Analysis on the optimum matching of collector and storage size of solar water heating systems in building space heating applications

The overall thermal performance of a solar water heating (SWH) system is significantly affected by the mismatch between the temporal distribution of solar radiation and the heating load. Therefore, a favorable correlation between the collector and storage size should be generated based on the dynamic characteristics of the system. This study focuses on the optimal matching of solar collector area with storage volume for an SWH system (with short-term heat storage capability) for a space heating application. A simplified model of an SWH system based on hourly energy flow is established. System control strategy is integrated into the model in a simple manner without sacrificing computing speed. Based on this model, the combined effect of collector area and storage volume on system thermal performance and economy is analyzed, and a simple procedure for determining the optimal system size is illustrated. A case study showed that for an SWH system utilized for space heating application, the optimized ratio between storage volume and collector area is dependent on the total collector area of the system, and is dominated by the requirement of overheating prevention. The minimum storage volume for a specific collector area that can prevent the storage tank from being overheated can be adopted as the optimum storage volume for that collector area. The optimum ratio between storage volume and collector area increases as the collector area increases. Therefore, a trade-off between heat collection and heat loss has to be made while attempting to increase solar fraction by improving collector area.     

Study on the performance of a solar assisted air source heat pump system for building heating

This paper proposed a new solar assisted air source heat pump system with flexible operational modes to improve the performance of the heating system. A mathematical model was established on the solar assisted air source heat pump system for building heating with a heating capacity of 10 kW, and an air source heat pump unit was developed to validate the model. The effect of the solar collector area on the performance of the system running in Nanjing was studied. The results showed that the COP of the heat pump unit was enhanced with the increase of the solar radiation density during the typical sunny day in the heating season. In addition, the COP also increased in proportion to the solar collector area. Compared with the case when the solar collector area was 0 m², the COP increase of the heat pump and the energy-saving rate were 11.22% and 24% respectively when the solar collector area was 40 m². Meanwhile, the solar equivalent generation power efficiency could reach 11.8%.     

敞开式太阳能集热/再生器的理论模型及性能分析

对敞开式太阳能集热再生器建立理论解析模型,理论求解发现溶液在常温下再生时存在一个最佳单位面积流量使单位面积蒸发率最大。溶液入口温度和室外风速是决定最佳流量值的2个最重要参数,溶液浓度和太阳辐射强度对最大蒸发率影响最明显。当溶液出口温度低于入口温度时,最佳流量不存在,溶液流量越大再生效果越好。当室外风速为2m/s时,溶液再生蒸发率最大。文章全面揭示了影响敞开式集热/再生器性能的各项因素。     

上海地区高校学生宿舍太阳能热水系统一体化设计研究

本文从分析上海地区太阳能资源入手,说明了上海地区高校学生宿舍应用太阳能热水技术的必要性和可行性,分析了上海地区高校学生宿舍太阳能热水系统一体化设计的几个关键问题,包括集热器与屋面结合方式、集热器方位与角度确定、集热器选型及面积确定、集热器安装位置确定等内容。得出的结论对同类项目有一定的参考价值,对其他夏热冬冷地区的太阳能热水系统与高校宿舍一体化设计也有一定的借鉴意义。     

太阳能热水系统与建筑一体化的实践与思考

首先叙述了太阳能集热器的背景与分类,并列举了平板集热器的一些优势,然后介绍了太阳能热水系统的设计原理及其与建筑一体化设计时的主要方案,从室内热负荷的选取及太阳能集热器的面积计算两方面作了具体分析,进而提高太阳能的利用效率。     

连续阴雨雪天对太阳能取暖住宅的影响及解决

叙述了国内外太阳能利用的发展现状与趋势，提出了北方地区的冬季取暖问题从太阳能利用现状来看还没有得到充分解决的原因，还论述了解决集热板的面积少、集热板的安装位置不够用、储热箱的安装位置及大小不当等问题的方式方法。     

Prediction of the optimum slope and surface azimuth angles using the Genetic Algorithm

In this paper, the Genetic Algorithm is applied to calculate the optimum slope and surface azimuth angles for solar collectors to receive maximum solar radiation. An area of Iran is selected to verify the results of this algorithm. The optimum angles and the collector input solar energies for these angles are calculated in hourly, daily, monthly, seasonally and yearly bases respectively. Then, the influence of different combinations of solar radiation components on the optimum slope angle and the energy gain is investigated. The results show that the Genetic Algorithm is a useful technique to find the optimum angles specifically when the number of independent parameters is large. The results show that the daily, monthly and yearly optimum surface azimuth angles for receiving the maximum solar energy are zero. Adjusting the collector at the daily optimum slope angle slightly increases the collector input energy compared with the case of monthly optimum slope angle so that the gain of solar energy is almost the same. The results also show that the hourly optimum surface azimuth angle is not zero and mounting the solar collector at the hourly optimum slope and azimuth angles increases the input energy significantly compared with the case of daily optimum angles. It is shown that the optimum slope angles are mostly dependent on the beam solar radiation. Furthermore, the results indicate that the optimum slope angles of solar collector and Photovoltaic panels are almost the same.     

