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Records Added in October 2018
Records added in October 2018
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Showing records 51 to 75 of 99. [First] Page: 1 2 3 4 Last
Decomposing Industrial Energy-Related CO₂ Emissions in Yunnan Province, China: Switching to Low-Carbon Economic Growth
Mingxiang Deng, Wei Li, Yan Hu
October 23, 2018 (v1)
Subject: Energy Policy
Keywords: CO2 emissions, drivers, less-developed regions, low-carbon pilot, structural decomposition analysis, Yunnan province
As a less-developed province that has been chosen to be part of a low-carbon pilot project, Yunnan faces the challenge of maintaining rapid economic growth while reducing CO₂ emissions. Understanding the drivers behind CO₂ emission changes can help decouple economic growth from CO₂ emissions. However, previous studies on the drivers of CO₂ emissions in less-developed regions that focus on both production and final demand have been seldom conducted. In this study, a structural decomposition analysis-logarithmic mean Divisia index (SDA-LMDI) model was developed to find the drivers behind the CO₂ emission changes during 1997⁻2012 in Yunnan, based on times series energy consumption and input-output data. The results demonstrated that the sharp rise in exports of high-carbon products from the metal processing and electricity sectors increased CO₂ emissions, during 2002⁻2007. Although increased investments in the construction sector also increased CO₂ emissions, during 2007⁻2012, the carbon... [more]
Building Integrated Photovoltaics: A Concise Description of the Current State of the Art and Possible Research Pathways
Bjørn Petter Jelle
October 23, 2018 (v1)
Subject: Energy Policy
Keywords: building integrated photovoltaics (BIPV), research pathway, review, solar cell, state-of-the-art
Building integrated photovoltaics (BIPV) offer an aesthetical, economical and technical solution to integrate solar cells harvesting solar radiation to produce electricity within the climate envelopes of buildings. Photovoltaic (PV) cells may be mounted above or onto the existing or traditional roofing or wall systems. However, BIPV systems replace the outer building envelope skin, i.e., the climate screen, hence serving simultanously as both a climate screen and a power source generating electricity. Thus, BIPV may provide savings in materials and labor, in addition to reducing the electricity costs. Hence, for the BIPV products, in addition to specific requirements put on the solar cell technology, it is of major importance to have satisfactory or strict requirements of rain tightness and durability, where building physical issues like e.g., heat and moisture transport in the building envelope also have to be considered and accounted for. This work, from both a technological and scie... [more]
A Robust Weighted Combination Forecasting Method Based on Forecast Model Filtering and Adaptive Variable Weight Determination
Lianhui Li, Chunyang Mu, Shaohu Ding, Zheng Wang, Runyang Mo, Yongfeng Song
October 23, 2018 (v1)
Keywords: combination forecast, immune algorithm, load forecasting, Markov chain, normal cloud model, Particle Swarm Optimization, robustness
Medium-and-long-term load forecasting plays an important role in energy policy implementation and electric department investment decision. Aiming to improve the robustness and accuracy of annual electric load forecasting, a robust weighted combination load forecasting method based on forecast model filtering and adaptive variable weight determination is proposed. Similar years of selection is carried out based on the similarity between the history year and the forecast year. The forecast models are filtered to select the better ones according to their comprehensive validity degrees. To determine the adaptive variable weight of the selected forecast models, the disturbance variable is introduced into Immune Algorithm-Particle Swarm Optimization (IA-PSO) and the adaptive adjustable strategy of particle search speed is established. Based on the forecast model weight determined by improved IA-PSO, the weighted combination forecast of annual electric load is obtained. The given case study i... [more]
Review of the Thermo-Physical Properties and Performance Characteristics of a Refrigeration System Using Refrigerant-Based Nanofluids
Mahesh Suresh Patil, Sung Chul Kim, Jae-Hyeong Seo, Moo-Yeon Lee
October 23, 2018 (v1)
Subject: Materials
Keywords: nanofluid, nanolubricants, nanorefrigerants, performance, refrigeration systems
