Design and construction of a system for sun-tracking

An electromechanical system to follow the position of the sun was designed and built at the Solar Evaluation Laboratory of the Technical University Federico Santa Maria (UTFSM) in Valparaiso. It allows the automatic measurement of direct solar radiation with a pyrheliometer. It operates automatically, guided by a closed loop servo system. A four-quadrant photo detector senses the position of the sun and two small DC motors move the instrument platform keeping the sun’s image at the center of the four-quadrant photo detectors. Under cloudy conditions, when the sun is not visible, a computing program calculates the position of the sun and takes control of the movement, until the detector can sense the sun again. The constructed system was tested in the climatic conditions of the city of Valparaiso, Chile. The presented tracker proves the effective work of a simple and cheap mechanism, which can be adapted to also work with larger following installations like solar cell panels, concentrators, etc.     

Application of one-axis sun tracking system

This paper introduces design and application of a novel one-axis sun tracking system which follows the position of the sun and allows investigating effects of one-axis tracking system on the solar energy in Turkey. The tracking system includes a serial communication interface based on RS 485 to monitor whole processes on a computer screen and to plot data as graphic. In addition, system parameters such as the current, the voltage and the panel position have been observed by means of a microcontroller. The energy collected is measured and compared with a fixed solar system for the same solar panel. The results show that the solar energy collected on the tracking system is considerably much efficient than the fixed system. The tracking system developed in this study provides easy installation, simple mechanism and less maintenance.     

Design of one-axis tracked linear Fresnel lenses

The most frequently used criterion in the design of linear Fresnel lenses consists of minimizing the radiation spread at the collector when the lens is illuminated by rays that are contained in the full lens acceptance angle and are incident on the lens in the plane perpendicular to the lens axis. This paper analyzes this topic and concludes that when the lenses are one-axis-tracked this criterion can be improved by replacing the perpendicular plane with another forming a certain angle to it. When calculated for a specific lens, at the location of Madrid, the new criterion was found to yield an increase of more than 7% in the total annual energy collected.     

蝶式聚光光伏发电自动跟踪太阳装置的设计

在分析太阳运行规律的基础上,描述了蝶式聚光器的机械结构、传动机构及自动跟踪控制的原理、方法,提出了一种在聚光条件下太阳跟踪的新方案.该蝶式反射聚光光伏自动跟踪太阳装置制造和运行成本低,跟踪精度较高,应用前景广阔.     

Characterisation of a 300× photovoltaic concentrator system with one-axis tracking

A solar concentrator with one-axis tracking is being developed at our institute. This concentrator system achieves a high geometrical concentration ratio of 300 using a parabolic trough mirror and a three-dimensional second stage consisting of compound parabolic concentrators. The design of the system as well as the characterisation of the second stage is described in this paper.     

太阳能单轴跟踪系统的PLC设计

提出基于可编程逻辑控制器PLC的太阳能跟踪系统,使光伏模块能实时跟踪太阳光照,从而最大限度地获得太阳能.系统的硬件有PLC输入/输出端口的配置、信号处理单元、光敏电阻光强法比较电路和开关电源的设计;系统的软件有PLC的控制和监控程序,基于Visual Basic 6.0软件平台开发的PC机监控和数据采集程序.基于PLC的太阳能跟踪系统既适用于独立的太阳能发电设备,也适用于串、并联的大型太阳能光伏发电系统的现场总线控制.     

用80C196KC单片机实现太阳跟踪

描述了一种跟踪控制的实现方法。核心部件80C196KC单片机通过预先计算的太阳位置进行跟踪。并通过光学传感器校正位置量可能出现的误差。该系统与模拟系统相比仅增加了少量的低成本集成电路。具有精确度高、适应性好等特点。     

时序与光传感复合控制在太阳跟踪系统中的应用

介绍了两类常用的太阳能跟踪控制方式,即时序跟踪控制与光传感跟踪控制,以及两种跟踪方式的复合控制原理,并根据原理进行了控制系统的硬件设计和软件设计.跟踪控制系统在重庆市大足县一光伏电站投入使用,二年内无故障,且能够实现高精度全天候太阳跟踪.     

Design and construction of a residential solar heating and cooling system

The first integrated system providing heating and cooling to a building by use of solar energy has been designed and installed in a residential-type building at Colorado State University. Solar heated liquid supplies heat to air circulating in the building and to a lithium bromide absorption air conditioner. Service hot water is also provided. Approximately two-thirds of the heating and cooling loads are expected to be met by solar energy, the balance by natural gas. The paper contains details of design and principles of operation. A breakdown of actual costs of the equipment and its installation is also provided.     

