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Records Added in January 2019
Records added in January 2019
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Showing records 76 to 100 of 220. [First] Page: 1 2 3 4 5 6 7 8 Last
A Novel Dynamic Co-Simulation Analysis for Overall Closed Loop Operation Control of a Large Wind Turbine
Ching-Sung Wang, Mao-Hsiung Chiang
January 30, 2019 (v1)
Keywords: co-simulation, dynamic simulation, generator torque control, pitch control, wind turbine, yaw control
A novel dynamic co-simulation methodology of overall wind turbine systems is presented. This methodology combines aerodynamics, mechanism dynamics, control system dynamics, and subsystems dynamics. Aerodynamics and turbine properties were modeled in FAST (Fatigue, Aerodynamic, Structures, and Turbulence), and ADAMS (Automatic Dynamic Analysis of Mechanical Systems) performed the mechanism dynamics; control system dynamics and subsystem dynamics such as generator, pitch control system, and yaw control system were modeled and built in MATLAB/SIMULINK. Thus, this comprehensive integration of methodology expands both the flexibility and controllability of wind turbines. The dynamic variations of blades, rotor dynamic response, and tower vibration can be performed under different inputs of wind profile, and the control strategies can be verified in the different closed loop simulation. Besides, the dynamic simulation results are compared with the measuring results of SCADA (Supervisory Cont... [more]
Estimation of Total Transport CO₂ Emissions Generated by Medium- and Heavy-Duty Vehicles (MHDVs) in a Sector of Korea
Jigu Seo, Junhong Park, Yunjung Oh, Sungwook Park
January 30, 2019 (v1)
Subject: Energy Policy
Keywords: carbon dioxide emission inventory, carbon dioxide emissions, medium and heavy-duty vehicle (MHDV), vehicle simulation
In order to mitigate carbon dioxide (CO₂) emissions, policy action that addresses vehicle emissions is essential. While many previous studies have focused on light-duty vehicles (LDV), little is known about medium- and heavy-duty vehicles (MHDV). This study lays the groundwork for future MHDV investigations in the Republic of Korea by developing an MHDV CO₂ emissions inventory. The bottom-up approach was used to calculate national CO₂ emissions. Simulation methods that calculated the CO₂ emissions of each vehicle and statistical data, such as vehicle miles traveled (VMT) and the number of registered vehicles were used to predict CO₂ emissions. The validity of this simulation model was examined by comparing it with the chassis dynamometer test results. The results of this study showed that the CO₂ emissions of MHDV in 2015 were 24.47 million tons, which was 25.5% of the total road transportation CO₂ emissions, despite only comprising 4.2% of the total vehicles. Trucks emitted 69.6% and... [more]
Design and Implementation of a Test-Bench for Efficiency Measurement of Domestic Induction Heating Appliances
Javier Serrano, Jesús Acero, Rafael Alonso, Claudio Carretero, Ignacio Lope, José Miguel Burdío
January 30, 2019 (v1)
Keywords: efficiency measurement, efficient power transfer, induction heating, measurement station
The operation of a domestic induction cooktop is based on the wireless energy transfer from the inductor to the pot. In such systems, the induction efficiency is defined as the ratio between the power delivered to the pot and the consumed power from the supplying converter. The non-transferred power is dissipated in the inductor, raising its temperature. Most efficiency-measuring methods are based on measuring the effective power (pot) and the total power (converter output). While the converter output power is directly measurable, the measurement of the power dissipation in the pot is usually a cause of inaccuracy. In this work, an alternative method to measure the system’s efficiency is proposed and implemented. The method is based on a pot with a reversible base to which the inductor is attached. In the standard configuration, the inductor is placed below the pot in such a way that the delivered power is used to boil water, and the power losses are dissipated to the air. When the pot... [more]
Lignocellulosic Ethanol Production from the Recovery of Stranded Driftwood Residues
Gianluca Cavalaglio, Mattia Gelosia, Silvia D’Antonio, Andrea Nicolini, Anna Laura Pisello, Marco Barbanera, Franco Cotana
January 30, 2019 (v1)
Subject: Biosystems
Keywords: bioethanol, cellulose hydrolysis, steam explosion, stranded driftwood residues
