ENERGY OF THE FUTURE? - SHELL HYDROGEN STUDY - Hydrogen Europe
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SHELL HYDROGEN STUDY ENERGY OF THE FUTURE? Sustainable Mobility through Fuel Cells and H2
SHELL HYDROGEN STUDY
ENERGY OF THE FUTURE? INTRODUCTION 4 1
THE ELEMENT HYDROGEN 6
Sustainable Mobility through Fuel Cells and H2
SHELL WUPPERTAL INSTITUT
Dr. Jörg Adolf (Project Lead) Prof. Dr. Manfred Fischedick (Supervision)
Dr. Christoph H. Balzer Dr. Karin Arnold (Project Coordination)
Dr. Jurgen Louis Dipl.-Soz.Wiss. Andreas Pastowski
Dipl.-Ing. Uwe Schabla Dipl.-Ing. Dietmar Schüwer
www.shell.de www.wupperinst.org
3 2
STORAGE & TRANSPORTATION SUPPLY PATHWAYS
20 11
PUBLISHED BY
Shell Deutschland Oil GmbH
22284 Hamburg
+ –
9 SUMMARY 62 4
ENERGY & ENVIRONMENTAL BALANCES APPLICATIONS 28
SCENARIOS FOR FUEL CELL VEHICLES 57
MOBILITY
APPLICATIONS
REFUELLING STATION VEHICLE OWNERSHIP 38
INFRASTRUCTURE 51 COSTS 47
STATIONARY ENERGY
6 APPLICATIONS 35
8 7
5
Design & Production: Mänz KommunikationINTRODUCTION Shell Hydrogen Study
Hard copies of the Shell Commercial Vehicle Study, the Shell
ENERGY OF THE FUTURE?
Passenger Car Scenarios (both also as an English summary) and
the Shell/BDH Domestic Heating Study (only in German) can be
ordered via shellpresse@shell.com.
Over the years Shell has produced a number of scenario dedicated business unit, Shell Hydrogen. Now, in cooperation
studies on key energy issues. These have included studies on with the Wuppertal Institute in Germany, Shell has conducted
important energy consumption sectors such as passenger cars a study on hydrogen as a future energy source.
and commercial vehicles (lorries and buses) and the supply of as part of a compound. If hydrogen is to What are the main conversion methods develops models, strategies and instruments
The study looks at the current state of hydrogen supply path- be used as an energy source in a future involved in using hydrogen for energy for transitions to sustainable development.
energy and heat to private households, as well as studies on
ways and hydrogen application technologies and explores the hydrogen energy economy, then first of all purposes? Alongside the mobility applica- Its work centres on the way in which
the state of and prospects for individual energy sources and
potential and prospects for hydrogen as an energy source in its origin needs to be clarified: Where does tions for hydrogen technology, are there challenges in terms of resources, climate
fuels, including biofuels, natural gas and liquefied petroleum
the global energy system of tomorrow. The study focuses on hydrogen occur? From which materials and any stationary applications for hydrogen as and energy influence and are influenced
gas.
the use of hydrogen in road transport and specifically in fuel how can it be produced, and using what a source of energy? by the economy and society. The “Future
Shell has been involved in hydrogen production as well as in cell electric vehicles (FCEVs), but it also examines non-automo- technical processes? If a future energy Energy and Mobility Structures” research
research, development and application for decades, with a tive resp. stationary applications. The focus of this study is the issue of
economy is to be sustainable, the way in group, which was involved in the study, is
sustainable mobility through fuel cells and
which it is generated is key. So what are concerned in particular with the transition
hydrogen (H2). When we think of hydrogen
the advantages and disadvantages of the to sustainable structures from a technical /
HYDROGEN – – as was interest in novel energy forms. RESEARCH OBJECTIVES and mobility, fuel cell electric vehicles,
various hydrogen supply pathways? structural and systems analytical point of
A PROMISING ELEMENT Nevertheless, issues around sustainability, AND KEY QUESTIONS in particular passenger cars, are what
view.
climate protection and environmental Highly developed energy systems rely come to mind. But hydrogen and fuel cells
More than 100 elements are known in protection began to have a growing influ- Shell scenario studies present facts, trends increasingly on electricity as a secondary can be used by other means of transport The project leader and coordinator of the
chemistry, over 90 of which occur naturally. and prospects on specific key energy too. Therefore, the aim of this study is to
ence on energy supply policy. This sparked energy source. Electricity has many Shell Hydrogen Study on behalf of Shell
Elements are substances which cannot issues in a compact form. As in the give an overview of the technical state of
a new interest in hydrogen as a clean and advantages as an energy source, but some was Dr. Jörg Adolf. The scientific coordina-
be broken down into simpler substances previous Shell studies on passenger cars, and prospects for hydrogen and fuel cell
sustainable energy option. disadvantages too: it can generally only tor on behalf of the Wuppertal Institute was
and from which all other substances are commercial vehicles, domestic heating technology in all transport sectors, including
be directly stored in small amounts and for Dr. Karin Arnold. She was supported by
formed. Hydrogen is an element – but not Over the past two decades, the energy and individual energy sources and fuels, non-road means of transport.
short periods of time, and its transportation Andreas Pastowski and Dietmar Schüwer.
just any element. Hydrogen is the smallest debate has been and is still dominated by the initial focus is on providing an expert
is mostly grid-based. Chemical energy The work was carried out under the
and lightest of all elements. Hydrogen was other energy sources – such as natural gas, analysis and assessment of a subject. After assessing the technological maturity
storage via hydrogen could represent an scientific supervision of Professor Manfred
the first element created in space after the biofuels/biomass and electricity. Throughout of motor vehicles and passenger cars in
There has certainly been plenty of alternative or an important supplement to Fischedick.
Big Bang. And it is the first element in the particular, we look at the costs and cost-
this period, however, intensive research and discussion and reporting on hydrogen, existing energy stores. If hydrogen is to
periodic table in modern chemistry. effectiveness of hydrogen mobility as an
development in hydrogen-related technolo- and it is an exceptionally simple element. play a part in the energy system of the The following authors at Shell also con-
important decision-making criterion, as well
gies has continued. Nonetheless, hydrogen At the same time, however, hydrogen is future, the possibilities for storing and trans- tributed to the scientific preparation of the
Hydrogen was discovered in the 18 th
as the development of a hydrogen supply
has so far failed to gain commercial not a familiar product, especially among porting hydrogen need to be analysed. study: Dr. Jurgen Louis, regarding technical
century as a flammable gas. Important infrastructure. Finally, since hydrogen-
acceptance either generally or in individual end users who are accustomed to petrol and scientific questions about hydrogen
technologies for producing and using powered vehicles are only viable if
application areas as a new energy source. and electricity. So far, any experience of In the past, debate about the use of hydro- and fuel cell technology, Uwe Schabla,
hydrogen were developed in the 19th and they can be operated more sustainably
Owing to high capital investment costs and hydrogen is limited largely to its use as a gen has centred above all on automobility. regarding stationary fuel cell applications,
early 20th century. Even then, its potential than today’s vehicles, we use scenario
a long useful life of energy infrastructure, feed material in chemical production and But hydrogen usage cannot be and is not and Dr. Christoph H. Balzer, regarding the
for the energy industry was recognised. techniques to estimate and assess possible
it takes considerable time for new energy as a technical gas in industry. limited to transport applications. In new preparation of energy and greenhouse gas
We now know that hydrogen has a very energy and environmental balances for
sources to capture a significant share of the technologies there are often synergies balances and scenario techniques.
