7,833 research outputs found
JUMPSAT: Qualifying three equipments in one Cubesat mission
We work on a student 3U Cubesat mission, called JUMPSAT, expected for 2017. This is a collaborative project involving both institutions (CNES, ONERA) and schools (ISAE, TELECOM Bretagne). The different equipments to qualify are the Supaero Star Tracker, which measures stars’ luminosity to infer the satellite’s attitude, a detector for particles trapped in the Earth magnetic field designed by the ONERA, and the AOCS. Uplink and Downlink communications will be provided during the mission by the HETE Primary Ground Stations. JUMPSAT is the first Cubesat which needs a three axis attitude control, which involves an innovative mission analysis, to overcome all these constraints. The mission analysis deals with the orbit’s determination, the Cubesat’s structure, the power strategy, and the visibility balance. The particles detector is the only constraint for the altitude of the satellite: we can get meaningful data only at altitudes higher than 700 km. Moreover, the most interesting zones are South Atlantic and poles. But a circular orbit with this altitude does not respect the LOS (French space act).The structure of the Cubesat is also hard to define. To get information from the satellite, we need an antenna, and an attitude and orbital control system to point the antenna at the ground station and the Star Tracker at the stars. Solar Panels cannot be opened out because of the micro elements that could be settled on the particles detector. However, fixed solar panels are not very efficient to recharge batteries. The power balance shows critical problems: both attitude control system and the Star Tracker consume a lot, and cannot work at the same time during the whole orbit. However, all the components are linked: the Star Tracker is not efficient if the satellite attitude is not stabilized; the antenna functioning must be synchronized with visibilities by the ground station. Anyway, the visibility balance stresses the point that a ground station at Toulouse would be particularly welcome. We need also to take into account phenomena of eclipse and satellite drift. To conclude, our mission analysis is deeply constrained by the equipments we want to qualify. Our task is to find the optimal orbit, suggest a power strategy considering the orbital constraints and components’ physical parameters, and to study the visibility balance. It is a real challenge in terms of power consumption, architecture, orbital strategy for such a small satellite
Hydrogen at the rooftop: Compact CPV-hydrogen system to convert sunlight to hydrogen
Despite being highest potential energy source, solar intermittency and low power density make it difficult for solar energy to compete with the conventional power plants. Highly efficient concentrated photovoltaic (CPV) system provides best technology to be paired with the electrolytic hydrogen production, as a sustainable energy source with long term energy storage. However, the conventional gigantic design of CPV system limits its market and application to the open desert fields without any rooftop installation scope, unlike conventional PV. This makes CPV less popular among solar energy customers. This paper discusses the development of compact CPV-Hydrogen system for the rooftop application in the urban region. The in-house built compact CPV system works with hybrid solar tracking of 0.1° accuracy, ensured through proposed double lens collimator based solar tracking sensor. With PEM based electrolyser, the compact CPV-hydrogen system showed 28% CPV efficiency and 18% sunlight to hydrogen (STH) efficiency, for rooftop operation in tropical region of Singapore. For plant designers, the solar to hydrogen production rating of 217 kWhe/kgH2 has been presented with 15% STH daily average efficiency, recorded from the long term field operation of the syste
Analysis of the advanced Nimbus power systems
Solar-conversion power-supply subsystem for Nimbus B, using pulse width modulated voltage regulato
A Sliding Mode Control for a Sensorless Tracker: Application on a Photovoltaic System
The photovoltaic sun tracker allows us to increase the energy production. The
sun tracker considered in this study has two degrees of freedom (2-DOF) and
especially specified by the lack of sensors. In this way, the tracker will have
as a set point the sun position at every second during the day for a period of
five years. After sunset, the tracker goes back to the initial position (which
of sunrise). The sliding mode control (SMC) will be applied to ensure at best
the tracking mechanism and, in another hand, the sliding mode observer will
replace the velocity sensor which suffers from a lot of measurement
disturbances. Experimental measurements show that this autonomic dual axis Sun
Tracker increases the power production by over 40%
A Sliding Mode Multimodel Control for a Sensorless Photovoltaic System
In this work we will talk about a new control test using the sliding mode
control with a nonlinear sliding mode observer, which are very solicited in
tracking problems, for a sensorless photovoltaic panel. In this case, the panel
system will has as a set point the sun position at every second during the day
for a period of five years; then the tracker, using sliding mode multimodel
controller and a sliding mode observer, will track these positions to make the
sunrays orthogonal to the photovoltaic cell that produces more energy. After
sunset, the tracker goes back to the initial position (which of sunrise).
