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This article addresses the contemporary challenges associated with the generation of electricity from solar panels, considering the diverse environmental conditions affecting efficiency. In response, various maximum power point tracking (MPPT) techniques are explored to optimize power generation. The study focuses on three MPPT techniques—perturb and observe, incremental conductance, and the beta method—in the context of solar water pump systems. Utilizing MATLAB software for analysis, this research compares the performance of these MPPT techniques to identify the most suitable approach for enhancing power generation in solar water pump applications. The findings highlight incremental conductance and the beta method as highly effective for operating solar water pump systems, providing valuable insights for enhancing their efficiency in real-world scenarios. This emphasizes the significance of utilizing optimized control strategies to improve the performance and reliability of solar water pumping technologies, thereby advancing sustainable water management practices across agricultural and rural environments. [ABSTRACT FROM AUTHOR]

Paying close attention to the environmental risks associated with traditional forms of energy, particularly the serious issue of global warming caused by the release and concentration of greenhouse gases, has become a paramount concern. This growing awareness has prompted governments worldwide to prioritize the benefits of alternative energy sources and develop comprehensive plans accordingly. Moreover, it is crucial to thoroughly consider and explore existing potentials in our quest for sustainable energy solutions. One such potential lies in the energy loss experienced due to gas pressure reduction in urban gas reduction stations. Furthermore, as we increase the amount of natural gas preheating, we observe a corresponding rise in the temperature within the expansion turbine, ultimately resulting in a significant boost in power generation. In this paper, we delve into the exciting possibility of harnessing electricity generation by utilizing a turbo expander within a municipal gas pressure reduction station. To maximize the work generation capacity, we propose preheating the gas input to the turbo expander using geothermal energy. Our study reveals that the turbo expander exhibits optimal performance, boasting an impressive isentropic efficiency of 92.3%, when the inlet temperature is maintained at 84 °C and the amount of preheating reaches 192.3 kJ/kg. [ABSTRACT FROM AUTHOR]

The Dutch climate agreement anticipates the large-scale implementation of solar and wind energy systems on land and water. Combining solar and wind farms has the benefit of multiple surface area use, and it also has the advantage of energy generation from both solar and wind energy systems, which is rather complementary in time; thus, a better balance can be found between electricity generation and demand and the load on the electricity grid. In combined solar and wind farms (CSWFs), the turbines will cast shadows on the solar panels. This concerns the static shadow from the construction tower of the turbine as well as the dynamic shadow caused by the rotating blades. This paper reports on the results of millisecond data monitoring of the PV farm of a CSWF in the Netherlands on land. Static and dynamic shadow effects are discussed, as well as their dependency on farm design. It is observed that the dynamic shade of the wind turbine blade causes serious disturbances of the DC inputs of the inverter, resulting in deviation of the maximum power point tracking monitored. The shadow of the wind turbine results in a total energy loss of about 6% for the given period, park configuration, PV modules, inverter type, and setting. [ABSTRACT FROM AUTHOR]

We utilize atomistic simulations that account for point charges and dipoles to demonstrate that flexoelectricity, which arises from strain gradients, can be exploited to generate electricity from crumpled graphene sheets. Indentation of a circular graphene sheet generates localized developable (d)-cones, for which we verify the core radius and azimuthal angle with established theoretical models. We determine the voltage that can be generated based on the resulting electrostatic fields and compare the voltage generation to previous theoretical predictions that are scaled down to the nanoscale. In doing so, we find that the voltage generated from crumpling graphene exceeds, by about an order of magnitude, the expected voltage generation, indicating the benefit of exploiting the large strain gradients that are possible at the nanoscale. Finally, we demonstrate that crumpling may be a superior mechanism of flexoelectric energy generation as compared to bending of two-dimensional nanomaterials. [ABSTRACT FROM AUTHOR]

Liquid sodium is an attractive working fluid for thermoacoustic conversion. Herein, a numerical study on a standing-wave thermoacoustic electricity generation system with liquid sodium as the working fluid is presented, based upon the Swift model. The characteristics of the thermoacoustic conversion and the output performance of the system have been investigated. The results show that the sodium engine can reach a power density much higher than the classical gas engine. Due to the strong acoustic coupling between components, the electricity output is significantly affected by the input heating power, the magnetic flux density, and the load ratio. In a typical case, the thermal-to-electric efficiency and the relative Carnot efficiency can reach 4.6% and 7.8%, respectively, with a temperature difference of 563 K and an input heat of 5 kW. More importantly, the output electricity density reaches 150 kW/m3, higher than some commercially available technologies. These results demonstrate the potential of such technology for small-scale electricity generation. Its extremely simple structure without any mechanical moving part endows the system with high reliability and long lifetime, if risks of corrosion and exposure to air and water can be avoided. [ABSTRACT FROM AUTHOR]

A transverse thermoelectric generator for magnetic-field-free and high-density power generation utilizing the anomalous Nernst effect is constructed and its performance is characterized. By alternately stacking two different permanent magnets with the large coercivity and anomalous Nernst coefficients of opposite sign, transverse thermoelectric voltage and power can be generated in the absence of external magnetic fields and enhanced owing to a thermopile structure without useless electrode layers. In the permanent-magnet-based stack, the magnetic attractive force enables easy construction of the thermopile structure with a high fill factor. In this study, we construct a bulk module consisting of 12 pairs of SmCo5- and Nd2Fe14B-type permanent magnets having positive and negative anomalous Nernst coefficients, respectively, whose fill factor reaches ∼80%, whereas that of conventional thermoelectric modules based on the Seebeck effect is typically 30%–60%. We demonstrate magnetic-field-free anomalous Nernst power generation up to 177 µW at a temperature difference of 75 K around room temperature, which corresponds to the largest anomalous Nernst power density of 65 µW/cm2. The presented module structure concept will provide a design guideline for high-performance transverse thermoelectric power generation. [ABSTRACT FROM AUTHOR]

We formulate a simple model for the power densities generated by thermoradiative devices based on narrow-gap semiconductors. Our model is more realistic than previous treatments because it includes the effects of both Auger (impact ionization) and Shockley–Read–Hall (SRH) processes on the generated power. For known materials and based on optimal values for the energy gap and operating bias, maximum possible power densities are estimated in the presence of strong nonradiative processes. In particular, we derive best-case numerical projections for thermoradiative devices based on III-V type-II superlattices and bulk HgCdTe operating at practical temperatures and having a range of SRH lifetimes. Devices with strong Auger suppression and configured in nonplanar architectures with limited geometric fill factor can in principle attain power densities per unit active area approaching 10 W/m2. However, practical limitations will more likely constrain the generation density to <1 W/m2, which is at least two orders of magnitude lower than for a typical solar cell. [ABSTRACT FROM AUTHOR]

