Building-integrated PV activities within the IEA framework: Going from task 16 to task VII

Early in 1997 a new task will be launched within the scope of the International Energy Agency (IEA) Photovoltaic Power Systems Implementing Agreement. This new task, Task VII, aims to develop building-integrated photovoltaic (BIPV) technology, consider ing technical viability, economics and aesthetic quality. The task concentrates strongly on the involvement of architects, building engineers and urban planners, and the ability to increase their interest in BIPV. Task VII succeeds Task 16, ‘Photovoltaics in Buildings’ of the IEA Solar Heating and Cooling Program, completed in March 1996. It has proved to be very effective in developing and demonstrating new concepts for building-integrated photovoltaics, with t he international cooperation in the task assisting in advancing and promoting the application of photovoltaics in both residential and commercial buildings. Task 16 played a pioneering role in obtaining the World's attention for BIPV. It is expected that Task VII will provide accelerated development and market acceptance of this promising technology.     

Simplified life-cycle analysis of PV systems in buildings: present situation and future trends

The integration of photovoltaic (PV) systems in buildings shows several advantages compared to conventional PV power plants. The main objectives of the present study are the quantitative evaluation of the benefits of building-integrated PV systems over their entire life-cycle and the identification of best solutions to maximize their energy efficiency and CO₂ mitigation potential. In order to achieve these objectives, a simplified life-cycle analysis (LCA) has been carried out. Firstly, a number of existing applications have been studied. Secondly, a parametric analysis of possible improvements in the balance-of-system (BOS) has been developed. Finally, the two steps have been combined with the analysis of crystalline silicon technologies. Results are reported in terms of several indicators: energy pay-back time, CO₂ yield and specific CO₂ emissions. The indicators show that the integration of PV systems in buildings clearly increases the environmental benefits of present PV technology. These benefits will further increase with future PV technologies. Future optimized PV roof-integrated systems are expected to have an energy pay-back time of around 1·5 years (1 year with heat recovery) and to save during their lifetime more than 20 times the amount of CO₂ emitted during their manufacturing (34 times with heat recovery). © 1998 John Wiley & Sons, Ltd.     

Life-cycle air emissions from PV power systems

This paper addresses the air emissions of grid supply versus grid-connected and off-grid photovoltaic power generation, using the framework of life-cycle assessment, in the context of rural household energy supply in Australia. Emissions of carbon dioxide, sulphur dioxide and nitrous oxides are calculated for the three life-cycle stages of manufacture, use and disposal. Sensitivities to materials and data inputs, as well as to component efficiencies, lifetimes and sizing are discussed. For each supply option, demand management options, including insulation and appliance choice, and the substitution of solar heating or bottled gas for electricity, are considered. The best option in all cases, in terms of life-cycle air emissions, is a grid-connected photovoltaic system used to supply an energy-efficient household with a mix of solar, gas and electric appliances. However, in financial terms, with current Australian energy prices, this option represents a high capital and life-cycle cost. Additionally, for the grid options, electricity costs do not significantly disadvantage the high demand scenarios. Both results provide a clear illustration of current Australian energy-pricing policies being in conflict with long-term environmental sustainability. © 1998 John Wiley & Sons, Ltd.     

Intelligent PV Module for Grid-Connected PV Systems

Most issues carried out about building integrated photovoltaic (PV) system performance show average losses of about 20%–25% in electricity production. The causes are varied, e.g., mismatching losses, partial shadows, variations in current–voltage$(I$–$V)$characteristics of PV modules due to manufacturing processes, differences in the orientations and inclinations of solar surfaces, and temperature effects. These losses can be decreased by means of suitable electronics. This paper presents the intelligent PV module concept, a low-cost high-efficiency dc–dc converter with maximum power point tracking (MPPT) functions, control, and power line communications (PLC). In addition, this paper analyses the alternatives for the architecture of grid-connected PV systems: centralized, string, and modular topologies. The proposed system, i.e., the intelligent PV module, fits within this last group. Its principles of operation, as well as the topology of boost dc–dc converter, are analyzed. Besides, a comparison of MPPT methods is performed, which shows the best results for the incremental conductance method. Regarding communications, PLC in every PV module and its feasibility for grid-connected PV plants are considered and analyzed in this paper. After developing an intelligent PV module (with dc–dc converter) prototype, its optimal performance has been experimentally confirmed by means of the PV system test platform. This paper describes this powerful tool especially designed to evaluate all kinds of PV systems.     

