Aurelia Turbines and hydrogen

Aurelia Turbines develops and produces small gas turbines that can run on a variety of fuels. One of these fuels is hydrogen.

What is hydrogen?

• Hydrogen is the most common and lightest element, making up 90% of the atoms in the universe.
• There would be no life without the energy produced by hydrogen. The sun shines because hydrogen atoms fuse into helium in its core.
• At atmospheric pressure and room temperature, hydrogen is colourless, odourless, tasteless, flammable, and considerably lighter than air. It occurs in nature as diatomic molecules (H₂).
• The best-known hydrogen compound is water formed by hydrogen and oxygen with the molecular formula H₂O.

Why hydrogen?

• The use of hydrogen as a fuel to generate electricity and heat or in industrial processes is always clean. When hydrogen is burned, the only emission is pure water as steam.
• Hydrogen can be stored as a gas or liquid in much the same way as natural gas. Existing storage facilities for natural gas are not suitable for 100% hydrogen, but solutions are being developed. Hydrogen stored in this form can be used when electricity and heat are needed.
• Hydrogen, mixed with natural gas, can be transported in existing natural gas pipelines, to a limited extent. This reduces the need to construct an expensive system for transferring and storing energy. Older pipes can withstand the addition of hydrogen, but only a fraction of the total amount of gas. However, newer pipes can carry a gas mixture of up to more than 50% hydrogen. At the destination, the hydrogen–natural-gas mixture can be burned or the hydrogen can be separated from the natural gas.
• Hydrogen can also be transported, like natural gas, onboard a ship in liquefied form or in combination with nitrogen to form ammonia. In addition, new technologies are being developed to transport hydrogen, for example, as part of a unique liquid hydrocarbon mixture (LOHC). The development of hydrogen transportation opportunities will allow hydrogen to be produced cost-efficiently in sunny countries and then transported to the northern industrialised countries.

Where should hydrogen be used?

• The most efficient way to generate and use electricity is to do that locally: the energy losses are the lowest.
• Hydrogen is a viable option in local power plants and in situations where there is no reliable electricity grid.
• In combined heat and power (CHP) plants, fossil fuels can be replaced entirely by hydrogen.
• In industry, temperature requirements can be very high and, therefore, virtually impossible to achieve with electricity. Producing the steam needed by industry with electricity alone, for example, is problematic, not to mention other industrial processes. To obtain the high temperatures, fossil fuels are used but can be replaced by clean hydrogen.
• Wind and sunshine vary. On windy and sunny days, electricity can be generated beyond the current need, providing a surplus that can be used to produce hydrogen. The resulting hydrogen can then be used for electricity on calm nights and cloudy days. Hydrogen can thus be the balancing power required by renewable energy sources.
• In many countries – such as Germany – there are not enough power lines to transfer all the electricity from wind farms to industrial areas. When wind power is applied to hydrogen production, the hydrogen can then be mixed with natural gas and transferred using existing gas pipelines, resulting in significant cost savings.
• In small passenger cars, battery power is often more efficient than hydrogen fuel. However, heavy commercial vehicles and buses that travel long distances require batteries too large to fit in the vehicles, hydrogen may be a better-suited energy source.
• New technical solutions are being developed for the use of hydrogen in ships and aircraft to reduce emissions.
• Various synthetic, carbon-neutral fuels can be prepared by combining captured carbon dioxide with hydrogen. Such fuels are largely suitable for existing internal combustion engines.

How to produce hydrogen?

• Hydrogen can be produced from pure water with electricity. In this case, electricity breaks down water molecules into hydrogen and oxygen – a method called electrolysis. The only emissions from electrolysis are the elements in the water molecules, i.e. hydrogen and oxygen.
• Electrolysis requires a large amount of electricity. From the point of view of hydrogen production technology, electricity can be produced by any method.
• If the electricity for electrolysis is produced by wind, solar or other renewable energy, the end result is green hydrogen. In this case, the generation of electricity to produce hydrogen does not generate greenhouse gas emissions. Interest in green hydrogen has grown significantly as the price of renewable energy has fallen sharply around the world.
• Electricity for hydrogen production can also be produced with nuclear energy without greenhouse gas emissions. France, for example, is rich in nuclear power and also considering the production of hydrogen from nuclear power.
• At present, hydrogen is mainly produced from natural gas and oil, as well as by gasifying coal for hydrogen production from water vapour. It is produced for the needs of the fertiliser industry, for example. A significant amount of carbon dioxide is a by-product of the current processes, which is released into the air, causing a greenhouse effect.
• Hydrogen can also be produced directly from natural gas by methods that allow coal to be recovered as a solid and utilised as an industrial raw material. For example, graphite, a form of carbon used in pencils, can be obtained in this manner, rather than mined from the ground.

What are the challenges of hydrogen?

• Hydrogen-containing gases burn too hot and fast for use in conventional engines and turbines. In a turbine, the nozzle injects fuel into a combustion chamber where the mixture of air and fuel burns. If pure hydrogen were used in the turbine with conventional natural gas nozzles, the nozzle would melt because combustion would occur too close to the nozzle.
• Hydrogen burns about ten times faster than other fuels, which can cause an explosion if the hydrogen is not handled properly.
• Although hydrogen carries a considerable amount of energy for its weight, there is little energy per unit volume compared to fossil fuels. For example, natural gas is almost entirely methane, with an energy density roughly three times that of hydrogen. Therefore, compared to natural gas, a larger volume of hydrogen is needed to achieve the same amount of energy.
• Hydrogen can pass through steel even at room temperature. It can weaken steel by introducing microscopic cracks in the steel. The structures carrying hydrogen must also withstand the high pressure of the gas. Therefore, many ordinary steel structures are not suitable for hydrogen storage.

Why can Aurelia's turbines use hydrogen?

• The structure of a gas turbine is different from that of a reciprocating engine. The expansion brought about by thermal energy is a continuous process in a turbine, unlike reciprocating engines. Rapid combustion of hydrogen can damage or restrict a reciprocating engine, but a well-designed turbine can withstand the loads.
• Aurelia is able to use various fuels in their turbines because of the modular design, having separate, interchangeable parts. The combustion chamber, in which the fuel burns, is separate from the rest of the machinery. Changes in the combustion chamber – such as length, volume or internal airflow adjustments – do not affect the other components of the turbine. In this way, hydrogen can be used with relatively minor modifications to generate electricity or heat with Aurelia gas turbines.
• Aurelia Turbines is the first company in the world to utilise the IRG2 process in its gas turbines. IRG2 stands for “intercooled and recuperated, generator on both shafts”. An intercooler lowers the temperature of the supply air heated by a supercharger, i.e. a compressor, with outside air or water. An internal heat exchanger recovers, or recuperates, waste heat. In the IRG2 process the supercharging and the turbine processes take place in two stages.