high specific energy content (calorific or For that reason one of the most important future fuel cell passenger car fleets.
energy market. between different applications, and these
heating value). In some contemporary aims of the Shell Hydrogen Study is need to be taken into account when In addition, many other experts, decision
visions of the future, hydrogen played a to provide basic information about the
After decades of R&D as well as testing, it is looking at learning curves and economies AUTHORS AND SOURCES makers and stakeholders from science, busi-
prominent role as an energy source. element and about the use of hydrogen as
legitimate to ask: Is hydrogen the energy or of scale of (new) technologies. And when it Shell worked closely with the German ness and politics were consulted during the
at least an important energy of the future? an energy source. The first purpose of the
Hydrogen was given new impetus in the comes to the use of scarce resources (like research institute and think-tank Wuppertal preparation of the Shell Hydrogen Study.
study is to give an overview of the special
1960s by space travel, which relied heavily And, if so, when and how could hydrogen energy and fuels), competing uses need Institute to produce the Shell Hydrogen Shell would like to take this opportunity to
properties and advantages of hydrogen.
on hydrogen as an energy store, and in the develop into a leading energy source in to be considered. This raises the following Study. Back in 2007 the Wuppertal Insti- thank all concerned for their contribution
1970s as a consequence of the energy the global energy system? The intent of Hydrogen is one of the ten most common question: What (other) fundamental tute examined and evaluated the concept and cooperation. A selection of relevant
and oil price crises, when the search the Shell Hydrogen Study is to provide elements on the surface of the Earth that is application areas – as a material and an of “geological CO2 storage” as a possible data and sources can be found at the end
began for alternative energy concepts. qualified assessments and answers to these accessible to man. In nature, however, it energy source – are there for hydrogen? climate policy action for Shell (WI 2007). of the study.
During the 1990s energy prices were low questions. does not exist in pure form, but rather only And, with regard to energy applications: The Wuppertal Institute researches and
4 5>> In the beginning, there was hydrogen.
1 THE ELEMENT HYDROGEN Shell Hydrogen Study
+20°
3 PHASE DIAGRAM HYDROGEN
Water will be the coal of the future. Pressure (bar) +10°
Jules Verne
700 GH2 0
“The Mysterious Island“
1874
‒10°
350 GH2
VISIONS OF A HYDROGEN ECONOMY CcH2
‒20°
100
Solid ‒30°
Supercritical fluid
SH2
‒40°
Critical point 13 bar, ‒240˚
Liquid
10
‒50°
Almost since its discovery, hydrogen has played an important During the 1970s, under the impression of dwindling and LH2
NIST 2017; own diagram
part in contemporary visions of the future, especially in ever more expensive fossil fuels, the concept of a (solar) ‒60°
Gaseous
relation to the energy industry and locomotion. hydrogen economy was developed, with H2 as the central
‒70°
energy carrier. Since the 1990s, hydrogen and fuel cells
As early as 1874, the French science fiction writer Jules Verne have made huge technical progress in the mobility sector.
1 ‒80°
(1828 – 1905) in his novel “L’Île mystérieuse” (The Mysteri- After the turn of the century, not least against the background −260˚ −250˚ −240˚ −230˚ −220˚ +20˚
ous Island) saw hydrogen and oxygen as the energy sources of renewed global raw material shortages and increasingly Temperature (°C) ‒90°
of the future. In his vision, hydrogen would be obtained by the urgent questions of sustainability, the prospects for a hydro-
breaking down of water (via electrolysis). Water, resp. hydro- gen economy were considered once again (Rifkin 2002). The critical temperature and critical pressure characterise the the critical point, hydrogen becomes a supercritical fluid, -100°
gen, would replace coal, which at the time was the dominant critical point of a substance. For hydrogen the critical point which is neither gaseous nor liquid. Compared with that
energy source in the energy supply industry. More recently, the focus has increasingly been on hydrogen’s is approximately –240°C or 33.15 K and 13 bar. At the of methane, the vapour-pressure curve of hydrogen is very ‒110°
role in a national and global energy transition. Within this critical point of a substance the liquid and gas phase merge. steep and short – over a small temperature and pressure
In the 1960s, the successful use of hydrogen as a rocket context, the value added of hydrogen (from renewable ener- At the same time, the critical point marks the upper end of range. As a consequence, liquefaction takes place primarily -120°
propellant and of fuel cells to operate auxiliary power units gies via electrolysis) in an increasingly electrified energy the vapour-pressure curve in the pressure-temperature phase by cooling and less so by compression. By contrast, the
in space – especially in the context of the US Saturn/Apollo world has also been subject to discussion. Nevertheless, an diagram. The critical density at the critical point is 31 grams compressed storage of hydrogen (at 350 or 700 bar)
‒130°
space travel programme – provided further impetus to the important role is envisaged for hydrogen – especially as per litre (g/l). always takes place as a supercritical fluid.
‒140°
fantasies surrounding hydrogen. Also in the 1960s, first a clean, storable and transportable energy store – in an
passenger cars were fitted with fuel cells as basic prototypes electricity-based energy future (Nitsch 2003; Ball/Wietschel The melting point, at which H2 changes from the liquid to the In connection with temperature and pressure changes,
‒150°
resp. technology demonstrators. 2009). solid state of aggregation, is –259.19°C or 13.9 K under a special feature of hydrogen that has to be taken into
normal pressure and is thus slightly lower again than the consideration is its negative Joule-Thomson coefficient: when ‒160°
boiling point. This means that only the noble gas helium has air expands under normal conditions, it cools down – an
lower boiling and melting points than hydrogen. effect which is used in the liquefaction of gases, specifically ‒170°
1.3 PROPERTIES OF HYDROGEN usefulness of a substance and the way in temperature scale. Below this temperature
which it is handled; that applies in particu- hydrogen is liquid under normal pressure of in the Hampson-Linde cycle for the cryocooling of gases.
