Techno-economic analysis of an integrated collector storage solar water heater with CPC reflector for households

Few countries bank on solar water heating systems (SWHS) to meet their domestic hot water needs, and instead prefer to use fuel or electric/gas geysers. The reason is the former having relatively high initial investment and performance marred by poor maintenance, and the latter having low initial cost. In this light, we need to compare the economic feasibility of an SWHS with the other alternatives. In almost all solar energy systems, the annual loads are met by a combination of solar and non-solar alternatives, i.e. auxiliary or conventional energy source. Several economic criteria have been proposed and used for evaluating and optimising solar energy systems. The authors have made use of EES software to obtain the economic figures of merit. The proposed model has low initial cost and better long-time thermal performance estimates. The annual solar fraction for the model is 0.55 and the payback period is two years.     

Comparison of solar radiation data sources for design and performance appraisal of CSP systems in India

The choice of a solar radiation data source is expected to have a significant impact on the predicted performance of a concentrating solar power (CSP) system and consequently on its technical and financial feasibility. In the present study, an attempt has been made to analyse the effect of choice of various solar radiation data sources on the predicted performance of a CSP system at 13 different locations in 5 different climatic zones of India. It was observed that there is significant variation in the amount of annual electricity output obtained for various locations using different solar radiation data sources resulting in variations in levelised cost of electricity. For a 50-MW parabolic trough-based CSP plant located in Jaisalmer, the estimated value of annual electricity output varies from 63 to 124?GWh. For a CSP plant based on the central tower receiver technology, the corresponding range is from 106 to 145?GWh.     

太阳能-地源热泵联合供暖系统数值模拟研究

在北方寒冷地区的冬季,利用地源热泵机组(Ground Source Heat Pump Unit,GSHPU)为建筑物进行供暖是一种新型节能减排模式。由于在采暖期间从土壤中吸收了较多的热量,超过了土壤本身的热修复能力,会造成GSHPU的地埋管所在区域的土壤热稳定性能发生变化,使得其COP值下降,运行功耗增加。针对此问题,提出了太阳能-地源热泵联合供暖系统。该系统在冬季以太阳能热水系统(Solar Water Heating System,SWHS)的运行作为主要供热模式,GSHPU的间歇运行作为辅助供热模式,从而充分利用太阳能并解决阴天等气象因素所带来的集热量不足、供水温度低等的问题。在非供暖季期间,GSHPU停运,而SWHS通过热水循环,对GSHPU地埋管所在的土壤区域进行热量回补,使得土壤温度场稳定,从而确保GSHPU在冬季间歇运行时的高效性。以兰州地区某办公楼的太阳能-地源热泵联合供暖系统作为案例,基于TRNSYS软件,进行数值模拟和分析,验证了该系统的可行性,且节能效果明显。     

Assessment of water availability for wet cooling at potential locations for solar thermal power generation in India

ABSTRACT

This study presents the results of a preliminary attempt to assess water availability for wet-cooled solar thermal power plants at potential locations in India. A total of 95 locations with sufficient wastelands and annual average DNI more than 2000?kWh/m² have been considered for the analysis. Options of rainwater harvesting and groundwater extraction have been explored. It was observed that with rainwater harvesting, only 12 locations in different states are suitable for adoption of wet cooling. Further, with only groundwater extraction option, only one location in the state of Madhya Pradesh is found to be suitable for adoption of wet cooling. By combining both the approaches, it is observed that 28 of the 95 locations would have sufficient water available to meet the requirements of the plant. In the remaining 67 potential locations, the adoption of other available cooling options with relatively lesser water requirements may be appropriate.     

Different applications of Scheffler reflector for renewable energy: a comprehensive review

A fixed focus on receiver maintains constant temperature of receiver and it is achieved by Scheffler reflector. It is a best example of solar energy application used for medium-temperature applications. The present review shows a complete review of Scheffler reflector in solar thermal applications like desalination, coffee-making machine, agricultural application, electricity generation, hot water, cooking and plaster of Paris production. The Scheffler reflector is a best solar energy application in future emerging technologies.     

