直膨式太阳能热泵运行特性的实验研究

对直接膨胀式太阳能热泵热水系统进行了实验研究,实验期间,太阳能辐照度变化范围为143.12~664.6 W/m2,分别采用三种不同结构的集热器和蒸发器,得出系统COP为2.49~3.47,表明该系统在各种天气情况下均能够可靠地生产45℃的生活热水,热性能稳定,可以全天候地提供生活热水且具有节能效果;同时选取双集热器的两组数据,分析了太阳辐照度对热泵系统运行的影响。     

太阳能-热泵辅助加热热水系统运行的经济性分析

通过建立太阳能集热设备和水箱温度模型,模拟仿真太阳能-空气源热泵辅助加热热水系统的系统性能。并以南京地区家用热水器全年供热水为例,对三种供热水系统的经济性能进行比较分析,从而得出采用太阳能-空气源热泵辅助加热供热水系统具有良好的经济效益。     

燃气机热泵冷热电三联供系统热经济学分析

采用热经济学分析法对一台燃气机热泵冷热电三联供系统进行分析,对不同转速,蒸发温度,冷凝温度和天然气价格4项影响因素条件下,子系统火用成本差、火用经济因子和总系统的火用经济系数的计算分析,指出了燃气机热泵冷热电三联供系统需要改进之处,针对燃气机热泵冷热电三联供系统的设计需要注意传动比的合理设置问题,并且得出了燃气机热泵冷热电三联供系统在中国具有广阔的应用空间的结论.     

太阳热水系统与燃油(燃气)炉联合供热

用电加热器作为家用太阳热水器的辅助加热装置 ,比较简单、方便。但对于大型太阳热水系统 ,采用燃油（燃气）炉作为辅助加热装置 ,则比较经济。例如 :一台每小时能产１吨热水的燃油炉 ,每小时耗油４ｋｇ ,市价８元不到 ;若改为电热管加热 ,电费需４７元。采用燃油（燃气）炉或电加热的定时用水单位 ,都能实现定时起动和停运 ,可进一步节约能源。针对２４小时用热水的单位（如宾馆酒店类） ,可另设一个较小的的恒温水箱 ,与燃油炉并列循环 ,其恒温箱的水源取自太阳热水器 ,这样既能保证２４小时有热水供应 ,同时也能保证太阳热水器的正常工作…     

太阳能热水系统与高层住宅一体化结合的运行方式

随着高层住宅越来越多的建立,太阳能热水器的适用问题也愈发突出.针对高层住宅应用太阳能热水系统的一些特点,总结了三种现有的运行方式,即集中式、集中—分散式和分散式,并分别从系统构造、布置、运行特点等几方面进行分析比较.最后结合我国现状阐述太阳能热水系统在高层住宅中的实际运用情况,并提出相应建议.     

用热泵作被动式太阳房辅助热源的研究

北方寒冷地区，农村直接受益式被动式太阳房在采暖季节室内温度较低，舒适性差。本研究采用热泵辅助供暖的方式对被动式太阳房在采暖季节进行供暖实验。通过与煤炉、电加热器、分散式锅炉供暖的比较，验证了该方法的可行性。同时对热泵供暖进行优化，找出影响热泵供暖性能及年成本价格的因素，并对其在小城镇的推广做了分析。结果表明，热泵作为被动式太阳房在北方寒冷地区及电力充沛而集中供暖有困难地区的辅助热源是可行的。     

一种新型太阳能辅助高温热泵系统性能分析

为降低压缩机排气温度、优化热泵系统性能,设计了 一种利用太阳能集热器加热压缩机排气,利用蒸气显热制取高温热水的新型太阳能辅助热泵系统.结合天津地区的辐射日照条件对新型太阳能辅助热泵系统进行了可行性和热力性能分析,并将其与直膨式太阳能辅助热泵系统的性能进行对比.结果表明:该系统通过提高蒸发温度,可以降低制冷压缩机排气温度...     

公共浴室热泵热水系统加热模式研究

从实际工程应用的角度出发,提出了用洗浴废水作为低温热源的4种热泵热水系统的换热方案,并针对循环加热和一次加热共2种不同加热模式下的热泵热水系统进行了研究,分别对其无预热和有预热系统的技术经济性进行了分析。     

热泵辅助太阳能中央热水系统年运行特性研究

提出采用热泵来取代传统的电加热器,构成热泵辅助太阳能中央热水系统,可有效地降低能源消耗.结合2005年西安地区气象数据,建立了合适的数学模型,并用现有的试验数据对模型进行了校准,通过模型模拟了该年热泵辅助和电辅助太阳能中央热水系统的性能系数,输入功耗,出水温度等运行参数,并对两者进行了对比.     