Under normal or standard conditions, The triple or three phase point of a substance is the point in Hydrogen behaves quite differently: it heats up when its flow ‒180°
hydrogen is a colourless and odourless lar also to the safe handling and storage of 1.013 bar, above this point it is gaseous.
the phase diagram at which all three states of aggregation is throttled. Only below its inversion temperature of 202 K
gas. Hydrogen is non-toxic and is not energy sources such as hydrogen.
are in thermodynamic equilibrium; for hydrogen this point is ‒190°
The state of aggregation is dependent not (approx. –71°C) does hydrogen demonstrate a “normal”
causing environmental damage – in that at –259.19°C and 0.077 bar. The triple point is also the Joule-Thomson effect. By contrast, for the main constituents of
PHYSICAL PROPERTIES only on temperature, however, but also on
‒200°
respect it is environmentally neutral. lowest point of the vapour-pressure curve. The vapour-pres- air, nitrogen and oxygen, the inversion temperature is 621 K
Hydrogen – by which both here and pressure. Gases can thus also be liquefied
In terms of the properties of substances, a by raising the pressure. However, there is sure curve indicates pressure-temperature combinations at and 764 K respectively.
below we mean dihydrogen or equilibrium ‒210°
distinction is made between physical and a critical temperature above which a gas which the gas and liquid phases of hydrogen are in equi-
hydrogen mixtures (H2) – exists in gaseous
chemical properties. Physical properties are can no longer be liquefied, no matter how librium. To the left of the vapour-pressure curve hydrogen is Density is a physical quantity that is defined by the ratio ‒220°
form under normal conditions. For a long
determined by measurement and experi- high the pressure. In the case of hydrogen liquid, to the right it is gaseous. To the right of and above of mass per volume. Gases have a very low density in
time hydrogen was believed to be a
mentation, while chemical properties are permanent gas, which cannot be converted the critical temperature is –239.96°C ‒230°
observed by means of chemical reactions. into either of the other two states of aggre- (33.19 K). If hydrogen is to be liquefied, its
Gaseous, cannot be liquefied ‒240°
One of the most important chemical prop- gation, i.e. liquid or solid (Hollemann/ temperature must be below this point. Critical point ‒240°
erties of energy sources is the behaviour Wiberg 2007). ‒250°
of the substance when it is burned (redox Similarly, once it reaches a sufficiently Gaseous @ atmospheric pressure, can be liquefied under pressure
Boiling point ‒253°
behaviour), either in a hot conversion In fact its boiling point is very low, at high pressure, a gas can no longer be Liquid @ atmospheric pressure
Triple point ‒259° Melting point ‒260°
process or by cold electrochemical com- –252.76°C; this is close to the absolute liquefied, even by lowering the temperature Solid @ atmospheric pressure
bustion. Physical and chemical properties zero temperature of –273.15°C and cor- further. This pressure is known as the critical
of substances influence both the use and responds to 20.3 Kelvin (K) on the absolute pressure, and for hydrogen it is 13.1 bar. Absolute zero temperature: ‒273.15° = 0 K
8 91 THE ELEMENT HYDROGEN Shell Hydrogen Study
comparison to liquid and solid substances. 4 IGNITION RANGE OF FUELS
At a temperature of 0°C or 273.15 K, the IN SUMMARY
density of hydrogen in its gaseous state Hydrogen Mixture too lean
Ignition range Hydrogen is the most common substance in the universe and Owing to its physical properties, hydrogen is an almost
is 0.089 grams per litre (g/l). Since air
Methane Mixture too rich the richest energy source for stars. permanent gas. Hydrogen gas only liquefies at very low
is around 14 times heavier than gaseous
Hydrogen (H) is the first element in the periodic table of temperatures (below –253°C).
hydrogen, with a density of 1.29 g/l, Propane
modern chemistry and is also the smallest, lightest atom. As hydrogen has a very low density, it is usually stored
hydrogen has a high buoyancy in the
Pure hydrogen occurs on Earth only in molecular form (H2). under pressure. Liquefaction increases its density by a
atmosphere. Hydrogen volatilises quickly Ethanol
Hydrogen on Earth is usually found in compounds, most factor of 800.
Gestis 2017; own diagram
in the open air.
Petrol notably as water molecules (H2O). The characteristic property of hydrogen is its excellent
Liquefaction plays an important part in the flammability. Due to its chemical properties, hydrogen
Hydrogen has long been regarded as an energy carrier of the
storage and transport of hydrogen as an Biodiesel has to be handled with care.
future. It is also discussed as the foundation of a sustainable
energy source. In the liquid state at the boil-
Diesel
hydrogen economy.
ing point, at –253°C (20.3 K) and 1.013
bar, hydrogen has a density of 70.79 g/l. 20% 40% 60% 80% 100%
At the melting point, at –259.2°C (13.9 K)
and 1.013 bar, its density is 76.3 g/l concentration of 4 vol%, the upper limit at amounts of energy – in other words high
(Hollemann/Wiberg 2007).
Liquefaction increases the density of
77 vol%. The liquid and gaseous fuels that
are currently in use have much lower
temperatures – are needed to form new
molecular bonds. Hydrogen exists almost
2 SUPPLY PATHWAYS
hydrogen by a factor of around 800, and ignition ranges. Only ethanol, which is entirely in atomic form only above a tem-
the storage volume falls correspondingly. contained in petrol for example, has a perature of 6,000 K. In addition to high
For the purposes of comparison, when higher upper explosive limit, at 27 vol.%. temperatures, catalysts are also often used
Liquefied Petroleum Gas (LPG) is liquefied, for chemical reactions involving hydrogen.
Its combustion properties make hydrogen
the density or volume factor, depending an interesting combustion fuel: If hydrogen
on the proportion of butane/propane, is Molecular hydrogen (H2) is relatively inert.
were to be used in internal combustion
around 250; when methane is liquefied Nevertheless, by punctual heating of a 2:1
engines, the broad ignition limits would
to form Liquefied Natural Gas (LNG), the hydrogen/oxygen mixture (oxyhydrogen
allow for extremely lean air/hydrogen gas
factor is around 600 (Shell 2013, 2015). gas) to approximately 600°C, a chain
mixtures. While petrol engines run at a
reaction can be started which leads to an
Another relevant feature of hydrogen is its stoichiometric combustion air ratio (λ = 1)
explosive propagation of the temperature
extremely high diffusibility. As the lightest and modern diesel engines typically oper- Hydrogen naturally only exists in (chemi- from renewable energies becomes Depending on the production method, the
rise throughout the entire gas mixture.
