Maximum Electrical Power Output Research Articles

Shooting Three Birds with One Stone: Device Construction and Thermal Management for Simultaneous Photothermal Conversion Water Evaporation, Thermoelectric Generation and Photocatalytic Degradation

AbstractIt's a promising way to address the global freshwater crisis and energy shortage through solar‐driven devices with evaporate, degrade, and generate electricity at the same time. Low‐efficient light‐thermal conversions for multi‐usage limit application. This paper presents a low‐cost melamine foam/TiO2/carbon black/bismuth (MF/TiO2/CB/Bi) composite with excellent activity to simultaneously process photothermal water evaporation, pollutant degradation, and thermoelectric output, namely‚ shooting three birds with one stone. Under 1 sunlight light intensity, the water evaporation rate reach 4.235 kg m−2 h−1, and the maximum electric power output of a single module is 0.733 W m−2. Meanwhile, Rhodamine B (RhB) solution with 4.0 × 10−4 mol L−1 can be almost degraded within 60 min. Excellent performance benefits from the enhanced adsorption by chemicals, 3D structure for accepting more incident light, and hydrophilic group reducing evaporation enthalpy. Combined with the simulation and experiment, the relationship between heat distribution and thicknesses is studied. When less than 1.98 cm, the lateral temperature is higher than the ambient temperature, thus additional energy cannot be obtained. This work provides a facile and novel method for the construction of photothermal conversion materials with multi‐functional, as a new and useful attempt to solve the shortage of fresh water and electric energy, as well as environmental pollution.

Experimental investigation on the performance of a micro-ORC system for different operating conditions

The micro-ORC systems are widely considered a reliable solution for domestic power production from renewable sources. The investigation of the optimal operating conditions to maximize system efficiency is an interesting challenge. In this study, a preliminary experimental campaign has been carried out on a biomass-fired micro-ORC system. The system is designed for stationary applications for domestic users, with a gear pump, a scroll expander and R245fa as the working fluid. The performance characterization of the micro-ORC under steady-state conditions has been obtained varying the water flow rate in the condenser at constant pump and expander speeds. The temperature of the hot source (thermal oil) is the maximum achievable in each operating condition. The temperature at the expander inlet and the condenser and evaporator pressure strongly influence the system performance. The increase in water flow leads to a decrease in the condenser pressure and a reduction of the superheating degree of the organic fluid. The system reaches the maximum electric power output of approximately 2565 W with a water flow rate of about 20 l/min. The highest electrical efficiency increases as the refrigerant flow rate decreases and reaches the highest value of 8.1% for the minimum investigated water flow rate.

Investigations on thermoelectric characteristic of heat pipe thermoelectric generator waste heat utilization device in nuclear power system

This paper proposes a waste heat utilization method for new type reactor by Heat Pipe - Thermoelectric Generator (HP-TEG) to utilize the waste heat of lower divertor in fusion device and stirling generator in heat pipe space reactor. The feasibility of the HPTEG waste heat utilization device is verified by its principle prototype. Firstly, the numerical simulations of the single heat pipe and principle prototype were carried out to provide a numerical optimization scheme for the design of the principle prototype. The simulation results show that the heat transfer efficiency of the copper–water heat pipe is about 93%, while the overall heat transfer efficiency of the principle prototype is about 85%. Based on the simulation results, the thermal stress concentration areas were found, mainly concentrated in the thermal insulation short of the heat pipe. During the construction of the principle prototype, stainless steel sleeves were installed outside the insulation section of the heat pipe to limit the thermal expansion caused by the thermal stress concentration. Besides the principle prototype of HPTEG assembled in new type reactor was built, and its thermoelectric characteristics were studied, the results verified the feasibility of using waste heat. The test results show that the principle prototype starts smoothly, and the heat pipe has suitable isothermal properties (△T < 15 ℃). Due to the heat pipe's high heat transfer efficiency, the heat pipe obtained from the experiment is 91%–96%. The principle prototype has good heat transfer efficiency, which is 81.94%–93.25%. The maximum total electric power output of TEG is 16.37 W, in which the corresponding current is 0.52A, and the power generation efficiency is up to 1.49%. This paper verifies the feasibility of HPTEG to utilize the waste heat of lower divertor in fusion device and stirling generator in heat pipe space reactor, which provides a reference for the utilization of reactor residual heat.

