Miaohong Su¹, Haiying Dong^1,2,*, Kaiqi Liu¹, Weiwei Zou¹

Energy Engineering, Vol.117, No.6, pp. 439-452, 2020, DOI:10.32604/EE.2020.011805

Abstract A subsynchronous oscillation suppression strategy based on self-adaptive auto disturbance rejection proportional integral controller is proposed for doublyfed induction generator-based wind farm integrated into grid through voltage source converter based multi-terminal direct current. In this strategy, the nonlinear PI controller is constructed by fal function to replace the traditional linear PI controller, and then the tracking differentiator is used to arrange the appropriate transition process in combination with the idea of active disturbance rejection control, and the self-adaptive auto disturbance rejection proportional integral controller is designed. By applying the controller to the inner loop of the converter on the rotor… More >

Yunxiang Guo¹, Cheng Lu^1,2, Feng Yu¹, Liang Hua¹, Xinsong Zhang^1,*

Energy Engineering, Vol.117, No.6, pp. 429-438, 2020, DOI:10.32604/EE.2020.011673

Abstract Nanocrystalline core is often adopted in high-power medium-frequency transformer, whose excitation voltage is usually a rectangular wave with an adjustable duty ratio. In this paper, several kinds of methods are proposed for core loss calculation under non-sinusoidal voltage excitation by modifying the original Steinmetz equation (OSE). Firstly, these correction methods are compared in theory, and their analytical equations under rectangular voltage with an adjustable duty ratio are deduced. Then, a hysteresis loop measurement system is established to measure the core loss density of a nanocrystalline core. Based on the measured results of the core loss density under sinusoidal voltage excitation,… More >

Yuhao Jia¹, Bin Cheng^1,2,*, Xiyang Li^1,2, Hui Zhang^1,2, Yinglong Dong¹

Energy Engineering, Vol.117, No.6, pp. 413-427, 2020, DOI:10.32604/EE.2020.012019

Abstract In order to study the effect of icing on the wind turbine blade tip speed ratio and wind energy utilization coefficient under working conditions, it is important to better understand the growth characteristics of wind turbine blade icing under natural conditions. In this paper, the icing test of the NACA4412 airfoil wind turbine was carried out using the natural low temperature wind turbine icing test system. An evaluation model of icing degree was established, and the influence of wind speed and icing degree on the performance parameters of wind turbines was compared and analyzed. It is shown that icing is… More >

Abdelsalam Aldawoud^*, Fatma Elzahraa Hosny, Rasha Mdkhana

Energy Engineering, Vol.117, No.6, pp. 381-395, 2020, DOI:10.32604/EE.2020.011863

Abstract The opportunities for energy savings by retrofitting of the existing school buildings in the United Arab Emirates (UAE) are significant because of their excessive energy consumption and space cooling demand. In this research, energy modeling and simulation are utilized with the use of Design Builder software to examine the influence of various retrofitting measures of air-conditioning (A/C) system and building envelope components on the energy use. Several combined measures are implemented and assessed to achieve the main goal of this research of selecting the best course of action to reduce cooling energy consumption for existing school buildings in the UAE.… More >

Asaad H. Sayer¹, Hameed B. Mahood^2,*

Energy Engineering, Vol.117, No.6, pp. 367-379, 2020, DOI:10.32604/EE.2020.011156

Abstract Salinity gradient solar ponds (SGSPs) provide a tremendous way to collect and store solar radiation as thermal energy, and can help meet the critical need for sustainable ways of producing fresh water. However, surface evaporation results in the loss of both water and heat. This study therefore theoretically investigates the effect on temperatures within an SGSP when its surface is covered with a layer of air encased in a nylon bag. An earlier SGSP model was slightly modified to add the air layer and to estimate the temperature distributions of the upper layer or the upper convective zone (UCZ) and… More >

D. Menaga¹, M. Premkumar², R. Sowmya^1,*, S. Narasimman³

Energy Engineering, Vol.117, No.6, pp. 481-495, 2020, DOI:10.32604/EE.2020.013282

