The Danish company Dantherm Power has recently announced its plans to sell solid oxide fuel cell (SOFC) plants as environmentally-friendly power stations for private homes. Even though the project is only in its infantile stages, the company predicts the now bulky prototype will evolve over the next few years as the green alternative to power generators, or act as a buffer for buildings that are powered by renewable but intermittent energy sources such as wind or solar.

How solid oxide fuel cells work

A solid oxide fuel cell is a device that produces electricity directly from the oxidation of a fuel. A single cell is a flat, thin structure generating a voltage of only about 1 volt but, when properly stacked and combined, their small output voltage and wattage can add up to reach much higher values.

The cells operate at very high temperatures and their theoretical efficiency in terms of electricity generation can reach a remarkable 60 percent; when used as combined heat and power (CHP) plants, they become even more effective. Their high efficiency — which translates into a smaller carbon footprint — and their low emissions of nitrogen and sulphur oxides make solid oxide fuel cells a strong horse to bet on in the technological race for cleaner energy.

These cells could be deployed as combined heat and power (CHP) plants for a single home's needs, which would cut wasteful transmission loss in both the electricity and the heating network. Combined with today's large CHP units, these "micro CHP" plants could be used either on their own, or as a buffer for clean but intermittent energy sources such as wind turbines and solar panels.

The timeline

Micro CHP plants are now in a prototype stage and, as the company itself put it, "the size of an overgrown American fridge." For the time being, stress was put on the ability to supervise and maintain the device rather than reducing its size; production models will however be reduced, the company promised, to approximately the size of a dishwasher.

Dantherm Power is producing a limited number of systems that will be put into operation among professional users like plumbers or electricians, who will be able to provide feedback and solve problems that might arise with these early prototypes. These first plants will generate 1 kW of power and 1 kW of heat and will be powered by natural gas.

There will be seven more micro CHP plants in operation as of early 2011, and in September 2011, another 15 will be installed in private homes in Southern Jutland, Denmark for a final trial. Starting in 2012 and progressively until 2015, the company predicts that the reduced costs and improved specifications and reliability will encourage more and more people to replace their old furnace with a SOFC micro CHP plant.

The mini plants will initially be fueled by natural gas, and possibly by methanol and liquefied petroleum gas, or even biofuels in the later stages. In the long term, fuel cell power plants will hopefully replace the more polluting, less efficient generators powered by diesel or gas that are often used as backup power sources in countries where the grid is not as stable as in Denmark and other developed countries.

The product is being developed thanks to a long-term collaboration between Topsoe Fuel Cell, which developed fuel cell stacks into a commercial stage, Risø DTU, and Dantherm Power.