Information about Nuna

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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.

Currently the Delft University of Technology is working on the Nuna4, for the 2007 World solar challenge.

Nuna 3 (2005)

The team at the race course of Zandvoort

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 very efficient solar cells of a type normally used to power orbital satellites (as had the previous Nunas), and it has better aerodynamics and is lighter 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 advice from Wubbo Ockels, the first Dutch astronaut and professor at the University.

Main specifications

Dimensions	5 x 1.8 x 0.8 m	(l x w x h)
Weight	< 200 kg
Air friction coefficient	0.07	comparison: this value is between 0.25 and 0.35 for modern cars
Solar cell efficiency	> 26%	this is a very high efficiency; for comparison the most efficient solar cells yet created under laboratory conditions were only 6% more efficient than this. The material used to fabricate these cells was a compound containing gallium arsenide. The efficiency of most panels is 15%
Motor efficiency	> 97%	comparison: an average electromotor has an efficiency of 85%
Battery capacity	5 kWh	comparison: an ordinary 24 kg car battery has a capacity of 80 Ah, which equals 1 kWh
Battery weight	30 kg

Design criteria

To have a good chance to win, the car has to:

collect as much solar energy as possible
use as little energy as possible to drive at a certain speed. This means special attention to:
the efficiency of transferring electrical energy to the wheels, and
minimizing friction, constituted by:
air friction (air resistance), and
rolling friction, which in turn is affected by the weight, among other things

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 currently. Apart from efficiency, size also matters, so the entire upper surface 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 2005 race was held in September (as opposed to October or November in previous years) the sun was lower in the sky (it's earlier in spring). To compensate for this, as many cells as possible were placed at the sides, most notably on the wheel caps.

VI characteristic 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 underside of the Nuna 3 model in a wind tunnel

The aerodynamic drag 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

Efficiency of the Biel 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 the original 1993 Motor of the Spirit of Biel III by the Engineering School of Biel, Switzerland (now: Berner Fachhochschule Technik und Informatik). The improvements are due to completely redeveloped digital power electronics and control, realized 1999. They allowed for 50% more power (over 2400 W) and a 45% higher torque compared to the 1993 Spirit of Biel II. The efficiency of the total drive system (including the power electronics losses) is also improved and is now over 98%. But as the graph shows this depends somewhat on the speed and increases with speed. The design was initially made to reach its maximum performance at the normal cruising speed of the solar car at around 100km/h.

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. For comparison, the Sunraycer (the first winner of the Solar Challenge race) attained a top speed of 109 km/h in 1987.

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

5 August 2005: the team arrives in Adelaide.
2 September 2005: The road permit is granted.
16 September 2005: During a test drive Nuna 3 strands in the rough next to the road. A defective wheel suspension turned out to be the cause. The damage was limited and repaired after a few days.
22 September 2005: The Nuna 3 is approved by the organisation.
24 September 2005: The Nuna 3 qualifies for the 8th starting position, which is better than the starting positions the previous two models got.
25 September 2005: The Nuna 3 covered 827 km holding first place, leading the next-placed Michigan team by approximately half an hour.
26 September 2005: On the second day the Nuna 3 covered 835 km, at an average speed of 105 km/h, which is a new single-day record for the World Solar Challenge. The Michigan team is now 132 km behind.
27 September 2005: Nuna 3 covered 858km, beating yesterdays record. They extended their lead to two hours. 500 km to go.
28 September 2005: Nuna 3 arrives as first car in Adelaide, thus scoring a hat-trick. The overall average speed of 103 km/h over 3,010 km means an improvement by 6 km/h of the 2003 record.