A significant amount of low-grade heat (< 100 °C) can be found in various sources, such as geothermal/solar sources, industrial plants, vehicles, and biological entities, but it is often wasted due to the absence of cost-effective and efficient recovery technologies. Thermally regenerative electrochemical cycle (TREC) represents a promising solution for effectively harnessing low-grade heat. Rapid advancements in TREC chemistry, materials, and design have established the crucial foundations for high-power, efficient, and long-lasting TREC systems. However, evaluating the potential of reported TREC systems of different types is challenging due to the inconsistency in evaluation metrics and methods. In this Perspective, we examine the working principle of various TREC systems, including the electrically powered TREC systems, charging-free TREC systems that solely convert thermal energy to electrical energy, and TREC systems that simultaneously provide high-power energy storage and thermal energy conversion. The critical performance metrics for each of these three types of TREC systems, such as absolute/apparent thermoelectric efficiency, power density, net electricity generation, various forms of energy loss, and thermal energy input, are presented to compare the thermoelectric performance across different types of TREC systems at various scales. In addition, some practical methods for measuring the critical parameters, current challenges, and future directions for practical applications are also highlighted. [ABSTRACT FROM AUTHOR]

A renewable portfolio standard is implemented to promote the development of renewable energy at a minimum cost through tradable green certificate market mechanism. Formulating a scientific and feasible renewable energy quota allocation scheme helps RPS function smoothly and optimize resource allocation. This paper proposed a bi-level programming model combined with entropy weight method to allocate renewable portfolio standard quotas with provincial heterogeneity and stakeholders' behavior, and an optimized quota allocation scheme among China's 30 provinces in 2020 was obtained. By comparing with the government's issued scheme, the following were the results under the optimized scheme: (1) Quotas in most provinces have increased, and the responsibility for renewable electricity generation is shared with the provinces with developed economy and well-constructed transmission facilities, where electricity producers can meet the quotas by purchasing tradable green certificate. (2) Quota allocation has positive effects on energy, economy, and environment. Specifically, the non-hydro renewable electricity generation increased by 43.8%, the non-hydro renewable electricity producers' profit increased by 18.4%, and the environmental pollution cost reduced by 27.9%. (3) Quota allocation equity measured by the environmental Gini coefficient increased by 14.3%. Based on these findings, some policy implications related to quota allocation and renewable portfolio standard's institutional arrangement have been put forward. [ABSTRACT FROM AUTHOR]

Evaporation-driven spontaneous capillary flow presents a promising approach for driving electrolytes through electrically charged channels and pores in electrokinetic energy conversion devices. However, there are no literature reports of detailed flow visualization in these systems and/or experimental observations relating the liquid velocity and evaporation rate to the generated voltage and current. In this manuscript, we describe such a visualization study for a glass channel based electrokinetic energy conversion device with one of its channel terminals left open to ambient air for facilitating the evaporation process. Fluorescence microscopy was used to measure the liquid velocity in the electrokinetic energy conversion channel by observing the advancement of an electrolyte solution dyed with a neutral tracer. The accumulation of the same dye tracer was also imaged at the open terminal of this glass conduit to estimate the rate of solvent evaporation, which was found to be consistent with the flow velocity measurements. Additionally, an electrochemical analyzer was employed to record the electrical voltage and current produced by the device under different operating conditions. The highest electrical power output was derived in our experiments upon flowing de-ionized water through a 1 μm deep channel, which also produced the fastest liquid velocity in it. Moreover, the energy conversion efficiency of our device was observed to increase for shallower channels and lower ionic strength electrolytes, consistent with previous literature reports on electrokinetic energy conversion platforms. [ABSTRACT FROM AUTHOR]

Following the 3.15 MJ fusion milestone at the National Ignition Facility, the further development of inertial confinement fusion, both as a source for future electricity generation and for high-energy-density physics applications, requires the development of more robust ignition concepts at current laser facility energy scales. This can potentially be achieved by auxiliary heating the hotspot of low convergence wetted foam implosions where hydrodynamic and parametric instabilities are minimized. This paper presents the first multi-dimensional Vlasov–Maxwell and particle-in-cell simulations to model this collisionless interaction, only recently made possible by access to the largest modern supercomputers. The key parameter of interest is the maximum fraction of energy that can be extracted from the electron beams into the hotspot plasma. The simulations indicate that significant coupling efficiencies are achieved over a wide range of beam parameters and spatial configurations. The implications for experimental tests on the National Ignition Facility are discussed. [ABSTRACT FROM AUTHOR]

We proposed a model of the coupling system composed of a vacuum thermionic power generator and a near-field thermophotovoltaic cell. The coupling system can simultaneously convert electrons and photons into electricity. Expressions for the efficiency and power output density of the coupling system are analytically derived. The influences of external and internal irreversible losses on the performance of the coupling system are discussed. The working temperature of the anode is calculated through an energy balance equation. The maximum efficiency and power output density of the coupling system are found to be obviously larger than those of a single vacuum thermionic power generator or a near-field thermophotovoltaic cell. Some parametric selective criteria are supplied and the boundaries of optimized parameters are determined. The results obtained here will be helpful to the optimal design and actual development of near-field thermionic-thermophotovoltaic cells. [ABSTRACT FROM AUTHOR]

This study set out to examine the flash sintering of thermoelectric materials. A finite element method analysis of electric current activated/assisted sintering with an insulating mold suggested that the use of a sufficiently high Joule-heating rate, such as >10 000 K/s, relative to the thermal diffusion rate of the mold material, can realize uniform sample heating. Based on the analysis results, the sintering of Sb2Te3, a typical thermoelectric material, was conducted with a current feed duration of 1 s, using a sintering apparatus that had been specially devised for flash-sintering. Although a slight reduction in the density and degree of grain alignment was observed, the crystallographic phase was unaffected by the rapid heating, with the thermoelectric performance of the Sb2Te3 sample prepared by the 1-s sintering being comparable with that of a sample that had been conventionally sintered at 773 K for 3 min. This significant reduction in the sintering time can result in the energy consumption for the sintering process being decreased to less than 1% of that required for conventional current sintering. This significant energy-conservation effect of the flash sintering should be appealing from a practical point of view, especially for the fabrication of those thermoelectric materials used for power generation and aimed at energy recovery. [ABSTRACT FROM AUTHOR]