This paper builds upon a research project funded by the Italian Ministry of Environment, and aims to recover stranded driftwood residues (SDRs), in order to transform a potential pollution and safety issue into valuable bio-resources. In particular, one of the experiments consisted of bioethanol production from lignocellulosic residues. The SDRs were gathered from the Italian coast (Abruzzo Region, Italy) after an intense storm. The biomass recalcitrance, due to its lignocellulosic structure, was reduced by a steam explosion (SE) pretreatment process. Four different pretreatment severity factors (R₀) were tested (LogR₀ 3.65, 4.05, 4.24 and 4.64) in order to evaluate the pretreated material’s accessibility to enzymatic attack and the holocellulose (cellulose plus hemicellulose) recovery. A first enzymatic hydrolysis was performed on the pretreated materials by employing a solid/liquid (S/L) ratio of 1% (w/w) and an enzyme dosage of 30% (w enzyme/w cellulose), in order to estimate the ma... [more]
Dispatching of Wind/Battery Energy Storage Hybrid Systems Using Inner Point Method-Based Model Predictive Control
Deyou Yang, Jiaxin Wen, Ka-wing Chan, Guowei Cai
January 30, 2019 (v1)
Keywords: battery energy storage, combination active output, dispatching curve, wind power
The application of large scale energy storage makes wind farms more dispatchable, which lowers operating risks to the grid from interconnected large scale wind farms. In order to make full use of the flexibility and controllability of energy storage to improve the schedulability of wind farms, this paper presents a rolling and dispatching control strategy with a battery energy storage system (BESS) based on model predictive control (MPC). The proposed control scheme firstly plans expected output, i.e., dispatching order, of a wind/battery energy storage hybrid system based on the predicted output of the wind farm, then calculates the order in the predictive horizon with the receding horizon optimization and the limitations of energy storage such as state of charge and depth of charge/discharge to maintain the combination of active output of the wind farm and the BESS to track dispatching order at the extreme. The paper shows and analyses the effectiveness of the proposed strategy with... [more]
TBM/MTM for HTS-FNSF: An Innovative Testing Strategy to Qualify/Validate Fusion Technologies for U.S. DEMO
Laila El-Guebaly, Arthur Rowcliffe, Jonathan Menard, Thomas Brown
January 30, 2019 (v1)
Subject: Energy Policy
Keywords: fusion nuclear testing facility, high temperature superconducting magnets, materials testing module, spherical tokamak, testing blanket module, testing strategy
The qualification and validation of nuclear technologies are daunting tasks for fusion demonstration (DEMO) and power plants. This is particularly true for advanced designs that involve harsh radiation environment with 14 MeV neutrons and high-temperature operating regimes. This paper outlines the unique qualification and validation processes developed in the U.S., offering the only access to the complete fusion environment, focusing on the most prominent U.S. blanket concept (the dual cooled PbLi (DCLL)) along with testing new generations of structural and functional materials in dedicated test modules. The venue for such activities is the proposed Fusion Nuclear Science Facility (FNSF), which is viewed as an essential element of the U.S. fusion roadmap. A staged blanket testing strategy has been developed to test and enhance the DCLL blanket performance during each phase of FNSF D-T operation. A materials testing module (MTM) is critically important to include in the FNSF as well to... [more]
Methodologies Developed for EcoCity Related Projects: New Borg El Arab, an Egyptian Case Study
Carmen Antuña-Rozado, Justo García-Navarro, Francesco Reda, Pekka Tuominen
January 30, 2019 (v1)
Subject: Energy Policy
Keywords: CO2 emissions, EcoCity, EcoCity methodologies, Egypt, Energy Efficiency, energy survey, feasibility study, roadmap, sustainability scenarios
The aim of the methodologies described here is to propose measures and procedures for developing concepts and technological solutions, which are adapted to the local conditions, to build sustainable communities in developing countries and emerging economies. These methodologies are linked to the EcoCity framework outlined by VTT Technical Research Centre of Finland Ltd. for sustainable community and neighbourhood regeneration and development. The framework is the result of a long experience in numerous EcoCity related projects, mainly Nordic and European in scope, which has been reformulated in recent years to respond to the local needs in the previously mentioned countries. There is also a particular emphasis on close collaboration with local partners and major stakeholders. In order to illustrate how these methodologies can support EcoCity concept development and implementation, results from a case study in Egypt will be discussed. The referred case study relates to the transformatio... [more]
