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Research Papers

J. Electrochem. En. Conv. Stor.. 2017;13(4):041001-041001-8. doi:10.1115/1.4035352.

This paper describes experimental testing of a “geothermic fuel cell (GFC),” a novel application of solid-oxide fuel cells for combined heat and power. The geothermic fuel cell (GFC) is designed for in situ oil-shale processing. When implemented, the GFC is placed underground within an oil-shale formation; the heat released by the fuel cells while generating electricity is transferred to the oil shale, converting it into high-quality crude oil and natural gas. The GFC module presented here is comprised of three 1.5-kWe solid-oxide fuel cell (SOFC) stack-and-combustor assemblies packaged within a stainless-steel housing for the ease of installation within a bore hole drilled within the earth. The results from above-ground, laboratory testing of the geothermic fuel cell module are presented, with a number of operating conditions explored. Operation is demonstrated under hydrogen and natural-gas reformate fuels. The combined heat-and-power efficiency ranges from 56.2% to 74.2% at operating conditions that generally favor heat generation over electricity production. Testing of the geothermic fuel cell module over a wide operating range in a controlled, laboratory setting provides a valuable data set for developing more-detailed electrochemical and heat transfer models of module operation.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2017;13(4):041002-041002-7. doi:10.1115/1.4035624.

An 8 mol. % yttria stabilized zirconia (8YSZ) coating has been prepared on a Cr-containing stainless steel interconnect (SS410) to improve the chemical compatibility of a BaO–B2O3–SiO2 sealing glass with the SS410. Three different methods as, grinding the 8YSZ coating prior to the sealing (fixture A), putting an interlayer glass on the 8YSZ coating prior to the sealing (fixture B), and exerting an external compressive force of ∼10.28 kPa during the sealing (fixture C), have been used to improve the thermal cycle stability of the sealing glass. The fixture A (using the grinding method) and the fixture B (using the interlayer method) both show poor thermal cycle stability. For the fixture C, the external compressive force is found to help the self-healing of the sealing glass. Due to the good chemical compatibility of the sealing glass with the 8YSZ coating, the sealing glass of the fixture C exhibits super long-term thermal cycle stability. The leak rates of the sealing glass of the fixture C show nearly no increase up to 280 thermal cycles, after which the leak rates increase slowly with the thermal cycles and the leak rate is still less than the Solid Energy Convergence Alliance (SECA) limit at the 626th thermal cycle.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2017;13(4):041003-041003-7. doi:10.1115/1.4035731.

Pr1.9A0.1NiO4 (A = Ca, Sr, Ba) are synthesized and characterized by X-ray powder diffraction (XRD), infrared spectrum (IR), and X-ray photoelectron spectroscopy (XPS). The effects of alkaline earth doping on the covalence of Pr–O and Ni–O bond, the mean valence of Ni, and the hydroxide absorption ability of material surface are studied. It is found that the covalence of Pr–O and Ni–O bond increases with the decrease of alkaline earth element radius. Meanwhile, the mean valence of Ni and the surface hydroxide absorption ability are enhanced. The electrochemical measurement results indicate that the O22 /OH replacement reaction is facilitated by the increase of mean valence of Ni in the material. The best oxygen reduction reaction (ORR) activity is found in Pr1.9Ca0.1NiO4. The current density of 2.16 mA cm−2 is obtained at a potential of −0.6 V (versus Hg/HgO). The tafel slope is 66.48 mV decade−1, close to Pt/C material.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2017;13(4):041004-041004-5. doi:10.1115/1.4035803.

Localized temperature gradients in a polymer electrolyte fuel cell (PEFC) are known to decrease the durability of the polymer membrane. The most important factor in controlling these temperature gradients is the thermal contact resistance at the interface of the gas diffusion layer (GDL) and the bipolar plate. Here, we present thermal contact resistance measurements of carbon paper and carbon cloth GDLs over a pressure range of 0.7–14.5 MPa. Contact resistances are highly dependent upon the clamping pressure applied to a fuel cell, and in the present work, contact resistances vary from 3.5 × 10−4 to 2.0 × 10−5 m2 K/W, decreasing nonlinearly over the pressure range for each material tested. The contact resistances of carbon cloth GDLs are two to four times higher than contact resistances of carbon paper GDLs throughout the range of pressures tested. The data presented here also show that the thermal resistance of the sample is negligible in comparison to the thermal contact resistance. Controlling temperature gradients in a fuel cell is desirable, and the measurements presented here can be used to more accurately predict temperature distribution in a polymer electrolyte fuel cell.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2017;13(4):041005-041005-6. doi:10.1115/1.4035847.

In this paper, we present experimental studies of electrochemical performance of an all-vanadium redox flow battery cell employing an active area of 103 cm2, activated carbon felt, and a novel flow field, which ensures good electrolyte circulation at low pressure drops. Extended testing over 151 consecutive charge/discharge cycles has shown steady performance with an energy efficiency of 84% and capacity fade of only 0.26% per cycle. Peak power density of 193 mW cm−2 has been obtained at an electrolyte circulation rate of 114 ml min−1, which corresponds to stoichiometric factor of 4.6. The present configuration of the cell shows 20% improved in peak power and 30% reduction in pressure drop when compared to a similar cell with a different electrode and a serpentine flow field.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Electrochem. En. Conv. Stor.. 2017;13(4):044501-044501-5. doi:10.1115/1.4035351.

Thermal management of Li-ion batteries utilizing internal cooling method is the promising way to keep these batteries in an appropriate temperature range and to improve the temperature uniformity. In this study, three-dimensional transient thermal analysis was carried out to investigate the effects of size of embedded microchannels inside the electrodes on the thermal and electrical performances of a Li-ion battery cell. Based on the ratio of the width of microchannels to the width of the cell, different cases were designed; from the ratio of 0 (without any microchannels) to the ratio of 0.5. The results showed that increasing the size of the microchannels from the width ratio of 0 to the width ratio of 0.5 can reduce the maximum temperature inside the battery cell up to 11.22 K; it can also improve the temperature uniformity inside the battery cell. Increasing the electrolyte flow inlet temperature from 288.15 K to 308.15 K can enhance the temperature uniformity inside the battery and the cell voltage up to 33.20% and 2.79%, respectively. Increasing the electrolyte flow inlet velocity from 1 cm/s to 10 cm/s can reduce the maximum temperature inside the battery cell up to 8.09 K.

Commentary by Dr. Valentin Fuster

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