gas, hydrogen can diffuse into another ate at λ = 2, lambda values of up to 10 cally) bound form, so it has to be produced increasingly available. hydrogen product gas that is obtained
The water vapour formed by the high heat
medium, passing through porous material would be possible with hydrogen-operated by means of specific processes in order to includes undesired substances (such as
of reaction then achieves a much greater Figure 6 shows the basic process stages for
or even metals (Hollemann/Wiberg combustion engines (Eichlseder/Klell be used for chemical or energy purposes. carbon monoxide, CO) and impurities; this
volume than the original hydrogen/oxygen industrial hydrogen production. For the most
2007). This can also cause materials to 2012). Lean combustion is more efficient A number of suitable processes are availa- applies especially to the thermochemical
mixture. The sudden propagation of the important processes various raw materials
become brittle. In storage, the high diffu- than stoichiometric combustion and thus ble and are in use today. Most of today’s and biochemical methods. Depending on
water vapour leads to a so-called can be used without fundamental changes
sivity requires the use of special materials minimises fuel consumption. global hydrogen production is based on the intended use the product gas has to
oxyhydrogen or Knallgas reaction. to the process. Hydrogen production pro-
for the storage containers – for example The autoignition temperature of pure hydro- fossil energy sources (see figure 5). undergo a subsequent purification; in some
cesses include steam reforming, currently the
austenitic steels or coatings with diffusion gen is 585°C, which is higher than that of For that reason, to avoid an oxyhydrogen/ cases the raw materials for the hydrogen
Only a small proportion of hydrogen is most important production process, as well
barrier layers. Otherwise, diffusion losses of conventional fuels. However, the minimum Knallgas reaction when working with production also have to be prepared.
produced by electrolysis, the electricity as partial oxidation, autothermal reforming
the stored hydrogen can occur. ignition energy of 0.02 MJ is much lower hydrogen, an oxyhydrogen gas sample for which currently stems from a variety of and gasification of solid fuels. In addition, The processes for producing hydrogen
than that of other fuels. Hydrogen is there- should always be taken or oxygen should sources. For the future it can be assumed the electrolysis of water with electricity from are described in more detail below,
CHEMICAL PROPERTIES
fore classified as an extremely flammable only be added to the hydrogen at the that hydrogen production from electrolysis various sources and the use of industrial followed by an analysis of the energy and
The most characteristic chemical property gas. However, a simple electrostatic dis- moment of ignition (Hollemann/Wiberg will rise significantly if (surplus) electricity “residual hydrogen” is considered. greenhouse gas emissions balances for the
of hydrogen is its flammability (Hollemann/ charge (with an energy of around 10 MJ) 2007). Likewise, in gas mixtures containing
Wiberg 2007). When hydrogen is burned would also be sufficient to ignite almost any hydrogen and chlorine gas or fluorine, the
in ambient air, the flame is scarcely visible other fuel. The maximum flame velocity of reaction to hydrogen chloride or hydrogen 5 SHARE OF PRIMARY ENERGY CARRIERS IN GLOBAL HYDROGEN PRODUCTION
in daylight, since the flame is characterised hydrogen is 346 cm/s, which is around fluoride can result in explosive exothermic
by low heat radiation and a high ultraviolet eight times higher than that of methane reactions. Electricity Coal Oil Gas
component. In comparison with other fuels, (43 cm/s). 5% 11% 16% 68%
it is striking that hydrogen is combustible in Its chemical properties make hydrogen an
a very broad concentration spectrum. The Regarding the thermal behaviour of hydro- excellent combustion and automotive fuel.
ignition range of hydrogen, marked by its gen, it has been found that because of the Nevertheless, handling hydrogen requires
lower and upper explosive limit, is corre- strong bond between the hydrogen atoms care, and in particular compliance with
spondingly large: the lower limit is at a of the hydrogen molecule, considerable safety regulations. E4tech 2014; own diagram
10 112 SUPPLY PATHWAYS Shell Hydrogen Study
The carbon monoxide content is further materials, rather than relying on light the preceding partial oxidation of the fuel.
6 PROCESSES FOR PRODUCING HYDROGEN reduced through further chemical conver- hydrocarbons (Zakkour/Cook 2010). As the feedstock is not fully converted, but
PRIMARY ENERGY SECONDARY ENERGY CONVERSION INTERMEDIARY PRODUCT FINAL ENERGY CARRIER sion processes such as CO methanation used for heat supply, this has a detrimental
and selective CO oxidation. The purity Autothermal reforming (ATR) impact on the efficiency.
Solar, Wind Electricity
of the product gas is further increased by Autothermal reforming is a combination
ELECTROLYSIS Air or a mixture of oxygen and water
subsequent CO2 washing and other of steam reforming and partial oxidation.
vapour or carbon dioxide is used as the
physical purification steps (DWV 2015). The reforming of methane takes place in
oxidant or gasifying agent. As in partial
Algea from accordance with the following reaction
If other starting materials such as heavy fuel oxidation, the product gas that is formed
sunlight equation:
BIOCHEMICAL HYDROGEN oil are used, the steam reforming process is at its purest when oxygen is used, since
Biomethane CONVERSION in principle proceeds in the same way. 4 CH4 + O2 + 2 H2O → 4 CO + 10 H2 the use of air introduces quite a high
Biogas However, the production of the synthesis proportion of nitrogen into the process.
Biomass Ethanol In the ATR process combining steam
Vegetable Oils gas in the first step differs. reforming and partial oxidation, the high The composition of the resulting synthesis
hydrogen yield is determined by the steam gas, in other words the proportion or purity
Partial oxidation (POX) reforming step. The necessary process of hydrogen, is also influenced by the
THERMOCHEMICAL Partial oxidation is understood to be the heat is supplied internally by the partial gasification temperature and pressure, by
Natural Gas CONVERSION
exothermic conversion of mainly heavy oxidation step. the cooling capacity of the reactor, and
hydrocarbons (such as heavy fuel oil or by the residence time of the product gas in
SMR
The advantage of the autothermal reaction, the reactor (Görner et al. 2015).
Steam methane reforming coal) with the aid of oxygen (O2). Thermal
Oil Syngas which is not dependent on an external heat
partial oxidation takes place under high
POX supply, is more or less offset by increased
Partial oxidation pressure and at high temperatures from 2.2 BIOGENIC
investment and operating costs for the air
around 1,250°C to around 1,400°C. As PRODUCTION
Coal separation unit and a more complicated
ATR heat is released, no external heat source is
Autothermal reforming flue gas purification process.
needed other than the partial combustion
of the raw material. The POX reaction GASIFICATION On a global scale, the production of
equation for hexadecane, a long-chain hydrogen from biomass has so far been
Gasification is a traditional method for
different hydrogen supply pathways, based is used as an oxidant, the product gas also however, other light hydrocarbons such as alkane found in gas oil, looks like this: negligible. In the long term, however, from
producing fuel gases. It denotes the
on the Well-to-Tank approach which con- contains nitrogen. The reaction takes place liquefied petroleum gas or naphtha can the perspective of low-CO2 hydrogen
C16H34 + 8 O2 → 16 CO + 17 H2 reaction of a carbon carrier (such as coal)
siders the production of the primary energy at high temperatures (between approx. also be used (Zakkour/Cook 2010). The production, it is conceivable that this
with oxygen or an oxygen-containing
source through to provision of the hydrogen 700°C and 900°C) and the conversion starting material has to be prepared first; As in steam reforming, a synthesis gas is manufacturing option could play a part –
gasifying agent to form a synthesis gas. In
in a storage system or (vehicle) tank. is assisted by a catalyst. In addition to the this usually involves removing sulphur, which produced that is converted to hydrogen provided that sustainability requirements for
this process, the raw material that is used is
raw material, reforming requires an oxidant, attacks the catalyst. In the next step, by means of the water gas shift reaction the biomass that is used can be reliably met
The summary of the energy and green- first dried and broken down thermally in the
which supplies the necessary oxygen. methane and water are converted into and gas treatment (Zakkour/Cook 2010). and that sufficient quantities are available.
