- Email: [email protected]
Pathways to a more sustainable production of energy: sustainable hydrogen—a research objective for Shell
International Journal of Hydrogen Energy 27 (2002) 1125 – 1129
www.elsevier.com/locate/ijhydene
Pathways to a more sustainable production of energy: sustainable hydrogen—a research objective for Shell J.W. Gosselink1 Shell Global Solutions International BV, Exploratory Research, P.O. Box 38000, 1030 BN Amsterdam, Netherlands
Abstract Towards a sustainable energy supply is a clear direction for exploratory research in Shell. Examples of energy carriers, which should be delivered to the envisaged sustainable energy markets, are bio-fuels, produced from biomass residues, and hydrogen (or electricity), produced from renewable sources. In contrast to the readily available ancient sunlight stored in fossil fuels, the harvesting of incident sunlight will be intermittent, e1cient electricity and hydrogen storage technologies need to be developed. Research to develop those energy chains is going on, but the actual transformation from current fossil fuel based to sustainable energy markets will take a considerable time. In the meantime the fossil fuel based energy markets have to be transformed to mitigate the impact of the use of fossil fuels. Some elements in this transformation are fuels for ultra-clean combustion (hydrocarbons and oxygenates), hydrogen from fossil fuels, fuels for processors for fuel cells, carbon sequestration. ? 2002 J.W. Gosselink. Published by Elsevier Science Ltd on behalf of the International Association for Hydrogen Energy. All rights reserved Keywords: Sustainable hydrogen
1. Introduction Towards a sustainable energy supply is a clear direction given by Sir Mark Moody Stuart, former Chairman of the Committee of Managing Directors of the Royal Dutch=Shell Group, who stated [1]: “We in Shell believe a major challenge facing society today is posed by three inextricably linked issues: (1) The world’s increasing demand for energy; (2) World population growth; (3) The need to assure a viable world for future generations. This threefold challenge has serious implications for the energy businesses and concerns over climate change are at the heart of it.” The steady growth of energy demand will be met by a range of energy sources, part of which renewable energy sources (wind, photovoltaics, biofuels, geothermal energy, etc.) are expected to grow signi@cantly in importance as also highlighted in Shell Group scenarios, see Fig. 1. 1
Tel.: +31-20-630-2313; fax: +31-20-630-3964 E-mail address: [email protected] (J.W. Gosselink).
Fig. 1. Increase of renewable sources in the energy mix (energy supply scenario (Shell Group Planning Energy Scenarios, Dynamics as Usual).
2. Future energy markets Sustainable development requires innovation to reduce the so-called “ecological footprint”. Such innovation may transform the way energy and energy carriers are produced, gradually shifting the emphasis away from the traditional
0360-3199/02/$ 22.00 ? 2002 J.W. Gosselink. Published by Elsevier Science Ltd on behalf of the International Association for Hydrogen Energy. All rights reserved PII: S 0 3 6 0 - 3 1 9 9 ( 0 2 ) 0 0 0 9 2 - 7
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J.W. Gosselink / International Journal of Hydrogen Energy 27 (2002) 1125 – 1129
Fig. 2. From re@ning of crude oil to the more sustainable production of energy.
hydrocarbon base, and ultimately yielding a sustainable mix of energy carriers and energy markets. Preparing for the anticipated future energy markets is one of the main drivers for exploratory and strategic research carried out in Shell. Reduction of the ecological footprint must be achieved in an economically sound and socially acceptable way. Hydrogen and electricity derived from renewable sources are likely to play a role, along with bio-fuels for transportation. We structure our thinking about future developments by distinguishing three diHerent future markets for energy carriers. These are expected to evolve in parallel to yield an increasingly sustainable mix. This mix will probably not be the same globally, but show distinct regional diHerences (see Fig. 2): A constrained hydrocarbon economy may develop to meet increasingly severe constraints with respect to supply, emissions and product quality. It will typically supply fuels (hydrocarbons and oxygenates) for ultra clean combustion to vehicles equipped with internal combustion engines. A hydrogen economy may be realised gradually, or take oH as the result of a game-changing innovation. In the hydrogen economy, fuel cells are the key energy providers both for stationary and mobile applications and hydrogen is the main fuel. The new fuel cell technologies, such as the (low temperature) proton exchange membrane fuel cell (PEMFC) and the high temperature solid oxide fuel cell (SOFC), hold the promise to develop into the ultimate universal, e1cient, clean and silent device for converting chemical energy directly into electricity. The optimal fuel for the PEMFC is pure hydrogen and the second best is reformate produced from a suitable feedstock, and hence the large-scale introduction of this technology will therefore inevitably lead to a considerable change in the energy infrastructure; less change will be needed for the SOFC, since it can be fuelled directly
from the existing natural gas grid (albeit that the compulsory spiking of natural gas with tetrahydrothiophene requires removal of this contaminant before reforming). Signi@cant inJuence can be expected from the totally diHerent scaling rules for electricity production with fuel cells as compared with conventional power production. The hydrogen economy as depicted here is by choice of de@nition based on fossil fuels. Typical products to be delivered to this market are hydrogen and fuels suitable for conversion in fuel processors for fuel cells. For both economies holds that intermediates have to be produced for the petrochemical industry. Furthermore, resource e1ciency based on petrochemical product lifecycles, increasing energy e1ciency, carbon sequestration, the use of renewable fuel components may contribute to the reduction of the ecological footprint. Sustainable markets could develop gradually or via a game-change scenario. We, of course, do not yet know the characteristics and contours of these markets, but it can be envisaged that energy and petrochemicals will be based not on fossil fuels, but on eco-e1cient Helio-technology. For instance, renewable hydrogen, green electricity, bio-fuels as energy carriers, plastics based on bio-sources may play an important role, applying closed-loop technologies, advanced materials, new market rules and redesigned value chains.
