Maximum Power Generation Research Articles

State space model of an array of oscillating water column wave energy converters with inter-body hydrodynamic coupling

In this paper we derive a state-space model restricted to heave motion of a full scale array of floating oscillating-water-column (OWC) wave energy converters with nonlinear power take off dynamics, taking hydrodynamic interactions between all bodies into account. The resulting state-space model is intended as a basis for accelerated development of advanced control approaches to maximize power generation. The kinetic and potential energy transferred to the air chamber causes a pressure difference, inducing unidirectional motion of a novel bi-radial turbine. This can be accurately modeled using pressure dependent turbine characteristics, taking into account the nonlinearity of the gas compressibility. The analytical model of the floating OWC is based on linear hydrodynamic coefficients, obtained using the boundary element solver ANSYS Aqwa of an equilateral triangle array of axis-symmetric floating OWCs of the Marmok-A-5 type. Finally, the system’s model time domain equations are simulated in different wave climates and an ideal active controller is applied to maximize energy conversion. For the specific implemented separation distance the resulting cross body interactions are found to be negligible in irregular compared to regular wave scenarios. The turbine rotational speed suggests investigations on discontinues nonlinear control methods before semi-global approaches are used to optimize power generation.

Technologies of geothermal resources development in South of Russia

A technology has been proposed for the integrated development of low-temperature geothermal resources for using their thermal and water potentials for various purposes. The possibility is substantiated for efficient development of geothermal resources by construction of binary geothermal power plants (GeoPP) using idle oil and gas wells that will significantly reduce capital investments for their building. The East Ciscaucasian artesian basin situated in the South European part of Russia has a number of fields with idle wells that can be converted to thermal water production. Involving the entire fund of idle wells will make it possible to obtain up to 300 MW of summary net capacity at a geothermal power plant. This work proposes a deployment of hybrid technology of geothermal power plant coupled with combined cycle plant of gas turbine type (further GCP) for the effective utilization of medium-temperature thermal waters (80–100 °C). These technologies are shown to be promising for using such water for electricity generating with high efficiency. A comparative analysis was carried out for GeoPP and GCP operating on medium-temperature water, which has shown the advantage of the latter. According to the calculations, the implementation of hybrid technology at the Thernair field in Makhachkala town will make it possible to get a power plant capacity of up to 60 MW. The prospects of integrated processing of high-temperature geothermal brines are shown. The technological diagrams are presented where the electricity generated at a binary GeoPP is used in the unit for the chemical components extraction. The estimated parameters for the Berikey geothermal field are given. The proven reserves of the Berikey field thermal brines are shown to be promising for output more than 2000 tons of lithium carbonate annually. The prospects of integrated processing of high-temperature geothermal brines in the Tarumovka geothermal field have been presented. The thermal energy of the geothermal brine can be converted into electricity in a binary geothermal power plant using a low-boiling working agent. The Rankine thermodynamic cycles have been considered realized in the secondary circuit of the GeoPP at different temperatures of evaporation of the working agent isobutane. The most effective in terms of maximum power generation is a supercritical cycle, close to the so-called “triangular” cycle with an evaporation pressure pe = 5.0 MPa. The spent brine with a low temperature from the GeoPP will go to a chemical plant, where the main chemical components, namely, lithium carbonate, magnesia, calcium carbonate and sodium chloride will be extracted according to the developed by us technology for the integrated utilization of hydrothermal brines. For the production of valuable inorganic materials, the electricity generated at the GeoPP may be applied. The need is shown in the priority integrated processing the associated highly saline brines of the Yuzhno-Sukhokumsk group of oil and gas wells in Northern Dagestan. At present, the associated brines with a radioactive background exceeding permissible standards are dumped onto surface filtration fields. Technological solutions for their decontamination and development have been proposed.

