Decrease In Power Output Research Articles

Energy and exergy analyses of a recompression supercritical CO2 cycle combined with a double-effect parallel absorption refrigeration cycle

In this study, a new cogeneration system is presented that can make optimal use of the waste heat from the sCO2 power cycle using a double-effect parallel absorption refrigeration cycle (DEARC), generating electricity and refrigeration simultaneously. A comparative study between the proposed (sCO2/DEARC) system and the stand-alone sCO2 power system is conducted to show its advantages and potential. The performances of the sCO2 and sCO2/DEARC systems are evaluated from the energetic and exergetic points of view using an in-house developed thermodynamic simulation platform via Engineering Equation Solver (EES) software. Variables such as pressure ratio, turbine inlet temperature, and evaporator temperature are also used for parametric analysis. The results indicate that the proposed system can generate of 132.72 MW cooling capacity. Also, the results show that the proposed sCO2/DEARC system can achieve a 55.8% and 5.2% improvement in thermal efficiency and exergy efficiency, respectively, with a negligible decrease in net power output (Wnet) compared to the stand-alone sCO2 power plant.

Influences of nonlinear parameters on the performance of a free‐piston Stirling engine

AbstractThis study presents a thermodynamic–dynamic model of a free‐piston Stirling engine (FPSE) with nonlinear coefficients of spring, load damping, and pressure for working spaces. The effects of the nonlinear coefficients of hardening and softening springs on the movement and operating frequency of a displacer and piston are investigated. Subsequently, the influences of the nonlinear pressure terms of the working space and buffer spaces, as well as the nonlinear coefficients of the load on the amplitudes of the two pistons, frequency, and output powers are discussed. The results indicate that the low nonlinear coefficients of the spring have a minor effect on the amplitudes and frequency. As the high nonlinear coefficients of the hardening spring increase, the amplitudes and output power decrease, while the frequency increases. As the nonlinear terms of the softening spring increase, the amplitudes and output power reach maximum values, but the frequency is reduced by 3.55%. The effects of the nonlinear pressure terms on the amplitudes and output power are not evident. However, an increase in the nonlinear load leads to a significant decrease in the FPSE's performance.

Effect of different ammonia mixing methods for diesel ignition on combustion and emission performance of high pressure common rail engine

Ammonia is a zero-carbon fuel. Diesel/ammonia dual-fuel combustion mode can solve the problem of difficult compression ignition of pure ammonia. This article aims to explore the best mixing method and mixing ratio of ammonia fuel. The research results show that with the increase of the ammonia mixing ratio in the intake duct, the fuel consumption rate decreases by 7.71%. However, the serious ammonia escape phenomenon reaches a maximum of 37.35%, resulting in a serious decrease in power output. The cylinder temperature dropped by 197.12K, CO2 emissions decreased by 49.34%, NOx emissions decreased by 16.84%, and emissions significantly improved. When using direct injection ammonia mixing in the cylinder, as the ammonia mixing ratio increases, the explosion pressure in the cylinder decreases by 8.32%, the temperature in the cylinder decreases by 127.37K, the maximum ammonia escape is only 6.89%, CO2 emissions decreased by 88.10%, NOx emissions decrease by 75.90%, and CO2 and NOx emissions significantly decrease. Compared with the two ammonia blending methods, the direct injection ammonia blending method in the cylinder is obviously better. When the direct injection ammonia blending ratio in the cylinder is 70%, compared to the original engine, the diesel engine has the best working performance, increased power, and improved economy by 7.52%, and the proportion of ammonia escape is small. CO2 emissions are reduced by 69.05%, and NOx emissions are reduced by 29.22%. The research results of this article provide data support for achieving energy-saving, emission reduction, and low-carbon environmental protection of diesel engines.