Nanofluids are considered a promising choice for several heat transfer applications. With the increasing awareness for energy saving and efficiency improvement in various thermal systems, including refrigeration systems, there is a growing interest in the refrigerant-based nanofluids owing to their superior thermo-physical properties. Nanorefrigerants are a class of nanofluid, which consist of suspended nanoparticles in a base refrigerant. In this paper, it is intended to include many articles on refrigeration systems that use nanorefrigerants, published in the period from 2005 to 2015. Although this is an extensive review, it could not include all the papers, and only some major research works were selected. It is believed that the dependency of thermal conductivity and other properties on temperature will make the thermal systems more efficient while operating at a high temperature. The literature reviews associated with the performance characteristics of nanorefrigerants in refriger... [more]
Noise Emission of a 200 kW Vertical Axis Wind Turbine
Erik Möllerström, Fredric Ottermo, Jonny Hylander, Hans Bernhoff
October 23, 2018 (v1)
Keywords: H-rotor, noise, noise emission, sound power level, vertical axis wind turbine (VAWT)
The noise emission from a vertical axis wind turbine (VAWT) has been investigated. A noise measurement campaign on a 200 kW straight-bladed VAWT has been conducted, and the result has been compared to a semi-empirical model for turbulent-boundary-layer trailing edge (TBL-TE) noise. The noise emission from the wind turbine was measured, at wind speed 8 m/s, 10 m above ground, to 96.2 dBA. At this wind speed, the turbine was stalling as it was run at a tip speed lower than optimal due to constructional constraints. The noise emission at a wind speed of 6 m/s, 10 m above ground was measured while operating at optimum tip speed and was found to be 94.1 dBA. A comparison with similar size horizontal axis wind turbines (HAWTs) indicates a noise emission at the absolute bottom of the range. Furthermore, it is clear from the analysis that the turbulent-boundary-layer trailing-edge noise, as modeled here, is much lower than the measured levels, which suggests that other mechanisms are likely to... [more]
Optimal Allocation of Thermal-Electric Decoupling Systems Based on the National Economy by an Improved Conjugate Gradient Method
Shuang Rong, Weixing Li, Zhimin Li, Yong Sun, Taiyi Zheng
October 23, 2018 (v1)
Subject: Energy Policy
Keywords: combine heat and power, improved parallel conjugate gradient, thermal-electric decoupling, wind power curtailment
Aiming to relieve the large amount of wind power curtailment during the heating period in the North China region, a thermal-electric decoupling (TED) approach is proposed to both bring down the constraint of forced power output of combined heat and power plants and increase the electric load level during valley load times that assist the power grid in consuming more wind power. The operating principles of the thermal-electric decoupling approach is described, the mathematical model of its profits is developed, the constraint conditions of its operation are listed, also, an improved parallel conjugate gradient is utilized to bypass the saddle problem and accelerate the optimal speed. Numerical simulations are implemented and reveal an optimal allocation of TED which with a rated power of 280 MW and 185 MWh heat storage capacity are possible. This allocation of TED could bring approximately 16.9 billion Yuan of economic profit and consume more than 80% of the surplus wind energy which wo... [more]
Performance Characteristics of a Modularized and Integrated PTC Heating System for an Electric Vehicle
Yoon Hyuk Shin, Seungkyu Sim, Sung Chul Kim
October 23, 2018 (v1)
Keywords: heating power density, high voltage, performance characteristics, PTC heating system, weight reduction
A modularized positive temperature coefficient heating system has controller-integrated heater modules. Such a heating system that uses a high-voltage power of 330 V was developed in the present study for use in electric vehicles. Four heater modules and one controller with an input power of 5.6 kW were integrated in the modularized system, which was designed for improved heating power density and light weight compared to the conventional heating system, in which the controller is separated. We experimentally investigated the performance characteristics, namely, the heating capacity, energy efficiency, and pressure drop, of a prototype of the developed heating system and found it to have satisfactory performance. The findings of this study will contribute to the development of heating systems for electric vehicles.
