Renewable Energy Global Innovations featured article: Fatty acids and related phase change materials for reliable thermal energy storage at moderate temperatures
The post Prof. Mary Anne White appeared first on Renewable Energy Global Innovations.
Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)
Bio-oils are becoming alternatives to fossil fuels in view of the ever rising global energy demands, greenhouse emissions, and crude oil shortage. Bio-oils extracted from lignocellulosic biomass are composed of multicomponent molecules extracted from lignin, cellulose, and hemicellulose. The lignin component of lignocellulose is a promising renewable feedstock for the production of a number of chemicals and fuels. Lignin has an advantage over its counterparts hemicellulose and cellulose considering that bio-oils extracted from lignin can be upgraded to higher quality transportation fuels. This is in view of the high stability of the lignin aromatic structures with reference to resonance stabilization.
Fast pyrolysis has been an extensively applied method for converting lignin into bio-oil. Unfortunately, the potential of the resulting bio-oil is limited by the presence of a number of oxygenated functional groups, which in consequence lead to undesirable physicochemical attributes including low thermal and chemical stability, low heating values, easy corrosiveness and high density. In addition, lignin-extracted bio-oils are incompatible with either direct use or in combination with a petroleum fraction. This has forced researchers to look for alternative strategies which can enhance the commercial viability of lignin-extracted bio-fuels for use as a transportation fuel.
One method to remove chemically bonded oxygen from lignin-extracted oil and therefore enable the use of lignin-extracted bio-fuels is through catalytic hydrodeoxygenation processes. However, the direct application of catalysts in such processes is associated with numerous challenges owing to the complex nature of its oxygenated aromatic elements such as anisole, furan, benzofuran, and phenols. In order to overcome these issues, heterogeneous catalysts are attracting much attention, containing both a metal centre for the hydrogenation of the acidic support and an aromatic ring for the deoxygenation. While noble metals such as platinum, palladium, and ruthenium have been used in this process, their application is limited by the high cost and scarcity of these noble metals. Therefore, researchers have focused their attention on transition metal based catalysts including cobalt, nickel, iron, and copper-nickel.
Putla Sudarsanam and Suresh Bhargava at the Centre for Advanced Materials and Industrial Chemistry, School of Science, RMIT University in Australia in collaboration with Murtala Ambursa, Lee Hwei Voon, and Sharifah Bee Abd Hamid at the University of Malaya investigated the preparation, characterization and catalytic application of bimetallic Cu-Ni catalysts supported on Ti-MCM-41 for the hydrodeoxygenation of guaiacol. Their research work is published in the journal Fuel Processing Technology.
The authors prepared Cu-Ni catalysts supported on either Ti-MCM-41 or pure MCM-41 and compared their catalytic efficiencies for the hydrodeoxygenation of guaiacol. They performed the catalytic experiments in an autoclave reactor and investigated the effect of hydrogen pressure on guaiacol conversion as well as product selectivity.
Through the catalytic activity investigation, the authors observed that the CuNi/Ti-MCM-41 catalysts had a higher catalytic performance in guaiacol conversion as well as cyclohexane selectivity as opposed to a CuNi/MCM-41 catalyst. The high catalytic activity of the CuNi/Ti-MCM-41 catalyst was as a result of the cooperative function of the larger surface area, hexagonal pore geometry, medium-sized mesopores, adequate acidic sites, and excellent redox attributes. For this reason, Ti-MCM-41 is an efficient catalyst support for the hydrodeoxygenation of oxygenated elements to saturated hydrocarbons.
The research team also found that increased hydrogen pressures improved the guaiacol conversion and selectivity of the oxygenated compounds to hydrocarbons over the Ti-MCM-41 supported CuNi catalyst, increasing the impact of these catalysts within this important field of research.
