Hydrogen economy

Summary

The hydrogen economy is an umbrella term that draws together the roles hydrogen can play alongside low-carbon electricity to decarbonize those sectors and activities which may be technically difficult to decarbonize through other means, or where cheaper and more energy-efficient clean solutions are not available.[2] In this context, hydrogen economy encompasses hydrogen's production through to end-uses in ways that substantively contribute to phasing-out fossil fuels and limiting climate change.

Hydrogen has the most potential to reduce greenhouse gas emissions when used in chemical production, refineries, international shipping, and steelmaking, according to the International Renewable Energy Agency.[1]

Most hydrogen produced today is gray hydrogen, made from natural gas through steam methane reforming (SMR) which accounted for 1.8% of global greenhouse gas emissions in 2021.[3] Low-carbon hydrogen, which is made using SMR with carbon capture and storage (blue hydrogen), or through electrolysis of water using renewable power (green hydrogen), accounted for under 1% of production.[4] Virtually all hydrogen produced is used in oil refining (43% in 2021) and industry (57%), principally in the manufacture of ammonia for fertilizers, and methanol.[5]: 18, 22, 29 

In its contribution to limiting global warming to 1.5 °C, it is broadly envisaged that the future hydrogen economy replaces gray hydrogen with blue and predominantly green hydrogen, produced in greater total volumes, to provide for an expanded set of end-uses.[6] These are likely to be in heavy industry (e.g. high temperature processes alongside electricity, feedstock for production of green ammonia and organic chemicals, as alternative to coal-derived coke for steelmaking), long-haul transport (e.g. shipping, aviation and to a lesser extent heavy goods vehicles), and long-term energy storage.[6][7] Other applications, such as light duty vehicles and heating in buildings, are no longer part of the future hydrogen economy, primarily for economic and environmental reasons.[8][9] These reasons include the difficulty of developing long-term storage, pipelines, and engine equipment, safety concerns since hydrogen is highly explosive, and the inefficiency of hydrogen compared to direct use of electricity.

As of 2023 there are no real alternatives to hydrogen for ammonia production for fertilizer, hydrogenation, hydrocracking, and hydrodesulfurization.[10] The extent to which hydrogen will be used to decarbonise chemical feedstock, long haul aviation and shipping, and long-term energy storage is likely to be influenced by the evolving production costs of low- and zero-carbon hydrogen. Estimates of future costs face numerous uncertainties – such as the introduction of carbon taxes, geography and geopolitics of energy, energy prices, technology choices, and their raw material requirements – but it is likely that green or white (underground[11]) hydrogen will see the greatest reductions in production cost over time.[12]

History and contemporary rationale edit

Origins edit

The concept of the hydrogen economy, though not the term, was by geneticist J.B.S. Haldane in 1923, who, anticipating the exhaustion of Britain's coal reserves for power generation, proposed a network of wind turbines to produce hydrogen for long-term energy storage through electrolysis, to help address renewable power's variable output.[13] The term itself was coined by John Bockris during a talk he gave in 1970 at General Motors (GM) Technical Center.[14] Bockris viewed it as an economy in which hydrogen, underpinned by nuclear and solar power, would help address growing concern about fossil fuel depletion and environmental pollution, by serving as energy carrier for end-uses in which electrification was not suitable.[2]

A hydrogen economy was proposed by the University of Michigan to solve some of the negative effects of using hydrocarbon fuels where the carbon is released to the atmosphere (as carbon dioxide, carbon monoxide, unburnt hydrocarbons, etc.). Modern interest in the hydrogen economy can generally be traced to a 1970 technical report by Lawrence W. Jones of the University of Michigan,[15] in which he echoed Bockris' dual rationale of addressing energy security and environmental challenges. Unlike Haldane and Bockris, Jones only focused on nuclear power as the energy source for electrolysis, and principally on the use of hydrogen in transport, where he regarded aviation and heavy goods transport as the top priorities.[16]

Later evolution edit

 
Contemporary[dubious ] view of the hydrogen economy from the International Renewable Energy Agency

A spike in attention for the hydrogen economy concept during the 2000s was repeatedly described as hype by some critics and proponents of alternative technologies,[17][18][19] and investors lost money in the bubble.[20] Interest in the energy carrier resurged in the 2010s, notably with the forming of the World Hydrogen Council in 2017. Several manufacturers released hydrogen fuel cell cars commercially, with manufacturers such as Toyota, Hyundai, and industry groups in China having planned to increase numbers of the cars into the hundreds of thousands over the next decade.[21][22]

The global scope for hydrogen's role in cars is shrinking relative to earlier expectations.[23][24] By the end of 2022, 70,200 hydrogen vehicles had been sold worldwide,[25] compared with 26 million plug-in electric vehicles.[26]

Contemporary takes on the hydrogen economy share earlier perspectives' emphasis on the complementarity of electricity and hydrogen, and the use of electrolysis as the mainstay of hydrogen production.[6] They focus on the need to limit global warming to 1.5 °C and prioritize the production, transportation and use of green hydrogen for heavy industry (e.g. high-temperature processes alongside electricity,[27] feedstock for production of green ammonia and organic chemicals,[6] as alternative to coal-derived coke for steelmaking),[28] long-haul transport (e.g. shipping, aviation and to a lesser extent heavy goods vehicles), and long-term energy storage.[6][7]

Current hydrogen market edit

Hydrogen production globally was valued at over US$155 billion in 2022 and is expected to grow over 9% annually through 2030.[29]

