Performance improvement by discharge from different levels in solar storage tanks

The thermal advantages by utilizing discharge from different levels in solar storage tanks are investigated, both for a small SDHW system and for a solar combisystem.The investigations showed that it is possible to increase the thermal performance of both types of systems by using two draw-off levels from the solar tanks instead of one draw-off level at a fixed position.The best position of the second draw-off level is in the middle or just above the middle of the tank. For the investigated small SDHW system with a realistic draw off hot water temperature of 40 °C and 45 °C and an auxiliary volume temperature of 50.5 °C the increase of the thermal performance by the second draw-off level is about 6%.For the investigated solar combisystem the increase in thermal performance by using one extra draw-off level, either for the domestic hot water heat exchanger or for the heating system, is about 3%, while an improvement of about 5% is possible by using a second draw-off level both for the domestic hot water heat exchanger and for the heating system.     

A new and inexpensive open source data acquisition and controller for solar research: Application to a water-flow glazing

A water-flow window consists of two glass panes making up a chamber in which a water layer flows in a controlled way. Such windows may be considered as Building-Integrated Solar Thermal (BIST) collectors, and could assist to incorporate renewable energy systems in buildings, improving their energy efficiency, especially when they are properly managed by a control system. Despite the need of an automatic controller for this kind of window and the advantages of microprocessor-based control for solar systems, only differential controllers have been described. A novel controller based on an inexpensive open source microcontroller board has been designed, built, programmed and installed in an experimental prototype water-flow window. The proposed data acquisition and control system, the code sequence steps, a model algorithm, and a comparison between the data collected by the system and a commercial datalogger are presented. The advantages of using an open source board for the proposed control system are analysed and the benefits of using a control system based on a microcontroller are discussed.     

主动式太阳热水系统自控方式

通过对现行主动式太阳热水系统水泵的控制方案进行分析比较,提出了一种新型控制方案。无论在何种天气条件下,这种控制方案都可使主动式太阳热水系统净收益达到最优值。时间控制模式、辐射量控制模式及温差控制模式相对于新型控制模式的最大收益偏差率分别为:-8.49%、-100%、-96.19%。     

A conceptual framework for the vehicle-to-grid (V2G) implementation

The paper focuses on presenting a proposed framework to effectively integrate the aggregated battery vehicles into the grid as distributed energy resources to act as controllable loads to levelize the demand on the system during off-peak conditions and as a generation/storage device during the day to provide capacity and energy services to the grid. The paper also presents practical approaches for two key implementation steps – computer/communication/control network and incentive program.     

耦合太阳能的燃气轮机动态性能与控制特性研究

为深入研究耦合太阳能对燃机动态特性的影响,建立耦合太阳能的燃气轮机以及相应控制系统的动态模型。分析槽式集热器不同耦合方式对系统稳态性能的影响以及受到外界负荷及太阳直射辐射（DNI）扰动时各参数的动态响应,研究槽式集热器金属热容对系统动态特性的影响,针对比例积分（PI）控制,研究相应参数对系统调节效果的影响。结果表明,采用集热器布置在回热器前时,系统的排气温度相对较高,但系统效率会相对较低,受到外界负荷扰动时,系统响应更加迅速,采用集热器布置在回热器后时则可得到更高的燃料节省量;DNI变化时2种方式的系统响应速度相同;当集热器金属热容较小时,系统的响应时间主要受控制系统及回热器惯性影响,随着热容增加,调节集热器惯性参数为改变系统动态响应时间的最有效方式;比例系数K_p与积分系数K_i应合理选取,过大或过小均会使系统失调的危险性提高。     

Nearest-neighbor methodology for prediction of intra-hour global horizontal and direct normal irradiances

This work proposes a novel forecast methodology for intra-hour solar irradiance based on optimized pattern recognition from local telemetry and sky imaging. The model, based on the k-nearest-neighbors (kNN) algorithm, predicts the global (GHI) and direct (DNI) components of irradiance for horizons ranging from 5 min up to 30 min, and the corresponding uncertainty prediction intervals. An optimization algorithm determines the best set of patterns and other free parameters in the model, such as the number of nearest neighbors. Results show that the model achieves significant forecast improvements (between 10% and 25%) over a reference persistence forecast. The results show that large ramps in the irradiance time series are not very well capture by the point forecasts, mostly because those events are underrepresented in the historical dataset. The inclusion of sky images in the pattern recognition results in a small improvement (below 5%) relative to the kNN without images, but it helps in the definition of the uncertainty intervals (specially in the case of DNI). The prediction intervals determined with this method show good performance, with high probability coverage (≈90% for GHI and ≈85% for DNI) and narrow average normalized width (≈8% for GHI and ≈17% for DNI).     

Smart switchable glazing for solar energy and daylight control

The exciting field of chromogenic materials for smart windows and other large-area applications is discussed. A selection of switchable glazing devices that change color electrically are detailed. The types of devices covered are the electrochromic which change color electrically, covering electrochromic, dispersed liquid crystal and dispersed particle glazing that switch under an applied electric field. Device structures and switching characteristics are compared. The status of prototype and commercial devices from commercial and university labs through out the world are covered. A discussion of the future of this technology is made including areas of necessary development for the realization of large area glazing in excess of 1m².     

