Dynamic Simulation of Solid Adsorption Solar Refrigerator System with AC/CH₃OH as a Working Pair

Solid adsorption system, one of alternative refrigeration systems, is utilized to provide cold for refrigerator or air-conditioner and can be operated by assistance of solar heat. System performance study through computer usage to develop simulation program and simulate behaviors of system operation can give designed system which suits for user’s need. Also, the present study aims to develop dynamic simulation program of solid adsorption refrigeration system operated by solar assistance to simulate behaviors of system operation and its performance. Flat plate collectror is utilized to provide thermal energy for system’s adsorber and activated carbon/methanol is used to be a suitable working pair. Simulation procedure starts with various solar radiation intensities as input energy on solar collector and water is used as collector working fluid. Behavior of system operation can be considered to be 4 steps as isosteric heating, isobaric desorption, isosteric cooling and isobaric adsorption, respectively. This research studies the effect of varying solar radiation intensity on temperature, pressure of adsorber, adsorption ratio at each steps of system operated ranging from 6:00 am (the first day) to 6:00 am (the next day) and system performance which is defined as coefficient of performance, COP. In addition, the simulation result shows monthly average COP of 0.43 compared to a result of another previous research work under the same operating condition and the percentage error is 7.5%.

A new solar coupling regeneration method for liquid desiccant air-conditioning system

A new solar coupling regeneration system is proposed in order to improve the reliability of solar desiccant regeneration system.The new system makes comprehensively use of the solar energy and can also be appropriate for energy-storage in a night operation mode when the electric power supply is at its valley.Comparison of the performance of the new system,the solar thermal regeneration system and the solar electrodialysis regeneration system are made and the influential factors of the performance of the new system are investigated.The results reveal that the new system will be more energy efficient than the solar thermal regeneration system and the solar electrodialysis regeneration system.

Investigation on Evaluation of a Solar Intermittent Refrigeration System for Ice Production with Ammonia/Calcium Chloride and Activated

Experimental results of an intermittent solar absorption cooling system using parabolic collector are presented in this paper. The system used 6 kg of ammonia as refrigerant, 6 kg of calcium chloride as absorbent and 2 kg activated carbon as a solvent. The generator temperature was found to be 105°C. The system could produce ice at –16°C on the average. These are the most advanced results for a solar ice maker so far. All these successful achievements will speed up the commercial processing of a solar ice maker.

Application of Solar Energy for Recovery of Water from Atmospheric Air in Climatic Zones of Saudi Arabia

In the present work, an investigation on the application of solar energy to heat a sandy bed impregnated with calcium chloride for recovery of water from atmospheric air is presented. The study also aimed at evaluating the effects of different parameters on the productivity of the system during regeneration. These parameters include system design characteristics and the climatic conditions. An experimental unit has been designed and installed for this purpose in climatic conditions of Taif area, Saudi Arabia. The experimental unit which has a surface area of 0.5 m2, comprises a solar/desiccant collector unit containing sandy bed impregnated with calcium chloride. The sandy layer impregnated with desiccant is subjected to ambient atmosphere to absorb water vapor in the night. During the sunshine period, the layer is covered with glass layer where desiccant is regenerated and water vapor is condensed on the glass surface. Ambient temperature, bed temperature and temperature of glass surface are recorded. Also, the productivity of the system has been evaluated. Desiccant concentration at start of regeneration is selected on the basis of the climatic data of Al-Hada region, which is located at Taif area, Saudi Arabia. Experimental measurements show that about 1.0 liter per m2 of pure water can be regenerated from the desiccant bed at the climatic conditions of Taif. Liquid desiccant with initial concentration of 30% can be regenerated to a final concentration of about 44%. Desiccant concentration at start of regeneration is selected on the basis of the climatic data of Al-Hada region. The climate of Taif city is dry compared with that for Al-Hada region. This method for extracting water from atmospheric air is more suitable for Al-Hada region especially in the fall and winter.