Modeling of a Wind Power System Using the Genetic Algorithm Based on a Doubly Fed Induction Generator for the Supply of Power to the Electrical Grid

This paper is interested in studying a system consisting of a wind turbine operating at variable wind speeds, and a two-feed asynchronous machine (DFIG) connected to the grid by a stator and fed by a transducer at the side of the rotor. The conductors are separately controlled for active and reactive power flow between the stator (DFIG) and the grid. The proposed controllers generate reference voltages for the rotor to ensure that the active and reactive power reaches the required reference values, to ensure effective tracking of the optimum operating point and to obtain the maximum electrical power output. Dynamic analysis of the system is performed under variable wind speeds. This analysis is based on active and reactive energy control. The new work in this paper is to introduce theories of genetic algorithms into the control strategy used in the switching chain of wind turbines in order to improve performance and efficiency. Simulation results applied to genetic algorithms give greater efficiency, impressive results, and stability to wind turbine systems are compared to classic PI regulators. Then, artificial intelligent controls, such as genetic algorithms control, are applied. Results obtained in the Matlab/Simulink environment show the efficiency of this proposed unit.

A Study on an Unpressurized Medium-Temperature-Differential Stirling Engine Integrated with a New Spiral-Patterned Flat-Flame Burner and a New Spiral-Finned Hot-End Plate

The present study experimentally investigates the performance of a power generator constituted by an unpressurized Stirling engine coupled with a new flat-flame burner. The operative temperature differential of the Stirling engine is within the medium range (around 400 K or less). In this work, there are two types of the engine’s hot-end-plate designs, a conventional flat plate and the new type with spiral fins developed within this framework. Consequently, the new hot-end-plate design forms spiral-patterned channels to enhance the engine’s heat input rate, thus partly compensating for the inherently low thermal efficiency of an unpressurized engine. The spiral fins are used to increase the resident time of the flue gas and increase the heat-transfer area. In addition, engine performance is measured for two types of fuels, namely, DME (renewable) and propane (fossil). Using propane, the new hot-end plate allows for a maximum electric power output of 24.6 W, which is typically superior to common unpressurized Stirling engines. Compared to the conventional hot-end plate, the new hot-end plate improved electric power output and the thermal-to-electric efficiency up to 63% and 47%, respectively. The study also proved the effectiveness of applying the integration of the new hot-end plate and the new flat-flame burner on boosting the power output of the present Stirling engine generator.

Green-in-green biohybrids as transient biotriboelectric nanogenerators

Green self-powered devices based on biodegradable materials have attracted widespread attention. Here, we propose the construction of the transient biotriboelectric nanogenerator (TENG) using green-in-green bionanocompoites. The green-in-green nanocomposites, cellulose nanocrystal (CNC)/polyhydroxybutyrate (PHB), are prepared with a high-pressure molding method. The CNC promotes the degradation and enhances the dielectric constant of CNC/PHB. It further allows for the significant improvement of the triboelectric output of CNC/PHB-based TENG. The voltage output and current output of CNC/PHB-based TENG are 5.7 and 12.5 times higher than those of pristine PHB-based TENG, respectively. Also, the bio-TENG exhibits admirable signal stability in over 20000 cycles. Despite the high hardness of CNC/PHB, a soft but simple-structured arch sensor is successfully assembled using CNC/PHB-based TENG. It can attain the precise real-time monitoring of various human motions. This study may provide new insights into the design/fabrication of green functional materials, and initiate the next wave of innovations in eco-friendly self-powered devices.

