Despite most of us seeing fuel cells as the future, the basic principles are not new. Hydrogen (H2) and energy have a long shared history – powering the first internal combustion engines over 200 years ago to becoming an integral part of the modern refining industry .
When Henry Cavendish first isolated and characterized hydrogen in 1766 he called it inflammable air. Years later, Antoine-Laurent Lavoisier named it hydrogen and began a new programme of research on the decomposition (as well as the synthesis) of water. At that time, he was providing additional and decisive proof that water was a compound composed of hydrogen and oxygen in fixed proportions by weight, and he was investigating the possibility of a new source of inflammable air for ballooning.
It was right after these experiments that a gas was produced in large-scale for the first time when hydrogen-filled balloons were used for military purposes during the French Revolution . The most common process used to produce hydrogen at that time was the iron contact process where steam was passed over red-hot iron. Even after World War I, when hydrogen was being used in large quantities in the recently developed Haber process and in the hydrogenation of oils, its use as a fluid to inflate balloons and airships remained the main industrial use of this gas.
In 1839, British physicist William Grove suggested that if electricity could split water into hydrogen and oxygen, it should also work in reverse – combining hydrogen and oxygen should give electricity – and he built the world’s first fuel cell to prove it. At the University of Cambridge, UK, in the 1940s and 1950s, Thomas Bacon resurrected and refined the technology that had changed little since Grove’s work. Bacon successfully developed a 3kW fuel cell powered by hydrogen and oxygen and, eventually, an improved version of this cell was used to power NASA’s Apollo space vehicles .
But NASA was also working to develop fuel cell technology of its own. The proton exchange membrane (PEM) fuel cell was used during the Gemini space project and it is mainly this technology or a variation of it, that is being put into cars today. The main difference between PEM and alkali fuel cells is that PEM cells can use air directly, whereas its predecessors had to use pure – or nearly pure – oxygen.
In today’s fuel cells, as in Grove’s ’gas battery’, hydrogen and oxygen can be combined to form water and give electrical energy, but over the years the technology has changed somewhat.
1.2 What is Hydrogen used for?
Approximately 50 million metric tons of hydrogen are produced globally each year . Hydrogen is an energy carrier that can be used to store, move, and deliver energy produced from other sources. It can be used for power generation in places where it is difficult to use electricity or as a CO2 neutral feedstock for chemical processes — e.g. ammonia-fertilizers. Hydrogen can fuel cars, power trucks, and ships and be a key raw material for refineries, chemical plants, and steel mills — sectors where it is proving difficult to meaningfully reduce CO2 emissions.
Today, we primarily use hydrogen for oil refining and ammonia production, but there is a growing demand for it in steel manufacturing and transportation to power vehicles, upgrade biofuels, and even produce synthetic fuels that may use carbon dioxide as a feedstock. The provision of back-up power and off-grid electricity is today often still dominated by diesel generators. Hydrogen fuel cells represent a possible alternative, in many cases reducing local air pollution as well as the need for imported diesel in non-oil-producing countries .
These multiple uses can be grouped into two large categories:
Hydrogen as a feedstock. A role whose importance is being recognized for decades and will continue to grow and evolve.
Hydrogen as an energy vector enabling the energy transition. The usage of hydrogen in this context has started already and is gradually increasing. In the coming this field will grow dramatically. The versatility of hydrogen and its multiple utilization is why hydrogen can contribute to decarbonize existing economies.
Hydrogen’s role in the decarbonization process can be summarized as shown in the graph below:
In the energy field, most hydrogen is used through Fuel Cells (FCs). A fuel cell is an electrochemical device that combines hydrogen and oxygen to produce electricity, with water and heat as by-products. In its simplest form, a single fuel cell consists of two electrodes – an anode and a cathode – with an electrolyte between them .
1.3 How is Hydrogen generated?
Hydrogen is the most abundant element on earth but it rarely exists alone, therefore it is produced by extracting it from its compound. It can be produced in numerous ways, some methods produce CO2 while others are carbon-free.
Hydrogen is also the lightest gas we know, but under high pressure, it does have a high energy density of 120 megajoules (MJ) per kg. That is almost three times as much as natural gas (45 MJ per kg). Pressurising — compressing — hydrogen gas, however, also requires the necessary energy (about 10%) .