Thermodynamic Analysis of Solid Oxide Fuel Cell Based Combined Cooling,Heating,and Power System Integrated with Solar-Assisted Electrolytic Cell

Syngas fuel such as hydrogen and carbon monoxide generated by solar energy is a promising method to use solar energy and overcome its fluctuation effectively.This study proposes a combined cooling,heating,and power system using the reversible solid oxide fuel cell assisted by solar energy to produce solar fuel and then supply energy products for users during the period without solar radiation.The system runs a solar-assisted solid oxide electrolysis cell mode and a solid oxide fuel cell mode.The thermodynamic models are constructed,and the energetic and exergetic performances are analyzed.Under the design work conditions,the SOEC mode’s overall system energy and exergy efficiencies are 19.0%and 20.5%,respectively.The electrical,energy and exergy efficiencies in the SOFC mode are 51.4%,71.3%,and 45.2%,respectively.The solid oxide fuel cell accounts for 60.0%of total exergy destruction,caused by the electrochemical reactions’thermodynamic irreversibilities.The increase of operating temperature of solid oxide fuel cell from 800℃to 1050℃rises the exergy and energy efficiencies by 11.3%and 12.3%,respectively.Its pressure from 0.2 to 0.7 MPa improves electrical efficiency by 13.8%while decreasing energy and exergy efficiencies by 5.2%and 6.0%,respectively.

Performance of Desiccant-Based Cooling Systems in Hot-Humid Climates: A Review

This paper reviews the principle and application of the thermally activated desiccant cooling systems with their capability to perform efficiently in hot-humid climates.The paper first introduces the continuous increase of thermal comfort required in building and their relation with the consumption of conventional energy sources.The importance of desiccant cooling technology and its applications has been introduced as well.The energy and environmental issues with the conventional energy supply and the demand with the environmental problems and conditions mainly related to indoor air quality have been also discussed in the second chapter of this paper.The third part of this paper deals with different techniques and systems applied for cooling and dehumidification including the principles of solid and liquid desiccant applications.Indeed,these systems perform well in hothumid climates.The result of a case study of the solid desiccant cooling system combined with solar energy for the desiccant wheel regeneration has been presented in the last chapter in this paper to show the capability of these systems once well applied in a hot-humid climate.

基于流固耦合的单轴跟踪式光伏结构风致扭转研究

以某跟踪式光伏发电系统为研究对象,通过编写自定义程序代码UDF对Fluent进行二次开发,建立单轴跟踪式光伏结构的二维模型,研究其在风荷载作用下的扭转振动问题。研究结果表明:风速达到某一特值后,结构出现等幅周期性振动,发生软颤振现象,而其阻尼比对抑制扭转振动有一定的作用,这同实际情况较吻合;光伏组件倾角在0°~20°范围内时,倾角越大,扭转振动的临界风速越低。

太阳能驱动闭式转轮除湿空调系统性能研究

为解决传统开式转轮除湿空调系统再生排风能量浪费的问题,本文提出了可高效回收再生排风空气显热和潜热的太阳能驱动闭式转轮除湿空调系统,利用TRNSYS软件对系统进行建模,模拟研究了冷水流量比和新风比对系统性能的影响和系统动态性能,并对模拟的准确性进行实验验证。结果表明:模拟结果与实验结果的相对误差最大为±9.8%。太阳能驱动闭式转轮除湿空调系统的最优冷水流量比为1∶5∶4。系统在广州地区整个制冷季(6月1日—9月30日)平均电力COP_(e)为2.4,平均热力COP_(th)为2.1,累计取水量为25.66 t,热回收量为9.70 MW。相比于太阳能驱动开式转轮除湿空调系统,太阳能驱动闭式转轮除湿空调系统平均COP_(e)和COP_(th)分别提高42.1%和69.2%,CO_(2)排放量减少29.3%。

太阳能界面蒸发驱动溶液再生的实验研究

为进一步提高液体除湿空调溶液再生性能,提出一种基于太阳能界面蒸发的溶液再生方式。研究溶液种类、浓度对于再生速率和效率的影响,并与传统热再生及膜再生进行对比。结果表明,在一个太阳强度照射下,温度为26℃、质量浓度为40%的LiCl溶液达到0.39 kg/(m^(2)·h)的再生速率,质量浓度为80%的KCOOH溶液达到0.37 kg/(m^(2)·h)的再生速率。与传统的膜再生以及填料塔热再生相比,该方式展现了较高的再生速率,因此基于太阳能界面蒸发方式有望成为一种新型高效的溶液再生方法。

