外文翻譯---改造在寒冷氣候下單戶家庭房屋的太陽能熱水器的生活熱水的分析

1、.附 錄附錄A 外文資料Retrofitting Domestic Hot Water Heaters for Solar Water Heating Systems in Single-Family Houses in a Cold Climate:A Theoretical AnalysisAbstract: One of the biggest obstacles to economic profitability of solar water heating systems is the investment cost. Retrofitting existing domestic h

2、ot water heaters when a new solar hot water system is installed can reduce both the installation and material costs. In this study, retrofitting existing water heaters for solar water heating systems in Swedish single-family houses was theoretically investigated using the TRNSYS software. Simulation

3、 models using forced circulation flow with different system configurations and control strategies were simulated and analysed in the study. A comparison with a standard solar thermal system was also presented based on the annual solar fraction. The simulation results indicate that the retrofitting c

4、onfiguration achieving the highest annual performance consists of a system where the existing tank is used as storage for the solar heat and a smaller tank with a heater is added in series to make sure that the required outlet temperature can be met. An external heat exchanger is used between the co

5、llector circuit and the existing tank. For this retrofitted system an annual solar fraction of 50.5% was achieved. A conventional solar thermal system using a standard solar tank achieves a comparable performance for the same total storage volume, collector area andreference conditions.Keywords: sol

6、ar thermal storage tank water heater retrofit domes;1. IntroductionOne of the biggest obstacles to the economic profitability of domestic solar water heating (SWH) systems is the investment cost . The installation cost of forced circulation systems used in cold climates can represent up to 50% of th

7、e total investment cost depending on the size and type of system . Also, the solar storage is one of the most expensive components in a solar water heating system . Retrofitting existing domestic water heaters when new SWH systems are installed can reduce the total investment cost by decreasing both

8、 the installation and material costs. In Sweden there are more than half a million electrically heated single family houses that use conventional water heaters for domestic hot water production . Such retrofitting needs to be carried out with consideration of the cold Swedish climate. In such region

9、s the solar storage is placed indoors and a freeze protection medium runs inside the collector circuit. Since existing water heaters are not provided with a heat exchanger, an external one should be used. There are two main types of systems designed with an external heat exchanger outside the storag

10、e: thermosyphon and forced flow circulation .Cruickshank and Harrison, in 2004 and 2006 , investigated this type of thermosyphon systems in the Canadian cold climate. In 2011 , the same authors studied the performance of series and parallel connected thermosyphon storages. Thermosyphon systems becam

11、e popular in several parts of the world such as Eastern Asia and Australia, mainly due to their simplicity and reliability . The thermosyphon driving force depends on the pressure difference and frictional losses between the heat exchanger side-arm and the tank. Hence, the generated flow will be a c

12、omplex function of the state of charge of the tank, the temperature profile along the heat exchanger and pipes, the height difference between the top of the heat exchanger and the top of the tank and the pressure drop in the heat exchanger, piping and connections . Such dependence on the heat exchan

13、ger pressure drop and tank characteristics limits how the retrofit is carried out, where the heat exchanger should be placed and which storage tanks can be used . Moreover, when properly designed, forced circulation systems can significantly achieve higher performances compared with natural convecti

14、on driven systems . This is mainly explained by the increase in energy transfer rate at a low energy driving cost. For example, a 40 W pump can generate a driving force 45 times higher than the one achieved by natural convection systems. In addition, low energy pumps are now available at a lower cos

15、t. The disadvantages of forced circulating systems are stated to be a higher degree of complexity and the demand for electricity to run the pumps and controls.Fewer studies are focused on forced circulation systems specially designed for cold regions. Wongsuwan and Kumar concluded that TRNSYS softwa

16、re predicts accurately the performance of forced circulation systems. Buckles and Klein used TRNSYS software to theoretically investigate different system configurations, and concluded that heat exchangers, with the same capacity, have similar performance whether placed inside or outside the storage

17、. In 2009, Hobbi and Siddiqui used TRNSYS to theoretically optimize the design of a forced circulation hot water system for cold climates. As in other studies, the annual solar fraction was used as design parameter to be optimized . Of specific interest is the fact that there is a lack of studies in