Hydrogen can be extracted from a variety of sources, such as natural gas, nuclear power, biomass, and from water with the aid of electricity. Natural gas, via steam methane reforming (SMR), is currently the primary source of hydrogen production, accounting for around three-quarters of the annual global dedicated hydrogen production , and up to 95% in the United States . SMR is a mature production process in which high-temperature steam (700°C–1,000°C) is used to produce hydrogen from a methane source, such as natural gas.
Firstly, methane reacts with steam under pressure in the presence of a catalyst to produce hydrogen, carbon monoxide, and a relatively small amount of carbon dioxide. This step is endothermic—that is, heat must be supplied to the process for the reaction to proceed. Subsequently, the carbon monoxide and steam are reacted using a catalyst to produce carbon dioxide and more hydrogen. In a final step, carbon dioxide and other impurities are removed from the gas stream, leaving essentially pure hydrogen.
Step 1. Steam-methane reforming reaction
CH4 + H2O (+ heat) → CO + 3H2
Step 2. Water-gas shift reaction
CO + H2O → CO2 + H2 (+ small amount of heat)
Steam reforming can also be used to produce hydrogen from other fuels, such as ethanol, propane, biofuels, gasified coal, or even gasoline. Reforming low-cost natural gas can provide hydrogen today for fuel cell electric vehicles (FCEVs) as well as other applications. Over the long term, experts expect that hydrogen production from natural gas will be augmented with production from renewable, nuclear, coal (with carbon capture and storage), and other low-carbon energy resources .
Electrolysis is the process of using electricity to split water into hydrogen and oxygen and is a promising option for hydrogen production from renewable resources. To date, only small amounts of hydrogen have been generated from renewable energies, although that amount is set to increase in the future.
Like fuel cells, electrolysers consist of an anode and a cathode separated by an electrolyte. Their specific functioning depends on the different types of electrolyte material involved: in a polymer electrolyte membrane (PEM) the electrolyte is a solid specialty plastic material, alkaline electrolysers use a liquid alkaline solution of sodium or potassium hydroxide, solid oxide electrolysers use a solid ceramic material .
Hydrogen produced via electrolysis can result in zero greenhouse gas emissions, depending on the source of the electricity used.
1.4 Where it comes from is important: the Colour of Hydrogen
The colours of hydrogen act as useful markers for telling us how the gas was produced and hence, allow us to evaluate their downsides compared to the advantages the final product can provide.
Grey hydrogen is produced industrially from natural gas generating significant carbon emissions. This is, by far, the dominant type of hydrogen up to date, over 70% of the world’s H2 is grey.
Brown hydrogen and black hydrogen are variants of the aforementioned, the first comes from brown coal, also known as Lignite, while the latter is produced from black coal . The ‘gasification’ of coal creates a synthesis gas (syngas), which is then cleaned in conventional ways to recover the hydrogen but that then leaves a considerable volume of greenhouse gases to deal with. These types constitute around 30% of the current hydrogen production.
Blue hydrogen – or low carbon hydrogen – is a cleaner version, for which 80-90% of the carbon emissions are captured and stored, or reused. This is also called CCS Carbon – Capture & Storage – and only happens in empty gas fields under the North Sea on a large scale.
Green hydrogen is obtained from renewable energy. It avoids carbon emissions in the first place and has the potential to help with the variable output from renewables, like solar photovoltaics (PV) and wind, whose availability is not always well-matched with demand.
Turquoise hydrogen is produced from natural gas using the so-called molten metal pyrolysis technology. Natural gas is passed through a molten metal that releases hydrogen gas as well as solid carbon. The latter can find a useful application in, for example, car tyres. It must be outsourced that this technology is still in the laboratory phase and it will take at least ten years for the first pilot plant to be realised .
