A novel Rh–Ir electrocatalyst for the oxygen reduction reaction and the hydrogen and methanol oxidation reactions

A novel Rh–Ir based material was synthesized by pyrolysis of an Ir₄(CO)₁₂/Rh₆(CO)₁₆ mixture in a reductive (H₂) atmosphere. The material was characterized by FTIR spectroscopy, X-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy, and was evaluated as electrocatalyst for oxygen reduction and hydrogen and methanol oxidation by rotating disk electrode measurements. The bimetallic material shows a high catalytic activity for the oxygen reduction reaction and is also capable to carry out the hydrogen oxidation reaction even in the presence of carbon monoxide in different concentrations (100 ppm and 0.5%), in contrast with commercial platinum catalysts, which become easily deactivated by CO. The activity of the catalyst for methanol oxidation is acceptable but still low in comparison with Pt–Ru. The results show that the new bimetallic catalyst is a potential candidate to be evaluated as both cathode and anode in a reforming hydrogen PEMFC, and as an anode in a direct methanol fuel cell.     

Ceramics and ceramic matrix composites for heat exchangers in advanced thermal systems—A review

In air-conditioning and energy-recovery applications, heat exchangers are very important to the overall efficiency, cost, and size of the system. Current heat exchanger designs rely heavily on fin-and-tube or plate heat exchanger designs, often constructed using copper and aluminum. Recent developments in material science—in particular, advances in ceramics and ceramic matrix composites—open opportunities for new heat exchanger designs. Some research directed toward using these materials for heat exchangers in other applications has been reported; however, there has not been a comprehensive study of the use of these emerging materials in both conventional HVAC&R systems and emerging energy technologies. This review reports the current state-of-the-art of ceramic materials for use in a variety of heat transfer systems.     

Biofuels from microalgae—A review of technologies for production,processing, and extractions of biofuels and co-products

Sustainability is a key principle in natural resource management, and it involves operational efficiency, minimisation of environmental impact and socio-economic considerations; all of which are interdependent. It has become increasingly obvious that continued reliance on fossil fuel energy resources is unsustainable, owing to both depleting world reserves and the green house gas emissions associated with their use. Therefore, there are vigorous research initiatives aimed at developing alternative renewable and potentially carbon neutral solid, liquid and gaseous biofuels as alternative energy resources. However, alternate energy resources akin to first generation biofuels derived from terrestrial crops such as sugarcane, sugar beet, maize and rapeseed place an enormous strain on world food markets, contribute to water shortages and precipitate the destruction of the world's forests. Second generation biofuels derived from lignocellulosic agriculture and forest residues and from non-food crop feedstocks address some of the above problems; however there is concern over competing land use or required land use changes. Therefore, based on current knowledge and technology projections, third generation biofuels specifically derived from microalgae are considered to be a technically viable alternative energy resource that is devoid of the major drawbacks associated with first and second generation biofuels. Microalgae are photosynthetic microorganisms with simple growing requirements (light, sugars, CO₂, N, P, and K) that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and valuable co-products.This study reviewed the technologies underpinning microalgae-to-biofuels systems, focusing on the biomass production, harvesting, conversion technologies, and the extraction of useful co-products. It also reviewed the synergistic coupling of microalgae propagation with carbon sequestration and wastewater treatment potential for mitigation of environmental impacts associated with energy conversion and utilisation. It was found that, whereas there are outstanding issues related to photosynthetic efficiencies and biomass output, microalgae-derived biofuels could progressively substitute a significant proportion of the fossil fuels required to meet the growing energy demand.     

Macro-economic impact of large-scale deployment of biomass resources for energy and materials on a national level—A combined approach for the Netherlands

Biomass is considered one of the most important options in the transition to a sustainable energy system with reduced greenhouse gas (GHG) emissions and increased security of enegry supply. In order to facilitate this transition with targeted policies and implementation strategies, it is of vital importance to understand the economic benefits, uncertainties and risks of this transition. This article presents a quantification of the economic impacts on value added, employment shares and the trade balance as well as required biomass and avoided primary energy and greenhouse gases related to large scale biomass deployment on a country level (the Netherlands) for different future scenarios to 2030. This is done by using the macro-economic computable general equilibrium (CGE) model LEITAP, capable of quantifying direct and indirect effects of a bio-based economy combined with a spread sheet tool to address underlying technological details. Although the combined approach has limitations, the results of the projections show that substitution of fossil energy carriers by biomass, could have positive economic effects, as well as reducing GHG emissions and fossil energy requirement. Key factors to achieve these targets are enhanced technological development and the import of sustainable biomass resources to the Netherlands.     

A novel approach to analyse incomplete design of experiments – Application to the study of the influence of operational parameters on the performance of a solid oxide fuel cell based micro-combined heat and power system

A SOFC based commercial μ-CHP system is characterized by Electrochemical Impedance Spectroscopy, using a 2⁴ full factorial test plan. The studied factors are: natural gas input power, ratio between oxygen and natural gas flow rates at the reformer inlet, stack average temperature and average operating cell voltage. Six replicates are performed in the domain centre. We performed equivalent circuit analysis and extracted three responses from each spectrum: ohmic resistance together with the two parameters of the CPE used in the model.However, one of our experiment is an outlier. To circumvent this problem, two methods described in the literature were applied: recalculation of missing response and introduction of a dynamic variable. Due their unsatisfactory results, we developed an innovative approach combining an iterative fitting of the multilinear model underlying any factorial design and an N-way ANOVA. Our method is successfully validated on the different 2⁴⁻¹ fractional designs deriving from the full factorial one.The only impacted response is the ohmic resistance. It increases as temperature decreases or as applied voltage increases. It is impacted by a strong synergistic effect of pressure and temperature and a compensating effect of pressure and applied voltage. No significant quadratic effect is observed.     

A continuum model for momentum,heat and species transport in binary solid-liquid phase change systems—II. Application to solidification in a rectangular cavity

A newly developed continuum model has been used with a well-established control-volume-based, finite-difference scheme to investigate solidification of a binary, aqueous ammonium chloride solution in a rectangular cavity. Advective transport of water enriched interdendritic fluids across the permeable liquidus interface has been identified as the primary mechanism for macroscopic species redistribution. The extent of this penetration is governed by the relative strengths of solutally driven mushy region flows and thermally driven flows in the bulk liquid. Unstable and double-diffusive conditions which accompany the discharge of interdendritic fluids into the liquid core have been shown to result in localized growth rate variations, remelting, and fluctuating bulk fluid transport behavior.