Fumed Silica Nanoparticles Incorporated in Quaternized Poly(Vinyl Alcohol) Nanocomposite Membrane for Enhanced Power Densities in Direct Alcohol Alkaline Fuel Cells
Selvaraj Rajesh Kumar, Cheng-Hsin Juan, Guan-Ming Liao, Jia-Shiun Lin, Chun-Chen Yang, Wei-Ting Ma, Jiann-Hua You, Shingjiang Jessie Lue
October 23, 2018 (v1)
Subject: Materials
Keywords: cell performance, Ethanol, fumed silica, ionic conductivity, Methanol, quaternized poly(vinyl alcohol)
A nanocomposite polymer membrane based on quaternized poly(vinyl alcohol)/fumed silica (QPVA/FS) was prepared via a quaternization process and solution casting method. The physico-chemical properties of the QPVA/FS membrane were investigated. Its high ionic conductivity was found to depend greatly on the concentration of fumed silica in the QPVA matrix. A maximum conductivity of 3.50 × 10−2 S/cm was obtained for QPVA/5%FS at 60 °C when it was doped with 6 M KOH. The permeabilities of methanol and ethanol were reduced with increasing fumed silica content. Cell voltage and peak power density were analyzed as functions of fumed silica concentration, temperature, methanol and ethanol concentrations. A maximum power density of 96.8 mW/cm² was achieved with QPVA/5%FS electrolyte using 2 M methanol + 6 M KOH as fuel at 80 °C. A peak power density of 79 mW/cm² was obtained using the QPVA/5%FS electrolyte with 3 M ethanol + 5 M KOH as fuel. The resulting peak power densities are higher than the... [more]
Methods for Global Survey of Natural Gas Flaring from Visible Infrared Imaging Radiometer Suite Data
Christopher D. Elvidge, Mikhail Zhizhin, Kimberly Baugh, Feng-Chi Hsu, Tilottama Ghosh
October 23, 2018 (v1)
Keywords: carbon dioxide emissions, carbon intensity, gas flaring, Nightfire, Visible Infrared Imaging Radiometer Suite (VIIRS)
A set of methods are presented for the global survey of natural gas flaring using data collected by the National Aeronautics and Space Administration/National Oceanic and Atmospheric Administration NASA/NOAA Visible Infrared Imaging Radiometer Suite (VIIRS). The accuracy of the flared gas volume estimates is rated at ±9.5%. VIIRS is particularly well suited for detecting and measuring the radiant emissions from gas flares through the collection of shortwave and near-infrared data at night, recording the peak radiant emissions from flares. In 2012, a total of 7467 individual flare sites were identified. The total flared gas volume is estimated at 143 (±13.6) billion cubic meters (BCM), corresponding to 3.5% of global production. While the USA has the largest number of flares, Russia leads in terms of flared gas volume. Ninety percent of the flared gas volume was found in upstream production areas, 8% at refineries and 2% at liquified natural gas (LNG) terminals. The results confirm that... [more]
Generation of Hydrogen, Lignin and Sodium Hydroxide from Pulping Black Liquor by Electrolysis
Guangzai Nong, Zongwen Zhou, Shuangfei Wang
October 22, 2018 (v1)
Keywords: black liquor, electrolysis, Energy, Hydrogen, lignin
Black liquor is generated in Kraft pulping of wood or non-wood raw material in pulp mills, and regarded as a renewable resource. The objective of this paper was to develop an effective means to remove the water pollutants by recovery of both lignin and sodium hydroxide from black liquor, based on electrolysis. The treatment of a 1000 mL of black liquor (122 g/L solid contents) consumed 345.6 kJ of electric energy, and led to the generation of 30.7 g of sodium hydroxide, 0.82 g of hydrogen gas and 52.1 g of biomass solids. Therefore, the recovery ratios of elemental sodium and biomass solids are 80.4% and 76%, respectively. Treating black liquor by electrolysis is an environmentally friendly technology that can, in particular, be an alternative process in addressing the environmental issues of pulping waste liquor to the small-scale mills without black liquor recovery.
