Nuclear Production of Hydrogen, Fourth Information Exchange ...

CHANGING THE WORLD WITH HYDROGEN AND NUCLEAR: FROM PAST SUCCESSES TO SHAPING THE FUTURE
Technologies for nuclear hydrogen production
Clean and sustainable ways of producing hydrogen rely on water splitting with electricity and heat
generated by CO 2 -free energy sources (renewable energies and nuclear).
As demonstrated by this NEA meeting, hydrogen production technologies are an area of
significant international activity and co-operation. Major research frameworks include the
International Partnership for the Hydrogen Economy (IPHE), the Generation IV International Forum,
Joint Technology Initiatives in Europe and leading research or industrial organisations represented at
this NEA meeting such as DOE-INL and ANL (USA), JAEA (Japan), BARC (India), European Framework
Programmes, CEA (France)…
Alkaline electrolysis is a mature technology. It features a good efficiency (~66% LHV), an excellent
lifetime of cell (above 20 years currently), and a production of 99.8% pure hydrogen at 30 bars. This
leads to a global efficiency of ~24% (based on a heat/electricity conversion efficiency of ~35%). The
main issue is the large fraction of the production cost (~80%) tied to the consumption of electricity
(typically 2.6 out of EUR 3.2/kg H 2 at EUR 54/MWh) [3.4 out of USD 4.2/kg H 2 at USD 70/MWh]. Besides,
progress is sought to reduce the investment cost.
The steam electrolysis at high temperature (600-800°C) features a potential efficiency of ~100%
LHV with extra heat available. Its technology benefits from current developments made of solid oxide
fuel cells. However, many uncertainties and issues remain to achieve a commercial viability.
Prominent issues include improving the reliability and the lifetime of electrolytic cells and stack of
cells and decreasing the investment and operating costs with a view to decreasing the currently
estimated production cost from 4 to about EUR 2/kg H 2 [from 5.2 to about USD 2.6/kg H 2 ].
The thermochemical cycles (S-I > 850°C) or hybrid cycles (S-electrolysis > 850°C) still feature
many uncertainties in terms of feasibility and performances. Uncertainties still exist in parts of the
flow sheet and technologies needed to provide high temperature heat whether from solar or nuclear
nature. Potential assets of thermochemical cycles lie in a theoretical potential for a global efficiency
above 35% and a scaling law of the hydrogen plant after the volume of reactants instead of the total
surface of electrolytic cells. In return, their practical feasibility and economic viability have to be
entirely demonstrated. Especially, a global efficiency above 30% is to be demonstrated to compete
with alkaline electrolysis. Moreover, the safety of co-located nuclear and chemical plants has to be
demonstrated.
All these processes will have to compete with steam methane reforming associated with carbon
capture and storage that is currently developed with prospects of commercialisation around 2015.
In Europe, the project “Cachet” for “Carbon capture via hydrogen energy technology” was launched in
2006 to address this issue. The goal is to capture and store 90% of the 8 tonnes of CO 2 released per
tonne of hydrogen produced, and to possibly reduce the production cost below the current cost of
EUR 1.8/kg H 2 [USD ~2.3/kg H 2 ]. Which leaves us with still about 1 tonne of CO 2 released per tonne of
hydrogen produced…
Beyond assessing technical feasibility and performances of the various hydrogen production
processes, the evaluation of the associated hydrogen generating cost and its breakdown into capital,
operating and energy costs are other important criteria to determine about R&D priorities. The same
holds for the capability of flexible operation that determines the potential for a variable or intermittent
production using off-peak electricity or the potential for use in systems co-generating electricity or
process heat together with hydrogen.
Furthermore, industrial prospects for high temperature electrochemical or thermochemical
processes and the temperature involved, together with non-hydrogen related applications of process
heat, will impact the development strategy of high or very high temperature reactors.
Carbon taxes
Clean hydrogen production processes, based on carbon-free energy sources and water splitting will
definitely be encouraged by carbon taxes that may apply to steam methane reforming and utilisation
of natural gas as an industrial heat source or reducing chemical agent.
NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010 29