Hydrogen myths and renewables reality

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Much is being made of the vision of a "hydrogen economy" as the panacea for sustainable energy use. But hydrogen is only as sustainable as the energy technology used to produce it. That makes it dependent on renewable energy. Yet according to government blueprints on both sides of the Atlantic, it is the future growth of renewables that is dependent on hydrogen -- a deviation from the truth with dangerous consequences for the wind industry

Two serious fallacies are being propounded for why massive investment in hydrogen as the key element of a low carbon energy system will greatly benefit wind power. First, that if transport runs on hydrogen it automatically opens up a vast new market for wind in the production of the fuel in a carbon-free manner. Second, that in electricity systems hydrogen can be used as a buffer store for wind power to balance supply and demand when the wind stops blowing, or blows too hard. Indeed, for these reasons it is even being presumed in energy strategy documents that realisation of the full potential of wind energy is entirely dependent on development of the "hydrogen economy."

Believe that and the announcement by President George Bush of a $1.7 billion program to make the hydrogen car a national goal within the next five years is good news for wind power. So too is development of the European Commission's hydrogen energy and fuel cells strategy. But far from boosting the vision of a low carbon energy future, Bush and the Commission are delivering body blows to the entire concept of sustainable power supply. In their scenarios for the next half century, the source of most of the hydrogen is nuclear and fossil fuels, not renewable energy.

Just as with electricity, another energy carrier, the manner in which hydrogen is produced and used decides whether it will add to or prevent carbon emissions. A hydrogen economy based on nuclear and fossil fuels can only meet the environmental vision mapped out by Bush and the Commission if it is sustainable. That requires a solution for nuclear waste storage and the discovery of methods for the capture and retention of carbon emissions from fossil fuel burn -- an infant technology referred to as carbon sequestration.

Faced with technological challenges for nuclear and fossil fuels that could take decades to solve, if they are solvable at all, at first sight use of renewables to produce hydrogen is the only realistic option for meeting environmental goals of a "hydrogen economy" for at least the next 20 years. Yet siphoning off renewables electricity to produce hydrogen for transport will not help the environment. It will result in less carbon emission reduction than using the electricity directly. In other words, wind power has greater environmental value when it replaces generation from fossil fuels than when it is used to create hydrogen to replace fuels used in transport. So the environmental driver for opening up a market for wind power to produce hydrogen is non existent until such time all electricity is generated by renewables.

The argument for using hydrogen as buffer-storage in electricity systems is also flawed. On the sophisticated electricity networks serving industrialised countries today there is no need to provide dedicated storage for wind power. It is a fact being proved in practice every day in areas of the world with significant levels of wind power penetration, like northern Germany, Denmark and California. Even if dedicated storage were to become necessary for securing electricity supplies on systems with high proportions of wind power, hydrogen storage is not likely to be a viable solution. There are better ways of balancing supply and demand while meeting sustainability criteria, particularly economic criteria.

Transport fuel truths

The attraction of using hydrogen for transport is that it eliminates all harmful exhaust emissions at the point of use. Apart from carbon dioxide, these include carbon monoxide, particulates and acid-producing gases. But the production of the hydrogen, whether from renewables or fossil fuels, simply shifts the emissions eliminated from transport to somewhere else (though if it is derived directly from reforming of natural gas there is probably a net air quality benefit compared with transport fuels as few other pollutants result aside from carbon dioxide). Renewables derived hydrogen also only eliminates emissions at the point of use. When there is no excess of renewables generation on the grid, it means fossil fuels are being burned somewhere (or nuclear exploited) to replace the electricity being siphoned off for electrolysis to make the hydrogen.

Greater emission reduction rewards come from generation of electricity for direct consumption than for hydrogen production. If wind displaces gas-fired generation, it saves about 370 grams of CO2 per kWh; it saves over twice that if it displaces coal. On the other hand, if wind-generated electricity is used for transport, the savings are only around 225 grams/kWh, as a new British report, Fuelling Road Transport, demonstrates. The report is from the Energy Saving Trust, the Institute for European Environmental Policy, and the National Society for Clean Air and Environmental Protection.

The economics of a renewables-fed hydrogen cycle, with hydrogen produced by electrolysis (passing an electrical current through water) are fuzzy, though clear enough to be not at all encouraging. Hydrogen from wind energy costs about twice as much as petrol (gasoline), before tax. With a typical wind energy price of $0.045/kWh, and presuming 90% efficiency for electrolysis, the price of a unit of hydrogen energy is $0.05/kWh. The fuzzy bits are the costs that must be added for the electrolyser, the infrastructure for handling and storing the gas, plus losses -- remembering that hydrogen is the lightest of all gases. Both the US Department of Energy and London's Imperial College in the UK believe the delivered cost of hydrogen at the pump would be around $0.08/kWh. The delivered cost of petrol (gasoline), excluding duties, is about $0.02/kWh, or a quarter the cost of hydrogen fuel.

It is argued that hydrogen fuel cells are expected to be twice as efficient as petrol engines, reducing the price gap between the two fuels to about 50%, though this has yet to be proved. The costs of hydrogen fuel at the pump will depend on duties and taxes. As for total motoring costs, the price of fuel cells is currently about ten times that of petrol engines, so there is a pretty hefty gap to close before hydrogen transport becomes economically viable, let alone environmentally sensible.

