H2Tech - Q4 2022 - 19

SPECIAL FOCUS: FUTURE OF HYDROGEN ENERGY
Solid oxide electrolysis cell (SOEC):
Potential technology for low-cost green H2
S. ROY and M. ETHAKOTA, Technip Energies India Ltd., Noida, India
Achieving net-zero emissions by 2050
to restrict global temperature rise to 1.5°C
continues to be a significant challenge for
the global energy sector. According to the
International Energy Agency's (IEA's)
Annual Report 2021, there will be a huge
energy transition from fossil fuel to renewables
to 2050: it is forecast that almost
90% of electricity generation will come
from renewable sources, with wind and
solar PV together accounting for nearly
70%. While there will be a significant shift
towards electrification, some sectors will
be difficult to electrify, such as steel, cement,
chemicals, fertilizers, aviation, etc.
Hydrogen (H2
), and specifically green
H2 (H2
a key role in decarbonizing these sectors.
H2
made without fossil fuels), can play
can contribute to energy security
and environmental compatibility as an
alternative energy carrier-the energy
system has key features that include
availability, economic production, transportability,
transformability (into other
forms of energy) and environmental
friendliness. It has the potential to be
used as fuel for power and transportation.
Electricity and H2
mentary options
form complefor
transferring
and
storing energy for different end uses, offering
much more flexibility in optimizing
energy structures on a macro scale.
Both are efficient and easy-to-handle
and have near-zero emissions when used
(considering non-fossil origins).
H2
(CO2
combined with carbon dioxide
) to produce liquid synthetic fuels
may also contribute to a reduction in CO2
emissions. H2
or H2-rich liquid fuel (e.g.,
methanol) can be converted to electricity
for transport purposes via fuel cells. Also,
it can serve as a feedstock for various
chemical reactions to produce a range of
synthetic fuels and chemicals, potentially
decarbonizing these sectors.
Global H2
production must rise from
approximately 75 MMtpy to 500 MMtpy-700
MMtpy by mid-century to reach
net-zero CO2
-emitting methods: natuemissions
targets. Coupling
H2 production with renewables is a viable
production is from carpath
to achieve this. More than 95% of
today's global H2
bon-based, CO2
ral gas steam methane reforming (SMR)
and coal gasification.
Green H2
can be produced in several
ways using renewable energy sources like
solar, wind or nuclear (high- and lowtemperature
electrolysis, various thermochemical
and photochemical processes,
etc.). However, water electrolysis is the
most effective technique and is capturing
the market's attention.
The electrolysis of water to produce H2
has been studied for the last 100 yr. However,
at present, only less than 1% of H2
is
produced from the electrolysis of water due
to the high consumption of electrical energy
required to separate the water molecule
because water is a very stable molecule.
Nevertheless, as renewable power costs
have been decreasing significantly over the
years, H2
production through electrolysis
is encouraged, as this route is the most sustainable
process for producing H2
.
Several water electrolysis technologies
have been developed throughout the years.
At present, alkaline electrolysis (AE) and
proton exchange membrane electrolysis
(PEME) are proven as commercial technologies.
However, solid oxide electrolysis
(SOE) has attracted many to bring this
technology to market to achieve better
energy efficiency. Other water electrolysis
technologies-like anion exchange membrane
electrolysis (AEME) and protonic
ceramic electrochemical cell electrolysis
(PCECE), among others-are in the development
or demonstration stages and
are not discussed here.
Low-temperature electrolysis AE and
PEME are operated below 100°C, whereas
SOE operates at significantly higher
temperatures. Despite their lower operating
temperatures, high efficiency and
technological maturity, low-temperature
electrolysis cells cause high electrical energy
consumption. Thermodynamically,
the electrical energy demand to electrolyze
water decreases as the operating
temperature increases. Due to this, hightemperature
electrolysis like SOE could
achieve a 30%-40% reduction in electricity
consumption if integrated with external
process waste heat. Therefore, hightemperature
solid oxide electrolysis cells
(HT-SOECs) can produce the most costeffective
energy H2
temperature routes like AE and PEME.
This article explores several opportunities
to produce green H2
WATER ELECTROLYSIS
TECHNOLOGIES
Electrolysis is the most straightforward
approach now available to produce H2
directly
from water. Water electrolysis is the
dissociation of water using electricity to
generate pure H2
and oxygen as a byproduct.
In 1789, Jan Rudolph Deiman and
Adriaan Paets van Troostwijk first demonstrated
water electrolysis using an electrostatic
generator. Then, in 1888, Dmitry Lachinov
developed a method of industrial
synthesis of H2
and oxygen via electrolysis.
Based on operating temperature, the
electrolysis technologies can be categorized
into low-temperature electrolysis (LTE)
and high-temperature electrolysis (HTE).
Low-temperature electrolysis (LTE).
Low-temperature electrolysis of water
is presently the most mature method of
H2Tech | Q4 2022 19
compared with low,
mainly focusing
on SOEC technology and its advantages
and challenges.
H2Tech - Q4 2022

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