Volume 7, Issue 4, July 2015
Index of content:
- REGULAR ARTICLES
Performance investigation of multi-chamber microbial fuel cell: An alternative approach for scale up system7(2015); http://dx.doi.org/10.1063/1.4923393View Description Hide Description
The performance of a multi-chamber microbial fuel cell (MFC) was investigated that consisting of four anodes and a cathode component separated by a membrane. The arrangements of the anode and cathode chambers were similar to four individual MFCs stack connected electrically in parallel fashion by sharing a cathode chamber. The multi-anode chamber MFC produced maximum open circuit potential of 720 ± 20 mV and the peak power density of 52.8 mW/m2 (162.5 mA/m2) at 100 Ω as normalized to the anode surface area. The effect of cathodic parameters such as electrode area, shapes, and catholyte concentrations was studied as factors affecting the power production. The wastewater concentration of 8720 mg COD/l was achieved the peak power density of 135.4 mW/m2 (368 mA/m2) using a graphite electrode with catholyte concentration of 100 mM potassium ferricyanide and 150 cm2 cathode electrode area. The results demonstrated that the proposed design may be an alternative approach to obtain high power generation and small space occupation for the scale-up MFC system.
New control strategy for fast-efficient maximum power point tracking without mechanical sensors applied to small wind energy conversion system7(2015); http://dx.doi.org/10.1063/1.4923394View Description Hide Description
This paper proposes a new Perturb and Observe (P&O) Maximum Power Point Tracking (MPPT) algorithm for Small Wind Energy Conversion Systems to overcome the rapidity-efficiency trade-off and wrong behavior problems of the conventional P&O technique. The proposed algorithm works in two separate modes. The first mode is activated when the wind speed changes slowly. Under a rapid change of the wind speed, the second mode is switched to avoid the divergence of the system. The proposed algorithm requires only the measurement of the dc-link voltage and the dc current to realize the MPPT control, so no rotor speed measurement is needed, reducing the complexity of the overall system. The performance and the validity of the new MPPT algorithm have been proved by both simulation and experimental results.
Slow pyrolysis of olive stones in a rotary kiln: Chemical and energy characterization of solid, gas, and condensable products7(2015); http://dx.doi.org/10.1063/1.4923442View Description Hide Description
The aim of this work is to investigate the slow pyrolysis of olive stones in a rotary kiln as a means to increase the fuel properties and potential use of this renewable solid fuel. The pyrolysis process takes place primarily at temperatures between 300 and 500 °C resulting in the transformation of the solid biomass into a biochar, a pyrolysis liquid (up to 38.1 wt. %) and a non-condensable gas fraction (up to 35.4 wt. %). This thermal treatment has a positive influence in the fuel properties of the solid fraction in terms of increased C content (up to 75.9 wt. %), reduced O/C and H/C ratios (down to 0.28 and 0.03), reduced volatile matter and moisture content (down to 6.9 wt. % and below 1.0 wt. %, respectively), increased fixed carbon (up to 90.2 wt. %), increased Lower Heating Value (LHVo up to 37.1 MJ/kg) and energy density (26.7 GJ/m3). The process also involved changes in the surface chemistry (increasingly hydrophobic nature) and textural properties of the solid (formation of cracks and internal voids, resulting in the development of a pore structure of up to 0.193 cm3/g and a surface area up to 507 m2/g). The condensable and gas fractions resulting from the pyrolysis process may also be used for their fuel properties. Thus, the pyrolysis liquid exhibited a high water content (62.5 wt. %), a mass density of 1.063 kg/m3, a viscosity of 1.33 cSt, and a Higher Heating Value (HHVo) of 16.9 MJ/kg. The gas fraction resulting from the pyrolysis of olive stones contains high concentrations of combustible gases like CO and H2, and lower proportions of light hydrocarbons. The gas fraction exhibited HHV up to 6.83 MJ/Nm3 due primarily to CO and H2, while the formation of light hydrocarbons was very limited. The energy distribution resulting from the pyrolysis of olive stone at 700 °C (following completion of the thermal degradation) is as follows: solid fraction 48.2%; oil fraction 11.0%; and gas fraction and energy losses (by difference) 40.8%.