3. Towards constrained hydrocarbon and hydrogen economies 3.1. Main strategies To ensure a future balance between the energy demands and carrying capacity of the Earth there are three main strategies to follow: (1) Increase of the e1ciencies of the various energy chains; (2) Mitigating climate eHects of the use of fossil fuels; (3) Developing sustainable energy chains, based on contemporary sunlight (as opposed to sunlight captured in fossil fuels), e.g. application of biofuels and hydrogen from renewable sources, vide infra. Obviously, increase of energy e1ciency will always be important. New technologies have been developed over the last few decades, such as better construction materials and insulating foams for houses; multipane windows, high-e1ciency heating systems, combined heat and power stations, more e1cient engines, motor oils with better lubricity and lower viscosity, better fuels, more aerodynamic shapes of automobiles, larger aeroplanes, better turbines, etc. Mitigation of the climate eHects of the use of fossil fuels should be really considered as a transition measure, buying time to develop and implement the sustainable energy chains. This in principle means separating, removing and storing of the carbon or CO2 , vide infra. Shell, together with
J.W. Gosselink / International Journal of Hydrogen Energy 27 (2002) 1125 – 1129
industrial and academic partners, is very actively following these pathways, as will be shown in the next sections. 3.2. Clean fossil Shell is developing, in partnership with Siemens Westinghouse Power Corporation US, power plants, which are virtually free of emissions [2]. The heart of such a plant is a solid oxide fuel cell system. The plants will be fuelled with natural gas and produce electricity. The use of gas as fossil fuel clearly is in line with a de-carbonisation trend. The exhaust CO2 might be captured, concentrated and sequestered. Several options for sequestration in geological formations can be envisaged, all with diHerent ratings on relative capacity, relative costs, storage integrity and technical feasibility [3]: active oil wells, coal beds, depleted oil=gas wells, deep aquifers, mined caverns=salt domes. In addition to geological sequestration, chemical sequestration could be an even more socially acceptable route to abate the CO2 eHects on the climate. Due to the fact that CO2 is thermodynamically a very stable molecule, the chemical possibilities are in principle limited. One interesting option, which is currently pursued in R& D in Shell, is the reaction with minerals forming even more stable carbonates. This reaction that takes place in nature on a geological timescale is currently being accelerated catalytically in a reactor [4]. The combination of low carbon fossil fuel and CO2 sequestration can be considered as clean use of fossil fuel. It should be noted that sequestration has still to be proven to be a technically and socially fully acceptable intermediate solution. 3.3. Fuel processors as a 9rst step towards the hydrogen economy Shell has developed its own proprietary catalytic partial oxidation (CPO) technology to facilitate a gradual transition to a hydrogen economy [5]. Realising power provision to a hydrogen and sustainable economy will be fragmented and will involve a diverse mixture of diHerent fossil and renewable energy sources and carriers. Over a decade ago Shell researchers discovered a very e1cient and compact catalytic conversion technology (CPO) of gaseous hydrocarbons to synthesise gas, a mixture of carbon monoxide and hydrogen. Only a few years ago it was discovered that also liquid hydrocarbons could be converted via CPO, followed by a few other process steps, into hydrogen (and carbon dioxide). Together with International Fuel-Cells Corp. (IFC) Shell established Hydrogen Source as a commercial venture to ensure the implementation of the CPO technology as a means to provide fuel cells with hydrogen fuel. This technology will enable the conversion of both conventional fuels like gasoline or natural gas and bio-fuels like ethanol or biogas to clean hydrogen for fuel cell applications. Via this route the introduction of fuel cell cars can be facilitated, because the conventional transportation fuel infrastructure can be used. This could very well be the @rst step in the
1127
transition towards a (automotive) hydrogen economy. The next two steps required will be direct fuelling with hydrogen, when hydrogen distribution and storage have been developed, and the production of hydrogen from a renewable source, i.e. completion of the transition to a hydrogen based sustainable energy market. 