18、vestigating the retrofitting of existing water heaters in single-family houses for solar hot water application in cold regions.Retrofitting solar domestic hot water systems today commonly consists on series connecting the existing system with a new solar storage upstream and using the existing hot w

19、ater boiler as a backup heater . Some retrofitted systems make use of thermosyphoning and are therefore dependent on a new well performing storage for that purpose . Existing installations are often oversized in volume since large design loads have been used before and because domestic hot water con

20、sumption has been decreasing . Combined with low levels of insulation, such over sizing causes large system heat losses. When using the existing storages as solar hot water storage the thermal losses in the system can be decreased since the solar water temperature is lower than the backup temperatur

21、e. In cases where it is possible to know when the existing boiler is close to the end of its lifetime, it can be advantageous to change the existing storage.In this research, retrofitting of conventional domestic water heaters using forced circulation SWH systems for single-family houses in the Swed

22、ish climate was theoretically investigated. This was carried out by means of two pumps, one in the tank loop and the other in the solar collector loop with a heat exchanger in between. Four different system configurations were simulated in TRNSYS software and compared based on the annual solar fract

23、ion. Since forced circulation is used, almost any kind of storage tank can be retrofitted when a new solar thermal system is installed. Also, the degree of complexity of forced circulation systems may be reduced with such a retrofit. For a better understanding of the research contribution to the fie

24、ld and to increase the readability of the paper, the main objectives of the study are stated below.To theoretically investigate different system configurations and control strategies in retrofitting conventional domestic water heaters for SWH systems in single-family houses in the Swedish climate.To

25、 compare the performance of the retrofitted systems with the performance of a standard solar thermal system for the same reference conditions.This study provides necessary information to further investigate such systems in practice. It is then necessary to validate the theoretical models and carry o

26、ut a life cycle cost assessment to compare the different systems. Such assessment is based on many factors that vary from country to country and can lead to different conclusions. Outside cold regions free from freezing, an anti-freeze solution and an external heat exchanger are not required. This w

27、ill alter the system configuration, its performance and final costs. Other variable factors are cost of the auxiliary energy, its predicted trend during the system lifetime, the investment cost of the required equipment, the installation cost, maintenance costs, operation costs, replacement costs, s

28、ubsidies, taxes on eventual loans, inflation, chosen discount rate and residual value at the end of the systems lifetime. Also, it is difficult to quantify how much the industrial development on the integration of all retrofitting components into one add-on unit would decrease the cost. In addition,

29、 the space occupied by the introduction of the extra retrofitting material such as pumps, controls and heat exchanger is a qualitative comparison parameter between the systems valued differently by the consumer. These assessments are outside the scope of this work and will be dealt with in a further

30、 stage of the investigation.2. MethodologyDifferent system configurations were analysed using TRNSYS software in order to determine the annual solar fraction. Firstly, the characteristics of existing domestic water tanks in Sweden were determined. Secondly, a domestic hot water load profile represen

31、tative of Swedish single-family houses was created. Lastly, the energy model of each system configuration and sensitivity analysis was described.2.1. Existing Domestic Hot Water Heaters in Swedish Single-Family HousesThe main boundary of this investigation was to retrofit the most common type of exi

32、sting domestic hot water heaters in single family houses in Sweden. To the best of our knowledge, there is no official data concerning the most common tank size in such houses. According to the Swedish domestic water heater manufacturers, installers and researchers in the field, the most common Swed

33、ish single-family house tank size is 200300 litres, depending on the family size. The trend is that higher loads correspond to higher available storage volumes. A sensitivity analysis showed that retrofitting a 300 litre tank would give a higher annual solar fraction than using a 200 litre tank for

34、the same load. Hence, to be on the safe side, it was decided to use a 200 litre tank for the analysis. In most of the cases, the heat is generated by a 3 kW electric auxiliary heater inside the tank.2.2. Domestic Hot Water Load in Swedish Single-Family HousesA profile of the domestic hot water load

35、consumption in Swedish single-family houses was created. The profile consists of seven different draw-offs during the day . This represents a simplification of the hourly profile described by Widén et al. but scaled to the latest data on the Swedish average hot water consumption of 42 litres pe

