Small fuel cell systems could be suitable for powering the home: they are compact, efficient and quiet. PEi looks at the technologies available and how manufacturers are hoping to break into the domestic market.

Ceres Power, UK

A rise in demand is resulting in an ever-increasing requirement for energy supply in both developed and developing countries. But efforts to meet this requirement also have to respect possibly conflicting additional demands – for example, there is growing awareness of the importance of security in national energy supply, and for the control of carbon emissions to limit environmental damage.

One of the consequences of increased demand is also the sheer cost of energy; in the UK average domestic electricity prices have increased cumulatively by 28.9 per cent since April 2003, and the average domestic energy bill stands at around £1000 ($1781) per annum. Estimates suggest that up to as much as 3 million people could be suffering from fuel poverty in the UK.

Effective solutions are needed that address these issues. It is likely that a combination of several technologies will provide the way forward, including new centralized generation systems based on coal, gas or nuclear; renewable resources such as large-scale wind or tidal systems; and microgeneration where energy is created at the point of consumption, for example in the home.

Figure 1. Fuel cell operation
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Microgeneration offers the potential for scalable deployment of new energy capacity, providing benefits for all stakeholders – utilities create new revenue streams, homeowners save on energy bills, and everyone gains from reduced emissions.

Playing a very significant part in this mix is fuel cell technology, since it has excellent fuel efficiency and provides silent, green power running off conventional hydrocarbon fuels such as natural gas. With this new energy generation in mind, UK-based Ceres Power is developing robust fuel cell systems intended for mass-market microgeneration appliances used in individual homes.

Government support

Worldwide, recognition is growing of the role of microgeneration and governments are taking steps to stimulate adoption and reduce barriers to entry.

In the UK, for example, a lively debate is underway regarding the country’s future energy direction. Chancellor Gordon Brown set up the Energy Research Partnership (ERP) in January 2006 to provide a forum where private and public entities can work together to facilitate a coherent national energy policy. Representatives of major utilities, power generation technology players (including Ceres Power as the only fuel cell company) and government departments and agencies are participating, and microgeneration is being actively considered as an option. Indeed, according to the Energy Savings Trust microgeneration products are estimated as having the potential to supply over one third of Britain’s total electricity needs in future.

As evidence of this interest, the UK government has recently announced its Microgeneration Strategy which identifies home microgeneration as a major technology suited to mass-market uptake. The report points out that “microgeneration technologies have the potential to make a significant contribution to our energy policy goals of tackling climate change, ensuring reliable energy supplies and tackling fuel poverty”.

Figure 2. Centralized vs. distributed generation efficiencies
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Policy measures have already been announced which are designed to promote rapid diffusion of residential combined heat and power (CHP) units. These include a reduction in VAT on such units from 17.5 per cent to 5 per cent, and grants for those wishing to install microgeneration systems. Furthermore, necessary standards for connecting microgeneration systems to the national grid have been agreed (G83/1) and clarity is emerging on the commercial terms under which utilities will buy back excess electricity generated by homeowners.

Whilst there is more that could be done by government to encourage uptake, the overall macroeconomic context is favourable – and becoming more so. Across Europe, other countries are also moving to encourage microgeneration; for example in Germany, the reward for domestic users selling electricity back to the grid is a premium price per unit. This has encouraged early adoption of technologies such as photovoltaics (PV), but with new cost-effective fuel cell technologies now emerging, mass-market adoption could well follow.

Fuel cell action

Fuel cells produce both electrical power and heat, by using an electro-chemical reaction to consume hydrogen (from a suitable fuel source) and oxygen (from the air), see Figure 1. They have some similarities to a battery, in that they are solid-state and highly efficient in converting energy from chemical to electrical form, but in contrast can provide continuous output as long as fuel and air are supplied. This allows operation as a long-term power source – clean too, since NOx, SOx, particulates and carbon footprint are reduced when compared to conventional combustion technologies.

There are several different fuel cell technologies that suit a variety of applications. For example, in order to power laptops and mobile phones a number of firms have been developing Direct Methanol Fuel Cells (DMFCs), miniaturizing the system components and addressing key packaging issues in order to deliver dramatically longer run times than existing batteries.

In automotive applications, Polymer Electrolyte Membrane (PEM) fuel cells are being considered as a potential long-term replacement for internal combustion engines in prime power usage. The organizations involved are striving to improve durability and reduce manufacturing costs, before this application can become mainstream. One barrier is the desirability of using pure hydrogen as a fuel source for PEMs, and the consequent requirement for generating, distributing and storing this gas; the difficulties involved are likely to mean the so-called ‘hydrogen economy’ will not be realized for many decades to come.

Figure 3. MicroCHP in the home
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In contrast, stationary power generation products based on fuel cells have been selling in niche markets for many years. These have mostly been systems of 100 kW or above, where Solid Oxide Fuel Cells (SOFCs) are highly applicable since they can use conventional fuels such as natural gas, propane or LPG rather than pure hydrogen. However, these systems have hitherto been very hard to downscale to the level required by a single home, where around 1 kW is an ideal size. Now, the vast market for such systems (small scale combined heat and power, or ‘microCHP’) has been opened up by technology, which Ceres Power is at the forefront of development.