4. Towards sustainable energy markets 4.1. Bio-fuels Shell is active on a commercial basis in solar photovoltaic manufacturing, biomass as fuel for power generation and wind projects. Shell researchers are also active in developing attractive options for conversion of biomass to bio-fuels. This is a typical example of research projects that are currently being carried out to support our sustainable development objectives. Electricity production from biomass tends to be non-competitive, because conventional fuels oHer relatively cheap solutions. Many routes have been explored to convert biomass into transportation fuels, e.g. gasi@cation followed by synthesis to methanol or diesel, fermentation to ethanol or biogas, etc. The current approach is to optimise the total value of crops by producing higher value products like food and @bre, and using “waste” (in fact biomass residues) to make other products such as bio-fuels, ethanol and electricity (see Fig. 3). In this way one would pro@t from cascading and create synergy rather than competition between the food and fuel industries for the same biomass feedstock. Research on bio-fuels has to take account of the needs of a number of traditional businesses if win–win options are to be developed. To compare biomass residue and crude oil in energy value, the annual world biomass residue (wood waste, straw, husks, pods, stalks) production equals half of the annual oil production. Bio-fuel components, blended with conventional fuels, would also form an attractive route for accelerated introduction of renewable
Towards a Sustainable Energy Supply: Biofuels Feedstocks specific characteristics Valuable Molecules
5 billion t/a biowaste equivalent to half of the oil production
Technologies New Developments Synergies
Products performance HSE; value - chemicals, solvents
$1000/t
- hydrogen
$1200/t
- transport fuels compon. $ 250/t - fuel oil - power to grid
$ 70/t $ 25/t
Key factors for successful development of biomass-to-biofuels chains: ·Target high value products (e.g. hydrogen, transportation fuel components) ·Make use of feedstock characteristics ·Develop new technologies (synergy between food and fuel industries)
Fig. 3. Towards a sustainable energy supply: bio-fuels.
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J.W. Gosselink / International Journal of Hydrogen Energy 27 (2002) 1125 – 1129
application distribution
harvesting
incident solar energy (also stored in wind, rain, and waves) wind wave hydropower power power
PV
heat space photocollection PV catalysis
electricity
biotechnology
radiation
biomass
?
gasification reforming
steam water electrolyses
water thermolyses molecular hydrogen at production site
pipeline
metal hydrides
molecular redox couples
carbon-based materials
?
molecular hydrogen applicable in end-device PEM fuel cell
combustion
?
power (electrical, mechanical)
Fig. 4. Sustainable hydrogen chain.
transportation fuels, bringing us step by step to a sustainable energy market. Targeting bio-fuels from biomass residues also sets challenges to the processes, rather making use of the molecules in the biomass residue (for instance oxygenates) than destroy them completely as, for example, by gasi@cation. Today, ethanol can be produced from a steadily widening range of feedstocks and if the key technologies continue to advance at su1cient pace, it could become a competitive component for blending into transportation fuels [6]. 4.2. Sustainable hydrogen Hydrogen from renewable sources might be considered as the ultimate clean and climate neutral energy system. A typical energy chain for sustainable hydrogen comprises the harvesting of sunlight into hydrogen as energy carrier, the storage and distribution of this energy carrier to the end-device where it is converted to power. Various options are envisaged for such a chain, see Fig. 4. A rollout of such a sustainable hydrogen chain in developed countries could go either gradually via a hydrogen economy based on fossil fuels or discontinuously in the case of inventions of disruptive technologies. For developing countries the situation may be diHerent. Introduction of such hydrogen chains for their fast growing primary energy demands might enable them to skip the stage of conventional, fossil fuel based, technologies=markets, and leapfrog directly to a sustainable economy, e.g. a sustainable hydrogen economy. A lot of research and development has to be carried out to make a sustainable economy happen, not only science and technical development, but also social aspects. A substantial corporate (Shell) eHort is being made to explore this social dimension of the triple bottom line (economy, ecology, social). In line
with this philosophy these aspects will also be addressed in the Dutch Hydrogen programme, a 6-year study on the development of a sustainable energy chain based on hydrogen [7]. An industrial consortium, in which Shell is participating, and NWO (Dutch science organisation) will lead this program. For the capturing of sunlight and the production of hydrogen various routes are possible. The most promising candidates to become important elements in the sustainable hydrogen chains are: (1) Water electrolysis, using renewably produced electricity and (2) biomass=biological processes. The electrolysis route is currently already achievable with ¿ 90% e1ciency. The required electricity can be produced from, e.g. wind power, wave power, hydropower, and photovoltaic. These electrolysis routes currently suHer from relatively high costs and ergo cost reduction obviously will be an important R& D target. A lot of research is being