Energy Yield Improvement Research Articles

Torrefaction of durian peel in air and N2 atmospheres: Impact on chemical properties and optimization of energy yield using multilevel factorial design

This study investigated the torrefaction of durian peel using air and nitrogen as carrier gases. A multilevel factorial design coupled with response surface methodology (RSM) and ANOVA analysis was employed to analyze the impact of torrefaction parameters on chemical properties and energy yield. Durian peel, an agricultural waste product, was torrefied at temperatures ranging from 200 to 320 °C for residence times between 0 and 30 min. Results showed that air torrefaction significantly enhanced thermal decomposition, reducing mass yield from 94.65 % to 30.63 % as the temperature increased from 200 °C to 300 °C with a 30-min holding time. Air torrefaction also increased the higher heating value (HHV) from 19.02 MJ/kg to 35.26 MJ/kg at 300 °C, compared to nitrogen, which achieved a maximum HHV of 32.49 MJ/kg. ANOVA analysis revealed that torrefaction temperature and carrier gas significantly affect energy yield and chemical properties. Air torrefaction positively affected HHV while reducing mass yield compared to nitrogen. Low-temperature air torrefaction showed enhanced energy yield improvement. These findings provided insights for optimizing torrefaction processes enhancing utilization wasted durian peel as a sustainable bioenergy resource.

High Efficiency and Full MPPT Range Partial Power Processing PV Module-Integrated Converter

To increase the energy yield of PV systems in presence of module level power mismatches, Maximum Power Point Tracking (MPPT) should be performed by converters at module level. Using module level converters at the output of the PV panels adds a constant loss even when there is no power mismatch which increases the overall system losses and compromises part of the energy yield improvement. To decrease this constant loss especially when there is no power mismatch, Partial Power Processing (PPP) concept is used in this paper to achieve a new high-frequency and high-efficiency module integrated PV converter, which can achieve full range MPPT and maximum possible efficiency when there is no mismatch. To overcome the challenge of limited MPPT range for partial power converters a special Pulse Density Modulation (PDM) technique is proposed, which preserves the merits of PPP and renders full range MPPT. A 220 W prototype converter is implemented to justify the converter principal of operation and analyses. The proposed converter reached 99.6% to 96.5% efficiency for the power mismatches in the PV module ranging from 0 to 50% of the maximum module power generation capability, respectively. The efficiency drop is shown to be linear with power mismatch level without any abrupt reductions that is commonly observed in conventional PV module integrated converters.

Extendable Voltage Equalizer Topology With Reduced Switch Count and MPPT With Partial Shading Detection Capability for Long Serially Connected PV Modules

Maximum power point tracking (MPPT) plays a significant role in a photovoltaic (PV) system's optimal performance. Bypass diodes create multiple peaks on the power–voltage curve during partial shading conditions (PSCs), reducing the PVs overall power extraction capability. This article proposed a new hybridized architecture for switched inductor and switched capacitor circuit based voltage equalizer (VE) topology with reduced switch count to prevent the multiple peaks and increase the energy yield during PSCs. The proposed VE operates with a fixed duty cycle and frequency. The MPPT controller with PSC detection is also proposed to operate VE only when the PSC is detected to avoid unwanted switching and conduction losses. The proposed system's effectiveness for ten modules connected in series has been determined compared with other modular state-of-the-art VEs. The proposed topology can be extended with a smaller number of control switches. On average, the experimental results showed a 30.42% improvement in energy yield in comparison with the conventional systems. Furthermore, the proposed controller offers the MPPT efficiency of 99.28% with a tracking time of 0.10 s for uniform shaded conditions and 0.692 s for PSCs on average.

Backside light management of 4-terminal bifacial perovskite/silicon tandem PV modules evaluated under realistic conditions.

Perovskite/silicon tandem modules have recently attracted growing interest as a potential candidate for new generations of solar modules. Combined with a bifacial configuration it can lead to considerable energy yield improvement in comparison to conventional monofacial tandem solar modules. Optical modeling is crucial to analyze the optical losses of perovskite/silicon solar modules and achieve efficient light management. In this article we study the optical properties of four-terminal bifacial tandem modules, using metal-halide perovskite top solar cell and a conventional industrial crystalline silicon PERC bottom solar cell. We propose a method to analyze bifacial gains, improve back side light management and challenge it under realistic spectral conditions at several locations with various albedos. We show that both optimized designs for the back side show comparable advantages at all locations. These results are a good sign for the standardization of bifacial four-terminal perovskite/silicon modules.

