The performance of PV‐t systems for residential application in Bangkok

This paper focused on the performance of photovoltaic‐thermal (PVT) systems working in Bangkok for residential applications. The PVT system is one which produces both electricity and low temperature heat at the same time. This paper investigated the performance of PVT systems that use different types of commercial solar PV panels. The characteristics of the PV panels were used as input parameters in the simulation. Each system comprises 2 m² of PVT collector area. Water draw patterns are those with a typical consumption of medium size houses in Bangkok, and the measured monthly average city water temperature of Bangkok has been used to estimate the energy output. The results show that the optimum water flow rate is 20 kg/h for all types of PVT collectors and the effect of water flow can improve the cell efficiency of PV cells. Moreover, the total energy output from the PVT collectors, which had glass covers is very significantly higher than those without one. The c‐Si PVT panel gave the best performance with the highest rate of primary energy reduction. The payback time of each system is 6.4, 11.8, and 13.4 years for a‐Si, mc‐Si, and c‐Si types of PVT system, respectively. This investigation concludes that from the viewpoint of system performance, c‐Si PVT is the most promising type than whereas from the viewpoint of economy, a‐Si PVT has the fastest payback time. Copyright © 2012 John Wiley & Sons, Ltd.     

Energy,cost and LCA results of PV and hybrid PV/T solar systems

Hybrid photovoltaic/thermal (PV/T) solar systems provide a simultaneous conversion of solar radiation into electricity and heat. In these devices, the PV modules are mounted together with heat recovery units, by which a circulating fluid allows one to cool them down during their operation. An extensive study on water‐cooled PV/T solar systems has been conducted at the University of Patras, where hybrid prototypes have been experimentally studied. In this paper the electrical and thermal efficiencies are given and the annual energy output under the weather conditions of Patras is calculated for horizontal and tilted building roof installation. In addition, the costs of all system parts are included and the cost payback time is estimated. Finally, the methodology of life cycle assessment (LCA) has been applied to perform an energy and environmental assessment of the analysed system. The goal of this study, carried out at the University of Rome ‘La Sapienza’ by means of SimaPro 5·1 software, was to verify the benefits of heat recovery. The concepts and results of this work on energy performance, economic aspects and LCA results of modified PV and water‐cooled PV/T solar systems, give a clear idea of their application advantages. From the results, the most important conclusion is that PV/T systems are cost effective and of better environmental impact compared with standard PV modules. Copyright © 2005 John Wiley & Sons, Ltd.     

光伏并网逆变器控制策略研究

随着光伏技术的日益发展,对太阳能的利用逐渐从无电地区发展到有电地区,许多国家都推出了光伏发电计划。在光伏并网发电系统中,逆变器实现把太阳能电池板产生直流电能转化为和电网同频同相的交流电能并且馈入电网,光伏并网逆变器是光伏并网发电系统的枢纽单元。     

Modular Deformable Steam Electricity Cogeneration System with Photothermal,Water, and Electrochemical Tunable Multilayers

Capturing solar energy for thermal conversion in a highly efficient manner for steam‐electricity cogeneration is particularly opportune in the context of optimal solar energy utilization for concurrent water‐energy harvesting. Herein, an integrative photothermal evaporator/thermogalvanic cell with the desired optical, heat, water, and electrochemical management for synergistic steam‐electricity production is reported. Versatile layer by‐layer assembly is employed to integrate a hydrogel/metal‐oxide/polymer into a multilayer film with individually addressable thickness, composition, and structure. As such, the ultimate integrative multilayer film cell demonstrates a unified high surface area and conductive electrodes, broadband absorption, rapid water suction‐ion exchange, and thermal insulation properties. Thus, the designed cell immensely suppresses heat losses, achieving a high solar thermal conversion efficiency of 91.4% and maximum power outputs of ≈1.6 mW m^?2. Additionally, the self‐floating, deformable, modular integral device presents appealing attributes such as salt‐rejection for viable seawater desalination, high mechanical stability, and resilience to demanding operating conditions, and configurable on‐demand/point‐of‐use tandem structure to maximize clean water and power generation value per area. This integrated strategy may provide prospective opportunities to reduce dependence on fossil fuels and freshwater inputs and solutions for renewable and decentralized clean water and electricity.     