Coordinated Scheme of Under-Frequency Load Shedding with Intelligent Appliances in a Cyber Physical Power System
Qi Wang, Yi Tang, Feng Li, Mengya Li, Yang Li, Ming Ni
January 30, 2019 (v1)
Keywords: cyber physical power system, demand response, intelligent home appliance, under-frequency load shedding
The construction of a cyber physical system in a power grid provides more potential control strategies for the power grid. With the rapid employment of intelligent terminal equipment (e.g., smart meters and intelligent appliances) in the environment of a smart grid, abundant dynamic response information could be introduced to support a secure and stable power system. Combining demand response technology with the traditional under-frequency load shedding (UFLS) scheme, a new UFLS strategy-determining method involving intelligent appliances is put forward to achieve the coordinated control of quick response resources and the traditional control resources. Based on this method, intelligent appliances can be used to meet the regulatory requirements of system operation in advance and prevent significant frequency drop, thereby improving the flexibility and stability of the system. Time-domain simulation verifies the effectiveness of the scheme, which is able to mitigate frequency drop and r... [more]
Techno-Economic Modeling and Analysis of Redox Flow Battery Systems
Jens Noack, Lars Wietschel, Nataliya Roznyatovskaya, Karsten Pinkwart, Jens Tübke
January 30, 2019 (v1)
Keywords: cost, materials, redox flow battery, Technoeconomic Analysis
A techno-economic model was developed to investigate the influence of components on the system costs of redox flow batteries. Sensitivity analyses were carried out based on an example of a 10 kW/120 kWh vanadium redox flow battery system, and the costs of the individual components were analyzed. Particular consideration was given to the influence of the material costs and resistances of bipolar plates and energy storage media as well as voltages and electric currents. Based on the developed model, it was possible to formulate statements about the targeted optimization of a developed non-commercial vanadium redox flow battery system and general aspects for future developments of redox flow batteries.
Perspectives on Near ZEB Renovation Projects for Residential Buildings: The Spanish Case
Faustino Patiño-Cambeiro, Julia Armesto, Faustino Patiño-Barbeito, Guillermo Bastos
January 30, 2019 (v1)
Subject: Energy Policy
Keywords: buildings, cost-optimal, Energy Efficiency, nZEB, renovation
EU regulations are gradually moving towards policies that reduce energy consumption and its environmental impact. To reach this goal, improving energy efficiency in residential buildings is a key action line. The European Parliament adopted the Near Zero-Energy Building (nZEB) as the energy efficiency paradigm through Directive 2010/31/EU, but a common technical and legislative framework for energy renovations is yet to be established. In this paper, the nZEB definition by COHERENO was adopted to evaluate several energy renovation packages in a given building, which is also representative of the Spanish building stock. Global costs are calculated for all of them following EPBD prescriptions. Two economic scenarios are analysed: with entirely private funding and with the current public financial incentives, respectively. The results show the divergence between optimum solutions in terms of costs and of minimum CO₂ footprint and maximum energy saving. Moreover, in the absence of enough i... [more]
Energy Optimization for Train Operation Based on an Improved Ant Colony Optimization Methodology
Youneng Huang, Chen Yang, Shaofeng Gong
January 30, 2019 (v1)
Subject: Optimization
Keywords: ant colony optimization, CBTC, discrete combination, optimization of energy-savings
More and more lines are using the Communication Based Train Control (CBTC) systems in urban rail transit. Trains are operated by tracking a pre-determined target speed curve in the CBTC system, so one of the most effective ways of reducing energy consumption is to fully understand the optimum curves that should prevail under varying operating conditions. Additionally, target speed curves need to be calculated with optimum real-time performance in order to cope with changed interstation planning running time. Therefore, this paper proposes a fast and effective algorithm for optimization, based on a two-stage method to find the optimal curve using a max-min ant colony optimization system, using approximate calculations of a discrete combination optimization model. The first stage unequally discretizes the line based on static gradient and speed limit in low-density and it could conduct a comprehensive search for viable energy saving target speed curves. The second stage unequally discret... [more]