Macroscopic Zeno Effect in a Su–Schrieffer–Heeger Photonic Topological Insulator

AbstractThe quantum Zeno effect refers to the slowdown of the decay of a quantum system due to frequent measurements. It has been extended beyond quantum systems, manifesting itself in such phenomena as the suppression of output beam decay by sufficiently strong absorption introduced in guiding optical systems. In this case, the phenomenon is termed as macroscopic Zeno effect. Here the observation of the macroscopic Zeno effect in a topological photonic system is reported. The phenomenon is based on the suppression of decay for only a subspace of edge modes that can propagate in the system and does not rely on the existence of exceptional points. By introducing controlled losses in one of the arms of a topological insulator comprising two closely positioned Su–Schrieffer–Heeger arrays, the macroscopic Zeno effect is demonstrated, which manifests itself in an increase of the transparency of the system with respect to the topological modes created at the interface between two arrays. The phenomenon remains robust against disorder in the non‐Hermitian topological regime. In contrast, coupling a topological array with a non‐topological one results in a monotonic decrease in output power with increasing absorption.

Research on dust deposition of PV modules based on three-dimensional numerical simulation and its application in installation parameter optimization

Dust deposition on the surface of photovoltaic (PV) modules leads to a decrease in photoelectric conversion efficiency and output power. To identify the dust deposition factors and laws, scholars have conducted numerous field experiments or numerical simulations. However, few scholars have studied the mechanism of dust deposition with three-dimensional (3D) simulation models. The parameters affecting dust deposition vary in different geographical regions, which limits the applicability of research findings on dust deposition to specific geographical areas. To address these issues, this paper first proposes dust adsorption conditions on the surface of PV modules. Based on the main dust deposition factors, a 3D simulation model for dust deposition is established, and the accuracy and effectiveness of the adsorption conditions and simulation model are verified. Then, with a combined approach of orthogonal experiments and 3D simulation analysis, the main dust deposition factors and laws are analyzed. Finally, regional clustering is conducted by dust deposition factors, and the simulation results are applied to the regional optimization of installation parameters. The case study results show that the PV modules have a maximum power generation of 231.91 kWh with an optimal installation angle of 17° and an installation height of 0.5 m in the I category region.

Impact of Cardiac Power Output on Exercise Capacity and Clinical Outcome in Patients With Chronic Heart Failure

Less data are available regarding the impact of cardiac power output on exercise capacity or clinical outcome in patients with chronic heart failure (CHF). The study enrolled 280 consecutive patients with CHF referred for cardiopulmonary exercise testing and right-sided heart catheterization between 2013 and 2018. The primary outcome was composite of heart failure hospitalization or death. Cardiac power output was calculated as (mean arterial pressure×CO) ÷ 451. Patients with low cardiac power output (<0.53W, n=99) were older and had a higher brain natriuretic peptide level than patients with high cardiac power output (≥0.53W, n=181). Cardiac power output was correlated with peak oxygen consumption (peak V̇O2), peak workload achievement, and ventilatory efficiency (V̇E/V̇CO2 slope) in cardiopulmonary exercise testing, whereas each of cardiac output or mean arterial pressure was not. There were 48 patients with events over a median follow-up period of 3.5 (interquartile range 1.0 to 6.0) years. Patients with low cardiac power output had about a 2-fold higher risk of events than those with a high cardiac power output (hazard ratio 1.97, 95% confidence interval 1.12 to 3.48). In the multivariable Cox regression, a 0.1-W decrease in cardiac power output was associated with 19% increased adverse events (hazard ratio 0.81, 95% confidence interval 0.67 to 0.99). In conclusion, cardiac power output was associated with reduced exercise capacity and poor clinical outcome, suggesting that cardiac power output is useful for risk stratification in patients with CHF. Further study is required to identify therapies targeting cardiac power output to improve the exercise capacity or clinical outcome in patients with CHF.

