Sizing of Energy Storage Systems for Output Smoothing of Renewable Energy Systems

光伏、风力发电等可再生能源（renewable energysources，RESs）具有随机性、间歇性等特点。为了抑制RESs输出波动对电网的不利影响，提出了用于平滑RESs发电系统功率输出的储能系统（energy storage system，ESS）容量优化确定方法。利用离散傅里叶变换（discrete Fouriertransform，DFT）对RESs输出功率进行频谱分析，基于频谱分析结果，考虑ESS充放电效率、荷电状态（stateofcharge，soc）及RESs发电系统目标功率输出波动率的约束，确定所需ESS最小容量。采用美国华盛顿州实际观测风速数据及日本东北电力公司风电场接入电网20rnin有功功率波动规范（最大波动率为10％），在一风力发电系统中对该方法进行了验证。算例结果表明采用该方法能够以较小的容量将风机输出最大波动率由61．7％降到9．9％。

Dynamic design of a nonlinear energy sink with NiTiNOL-steel wire ropes based on nonlinear output frequency response functions

A novel vibration isolation device called the nonlinear energy sink(NES)with NiTiNOL-steel wire ropes(NiTi-ST)is applied to a whole-spacecraft system.The NiTi-ST is used to describe the damping of the NES,which is coupled with the modified Bouc-Wen model of hysteresis.The NES with NiTi-ST vibration reduction principle uses the irreversibility of targeted energy transfer(TET)to concentrate the energy locally on the nonlinear oscillator,and then dissipates it through damping in the NES with NiTi-ST.The generalized vibration transmissibility,obtained by the root mean square treatment of the harmonic response of the nonlinear output frequency response functions(NOFRFs),is first used as the evaluation index to analyze the whole-spacecraft system in the future.An optimization analysis of the impact of system responses is performed using different parameters of NES with NiTi-ST based on the transmissibility of NOFRFs.Finally,the effects of vibration suppression by varying the parameters of NiTi-ST are analyzed from the perspective of energy absorption.The results indicate that NES with NiTi-ST can reduce excessive vibration of the whole-spacecraft system,without changing its natural frequency.Moreover,the NES with NiTi-ST can be directly used in practical engineering applications.

Analysis on Output Power for Multi-direction Piezoelectric Vibration Energy Harvester

To predict the performance of multi-direction piezoelectric vibration energy harvester,an equation for calculating its output power is obtained based on elastic mechanics theory and piezoelectricity theory.Experiments are performed to verify theoretical analysis.When the excitation direction is along Y direction,a maximal output power about 0.139 mW can be harvested at a resistive load of 65kΩ and an excitation frequency of 136 Hz.Theoretical analysis agrees well with experimental results.Furthermore,the performance of multi-direction vibration energy harvester is experimentally tested.The results show that the multi-direction vibration energy harvester can harvest perfect energy as the excitation direction changes in XY plane,YZ plane,XZ plane and body diagonal plane of the harvester.

The Influences of Energy Price Variation on the Prices of Other Industries: A Study Based on Input-Output Price Model

Energy has laid material foundation for human society during its development. Meanwhile, any change of price in the energy industry may influence social production and people’s life at all levels via an input-output mechanism under which the change related to energy is surely transmitted to other industries. The price change thus incurred in all industries may adversely affect the realization of macroeconomic objective-maintaining prices at a stable level. It is, therefore, needed to conduct an empirical research related to the impact of price change in energy industry on that in other industries. According to the data coming from “China’s 2015 Input-Output Extension Table (42 Departments)” and four hypothetical basis, this article focuses on four energy sectors and analyzes how deeply the price change of them, by use of input-output model, affects that of other industrial products under five conditions where each of their price rises by 10% individually or simultaneously, and why such an influence occurs. The results show that the price rising of the energies in question leads to an upward growth in the prices of other industrial products, especially when their prices go up simultaneously. Besides, the price increase in the four energy sectors doesn’t influence other industries in an accumulation form but actually leads to a rollback in some of other industries. It is recommended to adopt diversified pricing strategies for different energy products, thus maximizing the value of each specific energy, and meanwhile achieving the goals of energy consumption reduction and price equilibrium.

Improved Blind Multiuser Detection Algorithm Based on Minimum Output Energy

Based on minimum output energy,an improved blind multiuser detection algorithm is proposed by the use of Hopfield neural network.Compared with traditional algorithms,the proposed algorithm does not need the circuit for constraints.The resources are greatly saved and the complexity is reduced as well.The simulation results show that the performance of the improved algorithm is similar to that of the optimal multiuser detection algorithm which is not suitable for the mobile station.Compared with the traditional gradient blind multiuser detection algorithm,the convergence speed of the improved algorithm is quickened.

