The Experts below are selected from a list of 114 Experts worldwide ranked by ideXlab platform
Stephan Förster - One of the best experts on this subject based on the ideXlab platform.
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Ordered Particle Arrays via a Langmuir Transfer Process: Access to Any Two-Dimensional Bravais Lattice.
Langmuir, 2018Co-Authors: Miriam E. J. Hummel, Christian Stelling, Bernd A. F. Kopera, Fabian A. Nutz, Matthias Karg, Markus Retsch, Stephan FörsterAbstract:We demonstrate how to directly transform a close-packed hexagonal colloidal monolayer into nonclose-packed particle Arrays of any two-dimensional symmetry at the air/water interface. This major advancement in the field of nanoparticle self-assembly is based on a simple one-dimensional stretching step in combination with the particle Array Orientation. Our method goes far beyond existing strategies and allows access to all possible two-dimensional Bravais lattices. A key element of our work is the possibility to macroscopically stretch a particle Array in a truly one-dimensional manner, which has not been possible up to now. We achieve this by stretching the nanoparticle Array at an air/water interface during the transfer process. The degree of stretching is simply controlled by the wettability of the transfer substrate. To retain the symmetry of the transferred structure, the capillary forces upon drying have to be circumvented. We demonstrate two concepts based on thermal fixation for this. It allows for the first time to fabricate nonclose-packed, nonhexagonal colloidal monolayers on a macroscopic length scale.
Miriam E. J. Hummel - One of the best experts on this subject based on the ideXlab platform.
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Ordered Particle Arrays via a Langmuir Transfer Process: Access to Any Two-Dimensional Bravais Lattice.
Langmuir, 2018Co-Authors: Miriam E. J. Hummel, Christian Stelling, Bernd A. F. Kopera, Fabian A. Nutz, Matthias Karg, Markus Retsch, Stephan FörsterAbstract:We demonstrate how to directly transform a close-packed hexagonal colloidal monolayer into nonclose-packed particle Arrays of any two-dimensional symmetry at the air/water interface. This major advancement in the field of nanoparticle self-assembly is based on a simple one-dimensional stretching step in combination with the particle Array Orientation. Our method goes far beyond existing strategies and allows access to all possible two-dimensional Bravais lattices. A key element of our work is the possibility to macroscopically stretch a particle Array in a truly one-dimensional manner, which has not been possible up to now. We achieve this by stretching the nanoparticle Array at an air/water interface during the transfer process. The degree of stretching is simply controlled by the wettability of the transfer substrate. To retain the symmetry of the transferred structure, the capillary forces upon drying have to be circumvented. We demonstrate two concepts based on thermal fixation for this. It allows for the first time to fabricate nonclose-packed, nonhexagonal colloidal monolayers on a macroscopic length scale.
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Ordered Particle Arrays via a Langmuir Transfer Process: Access to Any Two-Dimensional Bravais Lattice
2018Co-Authors: Miriam E. J. Hummel, Christian Stelling, Bernd A. F. Kopera, Fabian A. Nutz, Matthias Karg, Markus Retsch, Stephan FörsterAbstract:We demonstrate how to directly transform a close-packed hexagonal colloidal monolayer into nonclose-packed particle Arrays of any two-dimensional symmetry at the air/water interface. This major advancement in the field of nanoparticle self-assembly is based on a simple one-dimensional stretching step in combination with the particle Array Orientation. Our method goes far beyond existing strategies and allows access to all possible two-dimensional Bravais lattices. A key element of our work is the possibility to macroscopically stretch a particle Array in a truly one-dimensional manner, which has not been possible up to now. We achieve this by stretching the nanoparticle Array at an air/water interface during the transfer process. The degree of stretching is simply controlled by the wettability of the transfer substrate. To retain the symmetry of the transferred structure, the capillary forces upon drying have to be circumvented. We demonstrate two concepts based on thermal fixation for this. It allows for the first time to fabricate nonclose-packed, nonhexagonal colloidal monolayers on a macroscopic length scale
Michael E Webber - One of the best experts on this subject based on the ideXlab platform.