Multi-axes sun-tracking system with PLC control for photovoltaic panels in Turkey

In the present study, the azimuth and solar altitude angles of the sun were calculated for a period of 1 year at 37.6° latitude in the Northern hemisphere, where Turkey is located, and according to these angles, an electromechanical system which tracks the sun on both axes and which is controlled via a programmable logic control (PLC) and an analog module was designed and implemented.After the mechanical control unit of the designed system was started, the performance measurements of the solar panel were carried out first when the solar panel was in a fixed position and then the solar panel was controlled while tracking the sun on azimuth and solar altitude angles and the necessary measurements were performed. It was observed that the control system operated without a problem. Besides, when the data obtained from the measurements were compared, it was seen that 42.6% more energy was obtained in the two-axes sun-tracking system when compared to the fixed system.     

General formula for on-axis sun-tracking system and its application in improving tracking accuracy of solar collector

Azimuth-elevation and tilt-roll tracking mechanism are among the most commonly used sun-tracking methods for aiming the solar collector towards the sun at all times. It has been many decades that each of these two sun-tracking methods has its own specific sun-tracking formula and they are not interrelated. In this paper, the most general form of sun-tracking formula that embraces all the possible on-axis tracking methods is presented. The general sun-tracking formula not only can provide a general mathematical solution, but more significantly it can improve the sun-tracking accuracy by tackling the installation error of the solar collector.     

Design and construction of a simple blade pitch measurement system for small wind turbines

For small wind turbines to be reliable they must have in place good mechanisms to protect themselves against very high winds or sudden removal of load. One common protection method in small wind turbines is that of blade feathering. It is important that the blade feathering mechanism of a small wind turbine is tested before the turbine is installed in the field. This paper presents a simple system for monitoring the blade feathering of a turbine with an overall component cost that small wind turbine manufacturers can afford. The Blade Pitch Measurement System (BPMS) has been designed and constructed by the Research Institute of Sustainable Energy (RISE) and aids small wind turbine manufacturers in testing and optimising the settings of the blade feathering mechanisms on their machines. The results show that the BPMS was successful in recording the behaviour of the blade feathering mechanism in field trials with a 20 kW and a 30 kW wind turbine. The BPMS displays significant potential as an effective, inexpensive system for small wind turbine manufacturers to ensure the reliability of their pitch regulating over-speed protection mechanisms.     

Design and construction of non-imaging planar concentrator for concentrator photovoltaic system

A novel configuration of solar concentrator, which is the non-imaging planar concentrator, capable of producing much more uniform sunlight and reasonably high concentration ratio, is designed and constructed. This design is envisioned to be incorporated in concentrator photovoltaic (CPV) systems. The work presented here reports on the design, optical alignment and application of the prototype, which is installed at Universiti Tunku Abdul Rahman (UTAR), Malaysia. In the architecture of the prototype, 360 flat mirrors, each with a dimension of 4.0 cm × 4.0 cm, are arranged into 24 rows and 15 columns with a total reflection area of about 5760 cm². In addition to that, illumination distribution for the prototype is simulated and its results are then compared with the experiment result.     

A review of principle and sun-tracking methods for maximizing solar systems output

Finding energy sources to satisfy the world's growing demand is one of society's foremost challenges for the next half-century. The challenge in converting sunlight to electricity via photovoltaic solar cells is dramatically reducing $/watt of delivered solar electricity. In this context the sun trackers are such devices for efficiency improvement.The diurnal and seasonal movement of earth affects the radiation intensity on the solar systems. Sun-trackers move the solar systems to compensate for these motions, keeping the best orientation relative to the sun. Although using sun-tracker is not essential, its use can boost the collected energy 10–100% in different periods of time and geographical conditions. However, it is not recommended to use tracking system for small solar panels because of high energy losses in the driving systems. It is found that the power consumption by tracking device is 2–3% of the increased energy.In this paper different types of sun-tracking systems are reviewed and their cons and pros are discussed. The most efficient and popular sun-tracking device was found to be in the form of polar-axis and azimuth/elevation types.     

Design and construction of a two-axis Sun tracking system for parabolic trough collector (PTC) efficiency improvement

An experimental study was performed to investigate the effect of using a continuous operation two-axes tracking on the solar energy collected. The collected energy was measured and compared with that on a fixed surface tilted at 40° towards the South. The results indicate that the measured collected solar energy on the moving surface was significantly larger (up to 46.46%) compared with the fixed surface. The proposed two-axis Sun tracking system was characterized by a fairly simple and low-cost electromechanical set-up with low maintenance requirements and ease on installation and operation.     