36、r person per day measured in 44 single-family houses . A sensitivity analysis showed that using a more detailed draw-off profile would have a low impact on the results and would only increase the total computational time. The measured average cold water temperature in the taps was 8.5 °C . The

37、variation in consumption during the year was also introduced based on measured data and is shown in Figure 2. Swedish statistics show that the average number of inhabitants in Swedish single-family houses is three . Hence, assuming that hot water is heated up to 60 °C, the annual domestic hot w

38、ater consumption in these houses was estimated to be 2050 kWh/year. This value is close to previous measured values in single-family houses . This energy amount does not include the extra energy necessary to compensate for the heat losses from the storage and piping system and the energy necessary t

39、o run the circulation pump in the tank loop, if one is installed. These factors were taken into account by the model in calculating the annual solar fraction of every system.From:Energies 2012,5,40110-4231改造在寒冷氣候下單戶家庭房屋的太陽能熱水器的生活熱水的分析摘要：投資成本是太陽能熱水系統(tǒng)的經(jīng)濟(jì)效益的最大障礙之一。改造現(xiàn)有的國(guó)內(nèi)熱水器比一個(gè)新的太陽能熱水系統(tǒng)的安裝，要減少安裝及材料費(fèi)用。在

40、這項(xiàng)研究中使用TRNSYS(Transient System SimulationProgram即瞬時(shí)系統(tǒng)模擬程序)軟件對(duì)瑞典單戶家庭住宅太陽能熱水系統(tǒng)的改造進(jìn)行理論上研究。使用不同的系統(tǒng)配置和控制策略的強(qiáng)制循環(huán)流動(dòng)的仿真模型，模擬和分析研究。在一個(gè)標(biāo)準(zhǔn)比較年太陽能保證率上，還介紹了太陽能光熱系統(tǒng)。仿真結(jié)果表明，加裝配置實(shí)現(xiàn)最高性能的太陽能由太陽集熱和一個(gè)系統(tǒng)組成，這個(gè)系統(tǒng)中現(xiàn)有的罐被用作存儲(chǔ)，較小的罐用加熱器串聯(lián)的加入，以確保所需的出口溫度可以得到滿足。外部熱交換器之間的集電極電路使用現(xiàn)有的罐。對(duì)于這個(gè)改造的系統(tǒng)每年的太陽能保證率達(dá)到50.5。傳統(tǒng)的太陽能光熱系統(tǒng)使用標(biāo)準(zhǔn)的太陽能水箱，相同的

41、總存儲(chǔ)量足以達(dá)到相當(dāng)?shù)男阅堋⒓療崦娣e和參考條件。關(guān)鍵詞：太陽能光熱 儲(chǔ)罐 熱水器 改造 圓頂1、介 紹家用太陽能熱水系統(tǒng)(太陽能熱水器)經(jīng)濟(jì)效益的最大障礙之一是投資成本。強(qiáng)制循環(huán)在寒冷氣候條件下使用的太陽能系統(tǒng)的安裝成本多取決于系統(tǒng)大小和類型投資成本的50。此外，太陽能的存儲(chǔ)是太陽能熱水系統(tǒng)的最昂貴的組件之一。改造現(xiàn)有的家用熱水器，安裝新的太陽能熱水系統(tǒng)的安裝及材料費(fèi)用的降低，可以降低總投資成本。在瑞典，有幾萬電加熱的單家獨(dú)戶的房子使用傳統(tǒng)的熱水器生產(chǎn)生活熱水。要進(jìn)行這樣的改造需要考慮的冷瑞典氣候。在這些地區(qū)的太陽能儲(chǔ)存放置在室內(nèi)，集熱器內(nèi)的電路運(yùn)行有防凍保護(hù)介質(zhì)。由于現(xiàn)有的熱水器不設(shè)置一個(gè)熱