Experimental measurements show that this autonomic dual axis Sun Tracker
increases the power production by over 40%
Observations of the December 13 and 14, 2006, Solar Particle Events in the 80 MeV/n - 3 GeV/n range from space with PAMELA detector
We present the space spectrometer PAMELA observations of proton and helium
fluxes during the December 13 and 14, 2006 solar particle events. This is the
first direct measurement of the solar energetic particles in space with a
single instrument in the energy range from 80 MeV/n up to 3
GeV/n. In the event of December 13 measured energy spectra of solar protons and
helium were compared with results obtained by neutron monitors and other
detectors. Our measurements show a spectral behaviour different from those
derived from the neutron monitor network. No satisfactory analytical fitting
was found for the energy spectra. During the first hours of the December 13
event solar energetic particles spectra were close to the exponential form
demonstrating rather significant temporal evolution. Solar He with energy up to
~1 GeV/n was recorded on December 13. In the event of December 14 energy of
solar protons reached ~600 MeV whereas maximum energy of He was below 100
MeV/n. The spectra were slightly bended in the lower energy range and preserved
their form during the second event. Difference in the particle flux appearance
and temporal evolution in these two events may argue for a special conditions
leading to acceleration of solar particles up to relativistic energies.Comment: Accepted for publication on Astrophysical journa
Financial Analysis of a Grid-connected Photovoltaic System in South Florida
In this paper the performance and financial analysis of a grid-connected
photovoltaic system installed at Florida Atlantic University (FAU) is
evaluated. The power plant has the capacity of 14.8 kW and has been under
operation since August 2014. This solar PV system is composed of two 7.4 kW
sub-arrays, one fixed and one with single axis tracking. First, an overview of
the system followed by local weather characteristics in Boca Raton, Florida is
presented. In addition, monthly averaged daily solar radiation in Boca Raton as
well as system AC are calculated utilizing the PVwatts simulation calculator.
Inputs such as module and inverter specifications are applied to the System
Advisor Model (SAM) to design and optimize the system. Finally, the estimated
local load demand as well as simulation results are extracted and analyzed.Comment: 6 Pages, IEEE PVSC 2017 Conference, Washington D.
CUSTARD (Cranfield University Space Technology Advanced Research Demonstrator) - A Micro-System Technology Demonstrator Nanosatellite. Summary of the Group Design Project MSc in Astronautics and Space Engineering. 1999-2000, Cranfield University
CUSTARD (Cranfield University Space Technology And Research Demonstrator) was
the group design project for students of the MSc in Astronautics and Space
Engineering for the Academic Year 1999/2000 at Cranfield University. The project
involved the initial design of a nanosatellite to be used as a technology
demonstrator for microsystem technology (MST) in space. The students worked
together as one group (organised into several subgroups, e.g. system,
mechanical), with each student responsible for a set of work packages. The
nanosatellite designed had a mass of 4 kg, lifetime of 3 months in low Earth
orbit, coarse 3-axis attitude control (no orbit control), and was capable of
carrying up to 1 kg of payload. The electrical power available was 18 W (peak).
Assuming a single X-band ground station at RAL (UK), a data rate of up to 1 M
bit s-1 for about 3000 s per day is possible. The payloads proposed are a
microgravity laboratory and a formation flying experiment.
The report summarises the results of the project and includes executive
summaries from all team members. Further information and summaries of the full
reports are available from the College of Aeronautics, Cranfield University
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