Odne Stokke Burheim

Through-Plane Thermal Conductivity of PEMFC Porous Transport Layers

We report the through-plane thermal conductivities of the several widely used carbon porous transport layers (PTLs or GDLs) and their thermal contact resistance to an aluminium polarisation plate. We report these values both for wet and dry samples and at different compaction pressures. We show that depending on the type of PTL and possible residual water, the thermal conductivity of the materials varies from 0.15 to 1.6 W K−1 m−1 — one order of magnitude. This behaviour is the same for the contact resistance varying from 0.8 to 11 10−4 m2 K W−1 . For dry PTLs the thermal conductivity decreases with increasing PTFE content and increases with residual water. These effects are explained by the behaviour of air, water and PTFE in between the PTL fibres.Copyright

Auto Generative Capacitive Mixing for Power Conversion of Sea and River Water by the Use of Membranes

The chemical potential of mixing two aqueous solutions can be extracted via an Auto Generative Capacitive Mixing, AGCM, cell using anionic and cationic selective membranes together with porous carbon electrodes. Alternately feeding sea and river water through the unit allows for the system to spontaneously deliver charge and discharge the capacitive electrodes so that DC electric work is supplied. Having a stack of eight cells coupled in parallel demonstrated the viability of this technology. An average power density of 0.055 W m−2 was obtained during the peak of the different cycles, though reasonable optimisation suggests an expectation of 0.26 W m−2 at 6.2 A m−2 . It was found that 86 ± 8 percent of the theoretical driving potential was obtained during the operating process. By studying the polarisation curves during charging and discharging cycles, it was found that optimising the feed fluid flow is among the routes to make AGCM with ionic selective membranes a viable salinity difference power source by mixing river and sea water. Another parallel route for increasing the exergy efficiency is lowering the internal ohmic resistances of the cell by design modifications.© 2011 ASME

Sonochemical and Sonoelectrochemical Production of Hydrogen

Reserves of fossil fuels such as coal, oil and natural gas on earth are finite. The continuous use and burning of these fossil fuel resources in the industrial, domestic and transport sectors has resulted in the extremely high emission of greenhouse gases, GHGs (e.g. CO2) and solid particulates into the atmosphere. Therefore, it is necessary to explore pollution free and more efficient energy sources in order to replace depleting fossil fuels. The use of hydrogen (H2) as an alternative fuel source is particularly attractive due to its very high specific energy compared to other conventional fuels and its zero GHG emission when used in a fuel cell. Hydrogen can be produced through various process technologies such as thermal, electrolytic, photolytic and biological processes. Thermal processes include gas reforming, renewable liquid and biooil processing, biomass and coal gasification; however, these processes release a huge amount of greenhouse gases. Production of electrolytic hydrogen from water is an attractive method to produce clean hydrogen. It could even be a more promising technology when combining water electrolysis with power ultrasound to produce hydrogen efficiently where sonication enhances the electrolytic process in several ways such as enhanced mass transfer, removal of hydrogen and oxygen (O2) gas bubbles and activation of the electrode surface. In this review, production of hydrogen through sonochemical and sonoelectrochemical methods along with a brief description of current hydrogen production methods and power ultrasound are discussed.

Influence of Electrode Gas Flow Rate and Electrolyte Composition on Thermoelectric Power in Molten Carbonate Thermocell

a Department of Materials Technology and Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway b Department of Mechanical and Industrial Engineering, University of Brescia, Brescia, Italy c Department of Electrical Engineering and Renewable Energy, NTNU, Trondheim, Norway d SINTEF Materials and Chemistry, SINTEF, Trondheim, Norway e Department of Chemistry, NTNU, Trondheim, Norway