carried out to produce sustainable hydrogen via biomass=biological processes (BioHydrogen 2002 conference, The Netherlands, April 21–24), e.g. to improve overall e1ciency and to reduce cost, in order to make these routes economically feasible [8]. A wide variety of interesting routes are being reported, e.g. hydrogen production via biomass gasi@cation, via biogas steam reforming (biomass fermentation followed by methane conversion to hydrogen), via fermentation or enzymatic conversion of sugars, direct production by micro organisms (bacteria and algae), such as by algae via photosynthesis after a metabolic switch. Because fuel cells are the most logical end-devices, purifying the produced hydrogen is required, because they currently require extremely pure hydrogen (especially as regards hydrogen sulphide and ammonia). The best way to produce the hydrogen will have to be locally determined using the most optimal way
J.W. Gosselink / International Journal of Hydrogen Energy 27 (2002) 1125 – 1129
to capture the sunlight, while keeping an eye on the overall source-to-sink e1ciency of the chain. In contrast to the readily available ancient sunlight stored in fossil fuels, the harvesting of incident sunlight will be discontinuous. Therefore, e1cient electricity and hydrogen storage technologies must be developed, not only for stationary but also for mobile applications. There is currently no ideal means of storing electricity to provide for high demand at times of low primary power supply. Various hydrogen-storage options can be envisaged and are being investigated, e.g. liquid hydrogen, compressed hydrogen, metal hydrides, chemical hydrides, and modi@ed carbonaceous materials. To reduce the cost and technological barriers for hydrogen storage, the processes should be optimised, e1ciency increased, reaction speeds optimised, and in almost all cases costs decreased. Therefore thorough understanding of the chemistry and physics of the interaction of hydrogen with other materials is required. The growing trend away from traditional centralised (and largely fossil-powered) electricity generation towards distributed generation is reshaping the size and function of electricity networks, particularly in emerging countries where no e1cient established grid is in place. The inclusion of renewables (e.g. hydrogen via electrolysis and biomass=biological processes), as an intermittent energy source which is inherently small scale, is oHering a sustainable element in support of this trend, and the future application of fuel cells and e1cient energy storage devices (in the form of hydrogen or electricity) will also contribute. Signi@cant attention will then need to be paid to buHering of the networks and eHective integration of a more diverse mixture of energy sources and carriers, particularly if these are dependent to varying extents on renewable sources. Novel methods of linking different components will be required, and developments in solid-state switchgear, power electronics and energy conversion devices will contribute to this. Fully integrated power solutions will play a signi@cant role in the future; for example, a small- to mid-scale unit which can produce heat, electricity and hydrogen, or a compact hydrogen storage device placed in a fuel-cell car
1129
but which can also be used to supply domestic electricity at times of peak demand. Such a paradigm shift, from remote generation to more localised production and storage of energy (as both hydrogen and electricity), will require careful attention with respect to social acceptance, particularly in developed economies, where the consumer—both residential and industrial—has long been separated—both physically and mentally—from any manufacturing impacts of his power supply. Acknowledgements The author thanks his colleagues Dr. A.M.S. Elliott, Dr. H.P.C.E. Kuipers, Dr. F.G.M. Niele, Dr. C.J. Schaverien and Drs. J.P. Haan for their contributions to this paper and critically reviewing the manuscript. References [1] Moody-Stuart M. In: Safe climate, sound business. A speech given at the World Economic Forum in Davos, 28 January 2000. [2] Moody-Stuart M. Shaping the future of energy industries— an energy company perspective. OHshore Northern Seas Conference, Stavanger, August 22, 2000. [3] Herzog H, Drake E, Adams E. CO2 capture, reuse, and storage technologies for mitigation global climate change. A White Paper, Final Report. DOE Order No. DE-AF22-96PC01257. [4] Shell Venster Januari=Februari 2002. p. 22–3 [in Dutch]. [5] Kramer GJ et al., The determining factor for catalyst selectivity in Shell’s catalytic partial oxidation process. Fuel Chem Div Preprints 2001; 46(2):659 – 60. [6] Groeneveld MJ. Ethanol: it’s possible role in CO2 sustainability. ISAF XIII, Stockholm, Sweden, 3– 6 July 2000. [7] NWO Programme Sustainable Hydrogen (an environmentally clean energy carrier). Outline of a research programme, 12 June 2001. [8] Pedroni PM. Biohydrogen production technologies: a general overview and photofermentations as a speci@c case. BioHydrogen 2002, Ede, The Netherlands, April 21–24, 2002, Book of Abstracts. p. 22.
