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Air Density

The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform

Anne Bourdon – 1st expert on this subject based on the ideXlab platform

  • Air Density dependent model for analysis of Air heating associated with streamers leaders and transient luminous events
    Journal of Geophysical Research, 2010
    Co-Authors: J A Riousset, Victor P. Pasko, Anne Bourdon

    Abstract:

    [1] Blue and gigantic jets are transient luminous events in the middle atmosphere that form when conventional lightning leaders escape upward from the thundercloud. The conditions in the Earth’s atmosphere (i.e., Air Density, reduced electric field, etc.) leading to conversion of hot leader channels driven by thermal ionization near cloud tops to nonthermal streamer forms observed at higher altitudes are not understood at present. This paper presents a formulation of a streamer‐to‐spark transition model that allows studies of gas dynamics and chemical kinetics involved in heating of Air in streamer channels for a given Air Density N under assumption of constant applied electric field E. The model accounts for the dynamic expansion of the heated Air in the streamer channel and resultant effects of E/N variations on plasma kinetics, the vibrational excitation of nitrogen molecules N2(v), effects of gains in electron energy in collisions with N2(v), and associative ionization processes involving N2(A 3 Su ) and N2(a′ 1 Su ) species. The results are in excellent agreement with available experimental data at ground and near‐ground Air pressures and demonstrate that for the Air densities corresponding to 0–70 km altitudes the kinetic effects lead to a significant acceleration of the heating, with effective heating times scaling closer to 1/N than to 1/N 2 predicted on the basis of similarity laws for Joule heating. This acceleration is attributed to a strong reduction in electron losses due to three‐body attachment and electron‐ion recombination processes with reduction of Air pressure.

Alain Ulazia – 2nd expert on this subject based on the ideXlab platform

  • Global estimations of wind energy potential considering seasonal Air Density changes
    Energy, 2019
    Co-Authors: Alain Ulazia, Gabriel Ibarra-berastegi, Jon Sáenz, Santos J. González-rojí, Sheila Carreno-madinabeitia

    Abstract:

    Abstract The literature typically considers constant annual average Air Density when computing the wind energy potential of a given location. In this work, the recent reanalysis ERA5 is used to obtain global seasonal estimates of wind energy production that include seasonally varying Air Density. Thus, errors due to the use of a constant Air Density are quantified. First, seasonal Air Density changes are studied at the global scale. Then, wind power Density errors due to seasonal Air Density changes are computed. Finally, winter and summer energy production errors due to neglecting the changes in Air Density are computed by implementing the power curve of the National Renewable Energy Laboratorys 5 MW turbine. Results show relevant deviations for three variables (Air Density, wind power Density, and energy production), mainly in the middle-high latitudes (Hudson Bay, Siberia, Patagonia, Australia, etc.). Locations with variations from −6% to 6% are identified from summers to winters in the Northern Hemisphere. Additionally, simulations with the aeroelastic code FAST for the studied turbine show that instantaneous power production can be affected by greater than 20% below the rated wind speed if a day with realistically high or low Air Density values is compared for the same turbulent wind speed.

  • The Consequences of Air Density Variations over Northeastern Scotland for Offshore Wind Energy Potential
    Energies, 2019
    Co-Authors: Alain Ulazia, Gabriel Ibarra-berastegi, Jon Sáenz, Ander Nafarrate, Sheila Carreno-madinabeitia

    Abstract:

    Hywind-Scotland is a wind farm in Scotland that for many reasons is at the leading edge of technology and is located at a paradigmatic study area for offshore wind energy assessment. The objective of this paper is to compute the Capacity Factor ( C F ) changes and instantaneous power generation changes due to seasonal and hourly fluctuations in Air Density. For that reason, the novel ERA5 reanalysis is used as a source of temperature, pressure, and wind speed data. Seasonal results for winter show that C F values increase by 3% due to low temperatures and denser Air, with economical profit consequences of tens of thousands (US$). Hourly results show variations of 7% in Air Density and of 26% in power generation via FAST simulations, emphasizing the need to include Air Density in short-term wind energy studying.