house gas balances is based on the Well- absence of air to form carbon and hydro-
Based on the oxidant, three basic methods hydrogen by the following reactions: In this process, the longer the chain length
to-Wheel balances of the Joint Research gen compounds, which are then partially In principle there are two methods for
can be identified (Aicher et al. 2004): of the hydrocarbon used, the lower the
Center of the European Commission, Eucar CH4 + H2O → CO + 3 H2 combusted by oxidation (Eichlseder/Klell producing hydrogen from biomass:
hydrogen yield.
and Concawe (JEC 2014); therefore the Steam reforming: Pure water vapour is 2012). In accordance with the following thermochemical or biochemical methods.
■■ CH4 + 2 H2O → CO2 + 4 H2
processes behind (JEC 2014) are briefly used as the oxidant. The reaction requires A substantial difference from steam reaction equation, the heated carbon and The possibility of generating electricity from
outlined. In addition, an overview of the the introduction of heat (“endothermic”). A synthesis gas is formed, consisting reforming is that O2 is used instead of water vapour produce a synthesis gas biomass and converting it into hydrogen by
hydrogen manufacturing costs for the predominantly of hydrogen and carbon water vapour as the oxidant. This O2 is consisting of CO and H2. electrolysis is covered under electrolysis.
■■ Partial oxidation: Oxygen or air is used monoxide, with small amounts of carbon
various processes is provided. usually produced in an air separation unit, C + H2O → CO + H2
in this method. The process releases heat THERMOCHEMICAL METHODS
dioxide, water vapour and residual which considerably increases the energy
(“exothermic”). By the subsequent water gas shift reaction
hydrocarbons. Both the carbon and the consumption of partial oxidation. However, Thermochemical methods are in most cases
2.1 PRODUCTION ■■ Autothermal reforming: This process is a H2 molecules can form a compound with this is offset to some extent by the extraction CO again is converted to form CO2 and based on the gasification or pyrolysis of
FROM FOSSIL combination of steam reforming and par- oxygen. In this process as little hydrogen of heat from the reaction. In addition, the further water vapour to H2. The various solid or liquid biomass to form a synthesis
ENERGY SOURCES tial oxidation and operates with a mixture as possible should oxidise to form water, use of O2 rather than air more or less reactor types are distinguished by the gas, followed by a further treatment to
of air and water vapour. The ratio of the so that a high yield of H2 can be achieved. eliminates the occurrence of nitrogen in the design of the gasifier. The gasification produce H2 (as with fossil fuels). The “solid
REFORMING two oxidants is adjusted so that no heat Suitable catalysts can help with this (Aicher process itself can be performed under biomass” category includes primarily
water gas shift reaction, resulting in a lower
Reforming of fossil hydrocarbons is by far needs to be introduced or discharged et al. 2004). energy consumption (for separation and excess pressure or at atmospheric pressure. woody and stalky biomass, i.e. forest wood
the most widespread method of hydrogen (“isothermal”). The higher the operating pressure, the or waste wood and straw, but also stalky
In the next step, CO and remaining water purification).
production. Reforming is the conversion of better the performance of the gasifier. energy crops such as miscanthus. Timber is
Steam reforming are converted further to H2 and CO2 in the
hydrocarbons and alcohols by chemical All in all, partial oxidation is less efficient Gasification generally involves the input of most suitable for gasification, since stalky
Steam methane reforming (SMR) so-called water gas shift reaction (DWV
processes into hydrogen, giving rise to the than steam reforming; at the same time, heat (endothermic reaction = allothermal materials like straw contain too many impu-
2015).
by-products water (vapour), carbon mon- The raw materials for steam reforming are however, it offers the advantage of being gasification). An autothermal process rities and, given the tendency to form ash,
oxide and carbon dioxide. If (ambient) air mostly natural gas and water; in principle, CO + H2O → CO2 + H2 able to convert a wider range of raw management, however, uses the heat from are not an ideal feedstock for gasification
12 132 SUPPLY PATHWAYS Shell Hydrogen Study
processes. Of the various timbers that can into oxygen and hydrogen by biophotolysis 7 THE PRINCIPLE OF ELECTROLYSIS 8 ELECTROLYSER KEY FEATURES
be used, untreated wood is most suitable, (Hy-NOW 2012). There are a number
i.e. forest wood or coppiced wood from of methods available for converting sugar O2 H2 Temperature°C Electrolyte Plant size Efficiency Purity H2 System costs Lifespan Maturity level
short-rotation coppices (SRCs). and starch and lignocellulose from biomass
2e–
into hydrogen. They are based on the use
High-pressure gasification of biomass is Alkaline Commercially used in
of various microorganisms and (with the Electrolysis 60 – 80
Potassium- 0.25 – 760
1.8 – 5,300 kW 65 – 82 %
99.5 % 1,000 – 60,000 –
industry for the last 100
complicated by the fact that waste wood hydroxid Nm3 H2/h – 99.9998 % 1,200 €/kW 90,000 h
exception of one process) draw at least (AE) years
tends to be contaminated with stones or
some of the energy they need from sunlight.
CATHODE
ANODE
nails, which can damage the pressure Proton
The most relevant methods are dark fermen- ½ O2 2 OH– H2 Commercially used
vessel. For that reason, wood gasification Exchange
Solid state 0.01 – 240 99.9 % 1,900 – 20,000 – for medium and small
tation using heterotrophic bacteria, photo- 2e – Membrane 60 – 80 0.2 – 1,150 kW 65 – 78 %
according to (JEC 2014) is usually carried membrane Nm3 H2/h - 99.9999 % 2,300 €/kW 60,000 h applications
fermentation using photosynthetic bacteria, Electrolysis
(2 SUPPLY PATHWAYS Shell Hydrogen Study
category retains hydrogen on site for its for example) but also in terms of the efficiency (in MJ primary energy / MJ
SECTOR COUPLING: HYDROGEN AS A STORAGE MEDIUM AND POWER - TO - X own use. Only “by-product” hydrogen has size and location of the production unit: hydrogen produced) and the associated
no further use within the process or on site; depending on demand and on the supply specific greenhouse gas intensity (g CO2
In the course of the energy transition, the proportion of renewable carriers, the Power-to-X concept (PtX), can result into a number of only this category can be made available equivalent / MJ hydrogen produced),
strategy, hydrogen is generated decen-
energies in electricity generation has risen markedly. Wind power different utilisation pathways (Rieke 2013; Dena 2015; NREL for other applications, such as fuel cell tralised in small plants directly at the point where CO2 equivalent is referred to below
and photovoltaics have seen the greatest expansion. However, the 2016; LBST/Hinico 2016): feeding small amounts of hydrogen into electric vehicles. of use or in large centralised plants and as CO2.
availability of these intermittent and non-dispatchable renewable the natural gas network; hydrogen methanation with CO2 to form subsequently transported by pipeline or
energies (variable renewable energies, VREs) fluctuates over time. CH4 and introduction of the methane obtained into the natural gas However, by-product hydrogen is also The results are shown in figures 10 and 11.
lorry to the dispensing stations.