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solar pv integration cost variation due to Array Orientation and geographic location in the electric reliability council of texas
Applied Energy, 2016Co-Authors: Thomas A Deetjen, Jared Garrison, Joshua D Rhodes, Michael E WebberAbstract:Abstract Adding large solar photovoltaic (PV) resources into an electric grid influences the flexibility characteristics of its net load profile. The dispatch of the existing generation fleet changes as it adjusts to accommodate the new net load. This study categorizes and defines these flexibility characteristics. It utilizes a unit commitment and dispatch (UC&D) model to simulate large solar generation assets with different geographic locations and Orientations. The simulations show the sensitivity of the wholesale energy price, reserve market prices, total dispatch cost, fuel mix, emissions, and water use to changes in net load flexibility requirements. The results show that generating 22,500 GW h of solar energy in a 2011 simulation of the Electric Reliability Council of Texas (ERCOT) reduces total dispatch cost by approximately $900 million (a 10.3% decrease) while increasing ancillary services costs by approximately $10 million (a 3% increase). The results also show that PV reduces water consumption and water withdrawals as well as CO 2 , NO x , and SO x emissions. It also reduces peak load by 4% but increases net load volatility by 40–79% and ramping by 11–33%. In addition, west-located, west-oriented solar resources reduce total dispatch cost more than the other simulated solar scenarios. The west-located, west-oriented solar simulation required greater system flexibility, but utilized more low-cost generators and fewer high-cost generators for energy production than other simulated scenarios. These results suggest that the mix of energy provided by different generation technologies influences the dispatch cost more than the net load flexibility requirements.
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a multi objective assessment of the effect of solar pv Array Orientation and tilt on energy production and system economics
Solar Energy, 2014Co-Authors: Joshua D Rhodes, Charles R Upshaw, Wesley Cole, Chris L Holcomb, Michael E WebberAbstract:Abstract This analysis considers the effect of the placement (azimuth and tilt) of fixed solar PV systems on their total energy production, peak power production, and economic value given local solar radiation, weather, and electricity market prices and rate structures. This analysis details a model that was used to calculate the output of solar PV systems across a range of azimuths and tilts to find the energetically and economically optimal placement. The result of this method, which concludes that the optimal placement can vary with a multitude of conditions, challenges the default due-south placement that is conventional for typical installations. We found that for Austin, TX the optimal azimuth to maximize energy production is about 187–188°, or 7–8° west of south, while the optimal azimuth to maximize economic output based on the value of the solar energy produced is about 200–231° or 20–51° west of south. The differences between due south (which is the conventional Orientation) and the optimal placement were on the order of 1–7%. Solar PV Arrays that are not constrained on their placement, such as ground mounted Arrays, could possibly increase overall production or the value of that production at no additional installation cost by a slight rotation from the traditional Orientation of due south. The model is then extended to consider 1020 locations across the United States that have Typical Meteorological Year (TMY) data to provide a spatial view of optimal solar placements across the country. For the rest of the US we found that for most locations the energetically optimal solar PV azimuth is within 10° of south. Considering the temporal value of the solar energy produced from spatially-resolved market conditions derived from local time-of-use rates, the optimal placement shifts to a west-of-south azimuth in attempt to align solar energy production with higher afternoon prices and higher grid stress times. There are some locations particularly on the west coast that have west-of-south energy optimal placements, possibly due to typical morning clouds or fog. Further solar considerations, such as maximum peak alignment also have the potential to influence solar placement. These results have the potential to be significant for solar PV installations: utilities might alter rate structures to encourage solar generation that is more coincident with peak demand, utilities might also use west-of-south solar placements as a hedge against future wholesale electricity price volatility, building codes might encourage buildings to match roof azimuths with local optimal solar PV generation placements, and calculations of the true value of solar in optimal and non-optimal placements can be more accurate.
Claude Oestges - One of the best experts on this subject based on the ideXlab platform.
