Search Results (6)

Sorbents for CO₂ capture based on CaO have been synthesized and tested for sorption-enhanced steam reforming (SESR) via the co-precipitation method. Various stoichiometries of MgO and CeO₂ have been utilized along with Cao and an optimum stoichiometry was identified providing the highest capacity and stability over cycling. The as-synthesized sorbents were structurally characterized by means of XRD and SEM. The thermal characterization was obtained via TGA. The porosity of the synthesized samples was measured by the N₂ adsorption and mercury porosimetry. Based on the outcomes of the current work, the sorbents with the highest capacities presented a highly porous structure with a porosity level higher than 65%. The sorbents were tested at high temperatures over repeated cycling (carbonation/decarbonation) to identify the stability of the synthesized sorbents over cycling. The results showed that the stoichiometry of 6:2:1 (CaO, MgO, CeO₂) could retain a capacity up to 25 wt% even after 45 cycles. Full article

The successful and fast start-up of proton exchange membrane fuel cells (PEMFCs) at subfreezing temperatures (cold start) is very important for the use of PEMFCs as energy sources for automotive applications. The effective thermal management of PEMFCs is of major importance. When hydrogen is stored in hydride-forming intermetallics, significant amounts of heat are released due to the exothermic nature of the reaction. This excess of heat can potentially be used for PEMFC thermal management and to accelerate the cold start. In the current work, this possibility is extensively studied. Three hydride-forming intermetallics are introduced and their hydrogenation behavior is evaluated. In addition, five thermal management scenarios of the metal hydride beds are studied in order to enhance the kinetics of the hydrogenation. The optimum combination of the intermetallic, hydrogenation behavior, weight and complexity of the thermal management system was chosen for the study of thermal coupling with the PEMFCs. A 1D GT-SUITE model was built to stimulate the thermal coupling of a 100 kW fuel cell stack with the metal hydride. The results show that the use of the heat from the metal hydride system was able to reduce the cold start by up to 8.2%. Full article

This work investigates life cycle costing analysis as a tool to estimate the cost of hydrogen to be used as fuel for Hydrogen Fuel Cell vehicles (HFCVs). The method of life cycle costing and economic data are considered to estimate the cost of hydrogen for centralised and decentralised production processes. In the current study, two major hydrogen production methods are considered, methane reforming and water electrolysis. The costing frameworks are defined for hydrogen production, transportation and final application. The results show that hydrogen production via centralised methane reforming is financially viable for future transport applications. The ownership cost of HFCVs shows the highest cost among other costs of life cycle analysis. Full article

Rechargeable magnesium ion batteries have recently received considerable attention as an alternative to Li- or Na-ion batteries. Understanding defects and ion transport is a key step in designing high performance electrode materials for Mg-ion batteries. Here we present a classical potential-based atomistic simulation study of defects, dopants and Mg-ion transport in Mg₆MnO₈. The formation of the Mg–Mn anti-site defect cluster is calculated to be the lowest energy process (1.73 eV/defect). The Mg Frenkel is calculated to be the second most favourable intrinsic defect and its formation energy is 2.84 eV/defect. A three-dimensional long-range Mg-ion migration path with overall activation energy of 0.82 eV is observed, suggesting that the diffusion of Mg-ions in this material is moderate. Substitutional doping of Ga on the Mn site can increase the capacity of this material in the form of Mg interstitials. The most energetically favourable isovalent dopant for Mg is found to be Fe. Interestingly, Si and Ge exhibit exoergic solution enthalpy for doping on the Mn site, requiring experimental verification. Full article

Low temperature methane steam reforming for hydrogen production, using experimental developed Ni/Al₂O₃ catalysts is studied both experimentally and numerically. The catalytic activity measurements were performed at a temperature range of 500–700 °C with steam to carbon ratio (S/C) of 2 and 3 under atmospheric pressure conditions. A mathematical analysis to evaluate the reaction feasibility at all different conditions that have been applied by using chemical equilibrium with applications (CEA) software and in addition, a mathematical model focused on the kinetics and the thermodynamics of the reforming reaction is introduced and applied using a commercial finite element analysis software (COMSOL Multiphysics 5.0). The experimental results were employed to validate the extracted simulation data based on the yields of the produced H₂, CO₂ and CO at different temperatures. A maximum hydrogen yield of 2.7 mol/mol-CH₄ is achieved at 700 °C and S/C of 2 and 3. The stability of the 10%Ni/Al₂O₃ catalyst shows that the catalyst is prone to deactivation as supported by Thermogravimetric Analysis TGA results. Full article

Phase change materials (PCMs) offer great potential as a latent heat energy storage technique to provide energy efficient systems in new and existing residential buildings. Due to their unique characteristic of high storage densities and latent heat properties, PCMs provide opportunities for greater energy storage in many applications for residential buildings. These applications include, but are not limited to, solar water heating, space heating/cooling, and waste heat recovery. This study reviews PCM systems in residential building applications, with a focus on their major disadvantages and concludes with proposals for future development. Several disadvantages of PCM use in the given application have been identified and include; super cooling, low thermal conductivity, phase segregation, fire safety, and cost. The issues caused by super cooling and phase segregation lead to thermal cycling degradation, limiting the useful lifecycle of the material. These issues could limit their potential in building applications, which require systems of a long lifespan. Low thermal conductivities can slow down the rate at which heat is distributed or absorbed from the building, which affect the occupants comfort and as well as the efficiency of the system. Ideas based on the current research on ways to limit these disadvantages are included in the study. This study also identifies that further research is required on novel maintenance ways for the PCM systems after they have been installed. Full article