Fuels for the future

Although applications until now have not been widespread, they have been useful in locations like hospitals and remote hotels, where grid power is expensive and reliability is worth a premium. Experts predict, however, that fuel cells will become a more common part of our lives over the next few years.

The technology works by generating energy and heat through an electrochemical reaction between hydrogen, or a hydrogen-rich fuel, and oxygen. Hydrogen atoms enter at the anode and are ionised by being stripped of their electrons. In some cell types, oxygen enters at the cathode where it combines with electrons returning from the circuit and hydrogen ions that have passed through the electrolyte from the anode. In other types, the oxygen picks up electrons and travels to the anode, where it combines with hydrogen ions. The process produces little waste other than water, with waste heat often being harnessed to further improve efficiency.

Since the energy is created chemically, cells are not subject to the thermodynamic laws that limit conventional power plants and they are more efficient than traditional combustion methods. Each single fuel cell generates a tiny amount of dc electricity, which can be routed through an inverter if ac is needed, so cells are usually assembled in a stack.

The electrolyte plays a key role in the workings of fuel cells – it must permit only the appropriate ions to pass between anode and cathode since free electrons would disrupt the chemical reaction.

The different types of fuel cells are classed in terms of the electrolyte used (see table 1, over). Choices in cell development are generally constrained by the electrolyte, since the design and material of the electrodes are based on the electrolyte used. The type of fuel used also depends on electrolyte – some need pure hydrogen (requiring extra equipment to purify fuel); others tolerate some impurity but need higher temperatures to run efficiently.

Fuel cells have applications in large and small-scale electricity generation, chp, transport, and to replace batteries as portable power. The different cells operate at varying temperatures and this tends to affect their potential uses – lower temperature cells are better for mobile and portable applications, while high temperature cells are more useful in stationary electricity generation and chp.

There is a growing market for fuel cells, with transport being perhaps the largest possible area of use for the technology. Significant investment is required to develop the technology in cars, although some manufacturers have begun experimenting.

The market for distributed power generation and chp is weaker, but there are still possibilities for the introduction of fuel cells in these areas. Several companies are currently developing products: Johnson Matthey and TXU Energi are working on cells as a source of domestic heat and power; Innogy is developing a regenerative cell intended for electricity storage.

Most of the cell use in the UK to date has been in specialist areas and research. The first system in the UK for everyday use has recently been commissioned for Woking Borough Council's Pool in the Park. The International Fuel Cells PC25 system, due to be installed by the end of the year, should create less than 29 g of pollution per 1000 kWh of electricity generated, compared with almost 11·5 kg of pollutants for conventional combustion systems.

Allan Jones, energy services manager for Woking Council considers the Council to be a pioneer in the use of this kind of technology. "Fuel cells are of interest to us because the Council addressed energy efficiency years ago, way ahead of everyone else. We then started looking at climate change strategy. The need was not so much for renewable energy, but about what the Royal Commission identified. If by 2050 the amount of CO₂ was not reduced catastrophic changes in climate would occur," he stated. He hopes that the project will open up the market for fuel cells in the UK: "Getting a fuel cell in the UK where people can see how it works might encourage the take-up."

The Council hopes to make use of the water produced as a by-product of the electricity generation process. Jones said that the Council planned to sell the pure water produced to other industries.

Fuel cells provide a clean, energy efficient form of electricity generation. With water as their main by-product they are virtually non-polluting, and they emit lower levels of nitrogen, hydrocarbons and particulates than combustion generators. It is anticipated that the technology would improve air quality if its application were widespread.

The World Wildlife Fund (WWF) welcomes it as a move towards greener energy production. Its fuel cell specialist Russel Marsh confirms: "It is a technology we would encourage. It has enormous benefits as a completely emission-free process. I think that initially it will be used in transport, probably buses, as that will be the easiest way first of all." He hopes that as people become more aware of green issues the demand for more technology like fuel cells will increase: "People are becoming more aware of issues like climate change. We get lots of enquiries asking what people can do. On the other hand, people are concerned about being able to use their cars, so they need to start asking and demanding this technology from manufacturers. Some are, however, already experimenting with fuel cells."

Experts predict that the global value of the fuel cell business could reach £13 billion per year by 2025. Economic analyst Peter Schwartz, author of Future of the global economy – towards a long boom, is an optimistic supporter of fuel cell technology. He says that: "Most likely the fuel cell will be the power source of the next half-century as we transform the [electrical] infrastructure."

At present the problems of high manufacturing costs along with slightly limited capabilities are preventing the introduction of more fuel cell systems in mainstream applications, but the development of the technology is a continuing process.

The potential of fuel cells is tremendous. MCFC and SOFC technologies (see table 1) could bring extraordinary efficiencies to power generating stations: hot steam and CO₂ produced can be used to drive gas turbines to generate additional electricity, possibly pushing efficiency to a massive 80%. Despite these potential benefits, there remains a need to persuade customers that the initial capital outlay for these systems is worth it.

Marsh believes that increasing environmental awareness will make a difference to the market for fuel cells, but is realistic about the possibilities: "Some people will pay for fuel cell technology, but the only way to persuade the majority will be to make it less expensive."