Overall efficiency enhancement and cost optimization of semitransparent photovoltaic thermal air collector

A semitransparent photovoltaic‐thermal (PV/T) air collector can produce electricity and heat simultaneously. To maximize the thermal and overall efficiency of the semitransparent PV/T air collector, its availability should be maximum; this can be determined through a Markov analysis. In this paper, a Markov model is developed to select an optimized number of semitransparent PV modules in service with five states and two states by considering two parameters, namely failure rate ( λ ) and repair rate (µ). Three artificial neural network (ANN) models are developed to obtain the minimum cost, minimum temperature, and maximum thermal efficiency of the semitransparent PV/T air collector by setting its type appropriately and optimizing the number of photovoltaic modules and cost. An attempt is also made to achieve maximum thermal and overall efficiency for the semitransparent PV/T air collector by using ANN after obtaining its minimum temperature and available solar radiation.     

Coupling PV and CAES power plants to transform intermittent PV electricity into a dispatchable electricity source

This study investigates the transformation of photovoltaic (PV) electricity production from an intermittent into a dispatchable source of electricity by coupling PV plants to compressed air energy storage (CAES) gas turbine power plants. Based on historical solar irradiation data for the United States' south western states and actual PV and CAES performance data, we show that the large‐scale adoption of coupled PV–CAES power plants will likely enable peak electricity generation in 2020 at costs equal to or lower than those from natural gas power plants with or without carbon capture and storage systems. Our findings also suggest that given the societal value of reducing carbon dioxide and the sensitivity of conventional generation to rising fossil fuel prices, this competitive crossover point may occur much sooner. Copyright © 2008 John Wiley & Sons, Ltd.     

Performance,cost and life‐cycle assessment study of hybrid PVT/AIR solar systems

An alternative and cost‐effective solution to building integrated PV systems is to use hybrid photovoltaic/thermal (PV/T) solar systems. These systems consist of PV modules with an air channel at their rear surface, where ambient air is circulating in the channel for PV cooling and the extracted heat can be used for building thermal needs. To increase the system thermal efficiency, additional glazing is necessary, but this results in the decrease of the PV module electrical output from the additional optical losses of the solar radiation. PV/T solar systems with air heat extraction have been extensively studied at the University of Patras. Prototypes in their standard form and also with low‐cost modifications have been tested, aiming to achieve improved PV/T systems. An energetic and environmental assessment for the PV and PV/T systems tested has been performed by the University of Rome ‘La Sapienza’, implementing the specific software SimaPro 5·1 regarding the life‐cycle assessment (LCA) methodology applied. In this paper electrical and thermal energy output results for PV and PV/T systems are given, focusing on their performance improvements and environmental impact, considering their construction and operation requirements. The new outcome of the study was that the glazed type PV/T systems present optimum performance regarding energy, cost and LCA results. Copyright © 2005 John Wiley & Sons, Ltd.     

40% efficient sunlight to electricity conversion

Increasing sunlight conversion efficiency is a key driver for on‐going solar electricity cost reduction. For photovoltaic conversion, the approach most successful in increasing conversion efficiency is to split sunlight into spectral bands and direct each band to a dedicated solar cell of an appropriate energy bandgap to convert this band efficiently. In this work, we demonstrate conversion of sunlight to electricity in a solar collector with an efficiency value above 40% for the first time, using a small 287‐cm² aperture area test stand, notably equipped with commercial concentrator solar cells. We use optical band‐pass filtering to capture energy that is normally wasted by commercial GaInP/GaInAs/Ge triple junction cells and convert this normally wasted energy using a separate Si cell with higher efficiency than physically possible in the original device. The 287‐cm² aperture area sunlight‐concentrating converter demonstrating this independently confirmed efficiency is a prototype for a large photovoltaic power tower system, where sunlight is reflected from a field of sun‐tracking heliostats to a dense photovoltaic array mounted on a central tower. In such systems, improved efficiency not only reduces costs by increasing energy output for a given investment in heliostats and towers but also reduces unwanted heat generation at the central tower. Copyright © 2015 John Wiley & Sons, Ltd.     

Exploiting existing dams for solar PV system installations

Recognizing the issues of land shortage and growing concerns for protecting natural lands, installers and project developers, with the help of scientists and engineers, continuously try to locate alternative spots for photovoltaic (PV) system installations. In the present paper a novel approach is suggested and analysed: installing solar PV systems on the downstream face of existing dams. This approach provides advantages that could favour even large‐scale systems with a capacity of several MWp. First, produced energy could cover water reservoirs' needs supporting energy‐intensive processes as water pumping and treatment in a sustainable manner. Moreover, energy provision to inhabited areas near the dams and the subsequent creation of independent mini grids could mitigate energy poverty. In the case of hydroelectric dams, the so‐created hybrid system (PV‐hydro) could become notably efficient, because the intermittent solar energy would be counterbalanced by the flexibility of hydropower. Finally, we found a notable number of existing water reservoirs in Africa that are either under‐utilized or non‐powered. That unexploited energy potential can also be amplified by PV‐system installation. The analysis included data collection from various sources. Datasets have been cross‐checked and extended in the newly created GIS‐based model, enabling the selection of the most suitable sites in South Africa, taken as case studies. Following their identification, the selected dams have been analysed using the PVGIS tool in order to estimate the annual energy production. The results have been very encouraging, indicating that PV systems on the face of dams are an advantageous option for renewable energy production. © 2015 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.     