Semitransparent polymer solar cell/triboelectric nanogenerator hybrid systems: Synergistic solar and raindrop energy conversion for window-integrated applications

Development of photovoltaic (PV)-derived hybrid power systems can overcome the weather-dependent electricity production and increase the amount of dispatchable renewable energy generation. Herein, monolithic hybrid devices are developed via rational integration of high-performance semitransparent polymer solar cells (ST-PSCs) and liquid−solid triboelectric nanogenerators (TENGs). High-performance PSCs with efficiencies of 17.4% for rigid and 15.7% for flexible devices are achieved. Further electrode modifications and integration of transparent TENGs synergistically balance the above-bandgap photon harvesting and transparency in a broad wavelength range (380 − 1000 nm), yet significantly reduce the transmittance in the near-infrared wavelength range (1000 − 2500 nm) of hybrid devices. The hybrid devices simultaneously provide high visible light transparency, good color fidelity, efficient heat resistance and possibility to integrate on rigid and flexible substrates. The hybrid devices attain a high solar conversion efficiency of 10.1% under 1 sun, indicating efficient light-to-electricity conversion (a maximum electrical power output: 101 W m−2) on sunny days. The hybrid devices can also generate a maximum electrical power output of 2.62 W m−2 through waterdrop energy conversion, implying complementary green electricity production on rainy days. The controlled ambient temperature and specific transmittance windows provided by the hybrid devices sustain plant growth and highlight their great potential in agricultural applications. Gratifyingly, this work demonstrates the first example of ST-PSC/TENG hybrid systems for scaling up renewable power generation in different weather conditions, considering architectural and agricultural applications.

Multicriteria Approach for Design Optimization of Lightweight Piezoelectric Energy Harvesters Subjected to Stress Constraints

In this work a multicriteria optimization approach to minimize weight and maximize power output in piezoelectric energy harvesting systems for aerospace applications is studied. The design variables are the geometric and electric circuit parameters of the vibration-based piezoelectric energy harvester (PEH). A finite element model is developed to model the dynamic behavior of the composite plate-type harvester with embedded piezoelectric layers. The cantilever PEH structure is subjected to constraints in the bending stresses which must be lower than or equal to the tensile yield strength of the piezoelectric material. For solving the multi-objective optimization problem, the Non-dominated Sorting Genetic Algorithm II (NSGA-II), the Non-dominated Sorting Genetic Algorithm III (NSGA-III) and the Generalized Differential Evolution 3 (GDE3) algorithm are employed. It is shown that the proposed algorithms are effective in developing optimal Pareto front curves for maximum electrical power output and minimum mass of the PEH system. A comparative assessment of the solutions generated on the Pareto Front show that GDE3 achieved solutions that generate higher maximum power output and performs better compared to the two other algorithms.

Optimization Using a Genetic Algorithm Based on DFIG Power Supply for the Electrical Grid

In this paper, we will be interested in studying a system consisting of a wind turbine operating at variable wind speed, and a two-feed asynchronous machine (DFIG) connected to the grid by the stator and fed by a transducer at the side of the rotor. The conductors are separately controlled for active and reactive power flow between the stator (DFIG) and the grid. The proposed controllers generate reference voltages for the rotor to ensure that the active and reactive power reaches the required reference values, to ensure effective tracking of the optimum operating point and obtaining the maximum electrical power output. Dynamic analysis of the system is performed under the variable wind speed. This analysis is based on active and reactive energy control. The new work in this paper is to introduce theories of genetic algorithms into the control strategy used in the switching chain of wind turbines, to improve performance and efficiency. Simulation results applied to genetic algorithms give greater efficiency, impressive results, and stability to wind turbine systems compared to classic PI regulators. Then, artificial intelligent controls, such as genetic algorithms control, are applied. . Results obtained, in Matlab/Simulink environment, show the efficiency of this proposed unit.

An analytical model to evaluate the fatigue crack effects on the hybrid photovoltaic-thermoelectric device

A hybrid photovoltaic and thermoelectric device can effectively increase utilization of solar systems. In this article, an analytical model to evaluate the fatigue cracking and its effect on electric power of a hybrid photovoltaic-thermoelectric device is proposed. Both the analytical and simplified expressions of crack length and electric power versus the cyclic number are presented. It is found that combining thermoelectric module with photovoltaic cell of a small temperature coefficient 0.001 K-1 can improve the total electric power by 7.8%. Inclusion of thermoelectric module with photovoltaic cell of a large temperature coefficient 0.004 K-1 reduces the total electric power by 3.3%. The electric power of the hybrid device is inversely proportional to the cyclic number. For photovoltaic cells with small temperature coefficient, the total electric power decreases with crack propagation. The total electric power increases with crack propagation for photovoltaic cells of large temperature coefficient. The thickness ratio of photovoltaic cell to the insulating layer is optimized to eliminate the interlaminar shear stress thus greatly enhance lifetime. Lifetime of the hybrid devices can be availably improved by appropriately increasing thickness of the insulating layer. The optimized length of thermoelectric module for obtaining the maximum electric power output is given.

