Showing papers on "Solar power published in 2005"

Perpetual environmentally powered sensor networks

Abstract: Environmental energy is an attractive power source for low power wireless sensor networks. We present Prometheus, a system that intelligently manages energy transfer for perpetual operation without human intervention or servicing. Combining positive attributes of different energy storage elements and leveraging the intelligence of the microprocessor, we introduce an efficient multi-stage energy transfer system that reduces the common limitations of single energy storage systems to achieve near perpetual operation. We present our design choices, tradeoffs, circuit evaluations, performance analysis, and models. We discuss the relationships between system components and identify optimal hardware choices to meet an application's needs. Finally we present our implementation of a real system that uses solar energy to power Berkeley's Telos Mote. Our analysis predicts the system will operate for 43 years under 1% load, 4 years under 10% load, and 1 year under 100% load. Our implementation uses a two stage storage system consisting of supercapacitors (primary buffer) and a lithium rechargeable battery (secondary buffer). The mote has full knowledge of power levels and intelligently manages energy transfer to maximize lifetime.

Organic-Based Photovoltaics: Toward Low-Cost Power Generation

Abstract: Harvesting energy directly from sunlight using photovoltaic technology is a way to address growing global energy needs with a renewable resource while minimizing detrimental effects on the environment by reducing atmospheric emissions. This issue of MRS Bulletin on “Organic-Based Photovoltaics” looks at a new generation of solar cells that have the potential to be produced inexpensively. Recent advances in solar power conversion efficiencies have propelled organic-based photovoltaics out of the realm of strictly fundamental research at the university level and into the industrial laboratory setting. Fabricated from organic materials—polymers and molecules—these devices are potentially easier to manufacture than current technologies based on silicon or other materials. In this introductory article, we describe the motivation for pursuing research in this field and provide an overview of the various technical approaches that have been developed to date. We conclude by discussing the challenges that need to be overcome in order for organic photovoltaics to realize their potential as an economically viable path to harvesting energy from sunlight.

Design considerations for solar energy harvesting wireless embedded systems

Abstract: Sustainable operation of battery powered wireless embedded systems (such as sensor nodes) is a key challenge, and considerable research effort has been devoted to energy optimization of such systems. Environmental energy harvesting, in particular solar based, has emerged as a viable technique to supplement battery supplies. However, designing an efficient solar harvesting system to realize the potential benefits of energy harvesting requires an in-depth understanding of several factors. For example, solar energy supply is highly time varying and may not always be sufficient to power the embedded system. Harvesting components, such as solar panels, and energy storage elements, such as batteries or ultracapacitors, have different voltage-current characteristics, which must be matched to each other as well as the energy requirements of the system to maximize harvesting efficiency. Further, battery non-idealities, such as self-discharge and round trip efficiency, directly affect energy usage and storage decisions. The ability of the system to modulate its power consumption by selectively deactivating its sub-components also impacts the overall power management architecture. This paper describes key issues and tradeoffs which arise in the design of solar energy harvesting, wireless embedded systems and presents the design, implementation, and performance evaluation of Heliomote, our prototype that addresses several of these issues. Experimental results demonstrate that Heliomote, which behaves as a plug-in to the Berkeley/Crossbow motes and autonomously manages energy harvesting and storage, enables near-perpetual, harvesting aware operation of the sensor node.

Performance parameters for grid-connected PV systems

Abstract: The use of appropriate performance parameters facilitates the comparison of grid-connected photovoltaic (PV) systems that may differ with respect to design, technology, or geographic location. Four performance parameters that define the overall system performance with respect to the energy production, solar resource, and overall effect of system losses are the following: final PV system yield, reference yield, performance ratio, and PVUSA rating. These performance parameters are discussed for their suitability in providing desired information for PV system design and performance evaluation and are demonstrated for a variety of technologies, designs, and geographic locations. Also discussed are methodologies for determining system a.c. power ratings in the design phase using multipliers developed from measured performance parameters.

Understanding renewable energy systems

Abstract: Beginning with an overview of renewable energy sources including biomass, hydroelectricity, geothermal, tidal, wind and solar power, this book explores the fundamentals of different renewable energy systems. The main focus is on technologies with high development potential such as solar thermal systems, photovoltaics and wind power. This text not only describes technological aspects, but also deals consciously with problems of the energy industry. In this way, the topics are treated in a holistic manner, bringing together maths, engineering, climate studies and economics, and enabling readers to gain a broad understanding of renewable energy technologies and their potential. The book also contains a free CD-ROM resource, which includes a variety of specialist simulation software and detailed figures from the book. Following a successful edition in German and in response to growing demand for high quality, user-friendly textbooks on renewable energy, the author has prepared a revised version of this classic text in English. Understanding Renewable Energy Systems is an ideal companion for students of renewable energy at universities or technical colleges - on courses such as renewable energy, electrical engineering, engineering technology, physics, process engineering, building engineering, environment, applied mechanics and mechanical engineering - as well as scientists and engineers in research and industry.