Investigation of weather conditions on the output power of various photovoltaic systems

The quantity of solar radiation received by photovoltaic panel surfaces and their efficiency are influenced by environmental factors, including dust buildup and weather changes. This study presents an experimental analysis to determine how dust and rain affected the output of photovoltaic power for five different types and orientations of solar module systems of 5 kW each. All systems are installed at Applied Science Private University in Jordan, and attached to sunny portal system to monitor the PV output power for each type in real time. After one–four weeks of exposure, the effects of dust buildup and weather conditions on the power output of the module systems were examined. The results showed that four weeks of dust buildup resulted in 16.7%, 28%, 16.6%, 26.7%, and 21% reduction in PV power production for Monocrystalline (c-Si)/South, Monocrystalline (c-Si) East/West, Polycrystalline (p-Si)/South, Polycrystalline (p-Si)/East/West, and Thin-film (a-Si, microcrystalline)/South system respectively. In addition, a 20% average decrease and fluctuation in PV output power under wet conditions is observed. Moreover, the results showed that the power sold to the grid would be lower than predicted by 21% after one month of dust accumulation, which should be included in energy management planning.

A Hybrid Particle Swarm Optimization with Butterfly Optimization Algorithm Based Maximum Power Point Tracking for Photovoltaic Array under Partial Shading Conditions

The key objective of this paper is to develop a photovoltaic (PV) maximum power point tracking (MPPT) algorithm based on particle swarm optimization–butterfly optimization algorithm (PSO-BOA) that is adapted for partial shading conditions (PSCs). Generally, conventional MPPT techniques are often unable to accurately locate the global maximum power point (GMPP) generated by partial shading in PV systems. As a result, a significant decrease in power output occurs. The traditional particle swarm optimization (PSO) algorithm traps the local maxima point easily, while the butterfly optimization algorithm (BOA) has slow convergence speed and large oscillations during its use in research. To address the limitations of the aforementioned PSO and BOA algorithms, the MPPT strategy of PV systems combining PSO-BOA is presented, which can ameliorate the efficiency and accuracy in PSCs. In this paper, the control parameter of sensory modality in the BOA can be acquired based on logistic mapping, and the self-adaptive adjustment of the inertial weight of the PSO algorithm is designed. According to the simulation findings, the suggested method is more suitable than PSO and BOA with respect to intricate shading-induced variations in irradiance and changes in external temperatures. The average tracking time is less than 0.5 s, and the tracking accuracy is not less than 99.94%. Especially under sudden variations in irradiance and temperature conditions, the tracking time of the PSO-BOA algorithm is only 49.70% of that of the PSO algorithm and 55.63% of that of the BOA. Therefore, the MPPT method presented has the ability to improve the oscillations and result in less convergence speed, which in turn accurately tracks the GMPP.

Performance Emission and Combustion Characteristics of Ethanol Hydrogen Blends at MBT Spark Timing on Multi-cylinder SI Engine

Alternative fuels are the need of the current situation as conventional fuels are depleting very quickly and causing increase in amounts of pollution. Hydrogen as a clean fuel with Higher Calorific Value plays important role in increasing combustion characteristics. When compared with the performance of ethanol as a fuel, ethanolhydrogen blends have demonstrated a 5% increase in power production, 15% reduction in hydrocarbon emissions, and 12% reduction in carbon dioxide emissions. All tests are conducted at speed of 2500, 3000, 3500, 4000, and 4500 rpm with the Wide-Open-Throttle (WOT) condition. CO &amp; HC emissions are reduced using ethanol, whereas hydrogen addition enhanced the decreased power output, higher brake-specific fuel consumption and in cylinder pressure.&#x0D; Keywords: Emission, combustion, ethanol, hydrogen, SI engine, alternate fuels, conventional fuels, renewable energy sources, MBT spark timing, NOx emissions, nitrogen, Maximum Brake Torque

Power Efficiency Analysis based on Lightning Effect on Large-Scale Solar Photovoltaic System