The present status and future direction of technology development for photovoltaic power generation in Japan

In 2004 NEDO established the PV Roadmap Toward 2030 PV2030 as a long‐term strategy for PV R&D. In this Roadmap, PV is expected by 2030 to supply approximately 50% of residential electricity consumption (cumulative installed capacity in the range of 100 GW). In terms of economic efficiency, electricity costs are targeted to equal commercial use, approximately 14 Yen/kW h, by 2020 and industrial use, approximately 7 Yen/kW h, by 2030. For future PV systems, it is essential to improve the stand‐alone capabilities of PV system with electricity storage and to develop community‐based PV systems using multi‐function inverters. Advanced technological innovations beyond the existing levels are also essential. Therefore, NEDO is undertaking 2‐year projects for preliminary research to make clear the next R&D of solar cells and PV system technology. Copyright © 2005 John Wiley & Sons, Ltd.     

Renewable Energy Systems With Photovoltaic Power Generators: Operation and Modeling

A substantial increase of photovoltaic (PV) power generators installations has taken place in recent years, due to the increasing efficiency of solar cells as well as the improvements of manufacturing technology of solar panels. These generators are both grid-connected and stand-alone applications. We present an overview of the essential research results. The paper concentrates on the operation and modeling of stand-alone power systems with PV power generators. Systems with PV array-inverter assemblies, operating in the slave-and-master modes, are discussed, and the simulation results obtained using a renewable energy power system modular simulator are presented. These results demonstrate that simulation is an essential step in the system development process and that PV power generators constitute a valuable energy source. They have the ability to balance the energy and supply good power quality. It is demonstrated that when PV array- inverters are operating in the master mode in stand-alone applications, they well perform the task of controlling the voltage and frequency of the power system. The mechanism of switching the master function between the diesel generator and the PV array-inverter assembly in a stand-alone power system is also proposed and analyzed. Finally, some experimental results on a practical system are compared to the simulation results and confirm the usefulness of the proposed approach to the development of renewable energy systems with PV power generators.     

风光互补发电系统的能量管理研究

风光互补发电系统可充分利用本地太阳能和风能资源,具有无污染、供电质量好的优点,是解决偏远地区供电问题的最佳选择之一。为了提高风光互补发电系统的能量利用率和经济性,满足负荷的供电要求,必需对系统能量进行有效的管理。本文提出了一种简洁适用的基于储能环节控制的能量管理策略,并进行了相关的仿真和实验验证。     

Life-cycle assessment of photovoltaic systems: results of Swiss studies on energy chains

The methodology used and results obtained for grid-connected photovoltaic (PV) plants in recent Swiss life-cycle assessment (LCA) studies on current and future energy systems are discussed. Mono- and polycrystalline silicon cell technologies utilized in current panels as well as monocrystalline and amorphous cells for future applications were analysed for Swiss conditions. The environmental inventories of slanted-roof solar panels and large plants are presented. Greenhouse gas emissions from present and future electricity systems are compared. The high electricity requirements for manufacturing determine most of the environmental burdens associated with current photovoltaics. However, due to increasing efficiency of production processes and cells, the environmental performance of PV systems is likely to improve substantially in the future. © 1998 John Wiley & Sons, Ltd.     

PVT光伏光热系统结合地源热泵的应用性研究

基于PVT系统存在太阳能间歇性,无法保证光热转换连续进行的特点,以及存在集热后太阳能电池背板温度过高,导致电池板光伏发电效率下降的缺陷。采用地源热泵与PVT系统相结合,解决了单纯PVT系统在日照不充足情况下热量不能连续稳定供应的问题,提高了系统的热能利用率。同时系统采用定温加热、温差循环技术,有效降低了太阳能电池背板的温度,提高了太阳能电池的光伏发电效率和地源热泵的工作效率以及系统在不同工况下连续运行的可靠性和稳定性。     

A high‐efficiency LPE GaAs solar cell at concentrations ranging from 2000 to 4000 suns

