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Energies, Volume 10, Issue 10 (October 2017)

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Cover Story (view full-size image) Medium-sized commercial buildings account for approximately 50% of Australia’s commercial office [...] Read more.
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Open AccessCorrection Correction: Hu, Z.; et al. Transport and Deposition of Carbon Nanoparticles in Saturated Porous Media. Energies 2017, 10, 1151
Energies 2017, 10(10), 1681; https://doi.org/10.3390/en10101681
Received: 16 June 2017 / Accepted: 2 August 2017 / Published: 24 October 2017
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Abstract
The author wishes to correct Figure 1b in this paper [1][...] Full article
(This article belongs to the Special Issue Nanotechnology for Oil and Gas Applications)
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Open AccessArticle Numerical Simulation of Hydraulic Fracture Propagation Guided by Single Radial Boreholes
Energies 2017, 10(10), 1680; https://doi.org/10.3390/en10101680
Received: 11 September 2017 / Revised: 12 October 2017 / Accepted: 20 October 2017 / Published: 23 October 2017
Cited by 2 | PDF Full-text (7121 KB) | HTML Full-text | XML Full-text
Abstract
Conventional hydraulic fracturing is not effective in target oil development zones with available wellbores located in the azimuth of the non-maximum horizontal in-situ stress. To some extent, we think that the radial hydraulic jet drilling has the function of guiding hydraulic fracture propagation
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Conventional hydraulic fracturing is not effective in target oil development zones with available wellbores located in the azimuth of the non-maximum horizontal in-situ stress. To some extent, we think that the radial hydraulic jet drilling has the function of guiding hydraulic fracture propagation direction and promoting deep penetration, but this notion currently lacks an effective theoretical support for fracture propagation. In order to verify the technology, a 3D extended finite element numerical model of hydraulic fracturing promoted by the single radial borehole was established, and the influences of nine factors on propagation of hydraulic fracture guided by the single radial borehole were comprehensively analyzed. Moreover, the term ‘Guidance factor (Gf)’ was introduced for the first time to effectively quantify the radial borehole guidance. The guidance of nine factors was evaluated through gray correlation analysis. The experimental results were consistent with the numerical simulation results to a certain extent. The study provides theoretical evidence for the artificial control technology of directional propagation of hydraulic fracture promoted by the single radial borehole, and it predicts the guidance effect of a single radial borehole on hydraulic fracture to a certain extent, which is helpful for planning well-completion and fracturing operation parameters in radial borehole-promoted hydraulic fracturing technology. Full article
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Open AccessFeature PaperArticle Flat Optical Fiber Daylighting System with Lateral Displacement Sun-Tracking Mechanism for Indoor Lighting
Energies 2017, 10(10), 1679; https://doi.org/10.3390/en10101679
Received: 28 September 2017 / Revised: 14 October 2017 / Accepted: 20 October 2017 / Published: 23 October 2017
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Abstract
An essential impact which can improve the indoor environment and save on power consumption for artificial lighting is utilization of daylight. Optical fiber daylighting technology offers a way to use direct daylight for remote spaces in a building. However, the existing paradigm based
[...] Read more.
An essential impact which can improve the indoor environment and save on power consumption for artificial lighting is utilization of daylight. Optical fiber daylighting technology offers a way to use direct daylight for remote spaces in a building. However, the existing paradigm based on the precise orientation of sunlight concentrator toward the Sun is very costly and difficult to install on the roof of buildings. Here, we explore an alternative approach using mirror-coated lens array and planar waveguide to develop a flat optical fiber daylighting system (optical fiber daylighting panel) with lateral displacement Sun-tracking mechanism. Sunlight collected and reflected by each mirror-coated lens in a rectangular lens array is coupled into a planar waveguide using cone prisms placed at each lens focus. This geometry yields a thin, flat profile for Sunlight concentrator. Our proposed concentrating panel can be achieved with 35 mm thickness while the concentrator’s width and length are 500 mm × 500 mm. The commercial optical simulation tool (LightToolsTM) was used to develop the simulation models and analyze the system performance. Simulation results based on the designed system demonstrated an optical efficiency of 51.4% at a concentration ratio of 125. The system can support utilizing a lateral displacement Sun-tracking system, which allows for replacing bulky and robust conventional rotational Sun-tracking systems. This study shows a feasibility of a compact and inexpensive optical fiber daylighting system to be installed on the roof of buildings. Full article
(This article belongs to the Special Issue Solar Energy Application in Buildings)
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Open AccessArticle Characterization and Prediction of the Gas Hydrate Reservoir at the Second Offshore Gas Production Test Site in the Eastern Nankai Trough, Japan
Energies 2017, 10(10), 1678; https://doi.org/10.3390/en10101678
Received: 2 August 2017 / Revised: 15 September 2017 / Accepted: 9 October 2017 / Published: 23 October 2017
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Abstract
Following the world’s first offshore production test that was conducted from a gas hydrate reservoir by a depressurization technique in 2013, the second offshore production test has been planned in the eastern Nankai Trough. In 2016, the drilling survey was performed ahead of
[...] Read more.