Studies have shown that surplus power from variable renewable electricity generation can be consumed in electric boilers or compressor heat pumps, i.e., Power-to-Heat (P2H), for heat production. This potentially provides power balancing for the electric grid and can also decarbonize and/or reduce biofuel demand in the district heating (DH) sector. This sector-coupling of thermal and electrical systems is, however, limited by production planning complexity, grid fees, tariffs, and risk-averse actors. The conditions for P2H production vary between DH-systems due to non-homogeneity in the configuration of production units in different systems. This study investigates the economic feasibility of placing bids for P2H electricity consumption on the reserve capacity market in three different DH systems. It is assumed that P2H electricity consumption is controlled by a hypothetical balance operator. To increase production flexibility, the DH systems are equipped with heat storage where P2H-produced heat is stored. The results show that P2H on the reserve capacity market can increase revenue for DH operators, but DH systems with co-generation of heat and electricity risk reducing income from power production. Furthermore, stored heat needs to compete with cost-efficient base-load production to avoid the large storage required. The power balancing potential of P2H in DH systems is generally limited by the installed P2H capacity as well as the rest of the constituents and the production strategy of the DH system. To overcome these limitations, policies are needed that reward power balancing services and provide investment support for P2H capacity and heat storage. [ABSTRACT FROM AUTHOR]

Solar thermal electricity generation is one of the encouraging technologies for reducing scarcity of electricity worldwide in a renewable and sustainable manner. Solar organic Rankine cycles (SORCs) are sustainable and an eco-friendly means of power production at low- and medium-heat source temperatures. The proposed system includes a parabolic trough collector based solar system, which operates with Therminol VP-1 oil, a two-tank direct thermal energy storage unit, and an organic Rankine cycle (ORC) operates with a working fluid Toluene. Improvement in efficiencies of components has a cascading benefit in the performance of SORC, operating costs, and payback period. A comparative energy and exergy analysis study is performed to assess the thermodynamic performance of subcritical non-recuperative solar organic Rankine cycle on the basis of heat source temperatures and ORC operating parameters. Iterative procedure is adapted in the analysis to find optimal operating parameters to maximize efficiency. Maximum energetic and exergetic efficiencies of SORC are calculated at various optimal T5 and pevp. Variations of optimal mass flow rate values with respect to time and ηI, ηII with respect to heat source temperatures are plotted. In all, the energy efficiency of the overall system remained almost the same, when the proposed system is operated at the exergy-based vs energy-based optimal operating conditions. However, significant enhancement of 6.61% and 12.42% in exergetic efficiency of ORC and overall system, respectively, are observed when SORC operates at exergy-based optimal operating conditions. [ABSTRACT FROM AUTHOR]

In this paper, a carbon fiber array cathode was constructed and the application in a hard-tube magnetically insulated transmission line oscillator (MILO) was investigated. The performance was compared with a traditionally used polymer velvet cathode in the same conditions, where applied electric power ranged from 9GW to 28GW and microwave with power level of several GW was the output. The MILO worked on single shot mode or repetitive mode at 5 Hz. For both cathodes, the central frequencies of output microwaves are in the L-band, and the pulse durations (full width at half maximum) range from 25 to 50 ns. Experimental results show that the pulse duration of output microwave of the carbon fiber array cathode is shorter than the velvet cathode, and the power conversion efficiency is also somewhat lower than the velvet cathode. Although the performance testing results show that this carbon fiber array cathode is somewhat not as good as the traditional velvet cathode in the present state, the reasons for the disadvantages of the carbon fiber array cathode have been analyzed and the corresponding solutions are presented to improve the performance of this cathode. If expected solutions are put into effect, this carbon fiber array cathode may be able to replace the velvet cathode. [ABSTRACT FROM AUTHOR]

A large fraction of the world's population lacks access to the electric grid. Standard photovoltaic (PV) cells can provide a renewable off-grid source of electricity but only produce power from daytime solar irradiance and do not produce power at night. While there have been several theoretical proposals and experimental demonstrations of energy harvesting from the radiative cooling of a PV cell at night, the achieved power density is very low. Here, we construct a device, which incorporates a thermoelectric generator that harvests electricity from the temperature difference between the PV cell and the ambient surrounding. We achieve 50 mW/m2 nighttime power generation with a clear night sky, with an open-circuit voltage of 100 mV, which is orders of magnitude higher as compared with previous demonstrations. During the daytime, the thermoelectric generator also provides additional power on top of the electric power generated directly from the PV cells. Our system can be used as a continuous renewable power source for both day- and nighttime in off-grid locations. [ABSTRACT FROM AUTHOR]

For each geographical region, one of the biggest challenges in reaching a zero-carbon grid is identifying sources of electricity that match the seasonal profile of the load. Summer-dominant solar electricity generation can often be balanced by winter-dominant wind electricity generation. Together with long-duration storage, balanced solar and wind generation are well positioned to provide reliable renewable electricity. However, in some locations the wind may not complement solar energy so well. For example, currently California's wind turbines produce more electricity during summer than winter, raising the question of whether all future wind plants in California will exhibit the same seasonality. As a response to this question, in this paper, we analyzed the generation from existing California wind plants and simulated potential onshore wind resource for the whole state using a metric that reflects the relative wind resource in winter. Our results indicate that the seasonality of the wind can vary for very small spatial difference with more than half of California showing stronger wind resource in the winter compared with the summer despite the current observation of the opposite trend. This study differentiates the seasonality of potential wind resources to inform the creation of a reliable, 100%-renewable-driven grid. [ABSTRACT FROM AUTHOR]

Korea has announced its goal of achieving net zero carbon emissions by 2050 by accelerating its shift toward renewable energy. We examined the effects of increasing renewable energy use on the demands for fossil fuels and the power supply price for the Korean electric power generation sector. Using the estimated price elasticities of demand between energy inputs, we can calculate that a 1% increase in renewable energy would lead to a 0.06%, 0.35%, and 0.17% lower demand for coal, oil, and gas, respectively, ceteris paribus, possibly resulting in a potential CO2 reduction by as much as 0.173 × 106 tons in total. The null hypothesis of no contribution of increasing renewable energy on power generation costs was rejected. The simulation results show that renewable energy generation costs did not increase sufficiently to cause the power supply price to rise significantly over the period 2000–2015. [ABSTRACT FROM AUTHOR]

Organic photovoltaics (OPVs) are regarded as promising for solar-electric conversion with steadily improving power conversion efficiencies. For further progress, it is crucial to understand and mitigate defect states (traps) residing in the band-gap of OPV materials. In this work, using capacitance measurements, we analyzed two major bands in the density of states (DOS) energy spectra of defects in poly(3-hexylthiophene) (P3HT); regio-regular and regio-random species of P3HT were compared to elucidate the role of morphological disorder. To accurately interpret the obtained DOS profile, trap emission prefactors and activation energy were extracted from temperature dependent capacitance-frequency measurements, while doping, Fermi energy, built-in voltage, and energy levels of the defects were extracted from capacitance-voltage measurements. We identified that the lower energy band-misinterpreted in literature as a defect distribution-stems from free carrier response. The higher energy defect distribution band for regio-random P3HT was an order of magnitude higher than region-regular P3HT, thus stemming from morphological disorder. Impedance spectroscopy was also employed for further comparison of the two P3HT species. [ABSTRACT FROM AUTHOR]