At the same time, because of its physical properties, supplying network as a replacement gas (both Power-to-Gas). However, this widely used today. In the chemical industry All pathways are shown as being “central-
electricity requires a constant balancing of supply and demand. latter option requires a concentrated CO2 source at the methanation it is used for additional processes such In practice there will also be combinations ised” in large production units, where “cen-
location. Finally, the stored hydrogen can be converted back into as hydrogenation. It is at least used to of centralised and decentralised pro- tralised” still means domestic production.
If the proportion of renewable energies exceeds roughly one-
electricity via fuel cells (Power-to-Power). produce electricity and heat, as in the duction, in regional supply for example, The possibility of producing hydrogen on
quarter of electricity generation, special/additional measures are steel industry for example. However, this but for simplification reasons they are a large scale using solar power in North
necessary in order to integrate fluctuating renewable energy Other concepts include: using hydrogen from renewable energies by-product hydrogen could be replaced by not described here. Thermal conversion Africa or offshore wind power in Northern
supplies. Otherwise it may be necessary to limit the production (“green hydrogen”) in fuel refining (hydrogenation) or for fuel natural gas as an energy source, and thus from the fossil fuels coal, oil and above Europe, for example, and shipping it to
or use of renewable energies. production by means of synthesis into liquid fuels (Power-to-Liquids) be made available. Moreover, the layout all natural gas still dominates. As part Germany has been excluded from this
Alongside other demand and supply measures, energy storage can and using the generated hydrogen as a basic chemical (Power-to- of new or retrofitted plant sites is such that of the process of decarbonising energy analysis. For various reasons, not only
play an important part in improved system integration. Until now, Chemicals; Power-to-Plastics). all input and product streams are used, as production and energy consumption, the technical but also geopolitical, the impact
pumped-storage hydro power plants have dominated electricity stor- a result of which the availability of individ- role of fossil fuels, especially coal, is being of implementing this option, which is more
Power-to-X is currently still in the research and development stage.
age capacity – although they account for less than 3 % of global ual “by-products” is falling sharply overall. reduced. In fact, the specific greenhouse of a long-term objective, cannot yet be
Various projects explore fundamental questions of feasibility and
electricity generation. Short-term electricity storage in batteries for gas emissions from hydrogen generated by assessed. The sensitivity analysis illustrates
economic viability (BMVI 2014; Graf et al. 2014; Sundmacher The project “CO2 ReUse NRW” (WI/
small plants is developing dynamically. However, longer-term stor- coal gasification are more than twice the the effects of decentralised production,
2014; Zuberbühler et al. 2014). Covestro 2015) provided a detailed
age of larger surplus amounts of electricity requires new types of ones from hydrogen produced by natural characterised firstly by the less efficient
insight into the production, distribution and
storage, such as chemical storage in the form of hydrogen (IEA One disadvantage of PtX concepts is, undoubtedly, the large num- gas reforming (JEC 2014). In the long term, production and secondly by the elimination
use of industrial hydrogen. The bulk of
2016b). ber of conversion steps. This leads to overall low efficiencies along thermal conversion will increasingly be or at least the considerable shortening of
industrial hydrogen is produced specifically
the entire supply and use pathways (IEA 2015b). On the other superseded by electrolysis (using electricity the transport route.
Hydrogen can be obtained by electrolysis from electricity produced for its intended purpose (mostly chemical
hand, hydrogen as an energy storage medium and/or its potential from renewable energies).
with surplus renewables. If there is a corresponding energy demand, industry). Within this context, refineries too In considering the energy efficiency of the
for conversion in further energy carriers allows for an accelerated
the hydrogen can fulfil it directly. However, it can also be stored in have become net consumers of hydrogen. For that reason, this section examines only different hydrogen production and supply
expansion and use of surplus renewable energies. Not least for that
bulk tanks as pressurised gas and retrieved when supplies are low. Only a relatively small proportion of 9 % two main hydrogen production pathways: pathways, differences between the primary
reason, an important role has been given to hydrogen as an energy of the total amount of hydrogen produced steam reforming from natural gas and energy sources are evident (figure 10).
Finally, the hydrogen can be converted into other energy carriers. store and to PtX supply and use pathways towards a greenhouse can be considered to be available for electrolysis. No further consideration is The EU electricity mix/electrolysis pathway
Converting renewable electricity via hydrogen into other energy gas neutral energy industry (UBA 2014). external applications. Therefore, little or no given to supply pathways based on coal stands out because the cumulated energy
industrial hydrogen is available for other and (heavy fuel) oil. Energy and green- input is 4.6 to 5 times higher than that
9 POWER - TO - X PATHWAYS Methanation applications, such as transportation fuel. house gas balances are considered for the of the other pathways. By contrast, the
selected pathways and their variants and differences between natural gas reforming
By contrast, according to a survey by (Cox
production costs are estimated. and electrolysis from variable renewable
Methane 2011), in the USA there is still potential
POWER-TO-GAS PtCH4 energies (in this case wind) in terms of the
CO2 in residual hydrogen. The most important The energy and greenhouse gas balances height of the bars are slight.
source for this is the chlor-alkali electrolysis; for the above-mentioned hydrogen pro-
however, landfill gas and biogenic gases duction pathways are presented and Nevertheless, the type of energy source
are also regarded as a potential source analysed with reference to (JEC 2014). used must be taken into account: electro-
H2 of by-product hydrogen. In this context (JEC 2014) contains energy and lysis from renewable energies uses more
O2 H2 considerable importance is attached to the greenhouse gas balances for a large than 70 % renewable energies and
PtH2 PtH2 PtH2 availability of gas processing plants. number of energy and fuels pathways. The consumes only small amounts of fossil and
H2O data is updated regularly and forms an nuclear resources (for transport and for
Gas grid
Power generation Power Electrolysis
acknowledged basis for analysing energy production and dismantling of the wind
2.5 COMPARISON OF sources and fuels in the European context. energy converters used). By contrast, the
SUPPLY PATHWAYS According to (JEC 2014) the primary proportion of renewable resources in the
energy share (subdivided into fossil, nuclear gas reforming pathways is less than 5 %.
