hydrogen
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Hydrogen has a crucial role to play in the race to diversify energy sources, maximise the benefits of renewables and reduce carbon emissions, argues Peter Hardy of the Institution of Gas Engineers & Managers (IGEM).

We all know that the coming years will bring more innovation in the gas and wider energy sector than ever seen before.

If governments are to meet binding carbon reduction targets while diversifying supplies to achieve energy security, technical developments and new technologies are essential.

IGEM – the voice of the UK and overseas gas industries since 1863 – believes widespread use of hydrogen as an energy carrier is one such development that must be embraced.

Hydrogen has been a chemical feedstock for decades, used by industry to produce fertilisers and for cracking hydrocarbons at petroleum refineries. Other significant applications include hydrogenation of unsaturated oils and fats. But molecular hydrogen (H2) occurs extremely rarely on Earth, so it must be produced through various processes that typically involve electrolysing water to yield hydrogen and oxygen.

In the 1970s, the term ‘hydrogen economy’ was coined by GE to describe the potential of hydrogen as an energy carrier to provide power, heat and automotive force wherever needed. At standard temperature and pressure, hydrogen is a colourless, tasteless, odourless, non-toxic, readily combustible gas with a high calorific value: properties which confer high suitability as a medium for transferring energy.

In recent years, governments and industry have invested significantly in developing mobile and stationary applications of hydrogen. Although not yet widely adopted, electric cars, buses, trains and boats powered by hydrogen and fuel cell (HFC) technology, as well as the required fuelling stations, are now a reality. Such vehicles produce ‘zero emissions at the tailpipe’, except for water.

The dwindling of conventional fossil fuels, combined with rising political concern over climate change and security of energy supply, has acted to revive interest in hydrogen and HFC technology, as well as in emerging renewable energy sources such as biofuels and biogas. One of IGEM’s roles has been to assess the technical challenges and opportunities associated with its environmental and energy security benefits.

Hydrogen as energy carrier

Molecular hydrogen is not a primary energy source like coal, oil or natural gas. Rather, it is a suitable medium for storing and transporting energy where it is needed. To produce hydrogen via the electrolysis of water requires energy. While fossil fuels have traditionally been burned to provide that energy, this is scarcely ideal for the transition to a low-carbon economy. And using nuclear fission, although it lowers the carbon footprint, has proved controversial.

A more environmentally sound means of producing hydrogen is to use renewable energy sources to drive electrolysis, which could become a significant industry in the years ahead. As well as helping to cut dependency on fossil fuels such as coal and oil, this approach offers additional opportunities to improve and maximise the impact of sources like wind and solar photovoltaics (PV).

Maximising renewables

However, one significant drawback of wind and solar is the intermittency and unpredictability of the weather conditions. Variation in the output of installations linked to electricity grids can be problematic since peaks and troughs often do not correspond with end user consumption. Because of the potential to destabilise grids, excess output is often siphoned off to avoid problems.

Germany is leading the field in avoiding such wastage, by using excess output for electrolysing water to produce hydrogen. In small quantities hydrogen can safely and legally be injected into gas networks, and the resultant hydrogen/methane blend burned in consumers’ existing appliances. Alternatively the hydrogen can be methanated to produce methane, the cleanest burning hydrocarbon, before injection into gas networks in much larger quantities.

E.ON recently started construction of a power-to-gas plant in Falkenhagen, northeast Germany, to convert waste output from a wind farm to energy utilised for H2 production. Such projects demonstrate that while not 100 per cent efficient (no energy conversion system can ever be), the intermittency of renewables can be successfully addressed. This is, of course, extremely good news for north European countries, which are blessed with relatively windy conditions.

A similar principle applies to RWE’s new power-to-gas plant in Ibbenbüren. But at RWE’s plant excess energy harnessed from wind or solar power will be used to split water into hydrogen and oxygen, before the hydrogen is injected into the gas grid.

While the energy derived from the rotation of wind turbine blades drives electrolysis of water, in the case of solar PV it is electromagnetic radiation from the sun that splits the molecule.

At Baden-Württemberg, the Centre for Solar Research (ZSW) has developed a research facility to harness solar power to produce methane, which can then be added to the gas grid without the regulatory issues that prevent large quantities of hydrogen being injected. The facility will come online by the end of 2013 and aims to produce up to 300 m3 of methane per day.

Utilising infrastructure

One of the key criticisms of hydrogen as an energy carrier is the seemingly huge investment required in infrastructure, to mass produce, transport and make available hydrogen for the end user. While it is true that government and industry collaborations are the only feasible means of rolling out hydrogen filling stations on a commercial scale, it is also the case that hybrid electric vehicles would put a huge strain on electricity grids if they were mass-adopted by consumers, particularly plug-in models.

Conversely, for countries such as Germany that are beginning or preparing to mix initially small quantities of hydrogen with natural gas before supplying the blends to customers’ appliances through gas transmission networks there are significant savings to be made on infrastructure. Gas networks supplying methane represent a hugely expensive investment, one which many countries cannot afford to fall into disuse in the future.

For countries that have previously pumped coal gas – also called town gas – through the networks, this need not be the case. Coal gas, produced by destructive distillation of coal, is a mixture containing about 50 per cent hydrogen along with methane, volatile hydrocarbons and usually carbon monoxide and carbon dioxide. For many gas networks, it is expected that only minimal work would be required to once more supply up to 50 per cent hydrogen mixed with natural gas – although in the UK changes to legislation, regulation and new standards would be required.

The wider picture

Current and forecasted global energy scenarios are extremely complicated. While investments in renewable energy sources have risen year-on-year to a record £165 billion ($263 billion) in 2011, unconventional resources like shale gas and coal bed methane have added decades to the world’s supply of fossil fuels, even with ever expanding levels of demand. While some countries have for the time being banned drilling for these resources, the US has experienced such a boom that it recently became a net exporter of gas.

To tackle concerns over carbon emissions, climate change and security of supply, it is therefore also imperative that advanced economies continue to invest in developing renewables and technologies like hydrogen and fuel cell technology. IGEM firmly believes that diversity of supply is essential, a message we are communicating to governments, regulators and industry through our programme of activities. Among such diversity we also know that clean-burning natural gas, as well as hydrogen, must figure for the foreseeable future.

Peter Hardy   Peter Hardy is technical services manager at IGEM, the leading chartered membership organisation for the UK and overseas gas industries. For more information, visit www.igem.org.uk