Performance of diesel engine having waste heat recovery system fixed on stainless steel made exhaust gas pipe

Chemical energy is not effectively converted into mechanical energy by an internal combustion engine. Major portion of heat energy get dissipated with exhaust and coolant. Use of thermoelectric generator (TEG) technology is regarded as an environment friendly technique for recovering the waste heat, with which heat energy directly converts into electrical energy. In this study, an experiment is conducted in which TEG technology has been used to recover waste heat going out through exhaust gas from the diesel engine. Thermoelectric modules were fixed on the surface of stainless steel made pipe having square cross-section. It has been found that the power output of thermoelectric generator enhances with the increase in engine load. The maximum electrical power output of TEG has been obtained as 37 W at maximum load of 6 kg. Overall thermal efficiency of diesel engine has also been improved with the use of TEG type of waste heat recovery system.

Study and Order of a Medium Power Wind Turbine Conversion Chain Connected to Medium Voltage Grid

In this article, we will study a system consisting of a wind turbine operating at a variable wind speed and a two-feed asynchronous machine (DFIG) connected to the grid by the stator and fed by a transducer at the rotor side. The conductors are separately controlled for active and reactive power flow between the stator (DFIG) and the network, which is achieved using conventional PI and fuzzy logic. The proposed controllers generate reference voltages for the rotor to ensure that the active and reactive powers reach the required reference values, in order to ensure effective tracking of the optimum operating point and to obtain the maximum electrical power output. System modeling and simulation were examined with Matlab. Dynamic analysis of the system is performed under variable wind speed. This analysis is based on active and reactive energy control. The results obtained show the advantages of the proposed intelligent control unit.

Experimental investigation of an Organic Rankine cycle system using an oil-free scroll expander for low grade heat recovery

ABSTRACT Organic Rankine cycle (ORC) has become a promising energy harvesting technique to recover thermal energy from low-grade heat sources. In this study, a lab-scale ORC system has been designed, constructed, and tested to investigate the potential of utilizing the heat from hot water, which is used to simulate the jacket water of internal combustion engines. The ORC system employs an oil-free scroll expander with R245fa as working fluid. A wide range of operating conditions has been studied by adjusting the pump frequency, the load and the mass flow rate of cooling water. Effect of the superheat degree at the expander inlet was investigated and the results showed that the ORC system presented better performance with superheat of 0. It is concluded that the system should be controlled to maintain the least possible superheat degree to obtain higher power output and better efficiency. The maximum electric power output and the maximum thermal efficiency are 0.61 kW and 4.09%, respectively, when the heat source is 96.8°C. The power consumed by the pump ranges from 0.07 to 0.18 kW, which accounts for 22 to 39% of the power output of ORC.

Nanostructured Black Aluminum Prepared by Laser Direct Writing as a High-Performance Plasmonic Absorber for Photothermal/Electric Conversion.

Utilizing the abundant and renewable solar energy to address the global energy shortage and water scarcity is promising. Great effort has been devoted to photothermal conversion for its typically full-spectrum utilization and high efficiency. Here, the coral-like micro/nanostructure was fabricated on an aluminum sheet by a facile laser direct writing technology. The nanocluster and microscale branches of corals endowed this black aluminum with broad-band plasmonic absorption and rapid heat transfer from the light absorption region to substrate. The black aluminum achieved ultrahigh solar absorbance of over 92.6% (>95.1% in the visible range) and excellent light heating ability (>90.6 °C under 1.0 sun). With good photothermal properties, this plasmonic absorber was used in a state-of-the-art eight-layer membrane distillation system, producing a water yield of up to 2.40 kg m-2 h-1 and a high solar conversion efficiency of 166.5% under 1-sun irradiation. Photothermal electricity was also achieved based on this system with a thermoelectric generator, with a water yield of 0.89 kg m-2 h-1 and a maximum electrical power output of 7.21 μW cm-2 under 1.0 sun. Considering the excellent performance of the plasmon-enhanced black aluminum, this work provides an alternative and feasible route toward high-efficient utilization of the solar energy.

