STW-Alliander Call
31-05-2013
STW-Alliander Programme on Plasma Conversion of CO2
Call for proposals
1. The Challenge
The need and urgency to create a sustainable energy future has spurred innovation in the energy sector. A
multi-B€ energy technology market has emerged driven by investors and researchers. Countries like
China, Germany, Japan and the USA invest heavily in energy technology and are set to become future
market leaders. This new energy sector is knowledge based and relies on use inspired basic
multidisciplinary research.
Renewable energy powered by the sun including photovoltaic, concentrated solar or wind driven sources,
are expected to contribute significantly to the energy supply mix of 2025. A limitation to large-scale
deployment is the ill-matched supply-demand character of solar energy owing to its geographical and
temporal distribution over the earth surface, which does not correspond to demand. To overcome this
limitation, storage and transport must form an integral part of such energy system. Various schemes are
being explored with an aim to optimise energy efficiency, energy density and cost. One option is the
conversion of water into hydrogen another is the conversion of carbon dioxide into carbon monoxide,
subsequently processed into hydrocarbon fuel. These so-called Solar Fuels using CO2 and H2O as
feedstock, role-modelled by photosynthesis, will enable CO2-neutral power generation closely matched to
existing infrastructure for storage, transport and distribution. Re-utilisation of CO2 emitted from fossil fuel
burning power plants is a first step in realising a CO2 neutral infrastructure. The re-capture of CO2 emitted
from Solar Fuels burned and ultimately, the capture of CO2 directly from the atmosphere forms an
essential element of a CO2 neutral energy society.
Breakthroughs in science and engineering are required for the conversion step of raw materials into CO2
neutral fuels. One approach is based on direct conversion of solar energy into fuels integrated into a single
device; another is to use sustainably generated electricity to power individual processing steps, see Figure
1.
Figure 1. Central to this STW-Alliander call is
the energy-efficient conversion of CO2 and
H2O into Solar Fuels by means of plasma
chemical processes. The red and green boxes
indicate the research required: Conversion of
raw materials by plasma activation followed
by known chemistry to produce methane or
liquid fuel. The scheme is powered by the sun
or by sustainably generated electricity. The
Capture of CO2 to provide input and the
Separation of CO to deliver output requires
innovative solutions to be addressed.
To date, most research effort is directed at the splitting of water producing hydrogen as a fuel. Although
energy efficient, the high operating pressure and temperature required presents an engineering challenge.
A promising alternative is the dissociation of CO2 into CO and O2 by means of plasma activation. Taking
advantage of non-equilibrium plasma conditions high energy efficiency may be obtained. The CO
produced may be processed into liquid fuel by known chemistry, i.e. the water gas shift reaction followed
by the Fischer-Tropsch reaction. Alternatively, the Sabatier reaction may be used to produce methane gas
out of CO2 and hydrogen, see Figure 2.
STW-Alliander Call
31-05-2013
Figure 2. Schematic showing the
Solar Fuel production steps using
H2O and CO2 as feedstock. The
conversion of sustainably generated
electrical energy into chemical
energy by means of plasma
activation forms the central theme of
this STW-Alliander call.
Courtesy: Wim Haije at ECN.
Alliander, an energy transport company, provides funding to this call in order to facilitate the market
introduction of Solar Fuels and to ease the transition to a renewable energy based economy. Solar Fuels
bear great potential for growth in employment and offer new business opportunities, because:
1) The European Union has formulated the ambition to reduce CO2 emissions by 80% in 2050 mainly
directed at the housing and utility building sector 1. An investment of 200 B€ would be needed during
next decade. For the Netherlands alone 300 B€ is budgeted until 2050 to reach the CO2 emission
reduction target. These investments benefit energy saving measures and new (smart) electricity grid
development. However, Solar Fuels do not need this level of investment because it relies on existing
energy infrastructure.
2) Cost of energy transport and distribution by means of electricity is significantly more expensive
compared with gas. Per kWh energy transported, electricity costs about 7 times more than gas 2.
Provided the conversion of electricity into gas can be done efficient and cost effective, CO2 neutral
Solar Fuels are expected to become the primary energy carrier.
3) Solar Fuels offer one of the solutions to the imbalance between supply and demand of renewable
electricity generation.
