Examples of successful architectural integration of PV: Japan

By the end of 2002 more than 1300 MWp of photovoltaic power was installed in industrialized countries worldwide. Of this, approximately 640 MWp, or 48%, is installed in Japan, mainly on buildings. This makes Japan the most prominent country in the field of building-integrated photovoltaics (BIPV). The interest in integration of PV among Japanese architects has increased accordingly, which has resulted in many sophisticated and innovative designs. This short communication introduces four examples of successful architectural integration from different fields. The Japanese government aims at an installed PV capacity of 4820 MWp in 2010. In parallel, the Japanese PV industry needs to develop into a strong sector which is able to operate without direct market support. The role of architects in this process should not only be to increase the volume of building integrated PV, but also to make comprehensive, integral designs, which include sunlight shading, thermal insulation, energy saving, passive use of solar energy, and obviously also photovoltaics. Furthermore, architects could make an important contribution to establishing a new, sustainable urban environment in which BIPV is used on a large scale as a distributed source of energy. This fits well within the new international effort in the framework of the International Energy Agency (IEA), Photovoltaic Power Systems (PVPS), Task 10. Copyright © 2004 John Wiley & Sons, Ltd.     

Power windows. Building-integrated photovoltaics

The author describes how the market for building-integrated photovoltaic systems (BIPV) could be enormous, and many companies are beginning to develop and commercialize specialized BIPV components and systems. Residential and commercial demand will probably be the nearest-term large-scale markets in developed countries. Homes and commercial buildings have a lot of surface area, allowing architects and system designers to displace the cost of conventional materials and labor onto photovoltaic substitutes. Moreover, BIPV produce power at the point of use, eliminating much of the cost and losses of its transmission and distribution. Finally, a building powered in this way trumpets its owners' environmental philosophy and commitment to the world at large. As the technology has moved out of the research laboratory and into commercial applications involving architects and building engineers, it has assumed a progressively more sophisticated, elegant and appropriate shape. BIPV components that take the place of conventional building materials become part of the form and esthetic of the structure, as well as part of a more sustainable future for their owners, for their communities, and for society in general     

Performance assessment of a 2 kWp grid-connected,building-integrated,amorphous silicon photovoltaic installation in Brazil

In September 1997 the first grid-connected, building-integrated photovoltaic (BIPV) installation in Brazil started operating in Florianópolis (27°S). The 2 kWp double-junction amorphous silicon PV system was retrofitted to the Solar Energy Laboratory's (LABSOLAR) building envelope, and connected through four commercial line-commutated inverters to the building's supply network. To demonstrate the architectural features of thin film PV technologies, both semitransparent and opaque modules were mounted on a north-facing, latitude-tilted overhang configuration. BIPV systems operating under the warmer conditions common in Brazil will typically experience relatively high operating temperatures, which suits the a-Si PV technology well. The installation is fully instrumented and is continuously monitored in order to allow the performance assessment of amorphous silicon PV operating at the prevailing conditions. This paper describes the design of the installation and presents system performance data from the first 18 months of operation. Copyright © 2000 John Wiley & Sons, Ltd.     

Photovoltaics in an architectural context

In well‐populated areas, such as western Europe, PV is often integrated into the building envelope. Despite the fact that there are many examples showing that PV can be an aesthetically neutral or visually attractive element in architecture, many BIPV systems display few architectural qualities. But if well applied, PV can increase a building's character and value. Within Task 7 of the IEA PVPS programme a team of experts with an architectural background studied which key requirements needed to be complied with (design criteria for good‐quality PV projects) in order to produce successful PV integration. These criteria are discussed in the article. PV is not automatically considered an indispensable material in architectural terms. This is why, no matter how well it is integrated, PV remains an ‘added’ element. Architects can take this as their starting point and can use one of the design approaches that are presented in the article. These criteria for incorporating PV in the building design and the design criteria for good‐quality PV projects are important to architects and architectural critics in determining why a BIPV project, be it their own design or that of a colleague, is or is not aesthetically pleasing. This offers learning opportunities and reasons for follow‐up or improvement options. Architects who apply PV in a well‐thought‐out way can make their clients very happy, and thereby contribute to a greater acceptance of PV technology. Copyright © 2004 John Wiley & Sons, Ltd.     