A Simple Operating Strategy of Small-Scale Battery Energy Storages for Energy Arbitrage under Dynamic Pricing Tariffs
Enrico Telaretti, Mariano Ippolito, Luigi Dusonchet
October 22, 2018 (v1)
Keywords: battery energy storage system, energy management, hourly electricity prices, optimal operation, price arbitrage
Price arbitrage involves taking advantage of an electricity price difference, storing electricity during low-prices times, and selling it back to the grid during high-prices periods. This strategy can be exploited by customers in presence of dynamic pricing schemes, such as hourly electricity prices, where the customer electricity cost may vary at any hour of day, and power consumption can be managed in a more flexible and economical manner, taking advantage of the price differential. Instead of modifying their energy consumption, customers can install storage systems to reduce their electricity bill, shifting the energy consumption from on-peak to off-peak hours. This paper develops a detailed storage model linking together technical, economic and electricity market parameters. The proposed operating strategy aims to maximize the profit of the storage owner (electricity customer) under simplifying assumptions, by determining the optimal charge/discharge schedule. The model can be appl... [more]
Enhancing LVRT of DFIG by Using a Superconducting Current Limiter on Rotor Circuit
Flávio Oliveira, Arthur Amorim, Lucas Encarnação, Jussara Fardin, Marcos Orlando, Selênio Silva, Domingos Simonetti
October 22, 2018 (v1)
Keywords: crowbar, doubly fed induction generator (DFIG), low voltage ride-through (LVRT), superconducting current limiter (SCL), voltage sags, wind turbines
This paper have studied the dynamic of a 2.0 MW Doubly Fed Induction Generator (DFIG) during a severe voltage sag. Using the dynamic model of a DFIG, it was possible to determine the current, Electromagnetic Force and flux behavior during three-phase symmetrical voltage dip. Among the technologies of wind turbines the DFIG is widely employed; however, this machine is extremely susceptible to disturbances from the grid. In order to improve DFIG Low Voltage Ride-Through (LVRT), it is proposed a novel solution, using Superconducting Current Limiter (SCL) in two arrangements: one, the SCL is placed between the machine rotor and the rotor side converter (RSC), and another placed in the RSC DC-link. The proposal is validated through simulation using PSCAD™/EMTDC™ and according to requirements of specific regulations. The analysis ensure that both SCL arrangements behave likewise, and are effective in decrement the rotor currents during the disturbance.
A Power Prediction Method for Photovoltaic Power Plant Based on Wavelet Decomposition and Artificial Neural Networks
Honglu Zhu, Xu Li, Qiao Sun, Ling Nie, Jianxi Yao, Gang Zhao
October 22, 2018 (v1)
Keywords: artificial neural network, photovoltaic power prediction, signal reconstruction, theoretical solar irradiance, wavelet decomposition
The power prediction for photovoltaic (PV) power plants has significant importance for their grid connection. Due to PV power’s periodicity and non-stationary characteristics, traditional power prediction methods based on linear or time series models are no longer applicable. This paper presents a method combining the advantages of the wavelet decomposition (WD) and artificial neural network (ANN) to solve this problem. With the ability of ANN to address nonlinear relationships, theoretical solar irradiance and meteorological variables are chosen as the input of the hybrid model based on WD and ANN. The output power of the PV plant is decomposed using WD to separated useful information from disturbances. The ANNs are used to build the models of the decomposed PV output power. Finally, the outputs of the ANN models are reconstructed into the forecasted PV plant power. The presented method is compared with the traditional forecasting method based on ANN. The results shows that the method... [more]
Design and Control of a 3 kW Wireless Power Transfer System for Electric Vehicles
Zhenshi Wang, Xuezhe Wei, Haifeng Dai
October 22, 2018 (v1)
Keywords: electric vehicle, power regulation, topology analysis, wireless power transfer (WPT)
This paper aims to study a 3 kW wireless power transfer system for electric vehicles. First, the LCL-LCL topology and LC-LC series topology are analyzed, and their transfer efficiencies under the same transfer power are compared. The LC-LC series topology is validated to be more efficient than the LCL-LCL topology and thus is more suitable for the system design. Then a novel q-Zsource-based online power regulation method which employs a unique impedance network (two pairs of inductors and capacitors) to couple the cascaded H Bridge to the power source is proposed. By controlling the shoot-through state of the H Bridge, the charging current can be adjusted, and hence, transfer power. Finally, a prototype is implemented, which can transfer 3 kW wirelessly with ~95% efficiency over a 20 cm transfer distance.