The pyroelectricity of polar materials provides great potential for electricity generation from waste heat. The pyroelectric effect of the material can be magnificently enhanced at a first-order phase transformation due to the abrupt jump in spontaneous polarization within a narrow temperature range. Here, we show that the performance of energy conversion by phase transformation is inversely resonant with the hysteresis of thermally driven structural transformations in a (Ba1−xSrx) (Hf0.02Ce0.005Ti0.975)O3 system, corresponding to a singular lattice distortion mode satisfying the crystallographic compatibility condition. Among the finely tuned Sr compositions from 0.04 to 0.10, we discovered that Sr0.07 composition is a promising material candidate in this material system for pyroelectric energy conversion. Our work suggests a rational strategy of material development for pyroelectric energy conversion applications. [ABSTRACT FROM AUTHOR]

Energy storage systems (ESS) can offer significant benefits to electricity systems and hence to society. Some of them include avoiding the costs of expensive centralized electricity generation and its environmental impact. However, existing electricity market arrangements aiming at rewarding these benefits present large externalities and therefore fail to reward well the true societal benefits of energy storage. In particular, ESS could be operated to avoid the emissions of polluting centralized generation. Thus, ESS could also avoid the damage cost of those emissions such as the social cost of climate change and the damage on population health. These large externalities are likely much higher than typically seen carbon taxes and prices. In this paper, we present an empirical assessment of the locational societal benefits of energy storage in a real electricity system that has a significant presence of solar and hydro power generation, and important transmission constraints. The assessment is performed via a linear programming model that is applicable for small scale ESS. Major conflicts were found between energy and emission arbitrage in zones with hydrothermal generation, yet strong synergies in zones with high solar generation. Transmission congestion has a significant impact on this. Energy storage benefits associated with the provision of reserve services are the highest source of societal benefit. Finally, it is shown that a battery system may be an attractive investment from a societal perspective. [ABSTRACT FROM AUTHOR]

An experimental demonstration of the combined photovoltaic (PV) and thermoelectric conversion of concentrated sunlight (with concentration factor, X, up to ~300) into electricity is presented. The hybrid system is based on a multi-junction PV cell and a thermoelectric generator (TEG). The latter increases the electric power of the system and dissipates some of the excessive heat. For X≤200, the system's maximal efficiency, ~32%, was mostly due to the contribution from the PV cell. With increasing X and system temperature, the PV cell's efficiency decreased while that of the TEG increased. Accordingly, the direct electrical contribution of the TEG started to dominate in the total system power, reaching ~20% at X ≈ 290. Using a simple steady state finite element modeling, the cooling effect of the TEG on the hybrid system's efficiency was proved to be even more significant than its direct electrical contribution for high solar concentrations. As a result, the total efficiency contribution of the TEG reached ~40% at X ≈ 200. This suggests a new system optimization concept that takes into account the PV cell's temperature dependence and the tradeoff between the direct electrical generation and cooling capabilities of the TEG. It is shown that the hybrid system has a real potential to exceed 50% total efficiency by using more advanced PV cells and TE materials. [ABSTRACT FROM AUTHOR]

II–VI semiconductors are used in numerous electro-optical applications. For example, CdTe-based solar technology is cost competitive with other electricity generation sources, yet there is still significant room to improve. Carrier lifetime has historically been well below the radiative recombination limit. Lifetimes reaching beyond 100 ns can significantly enhance performance and enable novel device structures. Here, double heterostructures (DHs) with passivated interfaces demonstrate lifetimes exceeding 1 μs, yet this appears only for CdSeTe and not for CdTe DHs. We compare the passivation mechanisms in CdTe and CdSeTe DHs. CdSeTe lifetimes on the order of 1 μs correspond to a combination of superior intragrain lifetime, extremely low grain boundary recombination and greater Te4+ interfacial presence compared to CdTe. [ABSTRACT FROM AUTHOR]

This paper conducts a systemic comparative study on univariate and multivariate wind power forecasting for five wind farms inside the Arctic area. The development of wind power in the Arctic can help reduce greenhouse gas emissions in this environmentally fragile region. In practice, wind power forecasting is essential to maintain the grid balance and optimize electricity generation. This study first applies various learning methods for wind power forecasting. It comprehensively compares the performance of models categorized by whether considering weather factors in the Arctic. Nine different representative types of machine-learning algorithms make several univariate time series forecasting, and their performance is evaluated. It is demonstrated that machine-learning approaches have an insignificant advantage over the persistence method in the univariate situation. With numerical weather prediction wind data and wind power data as inputs, the multivariate forecasting models are established and made one to six h in advance predictions. The multivariate models, especially with the advanced learning algorithms, show their edge over the univariate model based on the same algorithm. Although weather data are mesoscale, they can contribute to improving the wind power forecasting accuracy. Moreover, these results are generally valid for the five wind farms, proving the models' effectiveness and universality in this regional wind power utilization. Additionally, there is no clear evidence that predictive model performance is related to wind farms' topographic complexity. [ABSTRACT FROM AUTHOR]

For over two decades, the quest for decentralized electric power generation has stimulated much research interest into the Savonius (or S-type) wind turbine rotors. To enhance their efficiency, the operating parameters have already been examined by various numerical and experimental techniques. While most researchers have focused on using selected turbulence models to arrive at some meaningful conclusions and recommendations, no study analyzing a range of turbulence models in a systematic and comprehensive manner is reported. This study thus aims at conducting 2-D unsteady numerical simulations of a conventional semicircular-bladed Savonius rotor using six different turbulence models, viz., standard k–ε, realizable k–ε, RNG k–ε models, standard k–ω and shear stress transport (SST) k–ω, and transition SST (TSST) turbulence models. The simulations are performed by commercial finite-volume method solver ANSYS Fluent 17.1 at a fixed Reynolds number (Re) of 1.23 × 105 based on the rotor overall diameter. This study demonstrates the prediction capabilities of realizable k–ε, RNG k–ε, SST k–ω, and TSST models more accurately than those of other models. However, due to higher computational cost associated with TSST model, the use of realizable k–ε, RNG k–ε, and SST k–ω models for predicting the aerodynamic performance of other developed and to-be-developed profiles of Savonius rotor is recommended. [ABSTRACT FROM AUTHOR]