Murtala M. Ambursa, Putla Sudarsanam, Lee Hwei Voon, Sharifah Bee Abd Hamid, Suresh K. Bhargava. Bimetallic Cu-Ni catalysts supported on MCM-41 and Ti-MCM-41 porous materials for hydro-deoxygenation of lignin model compound into transportation fuels. Fuel Processing Technology, volume 162 (2017), pages 87–97.
Go To Fuel Processing Technology
The post Bimetallic Cu-Ni catalysts supported on MCM-41 and Ti-MCM-41 porous materials for hydrodeoxygenation of lignin model compound into transportation fuels appeared first on Renewable Energy Global Innovations.
Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)
Phase change materials (PCMs) are important for thermal energy storage applications, especially in buildings and in solar thermal systems. The use of PCMs can increase energy efficiency by storage of solar thermal energy, and reducing heating and cooling demands. Suitable phase change materials need to be inexpensive and reliable, with high latent heats and a phase change at a temperature appropriate to the application. Organic phase change materials can satisfy many of these criteria and are suitable for latent-heat thermal energy storage systems operating in the ambient-to-moderate temperature range. Non-paraffin organic PCMs such as esters, fatty acids and fatty alcohols are particularly attractive because these materials are non-toxic and can be extracted from renewable sources, such as from plant and animal fat. They are also abundant and inexpensive, with a commodity cost of around $1/kg for fatty acids, for example. Their economic and embodied energy payback times can be very favorable.
The optimal design of an energy storage system requires accurate data regarding the thermophysical properties of PCMs. Furthermore, for phase change materials to be useful and reliable in their applications, they must be chemically and thermally stable after many melt-freeze cycles, and must be chemically inert with the materials with which they are in contact. For the very promising fatty acid PCMs, there were significant knowledge gaps and even inconsistencies. For example, there are considerable discrepancies between the values reported by different researchers for the latent heat of fusion and the phase change temperature of the same fatty acid PCM. In addition, thermal properties, such as the thermal conductivity and heat capacity, which are especially necessary for numerical studies for optimization, were largely unknown.
Researchers led by Professor Mary Anne White at Dalhousie University in Canada presented a comprehensive analysis of the thermophysical properties, thermal stability and chemical compatibility of six important organic PCMs: dodecanoic acid, decanoic acid, hexadecenoic acid, tetradecanoic acid, 1-octadecanol, and octadecanoic acid. Their research work is published in the journal Solar Energy Materials and Solar Cells. “We focused on fatty acid PCMs with melting temperatures between 30 and 70 °C because these materials span a wide range of thermal energy storage applications, from integration in building materials and residential solar water heating systems to cooling of portable electronic devices. They are cheap and can be sustainably sourced. They are also useful for preparing new PCMs by forming eutectic mixtures with lower melting temperatures”.
The research team implemented consistent procedures and experimental methods for all six phase change materials to provide direct comparisons. They accurately measured the thermal properties of the PCMs in the solid and liquid phases and related physical properties. In addition to thermophysical characterization, the authors determined the thermal stability of phase change materials over thousands of freeze-thaw cycles, as well as their chemical compatibility with 16 different materials. “Chemical compatibility of PCMs with materials is very important information but had been significantly overlooked in this field. For instance, many studies consider the addition of metallic fillers to enhance the thermal conductivity of fatty acid PCMs, but it is not known whether the fatty acids will react with these fillers over time”.
From the long-term cycling results, the authors observed that all the six phase change materials studied were thermally stable over 3000 melt-freeze cycles. In fact, there were no significant changes in the heats of fusion and melting temperatures, even for a low-purity sample of hexadecenoic acid. For this reason, it was determined that these PCMs are thermally reliable for long-term thermal energy storage applications.
The authors also investigated chemical compatibilities of the phase change materials with nine metal alloys and seven plastic materials. “We chose a wide range of materials which are found in most of the thermal energy storage applications that these PCMs were considered for in previous studies, or will likely be used for in the future. For example, copper and aluminum are typical filler materials, whereas the magnesium alloy, Mg AZ91D, and polycarbonate are commonly used in today’s portable electronic devices”. They found that two copper alloys, namely Cu110 and Cu101, and one magnesium alloy, Mg AZ91D, were incompatible with the fatty acids, while the nickel alloy Ni C7521 was compatible only with octadecanoic and hexadecenoic acids. They observed that octadecanol was compatible with all the alloys. Polycarbonate was the only plastic material that did not react significantly with any of the phase change materials investigated.