Transfer of P-type to N-type Thermoelectric Properties of Ag-Sb-Te Thin Film Through Temperature Annealing and Its Electrical Power Generation

Ag-Sb-Te (AST) thin film was successfully fabricated on a flexible polyimide substrate by using DC magnetron sputtering from the AgSbTe (AST) target. As-deposited samples were annealed at temperatures between 300 and 450°C under vacuum for 30 min. Then, uni-leg AST thin film thermoelectric modules of five elements were fabricated. Thermal annealing induced a change of thermoelectric characteristic of the thin film from p-type material (300–350°C) to n-type material (400–450°C) through the change in structures (amorphous to crystalline, atomic composition ratio and surface roughness, etc.). The highest power factor was 0.97 mW m−1 K−2 and 0.065 mW m−1 K−2 for p-type and n-type, respectively. The maximum power generation of the uni-leg AST thin film thermoelectric module was approximately 0.88 nW for p-type and 0.54 nW for n-type, with a temperature difference of around 20 K.

A Design of Standalone Hybrid PV/Wind/Fuel cell Generation System and Hydrogen Electrolyzer With Local Controller for Remote Areas

Integration of fuel cell and electrolyzer on DC bus is a promising alternative to solve voltage fluctuation and balance of power problems in a standalone hybrid renewable power generation systems. The hybrid renewable power generation systems consist of photovoltaic, wind turbine, fuel cell and hydrogen electrolyzer. Each the component integrated on DC bus through the converter DC – DC using local controller to supply the inverter which connected to the islanded load. Local controller in each part will make the system become flexible if there are additional generating units in the future. The local control methods used in this hybrid renewable power generation system is MPPT and constant voltage control. MPPT control applied to photovoltaic and wind turbine converters to maximize power generation from photovoltaic and wind turbine. Constant voltage controller applied to the fuel cell and electrolyzer converters to control the DC bus voltage alternately. This research is a new design system for remote areas by utilizing the potensial of renewable energy in the area. The result show the power quality and continuity of electricity services.

Microalgae as a biocathode and feedstock in anode chamber for a self-sustainable microbial fuel cell technology: A review

Microbial fuel cell (MFC) technology has been investigated for over a decade now and it has been deemed as a preferred technique for energy generation since it is environmentally benign and does not produce toxic by/end products. However, this technology is characterized by low power outputs, poor microbial diversity detection, and the presence of methanogenic microorganisms, poor electrochemically active microorganisms’ enrichment techniques, and the type of electrode that is used, amongst others. Furthermore, this technology has relied mostly on refined chemicals for energy production and this practice is not sustainable for long-term application of this technology. This paper reviews the use of a microalgae-assisted MFC for a self-sustainable microbial fuel cell where a microalgae-assisted cathode is established to facilitate the oxidation/reduction reactions (ORR) while recycling the generated algal biomass to the anode compartment as a feedstock for improved energy generation. Furthermore, this review proposes for the utilization of cell disruption techniques to maximize nutrient availability for maximal power generation while also making use of molecular diagnostic tools such as metagenomics and metatranscriptomics to monitor the microbial community structure and function.

System Identification of a Solar Maximum Power Point Tracking System for Dual Axis

The project is on Maximum efficiency of a solar panel. As the sun is not constant at one place and by fixing the solar array at one place, maximum power generation is not possible. This project develops a solar power generation system using maximum power point tracking system. More direct sun light on Photovoltaic (PV) modules leads to enhanced energy yield. Therefore, tracking systems are implemented to improve the performance of PV system by tracking sun trajectory. The current design of Maximum Power Point Tracking (MPPT) trackers are more efficient than conventional single state solar power generation. Then by comparing two designs initially produced, Maximum Power Point Tracking (MPPT) tracking devices are found to be at better efficiency than static models. The system locates maximum- power generating point using an MPPT controller. The base line results of this study were obtained via physical implementation of simulated system to analyze the various parameters. The system then uses a quadratic-equation based algorithm that calculates the quadratic function corresponding to the maximum power generation point. With the advent of different applications of PV solar power, system planners have been implementing different strategies and techniques to maximize the output of solar system with commonly available technology in market. Additionally, various mathematical techniques were utilized to analyze the results gathered from the physical implementation. The simulation results also implemented to compare between the hardware and software of the project. The comparison of static Photovoltaic output graphs with real time measured values for the systems and a Dynamic Photovoltaic Maximum power point Solar Tracker (MPPT) system was observed. Both PV systems were implemented practically to get appropriate results and mainly all the equipment and services utilized in installation are widely available in local market.