2 WHAT IS DRIVING THE DEVELOPMENT OF HYDROGEN FUEL
As governments develop specific hydrogen strategies, growing industry associations provide further evidence that something truly different is happening with hydrogen. More industry players are recognising hydrogen’s versatility and falling cost, enabling investments in a growing range of sectors. The following figure lists all the drivers and indicators for hydrogen’s growing momentum :
Source: Path to Hydrogen Competitiveness: A Cost Perspective. Hydrogen Council
2.1 Latest technologies
The future of hydrogen fuel lies with the fuel cell. The following schematic diagram represents the basic components and flows occurring in a typical fuel cell:
A fuel cell is similar to a battery in that it generates electricity from electrochemical reactions. The essential difference, however, relates to how energy is provided to the cell. In the case of a battery, both the energy-out and the energy-in take the form of electricity, but in the case of a fuel cell—while the useful energy-out is primarily electricity, the energy-in is provided by a fuel, such as hydrogen. A key issue with fuel cells is fuel purity and different fuel cell technologies have different abilities to cope with variable fuel quality .
PEM Fuel Cells
The proton exchange membrane (PEM) uses a solid proton exchange membrane as the electrolyte, either side of which is a platinum catalyst. Hydrogen is oxidised by the anode catalyst giving electrons and protons that migrate through the membrane to the cathode. Here the protons react with oxygen molecules and the electrons, producing water. The movement of electrons from one side of the fuel cell to the other provides the current that can be used to drive a car, i.e. a Fuel Cell Electric Vehicle (FCEV).
Today, PEM fuel cells operate at around 55 per cent efficiency, compared to an average of around 18-20 per cent for a conventional internal combustion engine. The cells are also able to vary their output quickly, and so are suited for transport applications where quick start-up and high power are needed .
One of the problems with membrane-based fuel cells is that they need to run at relatively low temperatures (<80°C) to prevent dehydration, thus lowering the efficiency of the catalysts. Moreover, the two platinum catalysts are pricey and that’s where a lot of current research is focused. One of the approaches used to reduce platinum cost in fuel cells is making core-shell catalysts, with the expensive platinum coating a cheaper nanoparticle made of earth-abundant transition metals (Fe, Co, Ni, and Cu) with low cost and good catalytic performance .
PAFCs, MCFCs, and SOFCs
Phosphoric acid fuel cells are based on phosphoric acid as electrolyte, and are used today as stationary power generators with outputs in the 100–400 kW range. In addition to electricity, they also produce heat at around 180°C, with potential uses for space and water heating.
Molten carbonate fuel cells (MCFCs) and solid oxide fuel cells (SOFCs) operate at higher temperatures, 600°C and 800–1 000°C respectively . MCFCs are used in the MW scale for power generation (due their low power density, resulting in a relatively large size). The produced heat can be used for heating or cooling purposes in buildings and industrial applications. SOFCs have similar application areas, often at smaller scale in the kW range, such as micro cogeneration units or for off-grid power supply.
Innovators at NASA’s Glenn Research Center have developed a novel SOFC with five times the specific power density of currently available SOFCs. It consists of a bi-electrode supported cell (BSC) manufactured with an innovative ceramic fabrication method that replaces commonly used metal interconnects (such as steel or platinum) with ceramic interconnects .
Hydrogen Fuel Cell vs. Battery Electric Vehicles
Fuel cells and battery-powered vehicles (BEVs) — a.k.a. electric vehicles — are working towards the same aim, and are complementary. Some suggest a portfolio approach: batteries, with their limited range and long recharge time, are best suited to small cars and short trips, with fuel cell vehicles for long drives and larger cars .
Nonetheless, many specialists think at the moment, looking at the technical and economic analysis, that electric vehicles are the most promising option to decarbonise transport in the short-term. This may be due the overall efficiency process from the electricity generation to the use of the car being better in BEVs than for the multiple conversion processes of FCEVs. Moreover, the cost of hydrogen refuelling infrastructure per vehicle is initially three to four times higher than for BEVs.
In favour of FCEVs, it must be outsourced that their autonomy is much higher — 500+ km; they can be refuelled/refilled much faster — under 5 min; the business model and operation of a hydrogen infrastructure is the same as for a current gas station — this means infrastructure can be built on existing gasoline distribution and retail infrastructure, creating cost advantage, preserving jobs and capital assets; the current value chain and corresponding jobs are safeguarded; a much higher energy density of the hydrogen storage system (compared to batteries), the sensitivity of the FCEV powertrain cost and weight to the amount of energy stored (kWh) is low. This means that as the range, the weight or the volume to be transported grow in importance, the value proposition of FCEV increases. This is specifically important for Heavy-duty vehicles as the increased required amount of hydrogen for these applications is much less than the number of batteries needed as their requirement means that the increased number of batteries in a truck would be linear .