Currently, a large-scale solar photovoltaic (LSSPV) has become one of the fastest developments of electrical generation power for Malaysian Renewable Energy. However, lightning strikes are common in Malaysia due to its geographical position and tropical climate, especially in the open space of large-scale site power plants. This paper discussed the scientific basis and key assumptions that should be included in the layout of a lightning protection scheme in a large-scale solar photovoltaic installation. The framework proposal aims to ensure compliance with standards and guidelines, mitigating the risk of significantly induced currents in the LSSPV power plant. A 2.5 MW solar PV farm system was modelled using MATLAB software for assessing a solar PV farm’s electrical performance under various lightning current waveforms and lightning magnitude currents. These lightning strikes will impact photovoltaic modules, thus deteriorating the system’s ratio generation. The effects of lightning current on LSSPV were accessed based on simulation work in MATLAB Simulink. The induced current protection scheme covered rating selection and collecting data on lightning that may hit the modules or arrays. This data was then analysed according to the standard guidelines to ascertain the most effective protection measures for the 50MW PV farm within the LSSPV system. Minimising the maintenance and replacement cost of equipment is possible. The performance of a 2.5MW solar PV power plant with a grid connection was evaluated. A maximum and minimum power output of 2.47MW and 522.50kW, respectively, were observed. However, when the lightning impulsive current is included through the system, the power output decrease to 407.33kW due to the high magnitude induced.

Effects of high-dose 80 MeV proton irradiation on the electroluminescent and electrical performance of InGaN light-emitting diodes

The paper reports on the degradation of InGaN/GaN Blue LED submitted to proton irradiation at 80 MeV and various fluences (4×1013 p cm−2 and 1×1014 p cm−2). After irradiation, we found a decrease in light output power and the external quantum efficiency with fluence. Photoluminescence (PL) measurements exhibited that the peak position at 400, 447 and 568 nm remained unchanged, only the peak intensity decreased. The intensity of the blue emission reduced by 75%, indicating that the active region degraded seriously; the intensity from In x Ga1-x N (x = 0.11) reduced more than two times in comparison with the blue emission, implying that proton irradiation affected In x Ga1-x N more seriously than InGaN/GaN MQWs. The degradation of LED is ascribed to the increase in the defect-related Shockley–Read–Hall recombination after 80 MeV proton irradiation with higher fluence.

Short Wavelength Photons Destroying Si–H Bonds and Its Influence on High‐Efficiency Silicon Solar Cells and Modules

Photons of varying wavelengths exert substantial effects on silicon heterojunction (SHJ) solar cells. Collaborative research previously establishes that light soaking with long‐wavelength photons can activate boron doping in hydrogenated amorphous silicon (a‐Si:H), thereby augmenting cell efficiency (Eff). Herein, this investigation is extended, exploring the effects of short‐wavelength photons on a‐Si:H layers, SHJ solar cells, and modules. The ultraviolet A (UVA) light with the wavelengths peak of 365 nm can disrupt Si–H bonds, resulting in a notable reduction in hydrogen content within both intrinsic and doped a‐Si:H films, and the deterioration of deteriorated interface passivation. Following exposure to 60 kWh m−2 of UVA light, both Eff and module power output decrease significantly, primarily attributable to the degradation of open‐circuit voltage and fill factor. As a feasible solution, the application of a light‐soaking process or the implementation of UV band cutoff module encapsulants can effectively mitigate the loss induced by UV irradiation, thereby ensuring the long‐term operation of SHJ solar cells and modules. Herein, a deeper understanding of UV‐induced performance changes in a‐Si:H film and its degradation mechanism for SHJ solar cells are contributed to in this research and also a viable strategy is provided to counter UV‐induced degradation.