4) Energy security is served by not relying on supply from politically unstable countries
Alliander is intent on facilitating Solar Fuels through its energy distribution networks (both gas and
electricity) in the Netherlands and abroad, thereby responding to the energy and climate policy of the EU
formulated in the Energy Roadmap 2050.
Parallel to this STW-Alliander call, an NWO call is issued on CO2 neutral fuels calling for basic research
exploring various options of CO2 conversion. The NWO programme forms part of the TKI Gas, the Dutch
Top-consortium for Knowledge and Innovation on Gas. The STW-Alliander call complements this NWO
programme and its link to the TKI-Gas by focussing on CO2 conversion by plasma activation. Where the
NWO CO2 neutral call focuses on understanding the underlying physics and chemistry of the CO2
conversion process, the STW-Alliander call considers the system as a whole. from energy production upto
application, utilizing plasma activation of CO2 . The priority of the research proposed must be the plasma
conversion step. In addition, a system analysis will be required covering the entire process chain. This
includes innovative new solutions for CO2 capture and CO separation suited to the plasma conversion
process.
2. State of the Art in Solar Fuel research
In the energy storage chain covering capture, conversion, separation and production of fuel, the weakest
link is the conversion step. Worldwide research focuses on the splitting of water by means of photoelectro catalytic processes. Classic electrolysis reaches an energy efficiency of 70-80% 3, but makes use of
precious metals as a catalyst, such as Platinum, which drives up cost. Avoiding scarce materials in
European Commission: “A Roadmap for moving to a competitive low carbon economy in 2050”, COM(2011) 112
final, 8 March 2011
1
Depending calculation method, grid utilization or grid capacity, the factors range is 3-10 per kWh for a
household in the Netherlands
2
Electrical energy efficiency converting water into hydrogen and oxygen using Pt electrodes, together with solar cell
efficiency of 20% leads to overall energy efficiencies of 14 to 16%
3
STW-Alliander Call
31-05-2013
alternative photo- and electro-catalytic schemes presents a challenge 4. Solid Oxygen Electrolysis Cells
based on layers of rare earth metal composites operate at high pressure and high temperature that
remains an engineering challenge.
To date no efficient photo or electro catalytic method is known for the dissociation of CO2 into CO and O2.
Thermal dissociation based on heat generated by concentrated solar power by means of nano-structured
metal oxides reaches an energy efficiency of less than 5% 5. Most efficient metal oxides are based on rare
earth metals such as Cerium.
3. Plasma activation of CO2
An innovative way to activate CO2 is by means of plasma. Power to generate the plasma derives from
renewable electricity. The research programme of the FOM Institute DIFFER is directed at plasma
activation of CO2 for the production of Solar Fuels. This research effort is open to collaboration. STWAlliander funding facilitates research groups in the Netherlands to effectuate this collaboration. The
research fits within the Top sector Energy, possibly Chemistry and will be of great innovative value
because:
• It offers a solution to the storage and transport problem of renewable energy
• The liquid and gaseous fuel produced feeds into existing oil and gas infrastructure
• The CO2 reactant is non-toxic, non-corrosive and non-flammable and can be stored at relatively
low pressure offering substantial safety and environmental benefits.
• Reutilising CO2 adds value to industrial point source emissions of CO2.
• Research into plasma based processing yields spin-off to the chemical process industry 6 .
• Employing abundant materials lowers the cost of industrial processing.
• Chemical process devices considered are stable and compact
The advantages of plasma activation of CO2 include:
• High energy efficiency (>50%) in the conversion of electrical into chemical energy
• High energy density in the fuel produced
• No need for electrodes and/or scarce catalytic materials
• Low gas temperature (< 600K) in processing plant, relaxing engineering requirements
• Instant start-stop of the plasma reactor with no thermo-mechanical fatigue allows tuning to
intermittent energy supply from renewable source
• Near-atmospheric pressure and flow (l/min vs. ml/min in the photo-electro catalytic scheme)
yields high throughput
Because of these advantages plasma activation of CO2 offers an interesting alternative to electrolysis of
water. The CO produced becomes the starting point of known chemistry to produce, for example, H2 by
means of the reverse water gas shift reaction:
CO + H2O  CO2 + H2
(1)
After which reaction the CO2 produced may be recycled to produce CO again.
