Power hungry

Current solid oxide fuel cell systems (SOFCs) produce a typical power range of 1-5kW, far from sufficient to meet the multi-megawatt demands placed on a commercial power plant.

To help combat this, the EU has granted £3.9m (€5.8m) to a consortium of nine organisations led by VTT, the Technical Research Centre of Finland, to develop the technology to build large SOFC power plants. The three-year project started this year.

Dr Rolf Rosenberg, VTT’s chief research scientist, said producing a large power stack for a system of this size is just one of the challenges. ‘The important thing is we need not only the stack but also the whole system,’ he said.

‘The whole idea of making this project co-operative is that although the stack is vital, it is really just a part of the whole system. You need lot more components to have a working plant — a fuel delivery system, a reformer, a diffuser, pumps and heat exchangers, power, electronics and so on.’

Different plants

The programme will follow two different types of power plant. Rolls-Royce Fuel Cell Systems (RRFCS) is producing pressurised units, designed solely for power production. These incorporate a turbine driven by exhaust gases to improve overall electrical efficiency.

The other, known as planar SOFC, is a combined heat and power (CHP) unit, where the heat produced by the fuel cell is passed through a heat exchanger to heat water. Finnish marine and energy company Wärtsilä is the system integrator behind this system, and Topsoe Fuel Cells in Denmark is producing the stack system for it.

The organisations are developing SOFC power plant com- ponents that can benefit both the Rolls-Royce and Wärtsilä line of plant. ‘Although these plants are relatively different, they can use the know-how accumulated by the other companies to produce components for both systems,’ said Rosenberg.

One benefit of high-temperature fuel cells based on SOFC systems is the ability to use different types of fuels. ‘Usually when people talk about fuel cells they think of pure hydrogen as fuel but there is still no hydrogen infrastructure in place,’ said Rosenberg. ‘The advantage of SOFCs is we can use all kinds of hydrocarbon fuels.

‘Most of them use natural gas, but we can also use methane from different sources, like anaerobic fermentation of different kinds of organic waste or landfill gas. We can also use gasification gas made by heating coal or some solid biomass, which produces a hydrogen, carbon monoxide and carbon dioxide mixture. We can even use diesel oil, kerosene, methanol or ethanol.’

This fuel source versatility is useful for what is known as distributed power production, when the power plant is built where the fuel source is. This is particularly beneficial when using biofuels, which are not easy to transport.

Another benefit is that these power plants produce power with a relatively high electrical efficiency of 50 to 60 per cent.

Work packages

The project will bring together a great deal of new technology being developed by collaborators from across the EU, meaning the project management will be a challenge.

‘We have divided the project into what we call work packages,’ said Rosenberg. ‘Each of these is co-ordinated by a work leader and carried out by the participating commercial firms and research organisations. VTT will ultimately bring together all the packages.’

Rosenberg stressed that the project will not result in a fully operational megawatt power plant by the end of three years. ‘We are not going to build one that size during the course of the project, but we are developing concepts using much smaller systems, which we will later combine into large systems,’ he said.

‘We will demonstrate that these concepts work by building and testing a 50kW unit to verify that the concept is working. Using this, we can test the components and subsystems from which the main power system can later be built. So what we get is a clear understanding of how to build a large power unit and a lot of components ready to be used for that plant.’