Assessing solar hot water system performance with GIS

Current solar hot water (SHW) system modelling techniques, as applied in Australia, are inadequate for the demands of programs and policies that aim at widespread usage of SHW. Two major problems with current modelling techniques are the coarseness of modelling in a spatial context and the use of only two hot water load categories. These problems are described and suggestions are offered for improved modelling processes. Geographical information systems can be used in conjunction with existing SHW performance evaluation tools to produce models with much finer spatial resolution than those currently in use. It is recommended that categories used for evaluating SHW systems should be based upon household size. Methodologies for modelling SHW system performance that conform to these recommendations are described in this paper.     

集中式太阳能热水系统的性能研究

太阳能保证率是评价太阳能热水系统节能效果的重要指标,但实际运行情况表明,该评价指标具有一定的局限性,且仅按照此评价指标对热水系统进行评价达不到预期的节能效果。鉴于此,文章以天津某住宅的集中式太阳能热水系统作为研究对象,建立该热水系统的数学模型,并对该热水系统的性能指标进行模拟计算。文章基于模拟结果,研究了集中式太阳能热水系统全年的运行性能以及用户用水量、控制策略对该热水系统运行性能的影响,提出了应采用太阳能保证率、太阳能利用率、常规能源有效替代率和系统散热比4个参数作为太阳能热水系统的性能评价指标,以及适当减少供水循环时间的控制策略。     

Analytical approach of thermosyphon solar domestic hot water system performance

An efficient and simple simulation approach for thermosyphon solar water heaters has been developed and compared with experimental data. This approach, valid for solar-only systems, gives the ability to link the system main design and constructional parameters with the expected energy output through an analytical determination of the coefficients of the characteristic input–output equation of the system. The proposed methodology can be used not only for energy optimization of the system in the design phase but also for evaluation of test results of an existing system in order to improve it further.     

Design of a commercial solar hot water system

The paper critically evaluates the design and performance of a commercial hot water system. These systems are installed in IIT Delhi hostels mainly for cooking and washing utensils. In some of these systems, heat exchangers are also used. In specific terms, one can regard the thermal efficiency and the maximum hot water temperature as indicators of the performance of the system. Hence different parameters of the heat exchanger and the number of collector panels directly affect the performance of the system. In the paper, an energy balance for different components of the system under steady state conditions is primarily investigated. It is found that excellent agreement exists between experimental and theoretical results for the proposed design parameters.     

Experimental performance evaluation of a novel heat exchanger for a solar hot water storage system

The performance of a novel heat exchanger unit (‘Solasyphon’) developed for a solar hot water storage system was experimentally investigated. The ‘Solasyphon’ is a simple ‘bolt-on’ heat exchange unit that can be integrated externally to a traditional single-coil hot water cylinder (HWC) avoiding the costly replacement of an existing HWC with a twin-coil HWC. The installation cost of a ‘Solasyphon’ is lower compared to a traditional HWC thus offers greater cost effectiveness. A data acquisition system was designed to compare the thermal performance of an integrated ‘Solasyphon’ HWC with a traditional twin-coil HWC under controlled simulated conditions. The analysis was based on experimental data collected under various operating conditions including different primary supply temperatures (solar simulated); primary supply patterns and draw off patterns. The results indicated that the ‘Solasyphon’ delivered solar heated water directly to the top of the HWC producing a stratified supply at a useable temperature. Under variable solar conditions the ‘Solasyphon’ would transfer the heat gained by a solar collector to a HWC more efficiently and quickly than a traditional HWC. The ‘Solasyphon’ system can reduce installation costs by 10–40% and has a lower embodied energy content due to less material replacement.     

运行状态下太阳热水系统热性能测试方案

按照热力学原理、根据国家标准对已竣工的江苏五台山体育中心游泳馆太阳热水系统工程,提出了运行状态下的系统热性能验收测试方案,进行了测试工作,并取得测试结果.所提出的运行状态下的系统热性能验收测试方案,解决了工程热性能验收问题,具有实用价值.     

Experimental study of the burning-cave hot water soil heating system in solar greenhouse

In the northern China areas, the traditional heating methods are widely used in solar greenhouse, for example: electric heating, hot air heating, hot water heating, burning-cave heating etc. If copying the assuring building indoor environment of constant heating ways into solar greenhouse, it will further increase building energy consumption, thus improving the efficiency of energy utilization, establishing appropriate growing environment, and realizing the agricultural waste recycling are important ways of consistent with the Chinese conditions, construction of sustainable development, improving the efficiency of the greenhouse production. To solve the problem of traditional heating method for high heating energy consumption, the inharmonious between greenhouse air temperature and soil temperature, uneven soil temperature, the research build the burning cave hot water soil heating system of solar greenhouse experimental platform in accordance with principle of energy cascade utilization. This experiment platform will transfer burning cave internal heat into soil heating system. The soil is evenly heated by system. Through testing the actual operation effect of the burning cave hot water soil heating system of new solar greenhouse, electric heating system, no taking any heating measures system, burning cave hot water soil heating system of solar greenhouse can improve the soil average temperature 5 ∼ 6 °C. This research provides experimental basis for practical applications and promotion.     

Enhancement of natural circulation type domestic solar hot water system performance by using a wind turbine

Performance improvement of existing 200 litres capacity natural convection type domestic solar hot water system is attempted.A two-stage centrifugal pump driven by a vertical axis windmill having Savonius type rotor is added to the fluid loop.The windmill driven pump circulates the water through the collector.The system with necessary instrumentation is tested over a day.Tests on Natural Circulation System(NCS)mode and Wind Assisted System(WAS)mode are carried out during January,April,July and October,2009.Test results of a clear day are reported.Daily average efficiency of 25-28% during NCS mode and 33-37% during WAS mode are obtained.With higher wind velocities,higher collector flow rates and hence higher efficiencies are obtained.In general,WAS mode provides improvements in efficiency when compared to NCS mode.     

