Green Hydrogen as a Mobility Solution
Hydrogen has emerged as a promising clean transportation fuel option. With high efficiency, fast refuelling capabilities, and zero tailpipe emissions in fuel cells, hydrogen-powered vehicles can offer sustainability without compromising on performance. However, realizing hydrogen's potential requires building out refuelling infrastructure and overcoming technical hurdles like storage density. With countries like India taking steps to develop hydrogen infrastructure, the path forward looks promising for hydrogen energy to decarbonize the transport sector.
Hydrogen as an Alternative Fuel
Hydrogen is seen as a promising alternative transportation fuel. It can power fuel cells in zero-emission vehicles with great efficiency and fast refuelling times. Hydrogen fuel cell vehicles are two to three times more efficient than gasoline vehicles. Domestically-produced hydrogen could also provide energy independence. However, hydrogen technology faces challenges like low volumetric density that requires compressed storage and high-pressure tanks.
The energy in 1 kilogram of compressed hydrogen gas provides a similar driving range as 2.8 kg of gasoline. But volumes take up more space. Automakers use high-pressure 700 bar tanks to achieve standard vehicle range. Hydrogen refuelling stations can fill these up in 3-5 minutes. Buses utilize lower-pressure 350 bar tanks that need 7-10 minutes to refill. Materials innovations like metal hydrides and sorbent materials aim to store hydrogen more densely without high pressures.
Hydrogen Engines and Fuel Cell Electric Vehicles (FCEV)
Hydrogen internal combustion engines and hydrogen fuel cells can power vehicles using hydrogen, a zero-carbon fuel.
Hydrogen engines burn hydrogen in an internal combustion engine, in just the same way petrol/diesel is used in an engine. Hydrogen internal combustion engines (Hydrogen ICE) are nearly identical to traditional spark-ignition engines. Internal combustion engines tend to be most efficient under high load—which is to say when they work harder. So, for heavy trucks that tend to spend most of their time hauling the biggest load they can pull, internal combustion engines are usually the ideal and efficient choice. Hydrogen engines release near zero, trace amounts of CO2 (from ambient air and lubrication oil), but can produce nitrogen oxides or NOx. As a result, they are not ideal for indoor use and require exhaust aftertreatments to reduce NOx emissions.
Fuel cell electric vehicles (FCEVs) generate electricity from hydrogen in a device known as a fuel cell and use that electricity in an electric motor much like an electric vehicle. FCEVs are most efficient at lower loads. Vehicles that frequently operate with less load—tow trucks or concrete mixer trucks, for example, may be more efficient with a fuel cell. Fuel cell electric vehicles can also capture energy through regenerative braking in very transient duty cycles, improving their overall efficiency. FCEVs produce no emissions at all besides water vapour. This is a very attractive feature for vehicles operating in closed spaces or spaces with limited ventilation.
Hydrogen Refueling Stations (HRS)
Hydrogen refuelling stations (HRS) function similarly to conventional petrol stations, but supply hydrogen fuel at high pressure. HRS can be divided into off-site stations, where hydrogen is delivered via pipeline or truck, and on-site stations that produce and compress hydrogen on location. Typically, HRS source their hydrogen from electrolyzers that produce low-pressure hydrogen of around 30 bar, pipelines supplying medium-pressure hydrogen of 50-80 bar, or delivery of compressed hydrogen between 200-500 bar. The components of an HRS include hydrogen storage tanks, gas compressors to reach vehicle fueling pressures, pre-cooling systems, and hydrogen dispensers. There are two standards for fueling pressure - H35 dispenses at 350 bar and H70 at 700 bar. In India specifically, there are currently a few hydrogen stations in operation, such as at Indian Oil's R&D Center, NTPC Leh, and the National Institute of Solar Energy. Two additional stations are underway by NHPC in Leh and Chamba as the country's hydrogen infrastructure builds out.
Conclusion
Hydrogen shows exceptional promise as a sustainable fuel to drive the decarbonization of the transport industry. Technical aspects like storage density and lack of comprehensive infrastructure remain challenges to be tackled. However the complementary efficiency and emissions profiles of hydrogen internal combustion engines and hydrogen fuel cell electric vehicles open doors for optimization across many transportation applications. As major industries and countries like India make inroads into building hydrogen refuelling stations, the path for adoption seems optimistic. With continued innovation on materials for better storage alongside supply chain and policy initiatives to support infrastructure development, hydrogen can emerge as a leading player in the clean energy mix powering greener mobility. The unique versatility it provides means hydrogen is likely to drive the future of transportation.