The hydrogen economy blasts off

Physics World, July 2002

As fuel-cell buses take to the streets in Iceland, the idea of an economy based on hydrogen rather than fossil fuels is being taken more seriously, as Tim Chapman discovers

Iceland might seem an unlikely place to lead a technological revolution that could radically change the structure of the global economy. But as it takes its first steps to becoming the world's first hydrogen society, Iceland is aiming to prove that the 21st century can be powered without the environmental and political pitfalls of fossil fuels.

With no fossil fuel reserves, Iceland has long exploited its other geological assets to develop alternative energy sources. It meets virtually all its electricity and heating requirements from hydroelectric power and geothermal water reserves. But the sparsely-populated nation still relies on $150m/a worth of imported fuels for transport, including the demands of the fishing fleet which provides 70% of national income.

The Icelandic government is now backing an ambitious programme to remove all fossil fuel requirements from Icelandic society within a generation. The key is using hydrogen or hydrogen-rich compounds, produced using hydroelectric power, in vehicles powered by fuel cells. The first hydrogen buses will travel the streets of Reykjavik early next year, filling up with hydrogen-rich methanol at a new filling station built by Shell, one of the major corporate backers of the project alongside Norsk Hydro and DaimlerChrysler.

Over the next few years, the capital's entire 80-bus fleet will be replaced with buses powered by proton exchange membrane (PEM) fuel cells, accompanied by the introduction of PEM fuel cell cars for private transportation. A demonstration project for a fuel cell powered ocean vessel is planned for 2006, with the intention of replacing the entire national fishing fleet beginning in 2015.

Dr Bragi Arnason, professor of chemistry at the University of Iceland and an advocate of hydrogen power since the 1970s, says the transition to a hydrogen economy could be complete by 2030-2040.

Production and storage
The production of hydrogen is well established in Iceland, with 2,000t/a produced by electrolysis mainly for use in fertilisers. This capacity would have to be increased almost 30-fold to produce enough hydrogen to meet the expected demand.

Electrolysis is an energy-intensive process. According to Arnason, hydrogen produced this way will be up to three times as expensive by energy content as imported gasoline. Conveniently, PEM fuel cells are up to three times as efficient as internal combustion engines, so hydrogen fuel is competitively priced. And if hydroelectric electricity is used for production, greenhouse gas emissions are minimised.

The car industry also judges methanol the best medium for hydrogen - it has a relatively high proportion of hydrogen by mass, and as a liquid is easier to handle than methane. Pure molecular hydrogen would be the most energy efficient fuel, but is extremely awkward to carry in a car in its gaseous state.

Liquifying and compressing hydrogen gas uses 20-40% of its energy content, and pressurised storage tanks are many times the weight of their hydrogen content. Metal hydrides can store hydrogen at close to atmospheric pressure, but are too heavy for many uses. Other possible storage mediums are in development - graphite nanofibres, for instance, can store up to 75% hydrogen by mass, but may be impractical because they preferentially absorb water vapour.

American power
The hydrogen economy doesn't just involve fuel for transport, however. Iceland is fortunate that it can meet its national electricity requirements from fully renewable sources, but most countries are dependent on fossil fuels to produce electricity to homes and businesses.

Spurred largely by the desire to reduce its dependence on oil imports from politically sensitive parts of the world, the world's biggest and most energy-hungry economy has also embarked on an ambitious programme to convert to hydrogen.

In November 2001, the US Department of Energy led a meeting of industry, academia and government to discuss the potential role of hydrogen systems in America's energy future. The resulting vision document set out a wide-reaching vision of hydrogen as the nation's premier energy carrier. The DoE aims to realise the "meaningful introduction" of fuel cells for energy generation by 2005, with 0.04 quads of conventional energy replaced with hydrogen by 2010 (a quad is one trillion BTUs - US energy use is approximately 100 quads annually). By 2030, the DoE plans to replace tens of quads per year with hydrogen power. Much of the hydrogen will be derived from steam reforming of domestic fossil fuel reserves, with the pyrolysis of biomass and electrolysis of water playing an increasing role as the programme develops.

A major part of the DoE proposals is the use of hydrogen fuel cells in distributed generation, moving away from massive centralised power stations to much more localised generation. Many office and industrial buildings around the world already generate on-site heat and power from fuel cells which generate a hydrogen-rich fuel from natural gas. The cost of on-site fuel cells is now approaching parity with buying energy from existing powerplants, but prices should fall dramatically once there is sufficient demand to exploit manufacturing economies of scale.

Promoting adoption
The first stages of the transition to a hydrogen economy are something of a chicken-and-egg situation, with consumer demand unlikely to rise until the infrastructure is in place. The DoE proposes that national and state government services should be early adopters of hydrogen technology to help stimulate the market.

Some advocates of the hydrogen economy believe that market forces will be enough to drive the transition. Research by the Rocky Mountain Institute, the environmental thinktank in Colorado founded by experimental physicist Amory Lovins, shows that the transition can be profitable at every step. To kickstart the process, Lovins proposes leasing fuel cell cars to people who work in and around the buildings where fuel cells have been installed. The cars can fill up with hydrogen while parked during the day, and can also use their fuel cells to generate electricity to sell to the grid. Once there's a critical mass of fuel cell cars on the road, filling stations will install their own reformers and hydrogen pumps, promoting further infrastructure development. Eventually, most homes will have a fuel cell in the cellar, Lovins believes.

Hydrogen can also help solve one of the obstacles to the wider adoption of renewable energy sources such as wind and solar power. If such systems can only provide power when the wind is blowing or the sun is shining, they will play only a small part in meeting national energy needs. But if that power is used in electrolysis, hydrogen acts as an effective storage medium for renewable energy.