太阳能热水系统辅助热泵加热容量计算方法探讨

太阳能热水系统设计中热泵的加热容量是热泵选型及水箱设计的关键参数,但是其计算方法目前未见有文献报道。本文基于单水箱太阳能热水系统,分析了在连续阴雨天气下只有热泵供热时水箱的温度分布,提出了热泵加热容量的计算方法。通过该方法计算得到某太阳能热水系统热泵加热容量,并计算了与平均小时耗热量的比值。对于一般热泵辅助太阳能热水系统,按储热区相对高度0.20~0.25、热泵最大日运行时间8 h设计比较合适。     

Performance and economics of annual storage solar heating systems

Annual storage is used with active solar heating systems to permit storage of summer-time solar heat for winter use. This paper presents the results of a comprehensive computer simulation study of the performance of active solar heating systems with long-term hot water storage. A unique feature of this study is the investigation of systems used to supply backup heat to passive solar and energy-conserving buildings, as well as to meet standard heating and hot water loads.

Findings show that system performance increases linearly as storage volume increases, up to the point where the storage tank is large enough to store all heat collected in summer. This point, the point of “unconstrained operation”, is the likely economic optimum. In contrast to diurnal storage systems, systems with annual storage show only slightly diminishing returns as system size increases. Annual storage systems providing nearly 100% solar space heat may cost the same or less per unit heat delivered as a 50 per cent diurnal solar system. Also in contrast to diurnal systems, annual storage systems perform efficiently in meeting the load of a passive or energy-efficient building. A breakeven cost 4¢–10¢/kWh is estimated for optimal 100 per cent solar heating in the U.S.A.     

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.     

Experimental characterisation of a novel heat exchanger for a solar hot water application under indoor and outdoor conditions

The performance of a novel heat exchanger unit (‘Solasyphon’) developed for a solar hot water system was experimentally investigated under indoor and outdoor operating conditions. The ‘Solasyphon’ can be easily integrated to an existing single-coil hot water cylinder avoiding the need for costly twin-coil solar hot water storage. A series of tests were conducted under controlled indoor and real outdoor conditions to test and compare the performance of the ‘Solasyphon’ system with a traditional twin-coil (‘coil’) system. The analysis was based upon experimental data collected under various operating conditions including different primary supply temperatures (solar simulated); heating from ambient, heating with a partially stratified storage from ambient and finally under no draw-off and standard draw-off patterns. The outdoor testing was carried out on both systems separately over Summer/Autumn conditions in Northern Ireland. The results showed that the ‘Solasyphon’ system is more effective compared to a traditional twin-coil system for a domestic application where intermittent hot water demand is predominant and under a transient solar input particularly on intermediate or poor solar days. The ‘Solasyphon’ delivered solar heated water directly to the top of the storage producing a stratified supply at a useable temperature. The twin-coil system was found to be more efficient than the ‘Solasyphon’ system under a prolonged heating period.     

太阳热水系统节能量计算方法探讨

针对太阳辐照量、用户热水用量随时间段变化的情况,提出了分时间段计算的用户全年热水需能量、太阳热水系统年产能量计算公式及太阳热水系统年节能量与节能率的计算公式,还提出了用太阳热水系统利用率来优化太阳热水系统的设计方法,有助于设计一个合理、高效的太阳热水系统,提高太阳热水系统的利用率及减少投资回收期.该计算方法也可供其他可...     

Thermosiphon solar domestic water heating systems: long-term performance prediction using artificial neural networks

The objective of this work is to use artificial neural networks (ANN) for the long-term performance prediction of thermosiphonic type solar domestic water heating (SDWH) systems. Thirty SDWH systems have been tested and modelled according to the procedures outlined in the standard ISO 9459-2 at three locations in Greece. From these, data from 27 of the systems were used for training and testing the network while data from the remaining three were used for validation. Two ANNs have been trained using the monthly data produced by the modeling program supplied with the standard ISO 9459-2. Different networks were used depending on the nature of the required output, which is different in each case. The first network was trained to estimate the solar energy output of the system for a draw-off quantity equal to the storage tank capacity (at the end of the solar energy collection period) and the second one was trained to estimate the solar energy output of the system and the average quantity of hot water per month at demand temperatures of 35 and 40°C. The collector areas of the considered systems were varying between 1.81 m² and 4.38 m². Open and closed thermosiphonic systems have been considered both with horizontal and vertical storage tanks. In this way the networks were trained to accept and handle a number of unusual cases. The input data in both networks are similar to the ones used in the program supplied with the standard. These were the size and performance characteristics of each system and various climatic data. In the second network the demand temperature was also used as input. For the first network the statistical coefficient of multiple determination (R²-value) obtained for the training data set was equal to 0.9993. For the second network the R²-value for the two output parameters was equal to 0.9848 and 0.9926, respectively. Unknown data were subsequently used to investigate the accuracy of prediction and R²-values equal to 0.9913 for the first network and 0.9733 and 0.9940 for the second were obtained. These results indicate that the proposed method can successfully be used for the prediction of the solar energy output of the system for a draw-off equal to the volume of the storage tank or for the solar energy output of the system and the average quantity of the hot water per month for the two demand water temperatures considered.     

