Download EV Fest Experiments

Task 1: Where does your electricity come from?
Electric vehicles such as electric trains can be permanently connected to the electricity grid
via overhead wires, while other electric vehicles such as cars and busses may use
rechargeable batteries or capacitors as a temporary store of electrical energy from the grid so
that they don’t have to be connected by wires. Either way, the electrical energy sourced from
the grid has been transformed from some other source and converted into electrical energy for
distribution and use. In this task students determine where the electrical energy would come
from if their family owned an electric vehicle such as an electric bicycle, motorcycle or car
and recharged it at home.
Resources:
1. Home electricity bill
2. Information on any home generation such as wind or solar PV
3. The internet
(http://www.energy.nsw.gov.au/electricity/generation, http://www.aemo.com.au/Electricity/P
lanning/Related-Information/~/media/Videos/InteractiveMap_2012.swf.ashx)
Students work through the following questions using the above resources (expected time 80120 minutes):
1. How much electrical energy does your household use?
2. How much of this is during peak time’s v’s shoulder and off peak times?
3. If you charged a 0.3 kWh battery for your electric bicycle overnight 5 days per week, how
much would it add to your electricity bill in terms of energy consumption and additional
cost?
4. Does your household have a grid connected solar system and/or have specifically
purchased green energy? What proportion of your household energy consumption is
renewable?
5. Using the http://www.energy.nsw.gov.au/electricity/generation website - create a pie chart
of the total generating capacity of the different types of power generation currently existing in
NSW
6. Using the http://www.energy.nsw.gov.au/electricity/generation website - create a pie chart
to the total generating capacity of the different types of power generation that have been
approved or are in the planning system for NSW
7. Compare your pie charts of existing power generation capacity with the power generation
capacity that is in the planning pipeline. How is the mix of power generation capacity
changing? What will this mean for greenhouse gas emissions for the electricity sector in the
future?
8. Using the http://www.aemo.com.au/Electricity/Planning/RelatedInformation/~/media/Videos/InteractiveMap_2012.swf.ashx interactive map - Click the
‘Regional Zone Based Maps’ button, Click ‘Transmission System/Power Stations’, ‘Net
Energy Produced’, ‘Directional Energy Transfers’ and ‘Net Energy Transfers’. How much
energy is transferred to NSW from other states?
9. Click ‘Reset Maps, Layers and Data’ – Now Click ‘Solar Exposure Based Maps’ and
‘Transmission System/Power Stations’. If you were asked to build a major Solar Power
Station, where would you build it in NSW so that it had good access to both Sunshine and a
major Electricity Grid Connection?
10. Repeat 9 – but for a Wind Farm using the ‘Wind Speed Based Maps’
Task 2: Designing a Standalone Electrical Power Source
The EV Prize competition includes a prize category called ‘Power Source EVolution’ which
challenges teams to design and prototype a portable, on demand, zero emissions
power generator. Completion of the total task is expected to take approximately 20 hours, but
the research and design component of the activity may be completed as a standalone activity
and be completed in a shorter time period(<5 hours).
Rules and instructions for the ‘Power Source EVolution Prize’ can be found at
http://www.hunterevfestival.net
8.3.2 One of the main advantages of electricity is that it can be moved with comparative
ease from one place to another
Task 1: Determination of the force between the plates of a capacitor
Capacitors store electrical energy as an accumulation of charge between two conductors that
are separated by an insulating layer. Because capacitors store electrical energy by simply
moving charges rather than chemical reactions, they can be made of very inert materials that
can survive many millions of charge and discharge cycles. Small capacitors are used in
electrical devices to filter and condition electrical signals, but very large capacitors are being
increasingly used for energy storage in electric vehicles. In the EV Prize competition teams
have used ultra-capacitors to regulate power spikes created by brushed motors which can trip
the power protection circuits of battery management systems when they are operated at close
to their limit and to maximise the effect of regenerative braking.
How well a capacitor stores charge is referred to as its capacitance and is given by the
equation:
C=q/V
Where C is the capacitance in Farads, q is the electrical charge stored in the capacitor in
Coulombs and V is the voltage the capacitor has been charged to.
In a capacitor the strength of the Electric Field ‘E’ is dependent on the thickness of the
insulating layer and is given by the equation:
E=V/d
Where E is the electric field strength, V is the voltage across the capacitor terminals and d is
the thickness of the insulating layer in meters.
The force ‘F’ between two charged objects is given by the equation:
F=Eq
Where F is the force in Newtons, E is the electric field strength and q is the charge in
Coulombs. For a 1 Farad capacitor charged to 1 volt and an insulating layer thickness of
0.1mm; use the three equations above to determine the force between the two plates of the
capacitor.
Task 2: Does temperature influence maximum motor torque?
An electric motor works by forcing the motion of a rotor using one or more switched
magnetic fields. The force of the magnetic field developed by an electromagnet and hence
torque of the motor is proportional to the current flowing through the motor windings. When
stalled, the relationship between the voltage, current and resistance of electricity moving
through the motor windings follows the classic relationship of:
V=IR, or R=V/I or I=V/R
The Length, Material and Cross Sectional Area of the conductor in an electric motor are
constant, but the temperature of the motor will vary considerably during use depending on
how hard it is being worked and the effectiveness of cooling by the surrounding environment.
To investigate the effect of changing temperature on the maximum torque of the motor we
can conduct an experiment to look at how temperature impacts the current flowing through
the motor windings at a given voltage.
Resources:
1. Variable 5V DC Power supply
2. Ammeter
3. Multimeter
4. Connecting wires with alligator clips
5. Brushless motor winding (Warning! - note that placing a DC voltage across the terminals
of a brushed motor will cause the motor to rotate. To avoid confusion it may be better to use a
motor winding only rather than a whole motor, or a standalone electromagnet if available.
Always use a low voltage during the experiment to limit the possibility of injury should a
motor be incorrectly identified)
6. Esky with ice and hot water
7. Thermometer
Experiment:
In this experiment we will measure the changes in current through the motor winding at
different temperatures to infer changes in maximum motor torque and calculate the
relationship between temperature and resistance for the copper wire of the motor windings.
Procedure:
1. Place the motor winding in an esky of ice water and to allow it to equilibrate. Use the
thermometer to measure the temperature of the ice water.
2. Construct a test circuit consisting of a power supply and an ammeter in series with
two alligator clips ready to connect to the poles of the motor windings.
3. Set the power supply initially to 0 volts.
4. Take the brushless motor winding out of the esky and place it on a towel, noting the
temperature on the thermometer. With as little delay as possible, connect two of the
motor windings to the test circuit using the alligator clips and then carefully increase
the voltage on the power supply until the ammeter is close to full deflection. Note the
voltage, current and temperature (converted to degrees kelvin) in the table below.
5. Leaving the Voltage setting on the power supply unchanged, repeat the experiment
after placing the motor windings in tap water and hot water (use a jug and boiling
water if available – tie a string around the winding and wear gloves to prevent burns).
6. Develop a graph of temperature v’s current and resistance for the motor winding
7.
8. Discuss the effect of temperature on the conductivity of the motor windings and the
implications of your experiment for maximum motor torque