Hydrogen

Stéphane Rapuc
Nov 3 · 2 min read

Hydrogen Energy Density

The hydrogen, or H2, has a very high specific energy of 40kWh/kg. Once compressed or madeThis is is 3–4 times more that diesel or gasoline, and 160 times more than Lithium-ion battery.
However, the energy density kWh/L of liquid hydrogen and compressed hydrogen gas at any practicable pressure is about 5 times less than diesel or gasoline, and 5 times more than Lithium-ion battery.

As such it makes it an interesting energy solution to replace fossil fuels in some of our transport solutions.

(for reference see https://en.wikipedia.org/wiki/Energy_density)

Hydrogen engines

Hydrogen can be used in two ways:

  • As fuel cell which is an electrochemical device that combines hydrogen and oxygen to produce electricity, with water and heat as by-products. The efficiency of such fuel cell is around 60 %.
  • As a combustion engines in very similar engines as the ones

Reducing cost and improving durability are the two most significant challenges to fuel cell commercialization. Fuel cell systems must be cost-competitive with, and perform as well or better than, traditional power technologies over the life of the system

[ For reference see https://hydrogeneurope.eu/hydrogen-applications and https://www.californiahydrogen.org/wp-content/uploads/files/doe_fuelcell_factsheet.pdf]

Hydrogen productions

Hydrogen is typically produced from water via electrolysis process. This is the exact inverse system as the one mentioned above as fuel cell. This process as a quite high efficiency of around 80%. Meaning that to produce 1kg of H2, which as an energy of 40kWh, 50–55kWh of electricity are needed.

This could therefore be an interesting solution to stabilize our electrical grid, and/or replace our fossil fuel transport industry.

Also, it must be mentioned that having a transport running on water is simply not possible. The best fuel cell used to generate hydrogen would consume as much energy from the required input electricity as produced energy in the form of hydrogen. [For reference see https://en.wikipedia.org/wiki/Water-fuelled_car]

Hydrogen storage

Typically, hydrogen can be stored in two ways:

  • As a compressed gas in high-pressure tanks.
  • As a liquid in cooled tanks (stored at -253°C).

In both cases, the gas needs to be highly compressed or cooled, which makes it very challenging for transport industry. Although various hydrogen storage technologies are presently available, none completely satisfies all of the auto industry requirements. In fact, finding a solution to the hydrogen storage problem is considered by many to be the foremost challenge for the hydrogen economy.

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