Huan Ma¹, Linlin Ma², Zengwei Wang^3,*, Zhendong Li³, Yuanzhen Zhu¹, Yutian Liu³

Energy Engineering, Vol.121, No.11, pp. 3133-3160, 2024, DOI:10.32604/ee.2024.055051 - 21 October 2024

Abstract With the increasing penetration of renewable energy in power system, renewable energy power ramp events (REPREs), dominated by wind power and photovoltaic power, pose significant threats to the secure and stable operation of power systems. This paper presents an early warning method for REPREs based on long short-term memory (LSTM) network and fuzzy logic. First, the warning levels of REPREs are defined by assessing the control costs of various power control measures. Then, the next 4-h power support capability of external grid is estimated by a tie line power prediction model, which is constructed based More > Graphic Abstract

Weigang Jin¹, Lei Chen^2,*, Shencong Zheng², Yuqi Jiang², Yifei Li², Hongkun Chen²

Energy Engineering, Vol.121, No.11, pp. 3161-3179, 2024, DOI:10.32604/ee.2024.054068 - 21 October 2024

Abstract Investigating flexibility and stability boosting transmission expansion planning (TEP) methods can increase the renewable energy (RE) consumption of the power systems. In this study, we propose a bi-level TEP method for voltage-source-converter-based direct current (VSC-DC), focusing on flexibility and stability enhancement. First, we established the TEP framework of VSC-DC, by introducing the evaluation indices to quantify the power system flexibility and stability. Subsequently, we propose a bi-level VSC-DC TEP model: the upper-level model acquires the optimal VSC-DC planning scheme by using the improved moth flame optimization (IMFO) algorithm, and the lower-level model evaluates the flexibility More >

Chunxue Wen, Yaoquan Wei^*, Peng Wang, Jianlin Li, Jinghua Zhou, Qingyun Li

Energy Engineering, Vol.121, No.11, pp. 3241-3261, 2024, DOI:10.32604/ee.2024.051810 - 21 October 2024

Abstract A modular system of cascaded converters based on model predictive control (MPC) is proposed to meet the application requirements of multiple voltage levels and electrical isolation in renewable energy generation systems. The system consists of a Buck/Boost + CLLLC cascaded converter as a submodule, which is combined in series and parallel on the input and output sides to achieve direct-current (DC) voltage transformation, bidirectional energy flow, and electrical isolation. The CLLLC converter operates in DC transformer mode in the submodule, while the Buck/Boost converter participates in voltage regulation. This article establishes a suitable mathematical model More >

Samar El-Mekkawi¹, Wafaa Abou-Elseoud², Shaimaa Fadel², Enas Hassan², Mohammad Hassan^2,*

Journal of Renewable Materials, Vol.12, No.9, pp. 1573-1591, 2024, DOI:10.32604/jrm.2024.053589 - 25 September 2024

Abstract Recycling of paper sludge waste is crucial for establishing a sustainable green industry. This waste contains valuable sugars that can be converted into important chemicals such as ethanol, poly hydroxybutyrate, and lactic acid. However, the main challenge in obtaining sugars in high yield from paper sludge is the high crystallinity of cellulose, which hinders hydrolysis. To address this, pretreatment using phosphoric acid was optimized using response surface methodology to facilitate cellulose hydrolysis with minimal energy and chemicals. The created prediction model using the response surface method considered factors such as acid concentration (ranging from 60%… More > Graphic Abstract

Ananda S. Amarasekara^1,2,*, Gabriel Murillo Morales^1,2, Raghava R. Kommalapati^2,3

Journal of Renewable Materials, Vol.12, No.9, pp. 1495-1506, 2024, DOI:10.32604/jrm.2024.052373 - 25 September 2024

Abstract Renewable resources based polymers provides a sustainable alternative to petroleum derived polymeric materials. As a part of our series on synthesis of vanillin based renewable polymers, we report the synthesis of poly(hydrovanilloin-furfural) [poly(HVL-Fur)] and poly(hydrovanilloin–5-hydromethylfurfural) [poly(HVL-5-HMF)]. Vanillin was dimerized to a mixtures of meso/DL-hydrovanilloins with 94% meso product by electrochemical reductive coupling in aqueous sodium hydroxide using lead electrodes in quantitative yield. Then sodium hydroxide catalyzed condensation of hydrovanilloin with furfural in water at 80°C for 72 h was used to synthesize poly(HVL-Fur) with Mw = 8600 g mol⁻¹, PDI = 1.28 in 78% yield. Similarly, condensation of hydrovanilloin More > Graphic Abstract

