• Energy Research

Abstract Background Parabolic Trough Solar Collector (PTSC) is one of the most popular and an effective device that converts solar radiation into a heat or useful energy. However, it suffers from high temperature gradient and low thermal efficiency. The solution for this problem is to use new advanced coolants (hybrid nanofluids) in order to enhance PTSC's thermal efficiency. Methods A numerical analysis on the thermo-hydraulic performance of a PTSC receiver's tube equipped with conical turbulators is presented. The Navier-Stokes equations are solved using Finite Volume Method (FVM) coupled with Monte Carlo Ray Tracing (MCRT) method. The flow and thermal characteristics as well as entropy generation of the PTSC's receiver tube are investigated for three hybrid nanofluids (Ag-SWCNT, Ag-MWCNT, and Ag-MgO) having a mixing ratio of (50:50) dispersed in Syltherm oil 800, Reynolds number (5000 to 100,000) and fluid inlet temperatures (400 to 650 K). Significant findings The conical turbulators effectively augmented the thermal performance by 233.4% utilising Ag-SWCNT/Syltherm oil instead of pure Syltherm oil. The performance evaluation criterion is found to be in the range of 0.9–1.82. The thermal and exergetic efficiencies increased by 11.5% and 18.2%, respectively. The maximum decrement in the entropy generation rate and entropy generation ratio are 42.7% and 33.7%.

Thermochemical conversion process is one of the most promising routes to harness the potential of oil palm biomass as renewable energy alternative in Malaysia. Despite this potential, there is a lack of comprehensive study that characterises the complete spectrum of oil palm biomass. In this work, thermogravimetric-mass spectrometry (TG-MS) results of five oil palm biomass, i.e., oil palm trunk (OPT), palm kernel shell (PKS), oil palm frond (OPF), mesocarp fibre (MF) and empty fruit bunch (EFB), in pyrolysis and combustion conditions are presented and analysed. Kinetic studies on the TG data of these biomass were performed using Coats–Redfern integral method and Sestak–Berggren function to determine the activation energy and the reaction mechanism at different thermal decomposition stages. Pyrolysis of hemicellulose, cellulose, and lignin occurs at 140–331, 235–435, and 380–600 °C, respectively, while combustion of hemicellulose, cellulose, and lignin took place at 140–313, 225–395, and 372–600 °C, respectively. The activation energy was the highest for cellulose decomposition in both pyrolysis and combustion cases. Phase boundary reaction dominated during hemicellulose and cellulose decompositions, while nucleation dominated during lignin decomposition and char oxidation. MS results show that majority of the gases came out between 250 and 600 °C, mainly from CH4 and H2O in pyrolysis case and from CH4, CO2 and H2O in combustion case. Other than these major gases, NO, NO2 and SO2 were also generated although in much lower proportion compared to these gases. Based on TG-MS results, the best potential application for each biomass was also identified where OPT and OPF are suggested for gasification and fermentation, PKS for bio-char production and combustion, MF for bio-oil production, combustion, and bio-char production and EFB for bio-oil and bio-char production.

Abstract Carbon dioxide (CO 2 ) is a greenhouse gas found primarily as a main combustion product of fossil fuel as well as a component in natural gas, biogas and landfill gas. The interest to remove CO 2 from those gas streams to obtain fuel with enhanced energy content and prevent corrosion problems in the gas transportation system, in addition to CO 2 implications to the climate change, has driven the development of CO 2 separation process technology. One type of technology which has experienced substantial growth, breakthroughs and advances during past decades is membrane-based technology. The attractive features offered by this technology include high energy efficiency, simplicity in design and construction of membrane modules and environmental compatibility. The objective of this review is to overview the different types of membranes available for use including their working principles, current status and development which form the primary determinants of separation performance and efficiency. The emphasis is toward CO 2 /CH 4 separation, considering its substantial and direct relevance to the gas industry. To this end, discussion is made to cover polymeric gas permeation membranes; CO 2 -selective facilitated transport membranes, hollow fiber gas–liquid membrane contactors, inorganic membranes and mixed matrix membranes. The market for CO 2 separation is currently dominated by polymeric membranes due to their relatively low manufacturing cost and processing ability into flat sheet and hollow fiber configurations as well as well-documented research studies. While there have been immensely successful membrane preparation and development techniques with consequential remarkable performance for each type of membrane. Each type of membrane brings associated advantages and drawbacks related to the characteristic transport mechanism for specific application conditions. Inorganic membranes, for example, are very suitable for high temperature CO 2 separation in excess of 400 °C while all other membranes can be applied at lower temperatures. The recent emergence of mixed matrix membranes has allowed the innovative approach to combine the advantages offered by inorganic and polymeric materials.