Design and Performance Analysis of a Novel Integrated Solar Combined Cycle (ISCC) with a Supercritical CO2 Bottom Cycle

The integrated solar combined cycle (ISCC) system is a proven solution for grid-connected power generation from solar energy. How to further improve the ISCC system efficiency and propose a more efficient system solution has become a research focus. A novel gas turbine combined cycle (GTCC) benchmark system is proposed by replacing the conventional steam Rankine bottom cycle with a supercritical CO2 Brayton cycle, whose output power and efficiency are increased by 9.07 MW and 1.3%, respectively, compared to those of the conventional GTCC system. Furthermore, the novel ISCC systems are established with the parabolic trough solar collector (PTC) and the solar tower (ST) collector coupled to the novel GTCC system. Thermal performance analysis, exergy performance analysis, and the sensitivity analysis of the ISCC systems have been performed, and the results show that the system efficiencies of both ISCC systems are lower than that of the GTCC system, at 57.1% and 57.5%, respectively, but the power generation of the ISCC system with PTC is greater than that of the benchmark system, while that of the ISCC system with ST is less than that of the benchmark system. The photoelectric efficiency of the ISCC system with PTC is 27.6%, which is 2.1% greater than that of ISCC system with ST. In the ISCC system with PTC, the components with the highest exergy destruction and the lowest exergy efficiency are the combustion chamber, and PTC, respectively. ST is the component with the highest exergy destruction and the lowest exergy efficiency in the ISCC system with ST. With the increase in direct normal irradiance (DNI), the total output power, solar energy output power, and photoelectric efficiency of the ISCC system with PTC increase, while the system efficiency decreases; the solar energy output power and photoelectric efficiency of the ISCC system with ST increase, while the total output power and system efficiency decrease. The photoelectric efficiency of the ISCC system with PTC is greater when the DNI is greater than 600 W/m2; conversely, the photoelectric efficiency of the ISCC system with ST is greater. After sensitivity analysis, the optimal intercooler pressure for the ISCC system is 11.3 MPa.

Development of a cooling and power generation prototype integrating an axial micro-turbine in an absorption chiller

The integration of an expander in an absorption machine allows it to produce cooling and electricity simultaneously within the same cycle. This technology holds great potential to harness low-temperature heat sources more efficiently than production with separate cycles. However, very few experimental studies on absorption combined cooling and power production cycles can be found in literature. In order to achieve an in-depth understanding of this technology and of the interactions between power and cooling production sides of the circuit, the integration of an expander into a single stage ammonia water absorption chiller was undertaken through the development of an experimental pilot plant. The peculiar characteristics of the expansion device, as well as the use of a newly developed combined desorber avoiding the presence of a rectifier make the prototype built unique. Design and integration of the expander proved to be very challenging, mainly due to the small size of the application and corrosiveness of the ammonia water mixture. Significant electricity generation losses experienced lead to maximum electrical efficiency of 7% and corresponding maximum power production around 33 W at a lower than expected rotational speed of 20′000 rpm.Despite these difficulties, first experimental measurements have been obtained, giving interesting insights on the functioning of the cycle. Indeed, the impracticability of regulating the ratio between cooling and power production was highlighted, due to the characteristics of the impulse turbine. Opening of the turbine line in the nominal point leads to a reduction of the mass flow rate passing through the cooling line of 65% (i.e., split ratio of 0.35) and a cooling power output decrease of around 57% (from 4.9 to 2.1 kW). Additionally, diverting some of the desorbed vapour to the power production line has important effects on the pressure equilibrium and circulating vapour mass flow rate, increasing from 16.1 kg/h in the simple absorption working mode to 31.1 kg/h in the combined mode in the nominal operating point. Feedback from the pilot plant will be very useful for the further development of the technology.