Activity-Aware Energy-Efficient Automation of Smart Buildings
Brian L. Thomas, Diane J. Cook
January 30, 2019 (v1)
Keywords: activity prediction, activity recognition, building automation, cyber-physical systems (CPS), smart cities
This paper introduces the idea of activity-aware cyber-physical systems (CPS). Activity-aware systems allow smart city services to adapt to the needs of individual residents by being sensitive to their daily tasks. The paper first defines activity recognition and activity prediction algorithms that form the foundation of activity-aware CPS and implement a prototype activity-aware building automation system, called CASAS activity aware resource learning (CARL). Evaluation of CARL on real sensor data shows not only an accurate ability to sense and predict activities but an effective means of automation buildings that reduces energy consumption while being sensitive to user activities in the building. Our ideas are demonstrated in the context of a smart home but can be utilized in a variety of smart city settings including smart offices, smart hospitals, and smart communities.
Partial Discharge Measurement under an Oscillating Switching Impulse: A Potential Supplement to the Conventional Insulation Examination in the Field
Ming Ren, Ming Dong, Chongxing Zhang, Jierui Zhou
January 30, 2019 (v1)
Keywords: gas insulated switchgear, impulse voltage, insulation diagnosis, partial discharge, power apparatus, SF6
Partial discharge (PD) detection under oscillating switching impulse (OSI) voltage was performed on three types of insulation defects, including a protrusion on a conductor, a particle on an insulator surface, and a void in an insulator, which are three kinds of the common potential insulation hazards in gas insulated power apparatus. Experiment indicated that the PD sequences under OSI were composed of various combinations of the single pulse, the multiple pulses, and the reverse polarity pulse. The difference between the PD inception voltage (PDIV) and the breakdown voltage (BDV) under OSI voltage was greater than that under alternating current (AC) voltage in some cases, which can provide a more sufficient margin below the BDV for PD diagnosis. The OSI voltage also showed a better performance for exciting PDs with detectable magnitudes from small-scale defects, of which the AC voltage was incapable under our test conditions. The different PD activities with different interfaces unde... [more]
Offshore Power Plants Integrating a Wind Farm: Design Optimisation and Techno-Economic Assessment Based on Surrogate Modelling
Luca Riboldi, Lars O. Nord
January 17, 2019 (v1)
Keywords: combined cycle, hybrid system, kriging, multi-objective optimisation, offshore wind, oil and gas
The attempt to reduce the environmental impact of the petroleum sector has been the driver for researching energy efficient solutions to supply energy offshore. An attractive option is to develop innovative energy systems including renewable and conventional sources. The paper investigates the possibility to integrate a wind farm into an offshore combined cycle power plant. The design of such an energy system is a complex task as many, possibly conflicting, requirements have to be satisfied. The large variability of operating conditions due to the intermittent nature of wind and to the different stages of exploitation of an oil field makes it challenging to identify the optimal parameters of the combined cycle and the optimal size of the wind farm. To deal with the issue, an optimisation procedure was developed that was able to consider the performance of the system at a number of relevant off-design conditions in the definition of the optimal design. A surrogate modelling technique wa... [more]
Offshore Power Plants Integrating a Wind Farm: Design Optimisation and Techno-Economic Assessment Based on Surrogate Modelling
Luca Riboldi, Lars O. Nord
January 17, 2019 (v2)
Keywords: combined cycle, hybrid system, kriging, multi-objective optimisation, offshore wind, oil and gas
The paper investigates the possibility to integrate a wind farm into an offshore combined cycle power plant. The models used in the publication are here provided.