In this paper, a new approach is proposed to control the operation of a thermoacoustic Stirling electricity generator. This control basically consists in adding an additional acoustic source to the device, connected through a feedback loop to a reference microphone, a phase-shifter, and an audio amplifier. Experiments are performed to characterize the impact of the feedback loop (and especially that of the controlled phase-shift) on the overall efficiency of the thermal to electric energy conversion performed by the engine. It is demonstrated that this external forcing of thermoacoustic self-sustained oscillations strongly impacts the performance of the engine, and that it is possible under some circumstances to improve the efficiency of the thermo-electric transduction, compared to the one reached without active control. Applicability and further directions of investigation are also discussed. [ABSTRACT FROM AUTHOR]

Cu2ZnSn(S,Se)4 (CZTSSe) is an earth-abundant semiconductor with potential for economical photovoltaic power generation at terawatt scales. In this work, we use Raman scattering to investigate phase coexistence in combinatorial CZTS thin films grown at 325 or 470°C. The surface of the samples grown at 325°C is rough except for a prominent specularly reflective band near and along the ZnS-Cu2SnS3 (CTS) tie line in the Cu-Zn-Sn-S quaternary phase diagram. All structurally incoherent secondary phases (SnS2, CuS) exist only as surface phases or are embedded as separate grains, whereas the structurally coherent secondary phase CTS coexists with CZTS in the dense underlying film. In films grown at 325°C, which are kinetically trapped by the low growth temperature, a change is observed in Cu and Sn site occupancy, evidenced by the shift from cubic-CTS in the Cu-rich region (Cu/Sn>2) to more tetragonal-CTS in the Sn-rich region (Cu/Sn<2). For CZTS samples grown at 470° C, CTS is not observed and regions grown under excess Sn flux are more disordered than Cu-rich regions evidenced by broader CZTS A mode peaks. Therefore, increasing Sn chemical potential results in more CZTS lattice disorder, suggesting, with other evidence, the formation of Sn antisite defects. In contrast, the CZTS A mode breadth is insensitive to Zn richness suggesting that excess Zn does not induce significant disorder within the CZTS lattice. We postulate that initially growing CZTS films Cu-rich (Cu/Sn>2) results in higher cation ordering meaning fewer antisite defects. [ABSTRACT FROM AUTHOR]

A theoretical framework for studying signal and noise in multiple-stage interband infrared photovoltaic devices is presented. The theory flows from a general picture of electrons transitioning between thermalized reservoirs. Making the assumption of bulk-like absorbers, we show how the standard semiconductor transport and recombination equations can be extended to the case of multiple-stage devices. The electronic noise arising from thermal fluctuations in the transition rates between reservoirs is derived using the Shockley-Ramo and Wiener-Khinchin theorems. This provides a unified noise treatment accounting for both the Johnson and shot noise. Using a Green's function formalism, we derive consistent analytic expressions for the quantum efficiency and thermal noise in terms of the design parameters and macroscopic material properties of the absorber. The theory is then used to quantify the potential performance improvement from the use of multiple stages. We show that multiple-stage detectors can achieve higher sensitivities for applications requiring a fast temporal response. This is shown by deriving an expression for the optimal number of stages in terms of the absorption coefficient and absorber thicknesses for a multiple-stage detector with short absorbers. The multiple-stage architecture may also be useful for improving the sensitivity of high operating temperature detectors in situations where the quantum efficiency is limited by a short diffusion length. The potential sensitivity improvement offered by a multiple-stage architecture can be judged from the product of the absorption coefficient, α, and diffusion length, Ln, of the absorber material. For detector designs where the absorber lengths in each of the stages are equal, the multiple-stage architecture offers the potential for significant detectivity improvement when αLn ≤ 0.2. We also explore the potential of multiple-stage detectors with photocurrent-matched absorbers. In this architecture, the absorbers are designed to absorb and collect an equal number of carriers in each stage. It is shown that for zero-bias operation, this design has a higher ultimate detectivity than a single-absorber device. Such improvements in detectivity are significant for material with αLn ≤ 0.5. Using the results derived for general values of αLn, we offer an outlook for multiple-stage detectors that utilize InAs/GaSb superlattice absorbers. [ABSTRACT FROM AUTHOR]

We present a methodology for estimating the efficiency potential for candidate impurity-band photovoltaic materials from empirical measurements. This methodology employs both Fourier transform infrared spectroscopy and low-temperature photoconductivity to calculate a 'performance figure of merit' and to determine both the position and bandwidth of the impurity band. We evaluate a candidate impurity-band material, silicon hyperdoped with sulfur; we find that the figure of merit is more than one order of magnitude too low for photovoltaic devices that exceed the thermodynamic efficiency limit for single band gap materials. [ABSTRACT FROM AUTHOR]

Energy conversion by water flowing over graphene is a promising mode of energy harvesting. However, the mechanism, energy-conversion efficiency, and quantification of power density for this mode of interfacial electricity generation remain unknown. Quantification of the output performance for the flow-induced electricity generation using graphene is presented in this work. The output performance per unit contact area between water and graphene is found to be proportional to the flow speed, with an electromotive force density of 0.0025 [ μ V / mm 2 / mm / s ] for the conditions used in this work. The ability to quantify output density will help to construct guidelines for future applications of this form of electricity generation. [ABSTRACT FROM AUTHOR]

Sustainable, efficient, and affordable energy supply embraces a strong relationship with socio-economic development, specifically in developing countries. Pakistan has been facing an energy crisis in the form of expensive electricity generation by largely depending upon fossil fuels and experiencing power shortages. This paper offers a thorough analysis of Pakistan's renewable energy (hereinafter RE) potential and current practices, in trying to meet its energy demands. There is a limited academic discussion available concerning the utilization of RE resources of Pakistan to produce cost-effective and cost-competitive energy, including the formulation of pertinent laws and policies. This study adopts qualitative means to investigate global trends and current practices in renewables, followed by concrete observations and recommendations to improve the situation in Pakistan. The objective of the study is, therefore, to establish the significance of renewables and to examine possible solutions available to the government of Pakistan in addressing its energy crisis. The study concludes by suggesting that there is an urgent need to follow the global trend in replacing conventional energy methods with the country's extensive RE resources in order to ensure sustainable economic security and growth. [ABSTRACT FROM AUTHOR]

