Hydrogen fueled forklifts started replacing battery-powered forklifts in warehouses. Several countries also started experimenting with Hydrogen-fueled buses (Foton & Mercedes Benz). Major automobile manufacturers around the globe started developing technologies for Hydrogen driven cars (Toyota Mirai/ Hyundai Nexo, Honda Clarity etc.). Railway companies also started experimenting with Hydrogen-fueled locomotives (e.g. China South Rail Corporation/ Alstom). Few cities also started experimenting with trams running on Hydrogen. Even Boeing and Airbus are now studying the feasibility of Hydrogen-fueled passenger planes while a Hydrogen-powered supersonic private plane is also under development. Interestingly, Hydrogen and Electricity are generally considered as opposite sides of the same energy. While Electricity (derived from any source) can be readily used to produce Hydrogen via electrolysis, Hydrogen can only be consumed to produce pollution-free electricity via a fuel cell.
Hydrogen has many unique characteristics that make it an ideal energy carrier such as (1) it can be produced from and converted into electricity at relatively high efficiencies; (2) one of its material to produce it is water (Interestingly water is again formed when Hydrogen is burned to generate electricity), and is available in abundance; (3) it is a completely renewable fuel; (4) it can be stored in gaseous form (convenient for large-scale storage), in liquid form (convenient for air and space transportation), or in the form of metal hydrides (convenient for surface vehicles and other relatively small-scale storage requirements); (5) it can be transported over large distances through pipelines and/ or via tankers; (6) it can be converted into other forms of energy in more ways and more efficiently than any other fuel (such as catalytic combustion, electrochemical conversion, and hydriding); and (7) it is environmentally friendly when produced from water using renewable energies since its production, storage, transportation, and end use do not produce any pollutants (except for small amounts of nitrogen oxides when it is burned with ambient air), greenhouse gases, or any other harmful effects on the environment.
Hydrogen Production & Classification: As stated above, since the Hydrogen is a secondary form of energy & hence needs to be produced using any of the primary energies, industry has created a set of colour codes to distinguish the type of Hydrogen being produced, based upon the process being followed to produce it, and the impact of those processes on the environment while producing the Hydrogen. The Green Hydrogen, which the present day’s buzz word in energy sector, is supposed to be produced using Green Energy6. Some of these colour coded are indicated in the chart below:
However, this colour coded nomenclature, is only used to facilitate the intellectual discussions, since as of now nothing has been standardized about them. It is high time that policy makers must come out with a universally accepted standard colour coding of Hydrogen, based on quantified measurement of greenhouse gas (GHG) emissions from each of the methods of generating Hydrogen, during their complete life-cycle. This is important as there are many processes of Hydrogen generation which certainly do not fully fall under one colour (e.g. mixed Hydrogen sources, electrolysis with coal based electricity).
Hydrogen can be produced using a variety of chemistries and utilizing energies derived from both renewable and nonrenewable sources, through many different processes, some of which are given in the next page.
However, in real world, till now the two widely used processes for commercial generation of Hydrogen have been in use, the reformation of natural gas and electrolysis of water (with multiple sources of electricity).
The recent rise of Hydrogen economy has revived the focus on the development of new Hydrogen technologies which are safe and affordable for generating, storing, distributing & utilizing Hydrogen as an alternative to fossil fuel. The initiative for development of these technologies to produce Hydrogen and its utilization are based on the premise that Hydrogen is in abundant supply on Earth. Still, since the most of the Hydrogen on Earth is not available as free gas, but is bonded either as hydrocarbons or water, which has no fuel value unless separated (this separation also needs energy), the major challenge related to Hydrogen has been, in its efficient & safe harnessing so that it could be used as fuel. At present, the Hydrogen production is a growing industry and in the year 2021 alone about 94.3 MMT of Hydrogen was produced, which in energy terms was equivalent to about 365.65 Million KL of Oil. It is worth noting that during the same year (2022) world had produced 5797.22 Million KL of Oil. Thus, Hydrogen forms a healthy 6.31% of overall global energy scene (however out of this 6.31% of hydrogen energy produced, 2.26% is used in the refineries, 1.38% is used in ammonia production while only the balance 1.38% was used in other areas including basic power system & mobility network). And with the CAGR of 11% the future certainly looks bright for this energy source. At present, Hydrogen is primarily consumed in two nonfuel uses: (1) about 60% to produce NH3 to produce fertilizers (2) about 40% in refinery, chemicals, and petrochemical sectors. If nonconventional resources, such as wind, solar, or nuclear power for Hydrogen production were available, the use of Hydrogen for hydrocarbon synfuel production could expand by 5- to 10-fold.