吉林省节能减排技术服务与支持系统的构建

应对气候变化问题已成为实现我国可持续发展的必然要求,需要各省加以重视并采取行动。在分析吉林省节能减排发展情况的基础上,为了促进吉林省企业节能减排成果转化,提高企业自主创新能力和水平,设计并构建吉林省节能减排技术服务与支持系统,在分析系统功能主体、功能定位、组织模式、运行保障措施以及总体原则的基础上,对平台系统进行了总体构架、软件和硬件结构、开发环境、运行环境以及数据库的设计。     

Design, construction, performance evaluation and economic analysis of an integrated collector storage system

The design and construction of an Integrated Collector Storage (ICS) system is presented in this paper. The main advantage that such a collector system presents, with respect to conventional flat-plate collectors, is the fact that it is of a very low profile. The main disadvantage of these collectors comes from the design of the system, i.e. with the receiver of the collector being also the storage vessel, it is not possible to insulate it properly and there are significant heat losses during the night. System modelling and optimisation is carried out by the use of a computer code written for the purpose. Performance results presented are in good agreement with the predicted results, especially for the end-of-day storage temperature which is predicted to within 5.1%. The initial cost of the system presented here is 13% cheaper than the corresponding flat-plate (FP) collector of the same aperture area and storage volume. Additionally, the economic analysis of the two systems, performed with the F-Chart program, showed a yearly F-value of 0.85 for the ICS system compared to 0.83 for the FP system, a pay-back period of nine years for the ICS system, compared to 11 years for the FP system and a life cycle saving of C£330 for the ICS system compared to C£201 for the FP system.     

Design construction and test run of a solar powered solid absorption refrigerator

The intermittent system used CaCl₂ and NH₃ as absorbent and refrigerant, respectively. The absorbent was mixed with 20% by weight of CaSO₄, as cement, and prepared as hard porous granules of 5–10 mm sizes.The double glazed collector/absorber/generator unit used clear PVC and plane glass sheets, with the former as the outer cover. Overall collector plate exposed area was 1.41 m². A stagnant water evaporative condenser was designed and constructed of re-inforced sandcrete, with steel condenser tubes, and was coupled to the system. The evaporator was a spirally coiled steel tube immersed in a pool of stagnant water. Absorbent cooling during absorption was by natural convection of air over the collector plate and tubes, coupled with sky radiation. All construction, except the collector covers and porous condenser walls, were of steel sheets and tubes.Ambient temperatures during absorption and generation ranged over (25°–35°C). Tests indicated that cooling capacities of the NH₃ condensed were around 714 KJ m⁻², while effective cooling obtained was equivalent to an ice production of 1 kg m⁻², per day.     

Design and performance characteristics of a parabolic-trough solar-collector system

A comparison of the advantages and disadvantages of concentrating collectors against conventional flat-plate collectors are presented. This is followed by the design of a parabolic-trough solar-collector system, due consideration having been given to collector-aperture and rim-angle optimisation, together with the receiver-diameter selection. The collector characteristic curve gives a test slope of 0·441 and a test intercept equal to 0·642. The value of the test slope differs considerably from the initially predicted value: this is attributed to the heat losses from the receiver support brackets. Subsequent allowance for these losses is presented: this reduces the difference from 24·9% to 5·7%. Other tests are presented, including the determination of the collector's incidence-angle modifier, time constant and acceptance angle.     

Design and testing of a compact PEM electrolyzer system

A compact prototype system for H₂ production based on a Polymer Electrolyte Membrane (PEM) stack was developed and investigated. A detailed study and an optimization of the Balance of Plant (BoP) was carried out. The system was developed in laboratory by using commercial devices tailored around in house-made membrane electrode assemblies (MEAs). The study regarded both the hydraulic circuit efficiency loss and its optimization by varying process parameters. Energy consumption for auxiliary devices was studied at different temperatures (40, 60 and 75 °C). Efficiency and control strategy management of the system were investigated. Despite an increase of stack performance observed at high temperature, maximum system efficiency (65% compared to HHV) was obtained at 40 °C because of moderate energy consumption by the electric heater. To evaluate the stack contribution to the overall efficiency, the present investigation was completed by a hydrodynamic study of the stack inside the system. Diffusional aspects related to the water mass distribution inside the stack were investigated through a computational fluid dynamic analysis (CFD). In particular, a 3D analysis of the whole stack composed by 120 channels and 10 cells was carried out. The model showed a quite uniform distribution of water over the individual channels and a homogeneous pressure inside the cells. Accordingly, the risk of having hot spots and gases accumulated inside the stack was minimal.