www.elsevier.com/locate/ijhydene
Pathways to a more sustainable production of energy: sustainable hydrogen—a research objective for Shell J.W. Gosselink1 Shell Global Solutions International BV, Exploratory Research, P.O. Box 38000, 1030 BN Amsterdam, Netherlands
Abstract Towards a sustainable energy supply is a clear direction for exploratory research in Shell. Examples of energy carriers, which should be delivered to the envisaged sustainable energy markets, are bio-fuels, produced from biomass residues, and hydrogen (or electricity), produced from renewable sources. In contrast to the readily available ancient sunlight stored in fossil fuels, the harvesting of incident sunlight will be intermittent, e1cient electricity and hydrogen storage technologies need to be developed. Research to develop those energy chains is going on, but the actual transformation from current fossil fuel based to sustainable energy markets will take a considerable time. In the meantime the fossil fuel based energy markets have to be transformed to mitigate the impact of the use of fossil fuels. Some elements in this transformation are fuels for ultra-clean combustion (hydrocarbons and oxygenates), hydrogen from fossil fuels, fuels for processors for fuel cells, carbon sequestration. ? 2002 J.W. Gosselink. Published by Elsevier Science Ltd on behalf of the International Association for Hydrogen Energy. All rights reserved Keywords: Sustainable hydrogen
1. Introduction Towards a sustainable energy supply is a clear direction given by Sir Mark Moody Stuart, former Chairman of the Committee of Managing Directors of the Royal Dutch=Shell Group, who stated [1]: “We in Shell believe a major challenge facing society today is posed by three inextricably linked issues: (1) The world’s increasing demand for energy; (2) World population growth; (3) The need to assure a viable world for future generations. This threefold challenge has serious implications for the energy businesses and concerns over climate change are at the heart of it.” The steady growth of energy demand will be met by a range of energy sources, part of which renewable energy sources (wind, photovoltaics, biofuels, geothermal energy, etc.) are expected to grow signi@cantly in importance as also highlighted in Shell Group scenarios, see Fig. 1. 1
Tel.: +31-20-630-2313; fax: +31-20-630-3964 E-mail address: [email protected] (J.W. Gosselink).
Fig. 1. Increase of renewable sources in the energy mix (energy supply scenario (Shell Group Planning Energy Scenarios, Dynamics as Usual).
2. Future energy markets Sustainable development requires innovation to reduce the so-called “ecological footprint”. Such innovation may transform the way energy and energy carriers are produced, gradually shifting the emphasis away from the traditional
0360-3199/02/$ 22.00 ? 2002 J.W. Gosselink. Published by Elsevier Science Ltd on behalf of the International Association for Hydrogen Energy. All rights reserved PII: S 0 3 6 0 - 3 1 9 9 ( 0 2 ) 0 0 0 9 2 - 7
1126
J.W. Gosselink / International Journal of Hydrogen Energy 27 (2002) 1125 – 1129
Fig. 2. From re@ning of crude oil to the more sustainable production of energy.
hydrocarbon base, and ultimately yielding a sustainable mix of energy carriers and energy markets. Preparing for the anticipated future energy markets is one of the main drivers for exploratory and strategic research carried out in Shell. Reduction of the ecological footprint must be achieved in an economically sound and socially acceptable way. Hydrogen and electricity derived from renewable sources are likely to play a role, along with bio-fuels for transportation. We structure our thinking about future developments by distinguishing three diHerent future markets for energy carriers. These are expected to evolve in parallel to yield an increasingly sustainable mix. This mix will probably not be the same globally, but show distinct regional diHerences (see Fig. 2): A constrained hydrocarbon economy may develop to meet increasingly severe constraints with respect to supply, emissions and product quality. It will typically supply fuels (hydrocarbons and oxygenates) for ultra clean combustion to vehicles equipped with internal combustion engines. A hydrogen economy may be realised gradually, or take oH as the result of a game-changing innovation. In the hydrogen economy, fuel cells are the key energy providers both for stationary and mobile applications and hydrogen is the main fuel. The new fuel cell technologies, such as the (low temperature) proton exchange membrane fuel cell (PEMFC) and the high temperature solid oxide fuel cell (SOFC), hold the promise to develop into the ultimate universal, e1cient, clean and silent device for converting chemical energy directly into electricity. The optimal fuel for the PEMFC is pure hydrogen and the second best is reformate produced from a suitable feedstock, and hence the large-scale introduction of this technology will therefore inevitably lead to a considerable change in the energy infrastructure; less change will be needed for the SOFC, since it can be fuelled directly
from the existing natural gas grid (albeit that the compulsory spiking of natural gas with tetrahydrothiophene requires removal of this contaminant before reforming). Signi@cant inJuence can be expected from the totally diHerent scaling rules for electricity production with fuel cells as compared with conventional power production. The hydrogen economy as depicted here is by choice of de@nition based on fossil fuels. Typical products to be delivered to this market are hydrogen and fuels suitable for conversion in fuel processors for fuel cells. For both economies holds that intermediates have to be produced for the petrochemical industry. Furthermore, resource e1ciency based on petrochemical product lifecycles, increasing energy e1ciency, carbon sequestration, the use of renewable fuel components may contribute to the reduction of the ecological footprint. Sustainable markets could develop gradually or via a game-change scenario. We, of course, do not yet know the characteristics and contours of these markets, but it can be envisaged that energy and petrochemicals will be based not on fossil fuels, but on eco-e1cient Helio-technology. For instance, renewable hydrogen, green electricity, bio-fuels as energy carriers, plastics based on bio-sources may play an important role, applying closed-loop technologies, advanced materials, new market rules and redesigned value chains.