Mixed conducting membranes can be used for the separation of oxygen from air in both coal gasification and oxy-fuel power plants. In this review paper, the basic perovskite and non-perovskite structures, composition, properties and performance are addressed. Two typical perovskite materials, BSCF and LSCF, show promise in industrial applications as their oxygen fluxes are at least one order of magnitude higher than non-perovskite membranes. BSCF membranes are now delivering oxygen fluxes in excess of 5 ml min−1 cm−2. Latest developments in perovskite composition, effects of impurities in membrane performance and membrane geometry are discussed giving an insight into the potential utilisation in clean energy delivery processes. Strategies for improving membranes performance using unit operations with different geometries and possible future technologies are also addressed.

AbstractGraphene, a one‐atom‐layer‐thick carbon‐structured material, has attracted global research attention due to its unique two‐dimensional structure, high electrical conductivity, superior electron‐transfer properties and charge‐carrier charge‐carrier mobility, large specific surface area, high transparency, and good mechanical properties. After its successful isolation into the free standing form in 2004, various graphene nanostructures have been developed and incorporated as key components in supercapacitors, lithium‐ion batteries, solar cells, and fuel cells; the energy supporting devices which hold the key role to sustain our energy demand well into the future. Herein, we summarized the recent progress and performance of these graphene–nanostructure‐based devices.This article is categorized under: Energy Infrastructure > Science and Materials Energy and Development > Science and Materials Energy Research & Innovation > Science and Materials

Abstract The separation and reattachment flow occurs in a backward-facing step (BFS) is available in various industrial applications such as gas turbine engines, combustors, aircraft, buildings and many other devices of heat transfer. It represents the pillar key of determining the flow structure and significantly affecting the heat transfer mechanism. This work studies numerically the effects of four various types of blockage shapes on transient laminar mixed convective nanofluid flow over a horizontal BFS placed in a duct. Nanoparticles of SiO2 with ethylene glycol as a base fluid at 2% of volume fraction and 20 nm of nanoparticle diameter are considered to examine the effect of different blockage shape on the thermal and flow fields at different time scales. The downstream of the step is kept at a constant heat flux of 500 W/m2, while other walls and sides of the duct are considered thermally insulated. The Reynolds number used in this study is in the range of 50–200. The relevant governing equations (continuity, momentum and energy) along with the boundary conditions are solved with the aid of finite volume method (FVM). The results reveal that after dimensionless time of τ = 5 the trend of nanofluid flow and recirculation area near the step and behind the blockage shape does not change significantly and this time is selected as a quasi-steady state time and the point of comparison. The velocity distributions for front facing triangular blockage decreased and this blockage shape has the highest value of skin friction coefficient beyond Re = 150. The results indicate that the front facing triangular blockage has the highest value of average Nusselt number and performance evaluation index while the trapezoidal blockage has the lowest value

A beancurd-derived mesoporous carbon (NSC) was prepared by an environmentally friendly procedure, and then it was investigated as Au@Pd@Pt core-shell catalysts support (Au@Pd@Pt-NSC) for oxygen reduction reaction (ORR). The Au@Pd@Pt-NSC (E1/2 = 0.91 V) has a marginally negative ORR half-wave potential compared with other materials, in particular Pt/C (E1/2 = 0.87 V) and Au@Pd@Pt-C (E1/2 = 0.81 V). The specific and mass activities of the Au@Pd@Pt-NSC were 5 and 13 times higher than the commercial a Pt/C catalyst. After 20000 cycles of rapid durability test, the Au@Pd@Pt-NSC sample showed a loss of just 4.9% compared with the initial ECSA area, which can be attributed to the favorable interaction between Au@Pd@Pt and NSC. These results can be considered of environmental relevance and high potential applicability.

This review examines the latest research on the design and engineering of nanoreactors for application in metal–chalcogen batteries.