太阳能在LPG气化器的应用

提出了把太阳能用于LPG气化器的思路,设计了3种太阳能LPG气化系统.进行了技术分析和经济分析,太阳能LPG气化器具有节能环保的优势,在应用上是经济可行的.     

China's fuel gas sector: History,current status,and future prospects

China has a unique urban pipeline network of three types of fuel gases: manufactured gas (coal gas), Liquefied Petroleum Gas (LPG), and natural gas. Manufactured gas, which is often seen as an outdated technology in the western world, is still widely used in Chinese cities. LPG is distributed through community-based pipelines in many Chinese cities, in addition to its distribution in cylinders and canisters in rural areas. Natural gas consumption is increasing throughout China, particularly as a cooking fuel. Expanding the production and supply of natural gas in China faces many challenges. In particular, China's controls on natural gas prices have deterred investment in exploration and natural gas imports. However, recent price decontrols of unconventional natural gas (defined in Chinas as shale gas, coal-bed methane, and coal-to-natural-gas), and recent pricing reforms, appear likely to increase natural gas use. The prospect for increased exploration is promising but will still depend greatly on the future of institutional reforms. In the near term, regulatory reforms toward a more market-driven system will be the most critical issue in the development of China's fuel gas sector.     

Experimental investigation of the solar cooker during sunshine and off-sunshine hours using the thermal energy storage unit based on a parabolic trough collector

A solar cooker based on a parabolic trough collector with thermal energy storage (TES) was investigated. In this experimental set-up, solar radiations were focused on the absorber tube and the collected heat was transferred to the solar cooker by natural circulation (thermosiphon) of the working fluid. The water and thermal oil (engine oil) were used separately as working fluids. Acetanilide was used as the TES material in the solar cooker. In day time, the phase change material (PCM) stored heat as well as transferred it to the cooking pot. In evening time, the stored energy by PCM was used to cook the food. The cooking process was carried out with different foods and with variation in the quantity of food. It was found that the temperature of thermal oil was 10–24°C higher than water as the working fluid. The system was able to cook the food twice a day and the rate of evening cooking was higher as compared with noon cooking. Using thermal oil as the working fluid, the quantity of heat stored by PCM was increased by an amount of 19.45–30.38% as compared with water.     

Performance evaluation of evacuated tube solar domestic hot water systems in Hong Kong

Evacuated tube solar water heaters are increasingly in use in Hong Kong because of their good thermal efficiency and high water temperature achievable as compared to the flat-plate solar water heaters. But so far their thermal performance has not been systematically evaluated and therefore not well known to the users. This paper reports our experimental and numerical works on evaluating the performance of the two common types of evacuated tube solar water heaters for domestic hot-water applications. These are the single-phase open thermosyphon system and the two-phase closed thermosyphon system. Our results show that the daily and annual thermal performance of the two-phase closed thermosyphon solar collector is slightly better than the single-phase open thermosyphon design. But the payback periods of the two are relatively the same because of the higher initial costs of the two-phase closed thermosyphon collector system. Although economically they are less attractive than the flat-plate type collector system, they are suitable for applications in advanced systems with higher temperature demands.     

Estimation of direct solar irradiance intercepted by a solar concentrator in different modes of tracking (case study: Algeria)

While reasonably accurate knowledge of solar radiation data at the location of interest is necessary for the design of any solar energy conversion system, the use of concentrating solar collectors implies that these systems only work with the direct solar irradiance. In the present study, by using a methodology based on simple equations, the total hourly, daily, monthly and annual direct radiations incident on four different oriented solar concentrators were calculated only from the recorded data of monthly mean daily global and diffuse horizontal solar irradiance for three different Algerian sites, in order to choose the best mode of tracking for concentrating solar thermal power systems and concentrating solar photovoltaic power systems applications. The model predictions were found to be consistent with ground measurements and prior studies of Kalogirou. It was found that the greatest energy gains were achieved by using full tracking. Furthermore, the model can be included for application to other Algerian and worldwide locations for estimating direct solar irradiance intercepted by a solar concentrator in different modes of tracking.     