Computer-based solar tracking system for PV energy yield improvement

<p>Electric energy is the main driver of various daily activities, both to increase productivity as well as to improve life quality. Energy demand is continuously increasing in parallel to the progress in technology and population growth. Depletion of fossil energy sources and awareness of environmental protection make people resort to renewable energy sources like solar energy. Low efficiency and intermittent characteristic of solar energy may originate from the sun movement along the day as well as the year. Efforts have always been tried to deal with the drawbacks. This paper proposes a computer-based tracking system to fully monitor and control a solar panel movement. The designed system has proven a good performance of working at certain time intervals, either hourly, or even continuously, as desired. Energy yield improvement has been achieved by processing the tracking results with the help of a microcontroller to optimize the power generation of the solar panel.</p>

Closed-loop model-based wind farm control using FLORIS under time-varying inflow conditions

Wind farm (WF) controllers adjust the control settings of individual turbines to enhance the total performance of a wind farm. Most WF controllers proposed in the literature assume a time-invariant inflow, whereas important quantities such as the wind direction and speed continuously change over time in reality. Furthermore, properties of the inflow are often assumed known, which is a fundamentally compromising assumption to make. This paper presents a novel, closed-loop WF controller that continuously estimates the inflow and maximizes the energy yield of the farm through yaw-based wake steering. The controller is tested in a high-fidelity simulation of a 6-turbine wind farm. The WF controller is stress-tested by subjecting it to strongly-time-varying inflow conditions over 5000 s of simulation. A time-averaged improvement in energy yield of 1.4% is achieved compared to a baseline, greedy controller. Moreover, the instantaneous energy gain is up to 11% for wake-loss-heavy situations. Note that this is the first closed-loop and model-based WF controller tested for time-varying inflow conditions (i.e., where the mean wind direction and wind speed change over time) at such fidelity. This solidifies the WF controller as the first realistic closed-loop control solution for yaw-based wake steering.

Photovoltaic Energy Yield Improvement in Two-Stage Solar Microinverters

The focus in this paper is on the two-stage photovoltaic (PV) microinverters using a buck-boost dc/dc front-end converter. Wide input voltage range of the front-end converter enables operation under shaded conditions but results in mediocre performance in the typical voltage range. These microinverters can be controlled with either fixed or variable dc-link voltage control methods. The latter improves the converter efficiency considerably in the range of the most probable maximum power point (MPP) locations. However, the buck-boost operation of the front-end converter results in noticeable variations of the efficiency across the input voltage range. As a result, conventional weighted efficiency metrics cannot be used to predict annual energy productions by the microinverters. This paper proposes a new methodology for the estimation of annual energy production based on annual profiles of the solar irradiance and ambient temperature. Using this methodology, quantification of the annual energy production is provided for two geographical locations.

Energy yield of all thin‐film perovskite/CIGS tandem solar modules

AbstractPerovskite/CuIn1 − xGaxSe2 (CIGS) tandem photovoltaics (PV) promises high power conversion efficiencies in combination with the advantages of a light weight and an all thin‐film PV technology. However, the complexity of perovskite/CIGS tandem solar module architectures requires careful optimization of the layer stack under realistic solar irradiation conditions. Here, we provide a systematic numerical study on the energy yield (EY) of perovskite/CIGS tandem solar modules, optimizing the device architecture with regard to irradiance in various climate zones. In particular, variations of the spectral irradiation and the average photon energy are of decisive importance for the location‐specific optimization of the device architecture. Compared with the reference single‐junction CIGS thin‐film PV technology, we demonstrate a strong improvement in EY (>30%) in perovskite/CIGS thin‐film PV for perovskites of a wide range of bandgaps (1.55 ‐ 2.0 eV), reaching up to 52% improvement in EY for the optimal bandgap (around 1.8 eV). Of the two most favored architectures, the two‐terminal and four‐terminal devices, perovskite/CIGS tandem solar modules with low bandgap (∼1.55 eV) perovskite absorbers in the four‐terminal architecture outperform those in the two‐terminal architecture in average by 3.5% relative. However, for wide perovskite bandgaps ranging from 1.75 eV to 1.85 eV, both architectures perform comparably. The improvements in EY for perovskite/CIGS tandem solar modules highlight the potential of this technology but also the vital need for light management in tandem photovoltaics.

Spectrally Selective Mirrors with Combined Optical and Thermal Benefit for Photovoltaic Module Thermal Management

Waste heat generated during daytime operation of a solar module will raise its temperature and reduce cell efficiency. In addition to thermalization and carrier recombination, one major source of excess heat in modules is the parasitic absorption of light with sub-bandgap energy. Parasitic absorption can be prevented if sub-bandgap radiation is reflected away from the module. We report on the design considerations and projected changes to module energy yield for photonic reflectors capable of reflecting a portion of sub-bandgap radiation while maintaining or improving transmission of light with energy greater than the semiconductor bandgap. Using a previously developed, self-consistent opto-electro-thermal finite-element simulation, we calculate the total additional energy generated by a module, including various photonic reflectors, and decompose these benefits into thermal and optical effects. We show that the greatest total energy yield improvement comes from photonic mirrors designed for the outside o...