The Energy and Environmental Performance of Ground-Mounted Photovoltaic Systems—A Timely Update
Enrica Leccisi, Marco Raugei, Vasilis Fthenakis
January 7, 2019 (v1)
Subject: Energy Policy
Keywords: cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), crystalline Si (c-Si), energy pay-back time (EPBT), energy return on investment (EROI), environmental performance, life cycle assessment (LCA), net energy analysis (NEA), photovoltaic (PV)
Given photovoltaics’ (PVs) constant improvements in terms of material usage and energy efficiency, this paper provides a timely update on their life-cycle energy and environmental performance. Single-crystalline Si (sc-Si), multi-crystalline Si (mc-Si), cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) systems are analysed, considering the actual country of production and adapting the input electricity mix accordingly. Energy pay-back time (EPBT) results for fixed-tilt ground mounted installations range from 0.5 years for CdTe PV at high-irradiation (2300 kWh/(m²·yr)) to 2.8 years for sc-Si PV at low-irradiation (1000 kWh/(m²·yr)), with corresponding quality-adjusted energy return on investment (EROIPE-eq) values ranging from over 60 to ~10. Global warming potential (GWP) per kWhel averages out at ~30 g(CO₂-eq), with lower values (down to ~10 g) for CdTe PV at high irradiation, and up to ~80 g for Chinese sc-Si PV at low irradiation. In general, results point to CdTe... [more]
Automated Variable Selection and Shrinkage for Day-Ahead Electricity Price Forecasting
Bartosz Uniejewski, Jakub Nowotarski, Rafał Weron
January 7, 2019 (v1)
Keywords: autoregression, day-ahead market, elastic net, electricity price forecasting, lasso, ridge regression, stepwise regression, variable selection
In day-ahead electricity price forecasting (EPF) variable selection is a crucial issue. Conducting an empirical study involving state-of-the-art parsimonious expert models as benchmarks, datasets from three major power markets and five classes of automated selection and shrinkage procedures (single-step elimination, stepwise regression, ridge regression, lasso and elastic nets), we show that using the latter two classes can bring significant accuracy gains compared to commonly-used EPF models. In particular, one of the elastic nets, a class that has not been considered in EPF before, stands out as the best performing model overall.
Hysteresis Characteristic in the Hump Region of a Pump-Turbine Model
Deyou Li, Hongjie Wang, Jinxia Chen, Torbjørn K. Nielsen, Daqing Qin, Xianzhu Wei
January 7, 2019 (v1)
Keywords: experimental investigation, hump characteristic, hysteresis characteristic, pump turbine
The hump feature is one of the major instabilities in pump-turbines. When pump-turbines operate in the hump region, strong noise and serious fluctuations can be observed, which are harmful to their safe and stable operation and can even destroy the whole unit as well as water conveyance system. In this paper, a low specific speed (nq = 36.1 min−1) pump-turbine model was experimentally investigated. Firstly, the hump characteristic was obtained under 19 mm guide vane opening conditions. More interestingly, when the hump characteristic was measured in two directions (increasing and decreasing the discharge), characteristic hysteresis was found in the hump region. The analysis of performance characteristics reveals that the hump instability is the result of Euler momentum and hydraulic losses, and different Euler momentum and hydraulic losses in the two development processes lead to the hysteresis phenomenon. Then, 12 pressure sensors were mounted in the different parts of the pump-turbin... [more]
A Hybrid Multi-Step Model for Forecasting Day-Ahead Electricity Price Based on Optimization, Fuzzy Logic and Model Selection
Ping Jiang, Feng Liu, Yiliao Song
January 7, 2019 (v1)
Keywords: forecasting, fuzzy logic, particle swarm optimization (PSO), reducing volatility, selection rule (SR), self-organizing-map
