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Large scale fuel cells near commercial application

Large scale fuel cells near commercial application

"Fuel cells are the most promising new form of energy generation – and always will be!" That is the unkind jibe sometimes levelled at this technology, originally invented back in 1839 by Sir William Grove. However, developments in fuel cell technology mean the waiting may be over sooner than many might think.

There is a new urgency for fuel cell development, driven by such issues as the need for clean energy generation, pressures from environmental targets and the cost and availability issues surrounding platinum – a common catalyst in modern fuel cells.

Compared with combustion engines, fuel cells are cleaner, quieter and more efficient. This, and their practical power range from 1kW to more than 200kW for the most common proton exchange membrane (PEM) types, makes them well suited to applications in automotive, domestic combined heat and power, remote power and small auxiliary power generation.

While some inroads have been made in such areas as backup power for telecoms and power modules for materials handling equipment, the need for reduced cost and improved reliability means that higher profile applications, such as fuel cell powered cars, have yet to fulfil their potential.

ACAL Energy revealed in 2008 that it had been developing FlowCath, a fuel cell system based on the use of a low cost water based catalyst solution which replaces platinum at the cathode. This approach enables 80% of the total platinum content to be eliminated from the system. Partly as a consequence of removing the platinum, cost can be reduced by at least 25% compared with conventional PEM fuel cell systems.

Through system simplicity and the removal of the need for expensive hydration equipment and separate cooling, significant balance of plant cost could also be avoided. Looking further ahead, by combining FlowCath with a non Pt anode, a Pt free fuel cell could be created. The lower cost and simpler systems make them more appropriate for mass market opportunities.

The FlowCath system separates the oxygen reduction step from the electrochemical reaction. The soluble catalyst and a mediator are dissolved in an aqueous solution, called the catholyte solution. In a regenerator external to the cell, the catalyst reacts with oxygen from the air to oxidise a mediator. The mediator is transported in the catholyte solution to the electrode, where it is reduced (see fig 1). As well as enabling the use of cheaper catalyst materials, the liquid system provides inherent membrane humidification and thermal management: key system challenges for conventional PEM technology. Other benefits include good resistance to air contaminants, such as carbon monoxide and carbon dioxide, and an ability to cope with higher levels of water in the supplied hydrogen, meaning lower grade hydrogen could be used.

Progress with the FlowCath technology has been strong. In 2008, a 50W fully integrated 10 cell system was operated for the first time and produced higher power levels than expected.

Although FlowCath is radically different from conventional systems, it has proved straightforward to scale. By the end of 2009, a peak power level of 1.5kW was achieved from a hydrogen fuelled laboratory scale fuel cell system.

In 2010, ACAL Energy began leading a £1.9million collaborative project –part funded by the Technology Strategy Board – to build its first installed system in a practical application. This important milestone represented the first 'real world' application with partner Solvay Interox. SolviCore (a 50:50 joint venture between Umicore and Solvay) and Johnson Matthey Fuel Cells focused on the development of the membrane electrode assemblies, whilst UPS Systems was responsible for the commercial integration of the project and the monitoring systems.

Building this full scale, unattended prototype system was an important achievement. The 3kW unit was designed to operate through large changes in ambient temperature and humidity and with erratic duty cycles and fluctuating loads. The rapid start up, rapid response characteristic would be important for its role in providing power to a remote environmental monitoring system located at Solvay's Warrington facility.

Confidence in the robustness and reliability has always been high, as the FlowCath system avoids much of the complex engineering required in conventional fuel cells. It achieves this principally through simplification and elimination of many common failure mechanisms found in standard PEM fuel cells. The technology is expected to reduce the balance of plant costs by eliminating the need for hydration, separate cooling and other expensive mechanical subsystems.
Earlier in 2011, ACAL Energy won The Carbon Trust's Polymer Fuel Cell Challenge and, with it, a £1m investment. At the time, the Trust said 'ACAL Energy's breakthrough technology could make hydrogen fuel cell cars a mass market reality'. Hydrogen powered fuel cells can power electric cars with zero local emissions, whilst offering the range currently expected from a traditional combustion engine. ACAL Energy's developments could make fuel cell powered cars the lowest carbon vehicles around.

A critical factor in adoption is the proven durability of any new energy technology. ACAL Energy's catalysts have been in regular use for more three years in multiple test cells and systems and no instance of catalyst deterioration has been seen after a battery of single cell, stack and system testing programmes. In one set of tests, a full scale stack was subjected to extreme load and rapid thermal cycling from zero to 1A/cm^2 load cycles and from 20 to 80°C. No measurable change in performance was seen in more than 400 load cycles and 100 thermal cycles. In total, close to 2000 hours of cumulative testing have been clocked up.

These results demonstrate the practical benefit of inherently removing many of the root causes behind conventional PEM failure in use. For instance, one aspect of poor durability with the platinum used in conventional designs is that oxidation reaction by products, such as peroxides are formed, which over time lead to carbon corrosion. This, in turn, leads to a gradual loss of performance. These by products do not occur in FlowCath systems and neither does the 'flowing' liquid catalyst become deactivated, another limitation of conventional platinum systems. These features enable FlowCath based systems to be more robust and reliable in practical application.

In January 2012, a new Government backed initiative called UKH2Mobility was announced. This will evaluate the potential for hydrogen as a fuel for ultra low carbon vehicles in the UK and develop an action plan for an anticipated roll out to consumers from 2014 onwards. The initiative brings together Government and industrial participants from the utility, gas, infrastructure and global car manufacturing sectors to identify what is required to make the UK a leading global player in hydrogen fuel cell car and truck manufacturing.

ACAL Energy is confident it has the potential to assist the cost down strategies of vehicle OEMs looking to deploy fuel cells. Reducing the cost of achieving durability is essential to enabling vehicle manufacturers to accelerate progress and to supplying affordable fuel cell vehicles in mass market applications.

Amanda Lyne

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What you think about this article:

The most interesting fuel cell has been invented in Vietnam by an American engineer. It runs on water - either fresh or salt. No expensive ingredients are involved.

A 2,000 watt home generator is under development and will retail for $1,600.

See Moving Beyond Oil and Cheap Green on the Aesop Institute website for available details.

Posted by: Mark Goldes, 08/05/2012

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