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Abstract The demand for methanol will continue to increase since methanol is an attractive fuel for fuel cells in addition to being an intermediate raw material for hydrogen and dimethyl ether (DME), which are categorized as green energy sources. To produce methanol with a minimum amount of energy, it is necessary to investigate and reconsider a whole methanol synthesis process from energy saving point of view. Recently, we developed an innovative process design technology referred to as self-heat recuperation technology for saving energy. To apply this technology, whole-process heat is recirculated within the process without heat addition leading to large energy savings. In this paper, the feasibility of applying self-heat recuperation technology to the methanol synthesis process is investigated and an innovative process for methanol synthesis is developed from an energy saving point of view. The use of this self-heat recuperation technology in the methanol synthesis process greatly reduces the energy consumption.

Light weighting by material substitution is a key to reducing GHG emissions during vehicle operation. The GHG benefits are a salient factor in selecting lightweight materials for vehicles. Although the literature has performed lightweight material selections using GHG benefits under product- and fleet-based life-cycle inventory (LCI) analyses, recycling effects have therein been accounted for by arbitrarily selecting allocation methods for recycling, as the consensus on their selection is absent. Furthermore, studies have mistreated the temporal variations of the LCI parameters (the dynamic inventory (DI)), though that could be an important factor affecting the overall LCI results when allocation methods for recycling are in place. Therefore, to investigate their influence on greenhouse gas (GHG) benefit evaluations, an LCI case study was conducted, centered on aluminum- and magnesium-substituted internal combustion engine vehicles (ICEVs) at the product- and fleet- levels. “CO2 savings” and the “CO2 payback time”, as well as four allocation methods for recycling, were considered to represent the GHG benefits and address the recycling effects, respectively. The dynamic inventory was based on the world average electricity grid mix change. The results indicate that changing the conditions of the DI and the allocation methods for recycling could alter the better performing material under fleet-based analyses. Therefore, we ascertained that the choice of the allocation method for recycling and conducting fleet-scale dynamic LCI analyses in the presence of the DI is pivotal for material selections.

Abstract This paper presents a temporally coupled distributed online (TDO) algorithm to aggregate and coordinate numerous networked distributed energy resources (DERs) as a virtual power plant (VPP). A centralized stochastic optimization problem is formulated to minimize the long-term social utility loss while satisfying the voltage security, operational requirements of DERs, and VPP service requests. After that, we propose the TDO algorithm to reformulate the primary problem as an adaptation of online convex optimization (OCO). In particular, the temporally coupled constraints are well separated to each timeslot. In real-time operation, the VPP operator updates the incentives according to the measurement feedback. The smart energy gateways (SEGs) equipped at each node maximize their income and utility based on the received incentive signals through adjusting the setpoints of the governed photovoltaics (PV) inverters and electric vehicles (EVs). Unlike conventional distributed optimization algorithms where complicated iterative procedures between agents are unavoidable, the proposed TDO algorithm is computation- and communication-efficient since the SEG can directly employ the closed-form optimal setpoints without iterative communications once receiving the incentives. Furthermore, we design an incentive scheme to coordinate the SEGs based on the privacy protected nonintrusive measurements instead of direct control. Optimality and convergency of TDO are analyzed mathematically. Finally, the proposed method is corroborated numerically on a modified 33-node test feeder. A larger system is tested to validate the computational time performance.

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%.