Abstract The proposed controller accompanies with different sliding surfaces. To understand maximum power point extraction as opposed to nonlinear uncertainties and unknown disturbance of a grid-connected photovoltaic system to various control inputs (u_d, u_q) is designed. To extract maximum power from a solar array and maintain unity power flow in a grid by controlling the voltage across the dclink capacitor (V_pvdc) and reactive current (i_q). A multiple input-output with multiple uncertainty constraints have considered designing proposed sliding mode controllers to validated their robustness performance. An innovative controller verifies uncertain inputs, constant and changes in irradiances, and temperature of the photo-voltaic system.… More >

Tanzhong Fu^1,2,3, Yu Xue^1,*, Tancai Xia¹, Wang Jing¹, De Gejirifu¹

Energy Engineering, Vol.117, No.6, pp. 397-411, 2020, DOI:10.32604/EE.2020.011633

Abstract To further study the impact of renewable energy penetration on the technical transformation of distribution networks. Based on the output power characteristics of wind power and photovoltaics, a renewable energy grid-connected capacity model and a distribution network full cost-benefit model were constructed. Based on this, to maximize the comprehensive income of the distribution network and the renewable energy penetration rate, to establish the technical reform optimization model and search for the optimal solution through the improved NSGA-II algorithm. Finally, the effectiveness of the proposed model was verified by setting up three scenarios of simultaneous wind power, grid-connected wind power, grid-connected… More >

Shafiqur Rehman¹, Umar T. Salman^2,*, Luai M. Alhems¹

Energy Engineering, Vol.117, No.6, pp. 343-365, 2020, DOI:10.32604/EE.2020.011471

Abstract Renewable energy has received much attention in the last few decades and more investment is being attracted across the world to boost its contribution towards the existing energy mix. In the Kingdom of Saudi Arabia (KSA), many studies have been conducted on the potential of renewable energy sources (RES), such as wind, solar, and geothermal. Many of these studies have revealed that the Kingdom is blessed with an abundance of RES with wind energy being the best after solar. This paper presents an analysis of windfarm distributed generation (WFDG) for energy management strategy in the Eastern Province of KSA. The… More >

Louis Francois Marie^1,*, Sunkara Prudhvi Raj², Policherla Venkata Sai³, Tara MacLeod¹, Morapakala Srinivas², K. Srinivas Reddy³, Tadhg Seán O’Donovan⁴

Energy Engineering, Vol.117, No.5, pp. 323-342, 2020, DOI:10.32604/EE.2020.011035

Abstract Non-centrifugal cane sugar (NCS), known as Jaggery, is a form of unre- fined sugar which contains molasses. The integration of renewable energy resources in the production of NCS, have been analysed. The work investigates the energy requirements of a system incorporating a freeze-concentrator and a solar thermal heater to reduce the reliance on the combustion of bagasse or other fuels in a Jaggery production process. Depending on the extent to which freeze concentration can be incorporated into the process, results show that the minimum theoretical energy required to produce Jaggery can be reduced by 91.30% overall. Although difficult in practice,… More >

Shusheng Xiong¹, Defeng Xuan², Yonggen Zhang², Zhankuan Wu¹, Wei Li^1,*, Zhaohan Hu¹, Jing Xu¹

Energy Engineering, Vol.117, No.5, pp. 315-322, 2020, DOI:10.32604/EE.2020.011975

Abstract This research studied catalytic reforming mechanism of low concentration alcohol, analyzed the producing conditions and influencing factors of a mixture of combustible gas, took an analysis towards the composition of the mixture produced by reforming, and studied the respective effects of temperature, traffic, alcohol concentration and catalyst on the components of mixed gas. It is found that, under different working conditions of the engine, the external condition of the reforming reaction changes, and the composition of the reforming gas will differ as well. As a result, the optimum air-fuel ratio of the engine must at the same time adapt to… More >