Abstract

Using conventional processes, biodiesel production is necessarily accompanied by the use of excess alcohol and production of a low value glycerol-rich co-product. There is currently a substantial worldwide surplus of this coproduct. While recovery of the alcohol is associated with high capital cost and energy requirement. This work tend to reduce the alcohol usage during biodiesel production and in situ convert the crude glycerol to an added valued product. The biodiesel was produced batch-wise at 130 – 160 oC with sulfuric acid as the catalyst. The effects of reaction temperature, catalyst concentration and molar ratio of triglyceride to methanol were studied. Approximately 100% conversion of the triglyceride was achieved. The glycerol conversion increased with increasing temperature and decreasing molar ratio. This represents proof-of-concept not only for reducing the excess methanol requirement, but also for combining production of fatty acid methyl esters with other added value products, whilst reducing glycerol production.

Abstract

Sustainable aviation fuels (SAFs) can play a crucial role in reducing the aviation industry’s carbon footprint. Unlike conventional jet fuel production, SAFs could be produced via a combination of chemical processes and feedstocks. However, current studies have primarily focused on the techno-economic analysis of a single conversion pathway (chemical process plus feedstock), there is a lack of study on multi-criteria evaluations of multiple conversion pathways simultaneously. In this paper, a survey instrument is developed in which 106 experts participated in evaluating thirty-eight performance criteria across six production technologies or conversion pathways along the SAF supply chain. A generic value tree is thus obtained. The recommendations of this work are to be utilized as a foundation for stakeholder assessment of SAF planning.

Abstract

The growing global population and the resulting excess use of fossil fuels have brought the urgency for climate change mitigation leading to focus on renewable energy resources. Biomass is one of the earliest natural sources of energy, which has the potential to substitute for primary energy resource. However, commercial production of biofuel is still constrained by uncertainties such as biofuel demand. In this study, a two-stage stochastic mixed integer linear programing is formulated for biofuel supply chain based on macroalgae resource under uncertainties. The objective function in this formulation is total annual cost to be minimized. The approach is illustrated through a bioethanol supply chain case study in Korea, where macroalgae are among the dominant biomass resources.

Abstract

The rapid development of modern electronic devices urges an increasing need for better heat transfer techniques. Pool boiling heat transfer has great potential as it can provide high heat transfer capacity during the phase change of the working fluid. With the help of additive manufacturing technology, complex designs of pool boiling heat sinks can be achieved with selective laser melting (SLM) and they have shown great performances. In this study, heat sinks with one-layer and two-layer porous fin arrays are manufactured by SLM method using AlSi12 alloy powders and heat treated at 450℃ in nitrogen. Their pool boiling performances have shown great enhancement compared with plain copper heat sinks and the heat treated heat sinks have shown the best result both in heat transfer coefficient (HTC) and critical heat flux (CHF). The visualization data is collected during the experiments and used to analyze the heat transfer mechanism.

Abstract

In this paper, an AC/DC hybrid microgrid with PET is firstly modeled, and then a two-layer optimization model is established with the objective of minimizing the operating cost of AC/DC hybrid microgrid. Finally, the above two-layer optimization model is converted to a single-layer optimization model through KKT method for solving. According to the analysis of the case, the scheduling method based on two-layer optimization considers the cost of purchasing the PET in the upper layer and the operating cost of the different microgrids in the lower layer, and realizes the flexible scheduling between the main grid and microgrids through PET. Compared with the AC/DC hybrid microgrid with AC/DC converter, the hybrid microgrid with PET has flexible power regulation characteristics, and has advantages in reducing operating costs, fully absorbing and efficiently utilizing the renewable energy.

Abstract

The hybrid wind-based pumped hydro storage system that absorbs the wind curtailment due to grid limitations is considered to be a solution to improve wind energy penetration and the cost-effectiveness of wind farms. An offshore wind-pumped hydro storage hybrid power system connected to thermal supplied main grid is proposed in this paper. The contribution of this paper can be summarized as follows: (1) a multi-objective dynamic economic optimization model for the proposed system based on evolutionary algorithms is established to optimize size for offshore wind-based pumped hydro storage system; (2) design parameters include the capacity of pump, turbine and reservoirs, and the key financial parameters such as wind power feed-in tariff and capacitor price of pumped hydro storage power station are also taken into account; and (3) examine the attainability of various objectives to analyze the influence on the operation and economic effectiveness. The results show that the optimizing size study is importance to test the economic feasibility of the system. The case study presented in this paper provides decision makers with the flexibility to choose the appropriate capacity installation under different expectations.

Abstract

With the large-scale penetration of electric vehicles, the research on the influence factors of energy consumption of electric vehicles has become an important requirement for the estimation of energy efficiency, energy-saving route planning and the optimal design of power system structure. In this paper, the real-world driving data of 59 electric taxis in Beijing are obtained and divided into three-level driving fragments. The influence factors of energy consumption, including vehicle-related factors (velocity, acceleration and kinematic states), environment-related factors (ambient temperature and traffic condition) as well as driver-related factors are extracted and studied. Results show that the energy consumption of electric vehicle is significantly influenced by velocity, acceleration and kinematic states. Benefit from the energy-saving at idling state and the braking energy regeneration technology, traffic congestion has a slighter influence on energy consumption. Besides, the appropriate ambient temperature around 19.5℃ and moderate driving pattern can help reduce energy consumption to a certain extent. This work builds an essential foundation for accurate estimation and prediction of energy consumption of electric vehicles.

Abstract

The physico-chemical structure of co-pyrolysis char significantly affects its gasification reactivity. Pore distribution and microcrystal structure of co-pyrolysis char from polyvinyl chloride (PVC) and bituminous coal were investigated by specific surface area analyzer and X-ray diffraction. Based on fractal theory and deconvolution method, the influence of PVC on copyrolysis char structure was analyzed quantitatively. The results showed that the specific surface area of copyrolysis char increased slightly compared with PVC char. Similar to the PVC char, the pore size distribution of copyrolysis char was wide and uniform. The ordering of carbon microcrystal structure of co-pyrolysis char was promoted by the addition of PVC. This study can provide basic data for exploring the relationship between gasification characteristics and structure parameters of co-pyrolysis char.

Abstract

Resilience of power systems has received more and more attention in recent years. In this paper, considering the switching operation time of sectionalizing switches and limited maintenance resources, we propose a multi-stage reconfiguration method for the enhancement of distribution system resilience, where, the preventative network reconfiguration before extreme events is considered to improve load survivability and the network reconfiguration in each stage after extreme events is considered for load restoration. The model is formulated as a MILP problem. Case studies on the IEEE 33-bus system show the effectiveness of the proposed method.

Abstract

Promoting clean heating in winter in the northern region is related to the warmth of the masses in the northern region and whether fog and haze can be reduced. On the basis of summarizing the current situation of heating in rural areas of northern China, this paper expounds the practical problems and basic needs of clean heating. Taking Shandong as the research object, this paper studies the applicability of different modes of clean heating technology in rural areas of North China.The author calculates the heat load demand during heating period, screens the suitable clean heating technology in Shandong area, and obtains the suitable technical path and application mode for rural clean heating in Shandong area.The technical feasibility, economic feasibility and environmental impact of different modes of clean heating, such as solar heating, gas heating and biomass pyrolysis multi-generation heating, are analyzed. The results show that under the existing economic and technological conditions, biomass pyrolysis polygeneration is suitable for clean heating in rural areas of Shandong Province, especially for demonstration and promotion of small centralized or decentralized heating in natural villages or new rural communities. This study provides a new way to solve the problem of clean heating in rural areas of northern China.