太阳能耦合固体氧化物电池热电氢联产系统技术经济性分析

固体氧化物电池可在燃料电池发电模式和电解制氢模式间切换,且工作温度为650~850℃,具有高品位余热回收利用的潜力,将固体氧化物电池用于热、电、氢联产可大幅提高设备利用率及能量利用效率。提出了光伏、光热驱动的固体氧化物电池热电氢联产系统,并耦合了蓄电池及熔盐蓄热保障系统连续稳定运行。以总成本最低为目标,构建系统容量配置及运行策略优化的混合整数线性规划模型,并基于品位对口、梯级利用的用能原则,采用夹点分析方法优化全系统多品位能流的梯级利用,揭示耦合系统物质和能量高效集成机理。针对某工业园区太阳能资源及热电氢需求实际案例,固体氧化物电池年满负荷运行小时数高于6 000 h,耦合系统平准化用能成本为0.28元/kW。

Solar air conditioning researches and demonstrations in China

This paper mainly shows the demonstration of solar air conditioning systems in China, which includes LiBr-H2O absorption cooling, silica gel-water adsorption chiller, desiccant cooling and hybrid integrated energy systems for buildings. The match of solar collector types and chiller types have been discussed and suggested.

太阳能-地热能复合利用的溶液除湿空调系统研究

针对传统空调系统采用温湿度联合处理的方式而导致的舒适性差、能源消耗大等问题,以南昌市某建筑为研究对象,利用TRNSYS仿真软件建立太阳能-地热能复合利用的溶液除湿空调系统数学模型,并分析集热器面积及埋管数量对系统性能的影响,在此基础上选取合适的参数对系统全年运行工况进行模拟。同时针对夏季室外新风含湿量波动较大的问题,提出对新风采取分流处理的解决方式。结果表明:在制冷工况下,室内平均温度为26.1℃,相对湿度在50%~65%之间;在供暖工况下,室内平均温度为19.2℃,相对湿度大部分处于40%~60%之间,能够很好地控制室内热湿环境。供暖和制冷季节能效比分别为6.2和4.5,全年性能系数为4.7,明显高于传统的空调系统。

太阳能与矿井水互补转轮除湿空调系统研究

为了充分利用矿井水的低焓地热能,文章构建了太阳能和矿井水互补转轮除湿空调系统,系统用低温矿井水处理显热,用转轮除湿机处理潜热,太阳能和高温矿井水互补驱动转轮除湿机再生。在TRNSYS中进行了建模和模拟。结果表明:当低温矿井水水温≤16℃时,可满足系统显热冷却要求。高温矿井水水温为40℃时,制冷季82.8%的再生热量由矿井水源热泵提供,其余再生热量由太阳能提供。系统制冷季平均热力性能系数COP_(th)为1.5,平均电力性能系数COP_(e)为2.2。与传统蒸汽压缩空调系统相比,太阳能与矿井水互补转轮除湿空调系统节能率可达到55.8%。

基于土壤储热的温室热湿调控系统研究

位于中高纬度地区的温室,都难以避免遇到冬季夜间相对湿度过高、温度较低的问题。针对该问题,基于太阳能“削峰填谷”思想,提出了一种基于土壤储热和固体除湿剂除湿的温室热湿调控系统。该系统结合地中热交换技术,将固体除湿剂脱附后的余热通过土壤储存,能够在冬季将温室夜间相对湿度从92.1%的高湿区间调控到72.3%的作物正常生长区间,平均相对湿度下降19.8%,室内平均温度上升2℃。白天脱附阶段,窄槽式集热器的最高出口温度为153℃,平均集热效率为0.51。土壤白天最高温度为40.2℃,夜间最低温度为8.2℃,在冬季,可为温室中作物提供更适宜的生长环境。