Following the world’s first offshore production test that was conducted from a gas hydrate reservoir by a depressurization technique in 2013, the second offshore production test has been planned in the eastern Nankai Trough. In 2016, the drilling survey was performed ahead of the production test, and logging data that covers the reservoir interval were newly obtained from three wells around the test site: one well for geological survey, and two wells for monitoring surveys, during the production test. The formation evaluation using the well log data suggested that our target reservoir has a more significant heterogeneity in the gas hydrate saturation distribution than we expected, although lateral continuity of sand layers is relatively good. To evaluate the spatial distribution of gas hydrate, the integration analysis using well and seismic data was performed. The seismic amplitude analysis supports the lateral reservoir heterogeneity that has a significant positive correlation with the resistivity log data at the well locations. The spatial distribution of the apparent low-resistivity interval within the reservoir observed from log data was investigated by the P-velocity volume derived from seismic inversion. The integrated results were utilized for the pre-drill prediction of the reservoir quality at the producing wells. These approaches will reduce the risk of future commercial production from the gas hydrate reservoir. Full article
(This article belongs to the Special Issue Methane Hydrate Research and Development)
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Open AccessArticle Design of Parallel Air-Cooled Battery Thermal Management System through Numerical Study
Energies 2017, 10(10), 1677; https://doi.org/10.3390/en10101677
Received: 10 August 2017 / Revised: 18 October 2017 / Accepted: 19 October 2017 / Published: 23 October 2017
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Abstract
In electric vehicles, the battery pack is one of the most important components that strongly influence the system performance. The battery thermal management system (BTMS) is critical to remove the heat generated by the battery pack, which guarantees the appropriate working temperature for
[...] Read more.
In electric vehicles, the battery pack is one of the most important components that strongly influence the system performance. The battery thermal management system (BTMS) is critical to remove the heat generated by the battery pack, which guarantees the appropriate working temperature for the battery pack. Air cooling is one of the most commonly-used solutions among various battery thermal management technologies. In this paper, the cooling performance of the parallel air-cooled BTMS is improved through choosing appropriate system parameters. The flow field and the temperature field of the system are calculated using the computational fluid dynamics method. Typical numerical cases are introduced to study the influences of the operation parameters and the structure parameters on the performance of the BTMS. The operation parameters include the discharge rate of the battery pack, the inlet air temperature and the inlet airflow rate. The structure parameters include the cell spacing and the angles of the divergence plenum and the convergence plenum. The results show that the temperature rise and the temperature difference of the batter pack are not affected by the inlet air flow temperature and are increased as the discharge rate increases. Increasing the inlet airflow rate can reduce the maximum temperature, but meanwhile significantly increase the power consumption for driving the airflow. Adopting smaller cell spacing can reduce the temperature and the temperature difference of the battery pack, but it consumes much more power. Designing the angles of the divergence plenum and the convergence plenum is an effective way to improve the performance of the BTMS without occupying more system volume. An optimization strategy is used to obtain the optimal values of the plenum angles. For the numerical cases with fixed power consumption, the maximum temperature and the maximum temperature difference at the end of the five-current discharge process for the optimized BTMS are respectively reduced by 2.1 K and 4.3 K, compared to the original system. Full article
(This article belongs to the Special Issue Thermal Energy Storage and Thermal Management (TESM2017))
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Open AccessArticle Solar-Enhanced Air-Cooled Heat Exchangers for Geothermal Power Plants
Energies 2017, 10(10), 1676; https://doi.org/10.3390/en10101676
Received: 6 September 2017 / Revised: 18 October 2017 / Accepted: 19 October 2017 / Published: 23 October 2017
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Abstract
This paper focuses on the optimization of a Solar-Enhanced Natural-Draft Dry-Cooling Tower (SENDDCT), originally designed by the Queensland Geothermal Energy Centre of Excellence (QGECE), as the air-cooled condenser of a geothermal power plant. The conventional method of heat transfer augmentation through fin-assisted area
[...] Read more.