3. Towards constrained hydrocarbon and hydrogen economies 3.1. Main strategies To ensure a future balance between the energy demands and carrying capacity of the Earth there are three main strategies to follow: (1) Increase of the e1ciencies of the various energy chains; (2) Mitigating climate eHects of the use of fossil fuels; (3) Developing sustainable energy chains, based on contemporary sunlight (as opposed to sunlight captured in fossil fuels), e.g. application of biofuels and hydrogen from renewable sources, vide infra. Obviously, increase of energy e1ciency will always be important. New technologies have been developed over the last few decades, such as better construction materials and insulating foams for houses; multipane windows, high-e1ciency heating systems, combined heat and power stations, more e1cient engines, motor oils with better lubricity and lower viscosity, better fuels, more aerodynamic shapes of automobiles, larger aeroplanes, better turbines, etc. Mitigation of the climate eHects of the use of fossil fuels should be really considered as a transition measure, buying time to develop and implement the sustainable energy chains. This in principle means separating, removing and storing of the carbon or CO2 , vide infra. Shell, together with
J.W. Gosselink / International Journal of Hydrogen Energy 27 (2002) 1125 – 1129
industrial and academic partners, is very actively following these pathways, as will be shown in the next sections. 3.2. Clean fossil Shell is developing, in partnership with Siemens Westinghouse Power Corporation US, power plants, which are virtually free of emissions [2]. The heart of such a plant is a solid oxide fuel cell system. The plants will be fuelled with natural gas and produce electricity. The use of gas as fossil fuel clearly is in line with a de-carbonisation trend. The exhaust CO2 might be captured, concentrated and sequestered. Several options for sequestration in geological formations can be envisaged, all with diHerent ratings on relative capacity, relative costs, storage integrity and technical feasibility [3]: active oil wells, coal beds, depleted oil=gas wells, deep aquifers, mined caverns=salt domes. In addition to geological sequestration, chemical sequestration could be an even more socially acceptable route to abate the CO2 eHects on the climate. Due to the fact that CO2 is thermodynamically a very stable molecule, the chemical possibilities are in principle limited. One interesting option, which is currently pursued in R& D in Shell, is the reaction with minerals forming even more stable carbonates. This reaction that takes place in nature on a geological timescale is currently being accelerated catalytically in a reactor [4]. The combination of low carbon fossil fuel and CO2 sequestration can be considered as clean use of fossil fuel. It should be noted that sequestration has still to be proven to be a technically and socially fully acceptable intermediate solution. 3.3. Fuel processors as a 9rst step towards the hydrogen economy Shell has developed its own proprietary catalytic partial oxidation (CPO) technology to facilitate a gradual transition to a hydrogen economy [5]. Realising power provision to a hydrogen and sustainable economy will be fragmented and will involve a diverse mixture of diHerent fossil and renewable energy sources and carriers. Over a decade ago Shell researchers discovered a very e1cient and compact catalytic conversion technology (CPO) of gaseous hydrocarbons to synthesise gas, a mixture of carbon monoxide and hydrogen. Only a few years ago it was discovered that also liquid hydrocarbons could be converted via CPO, followed by a few other process steps, into hydrogen (and carbon dioxide). Together with International Fuel-Cells Corp. (IFC) Shell established Hydrogen Source as a commercial venture to ensure the implementation of the CPO technology as a means to provide fuel cells with hydrogen fuel. This technology will enable the conversion of both conventional fuels like gasoline or natural gas and bio-fuels like ethanol or biogas to clean hydrogen for fuel cell applications. Via this route the introduction of fuel cell cars can be facilitated, because the conventional transportation fuel infrastructure can be used. This could very well be the @rst step in the
1127
transition towards a (automotive) hydrogen economy. The next two steps required will be direct fuelling with hydrogen, when hydrogen distribution and storage have been developed, and the production of hydrogen from a renewable source, i.e. completion of the transition to a hydrogen based sustainable energy market. 