External links

Solar energy is energy from the sun. It supports life on Earth and drives the Earth's weather. Solar energy predominantly arrives in the form of infrared, visible and ultraviolet light, and is either returned back to space or is absorbed.
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World Solar Challenge is a solar powered-car race over 3021 km (1,877 miles) through central Australia from Darwin to Adelaide. The race attracts teams from around the world, most of which are fielded by universities or corporations although some are fielded by high schools.
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Anthem
Advance Australia Fair ^[1]

Capital Canberra

Largest city Sydney
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Delft University of Technology, (Technische Universiteit Delft in Dutch) in Delft, the Netherlands, is the largest and most comprehensive technical university in the Netherlands, with over 13,000 students and 2,100 scientists (including 200 professors).
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The Nuna 4 is a solar car developed by the University of Delft in 2006-2007 for the 2007 World Solar Challenge. it succeeds the nuna3 which was the solar card that did a hat trick for the University of Delft by winning the World Solar Challenge for the third time in a row.
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A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell
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satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon.
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For the Daft Punk song, see .

Aerodynamics (shaping of objects that affect the flow of air or gas) is a branch of fluid dynamics concerned with the study of forces generated on a body in a flow.
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Wubbo Ockels

ESA Astronaut
Nationality Dutch
Born May 21, 1945
Almelo, The Netherlands
Other occupation Physicist
Space time 7d 00h 44m
Selection 1978 ESA Group
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Rolling resistance, sometimes called rolling friction or rolling drag, is the resistance that occurs when an object such as a ball or tire rolls. It is caused by the deformation of the wheel or tire or the deformation of the ground.
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Gallium arsenide (GaAs) is a compound of two elements, gallium and arsenic. It is an important semiconductor and is used to make devices such as microwave frequency integrated circuits (ie, MMICs), infrared light-emitting diodes, laser diodes and solar cells.
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trigonometric functions (also called circular functions) are functions of an angle. They are important in the study of triangles and modeling periodic phenomena, among many other applications.
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Electric current is the flow (movement) of electric charge. The SI unit of electric current is the ampere (A), which is equal to a flow of one coulomb of charge per second.

Definition

The amount of electric current (measured in amperes) through some surface, e.g.
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Voltage (sometimes also called electric potential difference or electrical tension) is the potential similarity of electrical potential between two points of an electrical or electronic circuit, expressed in volts.
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Load may refer to:

Structural load, forces which are applied to a structure
Cargo, Freight, or Lading
The load of a mutual fund (see Mutual fund fees and expenses)
The genetic load of a population
The parasite load of an organism

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In physics, power (symbol: P) is the rate at which work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time.
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Direct current (DC or "continuous current") is the constant flow of electric charge. This is typically in a conductor such as a wire, but can also be through semiconductors, insulators, or even through a vacuum as in electron or ion beams.
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transformer is a device that transfers electrical energy from one circuit to another through inductively coupled wires. A changing current in the first circuit (the primary
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alternating current (AC) is an electrical current whose magnitude and direction vary cyclically, as opposed to direct current, whose direction remains constant. The usual waveform of an AC power circuit is a sine wave, as this results in the most efficient transmission of
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In electronic engineering, a DC to DC converter is a circuit which converts a source of direct current (DC) from one voltage level to another. It is a class of power converter.
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Drag may refer to:

Computing

In computing, to drag a mouse's button and hold it down while moving the mouse, used in drag-and-drop

Culture

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turbulence or turbulent flow is a flow regime characterized by chaotic, stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time.
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scale model is a representation or copy of an object that is larger or smaller than the actual size of the object being represented. Very often the scale model is smaller than the original and used as a guide to making the object in full size.
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wind tunnel is a research tool developed to assist with studying the effects of air moving over or around solid objects.

Ways that wind-speed and flow are measured in wind tunnels:

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Emmeloord is the administrative center of the municipality of Noordoostpolder, Flevoland, Netherlands.
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Meteorology (from Greek: μετέωρον, meteoron, "high in the sky"; and λόγος, logos, "knowledge") is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and
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torque (or often called a moment) can informally be thought of as "rotational force" or "angular force" which causes a change in rotational motion. This force is defined by linear force multiplied by a radius.

The SI unit for torque is the newton meter (N m). In U.S.
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