The in-depth information provided in the study conducted at Dalhousie University regarding the thermophysical properties, thermal stability and chemical compatibility of organic non-paraffin phase change materials provides all the required data to design and optimize thermal energy storage systems in the temperature range 30 to 70 °C, for applications from the built environment to compact electronic devices.
Samer Kahwaji, Michel B. Johnson, Ali C. Kheirabadi, Dominic Groulx, Mary Anne White. Fatty acids and related phase change materials for reliable thermal energy storage at moderate temperatures. Solar Energy Materials and Solar Cells, volume 167 (2017), pages 109–120.
Go To Solar Energy Materials and Solar Cells
The post Fatty acids and related phase change materials for reliable thermal energy storage at moderate temperatures appeared first on Renewable Energy Global Innovations.
Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)
Climate change mitigation and carbon emission reduction policies have been taking center stage in Australia in the last decade. Australians are broadly in favor of developing clean sources of energy but there’s a political divide about how to approach climate change. To prove its commitment and determination in championing against global warming, the Australian government committed to reduce emissions by 26-28% on 2005 levels by 2030. However, the achievability of such stringent target with the current subsidized emissions abatement policy has been put into question. Regardless, the Emissions Trading Scheme has been demonstrated as a good policy for Australia owing to its small unfavorable effects on the economy.
Dr. Duy Nong at Colorado State University with Dr. Sam Meng and Professor Mahinda Siriwardana at University of New England in Australia evaluated the effects of the proposed Emissions Trading Schemes on the Australian economy as well as the emissions level using MONASH-Green model, and a database containing detailed energy sectors. In their study they applied the stylized BOTE macro model developed by Adams and Parmenter (2013) in order to inform the macroeconomic results generated by the full model. Their work is now published in the research journal, Energy Policy.
The researchers commenced by replacing the output production function in MONASH Green with the ORANI-G model production system as their study did not contain composite commodity outputs. They then altered the input demand structure in MONASH-Green. The team then collected and compiled database from a variety of sources. After policy design, they developed a simulation where they considered microeconomic effects, effects on households, emissions trading among sectors and effects on sectoral outputs and employment.
From the simulation results, the authors demonstrated that the costs of the proposed emissions trading scheme were as low as of those of related studies conducted earlier by Adams et al. For example, it was seen that the permit price would have to increase from A$4.1 in 2015 through A$13.1 in 2020 to A$41.3 in 2030 in order to enable Australia to achieve the 2020 and 2030 emissions targets. More so, the operation of the proposed Emissions Trading Scheme in Australia would cause the economy to contract progressively over the lifetime of the Emissions Trading Scheme. This is due to the fact that the energy sectors will tend to substitute high emission-intensive energy commodities such as brown coal with black coal. Additionally, employment at sectoral level will fluctuate in line with variations in their outputs.
Thus the MONASH-Green model has been successfully used in their study to assess the effects of a proposed Emissions Trading Schemes on the Australian economy, particularly on the energy sectors and multi household groups. The simulation results indicate that the current price of carbon permits cannot suffice to meet the set carbon reduction targets by 2030 without prior adjustments and reviews. These results lend strong support towards the transition to renewable energy. This policy study is therefore likely to be of continuing relevance to Australia and could form future climate policy.
Duy Nonga, Sam Meng, Mahinda Siriwardana. An assessment of a proposed ETS in Australia by using the MONASH-Green model. Energy Policy 108 (2017) 281–291
Go To Energy Policy
The post An assessment of a proposed ETS in Australia by using the MONASH-Green model appeared first on Renewable Energy Global Innovations.
Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)