III–V solar cells for terrestrial concentration applications are currently becoming of greater and greater interest. From our experience, concentrations higher than 1000 suns are required with these cells to reduce PV electricity cost to such an extent that this alternative could become cost competitive. In this paper, a single‐junction p/n GaAs solar cell, with efficiencies of 23ċ8 and 22ċ5% at concentration ratios of 2700 and 3600 suns respectively, is presented. This GaAs solar cell is well suited for use with non‐imaging optical concentrators, which possess a large aperture angle. Low‐temperature liquid phase epitaxy (LTLPE) has been the growing technique for the semiconductor structure as an attempt to use a simplified, cheap and clean technique, within a renewable energy perspective. The GaAs solar cell presented is compared with the highest efficiency tandem solar cells at concentration levels exceeding 1000 suns. The GaAs solar cell performance maintains high efficiencies up to 4000 suns, while tandem cells seem to drop very quickly after reaching their maximum. Therefore, single‐junction GaAs solar cells are a good candidate for operating at very high concentrations, and LPE is able to supply these high‐quality solar cells to work within terrestrial concentration systems, the main objective of which is the reduction of PV electricity costs. Copyright © 2003 John Wiley & Sons, Ltd.     

Design and Numerical Simulation of a Symbiotic Thermoelectric Power Generation System Fed by a Low-Grade Heat Source

All liquid heating systems, including solar thermal collectors and fossil-fueled heaters, are designed to convert low-temperature liquid to high-temperature liquid. In the presence of low- and high-temperature fluids, temperature differences can be created across thermoelectric devices to produce electricity so that the heat dissipated from the hot side of a thermoelectric device will be absorbed by the cold liquid and this preheated liquid enters the heating cycle and increases the efficiency of the heater. Consequently, because of the avoidance of waste heat on the thermoelectric hot side, the efficiency of heat-to-electricity conversion with this configuration is better than that of conventional thermoelectric power generation systems. This research aims to design and analyze a thermoelectric power generation system based on the concept described above and using a low-grade heat source. This system may be used to generate electricity either in direct conjunction with any renewable energy source which produces hot water (solar thermal collectors) or using waste hot water from industry. The concept of this system is designated “ELEGANT,” an acronym from “Efficient Liquid-based Electricity Generation Apparatus iNside Thermoelectrics.” The first design of ELEGANT comprised three rectangular aluminum channels, used to conduct warm and cold fluids over the surfaces of several commercially available thermoelectric generator (TEG) modules sandwiched between the channels. In this study, an ELEGANT with 24 TEG modules, referred to as ELEGANT-24, has been designed. Twenty-four modules was the best match to the specific geometry of the proposed ELEGANT. The thermoelectric modules in ELEGANT-24 were electrically connected in series, and the maximum output power was modeled. A numerical model has been developed, which provides steady-state forecasts of the electrical output of ELEGANT-24 for different inlet fluid temperatures.     

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.     

Bioinspired Temperature Regulation in Interfacial Evaporation

Human skin shows self‐adaptive temperature regulation through both enhanced heat dissipation in high temperature environments and depressed heat dissipation in cold environments. Inspired by such thermal regulation processes, an interfacial material system with self‐adaptive temperature regulation in the solar‐driven interfacial evaporation system, which can exhibit automatic temperature oscillation to enable pyroelectricity generation while producing water vapor, is reported. The bioinspired interface system is designed with the combination of a thermochromism‐based temperature regulator consisting of tungsten‐doped vanadium dioxide nanoparticles and a polymeric pyroelectric thin film of polyvinylidene fluoride. Under the simulated solar illumination with power density of 1.1 kW m^?2, the bioinspired interfacial evaporation system achieves a self‐adaptive temperature oscillation with the maximum temperature difference of ≈7 °C and this system can simultaneously generate water vapor as well as electricity with an evaporation efficiency of 71.43% and a maximum output electrical power density of 104 µW m^?2, respectively. The study demonstrates a design of thermal management at the interface of solar‐driven evaporation system to exhibit a self‐adaptive temperature oscillation and offers an alternative approach for the multifunctional harvesting of solar energy.     

MicroFab wins NSF award for organic PV

Texas-based MicroFab Technologies has been awarded a National Science Foundation Small Business Innovation Research (SBIR) program grant for its project on fabrication of organic PV solar panels using inkjet technology.This is a short news story only. Visit www.re-focus.net for the latest renewable energy industry news.     

UCSY acquiring GiraSOLAR,contract for Israeli subsidiary

Miami-based Universal Communication Systems Inc (UCSY) has entered into a ‘letter of intent’ to acquire an initial 51% ownership position in GiraSOLAR BV, a Dutch solar technology developer that makes and markets PV panels and other PV energy-producing systems and products. Meanwhile, Israel-based Millennium Electric TOU Inc, a recently acquired subsidiary of UCSY, has received a contract from the City of Herzliah in Israel to build and install PV panels and systems to provide solar/electric power for traffic lights, lampposts and other city-wide projects.Visit www.re-focus.net for the latest renewable energy industry news