太阳能热水空调建筑一体化系统

设计了太阳能热水空调建筑一体化系统。该系统由2台冷水水冷机组、2个平板型太阳能集热器单元、1个贮热水箱、2个贮冷水箱和77台供冷终端组成,为海南省昌江县人民医院内儿科77个病房提供空调冷量和洗澡用热水。该系统初投资少,设备利用率高。经过1年的应用运行,取得了节约能源、减少对环境热污染的效果,为更好地推广应用太阳能探索一条新的路子。     

某宾馆太阳能热水洗浴系统介绍

介绍了解放军总后勤部某宾馆太阳能热水洗浴系统,重点阐述了太阳能定温放水与电辅助加热相结合的热水供应系统的运行原理,总结了系统设计应注意的问题。     

Experimental study of the performance of multieffect solar thermal water desalination system

The pilot project of a multistage solar thermal water desalination system has been developed, and experimental investigations have been carried out. This paper presents the results of the testing of the system under laboratory conditions. The results show that the productivity of the developed system is two times higher than that of the conventional solar distillers of the greenhouse type. The text was submitted by the authors in English.     

Feasibility study of a solar water pumping system

Solar photovoltaic (SPV) water pumping systems have the potential to provide clean drinking water to millions of unserved people around the world. The abundant solar energy resource and groundwater availability in the Pacific Island Countries (PICs) can be combined to make much needed potable water available to remote island communities in these countries. This paper looks at the feasibility of using a SPV pumping system in one of the villages in the Fiji Islands.     

Experimental and numerical study of thermal stratification in a mantle tank of a solar domestic hot water system

The simulation and the optimisation of the mantle tank of solar domestic hot water systems needs dynamic simulation over long periods of time (e.g. 1 year). A model for such a mantle tank was developed by using the zonal approach. The dimensions of the zones are determined based on physical considerations. A mixing coefficient is identified to model the water flow in the mantle heat exchanger. Comparisons of the results of temperatures distribution of the model and of experiments show a difference <7% for three positions of the inlet water flow in the mantle heat exchanger.     

A new heat-pipe type solar domestic hot water system

The performance of a new solar hot water system with an integrated heat-pipe is investigated theoretically and experimentally. The new system uses a wickless gravity assisted loop heat-pipe for the heat transfer from the collector–evaporator to the tank through a heat exchanger–condenser. A detailed heat transfer experimental study is performed, focused on the thermal behaviour of the different parts of the system. The results show that the system can reach satisfactory efficiencies which, in combination with manufacturing simplicity, absence of moving parts and good behaviour under freeze conditions, make it an interesting technological solution. Furthermore, a theoretical model for the collector is proposed and comparison with experimental results is performed. This model can be used for the optimisation of the system design.     

Parametric model of solar cooker performance

This paper presents a model for prediction of the cooking power of a solar cooker based on three controlled parameters (solar intercept area, overall heat loss coefficient, and absorber plate thermal conductivity) and three uncontrolled variables (insolation, temperature difference, and load distribution). The model basis is a fundamental energy balance equation. Coefficients for each term in the model were determined by regression analysis of experimental data. The model was validated for commercially available solar cookers of both the box and concentrating types. The valid range of model application includes most of the feasible design space for family-sized solar cookers. The model can be used to estimate the cooking capacity of existing box type and concentrating type solar cookers. It can also be used to find the combinations of intercept area and heat loss coefficient required to cook a given quantity of food in a given climate.     

太阳能热水系统蓄热水箱技术的研究进展

蓄热水箱是太阳能热水系统的重要组成部分,蓄热水箱技术对系统的性能具有明显的影响。文章分析了太阳能热水系统蓄热水箱技术的发展,阐述了太阳能热水系统蓄热的主要形式、不同工作阶段的过程和特点以及蓄热水箱的理论和技术的研究进展。     

Thermal analysis and performance optimization of a solar hot water plant with economic evaluation

The main objective of this study is to optimize the long-term performance of an existing active-indirect solar hot water plant (SHWP), which supplies hot water at 65 °C for use in a flight kitchen, using a micro genetic algorithm in conjunction with a relatively detailed model of each component in the plant and solar radiation model based on the measured data. The performance of SHWP at Changi International Airport Services (CIASs), Singapore, is studied for better payback period using the monthly average hourly diffuse and beam radiations and ambient temperature data. The data input for solar radiation model is obtained from the Singapore Meteorological Service (SMS), and these data have been compared with long-term average data of NASA (surface meteorology and solar energy or SSE). The comparison shows a good agreement between the predicted and measured hourly-averaged, horizontal global radiation.The SHWP at CIAS, which comprises 1200 m² of evacuated-tube collectors, 50 m³ water storage tanks and a gas-fired auxiliary boiler, is first analyzed using a baseline configuration, i.e., (i) the local solar insolation input, (ii) a coolant flow rate through the headers of collector based on ASHRAE standards, (iii) a thermal load demand pattern amounting to 100 m³/day, and (iv) the augmentation of water temperature by auxiliary when the supply temperature from solar tank drops below the set point. A comparison between the baseline configuration and the measured performance of CIAS plant gives reasonably good validation of the simulation code. Optimization is further carried out for the following parameters, namely; (i) total collector area of the plant, (ii) storage volume, and (iii) three daily thermal demands. These studies are performed for both the CIAS plant and a slightly modified plant where the hot water supply to the load is adjusted constant at times when the water temperature from tank may exceed the set temperature. It is found that the latter configuration has better thermal and economic performances over the conventional design.