If one asks anyone today what the future of cars looks like, they’ll probably answer it’s electric and that Tesla is at the forefront of the movement. But if and when fuel-cell vehicles scale, Tesla and other BEVs will have a tough challenge: they’ll have to increase range while simultaneously decreasing recharging time and price. On the other side, for FCEVs to become the breakthrough that automotive executives believe in, a vast network for hydrogen stations is vital .
2.2 Low-Carbon Energies and Climate Change
Most hydrogen on the market today is made from natural gas reforming. Although hydrogen produces no direct emissions of pollutants or greenhouse gases, its production is responsible for CO2 emissions of around 830 million tonnes of carbon dioxide per year, equivalent to the CO2 emissions of the United Kingdom and Indonesia combined .
As the world moves to a low-carbon future, hydrogen offers diverse applications as an energy carrier and chemical feedstock and has great potential to support decarbonisation of the world’s energy and industrial sectors. The EU objective of reducing emissions by 80–95% by 2050 compared to 1990 levels, for example, implies almost complete decarbonisation of power generation and high levels of variable renewables (VRE).
Because of this, there is a growing global demand for renewable and low-emissions hydrogen. One pathway for producing green renewable hydrogen is shown below:
Source: Western Australian Renewable Hydrogen Strategy 
Is hydrogen the perfect energy storage medium for variable-output renewables?
There is a major concern with hydrogen — where it comes from. Most hydrogen at the moment comes from refining methanol or electrolysis of water, so the power from that should be renewable — otherwise, the emission problem is just being transferred to a different part of the chain. Many argue that hydrogen is the perfect energy storage medium for wind power, with its variable output, producing truly green hydrogen for chemical energy storage.
Achieving a decarbonised electricity supply still faces major economic and technical challenges, in particular in the integration of variable renewable power output. Hydrogen-based fuels are also options for large-scale and long-term energy storage to balance seasonal variations in electricity demand or variable renewable power generation. Also, among the alternative energy sources for the transport sector, hydrogen shows the best performance for the environmental and social bottom line when renewable electricity is employed for hydrogen production .
In electricity systems with increasing shares of VRE, surplus electricity may be available at low cost. Producing hydrogen through electrolysis and storing the hydrogen for later use could be one way to take advantage of this surplus electricity. Yet, if surplus electricity is only available on an occasional basis it is unlikely to make sense to rely on it to keep costs down .
So, in the long term, with very high VRE shares, there is a need for large-scale and long-term storage for seasonal imbalances or longer periods with no generation. This should be achieved in combination with long-distance trade to take advantage of seasonal differences in global renewable supply.
Could hydrogen help save nuclear energy?
Hydrogen production via electrolysis is being pursued for renewable (wind) and nuclear energy options. These pathways result in virtually zero greenhouse gas and criteria pollutant emissions. However, over the last decade, nuclear units have been shut down prematurely with others currently scheduled for early retirement worldwide, mainly due to lack of market value and socio-political concerns. This is a particularly important trend in the United States, Japan, and Western Europe.
With the rise of more renewables coming onto the grid, many utilities are considering a hybrid or integrated systems approach to improve the economics for baseload energy sources like nuclear reactors . One opportunity is to utilize nuclear thermal heat and electricity to produce hydrogen. Existing nuclear plants could produce high-quality steam at lower costs than natural gas boilers and could be used in many industrial processes, including steam-methane reforming. However, the case for nuclear becomes even more compelling when this high-quality steam is electrolysed and split into pure hydrogen and oxygen.
Solid oxide electrolysers are a good match for atomic energy. They must operate at temperatures high enough for the solid oxide membranes to function properly (about 700°–800°C, compared to PEM electrolysers, which operate at 70°–90°C, and commercial alkaline electrolysers, which operate at 100°–150°C). The solid oxide electrolyser can effectively use heat available at these elevated temperatures (from various sources, including nuclear energy) to decrease the amount of electrical energy needed to produce hydrogen from water .
