A review of materials for solar heating systems for domestic hot water

This paper reviews the fitness-for-purpose of commonly used materials and possible alternative materials for all components of solar heating systems for domestic hot water. Optimum materials are recommended where possible. A conclusion of the survey of materials which has been carried out is that, using current technology, reliable, durable solar heating systems can be built. The cost of such systems is high, due to the use of expensive materials (such as copper and stainless steel) and the systems are unlikely to be cost-effective in the long term. Costs can be reduced by the use of lower cost materials such as the polymerics for many of the components, but as yet there are insufficient materials performance data to ensure long-term reliability.     

Determination of design space and optimization of solar water heating systems

In this paper, a methodology is proposed to determine the design space for synthesis, analysis, and optimization of solar water heating systems. The proposed methodology incorporates different design constraints to identify all possible designs or a design space on a collector area vs. storage volume diagram. The design space is represented by tracing constant solar fraction lines on a collector area vs. storage volume diagram. It has been observed that there exists a minimum as well as a maximum storage volume for a given solar fraction and collector area. Similarly existence of a minimum and a maximum collector area is also observed for a fixed solar fraction and storage volume. For multi-objective optimization, a Pareto optimal region is also identified. Based on the identified design space, the solar water heating system is optimized by minimizing annual life cycle cost. Due to uncertainty in solar insolation, system parameters and cost data, global optimization may not be utilized to represent a meaningful design. To overcome this, a region of possible design configurations is also identified in this paper.     

低能耗建筑太阳能采暖热水系统实例设计分析(下)

4 太阳能采暖系统的确定 太阳能采暖系统均为强制循环方式,包含集热器阵列、水箱、循环泵站、控制系统、过热保护等.不同水箱的方式决定了太阳能系统的不同形式及控制模式.在Tsol模拟软件的系统模式中,提供了多达24种方式.本设计主要根据Tsol模拟系统来确定实际运行系统.     

低能耗建筑太阳能采暖热水系统实例设计分析(上)

一引言 由于太阳能供暖技术复杂,初投资较大,在我国仅处于起步阶段.虽然国内一些研究机构根据国外的研究结果,结合我国实际实施了一些太阳能采暖示范工程,取得了一些经验及数据,国家也在着手准备太阳能采暖方面的国家技术规范,但目前为止还很难看到比较系统的数据资料供广大设计人员参考.因此,笔者通过对一栋节能建筑的太阳能采暖工程设计参考的国内外技术资料进行总结,以供大家参考.     

A simplified approach to economic analysis of solar heating and hot water systems and conservation measures

Using a new manipulation of standard relationships, the economic optimization and analysis of solar heating and hot water systems has been simplified. A payback ratio is defined as the reciprocal of the capital recovery factor and used to calculate the minimum or marginal annual thermal return per unit area acceptable for the system. Selecting the point at which the slope of a plot of solar fraction versus area (expressed as area per unit annual demand) equals the marginal annual thermal return per unit area optimizes the system. The ratio of coordinates at that point is the overall annual thermal return per unit collector area. This may be easily transformed into the return on investment, net worth, and payback time of the system. A new equivalent life-cycle payback time is defined that is derived from life-cycle analysis.The analysis is then extended to optimization of conservation measures. A closed formula for optimal insulation thickness is developed and illustrated.     

Economic evaluation and optimization of solar systems for space and domestic water heating

Solar energy will be utilized only if it proves to be economical. In this paper, we evaluate the economic feasibility of the use of solar energy for space and domestic water heating systems for a house in Benghazi, Libya. A comprehensive evaluation considerering 324 cases representing the proper ranges of economic and load factors and based on the annual equivalent cost approach is given. The optimum collector area for each case is determined. The results obtained and relationships developed permit generalizations that can be applicable in other locations.     

Validation of a computer model for solar assisted district heating systems with seasonal hot water heat store

The TRNSYS XST-model for the calculation of the thermal behaviour of ground buried hot water heat stores was validated. For the validation procedure measured data of the seasonal hot water heat store in Hannover (Germany) were used. In contrast to previous investigations the temperatures of the surrounding ground were also taken into consideration. The determination of the heat store parameters was carried out using TRNSYS in combination with the parameter identification software DF. The deviation between measured and calculated temperatures is less than ±3%. The measured and calculated heat quantities are also in good agreement (annual deviation less than 2%). The validated XST-model was integrated into a TRNSYS model to calculate the thermal behaviour of the solar assisted district heating system in Hannover in 2002. The deviations between measured and calculated heat quantities do not exceed 5%.     