Examples of successful architectural integration of PV: Germany

In Germany building‐integrated photovoltaics (BIPV) are developing rapidly, and much progress has been achieved in the past five years. BIPV can be used today in different ways on both existing and new buildings. Architects and designers are discovering BIPV. With the help of custom‐made products available on the German market they are beginning to explore the technical limits of an aesthetic and structural integration of PV in buildings. As a result some exciting high‐profile building projects with PV have been built, for example, the small service pavilion Meereslauschen in Steinhude or the new headquarters building of the Wood Trade Association in Munich. These projects show that the use of PV is very varied and offers opportunities for creative architects. However non‐technical problems still need to be solved to allow a meaningful and widespread application of PV in the built environment. To decrease costs it is essential to develop further standard BIPV components. The aim of such developments should be to replace standard PV modules by products in which PV and structural building elements are melded into one design and structural unit. Copyright © 2004 John Wiley & Sons, Ltd.     

Operational performance of grid‐connected PV systems on buildings in Germany

This paper presents operational performance results of grid‐connected PV systems in Germany, as collected and elaborated for the Photovoltaic Power Systems Programme (PVPS) of the International Energy Agency (IEA). Performance ratios obtained from 235 PV installations in Germany and from 133 PV plants in other countries are compared and discussed. For Germany, a significant rise in PV system performance and reliability was observed for new PV installations due to higher component efficiencies (e.g., inverter) and increased availabilities. There is a lack of long‐term experience in performance and reliability of PV systems, owing to the absence of monitoring programmes. As an outcome of IEA PVPS collaborative work, Task 2 provides reliable and worldwide monitoring performance data and results (www.task2.org). Technical and operational data is available for system planning and comparison, for teaching and training purposes as well as for future developments of financing schemes (e.g., feed‐in‐tariffs) in order to stimulate the PV market. Copyright © 2004 John Wiley & Sons, Ltd.     

Multi-objective optimization for task offloading based on network calculus in fog environments

With the widespread application of wireless communication technology and continuous improvements to Internet of Things (IoT) technology, fog computing architecture composed of edge, fog, and cloud layers have become a research hotspot. This architecture uses Fog Nodes (FNs) close to users to implement certain cloud functions while compensating for cloud disadvantages. However, because of the limited computing and storage capabilities of a single FN, it is necessary to offload tasks to multiple cooperating FNs for task completion. To effectively and quickly realize task offloading, we use network calculus theory to establish an overall performance model for task offloading in a fog computing environment and propose a Globally Optimal Multi-objective Optimization algorithm for Task Offloading (GOMOTO) based on the performance model. The results show that the proposed model and algorithm can effectively reduce the total delay and total energy consumption of the system and improve the network Quality of Service (QoS).     

Multifactor task allocation problem in wireless sensor and actuator networks

Task allocation is an essential part of many military applications of WSAN such as intelligent minefield.The key problem of task allocation decision in these systems for the optimal scheme on task allocation is how to obtain the node-target assignment.Combing with the factors of target’s parameters and node’s own status,the various influence factors of task efficiency were analyzed and the positive and negative indicators were processed by range normalization method separately.The linear-weighted task efficiency function was proposed in the applications of WSAN such as intelligent minefield.It can be utilized as the evaluation index of assignment schemes since it reflected the integrated impact of target’s threat and node’s value on the system more comprehensively.Task efficiency function can be constructed flexibly based on the demand of different multifactor task allocation application.The essence of the problem was how to make node-target assignment to achieve the maximum task efficiency of the whole system.This problem turned into assignment problem and can be solved.Finally,an application was implemented to demonstrate this scheme.The results show that the model is suitable for small-scale multifactor task allocation problem in intelligent minefield system.     

Latest Progress on Photoabsorbent Materials for Multifunctional Semitransparent Organic Solar Cells

Semi-transparent organic solar cells (ST-OSCs) have revolutionized the field of photovoltaics (PVs) due to their unique abilities, such as transparency and color tunability, and have transformed normal power-harvesting OSC devices into multifunctional devices, such as building-integrated photovoltaics, agrivoltaics, floating photovoltaics, and wearable electronics. Very recently, ST-OSCs have seen remarkable progress, with a rapid increase in power conversion efficiency from below 7% to 12–14%, with an average visible transparency of 9–25%, especially due to the use of low bandgap semiconductors including polymer donors and non-fullerene acceptors that exhibit absorption in the near-infrared region as photoabsorbent materials. From this perspective, the latest developments in ST-OSCs stemming from the innovations in photovoltaic materials that delivered multifunctional ST-OSCs with top-of-the-line power conversion efficiencies are discussed to shed light on the structure-property relationship between molecular design and current challenges in this cutting-edge research field. Finally, personal perspectives, including research directions for the future use of ST-OSCs in multifunctional applications, are also proposed.     