Choice of solar collector for applications below 100°C

Non-tracking collectors are the important technology options to harness the solar thermal energy at temperatures below 100°C. Thermal energy below this level has very wide applications in the residential and industrial sectors. Also, energy at this level can be used indirectly to produce cooling, fresh water or electricity. Flat plate and evacuated tube collectors with different design, configuration and cost were considered and their energy collection capabilities were estimated under the Kuwaiti conditions for different applications identified with the temperature. Based on the manufacturers' quotations and other economic parameters, the annual amortized cost of solar collectors were estimated. These values were used to estimate the system cost per unit of energy generation. A domestic solar water heater with an unglazed collector is the only solar system having economic viability at present. Evacuated tube collectors stand a good chance of being economically viable in future with increase in fuel prices and/or reduction in system cost.     

热管型太阳能热电联产系统

传统的太阳能光伏组件受温度影响较大,光伏组件表面温度的急剧升高会严重影响光伏电池的发电效率。太阳能热电联产系统回收利用太阳能电池产生的热能可降低太阳能电池的工作温度,在提高太阳能电池发电效率的同时亦可产生热水。充分运用热管导热技术,自主设计了热管型太阳能热电联产系统组件、太阳能光热系统。该系统运行两年来,年均产电2.37万k W·h,年产45℃以上热水2 000 t,具有显著的经济和环境效益,推广应用前景广阔。     

Exergetic modeling and performance evaluation of solar water heating systems for building applications

Solar water heating (SWH) is a well-proven renewable energy technology and has been used in many countries of the world. The basic technology is straightforward, although there are a variety of various types of SWH systems. In the performance assessment of SWH systems, energy analysis (first law) method has been widely used, while the number of the studies on exergetic assessment is relatively low. The SWH system investigated consists of mainly three parts, namely a flat plate solar collector, a heat exchanger (storage tank) and a circulating pump. The main objectives of the present study are as follows, differing from the previously conducted ones: (i) to model and assess SWH systems using exergy analysis (second law) method as a whole, (ii) to investigate the effect of varying water inlet temperature to the collector on the exergy efficiencies of the SWH system components, (iii) to study some thermodynamic parameters (fuel depletion ratio, relative irreversibility, productivity lack and exergetic factor) and exergetic improvement potential, and (iv) to propose and present an exergy efficiency curve similar to the thermal efficiency curve for solar collectors. The system performance is evaluated based on the experimental data of the Izmir province, Turkey, which is given as an illustrative example. Exergy destructions (or irreversibilities) as well as exergy efficiency relations are determined for each of the SWH system components and the whole system. Exergy efficiency values on a product/fuel basis are found to range between from 2.02 to 3.37%, and 3.27 to 4.39% at a dead (reference) state temperature of 32.77 °C, which is an average of ambient temperatures at eight test runs from 1.10 to 3.35 p.m., for the solar collector and entire SWH system, respectively. An exergy efficiency correlation for the solar collector studied was also presented to determine its exergetic performance. It is expected that the model presented here would be beneficial to the researchers, government administration, and engineers working in the area of SWH systems for residential applications.     