An efficient pulsed- spray water cooling system for photovoltaic panels: Experimental study and cost analysis

Cooling of photovoltaic panels is an important factor in enhancing electrical efficiency, reducing solar cell destruction, and maximizing the lifetime of these useful solar systems. Generally, the traditional cooling techniques consume considerable amount of water, which can be a major problem for large scale photovoltaic power stations. In this experimental study, a pulsed-spray water cooling system is designed for photovoltaic panels to improve the efficiency of these solar systems and decrease the water consumption during the cooling process. The results of the photovoltaic panel with the pulsed-spray water cooling system are compared with the steady-spray water cooling system and the uncooled photovoltaic panel. A cost analysis is also conducted to determine the financial benefits of employing the new cooling systems for the photovoltaic panels. The results show that as compared with the case of non-cooled panel, the maximum electrical power output of the photovoltaic panel increases about 33.3%, 27.7%, and 25.9% by using the steady-spray water cooling, the pulsed-spray water cooling with DC = 1 and 0.2, respectively. The pulsed-spray water cooling system with DC = 0.2 can reduce the water consumption to one-ninth in comparison with the case of steady-flow one. The levelized cost of electricity by the uncooled system was found lower than the spray-cooled systems but very near to pulsed-spray water cooling with DC = 0.2. The levelized cost of electricity produced by the PV system is reduced about 46.5% and 76.3% by using the pulsed-spray water cooling system with DC = 1 and 0.2, respectively as compared with the case of steady-spray water cooling system. As a result, the new pulsed-spray water cooling is efficient from the economic point of view.

Non-linear piezoelectric fluidic energy harvesters: The mutual interaction of two oscillating cylinders

The presence of a bluff body upstream of a cantilever beam promotes persistent, aero-elastic vibrations of the beam. Vortex-induced vibration in an array of two mutually interacting bluff bodies in such configurations undergoing two-degrees of freedom transverse oscillation has not been investigated before. In the present work, we have studied experimentally, the unsteady response of an array of two similar rigid cylinders, positioned side-by-side in reference to the freestream velocity, each one mounted on the upstream end of an elastic cantilever beam. By fitting the beams with piezoelectric layers, these configurations are converted to piezoelectric fluid energy harvesters (PFEH) that can extract small amounts of energy from the flow. Comparing the performance of linear (L-PFEH), non-linear (NL-PFEH), and a non-linear array (NLA-PFEH) of harvesters show that NLA-PFEH has the widest broadband operating velocity range and the greatest generated power followed by NL-PFEH and then L-PFEH. The maximum electric power output of NLA-PFEH was ~1000% greater than for NL-PFEH with a corresponding ~250% increase in the operating velocity range. Different cylinder configurations reveal the presence of hysteresis in the behavior of NLA-PFEH when the distance between the cylinders (so-called cylinder gap to diameter ratio), G/ D &lt; 0.5. At large distances from each other ( G/ D ≥ 4), the two cylinders behave like independent, isolated harvester units with rather weak mutual interaction.

Effects of the Angled Blades of Extremely Small Wind Turbines on Energy Harvesting Performance

Low-intensity winds can be useful power sources in the context of energy harvesting. This study aims to enhance the power generation capacity of a super micro wind turbine (SMWT) in low-intensity winds by modifying the blade geometry, which cannot be realized in conventional wind turbines owing to the stress concentration. By controlling the curved angle (θ) in the middle of the blade, the rotor performance can be improved, and the rotor diameter can be reduced to increase installation density. Experimental results indicated that the optimal θ value was 105°, at which the AC voltage was improved by 7.4% compared to that in the case of the basic model with θ = 0°. The maximum electric power output was 9.333 μW and the load resistance was 47.62 kΩ. Moreover, a computational fluid dynamics analysis was performed to clarify the pressure field and streamlines on and around the blade to demonstrate the aerodynamic performance of the SMWT. The proposed blade geometry is one of many possible designs that can enhance extremely small wind turbines for energy harvesting.

