Modeling, Simulation, and Implementation of a Solar Thermoelectric Energy Harvesting System

New alternatives and inventive renewable energy techniques which encompass both generation and power management solutions are fundamental for meeting remote residential energy supply and demand today, especially if the grid is quasi-inexistent. Solar thermoelectric generators mounted on a dual-axis sun tracker can be a cost-effective alternative to photovoltaics for remote residential household power generation. A complete solar thermoelectric energy harvesting system is presented in this paper for energy delivery to remote residential areas in developing regions. To this end, the entire system was built, modeled, and then validated with the LTspice simulator software via the thermal-to-electrical analogy schemes. Valuable data in conjunction with a novel LTspice circuit were obtained, showing the achievability of analyzing transient heat transfer with the SPICE simulator; however a few of the problems to be solved remain at the practical level. Despite the unusual operation of the thermoelectric modules with the solar radiation, the simulation and measurements were in good agreement, thus validating the new modeling strategy.

Simultaneous Solar-driven Steam and Electricity Generation by Cost-effective,Easy Scale-up MnO 2-based Flexible Membranes

Harvesting solar energy in an effective manner for steam and electricity generation is a promising technique to simultaneously cope with the energy and water crises.However,the construction of efficient and easy scale-up photothermal materials for steam and electricity cogeneration remains challenging.Herein,we report a facile and cost-effective strategy to prepare MnO_(2)-decorated cotton cloth(MCx).The wide adsorption spectrum and excellent photothermal conversion ability of the in situ-formed MnO_(2)nanoparticles make the MCx to be advanced photothermal materials.Consequently,the hybrid device integrated with MCx as the photothermal layer and the thermoelectric(TE)module for electricity power conversion exhibits an extremely high evaporation rate of 2.24 kg m^(−2)h^(−1)under 1 kW m^(−2)irradiation,which is ranked among the most powerful solar evaporators.More importantly,during solar evaporation,the hybrid device produces an open-circuit voltage of 0.3 V and a power output of 1.6 W m^(−2)under 3 Sun irradiation,and outperforms most of the previously reported solar-driven electricity generation devices.Therefore,the integrated device with synergistic solar-thermal utilization opens up a green way toward simultaneous solar vapor and electric power generation in remote and resource-constrained areas.

Self-Floating Efficient Solar Steam Generators Constructed Using Super-Hydrophilic N,O Dual-Doped Carbon Foams from Waste Polyester

Solar evaporation is recognized as a prospective technique to produce freshwater from non-drinkable water using inexhaustible solar energy.However,it remains a challenge to fabricate low-cost solar evaporators with obviously reduced water evaporation enthalpy to achieve high evaporation rates.Herein,N,O dual-doped carbon foam(NCF)is fabricated from the lowtemperature carbonization of poly(ethylene terephthalate)(PET)waste by melamine/molten salts at 340℃.During carbonization,melamine reacts with carboxylic acids of PET degradation products to yield a crosslinking network,and then molten salts catalyze the decarboxylation and dehydration to construct a stable framework.Owing to rich N,O-containing groups,3D interconnected pores,super-hydrophilicity,and ultra-low thermal conductivity(0.0599 W m^(−1) K^(−1)),NCF not only achieves high light absorbance(ca.99%)and solar-to-thermal conversion,but also promotes the formation of water cluster to reduce water evaporation enthalpy by ca.37%.Consequently,NCF exhibits a high evaporation rate(2.4 kg m^(−2) h^(−1)),surpassing the-state-of-the-art solar evaporators,and presents good antiacid/basic abilities,long-term salt-resistance,and self-cleaning ability.Importantly,a large-scale NCF-based outdoor solar desalination device is developed to produce freshwater.The daily freshwater production amount per unit area(6.3 kg)meets the two adults’daily water consumption.The trash-to-treasure strategy will give impetus to the development of low-cost,advanced solar evaporators from waste plastics for addressing the global freshwater shortage.

Solar image deconvolution by generative adversarial network

With aperture synthesis(AS)technique,a number of small antennas can be assembled to form a large telescope whose spatial resolution is determined by the distance of two farthest antennas instead of the diameter of a single-dish antenna.In contrast from a direct imaging system,an AS telescope captures the Fourier coefficients of a spatial object,and then implement inverse Fourier transform to reconstruct the spatial image.Due to the limited number of antennas,the Fourier coefficients are extremely sparse in practice,resulting in a very blurry image.To remove/reduce blur,“CLEAN”deconvolution has been widely used in the literature.However,it was initially designed for a point source.For an extended source,like the Sun,its efficiency is unsatisfactory.In this study,a deep neural network,referring to Generative Adversarial Network(GAN),is proposed for solar image deconvolution.The experimental results demonstrate that the proposed model is markedly better than traditional CLEAN on solar images.The main purpose of this work is visual inspection instead of quantitative scientific computation.We believe that this will also help scientists to better understand solar phenomena with high quality images.