4. Towards sustainable energy markets 4.1. Bio-fuels Shell is active on a commercial basis in solar photovoltaic manufacturing, biomass as fuel for power generation and wind projects. Shell researchers are also active in developing attractive options for conversion of biomass to bio-fuels. This is a typical example of research projects that are currently being carried out to support our sustainable development objectives. Electricity production from biomass tends to be non-competitive, because conventional fuels oHer relatively cheap solutions. Many routes have been explored to convert biomass into transportation fuels, e.g. gasi@cation followed by synthesis to methanol or diesel, fermentation to ethanol or biogas, etc. The current approach is to optimise the total value of crops by producing higher value products like food and @bre, and using “waste” (in fact biomass residues) to make other products such as bio-fuels, ethanol and electricity (see Fig. 3). In this way one would pro@t from cascading and create synergy rather than competition between the food and fuel industries for the same biomass feedstock. Research on bio-fuels has to take account of the needs of a number of traditional businesses if win–win options are to be developed. To compare biomass residue and crude oil in energy value, the annual world biomass residue (wood waste, straw, husks, pods, stalks) production equals half of the annual oil production. Bio-fuel components, blended with conventional fuels, would also form an attractive route for accelerated introduction of renewable
Towards a Sustainable Energy Supply: Biofuels Feedstocks specific characteristics Valuable Molecules
5 billion t/a biowaste equivalent to half of the oil production
Technologies New Developments Synergies
Products performance HSE; value - chemicals, solvents
$1000/t
- hydrogen
$1200/t
- transport fuels compon. $ 250/t - fuel oil - power to grid
$ 70/t $ 25/t
Key factors for successful development of biomass-to-biofuels chains: ·Target high value products (e.g. hydrogen, transportation fuel components) ·Make use of feedstock characteristics ·Develop new technologies (synergy between food and fuel industries)
Fig. 3. Towards a sustainable energy supply: bio-fuels.
1128
J.W. Gosselink / International Journal of Hydrogen Energy 27 (2002) 1125 – 1129
application distribution
harvesting
incident solar energy (also stored in wind, rain, and waves) wind wave hydropower power power
PV
heat space photocollection PV catalysis
electricity
biotechnology
radiation
biomass
?
gasification reforming
steam water electrolyses
water thermolyses molecular hydrogen at production site
pipeline
metal hydrides
molecular redox couples
carbon-based materials
?
molecular hydrogen applicable in end-device PEM fuel cell
combustion
?
power (electrical, mechanical)
Fig. 4. Sustainable hydrogen chain.
transportation fuels, bringing us step by step to a sustainable energy market. Targeting bio-fuels from biomass residues also sets challenges to the processes, rather making use of the molecules in the biomass residue (for instance oxygenates) than destroy them completely as, for example, by gasi@cation. Today, ethanol can be produced from a steadily widening range of feedstocks and if the key technologies continue to advance at su1cient pace, it could become a competitive component for blending into transportation fuels [6]. 4.2. Sustainable hydrogen Hydrogen from renewable sources might be considered as the ultimate clean and climate neutral energy system. A typical energy chain for sustainable hydrogen comprises the harvesting of sunlight into hydrogen as energy carrier, the storage and distribution of this energy carrier to the end-device where it is converted to power. Various options are envisaged for such a chain, see Fig. 4. A rollout of such a sustainable hydrogen chain in developed countries could go either gradually via a hydrogen economy based on fossil fuels or discontinuously in the case of inventions of disruptive technologies. For developing countries the situation may be diHerent. Introduction of such hydrogen chains for their fast growing primary energy demands might enable them to skip the stage of conventional, fossil fuel based, technologies=markets, and leapfrog directly to a sustainable economy, e.g. a sustainable hydrogen economy. A lot of research and development has to be carried out to make a sustainable economy happen, not only science and technical development, but also social aspects. A substantial corporate (Shell) eHort is being made to explore this social dimension of the triple bottom line (economy, ecology, social). In line
with this philosophy these aspects will also be addressed in the Dutch Hydrogen programme, a 6-year study on the development of a sustainable energy chain based on hydrogen [7]. An industrial consortium, in which Shell is participating, and NWO (Dutch science organisation) will lead this program. For the capturing of sunlight and the production of hydrogen various routes are possible. The most promising candidates to become important elements in the sustainable hydrogen chains are: (1) Water electrolysis, using renewably produced electricity and (2) biomass=biological processes. The electrolysis route is currently already achievable with ¿ 90% e1ciency. The required electricity can be produced from, e.g. wind power, wave power, hydropower, and photovoltaic. These electrolysis routes currently suHer from relatively high costs and ergo cost reduction obviously will be an important R& D target. A lot of research is being carried out to produce sustainable