In 2021, 94 million tonnes (Mt) of molecular hydrogen (H2) was produced.[30] Of this total, approximately one sixth was as a by-product of petrochemical industry processes.[4] Most hydrogen comes from dedicated production facilities, over 99% of which is from fossil fuels, mainly via steam reforming of natural gas (70%) and coal gasification (30%, almost all of which in China).[4] Less than 1% of dedicated hydrogen production is low carbon: steam fossil fuel reforming with carbon capture and storage, green hydrogen produced using electrolysis, and hydrogen produced from biomass.[4] CO2 emissions from 2021 production, at 915 MtCO2,[31] amounted to 2.5% of energy-related CO2 emissions[32] and 1.8% of global greenhouse gas emissions.[3]

Virtually all hydrogen produced for the current market is used in oil refining (40 MtH2 in 2021) and industry (54 MtH2).[5]: 18, 22  In oil refining, hydrogen is used, in a process known as hydrocracking, to convert heavy petroleum sources into lighter fractions suitable for use as fuels. Industrial uses mainly comprise ammonia production to make fertilisers (34 MtH2 in 2021), methanol production (15 MtH2) and the manufacture of direct reduced iron (5 MtH2).[5]: 29 

Production edit

As of 2022, more than 95% of global hydrogen production is sourced from fossil gas and coal without carbon abatement.[33]: 1 

Color codes edit

Hydrogen is often referred to by various colors to indicate its origin (perhaps because gray symbolizes "dirty hydrogen"[20]).[34][35]

Colors that refer to method of production[36]
Color Production source Notes References
green In most definitions, renewable electricity via electrolysis of water. Less frequently, definitions of green hydrogen include hydrogen produced from other low-emisison sources such as biomass. [37]
turquoise thermal splitting of methane via methane pyrolysis [38]: 28  [39]: 2 
blue hydrocarbons with carbon capture and storage CCS networks required [38]: 28 
gray fossil hydrocarbons, mainly steam reforming of natural gas [38]: 28  [40]: 10  [39]: 2 
brown or black fossil hydrocarbons: brown (lignite) or black coal via coal gasification or in a suitable reactor; requires abatement [41]: 91 
red, pink or purple nuclear power via thermochemical water splitting, electrolysis of water, or contributing steam to natural gas reforming [39]: 2 [20]
yellow sometimes understood to mean solar photovoltaics, or a mix of renewable and fossil electricity via photovoltaic [35]
gold or white hydrogen that occurs naturally deep within the Earth's crust obtained by mining; also referred to as white [42]

Methods of production edit

Molecular hydrogen was discovered in the Kola Superdeep Borehole. It is unclear how much molecular hydrogen is available in natural reservoirs, but at least one company[43] specializes in drilling wells to extract hydrogen. Most hydrogen in the lithosphere is bonded to oxygen in water. Manufacturing elemental hydrogen requires the consumption of a hydrogen carrier such as a fossil fuel or water. The former carrier consumes the fossil resource and in the steam methane reforming (SMR) process produces greenhouse gas carbon dioxide. However, in the newer methane pyrolysis process no greenhouse gas carbon dioxide is produced. These processes typically require no further energy input beyond the fossil fuel.

 
Illustrating inputs and outputs of steam reforming of natural gas, a process to produce hydrogen. As of 2020, the carbon sequestrastion step is not in commercial use.

Decomposing water, the latter carrier, requires electrical or heat input, generated from some primary energy source (fossil fuel, nuclear power or a renewable energy). Hydrogen produced by electrolysis of water using renewable energy sources such as wind and solar power, referred to as green hydrogen.[44] When derived from natural gas by zero greenhouse emission methane pyrolysis, it is referred to as turquoise hydrogen.[45]

When fossil fuel derived with greenhouse gas emissions, is generally referred to as grey hydrogen. If most of the carbon dioxide emission is captured, it is referred to as blue hydrogen.[46] Hydrogen produced from coal may be referred to as brown or black hydrogen.[47]

Current production methods edit

Steam reforming – gray or blue edit

Hydrogen is industrially produced from steam reforming (SMR), which uses natural gas.[48] The energy content of the produced hydrogen is around 74% of the energy content of the original fuel,[49] as some energy is lost as excess heat during production. In general, steam reforming emits carbon dioxide, a greenhouse gas, and is known as gray hydrogen. If the carbon dioxide is captured and stored, the hydrogen produced is known as blue hydrogen.

Electrolysis of water – green, pink or yellow edit

 
Illustrating inputs and outputs of simple electrolysis of water production of hydrogen

Hydrogen can be made via high pressure electrolysis, low pressure electrolysis of water, or a range of other emerging electrochemical processes such as high temperature electrolysis or carbon assisted electrolysis.[50] However, current best processes for water electrolysis have an effective electrical efficiency of 70-80%,[51][52][53] so that producing 1 kg of hydrogen (which has a specific energy of 143 MJ/kg or about 40 kWh/kg) requires 50–55 kWh of electricity.

In parts of the world, steam methane reforming is between $1–3/kg on average excluding hydrogen gas pressurization cost. This makes production of hydrogen via electrolysis cost competitive in many regions already, as outlined by Nel Hydrogen[54] and others, including an article by the IEA[55] examining the conditions which could lead to a competitive advantage for electrolysis.

A small part (2% in 2019[56]) is produced by electrolysis using electricity and water, consuming approximately 50 to 55 kilowatt-hours of electricity per kilogram of hydrogen produced.[57]

Hydrogen from biomass – green edit

Biomass is converted into syngas by gasification and syngas is further converted into hydrogen by water-gas shift reaction (WGSR)[58]

Hydrogen as a byproduct of other chemical processes edit

The industrial production of chlorine and caustic soda by electrolysis generates a sizable amount of Hydrogen as a byproduct. In the port of Antwerp a 1MW demonstration fuel cell power plant is powered by such byproduct. This unit has been operational since late 2011.[59] The excess hydrogen is often managed with a hydrogen pinch analysis.