Experimental study of small scale and high expansion ratio ORC for recovering high temperature waste heat

In recent times, the use and development of small-scale (≈ 10 kW) ORC systems has received an increasing interest. However, the operational characteristics of small-scale high-expansion ratio ORC turbines are not yet well understood. In this study, a small-scale high-temperature ORC was investigated experimentally. The studied system has a high-speed turbogenerator including a supersonic radial turbine, a permanent magnet generator and a Barske-type feed pump assembled on a single shaft. Siloxane MDM is used as the working fluid. The turbogenerator performance was studied under different operating conditions and the experimental results were compared against the results obtained from the numerical ORC cycle model for validating the numerical results. The turbine was analyzed to have the mechanical power output close to the system design value and a maximum electric power output of 6 kW was measured. The turbogenerator was capable to be operated at the targeted rotational speed range of 12 000 rpm to 31 000 rpm. Thus, the technical potential of using high rotational speed and supersonic turbomachinery in small-scale and high expansion ratio ORC applications was confirmed. The results highlights the importance of reducing turbogenerator losses and internal power consumption to reach higher power outputs in the future.

Performance of a Thermoelectric Module Based on n-Type (La0.12Sr0.88)0.95TiO3\u2212\u03b4 and p-Type Ca3Co4\u2212xO9+\u03b4

Here, we present the performance of a thermoelectric (TE) module consisting of n-type (La0.12Sr0.88)0.95TiO3 and p-type Ca3Co4−xO9+δ materials. The main challenge in this investigation was operating the TE module in different atmospheric conditions, since n-type has optimum TE performance at reducing conditions, while p-type has optimum at oxidizing conditions. The TE module was exposed to two different atmospheres and demonstrated higher stability in N2 atmosphere than in air. The maximum electrical power output decreased after 40 h when the hot side was exposed to N2 at 600°C, while only 1 h at 400°C in ambient air was enough to oxidize (La0.12Sr0.88)0.95TiO3 followed by a reduced electrical power output. The module generated maximum electrical power of 0.9 mW (∼ 4.7 mW/cm2) at 600°C hot side and δT ∼ 570 K in N2, and 0.15 mW (∼ 0.8 mW/cm2) at 400°C hot side and δT ∼ 370 K in air. A stability limit of Ca3Co3.93O9+δ at ∼ 700°C in N2 was determined by in situ high-temperature x-ray diffraction.

Modeling, Simulation and Optimization of Power Plant Energy Sustainability for IoT Enabled Smart Cities Empowered With Deep Extreme Learning Machine

A smart city is a sustainable and effective metropolitan hub, that offers its residents high excellence of life through appropriate resource management. Energy management is among the most challenging problems in such metropolitan areas due to the difficulty and key role of energy systems. To optimize the benefit from the available megawatt-hours, it is important to predict the maximum electrical power output of a baseload power plant. This paper explores the method of a deep extreme learning machine to create a predictive model that can predict a combined cycle power plant’s hourly full-load electrical output. An intelligent energy management solution can be achieved by properly monitoring and controlling these resources through the internet of things (IoT). The universe of artificial intelligence has produced many strides through deep learning algorithms and these methods were used for data analysis. Nonetheless, for further accuracy, deep extreme learning machine (DELM) is another candidate to be investigated for analyses of the data sequence. By using the DELM approach, a high level of reliability with a minimum error rate is achieved. The approach shows better results compared to previous investigations since previous studies could not meet the findings up to the mark and unable to predict power plant electrical energy output efficiently. During the investigation, it is shown that the proposed approach has the highest accuracy rate of 98.6% with 70% of training (33488 samples), 30% of test and validation (14352 examples). Simulation results validate the prediction effectiveness of the proposed scheme.