scholarly journals High-Performance Multilayer Radiative Cooling Films Designed with Flexible Hybrid Optimization Strategy

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2885
Author(s):  
Peng You ◽  
Xiong Li ◽  
Yijia Huang ◽  
Xiaoliang Ma ◽  
Mingbo Pu ◽  
...  
Keyword(s):  
Power Density ◽  
High Performance ◽  
Silver Film ◽  
Hybrid Optimization ◽  
Electromagnetic Properties ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Optimization Strategy ◽  
Special Significance ◽  
Traditional Design

Despite their great potential for energy-saving applications, it is still challenging to design passive radiative cooling (RC) materials with simultaneous high performance and simple structures based on traditional design philosophy. To solve the contradiction between optimization speed and corresponding performance, we present a flexible hybrid optimization strategy based on a genetic algorithm (GA) in conjunction with the transfer matrix method and introducing the calculation of radiative cooling power density in the evaluation function of the GA. As a demonstration, an optimized coating with 1.5-μm-overlapping MgF2 and Si3N4 layers on top of a silver film was numerically designed. Based on a detailed analysis of the material’s electromagnetic properties and cooling performance, this coating achieved a radiative cooling power density of 62 W/m2 and a temperature reduction of 6.8 °C at an ambient temperature of 300 K. Our optimization strategy may have special significance in the design of high-performance RC materials or other multi-spectral engineering materials with simple structures.

scholarly journals Biologically inspired flexible photonic films for efficient passive radiative cooling

2020 ◽  
Vol 117 (26) ◽  
pp. 14657-14666 ◽  
Author(s):  
Haiwen Zhang ◽  
Kally C. S. Ly ◽  
Xianghui Liu ◽  
Zhihan Chen ◽  
Max Yan ◽  
...  
Keyword(s):  
High Throughput ◽  
High Performance ◽  
Low Cost ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Fundamental Parameter ◽  
Photonic Materials ◽  
Biologically Inspired ◽  
Thermoregulatory Function ◽  
Wearable Products

Temperature is a fundamental parameter for all forms of lives. Natural evolution has resulted in organisms which have excellent thermoregulation capabilities in extreme climates. Bioinspired materials that mimic biological solution for thermoregulation have proven promising for passive radiative cooling. However, scalable production of artificial photonic radiators with complex structures, outstanding properties, high throughput, and low cost is still challenging. Herein, we design and demonstrate biologically inspired photonic materials for passive radiative cooling, after discovery of longicorn beetles’ excellent thermoregulatory function with their dual-scale fluffs. The natural fluffs exhibit a finely structured triangular cross-section with two thermoregulatory effects which effectively reflects sunlight and emits thermal radiation, thereby decreasing the beetles’ body temperature. Inspired by the finding, a photonic film consisting of a micropyramid-arrayed polymer matrix with random ceramic particles is fabricated with high throughput. The film reflects ∼95% of solar irradiance and exhibits an infrared emissivity >0.96. The effective cooling power is found to be ∼90.8 W⋅m−2and a temperature decrease of up to 5.1 °C is recorded under direct sunlight. Additionally, the film exhibits hydrophobicity, superior flexibility, and strong mechanical strength, which is promising for thermal management in various electronic devices and wearable products. Our work paves the way for designing and fabrication of high-performance thermal regulation materials.

A double-sided radiative cooling architecture with a record local cooling power density of 270 W/m2

2021 ◽  
Author(s):  
Lyu Zhou ◽  
Haomin Song ◽  
Nan Zhang ◽  
Jacob Rada ◽  
Matthew Signer ◽  
...  
Keyword(s):  
Power Density ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Local Cooling

scholarly journals High-performance subambient radiative cooling enabled by optically selective and thermally insulating polyethylene aerogel

2019 ◽  
Vol 5 (10) ◽  
pp. eaat9480 ◽  
Author(s):  
A. Leroy ◽  
B. Bhatia ◽  
C. C. Kelsall ◽  
A. Castillejo-Cuberos ◽  
M. Di Capua H. ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Air Conditioning ◽  
High Performance ◽  
Recent Progress ◽  
Passive Cooling ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Direct Sunlight ◽  
Solar Absorption ◽  
Solar Noon

Recent progress in passive radiative cooling technologies has substantially improved cooling performance under direct sunlight. Yet, experimental demonstrations of daytime radiative cooling still severely underperform in comparison with the theoretical potential due to considerable solar absorption and poor thermal insulation at the emitter. In this work, we developed polyethylene aerogel (PEA)—a solar-reflecting (92.2% solar weighted reflectance at 6 mm thick), infrared-transparent (79.9% transmittance between 8 and 13 μm at 6 mm thick), and low-thermal-conductivity (kPEA = 28 mW/mK) material that can be integrated with existing emitters to address these challenges. Using an experimental setup that includes the custom-fabricated PEA, we demonstrate a daytime ambient temperature cooling power of 96 W/m2 and passive cooling up to 13°C below ambient temperature around solar noon. This work could greatly improve the performance of existing passive radiative coolers for air conditioning and portable refrigeration applications.