These processes would allow utilities to produce and sell hydrogen regionally as a commodity in addition to providing clean and reliable electricity to the grid. By extending the life of the commercial fleet, it will give the industry time to bring new advanced reactors online. Advanced reactors are expected to operate at considerably higher temperatures and would allow nuclear plants to more efficiently produce hydrogen to dramatically scale-up the industry.
Also, hydrogen-based chemistry could serve as a carbon sink and complement or decarbonize parts of the petrochemical value chain. Today, crude oil (derivatives) are used as feedstock in the production of industrial chemicals, fuels, plastics, and pharmaceutical goods.
If the application of carbon capture and utilization (CCU) technology takes off (as part of a circular economy or an alternative to carbon storage), the technology will need green hydrogen to convert the captured carbon into usable chemicals like methanol, methane, formic acid, or urea. This use of hydrogen would make CCU a viable alternative for other hard-to-decarbonize sectors like cement and steel production .
2.4 Air Quality
Cleaning the air and improving health is feasible with hydrogen fuel-cell vehicles. Nitrogen and sulphur oxides (NOx, SOx) and particulate matter enter the bloodstream and lungs and are at the root of the cause of many deceases in big urban agglomerations. It is therefore important to tackle one of the main causes of these issues at city but also rural level: the transport sector 
Concerning FCEVs, petroleum use and emissions are lower than for gasoline-powered internal combustion engine vehicles. The only product from an FCEV tailpipe is water vapor but even with the upstream process of producing hydrogen from natural gas, the total greenhouse gas emissions are cut in half and petroleum is reduced over 90% compared to today’s gasoline vehicles .
Using hydrogen instead of carbon-containing fuels in energy end uses could also reduce local air pollution, improving environmental and health outcomes. Urban air pollution concerns and its related health impacts are now major drivers of energy policy decisions, and governments are keenly interested in ways of reducing air pollution and improving air quality. When used in vehicles and heating appliances, hydrogen does not produce particulates or sulphur oxides or raise ground-level ozone. When used in a fuel cell, hydrogen does not produce nitrogen oxides .
Hydrogen-powered vehicles can bring significant environmental benefits to transport, society, and the wider energy system. A new study found that if EVs replaced only 25% of combustion-engine cars currently on the road, the United States would save approximately $17 billion annually by avoiding damages from climate change and air pollution. Wind offers the greatest potential health benefits and could save thousands of lives annually .
3 THE MAIN CHALLENGES
Until now, the cost of producing hydrogen energy has put it out of reach for everyday use. Although renewable hydrogen for transport, industry, and export is a key opportunity for many countries, it will not occur without significant investment and lead times. According to the economics, scaling up the hydrogen value chain will be the biggest driver to unlock further cost reductions in the future.
Scaling up manufacturing is a proven way to reduce costs for many hydrogen applications where costs of end-use equipment comprises a large component of Total cost of ownership (TCO) — e.g. fuel cells and tanks in transportation. The scale in manufacturing of equipment would account for up to 70 percent of this reduction . Around USD 70 billion of investment from various sources will be needed to reach scale, this accounts for less than 5% of annual global energy spend. In transport, the refuelling and distribution networks required and the cost differential for fuel cells and hydrogen tanks compared with low-carbon alternatives imply an additional required investment of USD 30 billion to cover the economic gap.
Governments hold the key to enabling investment. Eighteen countries and a number of regions and provinces, whose economies account for 70% of global GDP, have developed detailed strategies for deploying hydrogen energy solutions. The Western Australian Government is such an example, it will establish a $10 million Renewable Hydrogen Fund to facilitate private sector investment and leverage financial support to the renewable hydrogen industry .
Likewise, the U.S. Department of Energy announced it will provide up to $30 million for cost-shared research and development projects focused on small scale solid oxide fuel cells. The funding seeks to develop advanced technologies which can take the small scale SOFC hybrid systems by using solid oxide electrolyzer cell technologies. Also in the U.S, H2@Scale is a concept from the Department of Energy that explores the potential for wide-scale domestic hydrogen production and utilization to enable resiliency of the power generation and transmission sectors. In 2020 has secured funding for 18 projects that will support the next round of research, development, and demonstration activities under H2@Scale’s multi-year initiative to fully realize hydrogen’s benefits across the economy .
