International policy issues regarding solar water heating, with a focus on New Zealand

Like many countries New Zealand is moving towards renewable energy targets and has recently (November 2006) announced a revised solar hot water heating subsidy program that is being implemented through the Energy Efficiency and Conservation Authority (EECA). This paper describes the new program and reviews international policies regarding solar water heating to see which aspects have been effective in gaining an increased penetration of solar systems for water heating. In addition, the factors leading to successful policy implementation and the possible downsides of the 2006 New Zealand policy are discussed with regard to international experience.     

环境条件对全玻璃真空太阳能热水系统热性能的影响

对同一太阳能热水系统在不同环境条件下得热量和热损的多次试验,计算了系统标准单位轮廓采光面积的日有用得热量和平均热损因数,并分析了太阳辐射量、环境风速和温度对系统得热量和热损的影响规律。     

家用太阳热水系统标准探讨

家用太阳热水系统性能检测的国家标准主要有GB/T 18708-2002、GB/T 19141-2003,因测试目的不同,两个标准之间以及与其他各相关标准之间存在一些差异,针对热性能测量系数对各相关的国内外标准进行对比分析,对家用太阳热水系统某些参数测量提出改进建议。     

Design of a solar water heating system for Alexandria, Egypt

The purpose of this work is two-fold. First, to introduce a comparison between steady state and dynamic test methods for two different collectors. Second, to design a solar water heating system to satisfy both hot water and space heating demands for a multi-family house in Alexandria, Egypt.     

Evaluation of a household solar water heating system rating procedure using a reference system for performance comparison

For some time there has been a need for a standard to cover the testing and performance of solar water heating systems. This paper describes a proposed method of performance testing and rating these systems. The method considered is to test the complete system rather than the individual components. The rationale behind this decision is discussed, the test philosophy and a proposed method is presented and the dimensionless rating factors defined and described. The validity of the test procedure and some of the assumptions made have been tested with a mathematical model of the proposed test procedure and sequence using typical Australian conditions. The results of an experimental investigation are presented.     

Modelling and performance of a copolymer solar water heating collector

The performance of a solar flat-plate thermal collector wholly manufactured in a copolymer material is studied. The influence of different parameters of the system such as the insulation thickness, the flow rate and the fluid layer thickness is analysed. Thermal performance, productivity and efficiency of such a solar system is presented for a Mediterranean site. Yearly mean efficiencies are about 56.5% in no wind and about 49.0% for a wind speed of 5 m s⁻¹. The use of polymer materials reduces the collector weight by 50% in comparison with a traditional metal collector, this renders easier installation.     

A new version of a solar water heating system coupled with a solar water pump

This research target was to improve the thermal efficiency of a solar water heating system (SWHS) coupled with a built-in solar water pump. The designed system consists of 1.58-m² flat plate solar collectors, an overhead tank placed at the top level, the larger water storage tank without a heat exchanger at the lower level, and a one-way valve for water circulation control. The discharge heads of 1 and 2 m were tested. The pump could operate at the collector temperature of about 70–90 °C and vapor gage pressure of 10–18 kPa. It was found that water circulation within the SWHS ranged between 15 and 65 l/d depending upon solar intensity and discharge head. Moreover, the max water temperature in the storage tank is around 59 °C. The max daily pump efficiency is about 0.0017%. The SWHS could have max daily thermal efficiency of about 21%. It is concluded that the thermal efficiency was successfully improved, except for the pump one. The new SWHS with 1 m discharge head or lower is suitable for residential use. It adds less weight to a building roof and saves electrical energy for a circulation pump. It has lower cost compared to a domestic SWHS.     

Transient performance of closed loop solar water heating system with heat exchanger

The present paper deals with an analysis of a forced circulation closed loop solar water heating system; withdrawal of hot water of constant flow rate from a storage tank through a heat exchanger is considered. The effect of flow rate and heat exchanger length on the performance has also been discussed for a typical set of parameters and for a typical cold day in Delhi (26 January 1980).     

太阳能集中供热水系统的经济评价

以某酒店为例,介绍了太阳能集中供热水系统的经济评价。通过节能计算得出使用该系统比原有燃油锅炉每年税后节省111 648元。文章还对该太阳能集中供热水系统的净现值、回收期、内含报酬率等方面进行了财务评价。研究表明,该企业使用太阳能集中供热水系统能够带来显著的经济效益。     

架空构架式太阳热水器系统

分析了当前太阳热水器和住宅建筑结合的现状,指出太阳热水器在住宅建筑上应用的限制因素;针对所存在的问题,提出了太阳热水器与住宅建筑结合的一种方式--"架空构架式".它和建筑一体化结合,构造、施工简单,对屋面使用没有影响,经济性好.因此必将成为今后高层住宅建筑太阳能一体化的发展趋势.     

太阳能热水系统的应用研究

文中列举了南京市若干太阳能热水系统与建筑一体化工程概况,建议集体单位大力推广应用太阳能集中热水系统;对居民小区住宅,适合分户使用太阳能热水系统,不宜应用太阳能集中热水系统。     

An electrical analog of a flat-plate solar water heating system

An electrical analog model, derived from the energy balance equations, is presented for the flat-plate solar water heating system. Measurements on the model are in good agreement with experimentally obtained and theoretical values.     