Assessing Asian Economies Renewable Energy Consumption Efficiency Using DEA with Undesirable Output

Along with vast non-fossil potential and significant expertise,there is a question of whether Asian nations are attaining efficient consumption and exploitation of renewable resources.From this perspective,the paper aims to evaluate the efficiency of 14 potential Asia countries in renewable energy consumption during the six-year periods(2014-2019).In analyzing the performance of the renewable energy sector,the data envelopment analysis(DEA)with an undesirable output model approach has been widely utilized to measure the efficiency of peer units compared with the best practice frontier.We consider four inputs and two outputs to a DEA-based efficiency model.Labor force,total energy consumption,share of renewable energy,and total renewable energy capacity are inputs.The outputs consist of CO_(2)emissions as an undesirable output and gross domestic product as a desirable output.The results show that United Arab Emirates,Saudi Arabia,Japan,and South Korea consistently outperform in the evaluation,achieving perfect efficiency scores during the research period.Uzbekistan is found to have the lowest average efficiency of renewable energy utilization.

Embodied Energy and CO2 Associated with Buildings by Using Input and Output Table in Japan

In July 2009, the 2005 basic Japanese input/output table was publicized together with its physical transaction table. This research paper analyzed the 2005 IO （input/output） table to create building industry-related intensities and, at the same time, compared the building industry with industries at large for distribution margins and transportation. The analysis of distribution margins separately for middle and purchaser margins found that middle margins in the building industry are minor at 35% of the averages for all industries, while purchaser margins are sizable at 1.8 times, proving that it is an industry for which local production for local consumption is quite effective. CO2 emissions resulting from transportation in the building industry were calculated and concisely characterized. Although the ratio of transportation CO2 emissions to total CO2 emissions in each industry finds almost no difference between general industries and the building industry, transportation CO2 emissions per production value are two to three times heavier than those from general industries to be justified as a transportation-intensive industry.

Energy Giant Expands Gas Output to Meet Growing Demand for Cleaner Fuel

China National Petroleum Corporation(CNPC),Asia’s biggest oil and gas producer,will increase its investment in natural gas exploration and production,pipeline construction and gas sales in the coming decade,betting big on the country’s thirst for the clean fuel.The stateowned company,which currently allocates 70

Research on Regulation Method of Energy Storage System Based on Multi-Stage Robust Optimization

To address the scheduling problem involving energy storage systems and uncertain energy,we propose a method based on multi-stage robust optimization.This approach aims to regulate the energy storage system by using a multi-stage robust optimal control method,which helps overcome the limitations of traditional methods in terms of time scale.The goal is to effectively utilize the energy storage power station system to address issues caused by unpredictable variations in environmental energy and fluctuating load throughout the day.To achieve this,a mathematical model is constructed to represent uncertain energy sources such as photovoltaic and wind power.The generalized Benders Decomposition method is then employed to solve the multi-stage objective optimization problem.By decomposing the problem into a series of sub-objectives,the system scale is effectively reduced,and the algorithm’s convergence ability is improved.Compared with other algorithms,the multi-stage robust optimization model has better economy and convergence ability and can be used to guide the power dispatching of uncertain energy and energy storage systems.

Robust Input-Output Energy Decoupling for Uncertain Singular Systems

This paper addresses the robust input-output energy decoupling problem for uncertain singular systems in which all parameter matrices except E exist as time-varying uncertainties. By means of linear matrix inequalities (LMIs), sufficient conditions are derived for the existence of linear state feedback and input transformation control laws, such that the resulting closed-loop uncertain singular system is generalized quadratically stable and the energy of every input controls mainly the energy of a corresponding output, and influences the energy of other outputs as weakly as possible. Keywords Uncertain singular systems - generalized quadratical stability - input-output energy decoupling - linear matrix inequality (LMI) Xin-Zhuang Dong graduated from the Institute of Information Engineering of People’s Liberation Army, China, in 1994. She received the M. S. degree from the Institute of Electronic Technology of People’s Liberation Army, in 1998 and the Ph.D. degree from Northeastern University, China, in 2004. She is currently a post-doctoral fellow at the Key Laboratory of Systems and Control, CAS.Her research interests include singular and nonlinear systems, especially the control of singular systems such as H ∞ control, passive control and dissipative control. Qing-Ling Zhang received the Ph.D. degree from Northeastern University, China, in 1995. He is currently a professor with the Institute of Systems Science, Northeastern University. His research interests include singular systems, fuzzy systems, decentralized control, and H 2/H ∞ control.

