A team of seven students from the Terrassa School of Industrial and Aeronautical Engineering (ETSEIAT) of the Universitat Politècnica de Catalunya. BarcelonaTech (UPC) have developed the technology for flying the Solar Endeavour UPC, Spain’s first photovoltaic-powered plane built by students.
The project’s main goal was to incorporate solar cells in the wings and to design an energy management system (EMS). This technology, which has been successfully developed in other countries but is not available in Catalonia or Spain, is essential for solar planes. The Solar Endeavour UPC project is sponsored by companies including GTD and CATUAV and through the INSPIRE programme for promoting entrepreneurial talent at the ETSEIAT.
After 18 months of extra-curricular work on their own initiative, the students have built a solar plane that they kept in the air for nearly six hours straight at the Sedis aero club in Seu d’Urgell thanks to the sun’s energy. Collaboration with industry has been vital to the success of this venture. GTD Sistemas de Información, one of the project’s main sponsors, designated an engineer to provide technical support.
Solar Endeavour managed to fly for 5h48min thanks to its intelligent EMS. The motor is fed from two power sources: the batteries and the solar panel. During peak sunlight hours (10:00–18:00), the solar panel can provide more than half the power required for the plane to maintain stable flight, thus extending the battery life. Even though the sun is a not constant energy source, this system means that the plane can always fly with the batteries, which are charged when there is good sunlight.
Efficiently and correctly managing all flight situations, including climbing and descending, atmospheric changes, downbursts, strong winds, and drops in solar intensity, is highly complex. An intelligent EMS is needed, as it provides the power and manoeuvrability required to control the plane at all times from the ground control station.
One of the project’s biggest challenges was to guarantee the Solar Endeavour’s flight autonomy. The team developed an EMS suited to the plane’s design that would distribute power from the solar cells and batteries to the motor and established an energy management strategy to maximise its autonomy.
The type of EMS used in solar planes is not available on the market as it has strict, tightly defined specifications. This meant developing an EMS exclusively for the project that had an auto-control algorithm for maximising the aircraft’s autonomy. The electronic circuit was designed and implemented with components of the highest quality and efficiency in adherence to the strictest operational requirements.
The EMS is one of the project’s cornerstones. In addition to its use in this prototype, it has also provided an architecture design that is scalable to any type of solar plane.
One of the main obstacles facing the students was adapting the solar cells to the wings. This was a highly complex technical challenge because of the extreme fragility of monocrystalline silicon, which is used to make the cells. Interference between the solar cells and the wing’s aerodynamic profile must be kept to minimum, which is why this technology is critical for the success of solar planes: a plane may lose control if excessive thickness or a rough finish causes a loss of airflow over the wing.
On a solar plane, cells are fitted to the wings and sometimes to the tail to take advantage of the entire available surface and collect the maximum amount of energy possible. This means that the solar cells have to be adapted and fitted to the curved, aerodynamic surface of the wing. Solar cells are 0.2 mm thick and not very flexible, making them very difficult to adapt without breaking. The panel built by the students was a success as they achieved a total thickness of less than 1 mm for the cells and their protective coating, allowing the plane to fly correctly.
Solar Endeavour has a telemetry and remote control system provided by CATUAV. The system, which has a maximum range of 15 km, includes an on-board video camera, flight-assistance instrumentation and GPS navigation. It ensures the plane’s safety and also provides real-time data to the ground control station for in-flight decision making.
Solar planes are the perfect platform for increasing the capabilities of unmanned aircraft. As the use of unmanned aerial vehicles (UAV) has exploded in recent years, it has become clear that the capabilities of these aircraft are constrained by their limited autonomy in low-cost civil applications. UAVs equipped for solar flight could fly non-stop over a particular area for days and be used for forest-fire prevention, traffic control and communications in isolated areas and scientific missions. The Solar Endeavour project aims to demonstrate the potential that these technologies hold for civilian applications.
The students in the ETSEIAT’s Trencalòs team working on Solar Endeavour UPC are Joaquim Creus Prats, Carles Felip Aragón, Josep Fernández Coll, Marta Marimon Mateu, Ignacio Pedrosa Lojo, Arnau Pons Lorente and Xavier Serena Alòs. This project is sponsored by the ETSEIAT–UPC’s INSPIRE programme for promoting talented entrepreneurs.
To make this dream a reality, the team has had the support of at least six companies. GTD Sistemas de Información S.A., the main driving force and sponsor behind the project, designated an engineer to act as a tutor and liaison between the company and the university. Laser manufacturer ROFIN IBERIA provided the solar-cell cutting service with a high-power laser. The high-performance photovoltaic cells were supplied by Heliene S.L. The Manresa Technology Centre (CTM) sponsored the solar-energy-management aspect of the project. Airtech Vacuum Solutions supplied composite consumables. CATUAV provided a telemetry and remote control system that makes it possible to pilot a plane of this type as if it were manned. Club Sedis in Seu d’Urgell and the International Centre for Numerical Methods in Engineering also provided their support to the project.
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