Promising results on plasma activation are reported by a Russian group employing microwave generated
CO2 plasma, creating a supersonically expanding non-equilibrium condition, claiming energy efficiencies
in excess of 80% 7. Obtained during the Soviet era for military application, these results have never been
reproduced in the West. Furthermore, the separation of the effluent gas stream into its constituents CO2,
CO en O2 and the production of a sufficiently pure CO product required for subsequent processing has not
been demonstrated by this early work. Therefore, a number of research questions remain before this
novel method of energy conversion may be exploited commercially 8.
N.S. Lewis and D.G. Nocera, PNAS 103 15729 (2006)
Ratio of CO combustion energy to the energy required to produce CO from CO2 by solar photon energy.
6 Non-equilibrium plasma processing allows selective excitation of molecular modes that lower activation thresholds
and thus improve energy efficiency and selectivity of the chemical reaction involved. Plasma processing offers a new
approach to industrial chemical processing.
4
5
7
8
V.D. Rusanov, A.A. Fridman and G.V. Sholin, Sov. Phys. Usp. 24 447 (1981)
This list of research questions is not an exhaustive list
STW-Alliander Call
31-05-2013
4. Research Questions
The research questions to be addressed may be grouped as follows to include:
Input gas feed:
•
•
What are the gas purity requirements of the CO2 input gas stream and how does this
influence the overall energy efficiency
Novel innovative concepts of CO2 capture are required that match the flow and pressure
conditions of the plasma conversion step. Which carbon capture system is proposed and
what are the physics or chemical principles and what are the technological challenges
Plasma-activation:
•
•
•
•
•
•
•
•
•
What is the preferred technology for plasma generation and what is the optimal technology for
the plasma source.
What are the important energy loss processes, including radiation and how to minimise these by,
for example, an optical cavity or the re-utilisation of waste heat generated.
Is thermo-dynamic non-equilibrium essential in obtaining high energy efficiency in the plasma
activation process.
Which CO2 excitation lowers the activation threshold most and how to preferentially excite
specific molecular vibration modes?
What role is played by the reduced electric field and the electron energy distribution function of
the plasma? How to determine, optimise and control these parameters.
What is the role of the interaction of ro-vibrational excited molecules and ions with the reactor
wall and possibly with catalytic materials employed?
For industrial fuel production at high throughput would it be possible to operate at or above
atmospheric pressure.
How to understand and control plasma instabilities developing at high pressure.
How to upscale the reactor to large industrial plant.
CO gas separation and chemical post-processing:
• How to separate CO from the effluent gas stream consisting of CO2, CO en O2 and how to optimise
the energy efficiency of this step? Novel innovative concepts are required.
• Are non-equilibrium processes also effective in the chemical post-processing step considering CO
produced is ro-vibrationally excited
• How is the overall energy efficiency optimised? This may be different from the optimisation of
individual parts of the process, for example by optimising energy efficiency against particle
conversion efficiency.
System Analysis
• Analyse and evaluate the whole chain for Solar Fuel production on cost and energy efficiency at a
system level. Consider large scale concentrated production against small scale distributed
generation (for example, table top H2 production). How does an energy system based on SF
compare with alternatives?
5. Pilot scale facility at DIFFER
At the FOM-Institute DIFFER 9 a pilot scale plasma activation facility is being developed (~100
kW) based on a supersonic expanding microwave plasma. The first objective of this facility is to
demonstrate CO2 plasma dissociation at high energy efficiency. Preliminary results show energy
efficiencies for CO2 conversion in excess of 50% obtained at 3kW RF power (915MHz) where
~10% of the CO2 is converted in CO. Next step is the separation of CO from the exit gas stream.
This FOM-DIFFER pilot scale facility is open to collaboration with University groups and
Research Institutes in the Netherlands and abroad. Research proposals are solicited by a
consortium on the basis of joint programming providing complementary expertise, diagnostics
and facilities. The approach could include:
9
Financed from other source including TKI Gas of Top sector Energy
•
•
•
•
•
•
•
STW-Alliander Call
31-05-2013
Method to create atmospheric plasma and supersonic stream conditions such that translational
temperature is low (<100 K).
Application of synergistic catalytic processes in the CO2 plasma activation process.
Method to identify and minimise energy loss processes.