Hybrid Wind Speed Prediction Based on a Self-Adaptive ARIMAX Model with an Exogenous WRF Simulation
Erdong Zhao, Jing Zhao, Liwei Liu, Zhongyue Su, Ning An
October 22, 2018 (v1)
Keywords: ARIMAX, self-adaptive strategy, wind speed, WRF simulation
Wind speed forecasting is difficult not only because of the influence of atmospheric dynamics but also for the impossibility of providing an accurate prediction with traditional statistical forecasting models that work by discovering an inner relationship within historical records. This paper develops a self-adaptive (SA) auto-regressive integrated moving average with exogenous variables (ARIMAX) model that is optimized very-short-term by the chaotic particle swarm optimization (CPSO) algorithm, known as the SA-ARIMA-CPSO approach, for wind speed prediction. The ARIMAX model chooses the wind speed result from the Weather Research and Forecasting (WRF) simulation as an exogenous input variable. Further, an SA strategy is applied to the ARIMAX process. When new information is available, the model process can be updated adaptively with parameters optimized by the CPSO algorithm. The proposed SA-ARIMA-CPSO approach enables the forecasting process to update training information and model pa... [more]
Empirical Validation of a Thermal Model of a Complex Roof Including Phase Change Materials
Stéphane Guichard, Frédéric Miranville, Dimitri Bigot, Bruno Malet-Damour, Teddy Libelle, Harry Boyer
October 22, 2018 (v1)
Keywords: building thermal simulation, model optimization, model validation, phase change materials (PCMs)
This paper deals with the empirical validation of a building thermal model of a complex roof including a phase change material (PCM). A mathematical model dedicated to PCMs based on the heat apparent capacity method was implemented in a multi-zone building simulation code, the aim being to increase the understanding of the thermal behavior of the whole building with PCM technologies. In order to empirically validate the model, the methodology is based both on numerical and experimental studies. A parametric sensitivity analysis was performed and a set of parameters of the thermal model has been identified for optimization. The use of the generic optimization program called GenOpt® coupled to the building simulation code enabled to determine the set of adequate parameters. We first present the empirical validation methodology and main results of previous work. We then give an overview of GenOpt® and its coupling with the building simulation code. Finally, once the optimization results a... [more]
Error Assessment of Solar Irradiance Forecasts and AC Power from Energy Conversion Model in Grid-Connected Photovoltaic Systems
Gianfranco Chicco, Valeria Cocina, Paolo Di Leo, Filippo Spertino, Alessandro Massi Pavan
October 22, 2018 (v1)
Keywords: distributed generation, error assessment, irradiance spike, photovoltaic (PV) conversion model, photovoltaic systems, power profiles, Renewable and Sustainable Energy, weather forecasts
Availability of effective estimation of the power profiles of photovoltaic systems is essential for studying how to increase the share of intermittent renewable sources in the electricity mix of many countries. For this purpose, weather forecasts, together with historical data of the meteorological quantities, provide fundamental information. The weak point of the forecasts depends on variable sky conditions, when the clouds successively cover and uncover the solar disc. This causes remarkable positive and negative variations in the irradiance pattern measured at the photovoltaic (PV) site location. This paper starts from 1 to 3 days-ahead solar irradiance forecasts available during one year, with a few points for each day. These forecasts are interpolated to obtain more irradiance estimations per day. The estimated irradiance data are used to classify the sky conditions into clear, variable or cloudy. The results are compared with the outcomes of the same classification carried out wi... [more]
A Numerical Study on System Performance of Groundwater Heat Pumps
Jinsang Kim, Yujin Nam
October 22, 2018 (v1)
Keywords: coefficient of performance, groundwater heat pump, heat exchanger, regression analysis, UA value