小浪底电站尾水渠喷锚支护试验及施工质量控制

根据小浪底工程电站尾水明渠喷锚支护的设计要求，对施工用喷射混凝土，砂浆锚杆及树脂张拉锚杆这两种支护方法进行有益的探讨，提出了喷射混凝土及树脂张拉锚杆室内试验及施工现场试验的各项指标及其施工工艺过程和施工质量控制方法，可作为今后此类工程施工的借鉴。     

变速恒频风力发电系统及其控制技术研究

为了最大限度地利用风能,风力发电系统应采用变速恒频控制策略。分析了鼠笼异步发电系统、双馈发电系统、无刷双馈发电等变速恒频风力发电系统的原理、性能及特点,通过对比各种风力发电机和各种控制方法的优缺点,对未来风力发电机和风力发电控制技术的发展趋势做了展望: 风力发电机大型化;采用变桨距和变速恒频技术;风力发电机采用直接驱动;采用智能化控制等。     

The importance of instrumental,symbolic, and environmental attributes for the adoption of smart energy systems

The conceptual model on motivations to adopt sustainable innovations (Noppers et al., 2014) proved to be successful in explaining proxies of the adoption of sustainable innovations: positive evaluations of the utility (instrumental attributes), environmental impact (environmental attributes), and specifically the extent to which the innovation says something about a person (symbolic attributes) increased interest in and intention to adopt sustainable innovations. In this paper, we examined to what extent the evaluations of these three attributes can also explain the actual adoption of smart energy systems that facilitate sustainable energy use. Results showed that adopters of smart energy systems (who agreed to participate in a project in which these systems were tested) evaluated the symbolic attributes of these systems more positively than non-adopters (who did not participate in this project), while both groups did not differ in their evaluation of the instrumental and environmental attributes of smart energy systems. A logistic regression analysis indicated that only evaluations of the symbolic attributes explained actual adoption of smart energy systems. Policy could stress and enhance the symbolic attributes of sustainable innovations to encourage adoption.     

Study on areal solar irradiance for analyzing areally-totalized PV systems

This paper describes the methodology for quantification of solar irradiance fluctuation in order to analyze the areally totalized PV systems, which consist of a large number of PV systems connected to each other in the optimum size of a certain community area. Two factors quantifying the fluctuation, fluctuation factor and power spectral density, and some examples are presented. Also cross-correlation analysis between nine stations' measurements were operated to estimate the extent of the power fluctuation in a certain area size and to determine optimum size of the area of areally localized PV systems.     

电极片检测熔盐储罐泄漏的实验研究

提出利用电极片检测熔盐储罐泄漏的方法并实验研究其可行性。结果表明,不同温度的熔盐发生泄漏时,熔盐会使电极片的回路立即形成通路,从而灵敏地检测到熔盐储罐的泄漏。并且,熔盐的运行温度越高、电极片布置位置越靠近地基材料顶部,熔盐泄漏到电极片上时导电性越强,电路中的电流越大,电极片检测熔盐罐泄漏的灵敏性和持续性越好。     

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.     

Experimental investigation on solar-flue gas chimney

Flue gases exhausted from thermal power plants contain more than 50% of the fuel thermal energy. In the present work, experimental investigation was carried out to study the utilization of thermal energy in flue gases to enhance the performance of modified solar chimney consisting of Savonius wind rotor. A modified solar chimney model was designed and fabricated to carry out experimental measurement. The model consists of thermal energy conversion unit; Savonius wind rotor and a chimney. The thermal energy in the flue gas transfers to the air particles in the air channel across the absorber plate and results in upward air stream due to the buoyancy effect. With an 9 absorber area of 2.36 re＇and flue gas mass flow rate of0.18 kg/s, air velocity＇ of 4.1 m/s was achieved at the top of the thermal unit. Increasing the mass flow rate of the flue gas to 0.24 kg/s enhances the air velocity to be 4.6 m/s. The results have demonstrated the possibility＇ of utilizing the thermal energy in the waste flue gas to enhance the performance of a solar chimney and facilitate the continuous operation during the absence of the sun.     

智能电网通信技术的研究

智能电网具有高速、双向、实时、集成的通信系统,能够实时监视和控制电网运行,预防事故发生和及时清除故障。研究了智能电网的通信技术,设计了集光纤通信、新一代3G/4G移动通信、无线局域网WLAN(IEEE 802.11)等先进通信技术的智能电网通信系统,遍布整个电网的通信设备将信息在各种测量装置、控制设备和执行元件之间进行相互传递,以保证电网安全、可靠、经济地运行。     

陶瓷太阳板及其应用的研究

陶瓷太阳板以普通瓷土、工业废弃物为原料、制造工艺简单、生产耗能少、成本低、寿命长、效率高;建造的陶瓷太阳能房顶与原房顶共用结构层、保温层、防水层,结构简单、与建筑一体化、与建筑同寿命,隔热、保温效果优于普通房顶,为建筑物提供热水、取暖、空调;用于沙漠太阳能发电、海水淡化、苦咸水淡化、改造沙漠成为耕地;可能实现太阳能使用成本低于常规能源。