Even if the poor economics of hydrogen were overlooked, requiring the electricity system to shoulder some of the energy requirements of transport makes massive demands for construction of more generation. If that capacity (whatever the technology) is specifically dedicated to hydrogen production, the costs of the system rise. As soon as specific generation is tied to specific demands, the indisputable economic, technical and environmental advantages of an integrated electricity system disappear. In a modern electricity system, charging a storage device -- or a hydrogen electrolysis plant -- with electricity when it is cheap, from whatever source, or a mix of sources, will nearly always be cheaper than setting up dedicated links. And an efficient system means fewer total emissions, not least because money that would otherwise have been wasted can be used to continue the shift to renewable energy generation and thus more carbon reduction for the same investment.

storage fiction

A perceived advantage of a hydrogen economy is that it enables the intermittent renewables -- particularly wind -- to have access to what is effectively a buffer store. In theory that store can absorb surplus electricity when demand is low and wind generation high and feed electricity back into the system when demand is high and wind generation low. In practice it is not that simple. The production of hydrogen by electrolysis is fairly straightforward, but to get electricity from hydrogen back into the network needs a whole new set of hardware -- and storage facilities too. It all has a price. Meantime, power systems already have ways of balancing supply and demand. Specific "load levelling" for wind is not needed in integrated electricity systems. This point is now being recognised by enlightened power market regulators, mainly in America, but also in Europe.

The implications for electricity networks of operating with increasing amounts of intermittent renewables amount to fine tuning rather than radical restructuring (Windpower Monthly, July 2001). Back-up for wind is not needed to cover for all the wind on a network at any given instant; it is only needed to cope with the extra uncertainty associated with wind. That extra uncertainty, in MW terms, typically amounts to around 3% of the wind capacity on a system with 10% wind energy. Most networks have storage of some kind to cope with everyday fluctuations in supply and demand and any extra fluctuations associated with wind are absorbed in the whole. More storage technologies are under development.

Today, the most common way of coping with intermittent renewables is to provide additional spinning reserve. This adds around $3.5/MWh (under 10%) to the cost of the wind energy if wind is supplying 10% of the energy on a network. With 20% wind, the additional cost is relatively less at just over $4/MWh. Using spinning reserve in this way also has an environmental advantage over diverting wind power to production of hydrogen: it pushes up emissions only very slightly. With 20% wind power on a network, the spinning reserve needed to cover the extra uncertainty reduces wind's emission savings by no more than about 1%, assuming the reserve is provided by the thermal plant wind is otherwise displacing. Diverting wind energy into producing hydrogen, on the other hand, results in the use of unsustainable fossil fuel or nuclear generation to replace the electricity no longer being fed into the grid.

If the hydrogen economy should take off due to the demands of transport for emissions free energy at the point of consumption, the costs of hydrogen storage for electricity will be spread over many uses and not just added to the price of wind. Even so, it seems unlikely that this will enable cheaper balancing costs to be realised than those already inherent in the network because of the efficiency losses associated with electrolysis and fuel cells. The overall efficiency of the fuel cell storage loop is less than 50%, even if optimistic efficiency values for electrolysis and fuel cells are used. This means that the electricity comes back from storage costing twice as much as when it left, to which must be added a contribution to the capital costs of the storage plant.

Fuel cell fallacies

The prospect of individual domestic-sized fuel cells for electricity generation is capturing the hearts and minds of environmentalists and politicians. But there is no escaping the fundamental difficulty that the hydrogen fuel cell route to electricity generation is an indirect one. The hydrogen has to be produced first. Only if the production is derived through electricity generated from renewable sources of energy is there an environmental benefit. But that benefit is far greater if the electricity is used directly rather than through a tortuous conversion route to hydrogen and back to electricity via a fuel cell.

There is no economic benefit either. Just as hydrogen for transport fuel is twice as expensive as burning petroleum products, so is electricity generated from hydrogen in a domestic fuel cell compared with mains electricity. Although hydrogen prices may fall, the greatest potential for price reduction is most likely linked to the falling cost of wind energy. For hydrogen to get significantly cheaper, it thus needs to be produced from wind, not fossil fuels -- presuming that a revival of cheap nuclear is not a politically live option. Without no solution for permanent disposal of its waste, nuclear is not a sustainable energy.

The realities

It is not a foregone conclusion that investment in a distribution and storage system for hydrogen will bring environmental benefits. Development of hydrogen as a second energy carrier to electricity will only reduce emissions if the hydrogen is based on renewable energy (today that is mainly wind power). Only if there is excess wind power generation -- a situation not likely before 2050 at the earliest according to the EU and American blueprints -- will there be an environmental driver for producing hydrogen for transport. Until that point, there are far greater environmental gains to be had from using renewable energy to displace fossil fuel generation.

There appear to be no environmental benefits to generating electricity on site from hydrogen-fed fuel cells. Adopting that route would drive up emissions unless the electricity used to produce the hydrogen came entirely from renewable energy or nuclear. Truly massive investment is required in development of wind power for the renewables vision to be realised. In Britain alone, 65,000 MW of wind generation would be needed to meet demands for zero-carbon transport, a logistical undertaking that makes reinforcement of the grid for offshore wind power mere child's play in contrast. In France, it would take 60, 1500 MW nuclear stations, according to the International Energy Agency.

Whether the ultimate hydrogen vision could ever be economically sustainable is highly uncertain. No solutions have yet been found for safe storage and transmission of a gas that is very light, making it prone to leakage, and potentially explosive. The transport and storage infrastructure needed for a hydrogen energy system would take many decades to build. The political vision being put forward by President Bush and the European Commission is that nuclear and fossil fuels would power this vast undertaking until such time as renewables could take over to make an unsustainable system sustainable. The Catch 22 is that such forced development of an infrastructure for a hydrogen economy will have long since squeezed-out renewables, with the result that emissions will have risen far faster than if transport had continued to run on fossil fuel. Renewable energy, not hydrogen, is the essential bedrock of an energy system which is economic, secure and above all environmentally sustainable.

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