Load optimization in solar space heating systems

When load variables, such as window and insulation types, are included in the economic optimization of a solar space heating system, the over-all cost is lower than that resulting from optimization of collection area for a fixed load (as by FCHART [1] and SOLCOST [2]). In this paper an algorithm is derived for choosing insulation levels, as well as solar collection area, so as to minimize the over-all cost of constructing and heating a building. The general algorithm is applicable with any solar performance prediction method, and with any economic criterion where the “cost” is a linear function of collection area and of auxiliary energy consumption. A specific algorithm is also derived for active solar systems using the Relative Areas method of performance prediction [3] and a conventional present worth life cycle cost analysis. The degree-day model is used for the load calculations.     

Incentives for solar water heating systems

Life-cycle costing has been used in an economic analysis of three solar domestic hot water installations. These are in operation in Las Palmas (Canary Islands) and are backed by conventional installations consuming either fuel-oil (GG), butane (BB) or electricity (EE). The cumulative cost flows (CCF), including expenditures for purchase, recovery, maintenance, fuel and operating costs, are calculated over the useful life of the installations for expected annual fuel-increment rates. Twenty-seven comparisons are made between the solar (SAS) and conventional systems (CS). Total savings are found over the lifetime and the repayment periods are obtained as a function of discount rate. The SAS and CS are examined with respect to economic incentives such as subvention, tax deduction, loans and their combinations. Finally, the variations of the payback periods and rates of return on investment (IRR) are plotted against the fuel price, annual fuel increment rate and initial investment in the SAS for a wide range of economic parameters.     

家用太阳能热水系统能效标准制定工作正式启动

在我国太阳能热水器产业蓬勃发展的今天,在繁荣的背后,太阳能热水器产品鱼龙混杂,市场秩序混乱是不争的事实.在新的形势,如何促进产业健康发展,如何促进产业升级?成为业内外人士关心的大问题.标准化工作是推动产业升级和健康发展的重要手段.     

太阳能热水系统技术方案

图1凡是使用过接触过或关注过太阳热水器(或系统)的人都会得出这样的认识:尽管太阳热水器有着其它热水器(油、电、气)无可比拟的节能、环保、安全等优点,但它也确实存在着其它热水器所不存在的令人头疼的难题,诸如:防冻、抗冻问题;一年四季24小时供应热水问题;与建筑物有机结合问题以及恒温,恒压出水问题。这些问题中任何一个问题的根本解决,都会对太阳能热利用起到很大的推动作用。如果能全部加以解决,那将对目前3种热水器的市场格局产生决定性的影响。能不能找到一种技术方案,把这所有的难题一下子全部加以解决呢?通过多年摸索与工程实践,…     

Domestic hot water and solar energy in Ireland

Two systems are discussed which involve the use of solar energy to supply domestic hot-water requirements and their usefulness in Ireland is examined. the systems are evaluated for thermal performance and cost-effectiveness but the use of a computer simulation model of a system involving a typical commercially available solar panel. It is shown that such systems may be economically justified when compared with electricity, but only if the water supply is directly heated by solar panels and only if the installed cost of such panels is low. Further, it appears that the system performance is relatively insensitive to the panel orientation and consequently that retro-fit installations on existing houses are unlikely to cause difficulties.     

家用太阳热水器与太阳热水系统的技术经济比较

分析了户用太阳热水器和太阳热水系统工程的经济技术特点,对两者成本构成、项目财务净现值、投入回收期和财务内部收益率等有关指标进行了经济技术比较.分析比较表明,太阳热水系统与家用热水器相比,节省安装占地,与建筑相结合得好,在降低成本,缩短投资回收期,提高经济效益方面有明显的优势.     

