# Standard litres to kg conversion for Hydrogen [closed]

When looking at hydrogen fuel tanks, they often give the capacity in terms of "standard litres". However, I can't find a definition of what this is.

I assumed this may mean a litre of hydrogen gas at room temperature? If so, is this at standard air pressure or is it compressed to a certain pressure? If so, what is this pressure?

I also thought perhaps it was a conversion to a litre of liquid hydrogen?

Or is it neither of these?

Is there a conversion between standard litres and kilograms for Hydrogen?

• Since 1982, STP is defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly $10^5$ Pa (100 kPa, 1 bar). At STP a mole of gas occupies 22.7 liters. A mole of hydrogen has a mass of 2.016 grams. Thus $8.88\times10^{-2}$ grams/liter. – MaxW Apr 8 '19 at 15:18
• Are you talking about hydrogen fuel tanks for cars? or something else? – Mathew Mahindaratne Apr 8 '19 at 18:55
• @MathewMahindaratne, it isn't specifically tanks for cars, although I guess this could be an application. It is merely that if I look at Hydrogen storage tanks on the internet, many companies define the capacity in terms of "standard litres" and I was just curious as to what the definition of one "standard litre" is. – PhysicsGuy123 Apr 8 '19 at 19:49

## 1 Answer

There has been a lot of promising buzz around hydrogen. Many people believe that hydrogen can be used as an energy carrier to replace other fuels like gasoline in the near future. One of the largest challenges to use hydrogen in a wide scale is its storage after hydrogen is produced. Some storage technologies have currently been developed. Yet, according to Florida Solar Energy Center, following three methods have been continuously used:

1. As a compressed gas (in high-pressure tanks).
2. As a liquid in dewars or tanks (stored at $$\pu{-253 ^{\circ}C}$$).
3. As a solid by either absorbing or reacting with metals or chemical compounds or storing in an alternative chemical form.

The current status of various storage technologies in terms of weight, volume and costs is given below (From: Florida Solar Energy Center):

$$\begin{array}{|c|c|c|c|c|c|} \hline \textrm{Storage Technology} & \textrm{Weight} & \textrm{Volume} & \textrm{Average Cost} \\ \textrm{} & \textrm{(kWh/kg)} & \textrm{(kWh/L)} & \textrm{(USD/kWh)} \\ \hline \textrm{Chemical Hydrides} & 1.6 & 1.4 & 8 \\ \hline \textrm{Complex Metal Hydrides} & 0.8 & 0.6 & 16 \\ \hline \textrm{Liquid Hydrogen} & 2.0 & 1.6 & 6 \\ \hline \textrm{Compressed Gas (10,000-psi)} & 1.9 & 1.3 & 16 \\ \hline \end{array}$$