Continuous Mixed p-norm Control Scheme with Reweighted L_(0) norm Variable Step Size for Mitigating Power Quality Problems of Grid Coupled Solar PV Systems

In this paper,the performance of a two-stage three-phase grid coupled solar photovoltaic generating system(SPVGS)is analyzed by using a novel reweighted Lo norm variable step size continuous mixed p-norm(RLo-VSSCMPN)of a voltage source inverter(VSI)control scheme.The efficacy of the system is determined by considering unbalanced grid voltage,DC offset,voltage sag and swell,unbalanced load and variations in solar insolation.RLo-VSSCMPN is used for inverter control and it ex-tracts fundamental components of load current for generating the reference grid current with a faster convergence rate and lesser steady state oscillations.With the proposed control,harmonics in the grid current follows the IEEE-519 norm and the performance is also satisfactory under varying environmental/load conditions.The power generated from SPvGS is transferred optimally using a DC-DC boost converter utilizing the incremental conductance(INC)maximum power point technique.The proposed system is simulated using MATLAB/Simulink 2018a and test results are verified experimentally using dSPACE1202 in the laboratory to ensure the validity of a novel proposed robust RLo-VSSCMPN.Index Terms-INC maximum power point tracker,power quality,reweighted LoVSSCMPN algorithm,solar PV generating system,total harmonic distortion,voltage source inverter.

Wide spectrum solar energy harvesting through an integrated photovoltaic and thermoelectric system

This paper proposes a power system concept that integrates photovoltaic （PV） and thermoelectric （TE） technologies to harvest solar energy from a wide spectral range. By introduction of the ＇spectrum beam splitting＇ technique, short wavelength solar radiation is converted directly into electricity in the PV cells, while the long wavelength segment of the spectrum is used to produce moderate to high temperature thermal energy, which then generates electricity in the TE device. To overcome the intermittent nature of solar radiation, the system is also coupled to a thermal energy storage unit. A systematic analysis of the integrated system is carried out, encompassing the system configuration, material properties, thermal management, and energy storage aspects. We have also attempted to optimize the integrated system. The results indicate that the system configuration and optimization are the most important factors for high overall efficiency.

Book review:Solar chimney power generating technology

Since Prof. Jorg SCHLAICH from the University of Stuttgart in Germany built the first solar chimney power plant （SCPP） prototype in the early 1980s, research on SCPP technology has aroused worldwide attention from experiment, to theory and then feasibility studies for large-scale commercial application.

Plant-leaf-inspired MXene-silk composite for intelligent solar steam generation combined with mechanical actuation

Solar steam generators based on photothermal materials are important in producing fresh water.However,conventional solar steam generators are difficult to self-adapt to the complex external environment as organisms.Herein,inspired by the plant leaf,we propose a photothermal composite based on MXene and silk to add more functionality.On one hand,the composite achieves an evaporation rate of 1.51 kg·m^(−2)·h^(−1)and a conversion efficiency of 86.9%under a solar intensity of 1 kW·m^(−2),mimicking the water transpiration of plant leaf.On the other hand,the MXene-silk-based actuator shows a maximum bending curvature of 0.91 cm^(−1)under a solar intensity of 5 kW·m^(−2).Furthermore,an intelligent solar system is constructed utilizing the synergy of solar steam generator and actuator,which advances the research from the material level to the system level.Mimicking the behavior of plant leaf,the system can automatically open during the day to generate steam and fresh water.And at night or in bad weather,it will automatically close to prevent external pollution such as dust,achieving intelligent anti-fouling.This research will have good application prospects in less developed areas.Meanwhile,it also provides a certain reference value for exploring multi-functional photothermal devices in the future.

Solar thermoelectric generator and thermoelectric cooler performance:analysis and comparison using a different shape geometry

Thermoelectric devices are one of the technologies used either to generate electricity by applying a temperature difference using thermal energy or as a heating/cooling system by applying an electrical voltage.The number of materials required to produce a product is an important factor in determining its price.Production costs associated with these materials,as well as their availability and quality,play a crucial role in price determination by manufacturers.In this context,a method that employs a uniform volume distribution was implemented.This approach enabled the analysis to focus on other variables,thereby promoting a more precise and relevant evaluation of overall performance.Based on the finite element method,this study investigated the influence of geometric shape,including Rect-leg,Y-leg,Pin-leg and X-leg designs,on the performance of solar thermoelectric generators and thermoelectric coolers.The study was conducted considering the same hot alumina junction surface that receives solar radiation;however,the ef-fective surface,which corresponded to the heat flow area and had a similar area near the exposed surface,varied depending on the chosen leg geometry,thus impacting the heat flux due to the variation in thermal resistance.In the case of a solar thermoelectric generator,the Rect-leg model,having the same effective surface area,presented the lowest heat loss value resulting from convection and radiation in the heat spreader and the hot alumina plate.Under the same conditions,the Y-leg showed the highest value.The Rect-leg design generated,by using thermal and optical concentration,the highest output power of 0.028 and 0.054 W,and efficiency of 3.47%and 4.7%,respectively,whereas the Y-leg generated lower values of 0.006523 and 0.018744 W for power,and 2.83%and 2.71%for efficiency,respectively.In the case of the thermoelectric coolers,the Y-leg generated the highest temperature difference between the hot and cold sides of 67.28 K at an electric current value of 1.8 A,whereas the Rect-leg,Pin-leg and X-leg generated~66.25,~67.02 and~67.19 K at 6.1,2.7 and 2.6 A.