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A new double-directional channel model including antenna patterns, Array Orientation, and depolarization
IEEE Transactions on Vehicular Technology, 2010Co-Authors: Ramya Bhagavatula, Claude Oestges, Robert W. HeathAbstract:Multiple-input-multiple-output (MIMO) wireless channel models are often too simplistic to accurately model wireless propagation effects or too complex and/or site specific to be used for analytical purposes. In this paper, we develop a double-directional MIMO channel model that accounts for important propagation effects like scattering, clustering, and channel depolarization and antenna effects like antenna diversity, cross polarization, and random Array Orientation, while still retaining an intuitive representation. The proposed model can be parameterized using channel measurements obtained from site-specific measurement campaigns or from standard-based channel models. We show, using simulations, that the proposed model captures channel and antenna effects not included in other models, like the third-generation partnership program (3GPP) spatial channel model, the WINNER, and the IEEE 802.11n channel model. We use the model to study the impact of random Orientation and channel depolarization on the data rates of a MIMO system.
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A new MIMO channel representation including spatial diversity, Array Orientation and depolarization effects
2008 IEEE Antennas and Propagation Society International Symposium, 2008Co-Authors: Ramya Bhagavatula, Robert W. Heath, Claude OestgesAbstract:This paper proposes an analytical channel model that accounts for spatial, pattern, polarization diversities, channel depolarization, random mobile terminal Orientations and mutual coupling effects. by utilizing simulations, this study verifies that the model accounts for more propagation effects than the 3GPP SCM and IEEE 802.11n model.
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impact of antenna coupling on 2 times 2 mimo communications
IEEE Transactions on Vehicular Technology, 2007Co-Authors: Bruno Clerckx, Christophe Craeye, Danielle Vanhoenackerjanvier, Claude OestgesAbstract:The impact of mutual coupling induced by two closely spaced minimum scattering antennas at the subscriber unit on 2 times 2 multiple-input multiple-output channels and communications is investigated. Both (de)correlation effects and variations of antenna gain resulting from coupling mechanisms are considered. Relationships between coupling and correlations/channel Frobenius norm are discussed, pointing out the role of the interelement spacing, the Array Orientation, and the richness of scattering. The analysis also yields useful insight into the influence of mutual coupling on capacity and system performance
Andrea Watson - One of the best experts on this subject based on the ideXlab platform.
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potential residential pv development in chile the effect of net metering and net billing schemes for grid connected pv systems
Renewable & Sustainable Energy Reviews, 2015Co-Authors: David Watts, Marcelo F Valdes, Danilo H Jara, Andrea WatsonAbstract:Abstract In recent years the global photovoltaic (PV) market has expanded rapidly due to a sharp decline in PV prices and increased attention to the importance of sustainable energy. Northern Chile has one of the highest irradiance levels in the world as well as one the highest electricity rates in Latin America. Because of these conditions, Chile is one of very few countries where several PV projects are being developed without government subsidies and consequently, the PV industry is experiencing rapid growth. This paper reviews the opportunity to take advantage of these market conditions within the residential sector, modeling PV Arrays across 10 cities in Chile. A detailed modeling of PV systems is performed to achieve an accurate analysis of energy production and electricity cost, using local resource data, optimal Array Orientation and inclination, and production losses. A review of how Net Metering and Net Billing affect the value of the PV production is applied and a comparison using levelized cost of electricity (LCOE) is conducted. Net Metering is found to be a better policy choice to promote PV systems than Net Billing because energy injected into the electrical network is paid at the complete retail rate. However, in developed countries this kind of policy is unlikely to be supported because of it׳s economic unfeasibility. Under a Net Billing scheme a consumer will see an advantage when energy is recorded over longer time intervals and when installing a system with smaller capacity relative to household electricity consumption. This prevents excess generation from being injected into the network which would be bought by the utility at lower prices than the retail rate. Payback periods are found to be low, between 6 years in northern areas with high retail rates and 13 years in other areas with lower radiation and retail rates.