Factsheet to accompany the report “Pathways for energy storage in the UK”
Hydrogen storage and fuel cells
Brief description of technology
Hydrogen based energy storage systems (ESS) are a
promising technology that is receiving considerable
attention nowadays. This system differs from the
usual idea of an ESS, since it uses two different
processes for the complete cycle of energy
production, storage and use. For hydrogen
production, generally an electrolyser unit is used
which separates water into hydrogen and oxygen
using electricity. Normally hydrogen is stored in high
pressures tanks, although there are other
alternatives for storage. To produce electricity from
the stored hydrogen, an electrochemical device
called a Fuel Cell is used [1].
The Fuel Cell (FC) is the key for this technology. In
essence, this devices combines hydrogen (or
hydrogen-rich fuel) and oxygen to cleanly and
efficiently produce electricity. Through an
electrochemical process, the fuel is combined with
oxygen (1) from the ambient air to produce electricity
(2), heat and water (3) (See Figure 1). Unlike
batteries, FCs continuously generate electricity, as
long as a source of fuel is supplied. A FC system can
be a truly zero-emission source of electricity, when
the hydrogen is produced from non-polluting
sources. FCs do not burn fuel, making the process
quiet, pollution-free and two to three times more
efficient than combustion [2].
A single fuel cell consists of two catalyst-coated
electrodes (a porous anode and cathode) and an
electrolyte in between, similar to a battery. The
material used for the electrolyte and the design of
the supporting structure determine the type and
performance of the FC. The hydrogen used to power
them may come from a variety of sources. While
there are different FC types, all FCs work in a similar
way. More details about the specific types of FC
technologies can be found in [3], [4]
The amount of power produced by a FC depends on
several factors, including FC type, cell size, operating
Figure 1: Schematic of a Fuel Cell.
temperature, among others. A single FC produces
less than 1.16 volts which is hardly enough for even
the smallest applications. Therefore, individual FCs
are combined in series, into a FC "stack” adding up
the electricity generated. A typical FC stack may
consist of hundreds of FCs [4].
Nowadays, FCs – integrated with hydrogen
production and storage – are being developed to
power vehicles, commercial buildings, homes, and
small devices. These clean systems offer a unique
opportunity for energy independence, highly reliable
energy services, and economic benefits.
Technical/economic data
See Table 1. Regarding the costs of FCs, costs are
expected to drop from $3500/kW to $1000/kW in
2015 when manufacturing economies of scale are
reached [4][8].
Application/markets
There are three main markets for FC technology:
stationary power – primary source or backup power –
transportation power – potential replacement for
vehicles fuels – and portable power [4]. This ample
range of applications is due to its technical
capabilities, with a wide range of power (see Table 1)
and fast response (~1/4 cycle [5]). Suitability of FCs
for a specific application depends on the type of FC to
be used [4], [10].
Energy Density
(Wh/L –W/L)
Rated
Capacity
(MW)
Duration
(hours)
Cycle Efficiency
[%]
Energy Cost
[$/kWh]
Power
Capacity cost
[$/kW]
Life (years)
500+, 500–
3000 [3]
0-50 [3],
0.2[5], 0.2-2
[7],
0.2-10 [10]
Seconds – 24+
[3],
20–50 [3],
59 [5],
45–66[6],40-85
[7]
6-20 [3], 425725 [5]
10000+ [3],
4000-4500
[8],15003000 [7]
5-15 [3], 20
[5]
Table 1: Technical and economic data for hydrogen – fuel cells energy storage systems.
1
Factsheet to accompany the report “Pathways for energy storage in the UK”
Since hydrogen can be stored for a long timescale
with negligible losses, this technology is suitable for
seasonal storage and energy management,
specifically oriented to increase the integration and
variability management of renewable energy.
However, at this date there are still limitations due to
the low energy density of hydrogen that makes
difficult to storage large quantities in a manageable
volume. Additionally, in the field of large power
applications, FCs are a favorable alternative to
conventional electricity generation for distributed
generation and to provide energy to rural areas [2].
Back-up power for banks and telecommunications
companies receives interest recently [11].
Additionally, a potential synergy between electricity
and transportation sectors is envisioned, as there is
likely to be a large forthcoming integration of
renewable energy. Hydrogen can be produced and
stored to be used for stationary power systems
application, such as energy management. In parallel,
when there is an excess of renewable generation and
using proper a distribution infrastructure, hydrogen
can be shipped to near refueling stations for vehicles.
A joint market approach where renewable energy
and hydrogen are used to supply energy to the
electricity network and to vehicles is possible.
This combination may represent an additional effort
to encourage the investment in renewable energy
and hydrogen-FCs technologies, enhancing the
benefits and the competitiveness of both
technologies. Coherent regulation of these
complimentary markets is one of the key issues to be
addressed in the future.
Advantages/disadvantages
Hydrogen storage and FCs offer many advantages.