Hydrogen In Fuel Cell Vehicles (FCVs): Going back to history of Fuel cells, it was in 1839, when Sir William Graves first demonstrated the principle of fuel cell. However, it was the oil crisis in 1973 fastened the development of fuel cells in the search of the alternative energy sources especially for automobiles which were one of the largest consumers of petroleum fuel and thus the EVs with Fuel cells started gaining momentum as, even in this time, mass commercial production of Lithium Ion Cells (LICs) was about 20 years away7. Back then, there were only two commercially available batteries – the Lead Acid Batteries (LAB) and the Nickel Cadmium (NiCd) Batteries, having their own sets of challenges for applicability in the EVs. This prompted research into the development of improved Fuel Cells for future EVs. The Fuel Cell is an electrochemical device that combines Hydrogen with Oxygen to produce electricity, heat and water. In these fuel cells, rather than applying a periodic recharge, the Hydrogen, which is stored in a pressurized container, is supplied as a fuel while the Oxygen is drawn from the air and unlike IC Engines, the fuel cells do not generate energy through burning; but by electrochemical process. There are little or no harmful emissions. The only release is clean potable water (if burned with pure Oxygen) or a little bit of NOx (if burned with atmospheric air). There is no physical limit of energy generation except to the limit of storage of Hydrogen i.e. the tank capacity to store Hydrogen. In a way Fuel Cells are analogous to the ICEs where instead of Gasoline, Hydrogen is stored in the tank. Till date the cost of fuel cell technologies have been prohibitively high due to cost of rare earth & pure materials. Although some improvements were made in early 1990s, for improving the stack designs, which led to increased power densities thus reducing the cost of energy generation. Over the time, several variations of fuel cell systems have emerged. Nowadays, several types of fuel cells are being developed for a large number of commercial applications which, are summarized below:
The most common Fuel Cell system used in EVs and portable electronic is the Proton Exchange Membrane Fuel Cell (PEMFC) system as it allows compact designs and achieves a high energy to weight ratio. It also has an added advantage of getting quick start-up as soon as Hydrogen is supplied. The stack runs at a relatively comparatively lower temperature of about 80°C (176°F) & the efficiency is about 50% (in comparison, the ICEs operate at about 15% efficiency). However, the limitations of the PEMFC system are its high manufacturing costs and need for a complex water management system for its stack which contains Hydrogen, oxygen and water. Unfortunately, if this stack gets dry, the cell develops a high flow resistance for gases and then water must be added to get the system going. But, if slightly more water than what is needed, gets added, it causes flooding in the Fuel Cell, impacting its operations. The PEMFC also has a limited operating range of temperature. While, freezing water can damage the stack (hence additional heating elements are fitted to keep these fuel cell within an acceptable temperature range), if the warm up is slow, then the performance goes down. Disposal of heat is also a concern when the temperature rises too high. Due to these operational issues, the PEMFC requires a complex set of accessories e.g. compressors, pumps and other sub-systems, which on one side make PEMFCs physically complex, these sub-systems also consume about 30% of the energy generated. Although the stationary & uniformly loaded PEMFC stack which is made to run continuously has an excellent life of 40,000 hours, it is the intermittent start and stop conditions in EVs that leads to induce drying and wetting, causing membrane stress. These stresses on membrane, effectively reduce the effective service life of PEMFC in EVs by 1/10th to 4,000 hours (i.e. about 2 years of life if the EVs is made to run 6 hours a day). Similar to BEV (in which battery replacement cost is prohibitively high), replacement cost of the stack in FCEV is also very high. Despite the above said challenges associated with the PEMFCs, they are still being considered the most promising fuel cells for cars and light trucks.
There are 5 basic components of a FCEV which include:
- Fuel Cell Stack – An Aggregate Of Numerous Fuel Cells That Combine Oxygen And Hydrogen To Generate Electricity And Power The Electric Motor
- Fuel Tank – Hydrogen Gas Is Stored In
Carbon-Fiber Reinforced Tanks To Provide Fuel To The Fuel-Cell Stack - Electric Motor – Powers The Car Using Energy Produced In The Fuel Cell Stack
- Battery – Captures Energy From Regenerative Braking And Provides Additional Power To The Electric Motor
- Exhaust – The Byproduct Of The Reaction Occurring In The Fuel Cell Stack Is Water Vapour, Which Is Emitted Through The Exhaust
Challenges Of Fuel Cell EVs/ Cars: In 2008, Professor Jeremy P. Meyers, in the Electrochemical Society journal Interface wrote that fuel cells “are not as efficient as batteries, primarily due to the inefficiency of the oxygen reduction reaction… They make the most sense for operation disconnected from the grid, or when fuel can be provided continuously. For applications that require frequent and relatively rapid start-ups… where zero emissions are a requirement, as in enclosed spaces such as warehouses.” Also in 2008, Wired News reported that “experts say it will be 40 years or more before Hydrogen has any meaningful impact on gasoline consumption or global warming, and we can’t afford to wait that long. In the meantime, fuel cells are diverting resources from more immediate solutions.” In 2008, Robert Zubrin, the author of Energy Victory, said, “Hydrogen is just about the worst possible vehicle fuel”.
To be continued
- Though these fuel cells were conceived in the 19th century, powerful versions were not developed until 40 years ago. Unlike IC engines, these battery-like devices only produce pure water as their output while generating electricity.
- Though the term Green Energy Is used for the electricity/ energies being produced from the sources of nature but if you consider the complete life cycle of this energy which may use Wind mills, Solar panels etc. which may be impacting the environment at some stage of their own manufacturing. Hence in real terms, no energy can be said to be a completely Green Energy.
- It was in 1991, when Sony Energytec Inc. began producing first commercial Li-MnO2 cells (or the first LIC) based on the Asahi patents with “electronic safety circuitry” to control the charge-discharge cycle of LICs (with an interrupter to break current flow on buildup of excessive internal cell pressure) as well as also used a “shut-down” polymer separator.
Prabhat Khare holds BE (Electrical) & a Gold Medalist from IIT, Roorkee. He is an Automotive (EV) & Engineering Consultant, as well as a Technology Article Writer. He is a Certified Energy Manager (BEE) & Lead Assessor for ISO 9K, 14K, 45K & 50K. He can be reached at LinkedIn: https://www.linkedin.com/in/prabhatkhare2/.