This paper focuses on the optimization of a Solar-Enhanced Natural-Draft Dry-Cooling Tower (SENDDCT), originally designed by the Queensland Geothermal Energy Centre of Excellence (QGECE), as the air-cooled condenser of a geothermal power plant. The conventional method of heat transfer augmentation through fin-assisted area extension is compared with a metal foam-wrapped tube bundle. Both lead to heat-transfer enhancement, albeit at the expense of a higher pressure drop when compared to the bare tube bundle as our reference case. An optimal design is obtained through the use of a simplified analytical model and existing correlations by maximizing the heat transfer rate with a minimum pressure drop goal as the constraint. Sensitivity analysis was conducted to investigate the effect of sunroof diameter, as well as tube bundle layouts and tube spacing, on the overall performance of the system. Aiming to minimize the flow and thermal resistances for a SENDDCT, an optimum design is presented for an existing tower to be equipped with solar panels to afterheat the air leaving the heat exchanger bundles, which are arranged vertically around the tower skirt. Finally, correlations are proposed to predict the total pressure drop and heat transfer of the extended surfaces considered here. Full article
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Open AccessArticle A Novel Topology of Hybrid HVDC Circuit Breaker for VSC-HVDC Application
Energies 2017, 10(10), 1675; https://doi.org/10.3390/en10101675
Received: 19 September 2017 / Revised: 17 October 2017 / Accepted: 19 October 2017 / Published: 23 October 2017
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Abstract
The use of high voltage direct current (HVDC) circuit breakers (CBs) with the capabilities of bidirectional fault interruption, reclosing, and rebreaking can improve the reliable and safe operation of HVDC grids. Although several topologies of CBs have been proposed to perform these capabilities,
[...] Read more.
The use of high voltage direct current (HVDC) circuit breakers (CBs) with the capabilities of bidirectional fault interruption, reclosing, and rebreaking can improve the reliable and safe operation of HVDC grids. Although several topologies of CBs have been proposed to perform these capabilities, the limitation of these topologies is either high on-state losses or long time interruption in the case bidirectional fault current interruption. Long time interruption results in the large magnitude of the fault current in the voltage source converter based HVDC (VSC-HVDC) system due to the high rate of rise of fault current. This paper proposes a new topology of hybrid CB (HCB) with lower conduction loss and lower interruption time to solve the problems. The proposed topology is based on the inverse current injection method, which uses the capacitor to enforce the fault current to zero. In the case of the bidirectional fault current interruption, the capacitor does not change its polarity after identifying the direction of fault current, which can reduce the interruption time accordingly. A switching control algorithm for the proposed topology is presented in detail. Different operation modes of proposed HCB, such as normal current mode, breaking fault current mode, discharging, and reversing capacitor voltage modes after clearing the fault, are considered in the proposed algorithm. The proposed topology with the switching control algorithm is tested in a simulation-based system. Different simulation scenarios such as temporary and permanent faults are carried out to verify the performance of the proposed topology. The simulation is performed in the Matlab/Simulink environment. Full article
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Open AccessArticle A Comparative Study of CFD Models of a Real Wind Turbine in Solar Chimney Power Plants
Energies 2017, 10(10), 1674; https://doi.org/10.3390/en10101674
Received: 19 September 2017 / Revised: 10 October 2017 / Accepted: 18 October 2017 / Published: 23 October 2017
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Abstract
A solar chimney power plant consists of four main parts, a solar collector, a chimney, an energy storage layer, and a wind turbine. So far, several investigations on the performance of the solar chimney power plant have been conducted. Among them, different approaches
[...] Read more.