Power Optimization of wind energy conversion system using T-S Fuzzy approach

This paper presents a maximum power point tracking control for a wind energy conversion system (WECS) using a squirrel cage induction generator (SCIG) which supplies a DC load through AC/DC converter. The goal of the developed fuzzy control law is to track the reference signals corresponding to the maximum power generation that leads to an optimal operation of the induction generator. First, the dynamics behaviour of the WECS is represented by a Takagi-Sugeno (T-S) fuzzy model. Then, a H∞ observer-based fuzzy controller is proposed to achieve a maximum power point tracking even when we consider a varying wind speed profile. The controller and observer gains are calculated by solving linear matrix inequalities (LMIs). Finally, simulation results are presented to illustrate the effectiveness of the proposed approach.

An experimentally validated, energy focused, optimal control strategy for an Organic Rankine Cycle waste heat recovery system

This paper presents a Nonlinear Model Predictive Controller (NMPC) designed to provide optimal control input for maximum turbine power generation in an Organic Rankine Cycle (ORC) Waste Heat Recovery (WHR) system. While the literature is rich in ORC-WHR system modeling and control approaches in simulation environments, the fundamental dynamic analysis, system aging, thermal inertia, and experimental implementation of power optimization based optimal ORC-WHR control are still lacking. These factors are key to fully understanding and controlling the dynamic behavior of the system and are the main focus of this study. In contrast to prior literature, this work experimentally evaluates the nonlinear dynamics of the ORC system to comprehensively understand the controller design requirements. A power optimization-based Nonlinear Model Predictive Controller (NMPC) is derived utilizing an Extended Kalman Filter (EKF) as a state estimator. Simulation results indicate that optimal turbine power generation is obtained with minimal working fluid superheat for the system under study. Consequently, a superheat-tracking controller is designed, and the performance of the controller is simulated over step inputs. The designed controller is then experimentally validated on an ORC test rig with a 13L Heavy Duty Diesel Engine (HDDE).During experimental evaluation of the controller, it was discovered that the control-oriented model is susceptible to system aging effects and therefore, the model was calibrated online to match the behavior of the aged system. Moreover, evaporator thermal inertia was found to play a vital role attenuating the fluctuating frequency components of the exhaust conditions. The tuned controller provided satisfactory control response for transient engine conditions and maintained the working fluid temperature within acceptable limits.

Performance Evaluation and Prediction of BIPV Systems under Partial Shading Conditions Using Normalized Efficiency

The performance of the Operable Building Integrated Photovoltaic (OBIPV) system applied to the building envelope to reduce the building energy consumption varies significantly depending on the operation method and influence of the surrounding environment. Therefore, optimization through performance monitoring is necessary to maximize power generation of the system. This study used temperature-corrected normalized efficiency (NE*) to evaluate the power generation performance of the operation methods and predict that of the OBIPV system based upon the measured data. It was confirmed that power generation performance decreased when the photovoltaic (PV) operation angle changed, the system remaining the same. A decrease in power generation performance due to partial shading from an overhang was also observed. As a result of the power generation prediction for two months using NE*, the error of the measured values was found to be less than 3%. In addition, with or without any partial shading of the OBIPV system, its performance degradation was predicted with an annual electricity generation decrease by 36 kWh/yr (6.5%). Therefore, NE* can be used as an indicator for evaluating the power generation performance of PV systems, and to predict generation performance considering partial shading.

Sensorless SynRG Based Variable Speed Wind Generator and Single-Stage Solar PV Array Integrated Grid System With Maximum Power Extraction Capability

This article presents a grid-integrated hybrid renewable energy sources based system comprising a solar photovoltaic (PV) array and a wind energy conversion system (WECS). The WECS uses a position-sensorless synchronous reluctance generator (SynRG) for the electric power generation from the wind turbine (WT), wherein, a sensorless field-oriented control (FOC) is made use of for the maximum power extraction (MPE). A second-order flux estimation (SFE) method along with frequency-locked loop (FLL) is utilized for the accurate flux estimation from the SynRG stator voltages and currents. A set of back-to-back connected three-phase two leg voltage source converter (VSC) topology is selected for the grid integration of WECS. This system has a common dc link where the solar PV array and the machine-side VSC (MSC) of the wind generator, are directly connected. The power output from the solar PV array and WECS, is shared between the grid and the local loads. The maximum power generation from SynRG in the WECS, is achieved by operating the SynRG at the speed estimated by the MPE algorithm. The maximum power is drawn from the solar PV array by adjusting the dc-link voltage, which is decided by the algorithm. For the proper power control and power quality improvement, the grid-side converter (GSC) is adequately controlled by implementing an observer-based control technique. The real-time validation of the system, is carried out using a developed laboratory prototype.

