By Charlotte Gliddon-Bush

The demand for cleaner sources of energy has prompted several companies to develop fuel cells for residential homes. PEI looks at the current technology and investigates the future of fuel cells in this market.

Since the introduction of the Kyoto Protocol the energy industry has been looking for new ways to produce cleaner energy in a more efficient way. In response to this demand, several companies – like Vaillant in Germany, Sulzer Hexis in Switzerland, Plug Power of the USA, and the Fuel Cell Initiative, a new consortium consisting of EWE AG, MVV AG, Ruhrgas AG, and Verbundnetz Gas AG – have decided to develop fuel cells for the residential market.

These fuel cells offer several benefits to the consumer. They are a cleaner and more reliable source of power than the power which is produced by some conventional power plants. The reliability of fuel cells has been highlighted as an obvious advantage, especially after the recent events in California, and this is an ideal reason for companies to keep on developing their fuel cells for this market.

In addition, fuel cells can offer home owners an alternative to joining the main-line grid. This system would, therefore, be ideal for homes in remote locations.

Bernadette Geyer, director of the Outreach Program at the US Fuel Cell Council explains further: “Fuel cells are becoming a more popular technology as they are highly efficient and because people are more aware of energy use, energy supply and energy costs and they are starting to look into technologies that will use natural resources more efficiently.


Figure 1. Vaillant hopes to start commercial sales of its Fuel Cell Heating Appliance system in Europe by 2004
Click here to enlarge image

“Another possible reason why fuel cells are really being looked into now would be the increasing need for reliable power.”

Ulf Bossel of the European Fuel Cell Forum expanded on this explanation: “In parts of the US there are frequent blackouts and brownouts so independent power would resolve this problem and allow homeowners to keep their refrigerators running.”

However, Bossel believes that the fuel cell currently offers little economic benefit to the homeowner. “The advantages to the homeowner is marginal in economic terms, but the homeowner will have more reliable power, more convenience and more safety.

“For the rest of the world it makes sense to produce power from fuel cells because they are cleaner, environmentally better than conventional power plants.”

Different fuel cells

Most companies are currently developing natural gas-powered fuel cells as hydrogen is still not an energy commodity.

“Companies are hoping that hydrogen will come around. But it doesn’t make sense to pump hydrogen through the pipeline, it will cost more energy to make hydrogen and deliver it to the people than to take the original energy to the homes,” said Bossel.

Geyer explained further: “Natural gas is looking to be the more popular potential fuel for stationary applications because there is already an infrastructure in place. Many homes are already connected to natural gas which would make it easier for them to switch to fuel cell power.”

The two types of fuel cells which are currently popular for this type of application are PEM – Proton Exchange Membrane – and Solid Oxide.

PEM fuel cells operate at relatively low temperatures and fairly high power density. The proton exchange membrane is a thin plastic sheet of complex chemistry that allows hydrogen ions to pass through it. The membrane is coated on both sides with carbon electrodes containing highly dispersed platinum particles that are active catalysts. Hydrogen is fed to the anode side of the fuel cell where the catalyst encourages the atoms to release electrons and become hydrogen ions (protons). The electrons travel around the cell in the form of an external electric current that can be utilized before returning to the cathode side of the fuel cell where oxygen is being fed. At the same time, protons diffuse through the membrane to the cathode where the hydrogen atoms are recombined and reacted with oxygen to produce water, thus competing the reaction. This type of fuel cell can digest only pure hydrogen. Natural gas and other hydrocarbon fuels have to be chemically converted to hydrogen by a reforming process.

Solid oxide fuel cells (SOFC) consist of a thin membrane of solid ceramic electrolyte (e.g zirconium oxide) covered on both sides by electrodes. Oxidation of the fuel cell takes place on the anode. As before, the electrons released by the anodic reaction flow via an external electrical current. On the cathode, atmospheric oxygen is dissociated and ionised. The circuit is closed by the transport of the oxygen ion through the ceramic electrolyte. Since oxygen ions are passed from the cathode to the fuel in the anode chamber, a wide variety of hydrocarbon fuels and hydrogen can be converted in a SOFC.