Lessons from a PV pumping programme in south Morocco

This paper presents the experience of a PV pumping project being carried‐out in the South of Morocco since 1997. At present, the project has reached 18 villages, affecting 15 000 people. Total involved photovoltaic power is 46 kW_p, and the total volume of pumped water since the installation of the systems approaches 0.7 × 10⁶ m³. About half the PV systems are based on dedicated inverters, while the rest are based on standard frequency drivers. Both perform very similarly in terms of both efficiency and reliability. Wells have been selected to provide good water taste, and pumped water is distributed to all the individual houses. Average daily water consumption in summer varies from 13 to 50 litres per person depending on ease of water access and ‚urban proximity’︁. The maintenance infrastructure is based on an agreement between the European supplier company and a local NGO, which is in charge of all the local organizations. Copyright © 2005 John Wiley & Sons, Ltd.     

The PV infrastructure: Architecture from houses to highways

Integrating photovoltaics into the built environment presents unique opportunities and challenges. Designers have to mediate between the functional demands of photovoltaics as solar devices and their architectural role as a building material. Photovolt aics are highly modular and will be used in large and small projects; their design will have to be considered at all scales. Solutions to these problems will change, for better or worse, the orientation and focus of the built environment. Will buildings, now mostly indifferent or even hostile to their climate, turn outward, expressing their relationship to the sun, or will the landscape be transformed into a sea of modules, fixed at monotonously optimized angles?     

On the available diversity gain from different dual-polarizedantennas

Dual-polarized antennas are traditionally characterized in terms of port-to-port isolation and co- and cross-polar radiation patterns. For base station antennas in a mobile communications system, the critical parameter is instead the far-field coupling between the two channels. In a mobile communication system, base station antennas with a nominal ±45° to vertical linear polarization are commonly used. Such antennas are difficult to design with constant polarization characteristics in azimuth. We calculate the antenna output power correlation and diversity gain under Rayleigh fading conditions and different values of the environment cross-polar discrimination. Two different antennas are compared: a dual-polarized aperture coupled patch and a slanted dipole configuration, both over an infinite groundplane. We show that the aperture coupled patch provides lower output correlation and higher diversity gain than the slanted dipoles in all investigated cases     

碲镉汞光伏器件的电极界面参数

利用热场发射理论和数值计算方法 ,分析了碲镉汞光伏器件的电流 -电压特性 ,提取了金属 -半导体 (MS)界面参数 ,并对这些参数进行了讨论 .结果表明 ,Sn/Au金属膜 -碲镉汞薄膜 PN器件的电极界面的势垒高度锁定在“Bardeen”限 ,界面密度比介质膜 -碲镉汞的大一个量级     

碲镉汞光伏器件的电极界面参数

利用热场发射理论和数值计算方法,分析了碲镉汞光伏器件的电流-电压特性,提取了金属-半导体(MS)界面参数,并对这些参数进行了讨论.结果表明,Sn/Au金属膜-碲镉汞薄膜PN器件的电极界面的势垒高度镇定在"Bardeen"限,界面密度比介质膜-碲镉汞的大一个量级.     

Europe's PV Roadmap

The first report from Europe's Photovoltaic Network (PVnet), set up in 2001, is expected in June, timed for the World Renewable Energy Congress, organised by UNESCO and to be held 29 June–5 July in Köln, Germany.     

Singapore PV studies

The Construction Industry Training Institute (CITI) in Singapore is to set up some 100 roof solar panels as part of a study into the viability of tapping solar power.     

PV thermal systems: PV panels supplying renewable electricity and heat

With PV Thermal panels sunlight is converted into electricity and heat simultaneously. Per unit area the total efficiency of a PVT panel is higher than the sum of the efficiencies of separate PV panels and solar thermal collectors. During the last 20 years research into PVT techniques and concepts has been widespread, but rather scattered. This reflects the number of possible PVT concepts and the accompanying research and development problems, for which it is the general goal to optimise both electrical and thermal efficiency of a device simultaneously. The aspects that can be optimised are, amongst others, the spectral characteristics of the PV cell, its solar absorption and the internal heat transfer between cells and heat‐collecting system. Another important level of optimisation is for the PVT device geometry and the integration into a system. The electricity and heat demand and the temperature level of the heat determine the choice for a certain system set‐up. With an optimal design, PVT systems can supply buildings with 100% renewable electricity and heat in a more cost‐effective manner than separate PV and solar thermal systems and thus contribute to the long‐term international targets on implementation of renewable energy in the built environment. Copyright © 2004 John Wiley & Sons, Ltd.     

CTX PV520

CTX PV520采用15英寸主动式矩阵排列TFT液晶面板,产品的体积为375×383×169mm,重量为6公斤.以液晶显示器而言,并不算是特别轻巧的产品.产品提供1024×768的屏幕分辨率,垂直扫描频率则为75Hz.而显示器的亮度为200cd/m2,对比则是350:1.