Wind and Solar Power Systems: Design, Analysis, and Operation, Second Edition

Abstract: The search for clean, renewable energy sources has yielded enormous growth and new developments in these technologies in a few short years, driving down costs and encouraging utilities in many nations, both developed and developing, to add and expand wind and solar power capacity. The first, best-selling edition of Wind and Solar Power Systems prov

Using HOMER Software, NREL's Micropower Optimization Model, to Explore the Role of Gen-sets in Small Solar Power Systems; Case Study: Sri Lanka

Abstract: This paper discusses using HOMER Software, NREL's Micropower Optimization Model, to explore the role of gen-sets in small solar power systems in Sri Lanka

Sustainable production of solar electricity with particular reference to the Indian economy

Abstract: Fossil fuel reserves are diminishing rapidly across the world, intensifying the stress on existing reserves day-by-day due to increased demand. Not only that, fossil fuels, presently contributing to 80% of world primary energy, are inflicting enormous impacts on environment. Climatic changes driven by human activities, in particular the production of greenhouse gas emissions, directly impact the environment. Energy sector has a key role in this regard since energy during its production, distribution and consumption is responsible for producing environmentally harmful substances. A secure and accessible supply of energy is thus very crucial for the sustainability of modern societies. There is an urgent need for a quicker switch over of energy systems from conventional to renewables that are sustainable and can meet the present and projected world energy demand. Solar power is one of the most promising renewables. It is reliable and less vulnerable to changes in seasonal weather patterns. Hydrogen, in the capacity of energy vector, is expected to be the optimum solution for intermittency and storage of energy produced by renewables. Thus, coupled with hydrogen as an energy carrier, solar energy has a large potential to become the fuel of the future. The present study is aimed to explore such potential for India in 2025. India is expected to have a high growth rate in energy demand over the coming years due to its huge population and rapid economic development. By the year 2020, the country's demand for commercial energy is expected to increase by a factor of 2.5. Presently, more than 90% of the energy demand is met by fossil fuels, in spite of the fact that India has limited fossil fuel resources as compared to global reserves. By the year 2020, India, presently the world's sixth largest energy consumer, is expected to meet 75% of its oil and gas needs by imports. Being an energy deficient country, it has not been able to keep up with demand, leading to power shortages and supply interruptions. The growing gap between the demand and supply of energy, and environmental externalities associated with fossil fuel require immediate and substantial increases in electric power generation and transmission capacities, and exploitation of new avenues of energy supply that are more stable and environment friendly. The geographic location of India makes it a strong candidate for harnessing solar energy. Thus, solar PV is a potential technology to meet India's future energy demand and its associated environmental challenges. The present work proposes solar hydrogen based energy network to meet the future energy demand for the major cities of India in a sustainable way. In the proposed energy network, solar PV produced electricity is to be utilized to meet the energy demand during day hours. The solar generated electricity that is excessive of demand is to be stored in the form of hydrogen to be utilized during nocturnal hours and prolonged overcast conditions. A modular approach has been adopted for the purposed energy network to meet the year 2025 demand of six major cities of India: Chennai, Delhi, Jodhpur, Kolkata, Mumbai and Trivandrum. Present as well as projected cost scenarios for 2025 have been provided for all the proposed technologies to evaluate the economical viability of the energy network under study. Based on the futuristic trends, it is foreseen that by the year 2025, the PV electricity would be more economical than the fossil fuel electricity.

Model of photovoltaic cell circuits under partial shading

Abstract: The PV-cell and natural energy production systems have been much attracted. Together with global warning and extensive applications of solar power electric generation, defects on PV-cell under the partial shading become interesting technical issue. This paper investigates the equivalent circuit model and its characteristics under the partial shading condition. And we have clarified the mechanism of PV-cell under the partial shading. As the extension of these considerations, we have proposed the new MPPT method (maximal power point tracking) for the sake of drastic energy generation improvement

Designing with Solar Power: A Source Book for Building Integrated Photovoltaics (BiPV)

Abstract: Designing with Solar Power is the result of international collaborative research and development work carried out within the framework of the International Energy Agency's Photovoltaic Power Systems Programme (PVPS) and performed within its Task 7 on 'Photovoltaic power systems in the built environment'. Each chapter of this precisely detailed and informative book has been prepared by an international expert in a specific area related to the development, use and application of building-integrated photovoltaics (BiPV). Chapters not only cover the basics of solar power and electrical concepts, but also investigate the ways in which photovoltaics can be integrated into the design and creation of buildings equipped for the demands of the 21st century. The potential for BiPV, in both buildings and other structures, is explored together with broader issues such as market deployment, and international marketing and government strategies. In addition, more than 20 contemporary international case studies describe in detail how building-integrated photovoltaics have been applied to new and existing buildings, and discuss the architectural and technical quality, and the success of various strategies. Packed with photographs and illustrations, this book is an invaluable companion for architects, builders, designers, engineers, students and all involved with the exciting possibilities of building-integrated photovoltaics.

