Laser welding of plastics for energy storage system

Fuel cell module joints

A novel energy storage system, requiring several equally novel joining processes has been developed by National Power PLC.

The Regenesys TM energy storage system is based on fuel cell technology and functions like a very large rechargeable battery. It is used in conjunction with a power station.

Electrical energy is converted into chemical potential energy by charging two electrolyte solutions. This stored energy can later be discharged on demand.

The system offers quick response times and the ability to deliver large quantities of stored energy, and allows the variations in output from a power station to be smoothed in a cost-effective manner. The station can therefore operate at optimum efficiency at all times and the maximum capacity of a given station can be reduced.

At the heart of the Regenesys TM system is a fuel cell module comprising electrodes, ion selective membranes and protective housings. Work began at TWI in 1993 on the development of the unique joining technology required for manufacture of the system.

The success of the joining methods adopted in the Regenesys TM system is critical. Any leakage of the electrodes would affect the efficiency of the energy storage process.

TWI and National Power worked together to develop the technology for joining the electrodes to their protective frame using transmission laser welding. Laser welding was selected following comparison with many other plastics processes because of the ability to make high speed sealed joints between components with a seam length over 3m long. A technique using clamped components and a robotically manipulated laser was found to be successful.

The adoption of what is one of the first major uses of laser welding of plastics is likely to result in substantial savings in production costs for National Power.

TWI has also contributed to several other aspects of the development of the cell manufacture including investigating methods to join the membrane to the supporting frames and the surfacing of electrodes.


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