18 March 2010

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Fuel cell cars – a guide

Fuel cell cars are widely considered the future of driving. The USA has plugged more than one billion dollars into fuel cell research and development, while the European Union approved a €940million initiative towards developing fuel cells and hydrogen technology for cars in May 2008. With such heavy financial backing for fuel cell cars it’s clear they are well supported – but just what are they and how do they work? This guide to fuel cell cars will explain.

Quick links:

What are fuel cell cars and how do they work?
What different types of fuel cell are there?
What are the advantages and disadvantages of fuel cell cars?
What is it like to own a fuel cell car? How much do fuel cell cars cost?
What fuel cell cars are available?
Where can you find a fuel cell car?

What are fuel cell cars and how do they work?

In many respects, a fuel cell car is similar to a battery-electric car in that there is no need for an internal combustion engine. Instead the fuel cells work as electro-chemical devices to convert the energy from chemical form into electrical energy, water and heat.

Fuel cells work in much the same way as a battery except there is no need to recharge – it will work as long as fuel is supplied – in most vehicular cases, this fuel is hydrogen.

Hydrogen fuel is fed in through the anode of the fuel cell, while oxygen enters through the cathode. This is where it gets technical – the hydrogen atom splits into a proton and electron with the proton passing through the electrolyte and the electrons creating a separate current, which is then united with the hydrogen and oxygen in a molecule of water. As the fuel cell relies on a chemistry process rather than combustion, its emissions are much lower.

What different types of fuel cell are there?

There are numerous different types of fuel cells – these include:

Alkaline fuel cells (AFC) – Often used on NASA space missions.
Direct Methanol fuel cells (DMFC) – Used to power mobile phones and laptops.
Microbial fuel cells (MFC) – Suitable for small applications such as medical devices.
Molton Carbonate fuel cells – Primarily targeted for electric utility applications.
Phosphoric Acid fuel cells (PAFC) – Commercially available and used in hospitals, utility plants, landfills and more; they generate electricity at more than 40% efficiency.
Proton Exchange Membrane fuel cells (PEMFC) – Considered as candidates for light duty vehicles and as a replacement for rechargeable batteries.
Protonic Ceramic fuel cells (PCFC) – Include a solid electrolyte so the membrane cannot dry out or leak.
Regenerative fuel cells – A closed loop of power generation that separates water into hydrogen and oxygen.
Solid Oxide fuel cells (SOFC) – Can be used in vehicles to power electronics.
Zinc Air fuel cells (ZAFC) – Has a high specific energy which gives it an advantage over other battery fuel cells.

Generally, the fuel cell thought to have the most advantages for fuel cell cars is the PEMFC. This is because it can operate at low temperatures, reducing start-up times, and as the cells use solid polymer materials the safety concerns of using liquid acid or alkalis are eliminated.

Hydrogen is the most commonly used fuel in fuel cells – because of the ease with which the element can form ions.

What are the advantages and disadvantages of fuel cell cars?

Fuel cell cars that operate on hydrogen produce zero emissions in the conventional sense as the only by-products are water and heat. The reaction in the fuel cells is highly efficient to the point that even if the hydrogen used was derived from fossil fuels, the hydrogen fuel cells would still cut carbon dioxide by more than half.

Energy efficiency is the number one advantage and if this is coupled with regenerative braking, emissions can be cut by a further 20%. If renewable energy is used to create the hydrogen, then harmful emissions are basically zero. Regulated emissions from UK hydrogen fuel cell cars (which use hydrogen formed from natural gas) are said to be significantly lower than petrol cars with nitrogen oxide emissions cut by 70%.

Hydrogen fuel cells also supply great flexibility. If a fuel reformer is included in the vehicle, it can generate fuel from diverse sources including fossil fuels, alcohol fuels, hydrogen compounds (such as ammonia or borohydride) or from biomass. Hydrogen can also be formed from electricity, whether from nuclear or renewable sources.

The problem facing fuel cell cars is that due to hydrogen’s low density there is a challenge to the design of on-board hydrogen storage systems – to store the same amount of energy as in a petrol tank would require a tank with approximately 800 times the volume.

However, solutions are being devised in the form of compression, cryogenic systems and metal hydrides which release the gas heat and reduce pressure.

Another approach is to reform the hydrogen-rich fuel on board the car – methanol is particularly popular for this process as it can be reformed at 260°C compared to 600-900°C for ethanol, natural gas, petrol and propane.

What is it like to own a fuel cell car? How much do fuel cell cars cost?

Refuelling a fuel cell car is dependent on the type of fuel used – in the case of methanol and petrol they are liquids so refuelling would the same as with a conventional car. If hydrogen becomes the norm however, hydrogen gas refuelling systems would need to be developed and would require a dispenser that is locked into place with the amount of hydrogen pre-selected.

There are only around 300 hydrogen refuelling systems worldwide, including one in Hornchuch, London – for a full list visit h2stations.org. As more hydrogen fuel cell cars are developed they should become more frequent.

With fuel cell vehicles, it’s difficult to estimate their costs but we can expect initial ownership expenses to be high – with purchase prices probably 80-100% higher than conventional cars. This price should fall as more come on to the market.

Once you own the car however, running costs should be lower. They should appear in the lowest tax band, be free from congestion charges, have lower fuel costs and be easier to repair due to the lower number of parts in the fuel cell engine.

What fuel cell cars are available?

Many companies are looking into fuel cell cars – here is a quick rundown:

BMW – The BMW Hydrogen 7 and the BMW H2R both use liquid hydrogen.
Daimler AG – The F-Cell is modelled on the Mercedes A-Class.
Fiat – The Panda hydrogen utilises a hydrogen fuel cell.
Ford – There is a hydrogen version of the Ford Focus (the Focus FCV).
General Motors – Multiple models including the HydroGen 3 and the Hy-wire.
Honda – Currently testing numerous fuel cells including the Honda FCX which is available from mid-2008.
Hyundai – Tucson FCEV utilises UTC Power fuel cell technology. Hyundai is also developing a fuel cell version of the ix35.
Lotus-in collaboration Intelligent Energy are developing hydrogen powered black taxi cabs.
Mazda – The RX-8 was the first hydrogen car leased to customers in 2006. The company has since created the Mazda Premacy Hydrogen RE.
Mercedes-Benz-is developing a fuel cell and hybrid model called the F800
Nissan – The X-Trail FCV is based on UTC Power technology.
Morgan – The LIFEcar debuted at the 2008 Sexy Green Car Show.
Peugeot-has developed a hyrdrogen fuel cell range extender.
Revolve-has been adapting Ford Transits to run on fuel cell technology
Riversimple-has created an open-source car that uses fuel cell technology
Smith Electric Vehicles: are trialing commercial vehicles on fuel cell technology
Toyota – Hydrogen versions of the Prius have been released and the Toyota Highlander FCHV is under testing.
Volkswagen – The company is reported as having several fuel cell models under development.

Where can you find a fuel cell car?

Fuel cell cars are not widely available. If you are interested in this technology you should contact the manufacturer directly to make enquiries. Otherwise, check back at TheGreenCarWebsite.co.uk as more fuel cell cars emerge on to the market.

Author: Paul Lucas, February 12, 2010

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