These systems are easily scalable, have a simple and
compact design, and reliable operation [4]. Most
importantly, while using hydrogen as fuel, this
technology is pollution-free and noiseless energy
system, which makes them suitable for the
decarbonisation of the energy matrix. In this regard,
this technology has the potential to reduce energy
use, pollutant emissions, and dependence on fossil
fuels. Technical data indicates that FC systems
perform with the highest efficiency compared to
conventional distributed energy systems [10].
Hydrogen can be stored with negligible losses for
long periods, and together with a fast FC response,
makes this technology suitable for storage needed
for renewable energy management in a wide range
of rated power.
Despite all the advantages, there are some
limitations for utilizing FCs. For instance, life span of
FCs shortens by pulse demands and impurities of gas
stream [10]. Additionally, there is a need to storage
hydrogen in large volumes, with still short power
rating for large scale applications. In other words, FCs
have a low power density per volume. Other
challenges for FC technology development are the
high costs and low durability.
Current status
Hydrogen generation, storage and FCs have been the
subject of many studies and developments around
the world. However, currently this technology is still
under development and only pilot/demonstration
projects have been undertaken. Before large scale
deployment of these technologies can occur, a
significant cost reduction and improvement in
durability is needed [8], [14].
Stationary power is the most mature application for
FCs. Approximately, 600 systems that produce 10
kilowatts or more have been built and operated
worldwide to date. It is estimated that more than a
thousand smaller stationary FCs (less than 10
kilowatts) have been built and operated to power
homes and provide backup power [4].
In applications with renewable energy, FCs are
playing an increasing ESS role. The first and largest
plant that integrates hydrogen and wind power has
been installed by Norsk Hydro and Enercon in Utsira,
Norway, in 2004, which operates as an isolated
power system. The system is enough to power 10
houses for 2–3 days without wind [12]. In the town of
Nakskov, Denmark, a wind-hydrogen project has
been successfully producing hydrogen since May
2007 [13]. Hydrogen is used to produce electricity
when demand exceeds generation, and the excess
oxygen is used for a waste water cleaning projects.
The Naval Air Warfare Center in China Lake,
California, is developing a system that will use solar
power to create hydrogen for use in a FC during
periods with insufficient sunlight. In Canada, a
partnership between the federal government, BC
Hydro, Powertech, and General Electric is converting
excess off-peak electricity into hydrogen, reducing
diesel consumption by an estimated 200,000 L/year
and greenhouse gas emissions by an estimated 600
tons per year. Germany’s Enertrag AG, one of the
world’s largest wind power companies, is building a
facility to use excess wind energy to produce
hydrogen for energy storage and for transport
applications [4].
2
Factsheet to accompany the report “Pathways for energy storage in the UK”
In June 2011, the U.S. Department of Energy (DOE)
published the 2010 FC technologies market report [4]
that provides and overview of trends in this industry
and markets, as well as summary of major projects
that were funded by the DOE and other funding
programs. The number of FCs units shipped from
North America quadrupled between 2008 and 2010.
The U.S. was the global leader in terms of total MW
shipped in 2010.
Worldwide there are substantial governmental
policies that have supported research and
development (R&D) and market activity. In California
residential FC demand has been supported as well as
in Japan, where sales exceeded 5,000 units in 2010
bringing to 13,000 the total installed [4]. In [16] an
estimation of the aggregated R&D investments
dedicated to these technologies is presented –
including the corporate R&D investments from
relevant EU-based firms and the public R&D funds
from EU Member States and the EU through the 6th
EU Research and Euratom Framework Programme.
Results indicate that hydrogen and FCs has attracted
the largest R&D investments among the non-nuclear
energy technologies, with €616 millions.
Time to commercialisation and R&D needs
Research continues in reducing cost and improving
durability, which are the two most significant
challenges to FC commercialisation. The outlook for
FCs remains very positive as the market integration is
increasing and costs are coming down and the
technical capabilities are improving.
Despite the significant progress in recent years, there
is still a need for further improvements; low carbon
and efficient hydrogen production and storage, and
develop new materials that will reduce the cost and
extend the life and efficiency of FC stacks. Highvolume manufacturing processes will also help to
make FC systems cost-competitive with traditional
technologies. In [11] a more specific discussion about
the different aspects that should be improved is
presented. Private industry research and public
support are critical to achieve these objectives.
The estimated cost of a transportation FC system in
2010 for high volume manufacturing (500,000 units
per year) is $51/kW (Figure 2). This is a reduction of
more than 80 percent since 2002 and approaches the
target of $30/kW established for 2015 by the DOE.
For stationary applications, the target is $750/kW in
2011. The DOE target of durability lifetime is greater
than 5000 h for transportation applications by 2015
and 40,000 h for stationary applications in 2011.