Solar power tower system with an external receiver is one of the most promising technologies for electricity generation and has a high concentration ratio and a high operating temperature range. In this paper, a lab-scale external receiver with xenon lamps, using molten salt as a heat transfer fluid, was established, and its optical and thermodynamic properties were evaluated. Experimental and numerical methods were used to analyze the performance of the receiver. For the base case (100% light power, no wind, 2.3 kg/s mass flow, and 400 °C inlet temperature), the deviation in the maximum temperature of the wall determined through numerical simulation and thermal imager measurement was 1.8%; the deviation in the back temperature of the receiver identified through simulation and thermocouple measurement was 0.22%. The performance of the receiver under different working conditions was also explored. Experimental and simulation results had good agreement at different mass flow rates, light power, and wind speed, and the deviation under each condition was less than 5%. The experimental results showed that the temperature rise of molten salt increased from 4.3 °C to 7.4 °C when the inlet temperature increased from 375 °C to 500 °C; the temperature rise of molten salt increased from 1.8 °C to 5.3 °C when the power of the xenon lamps increased from 20% to 100%; the temperature rise of molten salt decreased from 8.3 °C to 5.3 °C when the mass flow rate increased from 1.4 kg/s to 2.3 kg/s; and the temperature rise of molten salt decreased from 5.3 °C to 3.6 °C when the wind velocity increased from 0 to 10 m/s. The practical and simulation results present useful reference sources for fellow researchers and practitioners in the sector of the solar power tower system. [ABSTRACT FROM AUTHOR]

This work presents a localization study for the implementation of a solar power plant in Brazil using systems with Stirling engines and parabolic dish concentrators, also known as Dish-Stirling systems. The demand for electricity in the world is constantly growing, and this will likely double over the next 40 years, creating an electrical energy deficit scenario that can be filled with renewable and clean sources. The electric power generation system presented in this paper is formed by the parabolic dish concentrator and a receiver, where the Stirling engine and the power generator are located. The Dish-Stirling system presents the greatest efficiency in the conversion of heat to electrical energy when compared to other thermal concentration technologies. The localization study employed several criteria to select the most suitable place for the implementation of the power plant. The weights of these criteria were defined with the application of the Analytic Hierarchy Process. After determining the weights of each criterion, the localization study was carried out using a Geographic Information Systems (GIS) tool in three cities of different regions of Brazil. Fuzzy logic was used to implement the thresholds for each subcriterion in the GIS system. Research in Brazil about thermal conversion with Dish-Stirling systems is still incipient. Therefore, this work intends to demonstrate the potential of solar energy in Brazil and pinpoint available locations for future projects. The municipality of Bom Jesus da Lapa in the State of Bahia stood out in comparison with the other cities evaluated in this paper. [ABSTRACT FROM AUTHOR]

This work presents a simple, easily applicable macroscopic model for the simulation of the plasma effect on the fluid flow and the heat transfer, in a Dielectric Barrier Discharge (DBD) reactor used for environmental applications, such as soil remediation and biosolid stabilization. The model uses inputs that are easy to obtain experimentally, such as the inlet flow rate, electric power consumption, and reduction in the moisture of the treated specimen, in order to provide information on features that are difficult to measure, such as the temperature distribution in the plasma region and inside the specimen. The model is presented here through the simulation of a floating-electrode DBD process, and the results are compared with experimental data. For the simulation, the reactor's exact geometry is reconstructed in the computational domain, conjugate heat transfer is considered between the flowing air and the solid components, and the treated biosolid is modeled as a porous material. The findings show that, within the selected operating window, the temperature increase in the plasma area and inside the biosolid does not exceed 100 K. Such information is crucial for the assessment of the physicochemical modification of the specimen under treatment and the suitability of the treatment procedure for targeted applications. [ABSTRACT FROM AUTHOR]

Organo-metal lead halide perovskite solar cells (PSCs) attract attention due to their low cost and high power conversion efficiency. Some weak points of this technology are short lifetime, instability, and expensive metal electrode deposition. Eliminating the unstable hole transport layer (HTL) and using carbon-based materials as the counter electrode would address both. In this work, we present a cradle-to-gate life cycle assessment of two HTL-free PSC designs, which use solution phase deposition to achieve mesoscopic and planar structures. Environmental impacts of producing 1 m2 PSCs are converted to impacts per kWh electricity generation assuming 5 years of operational lifetime. We find that major impacts come from fluorine doped tin oxide (FTO) glass patterning due to the electricity consumption of FTO patterning and glass cleaning processes. Even though the electricity consumption when manufacturing both PSCs is similar, their different efficiencies make the environmental impacts per kWh of electricity higher for the mesoscopic PSC than for the planar PSC. Energy payback time values of planar PSCs and mesoscopic PSCs are 0.58 and 0.74 years, respectively, and these values are shorter than those of commercial first and second generation solar cells. However, the global warming potential (GWP) values of planar and mesoscopic PSCs are 75 and 94 g CO2-eq/kWh, respectively, and these values are still higher than those of commercial solar cells. To reach the GWP of commercial cells, the operational lifetime would have to be 8 and 10 years for planar and mesoscopic PSCs, respectively. [ABSTRACT FROM AUTHOR]

In this article, the photovoltaic (PV) and sun-tracking performance of single-axis multiposition sun-tracking PV panels (MP-PV) is investigated based on solar geometry and dependence of PV conversion efficiency on the incident angle of solar rays on PV panels. For such PV systems, the azimuth angle of the PV panels is adjusted daily M times from an eastward direction in the morning to a westward direction in the afternoon by rotating the PV panels about the inclined north–south axis (INSA) to ensure that the projected incident angle (PIA) of solar rays on the plane perpendicular to the INSA is always less than the angle θa, the specified maximum PIA. Results show that the annual average sun-tracking efficiency (η s t ) and the annual electricity generation (AEG) of the MP-PV system increase as M increases, but this increase is less than 1% when M > 5. The optimal θa of the MP-PV system for maximizing AEG and the ratio (Cp,MP-0) of AEG of the optimized MP-PV system to that of a similar fixed PV system are highly dependent on the annual average atmospheric clearness index (Kt) but only slightly dependent on the site latitude (λ). For an MP-PV with a tilt angle (β) of the INSA that is fixed yearly, the AEG of 3P-, 5P-, and 7P-PV systems is about 92%, 94%, and 95%, respectively, of that obtained from a similar dual-axis tracking PV panel (2A-PV). However, for an MP-PV whose β is adjusted four times a year at three tilts, the AEG of 3P-, 5P-, and 7P-PV systems is about 96%, 98%, and 99%, respectively, of that of a similar 2A-PV system. Empirical correlations for quick estimation of the optimal θa and Cp,MP-0 of the MP-PV optimized for maximizing AEG are suggested and examined based on monthly global radiation on the horizon at 30 sites around China. [ABSTRACT FROM AUTHOR]