A novel thermal water pump for circulating water in a solar water heating system

This research purpose was to perform a parametric study of a novel thermal water pump well fitted in a simulated solar water heating system (SWHS). The SWHS was composed of a heating tank (HT), a hot water storage tank (ST) and an overhead tank (OT). The HT together with a specially designed valve act as a novel thermal water pump that gets power from hot water vapor and air pressure produced by a built-in electric heater in order to transfer heat from the HT to ST. The general operation of this pump has four stages for each cycle: heating, water circulating, vapor circulating and water supplying. The discharge water heads were varied with an increment of 0.25 m from 0.75 to 3 m. According to the experiment, it was found that the pump could operate at an average HT temperature of about 80–95 °C leading to 70–80 °C ST temperatures and 20–35 pumping cycles and consumed 17 MJ energy input during 9-h period. The overall thermal efficiency of the SWHS was 33–42% and the mean pump efficiency was about 0.005–0.011% depending upon the discharge heads.     

射频控制在太阳能热水系统中的应用

一引言 射频(Radio Frequency)是一种高频交流变化电磁波的简称.它采用一种扩展窄带信号频谱的数字编码技术,通过编码运算增加了发送比特的数量,扩大了使用的带宽,使得带宽上信号的功率谱密度降低,从而大大提高了系统抗电磁、串话干扰的能力,使得无线数据传输更加可靠.     

Optimisation of minimum backup solar water heating system

Current flat plate solar water heaters overproduce slightly in summer and have poor performance in winter at the time of maximum load. They use an expensive absorber plate over the entire absorbing aperture of the collector and fail to use the backside of the absorber. They often have under insulated tanks and are not optimised as integrated systems. This paper describes a design approach taken to use existing commercial flat plate absorber and tank components in a new way to maximise solar contribution and minimise material usage in the construction of the system. The design criterion used is not maximum peak efficiency, but minimum annual backup energy supplied to the system to meet an annual load. This corresponds to meeting a minimum greenhouse emissions requirement in both invested pollution during manufacture and pollution from backup energy supplied. Two new designs are shown which allow the solar fraction of systems to be increased to approximately 80–90% in Sydney Australia using a standard model of domestic hot water usage specified in Australian Standard AS4234. Pollution from fuel use drops to as little as 40% of that of conventional flat plate solar water heaters. These new designs use one absorber plate instead of two and a smaller and better insulated tank. Comparisons of solar fraction are evaluated for a range of climatic conditions. An important insight is that with such a performance optimised system the ultimate solar fraction is limited by occasional long duration cloud cover at the site of installation and making the system larger only increases dumped energy, not utilisable energy. Technical efficiency improvements only reduce the required collector area. However, some additional backup fuel reductions can be made through manual control of backup energy use, because this allows finer control of backup relative to real demand. Pollution from backup fuel usage may be able to be reduced to 1/4 that of current flat plate solar water heaters.     

高太阳能保证率的太阳能热水系统

介绍了一种高效节能的太阳能热水系统,并分析了该系统的工作原理.本系统的设计核心是提高太阳能热水系统的太阳能保证率,及与常规热水器相比节能率fr.     

浅谈分体式太阳能热水系统

一引言 随着<可再生能源法>、<可再生能源中长期发展规划>等政策、法规的出台,我国的太阳能产业取得了快速的发展,成为当前建设节约型社会节能减排活动的排头兵.随着技术不断升级,我国的太阳能产业真正作为一个崭新的行业展现在公众面前.太阳能产业是我国为数不多的拥有自主知识产权的产业,近年来国际市场拓展逐渐加快,社会的关注度与公众的认知度逐步提高,基本形成了比较完善的产业体系.     

Theoretical investigation of the performance of a novel loop heat pipe solar water heating system for use in Beijing,China

A novel loop heat pipe (LHP) solar water heating system for typical apartment buildings in Beijing was designed to enable effective collection of solar heat, distance transport, and efficient conversion of solar heat into hot water. Taking consideration of the heat balances occurring in various parts of the loop, such as the solar absorber, heat pipe loop, heat exchanger and storage tank, a computer model was developed to investigate the thermal performance of the system. With the specified system structure, the efficiency of the solar system was found to be a function of its operational characteristics - working temperature of the loop heat pipe, water flow rate across the heat exchanger, and external parameters, including ambient temperature, temperature of water across the exchanger and solar radiation. The relationship between the efficiency of the system and these parameters was established, analysed and discussed in detail. The study suggested that the loop heat pipe should be operated at around 72 °C and the water across the heat exchanger should be maintained at 5.1 l/min. Any variation in system structure, i.e., glazing cover and height difference between the absorber and heat exchanger, would lead to different system performance. The glazing covers could be made using either borosilicate or polycarbonate, but borosilicate is to be preferred as it performs better and achieves higher efficiency at higher temperature operation. The height difference between the absorber and heat exchanger in the design was 1.9 m which is an adequate distance causing no constraint to heat pipe heat transfer. These simulation results were validated with the primary testing results.     

Calculation of long term solar collector heating system performance

A calculation of system performance is necessary for an economic analysis of solar space heating systems, but is made difficult by the complexity of the system and weather parameters. The system studies in the literature have in general employed detailed computer analyses which, although informative, require detailed weather records and tend to be costly in computer time. To overcome these difficulties, a simplified technique to predict yearly system performance was developed. This simplified method is based on a computation of the system performance for a single “average” day of each month, modifying this result with a correction factor, and summing the results over each month of the heating season. The result is that system performance can be calculated easily, by hand or with trivial computer cost. A comparison with detailed numerical analyses in the literature for systems in the cities of Phoenix, Charleston, Madison and Boston shows excellent agreement. Results are also presented for systems in Salt Lake City.