Energy and Buildings
Experimental and theoretical analysis on thermal performanceof solar thermal curtain wall in building envelope
Keywords: Solar thermal curtain wall Thermal performance
Heat transfer coefficientSensitivity analysis
Abstract
The need for energy efficient building design has stimulated the integrating buildings with energy sys-tems. In this paper, a novel solar thermal curtain wall (STCW), which is the solar collector installed as abuilding envelope or integrated to normal facades, is developed. A stand-alone house with the STCW wasconstructed and thermal performance of the STCW was tested and theoretically analyzed. The resultsshowed that the STCW combined energy production for hot water supply with other functional featuresof architectural, structural and aesthetic as a new kind of building component. In typical summer dayand winter day, the efficiency of the STCW system were 56.8% and 41.0%, respectively. The heat trans-fer coefficient of the STCW varied monthly, with the maximum value recorded being 1.99 W mminus;2Kminus;1in August and the minimum value recorded being 0.86 W mminus;2Kminus;1in January. A sensitivity analysis wasmade to investigate variations on the heat transmission load of the solar curtain wall. The results showthat the transmission heating load can be reduced by about 39% when the insulation is increased from25 mm to 50 mm. A comparison between the solar collector integrated with traditional wall and solarcurtain wall only was made. Integrated solar collector to wall provides more damping of load fluctuationand smaller peak load, compared with traditional walls, the heating load of faccedil; ade-integrated walls areless and the walls even contribute heating for the building. Though the cooling load was increased, thecomprehensive performance for the faccedil; ade-integrate walls are superior to the traditional walls.
copy; 2014 Elsevier B.V. All rights reserved
- Introduction
Buildings in major cities worldwide are in huge requirementof air conditioning and hot water. Thus renewable energy is pop-ular in buildings to enhance the building energy efficiency andbuilding-integrated solar thermal system has experienced a greatdevelopment. The integration of photovoltaic and solar thermalcollectors into the walls or roofing structure of a building couldprovide greater opportunity for the use of renewable solar energytechnologies. A substantial amount of research has been done onbuilding integrated solar water heating system [1–7]. The roof andthe wall are distinctively used as integrative thermal building ele-ments, which means that the roof and the wall performed thefunctions of a building envelope, as well as a component to collectsolar energy. Due to its advantages such as clean and low operation cost, solar hot water system contributes a lot to make buildingsenergy efficient. However, many studies have addressed on the per-formance of the solar system [8,9] and building-integrated PV walls[10–13].
Actually, the heat gain through the solar curtain wall may affectthe indoor climate environment which has influence on the energyconsumption of air conditioning or heating. Study of the thermalperformance of the solar thermal curtain wall (STCW) is usefulfor the wall to reduce indoor cooling loads under the premise ofhigh efficiency of energy generation. There are only a few studies[10–12,14] done on the thermal performance of the solar curtaincollector as building envelope. These studies report that solar ther-mal collectors show good performance in reducing the space load.Tomas et al. [1] investigated the faccedil; ade-integrated solar thermalcollectors for water heating and found that faccedil; ade solar collectorshould have an area increased by approximately 30% to achievethe usual 60% solar fraction compared with conventional roof solarcollectors with a 45◦slope and building behavior is not stronglyaffected by faccedil; ade collectors when sufficient insulation layers arepresented. Motte [15] presented a new concept of solar collectorintegrated into a rainwater gutter and investigated on the thermal performance of the system. Maria et al. [3] addressed a survey to more than 170 European architects and gave out an integration criteria, design guidelines and a methodology to design future solar thermal collectors system suited to building integration. Ji et al. [16] studied the annual performance of faccedil; ade-integrated hybrid photovoltaic/thermal collector system used in residential buildings of Hong Kong and got the results that the performance of the system was better than the conventional solar collector and space heat gain was reduced compared with traditional concrete wall. Hongxing Yang et al. [10] compared the PV walls and massive walls and found that the photovoltaic integration in building walls reduced the corresponding cooling load components by 33–50%.
The main objective of this research is to study the heat transfer coefficient and the transmission load of the solar thermal curtain wall and compare it with traditional walls. A solar thermal curtainwall incorporated with a house was constructed and tests were carried out to study the thermal performance of the system and the solar curtain wall. In order to evaluate the integrative energy performance of the STCW, a simulation model based on heat trans-fer theory was built. This paper first presents a brief review of the experimental results and validation of the simulation model and a year round performance of STCW.