A solar chimney power plant consists of four main parts, a solar collector, a chimney, an energy storage layer, and a wind turbine. So far, several investigations on the performance of the solar chimney power plant have been conducted. Among them, different approaches have been applied to model the turbine inside the system. In particular, a real wind turbine coupled to the system was simulated using computational fluid dynamics (CFD) in three investigations. Gholamalizadeh et al. simulated a wind turbine with the same blade profile as the Manzanares SCPP’s turbine (FX W-151-A blade profile), while a CLARK Y blade profile was modelled by Guo et al. and Ming et al. In this study, simulations of the Manzanares prototype were carried out using the CFD model developed by Gholamalizadeh et al. Then, results obtained by modelling different turbine blade profiles at different turbine rotational speeds were compared. The results showed that a turbine with the CLARK Y blade profile significantly overestimates the value of the pressure drop across the Manzanares prototype turbine as compared to the FX W-151-A blade profile. In addition, modelling of both blade profiles led to very similar trends in changes in turbine efficiency and power output with respect to rotational speed. Full article
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Open AccessArticle Performance Assessment of Black Box Capacity Forecasting for Multi-Market Trade Application
Energies 2017, 10(10), 1673; https://doi.org/10.3390/en10101673
Received: 28 August 2017 / Revised: 17 October 2017 / Accepted: 17 October 2017 / Published: 23 October 2017
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Abstract
With the growth of renewable generated electricity in the energy mix, large energy storage and flexible demand, particularly aggregated demand response is becoming a front runner as a new participant in the wholesale energy markets. One of the biggest barriers for the integration
[...] Read more.
With the growth of renewable generated electricity in the energy mix, large energy storage and flexible demand, particularly aggregated demand response is becoming a front runner as a new participant in the wholesale energy markets. One of the biggest barriers for the integration of aggregator services into market participation is knowledge of the current and future flexible capacity. To calculate the available flexibility, the current aggregator pilot and simulation implementations use lower level measurements and device specifications. This type of implementation is not scalable due to computational constraints, as well as it could conflict with end user privacy rights. Black box machine learning approaches have been proven to accurately estimate the available capacity of a cluster of heating devices using only aggregated data. This study will investigate the accuracy of this approach when applied to a heterogeneous virtual power plant (VPP). Firstly, a sensitivity analysis of the machine learning model is performed when varying the underlying device makeup of the VPP. Further, the forecasted flexible capacity of a heterogeneous residential VPP was applied to a trade strategy, which maintains a day ahead schedule, as well as offers flexibility to the imbalance market. This performance is then compared when using the same strategy with no capacity forecasting, as well as perfect knowledge. It was shown that at most, the highest average error, regardless of the VPP makeup, was still less than 9%. Further, when applying the forecasted capacity to a trading strategy, 89% of the optimal performance can be met. This resulted in a reduction of monthly costs by approximately 20%. Full article
(This article belongs to the Special Issue Selected Papers from International Workshop of Energy-Open)
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Open AccessReview Building Applications, Opportunities and Challenges of Active Shading Systems: A State-of-the-Art Review
Energies 2017, 10(10), 1672; https://doi.org/10.3390/en10101672
Received: 28 June 2017 / Revised: 2 August 2017 / Accepted: 4 August 2017 / Published: 23 October 2017
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Abstract
Active shading systems in buildings have emerged as a high performing shading solution that selectively and optimally controls daylight and heat gains. Active shading systems are increasingly used in buildings, due to their ability to mainly improve the building environment, reduce energy consumption
[...] Read more.
Active shading systems in buildings have emerged as a high performing shading solution that selectively and optimally controls daylight and heat gains. Active shading systems are increasingly used in buildings, due to their ability to mainly improve the building environment, reduce energy consumption and in some cases generate energy. They may be categorized into three classes: smart glazing, kinetic shading and integrated renewable energy shading. This paper reviews the current status of the different types in terms of design principle and working mechanism of the systems, performance, control strategies and building applications. Challenges, limitations and future opportunities of the systems are then discussed. The review highlights that despite its high initial cost, the electrochromic (EC) glazing is the most applied smart glazing due to the extensive use of glass in buildings under all climatic conditions. In terms of external shadings, the rotating shading type is the predominantly used one in buildings due to its low initial cost. Algae façades and folding shading systems are still emerging types, with high initial and maintenance costs and requiring specialist installers. The algae façade systems and PV integrated shading systems are a promising solution due to their dual benefits of providing shading and generating electricity. Active shading systems were found to save 12 to 50% of the building cooling electricity consumption. Full article
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Open AccessArticle An Optimized Prediction Intervals Approach for Short Term PV Power Forecasting
Energies 2017, 10(10), 1669; https://doi.org/10.3390/en10101669
Received: 30 August 2017 / Revised: 12 October 2017 / Accepted: 16 October 2017 / Published: 23 October 2017
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Abstract
High quality photovoltaic (PV) power prediction intervals (PIs) are essential to power system operation and planning. To improve the reliability and sharpness of PIs, in this paper, a new method is proposed, which involves the model uncertainties and noise uncertainties, and PIs are
[...] Read more.