Optimized operation of diversion-type hydropower reservoir to alleviate ecological degradation of the de-watered river reach

Diversion-type hydropower stations usually cause seriously de-watered situation of the natural river reach, which has adverse effects on the downstream river ecosystem. To alleviate the negative impacts on ecosystem of natural river reach, this study quantified the ecological requirements and incorporated them into the reservoir operating schemes to provide the ecological flow, which is beneficial to the balance between ecosystem protection and hydropower generation. The method mainly includes (1) propose an optimal ecological flow calculation method based on runoff probability distribution, (2) combine minimum ecological flow with optimal ecological flow to define the ecological protection degree, and then (3) establish the multi-objective optimization model of reservoir with the goal of maximizing ecological protection degree and power generation (DPM) and solve it with NSGA-II. In the meanwhile, the optimization model with the goal of minimizing ecological water shortage and maximizing power generation (SPM) was established and solved which was regarded as a control batch. A case study performed with the Liujiaping (LJP) reservoir in Hunan Province of South China demonstrates that optimized operation can play a protective role in the ecology of the dewatered section. And DPM has better ecological benefits than SPM under the same power generation benefits, especially when the emphasis is placed on ecological benefits.

A Dynamic Analysis of the Multi-Stack SOFC-CHP System for Power Modulation

This paper performs a dynamic analysis of a 10-kW solid oxide fuel cell/combined heat and power (SOFC-CHP) system with a multi-stack module via numerical simulations. The performance of stacks, tail gas burners, heat exchangers, and fuel reformers are modeled by the MATLAB/Simulink module. The effects of fuel and air maldistribution on SOFC-CHP systems are addressed in this work. A two-stack module for 10-kW power generation is adopted to represent the multi-stack module with high power modulation. The air flow rate and operating current, which are related to the fuel use rate of an SOFC system, should be optimally regulated to perform with maximum power generation and efficiency. The proposed dynamic analysis shows that the operating temperatures of the two stacks have a difference of 33 K, which results in a reduced total power generation of 9.77 kW, with inconsistent fuel use (FU) rates of 78.3% and 56.8% for the two stacks. With the optimal control strategy, the output power is increased to 10.6 kW, an increment of 8.5%, and the FU rates of the two stacks are improved to 79% and 70%, respectively. As a potential distributed power generator, the long-term effects of the studied SOFC-CHP systems are also investigated. The dynamic analysis of the long-term operating SOFC-CHP system shows that the total daily output power can be increased 7.34% by using the optimal control strategy.

New opportunities for electricity generation in shallow hot dry rock fields: A study of thermoelectric generators with different heat exchangers

Despite being one of the largest renewable sources, geothermal energy is not widely utilized for electricity generation. In order to leverage shallow hot dry rock (HDR) fields, the present paper proposes an alternative to enhanced geothermal systems (EGS): thermoelectric generators. Based on the conditions of Timanfaya National Park, a prototype has been built to experimentally analyze the feasibility of the proposed solution. The prototype is composed by a two phase closed thermosyphon (TPCT) as hot side heat exchanger, two thermoelectric modules, and it considers different cold side heat exchangers: fin dissipators assisted by a fan and loop thermosyphons, both with various geometries. Experiments have demonstrated that loop thermosyphons represent the best alternative due to their low thermal resistance and, especially, due to their lack of auxiliary consumption, leading to a maximum net power generation of 3.29 W per module with a temperature difference of 180 °C (200 °C in the hot side and 20 °C as ambient temperature), 54% more than with fin dissipators. Hence, there exists a new opportunity for electricity generation in shallow hot dry rock fields: thermoelectric generators with biphasic thermosyphons as heat exchangers, a patented and robust solution.