In modern electric power networks with fast evolving operational conditions, assessing the impact of contingencies is becoming more and more crucial. Contingencies of interest can be roughly classified into nodal power disturbances and line faults. Despite their higher relevance, line contingencies have been significantly less investigated analytically than nodal disturbances. The main reason for this is that nodal power disturbances are additive perturbations, while line contingencies are multiplicative perturbations, which modify the interaction graph of the network. They are, therefore, significantly more challenging to tackle analytically. Here, we assess the direct impact of a line loss by means of the maximal Rate of Change of Frequency (RoCoF) incurred by the system. We show that the RoCoF depends on the initial power flow on the removed line and on the inertia of the bus where it is measured. We further derive analytical expressions for the expectation and variance of the maximal RoCoF, in terms of the expectations and variances of the power profile in the case of power systems with power uncertainties. This gives analytical tools to identify the most critical lines in an electric power grid. [ABSTRACT FROM AUTHOR]

The conversion of solar power into electricity is dominated by non-concentrating photovoltaics and concentrating solar thermal systems. Recently, it has been shown that solar thermoelectric generators (STEGs) are a viable alternative in the non-concentrating regime. This paper addresses the possibility of STEGs being used as the power block in concentrating solar power systems. STEG power blocks have no moving parts, they are scalable, and they eliminate the need for an external traditional thermomechanical generator, such as a steam turbine or Stirling engine. Using existing skutterudite and bismuth telluride materials, concentrating STEGs can have efficiencies exceeding 10% based on a geometric optical concentration ratio of 45. [ABSTRACT FROM AUTHOR]

Solar energy is the most abundant and reliable source of energy we have to provide for the multi-terawatt challenge we are facing. Although huge, this resource is relatively dispersed. High conversion efficiency is probably necessary for cost effectiveness. Solar cell efficiencies above 40% have been achieved with multijunction (MJ) solar cells. These achievements are here described. Possible paths for improvement are hinted at including third generation photovoltaics concepts. It is concluded that it is very likely that the target of 50% will eventually be achieved. This high efficiency requires operating under concentrated sunlight, partly because concentration helps increase the efficiency but mainly because the cost of the sophisticated cells needed can only be paid by extracting as much electric power form each cell as possible. The optical challenges associated with the concentrator optics and the tools for overcoming them, in particular non-imaging optics, are briefly discussed and the results and trends are described. It is probable that optical efficiency over 90% will be possible in the future. This would lead to a module efficiency of 45%. The manufacturing of a concentrator has to be addressed at three levels of integration: module, array, and photovoltaic (PV) subfield. The PV plant as a whole is very similar than a flat module PV plant with two-axes tracking. At the module level, the development of tools for easy manufacturing and quality control is an important topic. Furthermore, they can accommodate in different position cells with different spectral sensitivities so complementing the effort in manufacturing MJ cells. At the array level, a proper definition of the nameplate watts, since the diffuse light is not used, is under discussion. The cost of installation of arrays in the field can be very much reduced by self aligning tracking control strategies. At the subfield level, aspects such as the self shadowing of arrays causes the CPV subfields to be sparsely packed leading to a ground efficiency, in the range of 10%, that in some cases will be below that of fixed modules of much lower cell efficiency. All this taken into account, High Concentration PV (HCPV) has the opportunity to become the cheapest of the PV technologies and beat the prevalent electricity generation technologies. Of course the way will be paved with challenges, and success is not guaranteed. [ABSTRACT FROM AUTHOR]

The search for thermoelectric materials for power generation and for solid-state cooling has led to increased interest of layered cobalt-containing oxides because of their thermal stability at high temperature and their desirable thermoelectric properties. This paper examines the effect of substitution of Co in the layered pervoskite Ba2Ho(Cu3-xCox)O6+y (x=0.3, 0.4, 0.5, 0.6, and 1.0). Structural analysis using the neutron Rietveld refinement technique reveals that when x≤0.4, Co substitutes mainly for Cu in the “chain sites” of the Ba2Ho(Cu3-xCox)O6+y structure. As x>0.4, Co also enters in the Cu-O “plane sites” as well. The thermoelectric properties of polycrystalline Ba2Ho(Cu3-xCox)O6+y samples were studied in the temperature range of 10–390 K. In general, as the cobalt content x increases, the resistivity and Seebeck coefficient of these samples increase while the thermal conductivity decreases. Among the five Ba2Ho(Cu3-xCox)O6+y compositions, the x=0.4 member gives the highest figure of merit ZT of ≈0.02 at approximately 270 K. [ABSTRACT FROM AUTHOR]

The search for thermoelectric materials for power generation and for solid-state cooling has led to increased interest of layered cobalt-containing oxides because of their thermal stability at high temperature and their desirable thermoelectric properties. This paper examines the effect of substitution of Co in the layered pervoskite Ba2Ho(Cu3-xCox)O6+y (x=0.3, 0.4, 0.5, 0.6, and 1.0). Structural analysis using the neutron Rietveld refinement technique reveals that when x≤0.4, Co substitutes mainly for Cu in the “chain sites” of the Ba2Ho(Cu3-xCox)O6+y structure. As x>0.4, Co also enters in the Cu-O “plane sites” as well. The thermoelectric properties of polycrystalline Ba2Ho(Cu3-xCox)O6+y samples were studied in the temperature range of 10–390 K. In general, as the cobalt content x increases, the resistivity and Seebeck coefficient of these samples increase while the thermal conductivity decreases. Among the five Ba2Ho(Cu3-xCox)O6+y compositions, the x=0.4 member gives the highest figure of merit ZT of ≈0.02 at approximately 270 K. [ABSTRACT FROM AUTHOR]

We describe a radio-frequency (rf) electromagnetic-field-assisted magnetohydrodynamic power generation experiment, where an inductively coupled rf field (13.56 MHz, 5.2 kW) is continuously supplied to the disk generator. The rf power assists the precise plasma ignition, by which the otherwise irregular plasma behavior was stabilized. The rf heating suppresses the ionization instability in the plasma behavior and homogenizes the nonuniformity of the plasma structures. The power-generating performance is significantly improved with the aid of the rf power under wide seeding conditions: insufficient, optimum, and excessive seed fractions. The increment of the enthalpy extraction ratio of around 2% is significantly greater than the fraction of the net rf power, that is, 0.16%, to the thermal input. [ABSTRACT FROM AUTHOR]

