Ceramic fuel cells convert natural gas and renewable fuels like hydrogen into heat and power, and are particularly promising as a clean energy source because they increasingly address the need for higher efficiency energy production with relatively low greenhouse gas emissions.

While batteries store a limited amount of electrical energy, fuel cells instead consume fuel and are able to operate virtually continuously as long as the necessary flows of fuel and air are maintained.

Solid Oxide Fuel Cells (SOFC) are a prime example of a ceramic fuel cell, and have electrical efficiency ranging up to 70 per cent. They use most hydrocarbon-based fuels and can be used for all types of stationary power generation, from below 1 kilowatt (kW) to many megawatts (MW).

Since the production of electricity is a direct process, SOFCs do not produce large quantities of greenhouse gasses, nitrous oxides or sulphur oxides and only emit steam and possibly low levels of carbon dioxide – this does not occur if the fuel cell uses pure hydrogen. The production of heat makes SOFCs ideal for domestic combined heat and power applications, which not only produce heat for space heating and hot water, but also electricity which can be used around the house or fed back into the electricity grid. This process is considered to be more efficient than separate production of heat energy and electricity, with wastage through the generation, transmission and distribution process.

Integrating gas and other renewables

Australian company Ceramic Fuel Cells Limited (CFCL) has developed a SOFC system that can be connected into a regular natural gas network, making the fuel cell system more accessible since there is no need to convert hydrocarbon fuel sources into hydrogen gas.

CFCL Product & Marketing Manager Trent Rowe notes that the fuel cells integrate very well with other renewable energy sources. “Fuel cells require a fuel source to operate. The key here is what the fuel source is and where it comes from. Biofuels, such as ethanol and biogas, and hydrogen are future renewable fuels and CFCL’s fuel cells can utilise these fuel sources.”

The company’s fuel cells have been in development since 1998, as part of a project which aimed to develop a hybrid solar/fossil fuel system that could be scaled up and used in both distributed power systems and large centralised generation to supply industry, cities and communities with cleaner energy.

The fuel cells were originally designed to integrate with other renewable energy sources, including solar thermal power. Solar energy can reform gas such as methane to increase its energy content by approximately 20 to 30 per cent, with no increase in greenhouse emissions.

Solar energy has also been used by CFCL to develop chilling technology which is suitable for residential application, although development of more efficient cooling is still being refined.

Technical challenges

With the considerable flexibility of the SOFC system, it is not surprising that the biggest challenge in developing the fuel cells relates to the complexity of the materials science behind the technology.

“Finding the exact materials for the system to function, and function with increasing reliability is the technical challenge. Over the years CFCL has developed ceramics, metal alloys and a number of other materials that are critical for the operation of the fuel cell,” says Mr Rowe.

A prime example of the type of technical challenge has been ensuring that the materials do not bend or break when subjected to the high operating temperatures of ceramic fuel cells, up to 1,000ºC for SOFC systems.

CFCL had initially developed metal-ceramic stacks but was limited by the available metal alloys and subsequently developed fuel cell stacks made chiefly from ceramic materials. However, newer materials have since been developed, enabling the company to resume its development of metal-ceramic stacks that now are capable of producing double the power in a smaller package size.

Challenges in commercialisation

In many ways, the major challenge to commercialising SOFC systems is analogous to those faced by all emerging technologies. Broadly speaking, the company needs to address the concern of whether the technology is sufficiently advanced for commercialisation. Secondly, are the fuel cells able to be made in sufficient quantities and affordably enough to foster the market? Finally, is there sufficient demand?

“The key here is that customers want to see lifetime, but like many industries it is difficult to undertake accelerated testing. To wait for five years to ‘prove’ lifetime is not an option as the technology will have evolved within those five years,” Mr Rowe says.

CFCL is well positioned to address commercialisation and affordability issues. As both a developer and manufacturer it can direct research effort over cell technology, stack lifetime and system performance on the one hand and, on the other, manufacturing tolerances and the infrastructure requirements for scaling up.

The company has reported that advances in power density have enabled it to increase the output from each of its fuel cell stacks to 2 kW of electricity, reducing the unit’s cost per kW and saving up to three tonnes of carbon dioxide per year. A 2 kW unit provides ample power for the average household’s annual baseload requirements, as well as additional power for export to the grid.

“While the fuel cells must work they must also be manufactured at a competitive cost – therefore all of the fuel cell components are being optimised for commercial manufacturing at the start,” adds Mr Rowe.

Field trials are currently being conducted in New Zealand, Melbourne, Australia, and Germany, with a focus on testing SOFCs with utilities and appliance manufacturers rather than more widespread trials in houses.

Currently in the product development stage, only sophisticated ‘pre-commercial’ and prototype units are being produced for testing and development, which are currently more expensive than traditional mass-produced generators/boilers. However, the company will soon invest $20 million for the construction of a manufacturing plant in Heinsberg, Germany for the commercial production of its fuel systems to be supplied throughout Europe. Volume production is expected to commence from June 2009.

To deal with the final challenge of commercialising these technologies for the mass market, Mr Rowe highlights CFCL’s collaboration with European utilities, which will ultimately deploy the units.

Mr Rowe says that a disruptive technology like fuel cells requires coordination from every part of the business, from retail, through to generation management and financing. Even if the product were available today, there would still be a delay as regulators and utilities considered its implementation, control and packaging to consumers.

“As many utilities and network operators know, managing the network can be a challenging task at times,” he says. “If we look into the future, network operators need to manage the variable generation technologies such as wind, solar, wave power. For example, in a localised area if 100,000 uncontrolled 1 kW fuel cells were installed in people’s houses, that would add 100 MW that the utility would need to consider. Then what about connection standards? Feed in tariffs? Government rebates? So from a market readiness perspective, there any many facets to consider.”

The market for ceramic fuel cells

Despite the complexity of the system, after successful field trials in Germany the company is deploying its latest generation units in France, The Netherlands, the UK and Japan this year. Mr Rowe says that Germany and Japan are considered one of the most advanced markets for fuel cells, with considerable government funding for demonstration programs.

“If we look at deployment in Australia we are faced with a unique problem where the cost of energy is very low. As an example, the US Department of Energy listed the price of electricity in Australia 2004 as $US0.09 per kWh, whereas the cost in Germany is roughly double and Denmark - more than three times as expensive compared to Australia,” Mr Rowe notes.

Despite the impact of low gas prices on immediate commercialisation within Australia, the Australian government has supported the company with funding and export grants to technically develop the fuel cells. The promotion of higher energy efficiency appliances may also eventually shift the focus onto SOFCs in Australia.

The direct nature of electricity production which translates into up to 70 per cent efficiency, rather than up to 35 per cent with generated by alternative methods, and its ability to use rather than waste heat energy give it a bright future among its clean energy counterparts.

As Mr Rowe concludes “Fuel cells are not a silver bullet technology that will solve the world’s energy problems; they form part of a complete solution integrating with incumbent and future generation technologies.”