Optical Durability of Candidate Solar Reflectors

Abstract: Concentrating solar power (CSP) technologies use large mirrors to collect sunlight to convert thermal energy to electricity. The viability of CSP systems requires the development of advanced reflector materials that are low in cost and maintain high specular reflectance for extended lifetimes under severe outdoor environments. The long-standing goals for a solar reflector are specular reflectance above 90% into a 4 mrad half-cone angle for at least 10 years outdoors with a cost of less than $13.8/m 2 (the 1992 $10.8/m 2 goal corrected for inflation to 2002 dollars) when manufactured in large volumes. Durability testing of a variety of candidate solar reflector materials at outdoor test sites and in laboratory accelerated weathering chambers is the main activity within the Advanced Materials task of the CSP Program at the National Renewable Energy Laboratory (NREL) in Golden, Colorado. Test results to date for several candidate solar reflector materials will be presented. These include the optical durability of thin glass, thick glass, aluminized reflectors, front-surface mirrors, and silvered polymer mirrors. The development, performance, and durability of these materials will be discussed. Based on accelerated exposure testing the glass, silvered polymer, and front-surface mirrors may meet the 10 year lifetime goals, but at this time because of significant process changes none of the commercially available solar reflectors and advanced solar reflectors have demonstrated the 10 year or more aggressive 20 year lifetime goal.

Artificial neural network model for prediction solar radiation data: application for sizing stand-alone photovoltaic power system

Abstract: The prediction of daily global solar radiation data is very important for many solar applications, possible application can be found in meteorology, renewable energy and solar conversion energy. In this paper, we investigate using radial basis function (RBF) networks in order to find a model for daily global solar radiation data from sunshine duration and air temperature. This methodology is considered suitable for prediction time series. Using the database of daily sunshine duration, air temperature and global solar radiation data corresponding to typical reference year (TRY). A RBF model has been trained based on 300 known data from TRY, in this way, the network was trained to accept and even handle a number of unusual cases. Known data were subsequently used to investigate the accuracy of prediction. Subsequently, the unknown validation data set produced very accurate estimation, with the mean relative error (MRE) not exceed 1.5% between the actual and predicted data, also the correlation coefficient obtained for the validation data set is 98.9%, these results indicates that the proposed model can successfully be used for prediction and modeling of daily global solar radiation data from sunshine duration and air temperature. An application for sizing of stand-alone PV system has been presented in this paper in order to show the importance of this modeling.

Modelling and Design of Direct Solar Steam Generating Collector Fields

Abstract: The direct steam generation (DSG) is an attractive option regarding the economic improvement of parabolic trough technology for solar thermal electricity generation in the multi megawatt range. According to Price, H., Lupfert, E., Kearney, D., Zarza, E., Cohen, G., Gee, R. Mahoney, R., 2002, Advances in Parabolic Trough Solar Power Technology, J. Sol. Energy Eng., 124 and Zarza, E., 2002, DISS Phase II-Final Project Report, EU Project No. JOR3-CT 980277 a 10% reduction of the LEC is expected compared to conventional SEGS like parabolic trough power plants. The European DISS project has proven the feasibility of the DSG process under real solar conditions at pressures up to 100 bar and temperatures up to 400°C in more than 4000 operation hours (Eck, M., Zarza, E., Eickhoff, M., Rheinlander, J., Valenzuela, L., 2003, Applied Research Concerning the Direct Steam Generation in Parabolic Troughs, Solar Energy 74, pp. 341-351). In a next step the detailed engineering for a precommercial DSG solar thermal power plant will be performed. This detailed engineering of the collector field requires the consideration of the occurring thermohydraulic phenomena and their influence on the stability of the absorber tubes.