Gas generated from coke ovens in steel production is similar to Syngas with 60% hydrogen by volume.[60] The hydrogen can be extracted from the coke oven gas economically.[61]

Uses edit

 
Some projected uses in the medium term, but analysts disagree[62]
 
Hydrogen fuel requires the development of a specific infrastructure for processing, transport and storage.

Hydrogen can be deployed as a fuel in two distinct ways: in fuel cells which produce electricity, and via combustion to generate heat.[63] When hydrogen is consumed in fuel cells, the only emission at the point of use is water vapour.[63] Combustion of hydrogen can lead to the thermal formation of harmful nitrogen oxides emissions.[63]

Industry edit

In the context of limiting global warming, low-carbon hydrogen (particularly green hydrogen) is likely to play an important role in decarbonising industry.[64] Hydrogen fuel can produce the intense heat required for industrial production of steel, cement, glass, and chemicals, thus contributing to the decarbonisation of industry alongside other technologies, such as electric arc furnaces for steelmaking.[27] However, it is likely to play a larger role in providing industrial feedstock for cleaner production of ammonia and organic chemicals.[64] For example, in steelmaking, hydrogen could function as a clean energy carrier and also as a low-carbon catalyst replacing coal-derived coke.[28]

The imperative to use low-carbon hydrogen to reduce greenhouse gas emissions has the potential to reshape the geography of industrial activities, as locations with appropriate hydrogen production potential in different regions will interact in new ways with logistics infrastructure, raw material availability, human and technological capital.[64]

Transport edit

Much of the interest in the hydrogen economy concept is focused on hydrogen vehicles, particularly planes.[65][66][67] Hydrogen vehicles produce significantly less local air pollution than conventional vehicles.[68] By 2050, the energy requirement for transportation might be between 20% and 30% fulfilled by hydrogen and synthetic fuels.[69][70][71]

Hydrogen used to decarbonise transportation is likely to find its largest applications in shipping, aviation and to a lesser extent heavy goods vehicles, through the use of hydrogen-derived synthetic fuels such as ammonia and methanol, and fuel cell technology.[6] Hydrogen has been used in fuel cell buses for many years. It is also used as a fuel for spacecraft propulsion.

In the International Energy Agency's 2022 Net Zero Emissions Scenario (NZE), hydrogen is forecast to account for 2% of rail energy demand in 2050, while 90% of rail travel is expected to be electrified by then (up from 45% today). Hydrogen's role in rail would likely be focused on lines that prove difficult or costly to electrify.[72] The NZE foresees hydrogen meeting approximately 30% of heavy truck energy demand in 2050, mainly for long-distance heavy freight (with battery electric power accounting for around 60%).[73]

Although hydrogen can be used in adapted internal combustion engines, fuel cells, being electrochemical, have an efficiency advantage over heat engines. Fuel cells are more expensive to produce than common internal combustion engines but also require higher purity hydrogen fuel than internal combustion engines.[74]

In the light road vehicle segment including passenger cars, by the end of 2022, 70,200 fuel cell electric vehicles had been sold worldwide,[25] compared with 26 million plug-in electric vehicles.[26] With the rapid rise of electric vehicles and associated battery technology and infrastructure, hydrogen's role in cars is miniscule.[23][24]

Energy system balancing and storage edit

Green hydrogen, from electrolysis of water, has the potential to address the variability of renewable energy output. Producing green hydrogen can both reduce the need for renewable power curtailment during periods of high renewables output and be stored long-term to provide for power generation during periods of low output.[75][76]

Ammonia edit

An alternative to gaseous hydrogen as an energy carrier is to bond it with nitrogen from the air to produce ammonia, which can be easily liquefied, transported, and used (directly or indirectly) as a clean and renewable fuel.[77][78] Among disadvantages of ammonia as an energy carrier are its high toxicity, energy efficiency of NH3 production from N2 and H2, and poisoning of PEM Fuel Cells by traces of non-decomposed NH3 after NH3 to N2 conversion.

Buildings edit

Numerous industry groups (gas networks, gas boiler manufacturers) across the natural gas supply chain are promoting hydrogen combustion boilers for space and water heating, and hydrogen appliances for cooking, to reduce energy-related CO2 emissions from residential and commercial buildings.[79][80][9] The proposition is that current end-users of piped natural gas can await the conversion of and supply of hydrogen to existing natural gas grids, and then swap heating and cooking appliances, and that there is no need for consumers to do anything now.[79][80][9]

A review of 32 studies on the question of hydrogen for heating buildings, independent of commercial interests, found that the economics and climate benefits of hydrogen for heating and cooking generally compare very poorly with the deployment of district heating networks, electrification of heating (principally through heat pumps) and cooking, the use of solar thermal, waste heat and the installation of energy efficiency measures to reduce energy demand for heat.[9] Due to inefficiencies in hydrogen production, using blue hydrogen to replace natural gas for heating could require three times as much methane, while using green hydrogen would need two to three times as much electricity as heat pumps.[9] Hybrid heat pumps, which combine the use of an electric heat pump with a hydrogen boiler, may play a role in residential heating in areas where upgrading networks to meet peak electrical demand would otherwise be costly.[9]

The widespread use of hydrogen for heating buildings would entail higher energy system costs, higher heating costs and higher environmental impacts than the alternatives, although a niche role may be appropriate in specific contexts and geographies.[9] If deployed, using hydrogen in buildings would drive up the cost of hydrogen for harder-to-decarbonise applications in industry and transport.[9]

Bio-SNG edit

As of 2019 although technically possible production of syngas from hydrogen and carbon-dioxide from bio-energy with carbon capture and storage (BECCS) via the Sabatier reaction is limited by the amount of sustainable bioenergy available:[81] therefore any bio-SNG made may be reserved for production of aviation biofuel.[82]