  • Calculation of Lebanon offshore wind energy potential using ERA5 reanalysis: impact of seasonal Air Density changes
    2019 Fourth International Conference on Advances in Computational Tools for Engineering Applications (ACTEA), 2019
    Co-Authors: Gabriel Ibarra-berastegi, Santos J. González-rojí, Alain Ulazia, Sheila Carreno-medinabeitia, Jon Sáenz

    Abstract:

    In this work, data from the ERA5 reanalysis (2010-2017) have been used to estimate the seasonal offshore wind energy potential for the Lebanese coast. Additionally, for this estimation, the effect of seasonal changes of Air Density has been incorporated. As a reference, the SIEMENS 160/6 turbine has been adopted and wind energy potential has been expressed as the capacity factor (CF) associated to this turbine. The spatial distribution of CF provides an idea of available wind energy potential in the Lebanese coast. The impact of seasonal Air Density changes has been assessed as percentage reduction in this indicator. In summer, the CF reduction due to high temperatures and lower Air Density, reaches in some Southern regions of the Lebanese coast to values around 5.5%. The use of such reanalyses is likely to increase in the future, thus making consultancy work easier since a lot of computational work with state-of-the-art meteorological models like WRF or MC2 (used to draw the National Wind Atlas of Lebanon) may not be necessary. Therefore, most likely in the future, for wind potential estimations, rather than heavy calculation efforts, the know-how for consultancy companies will focus into deeper analysis and interpretation of readily-available data from reanalyses.

Victor P. Pasko – 3rd expert on this subject based on the ideXlab platform

  • Dynamics of sprite streamers in varying Air Density
    Geophysical Research Letters, 2015
    Co-Authors: Victor P. Pasko

    Abstract:

    Similarity laws for streamer discharges, which state that the properties of streamers such as streamer radius, electric field, and electron Density should respectively scale as N−1, N1, and N2 in different but uniform Air densities N, are important relations that have provided a general understanding of the mesospheric sprite discharges based on existing knowledge of streamers in laboratory conditions. Recent modeling studies, however, show that the properties of sprite streamers in varying Air Density do not follow exactly or even contradict the similarity relations. We present here simulation results and related analysis of sprite streamers to provide a unified view and resolve these contradictions. Our results indicate that the properties of streamers in varying Air Density are determined by the physical dimensions of streamers and the reduced electric field E/N, with the varying Air Density N being only one of the three factors controlling the streamer properties.

  • Air Density dependent model for analysis of Air heating associated with streamers leaders and transient luminous events
    Journal of Geophysical Research, 2010
    Co-Authors: J A Riousset, Victor P. Pasko, Anne Bourdon

    Abstract:

    [1] Blue and gigantic jets are transient luminous events in the middle atmosphere that form when conventional lightning leaders escape upward from the thundercloud. The conditions in the Earth’s atmosphere (i.e., Air Density, reduced electric field, etc.) leading to conversion of hot leader channels driven by thermal ionization near cloud tops to nonthermal streamer forms observed at higher altitudes are not understood at present. This paper presents a formulation of a streamer‐to‐spark transition model that allows studies of gas dynamics and chemical kinetics involved in heating of Air in streamer channels for a given Air Density N under assumption of constant applied electric field E. The model accounts for the dynamic expansion of the heated Air in the streamer channel and resultant effects of E/N variations on plasma kinetics, the vibrational excitation of nitrogen molecules N2(v), effects of gains in electron energy in collisions with N2(v), and associative ionization processes involving N2(A 3 Su ) and N2(a′ 1 Su ) species. The results are in excellent agreement with available experimental data at ground and near‐ground Air pressures and demonstrate that for the Air densities corresponding to 0–70 km altitudes the kinetic effects lead to a significant acceleration of the heating, with effective heating times scaling closer to 1/N than to 1/N 2 predicted on the basis of similarity laws for Joule heating. This acceleration is attributed to a strong reduction in electron losses due to three‐body attachment and electron‐ion recombination processes with reduction of Air pressure.