Groundwater heat pumps have energy saving potential where the groundwater resources are sufficient. System Coefficients of Performance (COPs) are measurements of performance of groundwater heat pump systems. In this study, the head and power of submersible pumps, heat pump units, piping, and heat exchangers are expressed as polynomial equations, and these equations are solved numerically to determine the system performance. Regression analysis is used to find the coefficients of the polynomial equations from a catalog of performance data. The cooling and heating capacities of water-to-water heat pumps are determined using Energy Plus. Results show that system performance drops as the water level drops, and the lowest flow rates generally achieve the highest system performance. The system COPs are used to compare the system performance of various system configurations. The groundwater pumping level and temperature provide the greatest effects on the system performance of groundwater hea... [more]
Wind Turbine Fault Detection through Principal Component Analysis and Statistical Hypothesis Testing
Francesc Pozo, Yolanda Vidal
October 22, 2018 (v1)
Keywords: FAST (Fatigue, Aerodynamics, Structures and Turbulence), Fault Detection, principal component analysis, statistical hypothesis testing, wind turbine
This paper addresses the problem of online fault detection of an advanced wind turbine benchmark under actuators (pitch and torque) and sensors (pitch angle measurement) faults of different type: fixed value, gain factor, offset and changed dynamics. The fault detection scheme starts by computing the baseline principal component analysis (PCA) model from the healthy or undamaged wind turbine. Subsequently, when the structure is inspected or supervised, new measurements are obtained are projected into the baseline PCA model. When both sets of data—the baseline and the data from the current wind turbine—are compared, a statistical hypothesis testing is used to make a decision on whether or not the wind turbine presents some damage, fault or misbehavior. The effectiveness of the proposed fault-detection scheme is illustrated by numerical simulations on a well-known large offshore wind turbine in the presence of wind turbulence and realistic fault scenarios. The obtained results demonstrat... [more]
Heuristic Optimization of Consumer Electricity Costs Using a Generic Cost Model
Chris Ogwumike, Michael Short, Fathi Abugchem
October 22, 2018 (v1)
Keywords: decision support system, demand side management, heuristic algorithm, load scheduling, smart grid
Many new demand response strategies are emerging for energy management in smart grids. Real-Time Energy Pricing (RTP) is one important aspect of consumer Demand Side Management (DSM), which encourages consumers to participate in load scheduling. This can help reduce peak demand and improve power system efficiency. The use of Intelligent Decision Support Systems (IDSSs) for load scheduling has become necessary in order to enable consumers to respond to the changing economic value of energy across different hours of the day. The type of scheduling problem encountered by a consumer IDSS is typically NP-hard, which warrants the search for good heuristics with efficient computational performance and ease of implementation. This paper presents an extensive evaluation of a heuristic scheduling algorithm for use in a consumer IDSS. A generic cost model for hourly pricing is utilized, which can be configured for traditional on/off peak pricing, RTP, Time of Use Pricing (TOUP), Two-Tier Pricing... [more]
Energy Management Strategy for Microgrids by Using Enhanced Bee Colony Optimization
Whei-Min Lin, Chia-Sheng Tu, Ming-Tang Tsai
October 22, 2018 (v1)
Keywords: bee colony optimization, microgrid, Renewable and Sustainable Energy, time-of-use
This paper presents a microgrid (MG) energy management strategy by considering renewable energy and battery storage systems. Renewable energy, including wind power generation and solar power generation, is integrated into the distribution network, for which is formulated the optimal dispatch model of mixed-power generation by considering the charging/discharging scheduling of battery storage systems. The MG system has an electrical link for power exchange between the MG and the utility during different hours of the day. Based on the time-of-use (TOU) and all technical constraints, an enhanced bee colony optimization (EBCO) is proposed to solve the daily economic dispatch of MG systems. In the EBCO procedure, the self-adaption repulsion factor is embedded in the bee swarm of the BCO in order to improve the behavior patterns of each bee swarm and increase its search efficiency and accuracy in high dimensions. Different modifications in moving patterns of EBCO are proposed to search the f... [more]
Reconfiguration of Urban Photovoltaic Arrays Using Commercial Devices
Sergio Ignacio Serna-Garcés, Juan David Bastidas-Rodríguez, Carlos Andrés Ramos-Paja
October 22, 2018 (v1)
Subject: Energy Policy
Keywords: embedded systems, hardware in the loop, mismatching conditions, optimal configuration, partial shading, reconfiguration, series-parallel arrays