Storage edit

Although molecular hydrogen has very high energy density on a mass basis, partly because of its low molecular weight, as a gas at ambient conditions it has very low energy density by volume. If it is to be used as fuel stored on board the vehicle, pure hydrogen gas must be stored in an energy-dense form to provide sufficient driving range. Because hydrogen is the smallest molecule, it easily escapes from containers. Considering leakages, transport and production costs, hydrogen could have a Global Warming Potential (GWP100) of 11.6. Methane, for comparison, has a GWP of 34.[83]

Pressurized hydrogen gas edit

Increasing gas pressure improves the energy density by volume making for smaller container tanks. The standard material for holding pressurised hydrogen in tube trailers is steel (there is no hydrogen embrittlement problem with hydrogen gas). Tanks made of carbon and glass fibres reinforcing plastic as fitted in Toyota Marai and Kenworth trucks are required to meet safety standards. Few materials are suitable for tanks as hydrogen being a small molecule tends to diffuse through many polymeric materials. The most common on board hydrogen storage in 2020 vehicles was hydrogen at pressure 700bar = 70MPa. The energy cost of compressing hydrogen to this pressure is significant.

Pressurized gas pipelines are always made of steel and operate at much lower pressures than tube trailers.

Liquid hydrogen edit

Alternatively, higher volumetric energy density liquid hydrogen or slush hydrogen may be used. However, liquid hydrogen is cryogenic and boils at 20.268 K (−252.882 °C or −423.188 °F). Cryogenic storage cuts weight but requires large liquification energies. The liquefaction process, involving pressurizing and cooling steps, is energy intensive.[84] The liquefied hydrogen has lower energy density by volume than gasoline by approximately a factor of four, because of the low density of liquid hydrogen – there are actually more oxidizable hydrogen atoms in a litre of gasoline (116 grams) than there are in a litre of pure liquid hydrogen (71 grams). Like any other liquid at cryogenic temperatures, the liquid hydrogen storage tanks must also be well insulated to minimize boil off.

Japan has a liquid hydrogen (LH2) storage facility at a terminal in Kobe, and was expected to receive the first shipment of liquid hydrogen via LH2 carrier in 2020.[85] Hydrogen is liquified by reducing its temperature to −253 °C, similar to liquified natural gas (LNG) which is stored at −162 °C. A potential efficiency loss of 12.79% can be achieved, or 4.26kWh/kg out of 33.3kWh/kg.[86]

Liquid organic hydrogen carriers (LOHC) edit

Storage as hydride edit

Distinct from storing molecular hydrogen, hydrogen can be stored as a chemical hydride or in some other hydrogen-containing compound. Hydrogen gas is reacted with some other materials to produce the hydrogen storage material, which can be transported relatively easily. At the point of use the hydrogen storage material can be made to decompose, yielding hydrogen gas. As well as the mass and volume density problems associated with molecular hydrogen storage, current barriers to practical storage schemes stem from the high pressure and temperature conditions needed for hydride formation and hydrogen release.[citation needed]

Adsorption edit

A third approach is to adsorb molecular hydrogen on the surface of a solid storage material. Unlike in the hydrides mentioned above, the hydrogen does not dissociate/recombine upon charging/discharging the storage system, and hence does not suffer from the kinetic limitations of many hydride storage systems. Hydrogen densities similar to liquefied hydrogen can be achieved with appropriate adsorbent materials. Some suggested adsorbents include activated carbon, nanostructured carbons (including CNTs), MOFs, and hydrogen clathrate hydrate.[citation needed]

Underground hydrogen storage edit

 
'Available storage technologies, their capacity and discharge time.' COMMISSION STAFF WORKING DOCUMENT Energy storage – the role of electricity

Underground hydrogen storage is the practice of hydrogen storage in caverns, salt domes and depleted oil and gas fields. Large quantities of gaseous hydrogen have been stored in caverns by ICI for many years without any difficulties.[87] The storage of large quantities of liquid hydrogen underground can function as grid energy storage. The round-trip efficiency is approximately 40% (vs. 75–80% for pumped-hydro (PHES)), and the cost is slightly higher than pumped hydro.[88]

Another study referenced by a European staff working paper found that for large scale storage, the cheapest option is hydrogen at €140/MWh for 2,000 hours of storage using an electrolyser, salt cavern storage and combined-cycle power plant.[89] The European project Hyunder[90] indicated in 2013 that for the storage of wind and solar energy an additional 85 caverns are required as it cannot be covered by PHES and CAES systems.[91]

A German case study on storage of hydrogen in salt caverns found that if the German power surplus (7% of total variable renewable generation by 2025 and 20% by 2050) would be converted to hydrogen and stored underground, these quantities would require some 15 caverns of 500,000 cubic metres each by 2025 and some 60 caverns by 2050 – corresponding to approximately one third of the number of gas caverns currently operated in Germany.[92] In the US, Sandia Labs are conducting research into the storage of hydrogen in depleted oil and gas fields, which could easily absorb large amounts of renewably produced hydrogen as there are some 2.7 million depleted wells in existence.[93]

Infrastructure edit

 
Hydrogen gasification plant for Belinka Perkemija [sl], 2015

The hydrogen infrastructure would consist mainly of industrial hydrogen pipeline transport and hydrogen-equipped filling stations like those found on a hydrogen highway. Hydrogen stations which were not situated near a hydrogen pipeline would get supply via hydrogen tanks, compressed hydrogen tube trailers, liquid hydrogen trailers, liquid hydrogen tank trucks or dedicated onsite production.

Over 700 miles of hydrogen pipeline currently exist in the United States.[citation needed] Pipelines are the cheapest way to move hydrogen over long distances compared to other options. Hydrogen gas piping is routine in large oil-refineries, because hydrogen is used to hydrocrack fuels from crude oil.

