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Versa Power Systems SOFC Advantage

Power Density Advantage

Versa Power Systems has developed a proprietary micro-structure which gives its fuel cells very high power density (the amount of power measured in watts per square centimetre of surface area). Since beginning initial development in the labs of Global Thermoelectric in 1998, power density at 750°C operating temperature has increased more than five-fold to reach the threshold of the US Department of Energy's 2012 commercial power density goal.

This high power density allows Versa Power Systems' fuel cell stacks to be smaller, lighter and less expensive. In addition, Versa Power Systems' SOFC no longer needs to operate in the materials challenging regime of 800°C to 1,000°C. At temperatures below 800°C the interconnect plates that are used to direct fuel and oxygen flow, collect electrical current and hold the fuel cells in place in the stack, can be stamped from commercial stainless steel rather than made of exotic metal alloys or expensive conductive ceramic materials.

Thermal Cycling

Thermal cycling is the process of bringing a fuel cell system to operating temperature, then returning it to ambient temperature before returning to operating temperature. Planar SOFCs have not traditionally been capable of thermal cycling because of limitations in the glass seals used around the cells and gas manifold. When such a unit is thermally cycled, traditional glass seals crack, causing leaks and the rapid deterioration of the fuel cell stack. Versa Power Systems has developed a proprietary high-temperature compressive seal, permitting the stacks to be thermally cycled.

Fuel Reforming Advantage

In the foreseeable future, today's hydrocarbon fuel infrastructure will be the only economic source of hydrogen for fuel cells. In order to use hydrocarbons, these fuels must be reformed-a process whereby the hydrogen in the hydrocarbon fuel is separated from the carbon through a thermal reaction.

Unlike the popular PEM fuel cell, SOFCs do not require pure hydrogen fuel and therefore do not require expensive gas clean-up to remove carbon monoxide. Not only is it expensive to remove carbon monoxide, but any residual amount left in the hydrogen will poison the PEM membrane and significantly reduce its useful life. In contrast to these PEM fuel supply issues, Versa Power Systems' SOFC uses carbon monoxide as a fuel. This capability has enabled VPS to run a 2 kW SOFC generator using commercial natural gas piped into the development lab in Calgary, Alberta.

Installations of Versa Power Systems' SOFC generators running hydrocarbon fuel, offer highly significant advantages for system efficiency and combined heat and power applications. Pre-reforming of hydrocarbon fuels such as natural gas, propane, and even diesel, can be thermally integrated with the SOFC stack operation to effectively utilize some of the excess heat produced. Hydrocarbon fuels are effectively reformed in the temperature range of 600°C-750°C which matches Versa Power Systems generators very nicely. Furthermore, at these operating temperatures, any excess heat is easily captured for customer purposes such as building heating or process heat.

Stack Fabrication Scale-Up Advantage

Versa Power Systems has developed an integrated cell and stack pilot production and fabrication capability using commercial, ceramic production equipment, including Tape casting, Screen printing and single Co-firing (TSC), at VPS' 32,000 sq ft development facility that is capable of 2 MW per year output. This approach eliminates or significantly reduces full-scale manufacturing development cost and time.

With the latest TSC II cell fabrication process, VPS has reduced the start-to-end production time to 4 days and achieved a 90% or better yield with an overall plant capacity of 2,500 cells per week.

Versa Power Systems has also developed a user friendly, bar-coded, product tracking and database system, which is linked to state of the art statistical process control-- correlating electrochemical cell performance with any process variation as well as the raw materials used.