Ceres Power has developed a unique metal-supported Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) that uses a new generation of ceramic materials to enable operation between 500-600°C, compared to 800-1000°C with conventional SOFCs. This in turn allows use of conventional stainless steel as the cell substrate, separating the functions of mechanical support from electrochemistry. This approach offers durability, high power density, mechanical robustness and the potential for thousands of on/off cycles for everyday usability. In addition, balance-of-plant (BOP) components can be adopted from mature supply chains in white goods and automotive, avoiding the need for time-consuming and expensive bespoke solutions that operate at more extreme temperatures. Critically, the technology uses low cost materials and existing mass-production techniques, and is now being scaled up for manufacture in volume.

MicroCHP systems are also being brought to market by organizations using Stirling Engine technology. These use external combustion as energy input to a rotating machine, and again can provide both heat and electrical outputs. However, such systems have a high heat-to-power ratio (approximately 7:1) making them suited to niche applications in buildings with higher hot water and space heating needs. Fuel cells have a near 1:1 ratio and high efficiency across a wide part-load range, making them very well suited to mass market microCHP across a wide range of housing stock, geography and lifestyles, maintaining electrical output even down to modest levels of heat demand.

Distributed microgeneration

Centralized generating schemes typically suffer substantial heat losses at the power station, and further resistive losses through the electricity grid. By contrast, when fuel is provided to a microCHP system directly in the home, both the heat and electrical outputs can be used and the distribution losses are much lower, see Figure 2.

Using existing natural gas distribution networks, millions of customers can benefit from the installation of domestic microCHP through lower gas usage, therefore reduced bills and emissions. Utilities offering microCHP systems to customers can share in these savings and benefit through new revenues, whilst being seen to bring responsible energy-efficient solutions to the market. Ceres Power’s fuel cell systems are particularly suitable for this application since they are designed for long lifetimes, high durability, robustness to repeated thermal cycling and excellent cost effectiveness.

Designed to replace existing boilers, Ceres Power’s domestic microCHP systems produce electrical power, heat and hot water, see Figure 3. The company is developing complete system designs to deliver microCHP products, and is working with key manufacturing, channel and supply chain partners to bring these to market.

Technology to market

Utility companies are recognizing the opportunities in distributed microgeneration and are keen to establish themselves in this emerging market. It is logical for utilities to combine their access to and knowledge of the market, plus their supply chain expertise, with specialist technology companies whose know-how and development skills can address the challenges inherent in this new generation of products.

Ceres Power has positioned itself as a provider of complete product systems. The company will produce complete value-engineered product designs, optimized for performance and cost. Initial volumes can be met by production via Ceres Power, but mass-market demand will be met via OEM assembly partners with the necessary capital plant, end-of-line test and other features for volume build. Ceres Power will manufacture and supply core ‘hot modules’ to assembly partners. To complete the chain Ceres will work with channel partners such as utilities and retailers to market the technology to end-users, see Figure 4.

Figure 4: Ceres Power value chain
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Partnerships like this mean that utilities have a number of options available when it comes to servicing their markets. Under one possible business model the utility could sell microCHP units to end users, together with installation and servicing packages. Alternatively, utilities could own and operate the microCHP units themselves, providing an opportunity to share the financial benefits with end users and drive new revenues, as well as provide longer-term contract arrangements to encourage customer loyalty.

Path to commercialization

Ceres Power announced in March 2006 that it has successfully designed, built and tested a 1 kW production engineered fuel cell stack capable of generating sufficient power for the average home. The stack represents a breakthrough in both size and weight, being smaller and lighter than a typical car battery. It is designed to be reliable, robust and economical, lending itself to rapid mass-market uptake.

In the UK market, Ceres Power has established a partnership with British Gas, which estimates that Ceres technology is “immediately accessible by 14.5 million UK households”. Ceres Power has recently announced a £2.7 million programme with British Gas, part-funded by the UK government, to design, build and evaluate fuel cell microCHP units for the UK residential market. British Gas commented: “Our partnership approach acknowledges our confidence in the future of micro-power and the development of Ceres fuel cells which are uniquely designed to appeal to the demands of a mass market.”

As yet, no launch date has been announced as to when systems will be commercially available. The complete system will undergo a series of in-house tests before end-user trials begin. With regards to price, Bob Flint, commercial director at Ceres Power commented: “There will be a modest premium compared to the cost of a conventional condensing boiler but we anticipate a short payback time when considering the energy savings.”

Well placed

There is no illusion that tackling the key issues of climate change, reliable energy supplies and fuel poverty is going to be easy, but it is extremely positive that governments are assessing options and encouraging debate within industry in an effort to provide solutions to these growing problems. It is clear that microgeneration can be an essential element of the future energy supply mix, and metal supported Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) technology is a highly competitive solution which can enable mass market adoption.

By providing solutions to homeowners, business users, utilities, and governments, which will improve energy security, help address profound climate change issues and save consumers money, Ceres Power is well placed to address this exciting growth opportunity.