Fine particle number and mass concentration measurements in urban Indian households

Fine particle number concentration (D(p)>10 nm, cm(-3)), mass concentrations (approximation of PM(2.5), microg m(-3)) and indoor/outdoor number concentration ratio (I/O) measurements have been conducted for the first time in 11 urban households in India, 2002. The results indicate remarkable high indoor number and mass concentrations and I/O number concentration ratios caused by cooking. Besides cooking stoves that used liquefied petroleum gas (LPG) or kerosene as the main fuel, high indoor concentrations can be explained by poor ventilation systems. Particle number concentrations of more than 300,000 cm(-3) and mass concentrations of more than 1000 microg m(-3) were detected in some cases. When the number and mass concentrations during cooking times were statistically compared, a correlation coefficient r>0.50 was observed in 63% of the households. Some households used other fuels like wood and dung cakes along with the main fuel, but also other living activities influenced the concentrations. In some areas, outdoor combustion processes had a negative impact on indoor air quality. The maximum concentrations observed in most cases were due to indoor combustion sources. Reduction of exposure risk and health effects caused by poor indoor air in urban Indian households is possible by improving indoor ventilation and reducing penetration of outdoor particles.     

村镇住宅建设与太阳能利用

通过对我国太阳能资源分布情况的分析以及太阳能应用可行性研究,提出了一种既节约能源又节省投资的太阳能绿色建筑设计方案.将建筑设计技术与太阳能利用技术相结合,建造一种利用南外墙进行集热和蓄热的被动式太阳房或利用太阳能热水循环技术的主动式太阳房,解决严寒季节供暖问题以及生活热水供应问题,对发展村镇建设,提高人居环境质量,创建"和谐社会"有着重大的现实意义.     

Solar energy performance analysis of basin-type solar still under the effect of vacuum pressure

ABSTRACT

This paper deals with a solar still for distilled water, using the heat of the sun to evaporate, cool and then collect the water. They are used in areas where drinking water is unavailable, so that clean water is obtained from dirty water or from plants by exposing them to sunlight; vacuum pressure is delivered to still-type solar. The reason for selecting vacuum pressure is that during the monsoon and cloudy days, solar intensity will not be high as it leads to evaporation at lower temperature saline water under the soar still. The basin area for the production of 5 litres per day of fresh water is determined as 1.44?m²and the solar still basin area of 1.44?m² and 21.5° tilt angle are designed. Solar energy be may used full to alternate in electrical power and to purify water in future. Finally, the performance was analysed for the solar still with a vacuum pressure at 0.6 bar. The outcome of the theoretical analysis shows that adoption of 0.6 bar pressure inside the solar still improves the average performance by 30%. In order to overcome this problem, vacuum could be applied for the better performance of the solar still during the low solar intensity periods.     

寒冷地区浴池热水供应方式运行经济性比较分析

太阳能-空气源热泵热水系统作为可再生能源已得到广泛应用,但在我国北方寒冷地区运用较少。再加上空气源热泵自身存在低温环境运行效率过低甚至损坏机组的现象,需要对不同辅助热源辅助太阳能热水系统进行经济技术比较分析,以得到最佳的运行方案。通过对不同辅助热源辅助太阳能热水系统进行技术分析与计算,建立数学模型,模拟计算加热100 t水的全年运行情况,计算、分析不同辅助热源太阳能热水系统运行方案在长春地区的年运行总成本,结果表明:太阳能-空气源热泵-水源热泵热水系统在我国北方寒冷地区使用有很可观的发展空间。     

小高层强制安装太阳能热水器的可行性研究

对小高层强制安装太阳能热水器的可行性进行了研究分析,先从理论上进行了系统设计的方案选择,然后用计算机模拟的手段进行了论证,提出了在建筑物屋顶以及各墙面安装太阳能热水器的可行性及利用效率,从而解决了小高层安装太阳能热水器难的问题。     

集体宿舍热泵辅助太阳能热水器热性能分析

我国既有建筑面积为560亿m~2,绝大部分为高能耗建筑,生活热水能耗占建筑能耗的20%~30%。建筑节能势在必行。通过对上海地区某高校学生宿舍空气源热泵辅助太阳能热水系统的实际运行工况下的热性能测试和分析计算,得到该系统年运行耗能为807 445.6 MJ,热泵的平均COP为3.2,系统太阳能保证率为47%,系统年运行费用仅为37 147.4元,具有极大的节能经济性,为生活热水能耗研究提供了一定的理论指导。