The day-ahead electricity market is closely related to other commodity markets such as the fuel and emission markets and is increasingly playing a significant role in human life. Thus, in the electricity markets, accurate electricity price forecasting plays significant role for power producers and consumers. Although many studies developing and proposing highly accurate forecasting models exist in the literature, there have been few investigations on improving the forecasting effectiveness of electricity price from the perspective of reducing the volatility of data with satisfactory accuracy. Based on reducing the volatility of the electricity price and the forecasting nature of the radial basis function network (RBFN), this paper successfully develops a two-stage model to forecast the day-ahead electricity price, of which the first stage is particle swarm optimization (PSO)-core mapping (CM) with self-organizing-map and fuzzy set (PCMwSF), and the second stage is selection rule (SR).... [more]
Some Models for Determination of Parameters of the Soil Oscillation Law during Blasting Operations
Suzana Lutovac, Dragan Medenica, Branko Gluščević, Rade Tokalić, Čedomir Beljić
January 7, 2019 (v1)
Keywords: blasting, oscillation velocity, seismic effect, soil oscillation law, working environment
In order to evaluate and control the seismic effect of blasting, as well as its planning, it is required to determine the soil oscillation law, with the strike/mining facilities to be protected. One of the most commonly used equations is that of M.A. Sadovskii, defining the law of alteration in the oscillation velocity of the soil depending on distance, the explosive amount, and conditions of blasting and geologic characteristics of the soil; all of this being determined on the basis of test blasting for the specific work environment. In the Sadovskii equation two parameters, K and n appear and they are conditioned both by rock mass characteristics and blasting conditions. The practical part of this study includes experimental investigations performed in the Veliki Krivelj Open Pit in the Bor District located in Eastern Serbia and investigations carried out during mass mining in the Kovilovača Open Pit near Despotovac, Eastern Serbia. Thus this paper offers several modes for determinat... [more]
Sustainable New Brick and Thermo-Acoustic Insulation Panel from Mineralization of Stranded Driftwood Residues
Anna Laura Pisello, Claudia Fabiani, Nastaran Makaremi, Veronica Lucia Castaldo, Gianluca Cavalaglio, Andrea Nicolini, Marco Barbanera, Franco Cotana
January 7, 2019 (v1)
Subject: Materials
Keywords: bio-based composite, Biomass, building envelope, energy efficiency in buildings, environmental sustainability, stranded driftwood residues, thermal and acoustical properties
There is considerable interest recently in by-products for application in green buildings. These materials are widely used as building envelope insulators or blocks. In this study, an experimental study was conducted to test stranded driftwood residues as raw material for possible thermo-acoustic insulation panel and environmentally sustainable brick. The thermal and acoustic characteristics of such a natural by-product were examined. Part of samples were mineralized by means of cement-based additive to reinforce the material and enhance its durability as well as fire resistance. Several mixtures with different sizes of ground wood chips and different quantities of cement were investigated. The thermo-acoustic in-lab characterization was aimed at investigating the thermal conductivity, thermal diffusivity, volumetric specific heat, and acoustic transmission loss. All samples were tested before and after mineralization. Results from this study indicate that it is possible to use strande... [more]
DG Mix and Energy Storage Units for Optimal Planning of Self-Sufficient Micro Energy Grids
Aboelsood Zidan, Hossam A. Gabbar
January 7, 2019 (v1)
Keywords: combined heat and power, gas-power, Genetic Algorithm, micro energy grid, multi-objective, renewable, self-sufficient
Micro energy grids have many merits and promising applications under the smart grid vision. There are demanding procedures for their optimal planning and performance enhancement. One of the key features of a micro energy grid is its ability to separate and isolate itself from the main electrical network to continue feeding its own islanded portion. In this paper, an optimal sizing and operation strategy for micro energy grids equipped with renewable and non-renewable based distributed generation (DG) and storage are presented. The general optimization objective is to define the best DG mix and energy storage units for self-sufficient micro energy grids. A multi-objective genetic algorithm (GA) was applied to solve the planning problem at a minimum optimization goal of overall cost (including investment cost, operation and maintenance cost, and fuel cost) and carbon dioxide emission. The constraints include power and heat demands constraints, and DGs capacity limits. The candidate techn... [more]