Wave Energy Study in China: Advancements and Perspectives

The history and current status of research and development of wave energy in the world is briefly introduced. The main problems existing in these studies are pointed out. The description is focused on the current status and the advancements achieved in China. After analysis of the wave energy resources and practical situations in China, it is pointed out that the studies on wave energy should be not only concentrated on the conversion efficiency and costs of wave energy devices, but also focused on the technology of independent operation and stable output of electricity. Finally, the perspectives of application of wave energy in China are discussed.

Nonlinear energy harvesting with dual resonant zones based on rotating system

An electromagnetic nonlinear energy harvester(NEH)based on a rotating system is proposed,of which the host system rotates at a constant speed and vibrates harmonically in the vertical direction.This kind of device exhibits several resonant phenomena due to the combinations of the rotating and the vibration frequencies of the host system as well as the cubic nonlinearity of the NEH.The governing equation of motion for the NEH is derived,and the dynamic responses and output power are investigated with the multiple scale method under the 1:1 primary and 2:1 superharmonic resonant conditions.The effects of system parameters including the nondimensional external frequency,the rotating speed,and the nonlinear stiffness on the responses of free vibration for the system are studied.The results of the primary resonance show that the responses exhibit not only the resonant characteristics but also the nonlinear dynamic characteristics such as the saddle-node(SN)bifurcation.The coexistence of multiple solutions and the varying trends of responses are verified with the direct numerical simulation.Moreover,the effects of system parameters on the average output power are investigated.The results of the analyses on the two resonant conditions indicate that the large power can be harvested in two resonant frequency bands.The effect of resonance on the output power is dominant for the 2:1 superharmonic resonance.Moreover,the results also show that introducing the nonlinearity can increase the value of the output power in large frequency bands and induce the occurence of new frequency bands to harvest the large power.The efficiency of the harvested power could be improved by the combined effects of the resonance as well as the nonlinearity of the NEH device.Suitable parameter conditions could help optimize the power harvesting in design.

Simulation of the Power Take-off System for a Heaving Buoy Wave Energy Converter

The heaving buoy wave energy device is popular for wave conditions with small wave heights and short periods. This paper presents the design of a wave energy converter composed of a gyro buoy, a hydraulic power take-off, and an electricity generation system. The energy accumulators are used to improve the output power with different control strategies. The quantity relations between each component are established using theoretical methods. The simulation model describes the energy conversion and calculates the operation time, energy capacity, and output power of the device under different initial pressures, release pressures, and electric resistances. As a result, the capacity is determined by the electronic load, and the maximum output power can be obtained when the accumulators are turned on and off at the same time. This study investigates the factors influencing the electric energy production and can be used to guide the optimization of this type of device.

Impact of Renewable Energy on Carbon Dioxide Emission Reduction in Bangladesh

Economic growth and industrialization often default to a great dependency on fossil fuels (FF) to supply power needs. The carbon rich nature of FF combustion can impact global warming. Therefore, it is conducive to transition from FF to renewable energy (RE). The present study aimed to address if replacement of a single FF by RE can mitigate carbon emissions. We conduct the study in a country undergoing mass urbanization and challenging energy demands. Data from energy resources in the Power & Energy Sector Master Plan (PSMP2016;Bangladesh) are analyzed over the 2017-2021 trajectory. Two scenarios for imports, oil and coal are assessed. Environmental input output (E-IO) analysis and percentage equivalence analysis measured data variables. The data is then further disaggregated into an emission reduction (ER) model with sensitivity analysis to measure carbon emission reduction when each FF source is substituted by RE. Results show the percentage share of energy generation capacity by both coal and RE increase over time. Solar and wind power contribute to the increase in RE. When oil is imported a 1% increase in oil, coal, and gas-based energy generation capacity increases carbon emissions by 1.25%, 1.48% and 0.93%, respectively. 1% increase in RE produces negligible carbon emissions (0.0042%). There was little difference in the percentages of carbon emissions when coal is imported. Substituting any FF with RE of equal energy capacity does not, in the short term, reduce carbon emissions in either scenario. Therefore, we conclude that for long term clean energy prospects in Bangladesh, RE needs to be developed to operate at greater capacity in conjunction with other carbon management factors. The research findings herein offer insights for clean energy implementation in developing nations.