Analisis Pengaruh Suhu Dan Partial Shading Terhadap Output Daya PV 100-WP Untuk Sistem Hidroponik

This experiment discusses the effect of the variability of solar radiation due to partial shading and surface temperature of the PV Panel on the output power of 100 Wp solar panels. This study begins by determining the load of the system, i.e. DC pump in the nutrient circulation system of the DFT hydroponic system. From there, we can observe the change in solar panel power output and PV surface temperature change due to partial shade. This survey method actually measures the temperature and intensity of solar radiation and measures the power output of a solar panel, and the tools used are thermal sensors used to measure the surface temperature of solar panels. Solar power meter. to measure the solar irradiance and use the multimeter to measure the voltage and current, 10A capacity SCC battery, 100Wp capacity solar panel and 65Ah battery. The test will be conducted for 5 days, starting from 09:00 to 15:00 every day. This result shows that temperature increase affects the output power decrease when the solar panel is in normal condition (not half shaded condition). On the other hand, when partial shade conditions increase, the temperature does not affect the decrease in solar panel output power. The greater the intensity of partial shade produced by the solar panel, the lower the output power. However, for short periods of partial shade, the output power produced tends to be more stable than under normal conditions.

Design of a Highly Compatible Underwater Wireless Power Transfer Station for Seafloor Observation Equipment

Conventional cabled seafloor observatories (CSOs) power in-situ instruments via wet-mated or dry-mated direct electrical contact (DEC) connectors to achieve long-term and real-time observation. However, the DEC connectors have high risks of water leakage and short circuits in power feeding, especially under high water pressure. This paper proposes a highly compatible underwater station based on inductive wireless power transfer (IPT) technology to address the above reliability issue. A novel energy transmitter with runway-structure coils is applied to the proposed underwater station to cover a sufficient power feeding area so that various in-situ equipment can be powered with desirable misalignment tolerance. The magnetic field distribution is analyzed by both derivation and finite element analysis (FEA) methods, and the principal parameters of the transmitter are further optimized and compared with both the mixed-integer sequential quadratic programming (MISQP) algorithm and the evolutionary algorithm (EA) for better performance. The same results show a reliable optimization process. The WPT circuit characteristics are also investigated to power different loads and improve the power transmission efficiency. The output power decreases, and the transmission efficiency rises and then decreases as the load increases. In addition, receivers with higher mutual inductance have better transmission performance. A prototype of the underwater station has been tested both in air and in water, and the experimental results have proven it can power multiple seafloor observation instruments stably and achieve compatibility requirements. The maximum output power of the station prototype for testing is 100 W, and the maximum overall transmission efficiency is 61%.

Tolerance to hygrothermal and high-voltage stresses for Si-related photovoltaic modules with newly-developed polyvinyl butyral encapsulants

Newly-developed polyvinyl butyral (PVB) encapsulants were employed for Si-related photovoltaic modules. Modules of amorphous Si with a glass–glass structure and those of crystalline Si with glass and a back-sheet structure were subjected to hygrothermal stresses by a damp-heat (DH) test and high-voltage stress by a potential-induced degradation (PID) test, respectively. Even after a quite long DH test at 85 °C and 85% relative humidity for 49 000 h, retention of output power of about 85% was obtained without edge sealant. No decrease in output power was also observed after a PID test with −1000 V at 60 °C and 85% relative humidity for 168 h. These facts suggest that newly-developed PVB is well applicable to encapsulant materials for highly reliable photovoltaic modules.

Performance improvement of a pump running as turbine for energy recovery considering the effects of polymer additives: An experimental study