Exploring Reduction Potential of Carbon Intensity Based on Back Propagation Neural Network and Scenario Analysis: A Case of Beijing, China
Jinying Li, Jianfeng Shi, Jinchao Li
January 7, 2019 (v1)
Keywords: Beijing, carbon intensity, IPSO model, scenario analysis
Carbon emissions are the major cause of the global warming; therefore, the exploration of carbon emissions reduction potential is of great significance to reduce carbon emissions. This paper explores the potential of carbon intensity reduction in Beijing in 2020. Based on factors including economic growth, resident population growth, energy structure adjustment, industrial structure adjustment and technical progress, the paper sets 48 development scenarios during the years 2015⁻2020. Then, the back propagation (BP) neural network optimized by improved particle swarm optimization algorithm (IPSO) is used to calculate the carbon emissions and carbon intensity reduction potential under various scenarios for 2016 and 2020. Finally, the contribution of different factors to carbon intensity reduction is compared. The results indicate that Beijing could more than fulfill the 40%⁻45% reduction target for carbon intensity in 2020 in all of the scenarios. Furthermore, energy structure adjustment... [more]
Comparison of Organic Rankine Cycle Systems under Varying Conditions Using Turbine and Twin-Screw Expanders
Matthew Read, Ian Smith, Nikola Stosic, Ahmed Kovacevic
January 7, 2019 (v1)
Keywords: expander, geothermal, Organic Rankine Cycle, turbine, twin screw, waste heat
A multi-variable optimization program has been developed to investigate the performance of Organic Rankine Cycles (ORCs) for low temperature heat recovery applications using both turbine and twin-screw expanders when account is taken of performance variation due to changes in ambient conditions. The cycle simulation contains thermodynamic models of both types of expander. In the case of the twin-screw machine, the methods used to match the operation of the expander to the requirements of the cycle are described. The performance of turbine expanders in a superheated ORC has been modelled using correlations derived from operational data for single stage reaction turbines to predict the turbine efficiency at “off-design” conditions. Several turbine configurations have been considered including variable nozzle area and variable speed. The capability of the cycle model has been demonstrated for the case of heat recovery from a steady source of pressurized hot water at 120 °C. The system par... [more]
Contribution of Geothermal Resources to Energy Autonomy: Evaluation and Management Methodology
Liliana Topliceanu, Gabriel Petru Puiu
January 7, 2019 (v1)
Subject: Energy Policy
Keywords: energy autonomy, geothermal, heating, methodology, Romania
The development of renewable energy is one of the aspirations of the European Union energy policy, being generated by the struggle against climatic changes and by the intention of achieving a high rate of energy autonomy. In this context, geothermal energy is a viable solution which has been little exploited so far. Analysing the EU’s dependence on imported energy, the paper provides a short review of the utilization of geothermal energy, of the advantages and of the problems raised by the exploitation of this resource. It also analyzes the availability of this resource in Romania and the contribution it can have towards the energy autonomy of local communities. The paper presents a particular methodology for calculating the energy autonomy. Using this methodology, one can obtain an energetic overview of the community or the area analyzed, can calculate the degree of energy autonomy and, based on the results achieved, a sustainable development strategy can be designed. The low enthalpy... [more]
Showing records 76 to 100 of 220. [First] Page: 1 2 3 4 5 6 7 8 Last
Change year: 2018 | 2019
Change month: January | February | March | April | May | June | July