Influence of the underneath cavity on buoyant‐forced cooling of the integrated photovoltaic panels in building roof: a thermography study

Airflow around building‐integrated photovoltaics (BIPV) has a significant impact on their hygrothermal behavior and degradation. The potential of reducing the temperature of BIPV using an underneath cavity is experimentally and numerically investigated in literature. Most of the models are oversimplified in terms of modeling the impact of 3D flow over/underneath of PV modules, which can result in a non‐uniform surface temperature and consequently a non‐homogenous thermal degradation. Moreover, the simultaneous presence of radiation and convection related to upstream wind, in addition to the combined impact of back‐ventilation and surface convection, is barely addressed in literature. However, these simplifications can result in the unrealistic loading climate conditions. This paper aims to present a unique experimental setup to provide more realistic climate conditions for investigating the ventilation potential of the underneath. The setup consists of a solar simulator and a building prototype with installed PV, placed inside an atmospheric wind tunnel to control upstream wind velocity. Thermography is performed using an infrared camera to monitor the surface temperature of the BIPV. The potential of an underneath cavity with various cavity heights and PV arrangement is further investigated in this paper. The outcome would be eventually useful in the development of practical guidelines for BIPV installation. Copyright © 2013 John Wiley & Sons, Ltd.     

PV trends report available from IEA

The Photovoltaic Power Systems Programme of the International Energy Agency (IEA) has recently published its Task 1 report, Trends in photovoltaic applications. Survey report of selected IEA countries between 1992 and 2002, now available from the IEA-PVPS website.Visit www.re-focus.net for the latest renewable energy industry news     

Façade–integrated photovoltaics: a life cycle and performance assessment case study

The Solaire Building has the first façade building‐integrated photovoltaic (BIPV) array in New York City. This paper presents the life cycle impacts of the Solaire BIPV and extrapolates its performance to other façade systems. Engineering diagrams, detailed material inventories and 5 years of irradiation and actual performance data in 15‐min intervals offer insights into current BIPV construction and performance. The Solaire BIPV employs waste‐stream monocrystalline silicon wafers. Correspondingly, zero energy input was allocated to this BIPV from wafer production, resulting to a very low energy payback time (EPBT) and global warming potential burden (0.8 years and −10.2 g CO₂/kWh, respectively). A negative EPBT results from subtracting the impact of the thermally and structurally equivalent concrete and brick wall that the BIPV array replaced. Data from current photovoltaic‐dedicated Si wafer supply were also used; these resulted with an EPBT of 3.8 years and a global warming potential of 61 g CO₂/kWh. The performance ratio and EPBT of the Solaire system were compared with those in the International Energy Agency Photovoltaic Power Systems Task 2 inventory database. The drawback of façade BIPV is its vertical orientation, receiving lower incident irradiation than rooftop and ground installations. Nevertheless, BIPV offers two main advantages over such installations: it does not require any ‘virgin’ land for its operation, and it replaces structural units, thus avoiding the cost, embodied energy and corresponding emissions related to those. We detail herein how the replacement of traditional cladding materials can offset the performance drawback of BIPV, in terms of environmental burden and EPBT. Copyright © 2012 John Wiley & Sons, Ltd.     

Application task guides

Task guides provide a simple mechanism to reuse experiences in an application system and expand an online HTML-based help system to suit a particular application domain. We propose a task guide and implement it in a medical application system called Discover.     