Method to efficiently and safely separate CO from the CO2, CO en O2 effluent gas stream
Innovative diagnostics to probe the local electric field and gas density/temperature, to measure
the electron energy distribution function and the vibrational excitation distribution function.
Diagnostics for control, safety and protection of the machine. This includes the control of plasma
instability at high pressure, the control and optimisation of the electron energy distribution
function, the control and safe handling of CO produced
System analysis of the entire processing chain on energy efficiency and cost.
6. Open call STW-Alliander
The objective of the STW-Alliander call is to create an effective research collaboration by means
of projects on Plasma activation of CO2 including but not limited to physics, chemistry and
electro-technical disciplines. An Industrial partner is required as part of the team. This Industrial
partner may or may not be Alliander. Preferred form of collaboration is through JointProgramming by the constituent organisations.
7. Budget
The total budget is 2M€ including an STW contribution of 1M€, an Alliander contribution 0.5M€
and an NWO-AB contribution of 0.5M€. It is envisaged that 3 to 4 joint projects may be funded.
8. Alliander Objectives
Alliander aims to facilitate the transition to a renewable energy society. The STW-Alliander research call is
directed at innovation in CO2 neutral fuel production by means of plasma activation of CO2. Alliander is an
energy transport and distribution company not licensed to produce energy. Therefore, Alliander research
is aimed at:
•
•
•
A future energy system based on CO2 neutral fuels,
Integration of CO2 neutral fuel in the existing energy system
Coupling of sustainably generated hydrogen H2 or methane CH4 into the gas transport and
distribution network.
8.1 System research on a future energy system
The current natural gas based energy system is optimised for the use of natural gas as an energy carrier.
The emerging technology of converting electrical energy to gas enables a host of system solutions that are
often more efficient and cheaper. For example, a pilot project uses bio-gas instead of natural gas as an
energy carrier. Here the question is whether it is more cost effective to adapt high efficiency domestic gas
burners to biogas rather than to upgrade the bio-gas to natural gas quality before feeding into the existing
gas distribution network.
The conversion of electricity to synthetic natural gas (SNG) is schematically shown in Figure 3. Various
forms of energy transport and distribution currently exist, including hydrogen, carbon monoxide,
methane, SNG or heat. All have their pros and cons. It should be noted that oxygen produced from CO2
dissociation is a valuable commodity for various industrial application.
STW-Alliander Call
Electricity
H2O
Electrolysis
31-05-2013
N2
H2
O2
Methanisation
CO2
CO2 activation
Gas Conditioning
SNG
O2
CO
O2
CH4
Heat
Heat
Figure 3. Solar Fuel production scheme: H2, CH4, SNG and Heat are utilised in an energy transport and
distribution system (SNG = synthetic natural gas).
Alliander is interested in alternative energy systems based on Solar Fuels. An important aspect is the
overall efficiency of the system. This includes the balance of supply and demand, central vs. distributed
production, choice of energy carrier, utilisation of waste heat, electricity production at the point of
consumption and oxygen utilisation.
8.2 Demonstration of SNG injection into the existing natural gas network.
Replacing the existing gas supply network for use of Solar Fuels is a radical step. Prior to such change the
existing, infrastructure should be utilised where possible. Feeding Solar Fuels into the existing gas supply
network therefore offers an attractive option. In order to exercise this option it is important to understand
and optimise the entire system starting from the solar input toward SNG end use. To address this
challenge close collaboration between sub-system experts is essential.
This call solicits for collaborative applied research projects carried out by a consortium with partners
offering expertise covering the entire energy supply chain from solar to SNG. This includes a proof of
principle feeding CO2-activated product gas into the Alliander gas network, which shall constitute the final
task in the research programme proposed. Expert partners carrying out this final task shall be included in
the proposal. This task may be accomplished through use of the DIFFER pilot scale reactor. Providing gas
network quality requires a dedicated research effort. It is proposed to inject a broad range of product
gases into the gas network including alternative Solar Fuels routes. In addition to chain demonstration,
the impact of “CO2 neutral methane” on the European gas network and the energy supply system in
general will be an important aspect of the system analysis called for.
STW-Alliander Call
Figure 4 shows an energy infrastructure based on hydrogen as developed by Audi.
31-05-2013