Hydrogen embrittlement (a reduction in the ductility of a metal due to absorbed hydrogen) is not a problem for hydrogen gas pipelines. Hydrogen embrittlement only happens with 'diffusible' hydrogen, i.e. atoms or ions. Hydrogen gas, however, is molecular (H2), and there is a very significant energy barrier to splitting it into atoms.[94]

The IEA recommends existing industrial ports be used for production and existing natural gas pipelines for transport: also international co-operation and shipping.[95]

South Korea and Japan,[96] which as of 2019 lack international electrical interconnectors, are investing in the hydrogen economy.[97] In March 2020, the Fukushima Hydrogen Energy Research Field was opened in Japan, claiming to be the world's largest hydrogen production facility.[98] The site occupies 180,000 m2 (1,900,000 sq ft) of land, much of which is occupied by a solar array; power from the grid is also used for electrolysis of water to produce hydrogen fuel.[99]

Distributed electrolysis edit

Distributed electrolysis would bypass the problems of distributing hydrogen by distributing electricity instead. It would use existing electrical networks to transport electricity to small, on-site electrolysers located at filling stations. However, accounting for the energy used to produce the electricity and transmission losses would reduce the overall efficiency.

Safety edit

 
A NASA engineer sweeps an area with a corn broom to find the location of a hydrogen fire. Hydrogen burns with a nearly-invisible flame.

Hydrogen safety covers the safe production, handling and use of hydrogen, particularly hydrogen gas fuel and liquid hydrogen. Hydrogen possesses the NFPA 704's highest rating of four on the flammability scale because it is flammable when mixed even in small amounts with ordinary air. Ignition can occur at a volumetric ratio of hydrogen to air as low as 4% due to the oxygen in the air and the simplicity and chemical properties of the reaction. However, hydrogen has no rating for innate hazard for reactivity or toxicity. The storage and use of hydrogen poses unique challenges due to its ease of leaking as a gaseous fuel, low-energy ignition, wide range of combustible fuel-air mixtures, buoyancy, and its ability to embrittle metals that must be accounted for to ensure safe operation.[100]

Liquid hydrogen poses additional challenges due to its increased density and the extremely low temperatures needed to keep it in liquid form. Moreover, its demand and use in industry—as rocket fuel, alternative energy storage source, coolant for electric generators in power stations, a feedstock in industrial and chemical processes including production of ammonia and methanol, etc.—has continued to increase, which has led to the increased importance of considerations of safety protocols in producing, storing, transferring, and using hydrogen.[100]

Costs edit

More widespread use of hydrogen in economies entails the need for investment and costs in its production, storage, distribution and use. Estimates of hydrogen's cost are therefore complex and need to make assumptions about the cost of energy inputs (typically gas and electricity), production plant and method (e.g. green or blue hydrogen), technologies used (e.g. alkaline or proton exchange membrane electrolysers), storage and distribution methods, and how different cost elements might change over time.[101]: 49–65  These factors are incorporated into calculations of the levelized costs of hydrogen (LCOH). The following table shows a range of estimates of the levelized costs of gray, blue, and green hydrogen, expressed in terms of US$ per kg of H2 (where data provided in other currencies or units, the average exchange rate to US dollars in the given year are used, and 1 kg of H2 is assumed to have a calorific value of 33.3kWh).

Production method Note Current cost (2020–2022) Projected 2030 cost Projected 2050 cost
Gray hydrogen (not including a carbon tax)
International Energy Agency[102] 2022 costs estimated for June, when gas prices peaked in the wake of Russia's invasion of Ukraine 2021: 1.0–2.5
2022: 4.8–7.8
PWC[103] 2021: 1.2–2.4
Blue hydrogen
International Energy Agency[102] 2022 costs estimated for June, when gas prices peaked in the wake of Russia's invasion of Ukraine 2021: 1.5–3.0
2022: 5.3–8.6
UK government[104] Range dependent on gas price 2020: 1.6–2.7 1.6–2.7 1.6–2.8
GEP[105] 2022: 2.8–3.5 - -
Energy Transitions Commission[101]: 28  2020: 1.5–2.4 1.3–2.3 1.4–2.2
Green hydrogen
International Energy Agency[102] 2030 and 2050 estimates are using solar power in regions with good solar conditions 2021: 4.0–9.0 <1.5 <1.0
2022: 3.0-4.3
UK government[104] Using grid electricity, UK specific; range dependent on electricity price, and electrolyser technology and cost 2020: 4.9–7.9 4.4–6.6 4.0–6.3
Using otherwise curtailed renewable electricity, UK specific; range dependent on electrolyser technology and cost 2020: 2.4–7.9 1.7–5.6 1.5–4.6
IRENA[106] 2020: 2.2–5.2 1.4–4.1 1.1–3.4
GEP[105] Source notes green H2 production cost has fallen by 60% since 2010 2022: 3.0–6.0
Lazard[107] 2022: 2.8–5.3
PWC[103] 2021: 3.5–9.5 1.8–4.8 1.2–2.4
Energy Transitions Commission[101]: 28  2020: 2.6–3.6 1.0–1.7 0.7–1.2

The range of cost estimates for commercially available hydrogen production methods is broad, As of 2022, gray hydrogen is cheapest to produce without a tax on its CO2 emissions, followed by blue and green hydrogen. Blue hydrogen production costs are not anticipated to fall substantially by 2050,[104][101]: 28  can be expected to fluctuate with natural gas prices and could face carbon taxes for uncaptured emissions.[101]: 79  The cost of electrolysers fell by 60% from 2010 to 2022,[105] before rising slightly due to an increasing cost of capital.[20] Their cost is projected to fall significantly to 2030 and 2050,[108]: 26  driving down the cost of green hydrogen alongside the falling cost of renewable power generation.[109][101]: 28  It is cheapest to produce green hydrogen with surplus renewable power that would otherwise be curtailed, which favours electrolysers capable of responding to low and variable power levels.[108]: 5 

A 2022 Goldman Sachs analysis anticipates that globally green hydrogen will achieve cost parity with grey hydrogen by 2030, earlier if a global carbon tax is placed on gray hydrogen.[12] In terms of cost per unit of energy, blue and gray hydrogen will always cost more than the fossil fuels used in its production, while green hydrogen will always cost more than the renewable electricity used to make it.