Storage caverns
The previous sections of this chapter and renewable energy sources) and the One exception to this rule is the “biogas
introduced various hydrogen production resulting greenhouse gas emissions for mix” pathway, half of which is supplied
Petrol, Diesel, technologies. These technologies can each conversion stage and transport mode by waste-based biogas and which thus
POWER-TO-LIQUIDS Jet fuel
CO2 be differentiated not only in terms of the are calculated and mapped. The results contains a higher proportion of renewable
Synthesis energy sources used (fossil or renewable, show for each pathway the specific energy energy.
16 172 SUPPLY PATHWAYS Shell Hydrogen Study
In terms of greenhouse gas emissions the 10 ENERGY INPUT FOR HYDROGEN SUPPLY 12 HYDROGEN PRODUCTION COSTS
reforming pathways represent an average
4.5 MJ/MJ H2 12 €/kg H2 LBST/Hinico 2015; Grube/Höhlein 2013, own diagram
value which does not vary substantially
according to the origin of the natural gas Current
3.5 10
or the type of import (as Compressed Natu- Projected
Renewables
ral Gas, CNG, by pipeline or in liquefied Min. - Max.
Nuclear 8
form as LNG, Liquefied Natural Gas). The 2.5 Fossil
JEC 2014; own diagram
greenhouse gas intensity can be reduced 6
significantly by adding processed biogas, 1.5
so-called biomethane, which has similar 4
properties to natural gas. However, this is 0.5
2
very much dependent on the origin and the
type of the raw materials from which it is
EU Gas-Mix Biogas-Mix LNG EU Electricity-Mix Renewable Electricity
produced: The use of biomethane derived Reforming Reforming Reforming Electrolysis Electrolysis
Centralised Gas Reforming Decentralised Gas Reforming Centralised Electrolysis Decentralised Electrolysis Centralised Biomass Decentralised Biomass
from municipal waste results in significantly
lower greenhouse gas emissions than
biomethane based on energy crops
or slurry (DBFZ 2014). The addition of 11 GREENHOUSE GAS EMISSIONS OF HYDROGEN SUPPLY
biomethane to natural gas and its use in 2.6 PRODUCTION COSTS – et al. 2013; DBFZ 2007; Sattler 2010; The same is true for electrolysis: the spread
hydrogen production generally occurs as 250 g CO2/MJ H2 CURRENT AND PROJECTED Smolenaars 2010; Tillmetz/Bünger 2010; of costs for centralised plants is smaller than
a balance sheet calculation rather than by Trudewind/Wagner 2007). The pathways that for decentralised plants. One reason
physically transporting the biomethane to 200 Essential parameters of the various pro- in question are centralised and decentral- for this may be that decentralised plants are
the reforming plant. Centralised Paths Decentralised Paths duction pathways also include, in addition ised natural gas reforming, centralised and frequently not used at optimum capacity,
150 to the energy uses and greenhouse gas decentralised electrolysis of (wind) elec- and the variations in utilisation have an
Even more relevant than the type of gas
JEC 2014; own diagram
emissions described above, the production tricity, and centralised and decentralised even greater impact on production costs
used for reforming is the greenhouse gas than they do in a centralised plant.
100 costs. These are not included in (JEC 2014) biomass gasification and reforming. The
intensity of the electricity used for electro-
but have been added from other literature analysis has been supplemented with the
lysis. In terms of the carbon footprint, the EU According to these figures, hydrogen from
50 references. The structure and components data from (LBST/Hinico 2015).
electricity mix pathway and the electrolysis centralised and decentralised electrolysis
from renewable energies pathway differ by of the pathways in the literature differ in Finally, the timeliness of the data should be plants can be produced with production
a factor of 17. some details, such as plant size and taken into consideration: most of the studies costs ranging from almost 6 €/kg H2 (for
EU Gas-Mix Biogas-Mix LNG EU Electricity-Mix Renewable Electricity capacity utilisation, raw material costs, etc., that were analysed quote data from the centralised plant) to nearly 8 €/kg H2
If solely renewable electricity is used, the Reforming Reforming Reforming Electrolysis Electrolysis
(for decentralised electrolysis). Another
from the pathways considered above. methods that had been implemented at
hydrogen that is produced is almost emis- key input variable, along with capacity
the time of publication. Based on personal
sion-free, with around 13 g CO2/MJ H2. utilisation and full load hours achieved, is
Here only the pure production costs are information from the authors, these values
On the other hand, if the average Euro- parison: if hydrogen is to be produced by As a consequence of the high proportion the electricity price, which in the considered
considered; infrastructure and distribution are still up-to-date. Therefore they are
pean electricity mix is used for electrolysis, electrolysis from a partially decarbonised of coal used in its production, the German references varies between 6.5 and 10 EUR
costs (for road transport) are covered reproduced in figure 12 as the current
the greenhouse gas emissions produced electricity grid with the same greenhouse electricity mix has a higher CO2 intensity. cents/kWh.
elsewhere. Key controlled variables for status. The cost data from the cited studies
are some 2.2 times higher than in natural gas intensity as for the natural gas reform- However, the conclusions that can be the analysis and compilation of production are summarised in this figure. This has been The production costs for the centralised
gas reforming. ing pathway, specific greenhouse gas drawn are not fundamentally different. costs are the costs or prices of the primary done by calculating a weighted average, biomass-based pathways, at an average
Therefore, if hydrogen is to be made emissions from the electricity that is used energy sources (natural gas, biomass, elec- while the deviation from the minimum or
There are also similar programmes and of around 3.3 €/kg H2 up to a maximum
available sustainably and on a large scale, must be about 56 g CO2/MJ electricity. tricity, etc.) and energy costs for conversion; maximum value is shown in the shaded
resulting studies in other regions of the of 7.4 €/kg H2, lie somewhere between
only electrolysis using electricity generated Compared with the current levels of the type, size, capacity and utilisation of bars. In addition, three of the studies indi-
world, for example in California and other those for natural gas reforming and
from renewable energy sources offers the approximately 150 g CO2/MJ electricity, the conversion plant and the conversion cate costs for the years 2020 (or 2019)
states of the USA. The Well-to-Wheel electrolysis. Here too the dependency on
possibility of providing a low-CO2 fuel. the grid greenhouse gas intensity would and 2030 in two different scenarios; where
emissions for typical hydrogen production efficiency or yield of hydrogen. biomass production costs should be noted;
However, if a reliable supply of larger therefore have to be reduced by approxi- available these are shown in yellow in the
pathways were analysed by the Argonne depending on what sustainability require-
amounts of electricity is needed for the mately two-thirds. figure.