Home designs

Sulzer Hexis has designed a SOFC to meet the heat and electricity needs of a single-family home. In its design the excess heat generated by the fuel cell is collected and coupled with an auxiliary burner and fed to a water storage unit. This combined conversion allows for efficient fuel utilization.

The cell stack consists of several repeat elements connected in series. These generate an electric power of 1 kW. The modular auxiliary burner is switched on automatically if needed.

The Sulzer hexis fuel cells have undergone six field tests in Switzerland, Germany, Japan, the Netherlands and Spain and has acquired over 75 000 operating hours since 1998 (as of July 2001).

Sulzer Hexis is currently trying to form distribution partnerships with utilities who will own and operate the fuel cell systems in the market entry phase. These contractors will offer end-users a range of energy services.

Developing technology

Plug Power has focused its expertise on developing a PEM fuel cell system. The company first entered the residential market in 1998 when it demonstrated the Plug Power 7000, a 7 kW residential power system at a home in upstate New York. Since then, the system has been run on a regular basis, and in August 1999 the home was converted to natural gas operation. Plug Power has also entered into an agreement with GE Power Systems to set up a joint venture called GE Fuel Cells Systems, and Vaillant. Plug Power is working with these companies to develop new technology for the residential market.

Vaillant and Plug Power have designed and will shortly start the field tests on their Fuel Cell Heating Appliance (FCHA) which will also produce electricity as a by-product. The company is aiming to distribute its fuel cell product in multi-family homes across Europe, initially focusing on Germany, Holland, Austria and Switzerland where natural gas is widely available and “where environmental protection is an issue of paramount concern,” said Ebrulf Zuber, spokesperson for Vaillant.

He explained that the German government is involved in a scheme where solar panels on 100 000 rooftops are subsidized enabling the homeowners to sell the energy which is produced back to the grid. Zuber hopes that the German government may set up a similar scheme for fuel cells, opening up a huge market for their fuel cell system.


Figure 2. Market for hardware and services in the field of domestic fuel cells
Click here to enlarge image

Vaillant started to develop its PEM fuel cell system in 1999 and hopes to begin field tests by the beginning of 2002. It then hopes to install a further 400 appliances in Europe. The company is aiming to start commercial sales throughout Europe by 2004.

These devices will generate 4.5 kW electrical power and about 35 kW heat, covering the power and heat needs of a multi-family building with about four to ten buildings in each. Vaillant hopes to develop smaller units suitable for single family homes in the future.

Predictions

Vaillant is aiming for a European market share of 40 per cent and will initially market the new product to utilities. It believes that utilities could rent the devices to end-users and then manage the energy contracting.

“The technology could be installed as a plug and play application. End-users could keep existing boilers and use the FCHA when extra energy is needed,” said Zuber.

Bossel also highlighted other benefits to utilities: “Utilities should be glad to have fuel cells in their systems as they don’t have to extend the grids using transformers and other expensive technology. So utilities can serve more people with the existing grid.”


Figure 3. Vaillant’s European FCHA design for multi-family homes
Click here to enlarge image

Vaillant does, however, admit that the technology will come at a high price when it is made available to the general public.

“We have to face the same process as laptops and other similar applications. Evolution will reduce costs. Prototypes are quite expensive as they are just for tests. Even after we have installed the first 400 when we go on the market [they will still be quite expensive]. But after 5000 appliances the cost will be down to around DM 20 000 [$9200],” said Zuber.

Awareness of the need for cleaner and more reliable power is growing and the companies involved in developing fuel cells for the residential market are sure that they are in a winning market, and although the initial price of the fuel cells is high, Vaillant sees a positive future for the technology. Zuber explained: “From the very beginning we thought that by 2010 we could talk about 250 000 appliances in Northern Europe. From these 250 000 we think that Vaillant will have a 40 per cent share, but that is a very conservative estimate.”