Abstract Global environmental change is driven by food production. Biogas from food waste is a better source of clean energy. Ghana’s energy strategy targets a 10% increase in renewable energy and modern biomass in the national electricity generation mix. Studies on the assessment of electricity generation potential and economic feasibility of biogas to electricity projects in Ghana’s major cities are scarcely available. This study assesses the electricity generation potential of biogas from food waste through anaerobic digestion technology. The municipal solid waste generation potential of Accra and Kumasi was estimated from 2020 to 2039. The potential theoretical methane yield from food waste was calculated using Buswell’s equation. The study analyzed anaerobic digestion projects’ economic feasibility using the total life cycle cost, net present value, investment payback period, levelized cost of energy, and internal rate of return methods. A sensitivity analysis based on two scenarios (optimistic and pessimistic) was performed to analyze the influence of changes in the composition of food waste, per capita waste generation rate, population growth rate, per capita GDP growth rate, discount rate, capacity factor, electricity generation efficiency, waste collection efficiency, and methane production potential on the economic feasibility of the projects. The main findings indicate that the amount of waste generation in Accra during the project life cycle is 899,000 t/y to 3,359,000 t/y, while that of Kumasi is 915,000 t/y to 3,159,000 t/y. The power generation potential of the project in Accra ranges from 80.43 to 300.49 GWh/y, and in Kumasi ranges from 60.63 to 209.31 GWh/y. Economically, the project is feasible in Accra and Kumasi. The net present value of the project in Accra and Kumasi is $217,800,000 and $156,100,000. The sensitivity analysis shows that the project is infeasible in all the cities with a discount rate exceeding 20%. When the discount rate exceeds 20%, the project becomes highly infeasible in Accra compared to Kumasi. This study will offer itself as scientific guidance for investment in biogas to electricity projects in Ghana’s cities.

Abstract In this paper, the flame length (Lf), width (Wf), and volume (Vf) behaviors of the jet diffusion flame were experimentally and theoretically studied. Various fuel nozzle diameters (df), fuel jet velocities (uf), and air co-flow velocities (uco) were involved in the experiments to investigate their impacts on flame characteristics systematically. Additionally, the analytical solutions for the flow field, fuel concentration, Lf, Wf, and Vf of the jet diffusion flame were derived by theoretical analysis. The results show that flame shape and dimensions of the jet diffusion flame depended on fuel jet Reynolds number (Ref) inherently. At the laminar regime, the dimensionless flame length normalized by df (Lf*) was proportional to Ref. At the laminar–turbulent transitional regime and fully-turbulent regime, Lf* kept nearly constant. The dimensionless flame width (Wf*) remained basically unchanged at the laminar or fully-turbulent regime; but it increased fairly quickly with the increment in Ref at the laminar–turbulent transitional regime. The dimensionless flame volume (Vf*) increased linearly with Ref at the laminar regime, and parabolically with Ref at the laminar–turbulent transitional regime. At the fully-turbulent regime, Vf* kept constant. Besides, with the increase in uco, Lf* maintained nearly unchanged, and Wf* decreased exponentially. Based on the above behaviors, new forms of correlations for Lf*, Wf*, and Vf* of the jet diffusion flame were proposed presently. Comparisons of these correlations with the existing ones in the literature were also conducted in this paper. Moreover, Lf*, Wf*, and Vf* correlations for the dimethyl ether/air jet diffusion flames were developed herein.

Abstract Domestic wind turbine manufacturing sector in China has experienced development stages starting from scratch to mass production. During the 11th FYP period (2006–2010), the main goal of wind power policy in China is to promote the commercialization of wind power by large-scale deployment of wind farms. This goal has been realized to a great extent and now the cost of wind power generation is nearly comparable to coal-fired power generation in China. The industry policy, which devotes to mass production of domestic wind turbines, is also largely successful. The purpose of the paper is to provide an overview on wind turbine manufacturing sector in China. The policy evolution in different stages, achievements and challenges pertinent to the sector are addressed in the paper. Key findings are that the misleading industry policy, which provides strong incentive to blind entrance and “competition for scale and price” and restrains innovation as well, is the key obstacle for the sustainable development of the sector. Deficient technology standard and qualification system and the misplaced franchise bidding system also indulge vicious competition and oversupply. Creating a level playground for all turbine supplies, providing strong incentive to innovative manufacturers, establishing thorough and practicable standard and qualification system, and fine-tuning the directive of the franchise bidding system towards technology and service are the primary policy implications proposed by our study.

Space optoelectronic detectors present demand for the cryogenic environment that can operate stably and efficiently. Stirling, pulse tube and JT cryocoolers (SC, PTC and JTC) are capable of space applications, which have been verified and put into space use for many times. Shanghai Institute of Technical Physics, Chinese Academy of Science (SITP, CAS) has developed many space cryocoolers for decades. Multistage cryocoolers coupled by the Stirling technology, pulse tube technology and JT technology can satisfy the needs of the 2-30 K cryogenic enverionment in the space applications. This paper introduces the typical cryocoolers operating from 2 K to 30 K, which are important technologies and development tendency for the future space applications.

Abstract not Available.