不间断制冷技术在数据中心工程中的应用

介绍数据中心不间断制冷的必要性、数据中心Tier级别与不间断制冷的关系、不间断制冷的做法、水蓄冷技术在数据中心不间断制冷应用的可行性;为数据中心不间断制冷和蓄冷装置的设计提供了依据和思路。     

太阳能制冷空调研究现状及比较

介绍吸收式、吸附式和喷射式太阳能制冷技术的原理,对其优缺点进行了分析比较.分析了太阳能制冷空调技术在工程应用中的常见问题.最后得出太阳能制冷技术的适用条件和相应的改进措施及应用前景.     

半导体制冷技术及应用

<正> 半导体制冷又称温差制冷或热电制冷,这项技术自20世纪50年代末发展起来后,因其具有独特的优点而得到了较广泛的应用。在发达国家,它已用于汽车(或手提式)冰箱、白内障冷冻摘除器、核潜艇空调器、红外制导空对空导弹的红外探测器探头冷却器、照相显影液恒温冷却器、宇航员及坦克乘员的空调服等方面。我国在20世纪60年代开始对半导体制冷进行了研究,并生产出性能良好的半导体制冷材料。随着我国经济的高速发展,许多领域有待于用半导体制冷技术去进一步开拓。本文介绍半导体制冷技术的原理、特点及主要应用。     

冰片滑落式冰蓄冷系统基于周蓄冰策略下的优化运行

蓄冷空调系统,有效的控制方式是保证节省运行费用和节约能源的关键,采用冰片滑落式动态蓄冷系统与基于周蓄冰策略优化控制运行相结合的运行模式,保证制冷主机高效运行加变释冷率融冰供冷来满足联合供冷时空调负荷要求,由此制冷主机运行效率可避免受外界负荷变化影响而降低,始终在高效区域运行,从而能够实现蓄冷系统节省运行费用、降低运行能耗、制冷主机高效运行的目标。     

新型太阳能温差发电装置的研究

介绍了一种综合利用温差发电原理,相变储能原理的新型太阳能温差发电装置的组成及工作原理,并且结合金属氢化物特点,配套设计了新型太阳能制冷循环系统;对能精确测量硬脂酸转变温度、转变焓的差式扫描热法(DSC)实验曲线以及金属氢化物的制冷过程进行了简介;建立适用于福州地区晴天的太阳辐射量和热管集热器热力学计算模型;利用Matlab软件编写关于福州地区晴天太阳辐射模型的程序,对太阳能集热器的月最佳倾角及其对所接收的太阳辐射量的影响进行理论分析;结果表明,该装置具有结构简单、无需耗电、操作方便、应用范围广等优点。     

相变蓄热式太阳能低温辐射采暖解决方案经济性分析

传统太阳能低温辐射采暖解决方案,将太阳能作为采暖供热源保障室内供暖,供热过程中对太阳能的浪费情况较为严重,存在经济性差的问题。文中提出相变蓄热式太阳能低温辐射采暖解决方案,共包括太阳能集热器、相变蓄热器、保温水箱及供暖系统四部分;方案运行模式包括相变蓄热器单独蓄热、相变蓄热器蓄热与太阳能集热器供暖同时进行、太阳能集热器单独供暖、相变蓄热器单独供暖和电加热装置辅助供暖;通过理论运算公式获取太阳能集热器制热量、集热面积和相变蓄热器蓄热量。实验结果说明,白天使用所提方案的地表温度和室内温度分别为20.4～24.6℃和15.7～20.8℃,供暖和蓄热耗热量分别占总供热量的52.8%和47.2%;夜间使用所提方案的地表温度和室内温度分别为20℃以上和18℃左右,相变蓄热器提供热量占晚间总供热量43%,说明所提方案在保障室内供暖的同时可提高太阳能低温辐射采暖的经济性。     

积极推广蓄冷空调技术

空调蓄冷应用技术已成为实现电网移峰填谷的重要措施,也是空调系统经济运行的基本要求,有关空调冰蓄冷方面 的标准规范编制近况简介如下: (1)由中国商业联合会提出的“蓄冷设备”-SB/T 10343-2001行业标准已在2002年1月1日开始实施。     

太阳能溴化锂吸收式空调性能测试分析

太阳能溴化锂吸收式空调制冷是解决建筑节能降耗和太阳能建筑供能推广应用的重要途径。通过对太阳能热源系统、空调机组制冷系统的性能测试,确定了太阳能吸收式空调的制冷能力和太阳能辐照、冷冻出水温度及水循环流量之间的关系。在太阳能辐照度为700 W/m2、热源供水温度在75℃以上的工况下,溴化锂吸收式空调机组的COP达到0.65左右。太阳能空调内的真空环境和溶液管理措施是影响机组制冷性能的重要因素。     