A Nonlinear Control Algorithm for Flywheel Energy Storage Systems in Discharging Mode

针对Buck-Boost变换器的非线性特征给飞轮储能系统的放电运行状态带来的控制问题,提出了电压电流双环非线性控制算法。基于输入/输出线性化理论,推导出电流内环的控制律,并证明了内动态的稳定性。电压外环采用鲁棒性强的滑模变结构控制方法,并增加限流环节,保证放电电路安全、稳定运行。在Matlab/Simulink仿真平台中搭建飞轮放电模型,对所提出非线性控制算法进行了仿真验证。仿真结果表明,相比于双环PI控制,该算法能够明显改善输出电压调节时间、超调量等动态特性,在输入电压存在大范围变化的情况下,输出电压能够保持恒定和较低的纹波系数。

A process-level hierarchical structural decomposition analysis (SDA) of energy consumption in an integrated steel plant

A hierarchical structural decomposition analysis(SDA) model has been developed based on process-level input-output(I-O) tables to analyze the drivers of energy consumption changes in an integrated steel plant during 2011-2013. By combining the principle of hierarchical decomposition into D&L method, a hierarchical decomposition model for multilevel SDA is obtained. The developed hierarchical IO-SDA model would provide consistent results and need less computation effort compared with the traditional SDA model. The decomposition results of the steel plant suggest that the technology improvement and reduced steel final demand are two major reasons for declined total energy consumption. The technical improvements of blast furnaces, basic oxygen furnaces, the power plant and the by-products utilization level have contributed mostly in reducing energy consumption. A major retrofit of ancillary process units and solving fuel substitution problem in the sinter plant and blast furnace are important for further energy saving. Besides the empirical results, this work also discussed that why and how hierarchical SDA can be applied in a process-level decomposition analysis of aggregated indicators.

Energy efficiency and economic growth of China:1953-2006

Energy plays an important role in the economic life. With the rapid development of economy, the constraint of energy on the sustainable development of economy is becoming more and more obvious. This paper just Studies the factors influencing energy efficiency of China and the relationship between energy efficiency and China＇s economic： growth. By using time series multivariable linear regression methods with China＇s relevant data from 1953 to 2006, this paper constructs the regression model to analyze the factors that would impact energy, efficiency. After that, a regression model of China＇s real output to capital, labor and energy e lficiency is conducted to estimate the marginal contribution of every factor to the real output to prove the fundamental influence of energy efficiency to the economic growth. In the end, some policies and recommendations are also put forward in order to improve the energy efficiency; of China.

Optimization Study on Expansion Energy Used Air-Powered Vehicle with Pneumatic-Hydraulic Transmission

Pneumatic-hydraulic transmission has been developed for years. However, its dynamic properties are not good enough for application. In this paper, in order to increase the output characteristics, a late-model air-powered vehicle using expansion energy is proposed which can boost energy through a pneumatic-hydraulic transmission. The dynamic characteristics of the air-powered vehicle is modeled and verified by conducting experiment. In addition,the influence of the key parameters of the air-powered vehicle is researched for the optimization of the system performance. Through the results, the author got the conclusion that, firstly, comparison of the results of model and experiment proves the built model to be effective; secondly, input air pressure should be set according to the request of the practical loads, and range of 0.65 to 0.75 MPa can be chosen; thirdly, as a key structure parameter of the airpowered vehicle, ratio of the areas is considered to be set to approximate 8; what’s more, a bigger orifice with a limit will promote the system dynamic characteristic property, and the limit is about 3.5 mm; last but not the least, not too farther position of the rings will increase the quality of output dynamic characteristics. This paper can be a reference for system design of air-powered vehicle and dynamic improvement.

Modeling and Analysis of a Random Excited Double-Clamped Piezoelectric Energy Harvester

A double-clamped piezoelectric energy harvester subjected to random excitation is presented,for which corresponding analytical model is established to predict its output characteristics.With the presented theoretical natural frequency and equivalent stiffness of vibrator,the closed-form expressions of mean power and voltage acquired from the double-clamped piezoelectric energy harvester under random excitation are derived.Finally theoretical analysis is conducted for the output performance of the doubleclamped energy harvester with the change of spectrum density（SD）of acceleration,load resistance,piezoelectric coefficient and natural frequency value,which is found to closely agree with Monte Carlo simulation and experimental results.

An Improved Method of the Energy Loss Calculation Considering the Volatility of Wind Power Generation

The energy loss of the power grid is one of the key factors affecting the economic operation of power systems. How to calculate the electric energy consumption accurately will have a great influence on the planning, operation and management of the power grid. Currently there is a mountain of theoretical methods to calculate the line loss of the power system. However, these methods have some limitation, such as less considering the volatility of wind power resources. This paper presents an improved method to calculate the energy loss of wind power generation, considering the fluctuations of wind power generation. First, data are collected to obtain the curve of the typical daily expected output of wind farms for one month. Second, the curve of the typical daily expected output are corrected by the average electricity and the shape factor to obtain the curve of the typical daily equivalent output of wind farms for one month. Finally, the power flow is calculated by using typical daily equivalent output curve to describe the energy loss for one month. The results in the 110 kV main network show that the method is feasible.