2. Description of the solar thermal curtain wall
2.1. Construction of the STCW
The solar thermal curtain wall (STCW) system is a solar thermal system with collectors installed as a building envelope or an inte-grating curtain collector to normal facades. The STCW combines energy production with other functional features of architectur
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能源与建筑
在建筑围护结构的热性能的太阳能光热幕墙
的实验和理论分析
关键字: 太阳能热幕墙 热性能 传热系数敏感性分析
摘要：
节能建筑设计的需要，刺激了建筑与能源系统的整合。在本文中，一种新型太阳能幕墙（STCW）开发了，这是安装作为建筑围护结构或集成到正常外墙太阳能集热器。一个构建的STCW公约和STCW公约的热性能进行了测试，从理论上分析了独立的房子。结果表明，STCW联合能源生产热水供应与建筑其他功能特点、结构和美学作为一种新型的建筑构件类。在典型的夏日和冬日，STCW公约的系统效率分别为56.8%和41%。STCW公约的传热系数变化的月，最大值记录为1.99 W Mminus;2kminus;1在八月和最小值记录为0.86 W Mminus;2kminus;1在一月。对太阳能幕墙的传热负荷变化进行了敏感性分析。结果表明，当绝缘从25毫米增加到50毫米，传输的热负荷可以减少约39%。太阳能集热器与传统墙体和太阳能幕墙的比较。与墙体相比，太阳能集热器提供了更大的阻尼，负载波动小，峰值负荷小，与传统墙体相比，外墙整体墙体的采暖负荷较小，墙体甚至有利于采暖。虽然冷负荷的增加，综合幕墙的综合性能优于传统的墙壁。
copy;2014 Elsevier公司保留所有权利。
- 介绍
世界各大城市的建筑都对空调和热水有着巨大的要求。因此，可再生能源在建筑流行加强建筑节能与建筑一体化的太阳能热系统经历了巨大的发展。一体化光伏和太阳能集热器在墙壁或屋顶的一种建筑结构可以为可再生能源太阳能技术的使用提供更大的机会。对太阳能热水系统的建设已经进行了大量的研究[1-7]。屋顶和墙壁作为综合热建筑元素是特殊的，这意味着屋顶和墙进行围护结构的功能，以及一个组件来收集太阳能。太阳能热水系统以其清洁、运行成本低等优点，极大地提高了建筑的节能效果。然而，许多研究已经解决了性能上的太阳能系统[8-9]和光伏建筑一体化的墙[10-13]。
实际上，太阳能幕墙的热量增益会影响室内气候环境，从而影响空调或采暖的能耗。对太阳能光热幕墙的热工性能研究（STCW）墙上的发电效率高的前提下，减少室内冷负荷是有用的。只有少数的研究[ 10–12,14 ]作为建筑围护结构的太阳能集热器热性能做窗帘。这些研究报告，太阳能热收藏家显示降低的空间负荷性能好。托马斯等人[ 1 ]对立面整合太阳能集热器热水发现立面太阳能集热器应该有一个面积增加约30%，达到平时的60%太阳能与传统的屋顶太阳能集热器与一个45◦边坡和建筑物的行为是不受强烈的正面收藏家当足够的绝缘层了。Motte [ 15 ]提出了一种新的太阳能集热器集成到一个雨水天沟及对系统热性能的研究概念。玛丽亚等人[ 3 ]针对超过170名欧洲建筑师进行了一项调查，并给出了一个整合标准，设计准则和方法来设计未来的太阳能集热器系统，适用于建筑一体化。Ji等人[ 16 ]研究了立面整合混合光伏/集热器系统用于香港住宅年度工作和取得的成果，系统的性能明显优于传统的太阳能集热器的热增益和空间与传统的混凝土墙相比降低。洪星洋等人[ 10 ]对比光伏墙和巨大的墙壁和发现建筑墙体的光伏一体化降低了相应的冷却负荷组成的33–50%。
本研究的主要目的是通过太阳能光热幕墙的传输负载的传热和它与传统的墙比较研究古代和系数。一个太阳能热幕墙与房子的建设和测试进行了研究系统的热性能和太阳能幕墙。为了评价综合节能性能STCW公约，建立了一个基于传热模型理论仿真模型。本文首先提出了一种实验结果的一个简短回顾和验证仿真模型和全年STCW的性能。
Nomenclature
A area (m2)
C specific heat capacity (J kgminus;1 Kminus;1)
hc convection coefficient (W mminus;2 Kminus;1)
hcminus;a convection coefficient between cover and ambient
hr,cminus;a radiation heat transfer coefficient between cover and ambient
hcminus;p convection coefficient between cover and plate
hr,cminus;p radiation heat transfer coefficient between cover and plate
k thermal conductivity (W mminus;1 Kminus;1)
Gr Grashof number
Pr Prandtl number
Nu Nusselt number
g gravitational acceleration (m sminus;2)
I solar irradiation flux (W mminus;2)