High quality photovoltaic (PV) power prediction intervals (PIs) are essential to power system operation and planning. To improve the reliability and sharpness of PIs, in this paper, a new method is proposed, which involves the model uncertainties and noise uncertainties, and PIs are constructed with a two-step formulation. In the first step, the variance of model uncertainties is obtained by using extreme learning machine to make deterministic forecasts of PV power. In the second stage, innovative PI-based cost function is developed to optimize the parameters of ELM and noise uncertainties are quantization in terms of variance. The performance of the proposed approach is examined by using the PV power and meteorological data measured from 1kW rooftop DC micro-grid system. The validity of the proposed method is verified by comparing the experimental analysis with other benchmarking methods, and the results exhibit a superior performance. Full article
(This article belongs to the Section Energy Storage and Application)
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Open AccessArticle Laser Radiation Induces Growth and Lipid Accumulation in the Seawater Microalga Chlorella pacifica
Energies 2017, 10(10), 1671; https://doi.org/10.3390/en10101671
Received: 13 September 2017 / Revised: 13 October 2017 / Accepted: 16 October 2017 / Published: 22 October 2017
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Abstract
The impacts of laser radiation (Nd: YAG laser, 1064 nm at 800 mW, He–Ne laser 808 nm at 6 W, semiconductor laser 632.8 nm at 40 mW) on growth and lipid accumulation of Chlorella pacifica were investigated in this study. The results showed
[...] Read more.
The impacts of laser radiation (Nd: YAG laser, 1064 nm at 800 mW, He–Ne laser 808 nm at 6 W, semiconductor laser 632.8 nm at 40 mW) on growth and lipid accumulation of Chlorella pacifica were investigated in this study. The results showed growth rates increased 1.23, 1.41, and 1.40-fold over controls by 4 min Nd: YAG, 4 min He–Ne, and 8 min semiconductor laser treatments, respectively, whereas the corresponding nitrate reductase observed increased 1.25, 1.63, and 2.08-fold over controls. Moreover, total chlorophyll concentration was increased to 1.09, 1.29, and 1.33-fold over controls, respectively. After 20 days cultivation, the highest lipid content was 35.99%, 18.46%, and 31.00% after 2 min Nd: YAG, 4 min He–Ne, and 4 min semiconductor laser treatments, corresponding to 2.86, 1.50, and 2.46-fold increase over controls, respectively. Furthermore, the lipid productivity of the above 3 treatments were 15.25 ± 2.56, 16.25 ± 2.45, and 14.75 ± 2.11 mg L−1 d−1. However, the highest lipid productivity was 22.00 ± 3.28, 16.25 ± 2.45, and 19.25 ± 1.78 mg L−1 d−1, in response to treatment for 2 min Nd: YAG, 1 min He–Ne, and 4 min semiconductor laser treatments, with 2.67, 1.97, and 2.33-fold increase over controls, respectively. These results indicated that lipid accumulation efficiency of C. pacifica could be significantly improved by laser irradiation using Nd: YAG, He–Ne, and semiconductor laser treatments. Full article
(This article belongs to the Section Energy Sources)
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Open AccessArticle An Improved Coordinated Control Strategy for PV System Integration with VSC-MVDC Technology
Energies 2017, 10(10), 1670; https://doi.org/10.3390/en10101670
Received: 14 September 2017 / Revised: 9 October 2017 / Accepted: 18 October 2017 / Published: 22 October 2017
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Abstract
The rapid development of renewable energy calls for feasible and reliable technologies to transmit and integrate power into grids. Voltage Source Converter (VSC)- Direct Current (DC) technology is considered as a promising solution for its independent control of active and reactive power. Modeling
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The rapid development of renewable energy calls for feasible and reliable technologies to transmit and integrate power into grids. Voltage Source Converter (VSC)- Direct Current (DC) technology is considered as a promising solution for its independent control of active and reactive power. Modeling and coordinated control of a large-scale concentrating photovoltaic integration system with VSC-MVDC (Voltage Source Converter-Medium Voltage Direct Current) technology have been investigated in this paper. The average controlled-source model of PhotoVoltaic (PV) integration system is firstly established. Then, a novel control strategy without fast communication is proposed to improve the reliability of the coordinated control system. An extra voltage loop is added to the basic control block, which is able to assure stable operation of the PV system in various conditions. Finally, the proposed control strategy is verified with simulation results. Full article