Dimensioning of the solar heating system in the zero energy house in Denmark

The paper describes the project for a Zero Energy House constructed at the Technical University of Denmark. The house is designed and constructed in such a way that it can be heated all winter without any “artificial” energy supply, the main source being solar energy. With energy conservation arrangements, such as high-insulated constructions (30–40 cm mineral wool insulation), movable insulation of the windows and heat recovery in the ventilating system, the total heat requirement for space heating is calculated to 2300 kWh per year. For a typical, well insulated, one-storied, one-family house built in Denmark, the corresponding heat requirement is 20,000 kWh. The solar heating system is dimensioned to cover the heat requirements and the hot water supply for the Zero Energy House during the whole year on the basis of the weather data in the “Reference Year”. The solar heating system consists of a 42 m² flat-plate solar collector, a 30 m³ water storage tank (insulated with 60 cm of mineral wool), and a heat distribution system. A total heat balance is set up for the system and solved for each day of the “Reference Year”. Collected and accumulated solar energy in the system is about 7300 kWh per yr; 30 per cent of the collected energy is used for space heating, 30 per cent for hot water supply, and 40 per cent is heat loss from the accumulator tank. For the operation of the solar heating system, the pumps and valves need a conventional electric energy supply of 230 kWh per year (corresponding to 5 per cent of the useful solar energy).     

Preliminary performance of CSU Solar House I heating and cooling system

The NSF/CSU Solar House I solar heating and cooling system became operational on 1 July 1974. During the first months of operation the emphasis was placed on adjustment, “tuning”, and fault correction in the solar collection and the solar/fuel/cooling subsystems. Following this initial check out period, analysis and testing of the system utilizing a full year of data was begun. This paper discusses the preliminary performance of the heating and cooling system.

During the period 1 August 1974–31 January 1975, approximately 40 per cent of the cooling load was provided by solar energy. Solar heating over the same period of time provided 86 per cent of the space heating load and 68 per cent of the domestic hot water heating load. These percentages represent a total solar contribution of 33,996 MJ delivered to load (8061 MJ to the cooling unit; 20,687 MJ to heating; 5248 MJ to hot water). Natural gas accounted for 22,442 MJ, total. In addition, preliminary analysis has provided several significant results associated with the operating characteristics of the solar system and the individual components.     

Performance of commercially available solar and heat pump water heaters

Many countries are using policy incentives to encourage the adoption of energy-efficient hot water heating as a means of reducing greenhouse gas emissions. Such policies rely heavily on assumed performance factors for such systems. In-situ performance data for solar and heat pump hot water systems, however, are not copious in the literature. Otago University has been testing some systems available in New Zealand for a number of years. The results obtained are compared to international studies of in-situ performance of solar hot water systems and heat pump hot water systems, by converting the results from the international studies into a single index suitable for both solar and heat pump systems (COP). Variability in the international data is investigated as well as comparisons to model results. The conclusions suggest that there is not too much difference in performance between solar systems that have a permanently connected electric boost backup and heat pump systems over a wide range of environmental temperatures. The energy payback time was also calculated for electric boost solar flat plate systems as a function of both COP and hot water usage for a given value of embodied energy. The calculations generally bode well for solar systems but ensuring adequate system performance is paramount. In addition, such systems generally favour high usage rates to obtain good energy payback times.     

Comparative study of various optimization criteria for SDHWS and a suggestion for a new global evaluation

This study compares various optimization criteria for a solar domestic hot water system (SDHWS). First of all, we present the various parameters used to evaluate a SDHWS. We consider the energetic, exergetic, environmental (CO₂ emissions) and financial (life cycle cost) analysis. Various optimization criteria of a standard solar hot water system are then proposed. The optimized solutions are compared with a standard hot water system. The most suitable criteria take into account both energetic (therefore environmental) and financial evaluations. The most powerful solutions tend to increase the collector area - increasing the solar fraction during the mid-season - and reduce the tank volume, thereby decreasing the thermal losses and financial cost.Some of the usual evaluation criteria for SDHWs cannot be used as optimization criteria because they do not consider the auxiliary heater, resulting in inaccurate indications of the system’s performance. Therefore, it seemed important to propose a new evaluation method which integrates the life cycle savings, primary energy savings and CO₂ emission savings with regard to a referenced solution based on a radar diagram of these three fractions. This mode of representation is particularly useful when various auxiliary heaters are compared.     

A Markov model of solar energy space and hot water heating systems

This paper presents a Markov model approach to the generalized solar energy space heating performance analysis problem. Specifically, Markov chain models are developed to represent ambient temperature, insolation, hot water load and system performance. From the Markov transition probability matrices for these variables, long-term expected performance is calculated. The theoretical development is implemented in FORTRAN IV on a Control Data 6400 Computer System. Computational experience gained, using STOLAR 3.1 (STOchastic soLAR energy systems model), indicates the stochastic approach requires approximately five per cent of the time necessary for standard dynamic simulation approaches with comparable performance results. The method also compared favorably with FCHART, a simplified design procedure.