The photovoltaic sail on a building
The sail on La Seine Musicale is covered with more than 800 m² of photovoltaic solar panels, rotating around the glass auditorium. The sail will follow the sun’s path. The aim being to allow the photovoltaic sail to move around an axis following the sun’s azimuth, thereby keeping the sail optimally aimed at the sun. The sail will generate electric power as well as masking the sun shining on the auditorium and acting as a sunshade.
The system comprises a motor drive for the top part of the sail using a slewing ring for aiming it. At the base, there are two central motorised carriages linked together by a traction bar, to ensure the synchronisation of the two half sails. The non-motorised side carriages are used to carry some of the load and add stability to the system.
The system’s main functions comprise:
- Transforming the available energy into mechanical energy to move the sails around the auditorium from the East garage to the South garage and back again at nightfall.
- Optimally positioning the sail in relation to the sun throughout the day.
- Allowing the energy created by the photovoltaic sales to pass to the building.
- Bearing the weight and the stresses applied to the sails by weather conditions and transmitting them to the Civil Engineering part.
Algorithm for meeting with the sun
In addition to conventional mechanical analyses for this kind of project, the algorithm for meeting with the sun was defined. This is because rather than implementing a system for tracking the sun that would potentially not be very accurate on cloudy days, the preferred approach was to calculate the sun’s position over time to send the sail the angular position to reach based on the time and day of the year. Then a PLC was programmed with this algorithm and based on universal time (UT) only, the sail knows the optimum position to reach.
When the centre of the sun exceeds an angle of 95.5° in relation to the geographic North, the sail leaves the East garage and comes into action. Every 15 minutes and until it reaches the South garage when the sun exceeds 190.5°, the sail automatically resets thanks to its algorithm for rendezvousing with the sun. When the sun is below the astronomic sunset, an order is given to return to the East garage to await a new sun cycle.
The general design work was done by RFR (then reused by T/E/S/S for the EXE phase) and went with an articulated system for carrying the sail. Mechanism design was performed by the Meca cluster.
Info obtained from http://cluster-meca.fr/en/seguin.island.musical.complex-61-23.php
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