy power human civilization at our consumption rate of 18 TW?

Answer 1

When hydrogen reacts with oxygen and generate water, the released chemical energy is 286 kJ/mol (molecule). Hydrogen molecule weight is 2, so each mole hydrogen mass per mol is 2 g. Therefore the energy density of hydrogen is 286 kJ/mol / 2g/mol = 143 kJ/gram = 143 MJ/kg.

Energy contained in 100,000 kg of hydrogen is 143 ×10⁶ × 10⁵ = 1.43 × 10¹³ J,

if the power is 18 TW = 1.8×10¹³ W, the time last is t = 1.43 × 10¹³ J / 1.8×10¹³ W = 0.794 sec.

In some literature, the energy density of hydrogen is 120 MJ/kg, using this value, the answer is 0.666 sec.