A recent approach to mitigate the adverse effects of photovoltaic (PV) arrays operating under mismatching conditions is the dynamic electrical reconfiguration of the PV panels. This paper introduces a procedure to determine the best configuration of a PV array connected in a series-parallel structure without using complex mathematical models. Such a procedure uses the experimental current vs. voltage curves of the PV panels, which are composed of multiple PV modules, to construct the power vs. voltage curves of all of the possible configurations to identify the optimal one. The main advantage of this method is the low computational effort required to reconstruct the power vs. voltage curves of the array. This characteristic enables one to implement the proposed solution using inexpensive embedded devices, which are widely adopted in industrial applications. The proposed method, and its embedded implementation, were tested using a hardware-in-the-loop simulation of the PV system. Finall... [more]
A New Fast Peak Current Controller for Transient Voltage Faults for Power Converters
Jesús Muñoz-Cruzado-Alba, Javier Villegas-Núñez, José Alberto Vite-Frías, Juan Manuel Carrasco Solís
October 22, 2018 (v1)
Keywords: dip voltage, distributed generators (DGs), fast peak current control (FPCC), phase-jump ride through (PJRT), photo-voltaic (PV) systems, voltage ride through (VRT)
Power converters are the basic unit for the transient voltage fault ride through capability for most renewable distributed generators (DGs). When a transient fault happens, the grid voltage will drop suddenly and probably will also suffer a phase-jump event as well. State-of-the-art voltage fault control techniques regulate the current injected during the grid fault. However, the beginning of the fault could be too fast for the inner current control loops of the inverter, and transient over-current would be expected. In order to avoid the excessive peak current of the methods presented in the literature, a new fast peak current control (FPCC) technique is proposed. Controlling the peak current magnitude avoids undesirable disconnection of the distributed generator in a fault state and improves the life expectancy of the converter. Experimental and simulation tests with high power converters provide the detailed behaviour of the method with excellent results.
Low-Cost Feedstock Conversion to Biodiesel via Ultrasound Technology
Omotola Babajide, Leslie Petrik, Bamikole Amigun, Farouk Ameer
October 22, 2018 (v1)
Keywords: biodiesel, conversion efficiency, glycerol, transesterification, ultrasound
Biodiesel has attracted increasing interest and has proved to be a good substitute for fossil-based fuels due to its environmental advantages and availability from renewable resources such as refined and waste vegetable oils. Several studies have shown that biodiesel is a better fuel than the fossil-derived diesel in terms of engine performance, emissions reduction, lubricity and environmental benefits. The increasing popularity of biodiesel has generated great demand for its commercial production methods, which in turn calls for the development of technically and economically sound process technologies. This paper explores the applicability of ultrasound in the optimization of low-cost feedstock ⁻ in this case waste cooking oil ⁻ in the transesterification conversion to biodiesel. It was found that the conversion efficiency of the waste oil using ultrasound was higher than with the mechanical stirring method. The optimized variables of 6:1 methanol/oil ratio at a reaction temperature... [more]
Spectrally-Selective Photonic Structures for PV Applications
Marius Peters, Jan Christoph Goldschmidt, Philipp Löper, Bernhard Groß, Johannes Üpping, Frank Dimroth, Ralf B. Wehrspohn, Benedikt Bläsi
October 22, 2018 (v1)
Subject: Materials
Keywords: light trapping, photonic crystals, spectral selectivity
We review several examples of how spectrally-selective photonic structures may be used to improve solar cell systems. Firstly, we introduce different spectrally-selective structures that are based on interference effects. Examples shown include Rugate filter, edge filter and 3D photonic crystals such as artificial opals. In the second part, we discuss several examples of photovoltaic (PV) concepts that utilize spectral selectivity such as fluorescence collectors, upconversion systems, spectrum splitting concepts and the intermediate reflector concept. The potential of spectrally selective filters in the context of solar cells is discussed.
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