As the market grows for hydrogen fuel cell electric vehicles, so does the need for a comprehensive hydrogen fueling infrastructure. Refineries, chemical plants, and steel mills — sectors where it is proving difficult to meaningfully reduce CO2 emissions and thus are future consumers of hydrogen — tend to cluster at major industrial ports, offering an opportunity to build combined infrastructure and thus complementarity in hydrogen solutions. The development of combined solutions can create a virtuous cycle that makes other hydrogen applications viable, reducing the costs of each individual application.
Cost improvement depends on the scale-up of demand and the associated increase in utilisation of distribution infrastructure. For example, through an increase in trucking capacity, an increase in size and density of refuelling infrastructure, storage tanks, liquefaction and regasification plants, and conversion and reconversion plants are limiting factors that need to be addressed within the next 5-10 years.
3.3. Efficiency in the supply chain
All energy carriers, including fossil fuels, encounter efficiency losses each time they are produced, converted or used. In the case of hydrogen, these losses can accumulate across different steps in the value chain. This makes hydrogen more “expensive” than electricity or the natural gas used to produce it.
Hydrogen-based storage options also suffer from low round-trip efficiency: in the process of converting electricity through electrolysis into hydrogen and then hydrogen back into electricity, around 60% of the original electricity is lost, whereas for a lithium-ion battery the losses of a storage cycle are around 15%. Pumped-hydro storage facilities and batteries offer alternatives, although the latter are unlikely to be used for long-term and large-scale storage .
Uncertainty remains about the most effective type of carrier for shipping hydrogen, with much scope for thorough investigation of the options and improvement of efficiency and capital costs. Liquefaction efficiency, boil-off management, scalability and the efficiency of the cooling cycle require improvement. Publicly funded research efforts might focus primarily on key cost components, such as fuel cell durability and recycling, on-board storage options and electrolyser efficiency.
3.4 Water supply sustainability for electrolysis
Around 9 litres of water are needed to produce 1 kgH2 producing 8 kilograms of oxygen as a by-product. If all of today’s dedicated hydrogen production of around 70 MtH2 were to be produced by electrolysis, this would result in a water demand of 617 million cubic metres, which would correspond to 1.3% of the water consumption of the global energy sector today  or roughly twice the current water consumption for hydrogen from SMR.
Freshwater access can be an issue in water-stressed areas. Using seawater could become an alternative in coastal areas. Using reverse osmosis for desalination requires a manageable electricity demand and its costs have only a minor impact on the total costs of water electrolysis. Direct use of seawater in electrolysis currently leads to corrosive damage and to the production of chlorine, but research is looking at how to make it easier to use seawater in electrolysis in the future.
3.5 Public perception
So what of the safety concerns of having a pressurised gas cylinder in the back of your car? Experts believe there are no such issues, but public perception is another thing. For that reason, hydrogen entrepreneurs are trying very hard to convince the public that it is safe. They believe hydrogen is safer than the fuel we currently use to power our cars. Carbon-based fuels tend to spread as liquids. When it burns, conventional fuel produces hot ash, creating radiant heat. This isn’t the case with hydrogen. In its pure form, hydrogen burns no carbon and produces no hot ash and very little radiant heat .
Likewise, If hydrogen needs to be shipped overseas, it generally has to be liquefied or transported as ammonia or in liquid organic hydrogen carriers (LOHCs). For distances below 1 500 km, transporting hydrogen as a gas by pipeline is likely to be the cheapest delivery option; above 1 500 km, shipping hydrogen as ammonia or an LOHC is likely to be more cost-effective. These alternatives may also sometimes give rise to safety and public acceptance issues .
There is also a lot of work to be done within the framework of ISO/TS 19880-1:2016 standard that recommends the minimum design characteristics for safety and, where appropriate, for the performance of public and non-public fuelling stations that dispense gaseous hydrogen to FCEV.