Multi-Objective Optimal Scheduling Model of Dynamic Control of Flood Limit Water Level for Cascade Reservoirs

Reservoirs play a significant role in water resources management and water resource allocation. Traditional flood limited water level (FLWL) of reservoirs is set as a fixed value which over-considers the reservoir flood control and limits the benefits of reservoirs to a certain extent. However, the dynamic control of the reservoir FLWL is an effective solution. It is a method to temporarily increase the water level of the reservoir during the flood season by using forecast information and discharge capacity, and it can both consider flood control and power generation during the flood season. Therefore, this paper focuses on multi-objective optimal scheduling of dynamic control of FLWL for cascade reservoirs based on multi-objective evolutionary algorithm to get the trade-off between flood control and power generation. A multi-objective optimal scheduling model of dynamic control of FLWL for cascade reservoirs which contains a new dynamic control method is developed, and the proposed model consists of an initialization module, a dynamic control programming module and an optimal scheduling module. In order to verify the effectiveness of the model, a cascade reservoir consisting of seven reservoirs in the Hanjiang Basin of China were selected as a case study. Twenty-four-hour runoff data series for three typical hydrological years were used in this model. At the same time, two extreme schemes were chosen for comparison from optimized scheduling schemes. The comparison result showed that the power generation can be increased by 9.17 × 108 kW·h (6.39%) at most, compared to the original design scheduling scheme, while the extreme risk rate also increased from 0.1% to 0.268%. In summary, experimental results show that the multi-objective optimal scheduling model established in this study can provide decision makers with a set of alternative feasible optimized scheduling schemes by considering the two objectives of maximizing power generation and minimizing extreme risk rate.

Performance of genetic algorithms with different selection operators for solving short-term optimized reservoir scheduling problem

The tournament operator genetic algorithm (TGA) often shows poor convergence and easily gets trapped in a local optimum when solving optimized reservoir scheduling problems. The selection operation is the most important operation determining an algorithm’s convergence; therefore, this study proposes a proportional reproduction selection-based operator genetic algorithm (RGA) and a steady-state reproduction selection-based operator genetic algorithm (SGA) as alternatives to TGA. This study used TGA, RGA, and SGA to solve the maximum power generation model for the Gezhouba hydropower station, the largest runoff hydropower station in the world. Then, by using the maximum hydropower station output under a given typical runoff scenario as the optimization criterion, this study evaluated the optimized solution performance of the GA using different selection operators. The results show that TGA, SGA, and RGA can be applied to solve the short-term reservoir scheduling model. As the number of iterations increases, the hydropower station output optimized by these three GAs increases. Based on the maximum power generated by the Gezhouba hydropower station, SGA and RGA provide better results than TGA, and between SGA and RGA, the former provides better results.

WASTE HEAT CONVERSION IN COMPRESSION IGNITION ENGINE TO THE ELECTRIC POWER BY USING EXHAUST HEAT RECOVERY SYSTEM CONTAINED TEG

The energy lost in all internal combustion engines throughout the operation process is high; the most significant part of the energy produced during the combustion process is wasted meantime the engine cooling and exhaust systems. The exploitation of this energy is gained in terms of raising the efficiency of engines. This power can be used to enhance the air pumping to the engine to boost the effectiveness of combustion through the use of a turbocharger or used to raise the temperature of the incoming air into the combustion chamber within certain limits to increase the temperature at which the heat is added. The thermal energy enables to turn into electrical energy by employ thermoelectric generators (TEG). In this research, the thermoelectric generator was used which installed on the outer wall of the exhaust terminal. The four thermoelectric generators were installed and connected in series and parallel. The temperature changes through the two sides of the thermoelectric generator; current, voltage and power were measured by using instrumentation tools. The practical part of the research was accomplished operation condition of an engine speed of (2200 rpm), the fuel consumption of (0.67kg/hr) brake power of 1.87kw and an ambient air temperature of 11°C. The experimental outcomes show that the maximum voltage generated from the four thermoelectric generators when connected in series is (17.01volt), and the maximum power generation. Also, the maximum current generation was 15.49 imper when connecting the thermoelectric generator in parallel

Performance analysis of a solar‐powered water pumping using improved SIDO buck–boost converter