Flexible integrated photovoltaic roofing membrane and related methods of manufacturing same

Abstract: Disclosed herein are flexible, solar powered photovoltaic (PV) integrated roofing membrane and related methods of manufacturing such a membrane. The disclosed membrane and methods beneficially provide solar power to structures in either off grid or on-grid connections. The roofing membrane may comprise multiple membrane strips or members having electrically interconnected photovoltaic solar elements. The membrane members preferably have distinct patterns for the solar elements located thereon that provide for coverage of entire sections, upon installation, as well as accommodate interconnections between the solar elements. Moreover, the membrane will appreciate the numerous types of patterns to achieve such purposed of full coverage and electrical coupling.

Solar power generation system

Abstract: An economical solar generator system is provided wherein the solar energy collector is constructed from a plurality of heat exchangers of the kind used as evaporators in automobile air conditioners. The solar generator system includes a plurality of said heat exchangers connected to receive incoming liquefied refrigerant under pressure. The number of such heat exchangers is sufficient to collect solar energy sufficient to induce a phase change from a liquid to a gas state. The solar generator system also includes an air motor and an electric generator. The air motor is coupled to the outflow heated gas from the plurality of heat exchangers. The air motor is rotated by the heated gas. The electrical generator is coupled to the air motor so that rotation of said air motor causes rotation of said generator.

More profit with less carbon.

Abstract: Offers a look at the benefits of focusing on energy efficiency for the protection of Earth's climate. Claim that climate protection would reduce costs; List of businesses that have boosted production while cutting energy use and greenhouse gas emissions, including chemical manufacturer DuPont; Importance of switching to fuels that emit less carbon; Availability of energy-efficient products such as light bulbs and electronic speed controls; Discussion of home heating systems and thermal insulation; Report that transportation consumes 70 percent of U.S. oil and generates a third of the nation's carbon emissions; Improvements that could be made to transportation's efficiency by combining lightweight materials with innovations in propulsion and aerodynamics; Increase of alternatives to coal-fired power plants, including solar power and wind power. INSET: CROSSROADS FOR ENERGY.

Photovoltaic-embedded surface

Abstract: An integrated solar power system that provides electricity to external electrical devices has a trafficable surface formed from a plurality of roadway panels arranged with respect to each other. Each roadway panel has a solar energy collector, a layer of translucent and protective material covering the solar energy collector, the material being sufficiently translucent to allow passage of light therethrough for absorption of light by said solar energy collector and sufficiently protective to withstand the loads and the impact of pedestrian and vehicular traffic and having a sufficient coefficient of friction to allow passage thereon of pedestrians and vehicles without slippage, and an electrical conductor for extracting electrical power from the solar energy collector. Each roadway panel may be modularly connected to others. The roadway panel provides solar energy to at least one eternal electrical device or solar power storage member.

Impacts of energy storage on power system reliability performance

Abstract: Energy storage is an important feature in renewable energy based power systems especially in small isolated applications. This paper describes a sequential Monte Carlo simulation method for incorporating energy storage capability in generating capacity adequacy evaluation of such systems. Time series models were used to simulate the generation/load characteristics of a power system. Energy storage state time series were obtained from the load time series and the available generation time series and incorporated in the overall system adequacy evaluation. The impact of energy storage on power system reliability performance is investigated using example systems containing wind energy and/or solar energy

Solar power source with maximum power-point tracking

Abstract: A solar array power source is provided that automatically operates at its maximum power point despite changes in irradiance and array temperature.

A "real world" examination of PV system design and performance

Abstract: There is no substitute for experience when it comes to designing a PV power system. Almost all system requirements are unique in some way and the ability to anticipate the on-site challenges and design the system accordingly can help ensure an optimum system performance. It's the system performance that is measured and noted by the system user, not the solar panel performance. Although the solar panel usually gets blamed when performance is less than expected, it is usually a system problem such as a poor choice of components, inefficient system architecture, poor installation techniques, or possibly, the wrong PV technology for the application. Especially for the larger PV systems, the key challenge is to design a system that matches the requirements, the environment, location and application, resulting in a high level of performance.

Micro-optics concentrator for solar power satellites

Abstract: There is an increasingly intense need to harness solar energy due to an ever growing shortage of conventional energy sources, The instant invention is concerned with method and apparatus for solar concentrator micro-mirrors on solar power satellites and the moon to focus and reflect large quantities of solar energy. Method and apparatus are taught for directly reflecting solar energy to the Earth; reflecting solar energy to a microwave converter in space which transmits microwave energy to the Earth; and reflecting solar energy to a laser radiation converter which beams laser radiation to the Earth. The concentrated energy received at the Earth may be converted directly to electricity or indirectly by thermo-mechanical means. The advantages and disadvantages of the different means of sending such concentrated energy to the Earth are discussed. A particularly important objective of this invention is the focussing of sunlight for solar power conversion and production. The instant invention can contribute to the goal of achieving environmentally clean solar energy on a large enough scale to be competitive with conventional energy sources.