42、交換器，所以要使用一個(gè)額外的熱交換器。主要有兩種類型的系統(tǒng)之外的存儲(chǔ)與外置式換熱器設(shè)計(jì)：熱管和強(qiáng)制對(duì)流循環(huán)。在2004和2006年，Cruickshank和Harrison,在加拿大寒冷的氣候?qū)嶒?yàn)這種類型的熱管系統(tǒng)。在2011年，同樣研究了串聯(lián)和并聯(lián)連接的熱管儲(chǔ)存的性能。其中熱虹吸系統(tǒng)流行在幾個(gè)世界各地，如東亞和澳大利亞，原因是其有簡(jiǎn)單性和可靠性。熱虹吸驅(qū)動(dòng)力取決于熱交換器側(cè)臂和罐之間的壓力差和摩擦損失。因此，所產(chǎn)生的流量將是一個(gè)復(fù)雜的罐子充能狀態(tài)。熱交換器和管道的溫度分布是沿著熱交換器的頂部和罐子頂部的中的壓力降(以及管道和連接)。這種熱交換依賴于熱交換器的壓力降和罐子特性限制如何改造進(jìn)行，

43、其中應(yīng)放置可用于熱交換的儲(chǔ)罐。此外，如果設(shè)計(jì)得當(dāng)，強(qiáng)制循環(huán)的系統(tǒng)可以比自然對(duì)流驅(qū)動(dòng)系統(tǒng)實(shí)現(xiàn)更高的性能。這主要是解釋在一個(gè)低能量驅(qū)動(dòng)余弦下能量轉(zhuǎn)移率的增加。例如，一個(gè)40瓦的泵可產(chǎn)生驅(qū)動(dòng)力高于通過自然對(duì)流實(shí)現(xiàn)的一個(gè)系統(tǒng)的45倍以上。此外，以較低的成本，使用一個(gè)低能量泵。但是強(qiáng)制循環(huán)式系統(tǒng)的缺點(diǎn)是一個(gè)更高的復(fù)雜程度，以及要通過電力來運(yùn)行的水泵和控制。集中在專為寒冷地區(qū)的強(qiáng)制循環(huán)的系統(tǒng)研究較少。 wongsuwan和Kumar以TRNSYS軟件的結(jié)論預(yù)測(cè)準(zhǔn)確強(qiáng)制循環(huán)系統(tǒng)的性能。Buckles和Klein用TRNSYS軟件，從理論上探討不同的系統(tǒng)配置，并得出結(jié)論，相同容量的換熱器無論是置于內(nèi)部或外部的

44、存儲(chǔ)具有類似的表現(xiàn)，在2009年，Hobbi和Siddiqui使用TRNSYS從理論上優(yōu)化設(shè)計(jì)了在寒冷的氣候條件下的強(qiáng)制循環(huán)熱水系統(tǒng)。在其他研究中，每年的太陽能被用作設(shè)計(jì)參數(shù)進(jìn)行優(yōu)化。特別感興趣的是研究改造現(xiàn)有的熱水器在單一家庭住宅太陽能熱水器應(yīng)用在寒冷的地區(qū)存在一個(gè)缺乏。今天加裝太陽能生活熱水系統(tǒng)通常是在一系列連接現(xiàn)有系統(tǒng)的上游加裝一個(gè)新的太陽能儲(chǔ)存并使用現(xiàn)有的熱水鍋爐作為備用加熱器。某些改型系統(tǒng)利用rmosyphoning(熱虹吸)，因此，依賴于新的管道為該目的而進(jìn)行存儲(chǔ)。由于生活熱水的消費(fèi)量一直呈下降趨勢(shì)，而現(xiàn)有設(shè)備往往體積過大，并且有大負(fù)荷負(fù)載。結(jié)合低等級(jí)絕緣水平，如超過限度會(huì)導(dǎo)致大系統(tǒng)的熱損失。當(dāng)太陽能水溫低于備份溫度時(shí)，使用現(xiàn)有的存儲(chǔ)器作為太陽能熱水貯存那么在系統(tǒng)中的熱損失會(huì)減少。在知道現(xiàn)有鍋爐是接近其壽命的末尾時(shí)，它仍然是可以利用的，以利于改變現(xiàn)有的存儲(chǔ)。在本研究中，對(duì)在瑞典氣候的單家庭住宅傳統(tǒng)的家用熱水器采用強(qiáng)制循環(huán)太陽能熱水系統(tǒng)的的改造進(jìn)行了理論研究