scholarly journals Sub-Ambient Radiative Cooling Realized Using CaCO3 Microparticle-Based Single Layer Without Metal Reflector for Entire Day

2021 ◽  
Author(s):  
Hangyu Lim ◽  
Dongwoo Chae ◽  
Soomin Son ◽  
Sucheol Ju ◽  
Jisung Ha ◽  
...  
Keyword(s):  
Environmental Pollution ◽  
High Performance ◽  
Single Layer ◽  
High Energy ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Light Pollution ◽  
Cooling Systems ◽  
Air Conditioners ◽  
Conventional Cooling

Abstract Conventional cooling systems, that is, air conditioners, should be replaced because they consume a substantial amount of energy and cause environmental pollution. In this context, radiative cooling systems, which perform cooling without consuming any energy or causing environmental pollution, are emerging as an alternative. However, most of the radiative coolers explored thus far include metals, such as silver, that are used as solar reflectors, thereby entailing problems in terms of practicality, mass production, cost, and light pollution. Herein, we propose calcium carbonate (CaCO3) micro-particle-based radiative cooling, which utilizes the high-energy band gap of CaCO3 for high-performance radiative cooling. As the cooler has only a single layer of a CaCO3 composite without any metal reflector, it is mass-producible, cheap, and does not cause light pollution. To demonstrate the cooling performance of CaCO3, optical properties and temperature changes are measured and compared with those of commercial white paint. As a result, it is demonstrated that the CaCO3-based radiative cooler has cooling power 93.1 W/m2 in calculation and can be cooled 6.52 ℃ and 3.38 ℃ under ambient temperature in daytime and nighttime respectively. Thus, it can perform as radiative cooler in entire day.

Hybrid optimization strategy beyond local optima in aerospace panel designs

AIAA Journal ◽  
1999 ◽  
Vol 37 ◽  
pp. 588-593
Author(s):  
K. L. Chan ◽  
David Kennedy ◽  
Fred W. Williams
Keyword(s):  
Hybrid Optimization ◽  
Optimization Strategy ◽  
Local Optima

scholarly journals An Efficient Hybrid Optimization Strategy for Surface Reconstruction

2021 ◽  
Author(s):  
Giulia Bertolino ◽  
Marco Montemurro ◽  
Nicolas Perry ◽  
Franck Pourroy
Keyword(s):  
Surface Reconstruction ◽  
Hybrid Optimization ◽  
Optimization Strategy

scholarly journals Reliability-Oriented Design of Inverter-Fed Low-Voltage Electrical Machines: Potential Solutions

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4144
Author(s):  
Yatai Ji ◽  
Paolo Giangrande ◽  
Vincenzo Madonna ◽  
Weiduo Zhao ◽  
Michael Galea
Keyword(s):  
Power Density ◽  
High Speed ◽  
High Performance ◽  
Low Voltage ◽  
Electrical Machines ◽  
Design Stage ◽  
Switching Frequency ◽  
Special Focus ◽  
Electrical Machine ◽  
Engineering Approach

Transportation electrification has kept pushing low-voltage inverter-fed electrical machines to reach a higher power density while guaranteeing appropriate reliability levels. Methods commonly adopted to boost power density (i.e., higher current density, faster switching frequency for high speed, and higher DC link voltage) will unavoidably increase the stress to the insulation system which leads to a decrease in reliability. Thus, a trade-off is required between power density and reliability during the machine design. Currently, it is a challenging task to evaluate reliability during the design stage and the over-engineering approach is applied. To solve this problem, physics of failure (POF) is introduced and its feasibility for electrical machine (EM) design is discussed through reviewing past work on insulation investigation. Then the special focus is given to partial discharge (PD) whose occurrence means the end-of-life of low-voltage EMs. The PD-free design methodology based on understanding the physics of PD is presented to substitute the over-engineering approach. Finally, a comprehensive reliability-oriented design (ROD) approach adopting POF and PD-free design strategy is given as a potential solution for reliable and high-performance inverter-fed low-voltage EM design.

scholarly journals Electromagnetic-Thermal Integration Design of Permanent Magnet Motor for Vehicles

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Shijun Chen ◽  
Qi Zhang ◽  
Surong Huang
Keyword(s):  
Permanent Magnet ◽  
High Performance ◽  
Design Method ◽  
Electromagnetic Properties ◽  
Permanent Magnet Motor ◽  
Element Analysis ◽  
Experiment Platform ◽  
Motor Design ◽  
Dimensional Parameters ◽  
Thermal Integration

To more efficiently design high performance vehicular permanent magnet motor, an electromagnetic-thermal integration design method is presented, which considers both the electromagnetic properties and the temperature rise of motor winding when determining the main dimensional parameters of the motor. Then a 48-slot and 8-pole vehicular permanent magnet motor is designed with this method. The thermomagnetic coupling design is simulated and validated on the basis of multiphysical domain on finite element analysis. Then the prototype is analyzed and tested on a newly built motor experiment platform. It is shown that the simulation results and experimental results are consistent, which validate the accuracy and effectiveness of the new design method. Also this method is proved to well improve the efficiency of permanent magnet motor design.

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