某商业广场冰蓄冷系统的应用

介绍了一种冰蓄冷空调系统,采用永磁同步变频离心式冰蓄冷双工况制冷机组与基载制冷机组进行蓄冰、供冷。该系统具有配电功率低、日间制冷机组制冷效率高、系统控制简单等特点。结合该商业广场的冰蓄冷设计,对蓄冰方式的设计和运行策略进行了分析,并与常规中央空调系统在投资和运行费用方面进行比较分析。结果表明冰蓄冷系统的经济性好于常规中央空调系统。     

不同送风方式的行级冷却在高热流密度数据中心的应用与优化

目前阶段,数据中心功率密度不断提高,而传统精密空调主要采用地板送风的方式,很难使服务器等通信设备运行的稳定性得到必要保障,因而以热源为基础的行极冷却的重要性逐渐凸显出来且应用前景可观。在此研究中,为重点分析数据中心行极冷却送风方式的具体应用状况,依托有限体积法针对典型数据中心模型展开数值模拟,比较前送风与侧送风优劣势,以具体问题为依据确定两种不同优化方案。而根据实践研究了解到,较之于侧送风,前送风行极冷却可增强机房整体热环境的均匀性,然而远端机柜制冷效果差强人意。经优化处理即可使冷量利用效率不断优化,因而新建高密机房一般以封闭冷通道、空U挡板联合建设方案为首选。     

Ideal Energy‐Level Alignment at the ZnO/P3HT Photovoltaic Interface

Hybrid semiconductor‐polymer nanostructured solar cells hold the promise of photovoltaic energy conversion based on abundant and nontoxic materials and scalable manufacturing processes. After a decade of intense research activity, hybrid solar cells still exhibit low short‐circuit currents and moderate open‐circuit voltages. These bottlenecks call for a detailed understanding of the physics underlying the device operation at the nanoscale. Using first‐principles calculations the ideal energy‐level alignment of hybrid solar cell interfaces based on the wide bandgap semiconductor ZnO and the polymer poly(3‐hexylthiophene) (P3HT) is investigated. The interfacial charge transfer is quantified and it is shown that this effect increases the ideal open‐circuit voltage with respect to the electron‐affinity rule by as much as 0.5 V. The results of this work suggests that there is significant room for optimizing this class of excitonic solar cells by tailoring the semiconductor/polymer interface at the nanoscale.     

Diffusion emission model for solid-state photon-enhanced thermionic emission solar energy converters

Solid-state photon-enhanced thermionic emission (PETE) solar energy converters are new devices that can directly convert solar energy into electrical power at elevated temperatures. This study proposes a new solid-state PETE device structure with a p-type doped semiconductor as the absorber. A model based on a 1D steady-state continuity equation is presented to simulate the diffusion and emission of photogenerated carriers and to calculate the efficiencies. This model can evaluate the effect of device structure and material parameters on performance and efficiency. Calculation results show that the new device is more efficient compared with the original device. A longer electron diffusion length is favourable for enhancing efficiency. Moreover, the optimal absorber thickness is predicted. Our analyses also show that the front interface strongly affects conversion efficiency, which emphasises the need to reduce interface recombination losses. The results of this study may serve as bases for the optimum design of practical solid-state PETE devices.     

分子束外延生长的GaAs/GaInP双结电池研究

We report the recent result of GaAs/GaInP dual-junction solar cells grown by all solid-state molecularbeamepitaxy(MBE).The device structure consists of a GaIn0.48P homojunction grown epitaxially upon a GaAs homojunction,with an interconnected GaAs tunnel junction.A photovoltaic conversion efficiency of 27% under the AM1.5 globe light intensity is realized for a GaAs/GaInP dual-junction solar cell,while the efficiencies of 26% and 16.6% are reached for a GaAs bottom cell and a GaInP top cell,respectively.The energy loss mechanism of our GaAs/GaInP tandem dual-junction solar cells is discussed.It is demonstrated that the MBE-grown phosphide-containing Ⅲ–V compound semiconductor solar cell is very promising for achieving high energy conversion efficiency.     

A charge-separated interfacial hole transport semiconductor for efficient and stable perovskite solar cells

Perovskite solar cells (PSCs) with high efficiency and high stability are still a challenge to produce although remarkable successes have been achieved since they were first reported in 2009. One strategy to effectively improve both the performance as well as the stability is to introduce an interfacial layer between perovskite and hole transport material. Herein, we report a charge-separated (CS) organic semiconductor as the interfacial layer that forms cascaded energy levels between perovskite and hole transportation material. This CS semiconductor displays high hole and electron mobilities by converting long-lived CS states in solution into permanent polarons (charged carriers) in films. Doping with iodinehydride is able to improve the surface morphology of the CS semiconductor layer. Our devices with an iodinehydride-doped CS semiconductor layer exhibit an efficiency of 17.87%, which is increased by ~25% in comparison with 14.24% of the reference devices that have no interfacial layer. This additional CS semiconductor layer also enhances the unsealed device stability by maintaining 90% of initial PCE, while the reference devices degraded by 35% at a relative humidity of 20–30%, temperature of 25 °C and ambient light for 240 h. This result reveals that the utilization of CS states is an alternative approach to construct high charge transport organic semiconductors. An interfacial semiconductor with proper energy level and a matching hole transport mobility can improve the hole extraction, speed up hole transport and suppress charge recombination of PSCs, and thus may be an effective strategy to improve their efficiency and stability.     