Analysis and optimization of solar hot water systems

Use of a simplified method has been made to calculate the time-dependent thermal performance of various solar domestic hot water systems. to establish the value of solar hot water systems under given economic considerations a thermal analysis was carried out on three basic energy system designs, operating at several locations in the Federal Republic of Germany (F.R.G.) with various solar collectors. It is found that systems design can result in variations up to a factor of two in the per cent solar output. the location and year of operation in the F.R.G. result in variations up to 15 per cent in the solar output. A sensitivity study was also done with respect to all solar collector, systems and user parameters. From this it was found that the dominant effects on the systems performance were due to the collector-dependent parameters.     

太阳能空调热水系统研究分析

前言日益普及并呈加速发展的室内空气调节 ,需要消耗大量电能和化石燃料。常规空调制冷剂ＣＦＣｓ 对大气臭氧层有破坏作用 ,影响环境。因此 ,在空调制冷技术的发展与应用中 ,面临着节电、节能和环保三大问题。当前不用氟氯烃作工质、热驱动的吸收式制冷 ,日益受到人们的重视。太阳能是取之不尽 ,用之不竭 ,可再生的清洁能源。太阳能热水器现已发展到非常成熟的水平 ,它是以获取生活热水为目的的。但这种应用方式与人们的生活需求正相反 ,当夏季太阳辐射强、气温高的时候 ,太阳能热水器产生的热水量最大 ,而此时最需要的是空调降温而不是热…     

也谈全天候太阳能热水系统

何谓“全天候太阳能热水系统”，简单的说就是一年365天、每天24小时，时时都有热水备用的太阳能热水系统及工程。让用户(包括集体用户和家庭用户)再也不用为“现在洗浴有热水吗”而操心。它比过去使用过的“天天有热水”，实际上是天天的某个时段才有热水的承诺有更加明确的概念界限。也让用户遇到阴雨风雪等恶劣天气环境时无后顾之忧。     

A simplified method for optimal design of solar water heating systems based on life-cycle energy analysis

Significant energy mismatch exists in solar water heating systems as the time and amount of solar energy supply are usually different from that of hot water demand. Using a hot water storage tank can reduce or eliminate such mismatch in short term while it is difficult to avoid this mismatch in long term. In many optimal design and life-cycle analysis methods, the energy mismatch is ignored which causes the system performance to be overestimated and also misleads the optimal design of the system. This paper presents a simplified method for optimizing the key parameters of solar water heating systems based on life-cycle energy analysis. This optimal method considering the energy mismatch phenomenon can be implemented through two steps. In the first step, a simplified energy model based hourly energy matching different components of the system, is developed for determining the operating performance of system with different solar collector areas and water storage volumes. In the second step, the law of diminishing marginal utility is employed to determine the optimum size of the system. The optimum size is identified when the maximal life-cycle net energy saving is achieved. A case study on the application of the proposed method in a building is presented as well.     

Technical note Intelligent thermal energy meter cum controller for solar water heating systems

A microcontroller based, thermal energy meter cum controller (TEMC) suitable for solar thermal systems has been developed. It monitors solar radiation, ambient temperature, fluid flow rate, and temperature of fluid at various locations of the system and computes the energy transfer rate. It also controls the operation of the fluid-circulating pump depending on the temperature difference across the solar collector field. The accuracy of energy measurement is ±1.5%. The instrument has been tested in a solar water heating system. Its operation became automatic with savings in electrical energy consumption of pump by 30% on cloudy days.     

Analysis of natural circulation solar water heating systems

This paper presents an analysis of the performance of a solar water heating system with natural thermosyphon circulation between the collector and the storage tank. The analysis is based on the formulation by Ong except that provision for withdrawal of hot water from the tank (for domestic/ industrial use) has been made in the energy balance equation; further in contrast to the use of the finite difference method by Ong, explicit expressions have been obtained. The results of the present analysis (in the absence of withdrawal of hot water from the tank) are seen to be in better agreement with experiments than the corresponding results of Ong, obtained by use of the finite difference method.

Numerical results, corresponding to hot water retrieved from the storage tank, have been presented for two modes of hot water withdrawal viz. the constant flow rate and constant mean storage tank water temperature.     

Reliability of hot water solar systems in Greece

Ten thousand domestic hot water solar systems were surveyed in Greece to assess component and system reliability. Data concerning the functioning condition of the systems was collected, a computerized data base was established and statistical analysis was performed. This work is part of a solar system evaluation program within the European Community. Greece was selected due to the high concentration of solar collector systems and the fact that these systems have reached maturity, the average lifespan being five years.