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Debate Renewable energy

Hydrogen produced using energy from unpredictable renewable sources is claimed to be the pollution free fuel of the future - but there are massive storage and distribution challenges to be faced.

This week we ask: is hydrogen the key to making renewable energy acceptable - and vice versa?

Yes

Dr David Jollie, editor, Fuel Cell Today.

Over recent months, energy production has been a key topic for discussion, from the introduction of an infrastructure for developing nations to ensuring energy security for North America, and even limiting climate change due to greenhouse gas emissions.

Renewable energy often appears as a potential solution for all of these issues. Cleaner energy production and distributed generation from renewable power are an attractive proposition. However, no one can honestly say that the route for renewable technology into commercial territory will be smooth.

The main issue is the nature of the power provided. In contrast to central generation, such as coal or nuclear power, it is intermittent: water flow through hydroelectric schemes can be seasonal while wind-power can fluctuate by the minute. For this technology to succeed, energy storage therefore becomes important, in order to provide a reliable source of power.

Hydrogen is one of the most exciting means of storing this energy and has the potential to bring together current technology and renewables in a way that most other technologies cannot.

Because hydrogen is an energy carrier - or vector - it can come from a number of sources and be used in many different ways.

While nuclear power may be good for use on the electric grid, it is not realistic to expect huge numbers of battery electric cars to be charged from the mains and run with acceptable performance. However, a hydrogenfuelled car might be able to provide the fuel economy I need, using a fuel cell, and the necessary performance from a hydrogen internal combustion engine.

Cambridge's USHER project will use photovoltaics in the UK's gloomy East Anglia to provide hydrogen to power a city-centre bus, running with no harmful emissions. Other projects will see excess wind-power used to power public transport elsewhere in the UK.

Use of hydrogen to level peaks and troughs of generating power, allows smaller renewable systems to be used, reducing their cost. This levelling also means that power could be sold into the grid or to the end user when prices are attractive rather than when power is being generated.

Overall, the extra flexibility that integration of hydrogen with renewable generation can bring will prove attractive to the consumer and the producer, as well as the environment.

No

Frank Binns, Babtie Power Consultancy

Currently, most of the increase in renewable energy is expected to come from wind. So the question posed in this debate is really aimed at wind power where the predictability of generation is in the hands of the weather. The real questions are, does this level of wind generation pose a threat to security of supply because of its unpredictability? Is hydrogen the key to removing this unpredictability by using the electricity from wind farms, when they generate, to produce hydrogen for subsequent use in fuel cells, allowing electricity to be produced in a predictable way?

As long as the characteristics of all the fuel types within the generation mix are considered together then this level of wind generation can be accommodated without any special reliance on hydrogen technology. The fuel mix should of course include hydrogen as well as storage in the form of conventional pumped hydro and other emerging storage technologies.

It should also include nuclear, which the government's recent Energy Review identified as an option the UK should keep open.

Hydrogen fuel cells are being developed for use in transportation and distributed power generation. However, for fuel cells to be used widely the production of hydrogen as a fuel needs to be price competitive. Electrolysis of water to produce hydrogen offers emissions free hydrogen production but requires ample supplies of cheap electricity to make it commercially viable.

There is no doubt that hydrogen technology has a big role to play in the future. Its emergence, however, does not necessarily depend on renewable energy, but among other things, on the provision of reliable and cheap supplies of electricity.

The key to the success of renewable energy, including hydrogen technology, is the implementation of an energy strategy for the UK designed to deliver secure, reliable and cheap energy with low emissions. Hopefully such a strategy will be the outcome of the government's current deliberations.

The facts lHydrogen is a lightweight gas at normal pressures and temperatures.

It can be stored either as a liquid at temperatures below - 253infinityC or as a gas at pressures between 200 and 500 bar. In both forms it needs significantly more storage space than petroleum products, so a hydrogen-fuelled vehicle sacrifices either range or boot capacity compared to a conventional vehicle.

lThe EU has targeted 12% of energy supply to be from renewable sources by 2010. At present renewable energy costs are still uncompetitive with fossil fuel generation.

lHydrogen is produced by the electrolysis of water. To generate energy it can be burnt in an internal combustion engine or reacted with atmospheric oxygen in a fuel cell. Its lIn February the government published a document titled The Energy Review. It states 'the policy framework should address all three objectives of sustainable development - economic, environmental and social - as well as energy security.'

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