Employing pumps as turbines (PAT) has proven to be a cost-effective and efficient method for producing clean electricity in various engineering applications. PATs are now being considered for use in pumped hydro storage plants (PHS) instead of using a series of separate pumps and turbines and also in oil, petrochemical, and refinery industries as pressure energy recovery. Therefore, it is highly desirable to improve the hydraulic and mechanical characteristics of PATs in such applications. In this study, the effects of polymer additives as drag reducing agents on the performance of a centrifugal pump running as turbine mode is experimentally investigated. Reducing the friction drag within a turbulent flow using additives such as long-chain flexible polymers has attracted considerable attention from an energy-saving perspective. For this purpose, a test rig including the feed pump and the main pump has been set up where aqueous solutions of polyacrylamide with concentrations of 150, 300, and 450 ppm are used as working fluid. In order to compare the turbine mode with the pump mode, the pump performance in direct operation is also evaluated. The findings reveal that compared to tap water, using polymer solutions increases the efficiency and output power of the PAT, which even further improves with increasing polymer concentration. In the turbine mode, the highest increase in efficiency occurred at 450 ppm, which represented an increase of 7.61%. On the other hand, in the pump mode, the maximum improvement in pump efficiency (8.30%) has been recorded when the 150 ppm solution is used instead of tap water. By increasing the flow rate of polymeric solutions, the percentage of increase in the pump’s efficiency, compared to tap water, is ascending. Conversely, the percentage of increase in the PAT’s efficiency declines as the flow rate of polymeric working fluid passing the turbine is increased. The degradation of the utilized polymer in solutions leads to a decrease in output power and efficiency of the PAT compared to its fresh state. Nevertheless, the PAT efficiency and generated power in the degraded condition of the solution are still higher than what can be achieved in presence of tap water as the working fluid. The results of this study generally show that the use of working fluids with viscoelastic properties, which contain additive polymers, significantly improves the performance of reverse and direct pumps. As such, it can be used as an alternative working fluid in the industries mentioned above.

Impact of focusing and polarization inhomogeneity on SHG in type-II ppKTP

We study the effects of pump beam focusing and polarization inhomogeneity on second-harmonic generation (SHG) in a 3 cm long type-II ppKTP crystal. Focusing leads to an asymmetry in the SHG output power around the phase-matching temperature (PMT), along with a shift of the PMT to a lower temperature. Theoretical predictions are experimentally verified for different focusing parameters at various pump wavelengths, showing maximum SHG of W−1 (close to optimal focusing). Further, an inhomogeneous polarization across the pump beam cross-section is theoretically predicted to break up the SHG transverse (intensity) profile into several lobes, resulting in an overall decrease in the total output power. We experimentally show that a radially/azimuthally polarized pump beam (generated via a Q-plate) results in a four-lobed SHG similar to the Hermite–Gaussian HG 11 mode with an optimal focusing parameter that is four times higher than that for the homogeneously polarized pump.

Fast Neutron Irradiation on GaN-Based Light-Emitting Diodes From Near-Ultraviolet to Green Spectral Ranges

Neutron irradiation effects were compared for GaN-based multi-quantum well (MQW) light emitting diodes (LEDs) with emission wavelength in the near-ultraviolet (NUV), blue and green spectral regions. Optical output power, current-voltage and peak wavelength were analyzed in detail before and after irradiation. Three colors of LEDs showed an increase and then a decrease in optical output power with the increase of neutron fluence ranging from 1.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> to 1.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . The enhanced light emission performance is attributed to the increase of carrier injection for neutron irradiated MQWs. In addition, the formation of tunneling conductivity channels in the p-doped AlGaN electron block layer (EBL) induced by neutrons is considered as the main factor that dominates the performance degradation. Among the three colors of LEDs, the order of severity for the optical and electrical properties influenced by this medium-fluence neutron irradiation is green, blue, and NUV LEDs, in turn becoming more serious. The NUV LEDs rely heavily on the EBL due to their poor carrier confinement in relatively shallow GaN/AlGaN MQWs, so an increase of carrier injection or leakage induced by neutrons has significant influence on device performance. As the green LEDs have deep quantum wells, the strong confinement of carriers leads to their being least sensitive to neutron irradiation. So we believe that design of LEDs with deep quantum wells to enhance the carrier confinement ability will be helpful to improve their radiation tolerance. The findings not only enrich the understanding of the influence mechanism of neutron irradiated GaN-based UV/visible LEDs, but are also helpful to radiation hardened design.