hydrogen via biomass=biological processes (BioHydrogen 2002 conference, The Netherlands, April 21–24), e.g. to improve overall e1ciency and to reduce cost, in order to make these routes economically feasible [8]. A wide variety of interesting routes are being reported, e.g. hydrogen production via biomass gasi@cation, via biogas steam reforming (biomass fermentation followed by methane conversion to hydrogen), via fermentation or enzymatic conversion of sugars, direct production by micro organisms (bacteria and algae), such as by algae via photosynthesis after a metabolic switch. Because fuel cells are the most logical end-devices, purifying the produced hydrogen is required, because they currently require extremely pure hydrogen (especially as regards hydrogen sulphide and ammonia). The best way to produce the hydrogen will have to be locally determined using the most optimal way
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to capture the sunlight, while keeping an eye on the overall source-to-sink e1ciency of the chain. In contrast to the readily available ancient sunlight stored in fossil fuels, the harvesting of incident sunlight will be discontinuous. Therefore, e1cient electricity and hydrogen storage technologies must be developed, not only for stationary but also for mobile applications. There is currently no ideal means of storing electricity to provide for high demand at times of low primary power supply. Various hydrogen-storage options can be envisaged and are being investigated, e.g. liquid hydrogen, compressed hydrogen, metal hydrides, chemical hydrides, and modi@ed carbonaceous materials. To reduce the cost and technological barriers for hydrogen storage, the processes should be optimised, e1ciency increased, reaction speeds optimised, and in almost all cases costs decreased. Therefore thorough understanding of the chemistry and physics of the interaction of hydrogen with other materials is required. The growing trend away from traditional centralised (and largely fossil-powered) electricity generation towards distributed generation is reshaping the size and function of electricity networks, particularly in emerging countries where no e1cient established grid is in place. The inclusion of renewables (e.g. hydrogen via electrolysis and biomass=biological processes), as an intermittent energy source which is inherently small scale, is oHering a sustainable element in support of this trend, and the future application of fuel cells and e1cient energy storage devices (in the form of hydrogen or electricity) will also contribute. Signi@cant attention will then need to be paid to buHering of the networks and eHective integration of a more diverse mixture of energy sources and carriers, particularly if these are dependent to varying extents on renewable sources. Novel methods of linking different components will be required, and developments in solid-state switchgear, power electronics and energy conversion devices will contribute to this. Fully integrated power solutions will play a signi@cant role in the future; for example, a small- to mid-scale unit which can produce heat, electricity and hydrogen, or a compact hydrogen storage device placed in a fuel-cell car
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but which can also be used to supply domestic electricity at times of peak demand. Such a paradigm shift, from remote generation to more localised production and storage of energy (as both hydrogen and electricity), will require careful attention with respect to social acceptance, particularly in developed economies, where the consumer—both residential and industrial—has long been separated—both physically and mentally—from any manufacturing impacts of his power supply. Acknowledgements The author thanks his colleagues Dr. A.M.S. Elliott, Dr. H.P.C.E. Kuipers, Dr. F.G.M. Niele, Dr. C.J. Schaverien and Drs. J.P. Haan for their contributions to this paper and critically reviewing the manuscript. References [1] Moody-Stuart M. In: Safe climate, sound business. A speech given at the World Economic Forum in Davos, 28 January 2000. [2] Moody-Stuart M. Shaping the future of energy industries— an energy company perspective. OHshore Northern Seas Conference, Stavanger, August 22, 2000. [3] Herzog H, Drake E, Adams E. CO2 capture, reuse, and storage technologies for mitigation global climate change. A White Paper, Final Report. DOE Order No. DE-AF22-96PC01257. [4] Shell Venster Januari=Februari 2002. p. 22–3 [in Dutch]. [5] Kramer GJ et al., The determining factor for catalyst selectivity in Shell’s catalytic partial oxidation process. Fuel Chem Div Preprints 2001; 46(2):659 – 60. [6] Groeneveld MJ. Ethanol: it’s possible role in CO2 sustainability. ISAF XIII, Stockholm, Sweden, 3– 6 July 2000. [7] NWO Programme Sustainable Hydrogen (an environmentally clean energy carrier). Outline of a research programme, 12 June 2001. [8] Pedroni PM. Biohydrogen production technologies: a general overview and photofermentations as a speci@c case. BioHydrogen 2002, Ede, The Netherlands, April 21–24, 2002, Book of Abstracts. p. 22.