4 CURRENT STATUS & FUTURE PROSPECTS
4.1 Hydrogen Fuel in the World
The technology is working and being pushed by car manufacturers, start-ups, universities, and governments. Supplying hydrogen to industrial users is now a major business around the world. Globally, this industry is dominated by a set of competing industrial companies comprising: Air Products and Chemicals Inc. (USA), Air Liquide (France), Linde AG (Germany) incorporating BOC Ltd (UK), and Praxair (USA) . Demand for hydrogen continues to rise – almost entirely supplied from fossil fuels, with 6% of global natural gas going to hydrogen production . The world is also looking at how hydrogen can be established as a transport fuel of the future.
Road transport remains a central feature of most hydrogen projects and policies worldwide. Several cities included fuel cell vehicles as part of green transport strategies to promote the use of fuel cell public buses in metropolitan and peri-urban areas of the country. About 4,000 fuel cell electric cars were sold in 2018, growth of almost 56% over the previous year, but this still represents a small fraction compared with the 2018 BEV stock of 5.1 million or the global car stock of more than 1 billion. .
Hydrogen fuel cell electric forklifts are already commercially viable as replacements for existing battery electric forklifts and it is estimated that 25,000 forklifts have fuel cells globally. In the case of buses, China has reported the largest deployment, with more than 400 registered by the end of 2018 for demonstration projects . An estimated 50 fuel cell electric buses were also in operation in Europe in 2017, 25 in California and about 30 in other US states. Other demonstration projects have rolled out fuel cell electric buses in Korea and Japan. Volumes are scaling up rapidly and thousands are expected to be in operation by the end of 2020 – mostly in China.
Hydrogen is also combined with CO2 to produce synthetic hydrocarbons such as methane, or synthetic liquid fuels such as methanol, diesel, gasoline, and jet fuel via a process called Fischer-Tropsch [FT] synthesis. FT synthesis is a fully commercial process, the largest coal-to-liquid plant of this kind has operated since the 1980s in Secunda, South Africa  .
4.2 What’s next?
Hydrogen technologies currently have niche status, and there is significant potential for both achieving economies of scale in the manufacturing process and improving the technology further.
The global hydrogen generation market continues to grow driven by increasing demand. It is currently over $100 billion, and it is estimated that it will reach $200 billion by 2025 . It is also noteworthy that Asian countries, such as China and India, have proposed to tighten their sulphur standards for vehicle fuels. This will further drive up hydrogen demand .
On a research-level, teams are looking at all kinds of advanced hydrogen storage. These hydrogen storage efforts include metal-organic frameworks and metal hydride solutions, like sodium alanate or ammonia boranes, but so far none of the proposed solutions works on all the fronts needed for hydrogen storage on a vehicle. Research and pilot projects to introduce hydrogen and ammonia as fuel for gas turbines and coal power plants are being pursued in Japan, the Netherlands, and Australia.
Fuel cell costs could be further reduced in the future through research-driven advances in technology. It may be possible to increase catalyst activity and thus reduce the platinum content, which is one of the expensive components of the fuel cell. It may also be possible to develop a platinum-free catalyst.
Looking ahead, it seems probable that the long-term potential of hydrogen as a low-CO2 energy carrier will not, by itself, be sufficient to prompt industrial innovations that are not otherwise economically sustainable. The difficulties encountered worldwide in attempts to establish a meaningful price for greenhouse gas emissions suggest that a progressive hydrogen economy might emerge more incrementally from the global hydrogen industry as it already exists today, rather than any disruptive innovation .
Hydrogen is an energy carrier that can be used to store massive amounts of energy for grid resilience and security and it is a critical feedstock for most of the chemicals industry. It can, therefore, be considered as an energy vector, a fuel and a raw material. Hydrogen fuel provides a potentially clean alternative to transform electricity into an energy vector for use in transport. Additionally, it can be used as zero-emission mobility in the different transport sectors whilst keeping the infrastructure and value chain in these equal.
Clearly, the proportion of hydrogen coming as green hydrogen from electrolysis using renewable electricity is currently very small, but clean hydrogen is currently enjoying unprecedented political and business momentum, with the number of policies and projects around the world expanding rapidly. Now is the time to scale up technologies and bring down costs to allow hydrogen to become widely used. Government actions and investment in partnerships, seed funding, and fit-for-purpose regulatory support, as well as efficient approval processes, will assist the hydrogen industry to overcome its economic, regulatory and technical challenges.
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