Perfect solar absorber based on nanocone structured surface for high-efficiency solar thermoelectric generators

Nanostructured surface is a promising photon management strategy to tune spectrum in design of the selective solar absorber.In this paper,we propose a nanocone structured surface as a perfect solar absorber in application of the solar thermoelectric generators(STEGs).The trade-off between the solar absorption and the mid-infrared emission is obtained to maximize the STEG efficiency.The effects of the geometric parameters,thermal concentration,incident angle and polarized state as well as the lattice arrangement are systematically investigated.The results show that the STEGs equipped with our proposed selective solar absorber can achieve a peak efficiency of 6.53%under AM1.5G condition(no optical concentration).Furthermore,the selective solar absorber exhibits insensitive behavior to the incident angle and polarization angle as well.This means that the proposed selective solar absorber can utilize solar energy as much as possible and be generally suitable in equipping the STEGs without optical concentration.

Optimization of Distributed Solar Photovoltaic Power Generation in Day-ahead Electricity Market Incorporating Irradiance Uncertainty

This paper proposes a simple and practical approach to model the uncertainty of solar irradiance and determines the optimized day-ahead(DA)schedule of electricity mar-ket.The problem formulation incorporates the power output of distributed solar photovoltaic generator(DSPVG)and forecasted load demands with a specified level of certainty.The proposed approach determines the certainty levels of the random variables(solar irradiance and forecasted load demand)from their probability density function curves.In this process of optimization,the energy storage system(ESS)has also been mod-eled based on the fact that the energy stored during low locational marginal price(LMP)periods and dispatched during high LMP periods would strengthen the economy of DA schedule.The objective of the formulated non-linear optimization problem is to maximize the social welfare of market participants,which incorporates the assured generation outputs of DSPVG,subject to real and reactive power balance and transmission capability constraints of the system and charging/dis-charging and energy storage constraints of ESS.The simulation has been performed on the Indian utility 62-bus system.The results are presented with a large number of cases to demonstrate the effectiveness of the proposed approach for the efficient,economic and reliable operation of DA electricity markets.

Effect of non-uniform illumination on performance of solar thermoelectric generators

Solar thermoelectric generators （STEGs） are heat engines which can generate electricity from concentrated sunlight. The non-uniform illumination caused by the optical concentrator may affect the performance of solar thermoelectric generators. In this paper, a three- dimensional finite element model of solar thermoelectric generators is established. The two-dimensional Gaussian distribution is employed to modify the illumination profiles incident on the thermoelectric generator. Six non-uniformities of solar illumination are investigated while keeping the total energy constant. The influences of non-uniform illumination on the temperature distribution, the voltage distribution, and the maximum output power are respectively discussed. Three thermoelectric generators with 32, 18 and 8 pairs of thermocouples are compared to investigate their capability under non-uniform solar radiation. The result shows that the non-uniformity of the solar illumination has a great effect on the temperature distribution and the voltage distribution. Central thermoelectric legs can achieve a larger temperature difference and generate a larger voltage than peripheral ones. The non-uniform solar illumination will weaken the capability of the TE generator, and the maximum output power decrease by 1.4% among the range of non-uniformity studied in this paper. Reducing the number of the thermoelectric legs for non-uniform solar illumination can greatly increase the performance of the thermoelectric generator.

Numerical Study on the Thermal Stress and its Formation Mechanism of a Thermoelectric Device

The strong thermo-mechanical stress is one of the most critical failure mechanisms that affect the durability of thermoelectric devices. In this study, numerical simulations on the formation mechanism of the maximum thermal stress inside the thermoelectric device have been performed by using finite element method. The influences of the material properties and the thermal radiation on the thermal stress have been examined. The results indicate that the maximum thermal stress was located at the contact position between the two materials and occurred due to differential thermal expansions and displacement constraints of the materials. The difference in the calculated thermal stress value between the constant and the variable material properties was between 3% and 4%. At a heat flux of 1 W·cm^(-2) and an emissivity of 0.5, the influence of the radiation heat transfer on the thermal stress was only about 5%; however, when the heat flux was 20 W·cm^(-2) and the emissivity was 0.7, the influence of the radiation heat transfer was more than 30%.