An investigation of emissions and efficiency characteristics of a phosphoric acid fuel cell engine

There is immense interest in increasing efficiency and reducing emissions from power producing devices. This is especially true of the transportation application which contributes a significant portion of the energy consumption and emission production worldwide. One of the most promising technologies for clean, efficient propulsion systems is the fuel cell.; Based on modeling work completed in support of the Department of Energy Fuel Cell Bus Program, the University of Florida received a fully functional, 25 kW methanol-fueled, steam-reformed, liquid-cooled, phosphoric acid fuel cell engine designed for laboratory use. The engine was designed as a brassboard and was the building block of the 50 kW engines integrated into the three fuel cell buses. The brassboard engine is unique in that it was designed for laboratory use, thus allowing unusual access to the engine and electronics. The goal of this research was to begin development of the basic understanding of transportation fuel cell engine behavior, primarily in the areas of efficiency and emissions.; The net overall engine efficiency ranged from 13.5% at 6.5 kW stack power output to 32% at 20 kW stack power output. These values are well below many published values for efficiency. One reason for the low efficiency is all parasitic power losses were accounted for. Also, all flows of methanol were monitored. The engine has four methanol pumps, one pump for the primary fuel/water mixture and three ancillary pumps. The results of testing showed that at low power outputs, the ancillary flows were up to 75% of the primary fuel flow. Component interaction, control strategy limitations, etc. were investigated and the associated efficiency losses were documented to begin to develop an understanding of fuel cell engine performance; Emission testing showed that carbon monoxide (CO) was the primary regulated emission. At 6.5 kW stack power output, the CO levels were approximately 30 grams per hour, while at 20 kW the CO level was <0.2 grams per hour. The high levels and sources of CO at low stack power are established.