Hydrogen and its competitors, 2004

Risø Energy Report 3Summary, conclusions and recommendations 52Summary, conclusions and recommendationsHANS LARSEN, ROBERT FEIDENHANS'L AND LEIF SØNDERBERG PETERSEN, RISØ NATIONAL LABORATORYInterest in the hydrogen economy and in fuel cells hasincreased dramatically in recent years. The main reasonis that a hydrogen economy may be an answer to the twomajor challenges facing the future global economy:climate change and the security of energy supplies.Both these challenges call for development of new,highly-efficient technologies that are either carbonneutralor low emitting technologies. The commercialintroduction of such technologies has huge potential tocreate economic growth and new high-tech jobs.The need for new and sustainable energy technologies isparticularly urgent in the transport sector, where energydemand keeps growing, especially in China and otherdeveloping countries. It will be a major challenge for thetransport sector to convert to carbon-neutral fuels, interms of both technology and infrastructure. Hydrogencould link the power system to the transport sector,increasing the flexibility and robustness of the totalenergy system. Hydrogen could also be used to storeenergy produced from renewable, intermittent energysources, and hence open the way for their large-scalepenetration into the total energy system.Unlike coal or oil, hydrogen is not a primary energysource. Instead, it is an energy carrier comparable to theelectricity grid or a district heating network, and as suchit needs to be converted from other sources of energy.Most hydrogen produced today is used in the chemicalindustry. The dominant method of production is steamreforming of natural gas, which is currently used to makemore than 90% of all hydrogen.Alternative production methods include gasification andreforming of other fuels, electrolysis, and biologicalmethods. Biogas can be reformed directly to yield hydrogen.Solid fuels such as coal and biomass can be gasified,followed by reforming of the resulting gas. Electrolysis isa 200-year-old method, and is presently, and for theforseeable future the most straightforward way to makehydrogen from water using electricity, though it is noteconomically competitive at the moment.Biological routes to hydrogen, including biotechnologyand “bio-inspired” methods, have excellent long-termpotential as sustainable energy sources, but basic sciencebreakthroughs are needed, however, to make suchmethods commercially viable.Renewable energy sources can be used to producemethane, methanol and other hydrocarbon fuels thatdeserve careful consideration as alternatives to “renewable”hydrogen.A serious challenge, and potentially a complete obstacle,to the hydrogen economy is the need for cost-effectiveways to store hydrogen. The low energy density ofhydrogen makes it difficult to store in a cost-effectiveway smaller amounts in cars and portable devices.Possible answers are to store hydrogen in solid form, asmetal hydrides, or as synthetic hydrocarbons, but ineach case breakthroughs in basic science will be essential.Although pressurised storage of gaseous hydrogen is awell-known technology used in large scale, new lightweightstorage vessels will be needed to make thehydrogen economy practical. Very large quantities ofhydrogen could be stored in underground cavernssimilar to those now used for natural gas.Existing fuel cells can convert hydrogen efficiently intoelectric power. Emerging fuel cell technologies can dothe same for other hydrogen-rich fuels, while generatinglittle pollution. Fuel cells are already close to marketintroduction in niche areas such as portable electronicdevices and small power units, which do not require alarge hydrogen infrastructure. Applications like thiscould pave the way to a future hydrogen economy basedon hydrogen-rich fuels.If large amounts of hydrogen are to be used across theworld, a comprehensive hydrogen infrastructure willhave to be developed. Hydrogen grids could become afourth backbone in the energy supply system, alongsidethe existing electricity and natural gas grids and districtheating systems. Because hydrogen can be interconvertedbetween electricity and fuel, however, hydrogengrids could also link the other energy backbones to anextent that is not possible today.Developing robust solutions for a hydrogen infrastructurein road transport is particularly urgent. Prototypehydrogen-based fuel cell vehicles are already in operation,and hydrogen vehicles could enter the market in15-20 years' time.Hydrogen as a fuel has a low environmental impact atthe point of use, with no emissions of greenhouse gasesor of most other pollutants. The amounts of hydrogenentering and leaving the atmosphere, and the routes bywhich this happens, are still very uncertain, but ourcurrent knowledge suggests that the widespread use ofhydrogen would bring little environmental risk.Hydrogen is no more hazardous than conventional fuels,but its safety-related properties are significantly differentfrom those of conventional fuels. Thus, detailed riskassessments are needed for every element in the hydrogensupply chain.International hydrogen research and development iscomprehensive. Japan is one of the most ambitiouscountries in its hydrogen programme. The USA has