Design Criteria and Vehicle Specifications
Solar Vehicle Design Criteria
 Design and build an environmentally friendly solar
powered model vehicle which illustrates the idea of a car
of the future, capable of harnessing solar energy, storing
it and releasing it under controlled conditions. The vehicle
must include recycled or recyclable components or
materials within its design. In competition, the race
winning vehicle will be judged to be the one that
accumulates the most points over the three attempts.
Design and Technology National Curriculum coverage includes:
- Knowledge and understanding of systems and control: statements 5 (a) (b) (c) (d) (e)
Summary: Recognise the elements of systems that can be broken down and the importance of feedback;
understand basic principles of electrical, electronic control systems including sensors; understand basic mechanical
systems and how these can be linked to other control systems.
- Evaluating process and products: statements 3 (a) (b) (c)
Summary: Evaluation of ideas and comparison with original intention; testing and evaluation of prototypes;
use of criteria for judging wider fitness for purpose.
Solar Vehicle Specifications
- Your vehicle must include recycled or recyclable items within its design and the team must be able
to demonstrate features which make the vehicle environmentally friendly.
- All electrical components must have been supplied by Rapid (www.rapidonline.com).
- The power used to drive your vehicle must be harnessed by one or more standard Rapid solar panels
(Rapid 42-0240). This energy should be stored before use in one Rapid 10 farad super capacitor only.
- In the unlikely event that lighting conditions affect the performance of the solar panel, DC power sources
will be available to provide charge to the main 10F capacitor. The design should facilitate disconnection
of the solar panel(s) and access to the capacitor leads. However, any team required to charge their vehicle using
a DC power source will be penalised.
- Each vehicle must have an on / off switch, accessible from the outside, which enables the power to the motor(s)
to be cut.
- Maximum length (from the furthest point at the rear to the furthest point at the front) must not exceed
300mm.
- Maximum width (from the widest point at left to the widest point at right) must not exceed 190mm.
- Maximum height (from ground to highest point) must not exceed 150mm.
(Please note the track walls are 50mm in height)
- Teams may like to use a body shell to improve aerodynamics and aesthetics. This may not exceed the
maximum dimensions outlined above.
- All vehicles must have at least three wheels which touch the ground at all times.
 Solar Vehicle
Resources Needed:
- Solar panel
- 10F capacitor
- Motor(s)
- Drive units
- Chassis
The solar panels convert light into electrical energy
but as yet they are not very efficient. However in
the last 5 years solar panels have increased from
3% to 15% in their efficiency. A typical solar panel
might offer an efficiency of 15% - i.e. just 15% of
the energy falling as light on the surface…
However, an alternative approach to solar power involves separating the solar panel array from the vehicle. A large
array of fixed solar panels can be used to charge a storage battery which is then transferred to the vehicle. In future
practical schemes, the batteries might be exchanged in garages for a price reflecting all the costs of harnessing the
energy in the first place. Many car manufacturers, including Toyota, are working on ever more efficient storage batteries
and highly efficient electric motors (and control systems) that waste very little energy as heat when they run.
On a much smaller scale, powering even very small electric motors directly can be a problem because of the relatively
large area of solar panels needed. However, a new storage medium – the super capacitor – now offers an extremely
effective solution. Developed as computer back-up capacitors, these devices offer some of the characteristics of a
rechargeable battery and the rapid charge benefits of a capacitor. They can store large amounts of energy, and provide
high (and sustained) currents during discharge. Not surprisingly, these super capacitors were quickly taken up by toy
manufacturers as light-weight battery substitutes for small models such as electric cars and helicopters.
Super capacitors are available in a range of values from 1 farad to 150 farads – an enormous capacity when one
considers that a few years ago even a 1 farad capacitor would have filled a small room! The Toyota Technology Challenge
involves the use of a 10 farad capacitor combined with a solar panel providing a maximum output of 100mA at 3 volts.
This type of panel is commonly available and used for conventional solar powered battery chargers.
Breaking down the task
The first part of the task requires familiarity with the resources – notably how the solar panel and capacitor
work in combination. This calls for both demonstrations and pupil experiments. A very simple demonstration
shows that a typical small motor will not run directly from the solar cell if the latter is held close to a 60 watt
light source. Under the same conditions, however, a super capacitor can be charged in a short period to give
the motor a useful running time!
This demonstration raises a number of questions and might lead to experiments for quantifying and comparing
light levels, capacitor charging times and motor running times. An inexpensive photographic light meter would
be invaluable here but a light dependent resistor connected to a multimeter provides an uncalibrated substitute.
Once the pupils are more familiar with the choice of available resources and how they work, it is time for design
decision making. For example:
- Is the capacitor carried permanently on the vehicle or is it charged off-vehicle and plugged in?
- What motors provide optimum performance?
- What transmission system is most efficient (e.g. gears or pulley drive)?
- What kinds of wheels give the least rolling resistance?
The (optional) chassis kit could be used as a quick-fix method of assembling the basic parts for trialling.
The parts can be joined by mechanical locking (and gluing if needed) or fastenings such as 4mm screws and
nuts.
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