Renewable energy is playing an increasingly important role in addressing some of the key challenges facing today’s global society such as the cost of energy, energy security and climate change mitigation. Because energy storage is crucial for overcoming the inherent intermittency of renewable resources, chemical storage of energy can be achieved via Hydrogen (H2) or carbon-neutral Hydrogen derivatives such as Ammonia (NH3).
Hydrogen is a clean-burning molecule that could become a zero-carbon substitute for fossil fuels in hard-to-abate sectors of the economy. Combustion of Hydrogen (H2) only emits water vapor and warm air resulting in a true zero emission fuel. The combustion of Ammonia (NH3) in comparison, releases NOX which must be dealt with through some type of abatement system.
The climate advantage of hydrogen is though highly dependent on how it is produced. Grey hydrogen is made by extracting hydrogen from natural gas using thermal processes such as steam methane reformation. It offers little to no climate benefit. Blue hydrogen is made by extracting hydrogen from natural gas, and then using carbon capture and sequestration technology to store the remaining carbon. It has a low to moderate carbon intensity. Green hydrogen is made by extracting hydrogen from water using electrolysis powered by renewable energy. With the lowest carbon intensity, it offers the greatest climate benefit. The cost of producing hydrogen from renewables is primed to fall, but demand needs to be created to drive down costs and a wide range of delivery infrastructure needs to be built.
- Hydrogen is colourless as a liquid. Its vapours are colourless, odorless, tasteless, and highly flammable.
- Hydrogen exists as a liquid at -253°C. Materials stored at this low temperature can cause cryogenic burns or lung damage, so personal protective equipment is mandatory.
- Liquid hydrogen is noncorrosive. Special materials of construction are not required. However, because of its extremely cold temperature, equipment must be designed and manufactured of material that is suitable for extremely low temperature operation.
- Liquid hydrogen has a density of close to 71 kg/m3.
- The volume ratio of liquid to gas is 1:848.
- Hydrogen is stored and transported as a liquid or as compressed gas.
- Liquid hydrogen is transported at minus 253 degrees Celsius and a pressure of 1-4 bar.
- Once liquefied, it can be maintained as a liquid in pressurized and thermally insulated containers.
- Pressurised hydrogen is transported in standardized containers at 250-350 bar.
- The low density of hydrogen makes it considerably harder to store than fossil fuels while also making it expensive to transport via road or ship.
- Green hydrogen has the potential to play a role in multiple applications, and can be used through direct combustion or by chemical reaction in a fuel cell.
- The potential uses are vast, ranging from decarbonization of industrial processes such as fertilizers, methanol, chemical feedstock etc, as power for heavy industry such as steel and cement production, as fuel for the transportation sector, for the residential sector and as storage of renewable energy.