高效率有机太阳电池的理论建模

采用综合考虑温度、电场强度、载流子浓度的普遍迁移率模型,利用实际太阳能光谱和非富勒烯材料的吸收系数来计算载流子的产生,结合漂移扩散方程、电流连续性方程等对高效率有机太阳电池进行理论建模。利用该模型计算了器件的电流-电压曲线、开路电压-光照强度曲线和短路电流-光照强度曲线。结果发现,利用该模型计算的电流-电压曲线与实验数据符合很好,其他两种曲线也与实验数据符合较好。此外,利用该模型分析了能量无序度对器件性能的影响,结果表明减小材料的能量无序度可以提高有机太阳电池的性能。     

温差发电器的设计

温差发电器是一种利用大自然中广泛存在的温差进行发电的装置。温差发电器主要由半导体温差发电模块和控制器两部分组成,半导体温差发电模块将热能转化为电能,并通过充电电路将电能储存在蓄电池中;控制器主要完成限流、欠压保护功能。同时,还设计了升压电路,从而使温差发电器输出较高的电压。     

A new class of multi‐bandgap high‐efficiency photovoltaics enabled by broadband diffractive optics

A semiconductor absorber with a single bandgap is unable to convert broadband sunlight into electricity efficiently. Photons with energy lower than the bandgap are not absorbed, whereas those with energy far higher than the bandgap lose energy via thermalization. In this Article, we demonstrate an approach to mitigate these losses via a thin, efficient broadband diffractive micro‐structured optic that not only spectrally separates incident light but also concentrates it onto multiple laterally separated single‐junction semiconductor absorbers. A fully integrated optoelectronic device model was applied in conjunction with a nonlinear optimization algorithm to design the optic. An experimental demonstration is presented for a dual‐bandgap design using GaInP and GaAs solar cells, where a 20% increase in the total electric power is measured compared with the same cells without the diffractive optic. Finally, we demonstrate that this framework of broadband diffractive optics allows us to independently design for the number of spectral bands and geometric concentration, thereby enabling a new class of multi‐bandgap photovoltaic devices with ultra‐high energy conversion efficiencies. Copyright © 2014 John Wiley & Sons, Ltd.     

Modelling free-carrier absorption in solar cells

Free-carrier absorption can be a significant parasitic optical absorption process in solar cells. Although estimates of its influence have been made in the past, it has not previously been incorporated into a numerical semiconductor device simulator and studied in conjunction with other effects. A finite element model of free-carrier absorption is presented that incorporates the dependency of the absorption coefficient on the carrier concentration profile, including the change in carrier density that occurs across a single finite element. This model has been implemented in the semiconductor modelling program PC1D for Windows, and used to simulate the effects of free-carrier absorption on several types of silicon solar cells. It was found to have only a very small effect on cell efficiency, but can significantly affect the long-wavelength spectral response, which has implications for device characterization. Empirical equations for the behaviour of free-carrier absorption in a variety of materials are presented. © 1997 John Wiley & Sons, Ltd.     

A Triple Axial Chirality,Racemic Molecular Semiconductor Based on Thiahelicene and Ethylenedioxythiophene for Perovskite Solar Cells: Microscopic Insights on Performance Enhancement

For the low-cost fabrication of large-area, durable perovskite solar cells, it is of pivotal importance to engineer organic semiconducting films with a combined property of matched energy level, sufficiently large conductivity, high glass transition temperature, and excellent solution processability. Toward this goal, herein an in silico tailored molecular semiconductor (T5HE-OMeTPA) with triple axial chirality, by joint use of thia[5]helicene and ethylenedioxythiophene, is reported. T5HE-OMeTPA with a reduced reorganization energy of hole transfer can be exploited as the hole transport layer for perovskite solar cells with 21% efficiency, which also display excellent long-term stability at 60 °C. The doped, sufficiently conductive T5HE-OMeTPA composite with a glass transition temperature of 121 °C not only exhibits persistent film morphology under thermal stress, but also surprisingly damps the motion of diffusive components of perovskite for a better control of the degradation of photoactive layer. The translational motion of both ions and molecules is intrinsically associated with the glass transition of a doped molecular semiconductor composite, which is in stark contrast to the microscopic fashion for the glass transition of an undoped molecular semiconductor, that is, thermally activated rotation of diphenylamine.