National Laboratory in the “Greenhouse (Grube/Höhlein 2013) compiled the ments are implemented, these costs could
transport sector, surplus renewable elec- production costs for hydrogen generated rise sharply in future if sustainable biomass
The values for the selected hydrogen pro- gases, Regulated Emissions, and Energy It is obvious that the range of production
tricity is no longer sufficient for hydrogen by various pathways. For their cost compi- as a resource becomes scarce. In the short-
duction pathways are taken from the JEC use in Transportation” model (GREET costs from centralised natural gas reforming
production. Rather, the required electricity lation they drew on a number of studies, to medium-term outlook (2020 and 2030),
study (JEC 2014) and reflect the situation 2015). The values are in the same order is narrow. Production costs of between
must be produced specifically for that the data situation becomes much sparser.
across Europe. It is assumed that these of magnitude as those from the JEC study mostly from 2010 to 2013 but including 1 and 2 EUR per kilogram of hydrogen
purpose.
values also apply to Germany. There are and therefore support the conclusions set two older studies from 2007: (Gökçek (average 1.4 €/kg) can therefore be For decentralised natural gas reforming
The scale of the transition of electricity differences between the EU and Germany, out here. 2010; Kwapis/Klug 2010; Lemus/Duart regarded as very probable. The variations only one set of cost data is available, with
generation that is needed shows a com- especially in regard to the electricity mix. 2010; Liberatore et al. 2012; Michaelis in decentralised reforming are much higher. no spread. For the biomass pathways the
18 192 SUPPLY PATHWAYS Shell Hydrogen Study
reference period, i.e. whether the figures gas reforming, centralised electrolysis and fully exploited by 2030, however. Photo- 13 ENERGY DENSITY OF FUELS
are a projection of the anticipated costs centralised biomass pathways in particular biological hydrogen production and the
50 Volumetric energy density MJ/l
or the current situation, is not always are expected to offer significant cost-saving solar thermal cycle are innovative pro-
transparent. The decentralised natural potential, which may not yet have been cesses but have not yet reached maturity.
40
Diesel
IN SUMMARY Biodiesel
Syn-Diesel
30 Petrol
Hydrogen can be produced from a large number of primary Hydrogen generated by electrolysis from renewable energies LIQUID LIQUEFIED GASES
LPG
energy sources and by various technical processes. The most produces the lowest greenhouse gas emissions. The primary
20 Bioethanol LNG
important primary energy source for hydrogen production energy input for electrolysis based on conventional electricity
today is natural gas, with a share of 70 %, followed by oil, coal is high, whereas that for natural gas and biogas reforming and
HYDROGEN
and electricity (as a secondary energy). Steam reforming (from for renewable electrolysis is low. However, electrolysis from 10 NATURAL GAS
natural gas) is the most important method of hydrogen renewable electricity uses a high proportion of renewable LH2 20.3ºK
CNG 200 bar
CGH2 700 bar
production. Electrolysis from electricity currently accounts for primary energy and only small amounts of fossil primary CGH2 350 bar
0 Natural Gas EU-Mix
around 5 % of global hydrogen production. In addition, only energy. Hydrogen
a small amount of unused residual hydrogen, generated as a 0 20 40 60 80 100 120 140
by-product of industrial production processes, is (still) available. Of all the production methods and supply pathways considered, Gravimetric energy density in MJ/kg
centralised hydrogen production is more cost-effective than
The importance of renewable energies in hydrogen production decentralised production. Centralised natural gas reforming is
is still low, although it will increase in future. Electrolysis from the most cost-effective method. For newer production pathways, 14 STORAGE METHODS
renewable electricity is seen as offering huge potential for the in particular electrolysis from renewables, substantial cost
PHYSICAL MATERIALS-BASED
future. Hydrogen can also be produced from biomass, pro- reductions still need to be achieved.
vided that there is sufficient sustainable biomass potential.
Compressed Gaseous Hydrogen
Liquefied Hydrogen
CGH2 Metal Hydrides
LH2
(350, 700 bar)
3 STORAGE & TRANSPORTATION Cryo-compressed Hydrogen Slush Hydrogen
Liquid Organic Sorbents
Hydrogen Carriers (MOFs, Zeolites,
CcH2 SH2
LOHCs Nanotubes)
It can be seen that hydrogen as an energy tested over lengthy periods of time, include storage and cooled hydrogen storage. As
A major advantage of hydrogen is that it can be produced Owing to its physical and chemical properties, the logistics carrier has by far the highest gravimetric physical storage methods based on either hydrogen has to be cooled down to very
from (surplus) renewable energies, and unlike electricity it can costs (i.e. storage and transportation) for hydrogen are higher energy density (lower heating value), at compression or cooling or a combination low temperatures in order to liquefy, the
also be stored in large amounts for extended periods of time. than those for other energy sources (such as liquid fuels). 120.1 MJ/kg. The higher heating value of the two (hybrid storage). In addition, term cryogenic hydrogen storage is also
For that reason, hydrogen produced on an industrial scale This chapter provides an overview of storage technologies (not shown in figure 13) is even as high a large number of other new hydrogen used. Finally, if compression and cooling
could play an important part in the energy transition. As a for hydrogen as an energy carrier. It then looks at transport as 141.88 MJ/kg. The mass-based storage technologies are being pursued are combined, this is also referred to as
chemical energy store, hydrogen could act as means of sector options in connection with the corresponding storage methods. energy density (LHV) of hydrogen is thus or investigated. These technologies can be hybrid storage.
coupling in integrated energy schemes. almost three times higher than that of liquid grouped together under the name materials-
hydrocarbons. based storage technologies. These can
High-pressure storage
include solids, liquids or surfaces. Figure 14
Compressed Gaseous Hydrogen, CGH2
However, the volumetric energy density
3.1 STORAGE heat that is released in a (theoretically) of the energy source, so it is stated in shows an overview of the available hydro- From production through intermediate
of hydrogen is comparatively low. Under
complete combustion. The higher heating MJ/kg or kWh/kg, for example. Using gen storage methods. As yet only physical storage and on to distribution to the end
ambient conditions the y-section is almost
The way in which an energy carrier is value (HHV) additionally takes into account the density (kg/l), the mass-based calorific storage by compression and liquefaction user, hydrogen is handled at different gas
on the zero-line, at just 0.01 MJ/l. There-
stored is greatly influenced by its energy the heat of condensation contained in the value can also be converted into a volu- have any commercial relevance. pressures. A low-pressure storage tank
fore, for practical handling purposes, the
content. The energy content of an energy water vapour, although this cannot be used metric energy density, which is then stated operates at just 50 bar. For intermediate
density of hydrogen must be increased PHYSICAL HYDROGEN STORAGE
source is determined by its calorific value by motor vehicles. in MJ/l or kWh/l. Figure 13 shows the storage in high-pressure tanks or gas
significantly for storage purposes.
or more precisely by its lower and higher gravimetric and volumetric energy densities Physical storage methods are the most cylinders, pressures of up to 1,000 bar
heating value. The lower heating value The calorific or heating value is a specific of hydrogen and other gaseous and liquid The most important hydrogen storage mature and the most frequently used. are technically possible. Only special solid
(LHV) is defined as the amount of usable quantity and is usually based on the mass energy carriers and fuels. methods, which have been tried and A distinction is made between high-pressure steel or steel composite pressure vessels
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