Subsidies for clean hydrogen production are much higher in the US and EU than in India.[110]

Examples and pilot programs edit

 
A Mercedes-Benz O530 Citaro powered by hydrogen fuel cells, in Brno, Czech Republic.

The distribution of hydrogen for the purpose of transportation is being tested around the world, particularly in the US (California, Massachusetts), Canada, Japan, the EU (Portugal, Norway, Denmark, Germany), and Iceland.

An indicator of the presence of large natural gas infrastructures already in place in countries and in use by citizens is the number of natural gas vehicles present in the country. The countries with the largest amount of natural gas vehicles are (in order of magnitude):[111]Iran, China, Pakistan, Argentina, India, Brasil, Italy, Colombia, Thailand, Uzbekistan, Bolivia, Armenia, Bangladesh, Egypt, Peru, Ukraine, United States. Natural gas vehicles can also be converted to run on hydrogen.

Also, in some private homes, fuel cell micro-CHP plants can be found, which can operate on hydrogen, or other fuels as natural gas or LPG.[112][113] When running on natural gas, it relies on steam reforming of natural gas to convert the natural gas to hydrogen prior to use in the fuel cell. This hence still emits CO2 (see reaction) but (temporarily) running on this can be a good solution until the point where the hydrogen is starting to become distributed through the (natural gas) piping system.[original research?]

Australia edit

Western Australia's Department of Planning and Infrastructure operated three Daimler Chrysler Citaro fuel cell buses as part of its Sustainable Transport Energy for Perth Fuel Cells Bus Trial in Perth.[114] The buses were operated by Path Transit on regular Transperth public bus routes. The trial began in September 2004 and concluded in September 2007. The buses' fuel cells used a proton exchange membrane system and were supplied with raw hydrogen from a BP refinery in Kwinana, south of Perth. The hydrogen was a byproduct of the refinery's industrial process. The buses were refueled at a station in the northern Perth suburb of Malaga.

In October 2021, Queensland Premier Annastacia Palaszczuk and Andrew Forrest announced that Queensland will be home to the world's largest hydrogen plant.[115]

In Australia, the Australian Renewable Energy Agency (ARENA) has invested $55 million in 28 hydrogen projects, from early stage research and development to early stage trials and deployments. The agency's stated goal is to produce hydrogen by electrolysis for $2 per kilogram, announced by Minister for Energy and Emissions Angus Taylor in a 2021 Low Emissions Technology Statement.[116]

European Union edit

Countries in the EU which have a relatively large natural gas pipeline system already in place include Belgium, Germany, France, and the Netherlands.[117] In 2020, The EU launched its European Clean Hydrogen Alliance (ECHA).[118][119]

France edit

Green hydrogen has become more common in France. A €150 million Green Hydrogen Plan was established in 2019, and it calls for building the infrastructure necessary to create, store, and distribute hydrogen as well as using the fuel to power local transportation systems like buses and trains. Corridor H2, a similar initiative, will create a network of hydrogen distribution facilities in Occitania along the route between the Mediterranean and the North Sea. The Corridor H2 project will get a €40 million loan from the EIB.[120][121]

Germany edit

German car manufacturer BMW has been working with hydrogen for years.[quantify].[122]

Iceland edit

Iceland has committed to becoming the world's first hydrogen economy by the year 2050.[123] Iceland is in a unique position. Presently,[when?] it imports all the petroleum products necessary to power its automobiles and fishing fleet. Iceland has large geothermal resources, so much that the local price of electricity actually is lower than the price of the hydrocarbons that could be used to produce that electricity.

Iceland already converts its surplus electricity into exportable goods and hydrocarbon replacements. In 2002, it produced 2,000 tons of hydrogen gas by electrolysis, primarily for the production of ammonia (NH3) for fertilizer. Ammonia is produced, transported, and used throughout the world, and 90% of the cost of ammonia is the cost of the energy to produce it.

Neither industry directly replaces hydrocarbons. Reykjavík, Iceland, had a small pilot fleet of city buses running on compressed hydrogen,[124] and research on powering the nation's fishing fleet with hydrogen is under way (for example by companies as Icelandic New Energy). For more practical purposes, Iceland might process imported oil with hydrogen to extend it, rather than to replace it altogether.

The Reykjavík buses are part of a larger program, HyFLEET:CUTE,[125] operating hydrogen fueled buses in eight European cities. HyFLEET:CUTE buses were also operated in Beijing, China and Perth, Australia (see below). A pilot project demonstrating a hydrogen economy is operational on the Norwegian island of Utsira. The installation combines wind power and hydrogen power. In periods when there is surplus wind energy, the excess power is used for generating hydrogen by electrolysis. The hydrogen is stored, and is available for power generation in periods when there is little wind.[citation needed]

India edit

India is said to adopt hydrogen and H-CNG, due to several reasons, amongst which the fact that a national rollout of natural gas networks is already taking place and natural gas is already a major vehicle fuel. In addition, India suffers from extreme air pollution in urban areas.[126][127] According to some estimates, nearly 80% of India's hydrogen is projected to be green, driven by cost declines and new production technologies.[128]

Currently however, hydrogen energy is just at the Research, Development and Demonstration (RD&D) stage.[129][130] As a result, the number of hydrogen stations may still be low,[131] although much more are expected to be introduced soon.[132][133][134]