Currently, ~2500 h of lifetime was achieved for
Figure 2: DOE Projected Transport Fuel Cell
System Costs
transport, while 20,000 was obtained in 2005 for
stationary FCs [15].
Another 5-10 years of research activities are
anticipated prior to a worldwide deployment. FC
electric vehicle commercialization is expected in
Europe around 2015, led by Germany, and in Asia, led
by Japan and Korea (market report [4]).
Safety, security, environmental and public
perception issues
The major environmental problems associated with
hydrogen and FC are due to the materials used in
FCs. Carcinogenic asbestos membranes and potent
potassium hydroxide, for example, are currently used
in hydrogen-generating electrolyzers, and a variety of
toxic metals are used as catalysts or electrodes.
Hydrogen codes and safety regulations, as well as
products standards need revision to ensure better
harmonization of regulation. Finally, public
awareness of hydrogen and FCs remains low,
requiring further outreach and education (safety
codes and standards [4]).
References
[1]
M. Beaudin; H. Zareipour; A. Schellenberglabe;
W Rosehart. Energy storage for mitigating the
variability of renewable electricity sources: An
updated review. Energy for Sustainable
Development 14 (2010) 302–314.
[2]
FCE. Fuel Cell Energy Inc. white paper. Tech.
rep., Fuel Cell Energy; 2004. [Online]. Available:
http://www.fuelcellenergy.com/files/FCE%20W
hitePaper%20040308_2.
pdf.
[Accessed:
December 09, 2011].
[3]
H. Chen et al. Progress in electrical energy
storage system: A critical review/ Progress in
Natural Science 19 (2009) 291–312
[4]
U.S. Department of Energy. Energy Efficiency &
3
Factsheet to accompany the report “Pathways for energy storage in the UK”
Renewable Energy. Fuel Cell Technologies
Program
http://www1.eere.energy.gov/hydrogenandfuel
cells/fuelcells/index.html
[5]
Shoenung SM. Characteristics and technologies
for long- vs. short-term energy storage. United
States Department of Energy; 2001. March.
[6]
Schaber C, Mazza P, Hammerschlag R. Utilityscale storage of renewable energy. Electr.J.
2004;17(6):21–9 (July).
[7]
S. Mekhilef, R. Saidur, A. Safari; Comparative
study of different fuel cell technologies;
Renewable and Sustainable Energy Reviews,
Volume 16, Issue 1, January 2012, Pages 981989
[8]
European Parliament’s committee on Industry
Research and Energy (ITRE). Policy Department
Economic and Scientific Policy. Outlook of
Energy Storage Technologies. 2006 [Online].
Available:http://www.europarl.europa.eu/docu
ment/activities/cont/201109/20110906ATT260
09/20110906ATT26009EN.pdf
[9]
Oak Ridge National Laboratory. Bootstrapping a
Sustainable North American Proton Exchange
Membrane Fuel Cell Industry: Could a Federal
Acquisition Program Make a Difference?
October
2008.
[Online].
Available:http://cta.ornl.gov/cta/Publications/R
eports/ORNL_TM_2008_183.pdf
Management Study: Inventory of Energy
Storage Technologies” 2010. OctoberAvailable
[Online]
http://www.scotland.gov.uk/Publications/2010/
10
[15] Papageorgopoulos D. DOE fuel cell technology
program overview and introduction to the 2010
fuel cell pre-solicitation workshop in DOE fuel
cell pre-solicitation workshop. Department of
Energy, Lakewood, Colorado; 2010.
[16] Tobias Wiesenthal, Guillaume Leduc, Karel
Haegeman, Hans-Günther Schwarz. Bottom-up
estimation of industrial and public R&D
investment by technology in support of policymaking: The case of selected low-carbon energy
technologies.
Original
Research
Article.
Research Policy, Volume 41, Issue 1, February
2012, Pages 116-131.
[10] S. Mekhilefa, R. Saidurb, A. Safari; Comparative
study of different fuel cell technologies.
Renewable and Sustainable Energy Reviews 16
(2012) 981– 989.
[11] Yun Wang, Ken S. Chen, Jeffrey Mishler, Sung
Chan Cho, Xavier Cordobes Adroher; A review of
polymer electrolyte membrane fuel cells:
Technology, applications, and needs on
fundamental research Review Article Applied
Energy, Volume 88, Issue 4, April 2011, Pages
981-1007
[12] Nakken T, Strand L, Frantzen E, Rohden R, Eide
P. The Utsira wind-hydrogen systemoperational
experience. European Wind Energy Conference;
2006. p. 1–9.
[13] Alto P, Holeby. First Danish hydrogen energy
plant is operational. Renewable Energy.
[Online].
Available:http://www.renewableenergyworld.c
om/rea/news/article/2007/06/firstdanishhydrogen-energy-plant-is-operational-48873
2007 Jun. 8.
[14] The Scottish Government. “Energy Storage and
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