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Editor’s Choice : Potential Performance Enhancement of a Solar Combisystem with an Intelligent Controller
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Abstract: Solar thermal systems in residential buildings are generally controlled by two-level controllers, which activate solar thermal or at times with low solar radiation auxiliary energy supply into a thermal storage. Simple controllers do not have any information on actual or expected solar radiation. This leads to interference of auxiliary- and solar heat supply, which reduces the share of solar thermal energy fed into the thermal storage. Increasing accuracy of weather forecast data suggests incorporation of this information in the control algorithm. This work analyzes the maximum potential performance enhancement when applying such an intelligent predictive control. Two solar thermal systems with one auxiliary source respectively are designed in TRNSYS – these systems represent the base case. Further, a number of simulations are conducted with minor variations for the plant parameters – this gives generic results for different system configurations. In addition, each system configuration is altered to mimic the behavior of a plant with intelligent predictive control. Comparison of results indicates an improvement potential up to 10% for annual solar fractions and up to 30% for monthly solar fractions. The performance bound with respect to the annual auxiliary energy savings is approximately 8%. Keywords: Solar thermal, predictive, weather forecast, renewable, auxiliary energy.Download Full Article |
Editor’s Choice : Shaping Porous Materials for Hydrogen Storage Applications: A Review
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Abstract: Development of safe and effective hydrogen storage systems becomes a critical factor for further implementation of fuel cell and hydrogen technologies. Among new approaches aimed at improving the performance of such systems, the concept of porous materials-based adsorptive hydrogen storage is now considered as a long-term solution due to the reversibility, good kinetics and absence of thermal management issues. However, the low packing densities associated with the porous materials such as carbon structure materials, zeolites, metal-organic frameworks lead to the compromised volumetric capacity, potential pipe contaminations and difficulties in handling, when introducing the powdered adsorbents into hydrogen storage systems. Some efforts have been devoted to solve this problem by shaping the porous materials into beads, pellets or monoliths and achieve higher storage densities at more moderate temperatures and pressures. This review will firstly state the essential properties of shaped structures for hydrogen adsorption, and then highlight the recent attributes that potentially can be utilized to shape porous materials into specific configurations for hydrogen storage applications. Later, several testing techniques on structured porous material will be also discussed. Keywords: Porous materials,hydrogen storage systems, shaping process, application-specific configuration, packing density. Download Full Article |
Editor’s Choice : Transmission System Operation Challenges with Large Wind Penetration
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Abstract: The State of California’s renewable energy policies and energy incentives are the main drivers of renewable generation development occurring in the Pacific Northwest. The largest wind integration efforts are happening within the Bonneville Power Administration’s (BPA) Balancing Area (BA). BPA is approaching a 40 percent wind penetration factor. Such a large wind penetration imposes significant challenges on the transmission system operation requiring more system studies in operational time frame. These challenges include needs for additional voltage regulation requiring more switching operations, dealing with higher ramping rates and carrying additional regulation reserve as well as additional difficulty in Columbia River management (river scheduling). This paper discus some of those challenges in more details. Keywords: Bonneville Power Administration (BPA), Balancing Area (BA), System Operating limits (SOL), Transmission System Operation, Wind Penetration..Download Full Article |
Editor’s Choice : Zinc Oxide Nanostructures for Efficient Energy Conversion in Organic Solar Cell
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Abstract: We present a new approach of solution-processed using zinc oxide (ZnO) nanostructures as extraction layer material for organic solar cells. It is low chemical reaction compatibility with all types of organic blends and its good adhesion to both surfaces of ITO/glass substrate and the active layer (blends). Parameters such as the thickness and the morphology of the films were investigated to prove that these factors greatly affect the efficiency of organic solar cells. In this work, ZnO layer with thickness of approximately 53 nm was used as an interlayer to prevent pin-holes between the electrode and the polymer layer. The polymer layer was coated on the ZnO layer with the thickness of about 150 nm. The thick polymer layer will form a non-uniform surface because of the solvent, 1-2dichlorobenzene will etch away some region of the polymer layer and forming pin-holes. ZnO nanostructures layer was used to prevent pin-holes between the polymer layer and electrode. From the surface morphology of ZnO layer, it shows a uniform surface with particle grain size obtained between 50 -100 nm. The presence of the interlayer has a positive effect on the electrical characteristics of the solar cells. It was found that an organic solar cell with thickness less than 150 nm shows the optimum performance with efficiency of 0.0067% and Fill Factor (FF) of about 19.73. Keywords: Nanostructures, extraction layer, pin-holes, poly (3-hexylthiophene) (P3HT), [6,6]-phenyl C61-butyric acid methyl ester (PCBM).Download Full Article |