Experimentation of a Membrane-based Concentration Gradient Energy Storage of Liquid Desiccant Solutions Driven by Solar Energy

Solar energy storage is an indispensable and sustainable utilization mode of renewable energy;environment friendly,large-capacity,low heat loss,and long-term storage are critical to improving the integration of solar energy supply.Traditional thermal energy storage mode cannot achieve long-term storage due to the heat loss even under the excellent thermal insulation measures.In this work,a solar-powered membrane-based concentration gradient energy storage of liquid desiccant solutions is presented.In the membrane distillation process driven by solar energy under the right solar radiation conditions,the liquid desiccant solution is concentrated gradually and long-term stored as the concentration gradient energy.To this end,the measured temperature of solar hot water is in the range of 40°C to 90°C from May to September,2018,in Xi’an,China.And then,the LiBr solution(50 wt%),the LiCl solution(35 wt%),and the CaCl_(2)solution(40 wt%)were membrane-based concentrated in the temperature range of 42°C to 63°C,separately.The results showed that the water vapor pressure difference decides the water vapor transferred across the membrane pores from the liquid desiccant side to the air side.The energy storage density of liquid desiccant solutions increases along with the increases in temperature and the membrane area.Consequently,when the LiBr,LiCl,and CaCl_(2)solutions are concentrated from 50%to 55%,from 35%to 40%,and from 40%to 45%,separately,the concentration energy storage density is 245 kJ/kg,350 kJ/kg,and 306 kJ/kg,which is equivalent to or even higher than ice storage capacity.Due to the two independent closed cycle of the liquid desiccant solution and air,the liquid desiccant solution’s concentration gradient energy storage can be long-term stored environment-friendly without any insulation measures.

太阳能液体除湿空调系统再生和蓄能特性的研究

太阳能液体除湿空调系统中,能量在液体除湿剂中以化学能的形式存在,蓄能潜力大,再生温度低,可以利用太阳能或其它低位余热和废热。着重分析了液体除湿空调系统中溶液的再生原理和再生过程的传热传质特性,对再生过程进行了实验研究,获得了再生过程对流传质和对流换热的实验准则方程,讨论了各主要因素对再生量的影响。对再生器的蓄能特性进行了分析,讨论了太阳能液体除湿空调系统蓄能工况的运行方式。

太阳能液体干燥剂除湿潜能储存热质传递过程研究

对液体干燥剂制冷和除湿能力贮存环节进行了分析，给出一种太阳能干燥剂再生转换装置传热传质数学模型．该储能方式没有因储能介质与周围环境存在温差产生的冷热损失，对ＣａＣｌ２和ＬｉＣｌ等典型液体干燥剂的分析表明，理想情况下，二者的储能密度可达１０００ ＭＪ／Ｍ３和 １４００ ＭＪ／ｍ３，远大于水和冰的蓄能密度，储能密度还受太阳辐射、面盖间距、环境条件等因素影响．

太阳能固体吸收式制冰机

介绍了一台以氯化钙(CaCl_2)、氨(NH_3)为工质对的太阳能固体吸收式制冰机的结构及工作原理。运行结果表明,当水平面上日辐射量为20MJ/m^2时,太阳能制冰机的日产冰量为2kg冰/m^2集热器面积。

太阳能驱动的吸附除湿空调系统的研究

提出了一个以太阳能为动力的吸附除湿空调系统。在实验基础上 ,对该系统进行了详细分析。实验与计算表明 ,该空调系统的制冷效率约为 18%。所得数据为该空调系统的进一步完善提供了依据。

真空集热型太阳能固体吸附式制冷的理论研究

为提高太阳能吸附制冷系统的集热性能 ,提出了采用真空集热管式吸附床的太阳能固体吸附制冷系统 ,并对选择吸收式和直接吸热式的真空集热制冷系统分别进行了理论分析与计算模拟。这两种系统均具有较高的制冷性能 ,前者宜以沸石 -水为制冷工质对 ,而后者则宜采用活性碳 -甲醇工质对。分析了工作参数对这两种真空集热型制冷系统的影响 ,并对系统结构进行了优化研究。