太阳能-电辅热供暖系统的经济优化

集热器面积的选择是太阳能供暖系统设计的关键,本文对太阳能-电辅热供暖系统进行了技术经济分析,建立了系统费用年值与集热器面积函数关系的数学模型,分析探讨了使费用年值最小的集热器面积的计算方法。并以太原为例(100m2住宅)逐日进行了计算,结果表明当集热器面积为21.34m2,整个系统的费用年值最小;整个采暖季的太阳能保证率为60.24%。     

燃气与太阳能联合供热系统集热器面积优化

根据多项典型燃气与太阳能联合供热系统工程实例,得到太阳能集热器面积与太阳能集热系统造价间的关系。以寿命期内最大净收益为目标,考虑太阳能获得率与天然气价格,优化了太阳能集热器面积。     

Effect of flat plate collectors in parallel on the performance of the active solar still for Indian coastal climatic conditions

The effect of flat-plate collectors (FPCs) when connected in parallel on, in particular, the heat transfer coefficients and, in general, distillate output and the efficiency of solar still has been studied in the active mode. The solar still has an effective basin area of 1?m² and fixed cover inclination of 30°. Each FPC with an effective area of 2?m² is attached to the solar still. An effective collector inclination of 5° is used. Experiments have been conducted for 24?h in summer for the active solar distillation system at Kakinada (16°.93′N/83°.33′E), India, which has coastal climatic conditions. The aim of the present work is to study the variation in internal heat transfer coefficients with respect to the number of FPCs coupled with the solar still in parallel. It is understood that the heat transfer coefficients depend significantly on the size of the collector. The size of the collector is increased by increasing the number of collectors. It is also observed that this leads to an increase in distillate output but a decrease in efficiency of the solar still.     

基于逐时太阳辐射强度与动态逐时负荷分析的太阳能空调系统设计要点研究——以天津市某办公楼项目为例

建筑的地理气候特征影响太阳能在建筑中的收集与利用。以天津市某办公楼项目为例,基于日照遮挡模拟分析确定集热器布置区域,并根据逐时动态冷负荷与热负荷综合情况确定集热器面积,以动态逐时负荷与供热(冷)量匹配的方法辅助备用能源设计,降低了系统的造价,提高了太阳能的利用率和建筑供能系统的稳定性,为后续其他项目太阳能空调系统的设计提供了借鉴。     

太阳能热泵供热系统性能的试验研究

对太阳能热泵系统的不同运行工况进行了试验研究。分析了蒸发器入口水温、冷凝器入口水温对热泵系统性能的影响。通过研究分析得出:太阳能集热器面积与热泵机组的匹配为影响系统性能的重要参数,应根据用户对热量的需求来选择;蒸发器入口水温可在5℃—20℃之间变化,在20℃时,系统COP最高达到3.6。通过对试验结果的分析,为太阳能热泵系统的设计和运行控制提供了依据。     

Thermal performance analysis of the glass evacuated tube solar collector with U-tube

In this paper, based on the energy balance for the glass evacuated tube solar collector with U-tube, the thermal performance of the individual glass evacuated tube solar collector is investigated by analytical method. The solar collector considered in this study is a two-layered glass evacuated tube, and the absorber film is deposited in the outer surface of the absorber tube. The heat loss coefficient and heat efficiency factor are analyzed using one-dimensional analytical solution. And the influence of air layer between the absorber tube and the copper fin on the heat efficiency is also studied. The results show that the function relation of the heat loss coefficient of the glass evacuated tube solar collector with temperature difference between the absorbing coating surface and the ambient air is nonlinear. In the different ambient temperatures, the heat loss coefficient of the solar collector should be calculated by different expressions. The heat efficiency factor will be subject to influence of air layer between absorber tube and the copper fin. Specially, the influence is remarkable when the heat loss coefficient of the collector is large. When the synthetical conductance amounts to 5 W/m K, the solar collector efficiency decreases 10%, and the outlet fluid temperature decreases 16% compared with the case which the air thermal resistance is neglected. And the surface temperature of the absorbing coating increases 30 °C due to the effect of air thermal resistance. So the surface temperature of the absorbing coating is an important parameter to evaluate the thermal performance of the glass evacuated tube solar collector.     

Application of solar energy for milk pasteurisation: a comprehensive review for sustainable development

ABSTRACT

Solar energy is available freely. Hence, nowadays people are working on solar energy when compared with conventional sources of energy. Dairy industries require heat, which can be generated by the use of boiler with the aid of wood. Hence, due to increment in global warming, it is necessary to use renewable energy. The primary aim of this review paper is to study various researchers’ work on solar milk pasteurisation system. Hence, it also covers important aspects required for solar pasteurisation like flat plate collector, heat exchanger and solar water heating system.     