Multi-stage online task assignment driven by offline data under spatio-temporal crowdsourcing

In the era of the Internet of Things (IoT), the crowdsourcing process is driven by data collected by devices that interact with each other and with the physical world. As a part of the IoT ecosystem, task assignment has become an important goal of the research community. Existing task assignment algorithms can be categorized as offline (performs better with datasets but struggles to achieve good real-life results) or online (works well with real-life input but is difficult to optimize regarding in-depth assignments). This paper proposes a Cross-regional Online Task (CROT) assignment problem based on the online assignment model. Given the CROT problem, an Online Task Assignment across Regions based on Prediction (OTARP) algorithm is proposed. OTARP is a two-stage graphics-driven bilateral assignment strategy that uses edge cloud and graph embedding to complete task assignments. The first stage uses historical data to make offline predictions, with a graph-driven method for offline bipartite graph matching. The second stage uses a bipartite graph to complete the online task assignment process. This paper proposes accelerating the task assignment process through multiple assignment rounds and optimizing the process by combining offline guidance and online assignment strategies. To encourage crowd workers to complete crowd tasks across regions, an incentive strategy is designed to encourage crowd workers’ movement. To avoid the idle problem in the process of crowd worker movement, a drop-by-rider problem is used to help crowd workers accept more crowd tasks, optimize the number of assignments, and increase utility. Finally, through comparison experiments on real datasets, the performance of the proposed algorithm on crowd worker utility value and the matching number is evaluated.     

Self-Power Consumption Research with the Thermal Effects and Optical Properties of the HCRI-BIPV Window System

The building integrated photovoltaics(BIPV) application is one of the main study topics in the sustainable building field.In this paper,the high color rendering index(HCRI)-BIPV window system is developed to be used in the indoor environmental control,whose module material has appeared to be effective in improving the visible transmittance and reducing the absorption.This paper describes the performance of grid-connected HCRI-BIPV window system with 0.75 kWp capacity installed in an office building for a natural ventilation solution.The experimental results indicate that accumulative power generation of the HCRI-BIPV window system is 157.60 WKh during the 7-month experiment period.For consideration of each evaluated factors,the HCRI-BIPV window system not only offers the passive energy situation for its power loading but also improves the indoor thermal environment by natural ventilation.     

A non‐cooperative game model for reliability‐based task scheduling in cloud computing

Cloud computing is a newly emerging distributed system. Task scheduling is the core research of cloud computing which studies how to allocate the tasks among the physical nodes, so that the tasks can get a balanced allocation or each task's execution cost decreases to the minimum, or the overall system performance is optimal. Unlike task scheduling based on time or cost before, aiming at the special reliability requirements in cloud computing, we propose a non‐cooperative game model for reliability‐based task scheduling approach. This model takes the steady‐state availability that computing nodes provide as the target, takes the task slicing strategy of the schedulers as the game strategy, then finds the Nash equilibrium solution. We also design a task scheduling algorithm based on this model. It can be seen from the experiments that our task scheduling algorithm is better than the so‐called balanced scheduling algorithm.     

建筑集成光伏系统的常见结构及其设计要素

太光伏发电技术是新能源发电技术的重要组成部分。建筑集成光伏(BI PV,Building Integrated Photovoltaic)技术作为光伏发电技术的一种应用形式,有其得天独厚的优势。BIPV系统在结构上可以分为独立光伏发电系统和并网光伏发电系统,系统设计过程中存在一些有别于一般光伏发电系统的设计要素。BIPV系统是未来光伏发电应用的主要发展方向之一,有很大的研究价值。     

A framework for reconfigurable computing: task scheduling andcontext management

Dynamically reconfigurable architectures are emerging as a viable design alternative to implement a wide range of computationally intensive applications. At the same time, an urgent necessity has arisen for support tool development to automate the design process and achieve optimal exploitation of the architectural features of the system. Task scheduling and context (configuration) management become very critical issues in achieving the high performance that digital signal processing (DSP) and multimedia applications demand. This article proposes a strategy to automate the design process which considers all possible optimizations that can be carried out at compilation time, regarding context and data transfers. This strategy is general in nature and could be applied to different reconfigurable systems. We also discuss the key aspects of the scheduling problem in a reconfigurable architecture such as MorphoSys. In particular, we focus on a task scheduling methodology for DSP and multimedia applications, as well as the context management and scheduling optimizations     

Dynamic voltage scaling based energy-minimized partial task offloading in fog networks

Wireless Networks - With the dynamic voltage scaling (DVS) technology, the terminal node (TN) can dynamically adjust its computational speed, thus providing a new way to save energy during task...