This study proposes a low-cost solar-powered water pumping system (SPWPS) utilising a proposed single-input dual-output (SIDO) buck–boost converter with an efficient control technique for the switched reluctance motor (SRM) drive. The newly designed buck–boost converter provides a continuous input and output current to the motor with a low ripple content. This converter is also capable to minimise the size of DC-link capacitor and to provide a balanced dual output voltage supply. Owing to the fundamental frequency switching of a split DC mid-point converter, there is a considerable reduction in the semiconductor losses and provides an opportunity to eliminate the sensors from the motor side. In addition, an improved perturb and observe (P&O) maximum power point tracking (MPPT) technique is also implemented in proposed system. The implemented MPPT algorithm has drift-free operation and an ability to control the pumping rate also at maximum PV power generation, which is usually difficult in standalone water pumping system. Test results are presented on an 875-Wp PV array fed a 1 hp pump to demonstrate sound agreement between the simulated and test results of proposed system.

Response of thermoelectric generators to Bi2Te3 and Zn4Sb3 energy harvester materials under variant solar radiation

Some special features like having no moving parts and long lifetime and being highly reliable make thermoelectric generators (TEGs) a proper choice to convert solar energy into electricity. In this work, performance of Bi2Te3 and Zn4Sb3 solar thermoelectric generators (STEGs) are studied under transient condition using both experimental and numerical approaches. Variation of the temperatures of the hot and cold sides of the TEGs, open circuit voltage, short circuit current and maximum power generation to the fluctuation of the solar radiation, simulting semi-cloudy weather, are obtained and discussed. Effect of thermoelectric material properties and geometry of the thermoelectric elements on electrical response and performance of the STEGs is invetigated. Results of the developed numerical model using finite volume method are in good agreement with the experimental data. Performance of the TEG without graphite layer and with the same solar radiation condition is investigated and compared with the TEG with graphite layer. The results show that, applying the graphite layer significantly enhances performance of the STEGs. It is found that using graphite layer enhances the efficiency of the STEG system. Furthermore, for high solar concentrations, Zn4Sb3 based STEG module has better performance compare to the Bi2Te3 based module.

Energy-harvesting enhancement in composites of microwave-exfoliated KNN and multiwall carbon nanotubes

The objective of this research work is to investigate the effect of multiwall carbon nanotube (MWCNT) content (0.3–1.2 wt%) on a potassium sodium niobate (KNN)-based piezoelectric unimorph harvester for enhancing the energy generation capacity. KNN–MWCNT composites were fabricated by using a microwave solid state technique. The energy-harvesting performance of the KNN–MWCNT composite was determined by the base excitation method and sized to resonate between 20 and 100 Hz at 1 $$\hbox {M}\Omega $$ load resistance. The energy performance of the KNN composite at percolation threshold (0.6 wt% MWCNT) showed a maximum power generation of $$2.94\, \upmu \hbox {W}$$ , the power density of 7.15 $$\upmu \hbox {W}$$ $$\hbox {m}^{-3}$$ and overall efficiency of 83.75% at an input acceleration of 0.5 g and a load resistance of 1 $$\hbox {M}\Omega $$ . Improvements observed in the power generation by percolation phenomena and ionic flow over the nanotube surface of KNN composites prove to be a boon for low-power sensing devices.

Design optimization and experimental evaluation of photovoltaic double skin facade

This study proposed the introduction of a photovoltaic double skin façade (PV-DSF) as a way to economically and easily improve the performance of building envelopes. This system has been designed to be installed not only in new buildings but also in remodeling or renovation projects of existing buildings even in a state where occupants are present inside. For the PV-DSF system suggested, this study aimed to perform experimental evaluation of 1) the optimal operation method to maximize electric energy production of the PV vent window and to reduce the heating and cooling energy consumption of buildings and 2) the thermal behavior and energy performance of the building when the proposed PV-DSF is applied.Analysis results using simulation have shown that the monthly optimal operating angles of the PV vent window to minimize heating and cooling energy demand were the same as the operating angles to maximize power generation. It has also been proven through experiments that the proper operation of the PV vent window can significantly reduce the energy demand of buildings. In particular, the difference between the DSF and outdoor temperatures was 12 °C in winter, showing that it is possible to achieve a significant reduction of heating energy demand. Lastly, when the PV-DSF was applied, air and wall temperatures were decreased by 0.5 °C and 2 °C in summer, respectively, and cooling energy consumption was also at least 10% reduced on average.