We have investigated the thermal and electrical properties of filled skutterudites belonging to the series Ce1-zYbzFe4Sb12 and Cey/2Yby/2Fe4-x(Co/Ni)xSb12, as well as their potential for thermoelectric power generation. In the first series, increasing the Yb fraction decreases the resistivity and thermopower. These effects are related to the variations of valence of Yb with the Yb fraction (from 2.2 in Yb0.92Fe4Sb12 to 2.7 in Ce0.85Yb0.05Fe4Sb12). The power factor is increased in Ce0.40Yb0.53Fe4Sb12 while the thermal conductivity is reduced and this leads to an improved figure of merit in this compound when compared to Ce0.85Fe4Sb12. Co or Ni substitution was used to tune the carrier concentration and improve the power factor: we measure a ZT=0.5 at 500 K in Ce0.44Yb0.32Fe3.02Co0.98Sb12 and an extrapolation leads to ZT=0.95 at 800 K, which is close to state-of-the-art Ce0.28Fe1.52Co2.48Sb12 although the composition is far from being optimized. Double filling happens to be a promising path to provide good thermoelectric performances. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate electric power generation from the coldness of the universe directly, using the negative illumination effect when an infrared semiconductor diode faces the sky. Our theoretical model, accounting for the experimental results, indicates that the performance of such a power generation scheme is strongly influenced by the degree of matching between the responsivity spectrum and the atmospheric transparency window, as well as the quantum efficiency of the diode. A Shockley-Queisser analysis of an ideal optimized diode, taking into consideration the realistic transmissivity spectrum of the atmosphere, indicates the theoretical maximum power density of 3.99 W/m2 with the diode temperature at 293 K. The results here point to a pathway towards night-time power generation. [ABSTRACT FROM AUTHOR]

The development of a method to simulate desired approach turbulence characteristics and improve the typhoon resistance ability for complex building and transmission tower-line system in a multiple controlled fan wind tunnel is described. A case study is investigated using a closed-circuit single controlled fan wind tunnel model of the Full-Scale Test Facility at the State Grid Fujian Electric Power Research Institute for State Grid Wind Tunnel Laboratory. A small-scale model of the closed-circuit single controlled fan wind tunnel is designed and established to simulate the turbulence characteristics and develop the target turbulent flow generating methods efficiently. The results reveal that the value of the maximum average wind speed can reach 18.2 m/s and the maximum circular frequency is 7 Hz. Here, the mean wind speed of the sinusoidal wave flow is 15.1 m/s at the peak of amplitude of 3.8 m/s. The generated sinusoidal wave flow has a high correlation coefficient at 94.3% with the target. [ABSTRACT FROM AUTHOR]

Currently, existing technologies of energy generation based on fossil fuels and production processes of crude oil usually accompanied by flaring of gases resulted in excessive CO2 emissions. Kingdom of Saudi Arabia (KSA) national oil consumption is increasing by 7% annually. If this growth rate continues, local demands will be doubled in a decade. This study has covered various renewable energy solutions such as solar thermal hybrid solutions, photovoltaic cells/arrays, and wind turbines. A selection of possible applications of sustainable buildings, wind farming, solar energy, and their futures are discussed. From the crisis viewpoint of energy and environment safety, architectural trends have shifted toward sustainability demands. Energy and ecology were impetus to improve the residents' life quality and health standards. The climate/building correlation has been established to observe the response between both of them. Five distinguished coastal locations in KSA have given the consideration for wind farms, where meteorological data have been recorded since 1970. In contrast to the hot and irksome weather, water misting systems are elaborated to settle a soothing atmosphere. The results are noticed for evaporation and robbing the excessive heat. It is known that health is dependent on clean and unpolluted air, and the pollution has a threat for public health everywhere. So, an induction of renewable energy future has been considered. Gas turbine technology is also discussed as it accounts for about half of the overall capability of the KSA's power generation. Temperature, humidity, and pressure conditions have been accounted as important factors that affect gas turbine performance to produce electricity. An outlook of domestic energy cost is also reviewed. Furthermore, this study has focused on the necessity of maintaining a green and clean environment as well as a climate of lowest dust content. "Reference prices" concept has been clearly comprehended and understood. The contradiction of real opportunities and marginal costs has been explained. An important issue regarding depletion of resources that are depleted exhaustible has been studied. This issue has been tackled and being showed from the starting point. Alternative solutions to provide new energy sources are assumed. [ABSTRACT FROM AUTHOR]

This paper proposed an optimal control technique for power flow control of hybrid renewable energy systems (HRESs) like a combined photovoltaic and wind turbine system with energy storage. The proposed optimal control technique is the joined execution of both the whale optimization algorithm (WOA) and the artificial neural network (ANN). Here, the ANN learning process has been enhanced by utilizing the WOA optimization process with respect to the minimum error objective function and named as WOANN. The proposed WOANN predicts the required control gain parameters of the HRES to maintain the power flow, based on the active and reactive power variation in the load side. To predict the control gain parameters, the proposed technique considers power balance constraints like renewable energy source accessibility, storage element state of charge, and load side power demand. By using the proposed technique, power flow variations between the source side and the load side and the operational cost of HRES in light of weekly and daily prediction grid electricity prices have been minimized. The proposed technique is implemented in the MATLAB/Simulink working stage, and the effectiveness is analyzed via the comparison analysis using the existing techniques. [ABSTRACT FROM AUTHOR]

This paper studies the optimum sizing and techno-economic feasibility of photovoltaic systems for rural healthcare building located in a south Indian State, Tamil Nadu, which experiences tropical weather climate. In this study, fixed tilt, annual optimum tilt (AOT), and six other sun tracking installation types are analyzed using hybrid optimization of multiple energy resource (HOMER) energy to understand the power generation potential. As a first step, weekly and monthly optimum tilt angles and AOT are estimated for the study location. The selection of the optimum configuration is arrived with the lowest values of initial cost, operating cost, total net present cost, and levelized cost of energy. It has been found that AOT with fixed installation is the optimum configuration for the study location. However, the performance would vary when the system is put to operate in practical conditions. In order to understand the varying performance, a prototype model is implemented for horizontal axis sun tracking system. The performance of the prototype is analyzed as per the varying real-time weather conditions for four days typically considering the sandstorm day, cloudy day, clear day, and partially cloudy day. [ABSTRACT FROM AUTHOR]

Load sharing is one of the main concerns in AC microgrids (MGs) which should be treated differently in the presence of photovoltaic (PV) sources. There are two modes of operation for photovoltaic sources, namely, maximum power point tracking (MPPT) mode and DC link voltage control (DCLV) mode. When the total load of MGs is higher than the maximum power of the photovoltaic source, the PV source operates in the MPPT mode, while other sources share the remaining loads; otherwise, it should reduce its power to provide a balance between the generation and load sides by operation in the DCLV mode. Here, a new seamless approach for sharing the load among a photovoltaic (PV) generation system and other sources is proposed based on a conventional droop control method that helps the PV source to locally select its control mode in AC MGs. The proposed method helps the MG to extract as much photovoltaic power as possible while balancing the generations and load sides. The proposed method is simulated in the MATLAB/SIMULINK environment, and the results validate the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]