An empirical equation [E = E 0-b log i-Rim exp (ni)] was shown to fit the experimental cell potential (E) vs. current density (i) data for proton exchange membrane fuel cells (PEMFCs), at several temperatures , pressures , and oxygen compositions in the. cathode gas mixture. The exponential term compensates for the mass-transport regwns of th~ E vs. z plot; i.e., the increase in slope of the pseudolinear region and the subsequent. rapid fall-off of the cell potential with increasing current density. As has been prevwusly shown, the terms E 0 ~nd b yield the electrode kmetic parameters for oxygen reduction in the PEMFC and R represents the resistance, predommantly ohmic and, to a small extent, the chargetransfer resistance of the electro-oxidation of hydrogen. The exponential term charactenzesthe mass-transport regwn of theE vs. i plot. The parameter n has more pronounced effects than the parameter m m this regwn. A physicochemical interpretation of these parameters is needed.

In 1990 the Schatz Energy Research Center (SERC) installed a PV array comprised of 192 ARCO M-75 modules. Prior to installation, Zoellick [1] carefully measured module performance and reported average peak power at normal operating cell temperature (NOCT) to be 39.88 W, which was 14.1% lower than the 46.4 W nameplate rating. For the past 11 years the array has been exposed to and employed in a cool, marine environment. Of the original 192 modules, 191 were recently tested in order to re-evaluate their performance.This paper describes the equipment, conditions, and procedure used in retesting the modules, and reports module performance results. Notable results are that average module short circuit current and maximum power production at NOCT have decreased by 6.38% and 4.39%, respectively.

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Abstract. A semi-mobile torrefaction and densification pilot plant was constructed in order to determine ideal operating conditions and evaluate briquette quality and throughput rate using forest residuals as the input feedstock. Experiments were conducted at various conditions with feedstock moisture content ranging from 4% to 25% (wet basis), reactor residence times of 10 and 20 min, and final product temperatures between 214°C and 324°C. Optimal operating conditions, evaluated based on throughput rate, specific electricity demand, torrefied briquette grindability, briquette volumetric energy density, and briquette durability, were identified to occur with a short residence time (10 min), low feedstock moisture content (<11% wet basis), and high final product temperature between 267°C and 275°C. These conditions were able to process 510 to 680 kg h-1 (wet basis) feedstock with a dry mass yield of 79% to 84% to produce torrefied biomass with a higher heating value of 21.2 to 23.0 MJ kg-1 (dry basis) compared to 19.6 MJ kg-1 for the original biomass. Torrefied briquettes produced at these conditions had a neatly stacked packing density of 990 kg m-3 and a volumetric energy density of 21,800 MJ m-3. Their specific grinding energy was an average 37% of the energy required to grind a raw biomass briquette. These torrefied briquettes were more durable (94% DU) than raw briquettes (85% DU) directly following production, but were less durable after undergoing temperature and humidity fluctuations associated with long distance transportation (74% DU for torrefied and 84% DU for raw biomass briquettes). Results from this pilot plant are promising for commercial scale production of high quality torrefied briquettes and should lead to additional research and development of a torrefaction system optimized for a higher throughput rate at these conditions. Keywords: Biomass, Biomass conversion technology, Bioenergy, Briquetting, Densification, Forest residuals, Pyrolysis, Torrefaction.

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