(This article belongs to the Section Electrical Power and Energy System)
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Open AccessArticle Learning-Based Adaptive Imputation Methodwith kNN Algorithm for Missing Power Data
Energies 2017, 10(10), 1668; https://doi.org/10.3390/en10101668
Received: 29 August 2017 / Revised: 15 October 2017 / Accepted: 17 October 2017 / Published: 21 October 2017
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Abstract
This paper proposes a learning-based adaptive imputation method (LAI) for imputing missing power data in an energy system. This method estimates the missing power data by using the pattern that appears in the collected data. Here, in order to capture the patterns from
[...] Read more.
This paper proposes a learning-based adaptive imputation method (LAI) for imputing missing power data in an energy system. This method estimates the missing power data by using the pattern that appears in the collected data. Here, in order to capture the patterns from past power data, we newly model a feature vector by using past data and its variations. The proposed LAI then learns the optimal length of the feature vector and the optimal historical length, which are significant hyper parameters of the proposed method, by utilizing intentional missing data. Based on a weighted distance between feature vectors representing a missing situation and past situation, missing power data are estimated by referring to the k most similar past situations in the optimal historical length. We further extend the proposed LAI to alleviate the effect of unexpected variation in power data and refer to this new approach as the extended LAI method (eLAI). The eLAI selects a method between linear interpolation (LI) and the proposed LAI to improve accuracy under unexpected variations. Finally, from a simulation under various energy consumption profiles, we verify that the proposed eLAI achieves about a 74% reduction of the average imputation error in an energy system, compared to the existing imputation methods. Full article
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Open AccessArticle Dynamic Modeling and Simulation of Deep Geothermal Electric Submersible Pumping Systems
Energies 2017, 10(10), 1659; https://doi.org/10.3390/en10101659
Received: 21 September 2017 / Revised: 10 October 2017 / Accepted: 13 October 2017 / Published: 21 October 2017
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Abstract
Deep geothermal energy systems employ electric submersible pumps (ESPs) in order to lift geothermal fluid from the production well to the surface. However, rough downhole conditions and high flow rates impose heavy strain on the components, leading to frequent failures of the pump
[...] Read more.
Deep geothermal energy systems employ electric submersible pumps (ESPs) in order to lift geothermal fluid from the production well to the surface. However, rough downhole conditions and high flow rates impose heavy strain on the components, leading to frequent failures of the pump system. As downhole sensor data is limited and often unrealible, a detailed and dynamical model system will serve as basis for deeper understanding and analysis of the overall system behavior. Furthermore, it allows to design model-based condition monitoring and fault detection systems, and to improve controls leading to a more robust and efficient operation. In this paper, a detailed state-space model of the complete ESP system is derived, covering the electrical, mechanical and hydraulic subsystems. Based on the derived model, the start-up phase of an exemplary yet realistic ESP system in the Megawatt range—located at a setting depth of 950 m and producing geothermal fluid of 140 C temperature at a rate of 0.145 m 3 s 1 —is simulated in MATLAB/Simulink. The simulation results show that the system reaches a stable operating point with realistic values. Furthermore, the effect of self-excitation between the filter capacitor and the motor inductor can clearly be observed. A full set of parameters is provided, allowing for direct model implementation and reproduction of the presented results. Full article
(This article belongs to the Special Issue Low Enthalpy Geothermal Energy)
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