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[en] This paper reports that most electronic equipment today uses a central power supply: there is a single location where the main source of input power is converted to the required system voltages. Distributed power architectures replace central power sources with one bulk power supply that is converted to the required voltages by DC/DC converters at the point of need. This system is capable of serving any complex system applications with requirements for multiple power and voltage levels, light weight, or battery back-up. To use central power systems, the designer typically builds in central power supplies that deliver 5, 12, and 15 volts: a central filtering and thermal management system, and wiring that links the supplies to the board which require the power. The distributed power version of the same systems would use one bulk supply. If a board needs multiple voltages, converters with two or three outputs are used rather tan a single output converter. In a distributed power system, the converters are placed on the board to which they are supplying power
[en] Hybrid power towers offer a number of advantages over solar-only power tower systems for early commercial deployment of the technology. These advantages include enhanced modularity, reduced financial and technical risks, and lower energy costs. With the changes in the domestic and world markets for bulk power, hybrid power towers are likely to have the best opportunities for power projects. This paper discusses issues that are likely to be important to the deployment of hybrid power towers in the near future. A large number of alternative designs are possible, and it is likely that there is no single approach that can be considered best or optimal for all project opportunities. The preferred design will depend on the application, as well as the unique objectives and perspectives of the person evaluating the design
[en] This report utilizes the results of the Solar Two project, as well as continuing technology development, to update the technical and economic status of molten-salt power towers. The report starts with an overview of power tower technology, including the progression from Solar One to the Solar Two project. This discussion is followed by a review of the Solar Two project--what was planned, what actually occurred, what was learned, and what was accomplished. The third section presents preliminary information regarding the likely configuration of the next molten-salt power tower plant. This section draws on Solar Two experience as well as results of continuing power tower development efforts conducted jointly by industry and Sandia National Laboratories. The fourth section details the expected performance and cost goals for the first commercial molten-salt power tower plant and includes a comparison of the commercial performance goals to the actual performance at Solar One and Solar Two. The final section summarizes the successes of Solar Two and the current technology development activities. The data collected from the Solar Two project suggest that the electricity cost goals established for power towers are reasonable and can be achieved with some simple design improvements
[en] Distributed generation units are desirable from an environmental point of view but also have an impact on the costs of electricity grids at the distribution and transmission level. Therefore, investment planning has to consider all benefits and costs of DG to build DG sources at sites where they are economically efficient. Unfortunately, this is not an easy task in an unbundled industry where distribution and generation of electricity are not planned by one single institution. For this reason, this article analyses possible policy options for giving incentives to distributed generation and focuses on the long-term investment signals related to DG.
[en] The paper summarizes the economical conclusions of the 6th Symposium on Solar Thermal Concentrating Technologies which take place at Mojacar (Almeria). Parabolic throughs, Central Receiver Systems, dish stirling and Solar chimneys will commercial utilization by the year 2000. Levalized Energy Cost (Solar) is still higher than conventional (coal). Only the utilization of environmental parameters like ''CO2 avoided'' may contribute to market penetration. Concerning siting, it becomes clear that only those countries below 40 degree latitude, (Madrid, Nepal, Ankara) are acceptable. A desregulation of the electrical market is necessary for solar penetration, mainly in developing countries
[en] Modern industrial plants are characterized by their large size and higher complexity of the processes involved in their operations.The real time monitoring systems of theses plants must be used a distributed architecture.Due to the pressure of competitive markets, an efficient adaptability to changes must be present in the plants.Modifications in the plants due to changes in the lay-out, the introduction of newer supervision, control and monitoring technologies must not affect the integrity of the systems.The aim of this work is give an introduction to the agent-based technology and analyze it advantage for the development of a modern monitoring system
