Nuna
Encyclopedia
World Solar Challenge
The World Solar Challenge is a solar-powered car race which covers through the Australian Outback, 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...
in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
four times in a row, in 2001 (Nuna 1
Nuna 1
Nuna 1 was a car powered by solar-power, developed by students from the Delft University of Technology.The first Nuna Team was founded in 2000 by Ramon Martinez and Tim de Lange. The project was sponsored by Nuon. Thanks to this financial help the team was able to finish their first car: Nuna 1...
or just Nuna), 2003 (Nuna 2), 2005 (Nuna 3) and 2007 (Nuna 4). The Nunas are built by students who are part of the Nuon
Nuon (company)
Nuon is a Dutch utility company. It belongs to the group of Vattenfall.Nuon produces, sells and delivers electricity, gas, heat and additional services. The company is active in the Netherlands, Belgium and Germany and has more than 2.7 million customers. With over 10,000 employees in 2005 it...
Solar Team at the Delft University of Technology
Delft University of Technology
Delft University of Technology , also known as TU Delft, is the largest and oldest Dutch public technical university, located in Delft, Netherlands...
in the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
.
"Nuna" is also the Icelandic word "now
Present
Present is a time that is neither past nor future.Present may also refer to:- Time and timing :* Present tense, the grammatical tense of a verb* Before Present, radiocarbon dates relative to AD 1950* Presenting, a medical term* Presenteeism...
."
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.
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
depends on the load (more precisely the resistance of the load). The power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...
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. A special type of DC-DC converter is used to ensure the load resistance presented to the solar cells is such that the solar cells give maximum power, so also at the top of the green line in the graph. This is called a Maximum power point tracker
Maximum power point tracker
Maximum power point tracking is a technique that grid tie inverters, solar battery chargers and similar devices use to get the maximum possible power from the PV array. Solar cells have a complex relationship between solar irradiation, temperature and total resistance that produces a non-linear...
(MPPT). Here too, the goal is to have this conversion achieve maximum efficiency (>97%).
Aerodynamic design
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
is an important part of the total resistance. Important are the frontal surface area and the coefficient of drag. The shape must be designed to preserve laminar flow
Laminar flow
Laminar flow, sometimes known as streamline flow, occurs when a fluid flows in parallel layers, with no disruption between the layers. At low velocities the fluid tends to flow without lateral mixing, and adjacent layers slide past one another like playing cards. There are no cross currents...
, as turbulence
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...
causes increased surface drag. The ideal shape is achieved in various stages:
- Through computer simulations of the design.
- Through testing of a scale modelScale modelA scale model is a physical model, a representation or copy of an object that is larger or smaller than the actual size of the object, which seeks to maintain the relative proportions of the physical size of the original object. Very often the scale model is used as a guide to making the object in...
in a wind tunnelWind tunnelA wind tunnel is a research tool used in aerodynamic research to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...
. For example, liquid paints can be applied to see the flow of air over the surface. The photo shown was 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 EmmeloordEmmeloordEmmeloord is the administrative center of the municipality of Noordoostpolder, Flevoland, Netherlands.At the heart of the Noordoostpolder, where the three main drainage canals intersect, is the city of Emmeloord . Emmeloord is in a polder: land reclaimed from the IJsselmeer, which earlier was part...
is used.
From meteorological
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
data at 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
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
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 100 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
Weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
. 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
Telemetry
Telemetry is a technology that allows measurements to be made at a distance, usually via radio wave transmission and reception of the information. The word is derived from Greek roots: tele = remote, and metron = measure...
these constantly receive data about the condition of the batteries and the amount of captured sunlight.
Team
Each version of the Nuna has been built by a team consisting of students of the Delft University of Technology. The team has between ten and twenty team members. They take a year off from their studies to design and build a new version of the solar racer from scratch.In 2001 the Nuna 1 was built by the alpha-centauri team. They were provided with guidance from former astronaut Wubbo Ockels
Wubbo Ockels
Prof. Dr. Wubbo Johannes Ockels is a Dutch physicist and a former ESA astronaut. In 1985 he participated in a flight on a space shuttle , making him the first Dutch citizen in space. He was not the first Dutch-born astronaut, as he is preceded by the naturalized American Lodewijk van den Berg, who...
.
Since 2002 the team has been called the Nuon Solar Team and have had Ockels providing advice and assistance.
Nuna 3 (2005)
Nuna 4 (2007)
The main changes to the Nuna 4 from its predecessor the Nuna 3 are a steering wheel instead of levers, an upright seat instead of the driver lying down and a smaller solar panel of 6 m² compared to the previous 9 m². These changes were necessitated by changes in the rules prompted by alleged safety concerns and attempts to make the car more like a real car, and by reductions in the speed limit on Australian roads. The Nuna 4 won in 2007.Nuna 5 (2009)
The main changes to the Nuna 5 from its predecessor the Nuna 4 was the diminished battery weight, changing from 30 kg in 2007 to 25 kg.Other changes required cars not be allowed to race on previously used slicks (smooth tires), instead requiring profiled (treaded or grooved) tires. Also, the driver was required to sit more upright with a seating angle of, at most, 27 degrees.It finished second.
Nuna 6 (2011)
The main changes to the Nuna 6 from its predecessor the Nuna 5 is the change of solar cells to Monocrystalline siliconMonocrystalline silicon
Monocrystalline silicon or single-crystal Si, or mono-Si is the base material of the electronic industry. It consists of silicon in which the crystal lattice of the entire solid is continuous, unbroken to its edges. It can be prepared intrinsic, i.e...
cells in accordance with the new rules for the World solar challenge.
Also the weight of the batteries has been reduced in accordance with the rules.
To improve performance the weight of the car and aerodynamic drag have been reduced
See also
- The Twente OneTwente OneThe Twente One is the second solar car developed by the University of Twente and Saxion University in 2007, and succeeds the SolUTra...
a competing Dutch solar car from the University of Twente. - The SolUTraSolUTraThe Solutra is the first solar car designed by a group of students, the Raedthuys Solar Team, of the University of Twente. It participated in the 8th World Solar Challenge in 2005 and finished 9th place. Another Dutch team won the race with their car Nuna 3....
TUs car which preceded the Twente One. - The Nuna 5Nuna 5The Nuna 5 is the newest in the Nuna series solar-powered racing car built by the Dutch Nuon Solar Team.In October 2009, Nuna 5 ran second, in a field of twenty-five, in the World Solar Challenge in Australia....
solar car of the Nuon Solar Team which came in second in 2009. - List of solar car teams
- World Solar ChallengeWorld Solar ChallengeThe World Solar Challenge is a solar-powered car race which covers through the Australian Outback, 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...