Experimental analysis of the performance of a solar flat plate water heater with and without internal fins

Generally increasing, an increase in the surface area will increase the heat transfer capability of a solar collector and possibly its efficiency. Conventional solar water heaters have longitudinal fins attached externally to the collector tubes for reaping the benefits of enhanced heat transfer. Attempts have been made towards providing internal fins (spirally grooved copper tubes), in addition to the existing external fins for analysing its influence on efficiency and outlet temperature. Two identical solar water heaters with a capacity of 25?L per day were designed and fabricated, one with a collector with plain (unfinned) internals and another with internal grooving (finned tube). The paper details the temperature profile observed in the two collectors, variation of thermo-siphon mechanism and change in efficiency of the solar water heaters with respect to time. It has been observed that providing internal fins had led to an increase in efficiency of about 4.5% as compared to conventional plain tubes.     

双水箱太阳能热水系统贮热水箱容积的比较研究

针对设置双蓄热水箱的集中式太阳能热水系统,以辅助热源能耗为目标,分析了不同贮热水箱容积的设置对系统辅助热源能耗的影响。并通过运用TRNSYS软件,建立动态分析模型,比较分析了不同太阳能保证率条件下,单位面积集热器对应的贮热水箱容积对系统性能的影响。分析结果表明:单位面积集热器对应的蓄热水箱容积最优值分布在50~70 L/m~2范围内;贮热水箱的容积对系统能耗的影响较小,在单位面积集热器对应的蓄热水箱容积为40~100 L的推荐值范围内,其辅助热源的最大值与最小值差异在1%以内。     

Thermal performance analysis and economic evaluation of roof-integrated solar concrete collector

This paper examines the thermal performance of a roof-integrated solar concrete collector for reducing heat gain to a house and providing domestic hot water. The solar concrete collector is made of PVC pipes embedded in deck slab or concrete roof. No glazing on the top of the solar concrete collector or insulation at the back has been used as in conventional solar water heaters. To compare the energy saving, two test rooms of 2.3 m width, 2.5 m length and 2.5 m height were built. In the first room, the reinforced cement concrete (R.C.C.) slab was used as deck slab whereas the second room was equipped with a cement concrete solar collector. The experimental results showed that the cement concrete solar collector is extremely interesting as it can produce up to 40 l of hot water per day at water temperatures ranging from 40 to 50 °C. A mathematical model based on the conservation equations of energy is developed to predict the performance of the cement concrete solar collector. There is reasonable agreement from the comparison between measured data and predicted results. The economic analysis indicates that the payback period is rather fast.     

太阳能采暖系统在云南部分地区的应用探讨

针对云南地区的能源供应和冬季采暖状况,结合该地区的太阳能资源,对太阳能采暖的适用性进行了探讨,并进行了经济性分析和环保效益分析.主要研究内容包括:太阳能采暖系统的选择、太阳能集热器的安装面积及其布置原则、太阳能蓄热水箱大小的确定.结论证明,与其他采暖方式相比,在云南地区推广太阳能采暖系统是可行的.     

Experimental energy and exergy analysis of a double-flow solar air heater having different obstacles on absorber plates

This paper presents an experimental energy and exergy analysis for a novel flat plate solar air heater (SAH) with several obstacles and without obstacles. For increasing the available heat-transfer area may be achieved if air is flowing simultaneously and separately over and under the different obstacle absorbing plates, instead of only flowing either over or under the different obstacle absorbing plates, leading to improved collector efficiency. The measured parameters were the inlet and outlet temperatures, the absorbing plate temperatures, the ambient temperature, and the solar radiation. Further, the measurements were performed at different values of mass flow rate of air and different levels of absorbing plates in flow channel duct. After the analysis of the results, the optimal value of efficiency is middle level of absorbing plate in flow channel duct for all operating conditions and the double-flow collector supplied with obstacles appears significantly better than that without obstacles. At the end of this study, the exergy relations are delivered for different SAHs. The results show that the largest irreversibility is occurring at the flat plate (without obstacles) collector in which collector efficiency is smallest.     

Experimental and numerical investigation of a thermosyphon solar water heater

ABSTRACT

This paper presents the optimisation of a flat-plate solar collector commonly used in thermosyphon solar water heaters. The optimisation that helps to obtain the right optimum combination of the selected design parameters that maximises the performance of the collector was based on the genetic algorithm. The optimisation results also show the ability of the heater to achieve high performances with lower area of the collector and consequently lower price. Based on the optimisation results, a thermosyphon solar water heater was constructed with local materials; and tested under the climatic conditions of two cities of Cameroon. The experimental results show the ability of the heater to produce hot water and the applicability of solar water heaters in Cameroon. The experimental and numerical results have also been confronted, and the concordance proves to be acceptable.