[en] Highlights: • Model developed for cavity receivers for design and off-design performance analysis. • Receiver performance degraded with increased receiver inlet temperature. • Receiver control strategies were found to alter the inlet temperature and DNI limits. • A combined control approach was proposed to maximize receiver operation range. • Off-design receiver efficiency correlations are provided for these strategies. - Abstract: Solar irradiation is intermittent, but concentrated solar thermal (CST) plants are typically designed and analyzed solely based on their steady design point. Unlike coal power plants, however, CST plants frequently experience thermal loads well above and below their rated design point, leading to off-design operation for much of the operational year. Importantly, if a latent heat thermal energy storage (LHTES) system is employed, the receiver inlet temperature can vary under these conditions. To date, there is a clear lack of knowledge for how to handle off-design conditions in terms of developing appropriate control strategies to maximize the receiver thermal output and its operational region. In this study, a thermal model was developed and validated that is suitable for design/off-design performance analyses of molten salt cavity receivers in both steady state and transient conditions. The study investigated two control strategies – a fixed receiver flow rate (FF) and fixed receiver outlet temperature (FT) – for their off-design performance in each of two off-design operational modes (storage and non-storage). Solar field utilization (SFU) is variable in non-storage mode, but in the storage mode, it is whether variable or fixed at design point (SFU = 1). The feasible operating region in this study refers to the zone restricted by maximum allowable operational parameters defined based on design point analysis, mainly maximum receiver outlet temperature, maximum flow rate, and maximum receiver surface temperature. Through this analysis, it was found that receiver inlet temperatures above the design point (560 K) degrade the receiver performance in both control strategies and under all operational modes. The results also revealed that the maximum allowable receiver inlet temperature that maintains the receiver operation inside the feasible region could not go beyond ∼700 K or 600 K with the FF and FT strategies (in the storage mode with variable or fixed SFU), respectively. These values also indicate the charging cut-off temperature for the fluid flowing out in LHTES systems. In the non-storage mode, the receiver inlet temperature is remained constant at design point by varying the SFU over the time. While the design point direct normal irradiation (DNI) was 900 W m"−"2, the maximum allowable DNI is 700 W m"−"2 and 500 W m"−"2 with the FF and FT strategies, respectively. These results motivate a hybrid control strategy that switches between the FF and FT strategies to maximize the performance and the number of operational hours of a CST plant during the day. As a final aspect of this study, off-design receiver efficiency correlations are developed that can be used in any simulation environment to accurately predict receiver performance.
[en] This report describes a project by Science Applications International Corporation and its subcontractors Boeing/Rocketdyne and Bechtel Corp. to develop manufacturing technology for production of SAIC stretched membrane heliostats. The project consists of three phases, of which two are complete. This first phase had as its goals to identify and complete a detailed evaluation of manufacturing technology, process changes, and design enhancements to be pursued for near-term heliostat markets. In the second phase, the design of the SAIC stretched membrane heliostat was refined, manufacturing tooling for mirror facet and structural component fabrication was implemented, and four proof-of-concept/test heliostats were produced and installed in three locations. The proposed plan for Phase III calls for improvements in production tooling to enhance product quality and prepare increased production capacity. This project is part of the U.S. Department of Energy's Solar Manufacturing Technology Program (SolMaT)
[en] This guide provides advice to the developers and operators of small distributed generation plant (including microgenerators) in the UK about the practical issues associated with connecting their plant and trading their output. Particular attention is given to sales revenues and how to access these revenue streams, including the mechanisms for purchasing Renewable Obligation Certificates (ROCs). The guide clarifies key terms, explains the wholesale trading system and provides an overview of sales opportunities (including ROCs and Levy Exemption Certificates (LECs)). Requirements on small distributed generation (including licensing, claiming class exemptions and metering) are described and the commercial aspects of connection (including the recent reduction in the barriers to connection) examined. Microgeneration (ie generators below 10 kW) issues are covered in their own chapter. The six appendices contain: background information about the industry; a list of purchasers of electricity from small distributed generators; descriptions of the generation, transmission and supply industries; information about industry standards and their governance; the role of government departments and institutions; and a glossary and other links
[en] 'Full text:' A long term solution to pollution and resource depletion problems requires addressing at least three issues: increasing the efficiency of energy conversion systems, optimizing the use of currently available energy sources and expanding the use of clean energy vectors. The use of fuel cells as energy vector for automobile and residential applications is promising alternatives for clean energy production. The aim of this work is to study interactions between the fuel cell stack, the uninterruptible power systems, and the control systems. The best strategies and topologies for optimal operation conditions of these systems for distributed power systems will also be determined. To reach this aim, three main points are being studied: development of a detailed dynamic fuel cell model for real-time operation conditions, where the main transient phenomena are modeled and analyzed; optimizing the control of the stack and the auxiliary components; and optimizing the interconnection of the fuel cell systems to the grid in order to protect the network from unwanted consequences of islanding. (author)