Information AboutNuna |
| CATEGORIES ABOUT NUNA | |
| solar vehicles | |
| delft university of technology | |
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Nuna is the name of a series of manned Solar Powered vehicles that won the World Solar Challenge in Australia three times in a row, in 2001 (Nuna 1 or just Nuna), 2003 (Nuna 2) and 2005 (Nuna 3). The Nunas are built by students of the Delft University Of Technology . NUNA 3 (2005) ]] Nuna 3 was one of the favourites for the 2005 edition of the World Solar Challenge with a pre-race test-drive speed of 130 km/h. The final result was that the 3021 kilometers between Darwin and Adelaide were covered in a record 29 hours and 11 minutes, averaging about 103 km/h. It has improved Solar Cell s of a type that is otherwise only used in Artificial Satellites (as had the previous Nunas), and it has better Aerodynamics and a lower weight than its predecessors. It was designed and built by 11 students from different disciplines of the Delft University of Technology, who have partly put their studies on hold for this. They used the hightech labs and workshops of the University and, as with the Nuna 2, they received advise from Wubbo Ockels , the first Dutch astronaut and professor at the University. Main specifications Design criteria To have a good chance to win, the car has to:
Solar cells The solar cells are made of Gallium Arsenide (GaAs) and consist of three layers. Sunlight that penetrates the upper layer is used in the lower layers, resulting in an efficiency of over 26%. This type of solar cell is among the best available at the moment. Apart from efficiency, size also matters, so the entire roof of the Nuna 3 is covered with them, except for the cockpit. Efficiency is optimal when the cells are hit by the solar rays perpendicularly. If not, output is reduced by roughly the Cosine of the angle with the perpendicular. Because the race is held in September this year (as opposed to October or November in previous years) the sun will be lower in the sky (it's earlier in spring). To compensate for this, as many cells as possible are placed at the sides, most notably on the wheel caps. of a solar cell]] A solar cell gives a certain amount of Current for a certain amount of sunlight. The Voltage depends on the Load (more precisely the resistance of the load). The Power is the product of voltage and current and therefore also depends on the load. Over a certain voltage the current of the solar cell quickly drops to zero, as the graph illustrates. However, the batteries have a fairly constant voltage, which also has a rather different value than that of the solar cells. So a voltage transformation is needed. Because this is Direct Current , a normal Transformer , which uses Alternating Current can not be used. Also, the DC-DC Converter has to make sure the load the solar cells see is such that the solar cells give maximum power, so also at the top of the green line in the graph. The machine that does this is called the Maximum Power Point Tracker (MPPT). Here too, the goal is to have this conversion achieve maximum efficiency (>97%). Aerodynamic design ]] The Aerodynamic Resistance is an important part of the total resistance. Important are the frontal surface and the streamline. Any deviation from the ideal streamline will cause Turbulence , which costs energy. The ideal streamline is achieved in various stages: #Through computer simulations of the design #Through testing of a Scale Model in a Wind Tunnel . For example, liquid paints can be applied to see the flow of air over the surface. The photo shows is taken during one of those tests in the Low Speed Laboratory of the TU Delft. #Through testing of the full scale car in a wind tunnel. For this a German-Dutch wind tunnel in Emmeloord will be used. From Meteorological data from the area where the contest is to take place, it can be concluded that there will likely be a strong side-wind. The wheel caps of the Nuna 3 are designed such that a sidewind will have a propulsory effect. Motor engine]] The motor is totally encased in the rear wheel to minimise loss through mechanical transmission from motor to wheel(such as in a normal car in the gear box and cardan). The motor is an improved version of a Swiss motor by . The efficiency of the motor is also improved and is now over 98%. But as the graph shows this depends somewhat on the speed and increases with speed. Test drive During one of the test drives in the Netherlands the Nuna 3 achieved a speed of 130 km/h. On the first day of the race the car achieved a top speed of 140 km/h. The race Winning the race requires not just a good vehicle but also a clever way of driving it, in accordance with the characteristics of the track. Which is why this has been researched for two months prior to the race. Height differences are mapped and linked to GPS data. From this, during the race, the optimal speed can be determined. Despite all testing and other preparations, one uncertain factor remains; the Weather . Any clouds would strongly influence the amount of sunlight that can be captured. So any weather changes along the track will have to be constantly monitored. All these data are analysed by a computer model that constantly computes the ideal speed for that moment. This equipment is built into (petrol powered) pilot cars. Through Telemetry these constantly receive data about the condition of the batteries and the amount of captured sunlight. Important opponents The winner of the American Solar Challenge from the University Of Michigan (USA) was considered to be one of the most important opponents. Other important contestants were the MIT (also USA) and the Japanese Ashiya University team. In 2005 there were also two other European contestants, the Dutch Raedthuys Solar Team from the University Of Twente and the Belgian Umicore Solar Team from Leuven . 2005 Race monitor
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