Saudi Arabia edit

Saudi Arabia as a part of the NEOM project, is looking to produce roughly 1.2 million tonnes of green ammonia a year, beginning production in 2025.[135]

Turkey edit

The Turkish Ministry of Energy and Natural Resources and the United Nations Industrial Development Organization created the International Centre for Hydrogen Energy Technologies (UNIDO-ICHET) in Istanbul in 2004 and it ran to 2012.[136] In 2023 the ministry published a Hydrogen Technologies Strategy and Roadmap.[137]

United Kingdom edit

The UK started a fuel cell pilot program in January 2004, the program ran two Fuel cell buses on route 25 in London until December 2005, and switched to route RV1 until January 2007.[138] The Hydrogen Expedition is currently working to create a hydrogen fuel cell-powered ship and using it to circumnavigate the globe, as a way to demonstrate the capability of hydrogen fuel cells.[139] In August 2021 the UK Government claimed it was the first to have a Hydrogen Strategy and produced a document.[140]

In August 2021, Chris Jackson quit as chair of the UK Hydrogen and Fuel Cell Association, a leading hydrogen industry association, claiming that UK and Norwegian oil companies had intentionally inflated their cost projections for blue hydrogen in order to maximize future technology support payments by the UK government.[141]

United States edit

Several domestic U.S. automobile companies have developed vehicles using hydrogen, such as GM and Toyota.[142] However, as of February 2020, infrastructure for hydrogen was underdeveloped except in some parts of California.[143] The United States have their own hydrogen policy.[citation needed] A joint venture between NREL and Xcel Energy is combining wind power and hydrogen power in the same way in Colorado.[144] Hydro in Newfoundland and Labrador are converting the current wind-diesel Power System on the remote island of Ramea into a Wind-Hydrogen Hybrid Power Systems facility.[145]

A similar pilot project on Stuart Island uses solar power, instead of wind power, to generate electricity. When excess electricity is available after the batteries are fully charged, hydrogen is generated by electrolysis and stored for later production of electricity by fuel cell.[146] The US also have a large natural gas pipeline system already in place.[117]

Timeline of results for research and development edit

Experimental production methods edit

Methane pyrolysis – turquoise edit

 
Illustrating inputs and outputs of methane pyrolysis, a process to produce Hydrogen

Pyrolysis of methane (natural gas) with a one-step process[147] bubbling methane through a molten metal catalyst is a "no greenhouse gas" approach to produce hydrogen that was demonstrated in laboratory conditions in 2017 and now being tested at larger scales.[148][45] The process is conducted at high temperatures (1065 °C).[149][150][151][152] Producing 1 kg of hydrogen requires about 18 kWh of electricity for process heat.[153] The pyrolysis of methane can be expressed by the following reaction equation.[154]

CH
4
(g) → C(s) + 2 H
2
(g) ΔH° = 74.8 kJ/mol

The industrial quality solid carbon may be sold as manufacturing feedstock or landfilled (no pollution).

Biological production edit

Fermentative hydrogen production is the fermentative conversion of organic substrate to biohydrogen manifested by a diverse group of bacteria using multi enzyme systems involving three steps similar to anaerobic conversion. Dark fermentation reactions do not require light energy, so they are capable of constantly producing hydrogen from organic compounds throughout the day and night. Photofermentation differs from dark fermentation because it only proceeds in the presence of light. For example, photo-fermentation with Rhodobacter sphaeroides SH2C can be employed to convert small molecular fatty acids into hydrogen.[155] Electrohydrogenesis is used in microbial fuel cells where hydrogen is produced from organic matter (e.g. from sewage, or solid matter[156]) while 0.2 – 0.8 V is applied.

Biological hydrogen can be produced in an algae bioreactor. In the late 1990s it was discovered that if the algae is deprived of sulfur it will switch from the production of oxygen, i.e. normal photosynthesis, to the production of hydrogen.[157]

Biological hydrogen can be produced in bioreactors that use feedstocks other than algae, the most common feedstock being waste streams. The process involves bacteria feeding on hydrocarbons and excreting hydrogen and CO2. The CO2 can be sequestered successfully by several methods, leaving hydrogen gas. In 2006–2007, NanoLogix first demonstrated a prototype hydrogen bioreactor using waste as a feedstock at Welch's grape juice factory in North East, Pennsylvania (U.S.).[158]

Biocatalysed electrolysis edit

Besides regular electrolysis, electrolysis using microbes is another possibility. With biocatalysed electrolysis, hydrogen is generated after running through the microbial fuel cell and a variety of aquatic plants can be used. These include reed sweetgrass, cordgrass, rice, tomatoes, lupines, and algae[159]

High-pressure electrolysis edit

High pressure electrolysis is the electrolysis of water by decomposition of water (H2O) into oxygen (O2) and hydrogen gas (H2) by means of an electric current being passed through the water. The difference with a standard electrolyzer is the compressed hydrogen output around 120–200 bar (1740–2900 psi, 12–20 MPa).[160] By pressurising the hydrogen in the electrolyser, through a process known as chemical compression, the need for an external hydrogen compressor is eliminated,[161] the average energy consumption for internal compression is around 3%.[162] European largest (1 400 000 kg/a, High-pressure Electrolysis of water, alkaline technology) hydrogen production plant is operating at Kokkola, Finland.[163]

High-temperature electrolysis edit

Hydrogen can be generated from energy supplied in the form of heat and electricity through high-temperature electrolysis (HTE). Because some of the energy in HTE is supplied in the form of heat, less of the energy must be converted twice (from heat to electricity, and then to chemical form), and so potentially far less energy is required per kilogram of hydrogen produced.