Off-axis holographic lens spectrum-splitting photovoltaic system for direct and diffuse solar energy conversion.

This paper describes a high-efficiency, spectrum-splitting photovoltaic module that uses an off-axis volume holographic lens to focus and disperse incident solar illumination to a rectangular shaped high-bandgap indium gallium phosphide cell surrounded by strips of silicon cells. The holographic lens design allows efficient collection of both direct and diffuse illumination to maximize energy yield. We modeled the volume diffraction characteristics using rigorous coupled-wave analysis, and simulated system performance using nonsequential ray tracing and PV cell data from the literature. Under AM 1.5 illumination conditions the simulated module obtained a 30.6% conversion efficiency. This efficiency is a 19.7% relative improvement compared to the more efficient cell in the system (silicon). The module was also simulated under a typical meteorological year of direct and diffuse irradiance in Tucson, Arizona, and Seattle, Washington. Compared to a flat panel silicon module, the holographic spectrum splitting module obtained a relative improvement in energy yield of 17.1% in Tucson and 14.0% in Seattle. An experimental proof-of-concept volume holographic lens was also fabricated in dichromated gelatin to verify the main characteristics of the system. The lens obtained an average first-order diffraction efficiency of 85.4% across the aperture at 532 nm.

Bifacial Photovoltaic Systems Energy Yield Modelling

A bifacial photovoltaic model was developed not only to calculate the power and energy yield for bifacial modules for various setup and installation conditions but also to identify suitable bifacial module applications and markets. The bifacial model shows that the energy yield for bifacial modules is very much location dependent and hugely influenced by how they are setup and installed. There is a need to have the modules mounted at a certain elevation above the ground to gain maximum energy yield. It is also important to ensure there is no blockage for the direct sun to shine on the area directly beneath the module. For locations at low latitude, a higher elevation is required. For locations at high latitude, the probability of the direct sunlight reaching the ground directly under the module is higher. Therefore, less module mounting elevation is required. However, there is a saturation point for energy yield improvement with increased module mounting height. In addition to the mounting height, a sufficient length of clearance path in front of the module array should be considered. The model also shows that the ground reflectance is one of the key parameters for bifacial module performance. The model indicates that >10% of energy yield gain with 20% background reflectance from REC bifacial multi-crystalline silicon solar module array with a bifaciality of 0.6 is achievable in Konstanz, Germany. This correlates well with the measured field energy yield data of the bifacial prototype modules.

Practical Limits of Multijunction Solar Cell Performance Enhancement From Radiative Coupling Considering Realistic Spectral Conditions

III-V multijunction solar cells (MJSCs) operate close to the radiative limit under solar concentration. In this regime, radiative losses from the semiconductor material in one junction of the solar cell can be absorbed by a subsequent junction, thereby transferring charge from one subcell to another. Under blue-rich solar spectra, radiative coupling can improve the electrical performance by lifting constraints imposed by a series connection of subcells. We calculate the practical limit of performance enhancement due to the radiative coupling effect for MJSCs under a wide range of atmospheric conditions encountered in potential sites for concentrator photovoltaic systems. Three-junction and four-junction solar cells with current matched and current mismatched designs under the AM1.5D spectrum were considered. Under realistic atmospheric conditions, the relative enhancement to power due to radiative coupling is found to be 1% or less for current-matched triple-junction solar cells. Enhancement of up to 21% can be expected for noncurrent-matched quad-junction devices. The energy yield improvement over an annual period is shown to be up to 5% for the best combinations of devices and sites.

Energy Yield of Tracking PV Systems in Jordan

This paper analyzes the energy yield of photovoltaic (PV) modules mounted on fixed tilt, one-axis, and two-axis tracking system towards maximizing the annual energy production. The performance evaluation of the proposed design of the tracking systems is carried via simulating the global radiation averages using METEONORM software and depicting the simulation results in figures using MATLAB software. The one-axis system is simulated by either fixing the azimuth angle while optimizing the inclination angles or fixing the inclination angle while optimizing the azimuth angles; simulation results show an increase in energy yield of 5.87% and 20.12% compared to that of fixed tilt system, respectively. In the two-axis system, optimization of both azimuth and inclination angles is carried out simultaneously which resulted in 30.82% improvement in energy yield. Therefore, 30% improvement in energy yield is directly reflected as saving in PV system cost due to reduction of the PV modules surface area.