t temperature (K)
v wind velocity (m sminus;1)
q heat flux (W mminus;2)
R thermal resistance (m2 K Wminus;1)
W width (m)
Wo distance between the tubes (m)
Do outside diameter (m)
Di inside diameter (m)
L height of the solar collector (m)
H height of the room (m)
Greek symbols
r time (s); transmittance
p density (kg mminus;3)
ı thickness (m)
入 thermal conductivity (W mminus;1 Kminus;1)
˛ absorption rate
ε emissivity
� difference
Subscripts
a ambient air
c glass cover
p absorber plate
w wall
ins insulation material
f fluid
e emittance
s sky
col solar collector
i indoor room
- 太阳能热幕墙的描述
2.1 STCW公约的建设
太阳能光热幕墙（STCW）系统是一个太阳能集热系统的安装作为建筑围护结构或一个完整的光栅窗帘器正常外观的收藏家。STCW结合建筑其他功能的能源生产，结构和美学作为一种新型的建筑构件类。太阳能组件集成在建筑围护结构可以提供一个重要的贡献，可再生能源利用和设备执行一个信封的功能，同时将收集太阳能加热的目的。STCW公约的系统可以降低空调负荷时，它执行的功能的信封，对外墙和屋顶间的室内和室外环境和太阳能幕墙的保温，是最具成本控制的外部因素让家更舒适有效的方式进行面间。STCW还可以为洗澡间，厨房，游泳池等供应热水，使高层建筑供太阳能使用和避免楼顶权属争议问题为窗帘器作为信封或集成到门面。此外，幕墙学院讲师模块可以被制成一个施工单元（幕墙、屋面等）、材料和颜色可以考虑建筑，简化了集成设计。
一种太阳能集热器的集成独立的房子仍然包裹了太阳能光热幕墙热工性能研究。图1显示了实验装置。作为建筑围护结构，太阳能幕墙也可用于家庭热水生产。进行了实验研究的房子，从三个集热器模块在垂直连接，形成两个并联电路中的一个平行的壁，使得每个列的集电极可以具有相同的进水温度从水箱。
太阳能光热幕墙模块，实际上是一个由一层透明的玻璃板，一层高度吸收板、管和绝缘材料组成的平板集热器。板基本上是一个管板型板。图2显示了太阳能热幕墙模块的层。模块的结构参数如表1所示。
图1太阳能幕墙系统的出现
图2 平板集热器的结构图
对太阳能光热幕墙的独特的优点如下：（a）它可以节省传统能源，减轻环境污染；（b）增加了太阳能应用领域安装太阳能集热器，只在屋顶上进行比较；（c）提高室内环境的舒适性和遮光隔热；（d）减少空调负荷。然而，主要的挑战是初始投资较高，相比传统的墙壁和安装集热墙或整合器壁降低了系统的有效性。
表1太阳能幕墙组件结构参数
|
Collector |
Width (m) |
0.885 |
|
Length (m) |
1.905 |
|
|
Area (m2) |
1.686 |
|
|
Glass cover |
Thickness (m) |
0.003 |
|
Air gap |
Depth (m) |
0.018 |
|
Absorb plate |
Thickness (m) |
0.003 |
|
Tube |
Outside diameter (m) |
0.010 |
|
Inside diameter (m) |
0.009 |
|
|
Length (m) |
1.795 |
|
|
Separation between adjacent water tubes (m) |
0.115 |
|
|
Insulation layer |
Thickness (m) |
0.250 |
2.2 太阳能热幕墙系统及数据采集
图3显示了太阳能热水回路的示意图。该系统由太阳能集热器(用作墙),储水槽、水泵、膨胀水箱、管道和风机盘管单位组成。六个单位组成都安装有建筑南墙。总的SCTW面积为10m2。收藏家的水系统还包括一个0.5m3的储水箱。贮水集热器面积比为50L M -2。循环泵提供了一个通过集热器固定在质量流量0.12kgsminus;1的强制循环水。
对集热循环水由循环水泵是被迫在太阳能集热器阵列，导致热水流入储罐中时，流经水箱中的换热盘管加热。泵由太阳能控制器控制。在集热循环泵启动，当水箱底部的集热器的出口温度差超过10◦C和关闭时的差异小于4◦C时，供热循环热水泵风机盘管冬季供热。在供热循环泵继续运行时出口温度超过50◦C和进出口循环温差超过5◦C.泵停泵时的温度差小于3◦C.
利用电阻温度传感器测量的温度（真正的plusmn;0.1◦C精度），这是位于集热器入口和出口附近的系统，在家里的内外壁表面，如图3所示，分别测量以确定进、出集热温度、环境温度、室内空气温度和外表面的温度。通过超声波流计测定介质的流量（1–5%精度）。一个TBQ-2辐射计，这是校准绝对无误的1 W Mminus;2实验前，安装了90◦倾角测量太阳辐射。
- 性能指标的定义与计算
3.1 太阳能幕墙的日平均热效率
日平均热效率是一个重要的参数，可以反应太阳能集热器的太阳能幕墙热工性能。它可以通过以下公式计算：
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