While nuclear-generated electricity could be used for electrolysis, nuclear heat can be directly applied to split hydrogen from water. High temperature (950–1000 °C) gas cooled nuclear reactors have the potential to split hydrogen from water by thermochemical means using nuclear heat. Research into high-temperature nuclear reactors may eventually lead to a hydrogen supply that is cost-competitive with natural gas steam reforming. General Atomics predicts that hydrogen produced in a High Temperature Gas Cooled Reactor (HTGR) would cost $1.53/kg. In 2003, steam reforming of natural gas yielded hydrogen at $1.40/kg. In 2005 natural gas prices, hydrogen costs $2.70/kg.

High-temperature electrolysis has been demonstrated in a laboratory, at 108 MJ (thermal) per kilogram of hydrogen produced,[164] but not at a commercial scale. In addition, this is lower-quality "commercial" grade Hydrogen, unsuitable for use in fuel cells.[165]

Photoelectrochemical water splitting edit

Using electricity produced by photovoltaic systems offers the cleanest way to produce hydrogen. Water is broken into hydrogen and oxygen by electrolysis – a photoelectrochemical cell (PEC) process which is also named artificial photosynthesis.[166] William Ayers at Energy Conversion Devices demonstrated and patented the first multijunction high efficiency photoelectrochemical system for direct splitting of water in 1983.[167] This group demonstrated direct water splitting now referred to as an "artificial leaf" or "wireless solar water splitting" with a low cost thin film amorphous silicon multijunction sheet immersed directly in water.[168][169]

Hydrogen evolved on the front amorphous silicon surface decorated with various catalysts while oxygen evolved off the back metal substrate. A Nafion membrane above the multijunction cell provided a path for ion transport. Their patent also lists a variety of other semiconductor multijunction materials for the direct water splitting in addition to amorphous silicon and silicon germanium alloys. Research continues towards developing high-efficiency multi-junction cell technology at universities and the photovoltaic industry. If this process is assisted by photocatalysts suspended directly in water instead of using photovoltaic and an electrolytic system, the reaction is in just one step, which can improve efficiency.[168][169]

Photoelectrocatalytic production edit

A method studied by Thomas Nann and his team at the University of East Anglia consists of a gold electrode covered in layers of indium phosphide (InP) nanoparticles. They introduced an iron-sulfur complex into the layered arrangement, which when submerged in water and irradiated with light under a small electric current, produced hydrogen with an efficiency of 60%.[170]

In 2015, it was reported that Panasonic Corp. has developed a photocatalyst based on niobium nitride that can absorb 57% of sunlight to support the decomposition of water to produce hydrogen gas.[171] The company plans to achieve commercial application "as early as possible", not before 2020.

Concentrating solar thermal edit

Very high temperatures are required to dissociate water into hydrogen and oxygen. A catalyst is required to make the process operate at feasible temperatures. Heating the water can be achieved through the use of water concentrating solar power. Hydrosol-2 is a 100-kilowatt pilot plant at the Plataforma Solar de Almería in Spain which uses sunlight to obtain the required 800 to 1,200 °C to heat water. Hydrosol II has been in operation since 2008. The design of this 100-kilowatt pilot plant is based on a modular concept. As a result, it may be possible that this technology could be readily scaled up to the megawatt range by multiplying the available reactor units and by connecting the plant to heliostat fields (fields of sun-tracking mirrors) of a suitable size.[172]

Thermochemical production edit

There are more than 352[173] thermochemical cycles which can be used for water splitting,[174] around a dozen of these cycles such as the iron oxide cycle, cerium(IV) oxide-cerium(III) oxide cycle, zinc zinc-oxide cycle, sulfur-iodine cycle, copper-chlorine cycle and hybrid sulfur cycle, aluminum aluminum-oxide cycle, are under research and in testing phase to produce hydrogen and oxygen from water and heat without using electricity.[175] These processes can be more efficient than high-temperature electrolysis, typical in the range from 35% – 49% LHV efficiency. Thermochemical production of hydrogen using chemical energy from coal or natural gas is generally not considered, because the direct chemical path is more efficient.

None of the thermochemical hydrogen production processes have been demonstrated at production levels, although several have been demonstrated in laboratories.

Microwaving plastics edit

A 97% recovery of hydrogen has been achieved through microwaving plastics for a few seconds that have been ground and mixed with iron oxide and aluminium oxide.[176]

Kværner process edit

The Kværner process or Kvaerner carbon black and hydrogen process (CB&H)[177] is a method, developed in the 1980s by a Norwegian company of the same name, for the production of hydrogen from hydrocarbons (CnHm), such as methane, natural gas and biogas. Of the available energy of the feed, approximately 48% is contained in the hydrogen, 40% is contained in activated carbon and 10% in superheated steam.[178]

Extraction of naturally-occurring hydrogen – White Hydrogen edit

As of 2019, hydrogen is mainly used as an industrial feedstock, primarily for the production of ammonia and methanol, and in petroleum refining. Although initially hydrogen gas was thought not to occur naturally in convenient reservoirs, it is now demonstrated that this is not the case; a hydrogen system is currently being exploited near Bourakebougou, Koulikoro Region in Mali, producing electricity for the surrounding villages.[179] More discoveries of naturally occurring hydrogen in continental, on-shore geological environments have been made in recent years[180] and open the way to the novel field of natural or native hydrogen, supporting energy transition efforts.[181][182]

 
Mid-continental Rift System

White hydrogen could be found or produced in the Mid-continental Rift System at scale for a renewable hydrogen economy. Water could be pumped down to hot iron-rich rock to produce hydrogen and the hydrogen could be extracted.[183]

See also edit

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Sources edit

External links edit

  • International Partnership for the Hydrogen Economy
  • Hydrogen. International Energy Agency. 2022
  • European Hydrogen Association
  • Online calculator for green hydrogen production and transport costs