Saif Serag^1,*, Adil Echchelh², Biagio Morrone¹

Energy Engineering, Vol.121, No.10, pp. 2719-2741, 2024, DOI:10.32604/ee.2024.054424 - 11 September 2024

Abstract Renewable energy sources are essential for mitigating the greenhouse effect and supplying energy to resource-scarce regions. However, their intermittent nature necessitates efficient storage solutions to enhance system efficiency and manage energy costs. This paper investigates renewable and clean storage systems, specifically examining the storage of electricity generated from renewable sources using hydropower plants and hydrogen, both of which are highly efficient and promising for future energy production and storage. The study utilizes extensive literature data to analyze the impact of various parameters on the cost per kWh of electricity production in hybrid renewable systems incorporating… More > Graphic Abstract

Ganesh There^*, Rohit Sharma^*

Energy Engineering, Vol.121, No.10, pp. 2851-2892, 2024, DOI:10.32604/ee.2024.049506 - 11 September 2024

Abstract This analysis investigates the widespread use of solar drying methods and designs in developing countries, particularly for agricultural products like fruits, vegetables, and bee pollen. Traditional techniques like hot air oven drying and open sun drying have drawbacks, including nutrient loss and exposure to harmful particles. Solar and thermal drying are viewed as sustainable solutions because they rely on renewable resources. The article highlights the advantages of solar drying, including waste reduction, increased productivity, and improved pricing. It is also cost-effective and energy-efficient. The review study provides an overview of different solar drying systems and… More > Graphic Abstract

Mohammed Mohammed^1,2,*, Jawad K. Oleiwi³, Aeshah M. Mohammed⁴, Anwar Ja’afar Mohamad Jawad⁵, Azlin F. Osman^1,2, Tijjani Adam⁶, Bashir O. Betar⁷, Subash C. B. Gopinath^2,8,9

Journal of Renewable Materials, Vol.12, No.7, pp. 1237-1290, 2024, DOI:10.32604/jrm.2024.051201 - 21 August 2024

Abstract Natural fibre (NFR) reinforced functional polymer composites are quickly becoming an indispensable sustainable material in the transportation industry because of their lightweight, lower cost in manufacture, and adaptability to a wide variety of goods. However, the major difficulties of using these fibres are their existing poor dimensional stability and the extreme hydrophilicity. In assessing the mechanical properties (MP) of composites, the interfacial bonding (IB) happening between the NFR and the polymer matrix (PM) plays an incredibly significant role. When compared to NFR/synthetic fibre hybrid composites, hybrid composites (HC) made up of two separate NFR are… More > Graphic Abstract

Wentao Li¹, Jiantao Liu², Yudun Li³, Guoxin Ming¹, Kaifeng Zhang¹, Kun Yuan^1,*

Energy Engineering, Vol.121, No.9, pp. 2479-2503, 2024, DOI:10.32604/ee.2024.050852 - 19 August 2024

Abstract With the large-scale development and utilization of renewable energy, industrial flexible loads, as a kind of load-side resource with strong regulation ability, provide new opportunities for the research on renewable energy consumption problem in power systems. This paper proposes a two-layer active power optimization model based on industrial flexible loads for power grid partitioning, aiming at improving the line over-limit problem caused by renewable energy consumption in power grids with high proportion of renewable energy, and achieving the safe, stable and economical operation of power grids. Firstly, according to the evaluation index of renewable energy… More >

Kaicheng Liu^1,3, Chen Liang², Naiyue Wu^1,3, Xiaoyang Dong², Hui Yu^1,*

Energy Engineering, Vol.121, No.9, pp. 2621-2637, 2024, DOI:10.32604/ee.2024.050001 - 19 August 2024

Abstract This paper presents a novel approach to economic dispatch in smart grids equipped with diverse energy devices. This method integrates features including photovoltaic (PV) systems, energy storage coupling, varied energy roles, and energy supply and demand dynamics. The system model is developed by considering energy devices as versatile units capable of fulfilling various functionalities and playing multiple roles simultaneously. To strike a balance between optimality and feasibility, renewable energy resources are modeled with considerations for forecasting errors, Gaussian distribution, and penalty factors. Furthermore, this study introduces a distributed event-triggered surplus algorithm designed to address the More >