48550 Electrical Energy Technology48550 Electrical Energy Technology

Electrical Energy SystemsElectrical Energy Systems• Energy Resources

• Electrical Energy Generation• Utilisation of Electrical Energy

• System Design Examples– Electrical Vehicles

– Remote Area Power Supply

– Grid Power Supply

Energy ResourcesEnergy ResourcesEnergy

The capacity for doing work. The SI unit for energy is Joule.

Main Energy Forms* Electrical * Mechanical * Chemical

* Solar * Geothermal * Nuclear

Energy ResourcesEnergy resources are the various material that contain energy inusable quantities. These are present in any of the various energy forms that are transformable to other forms.

Expendable Resources: fuels (e.g. coal, oil, & natural gas)

Renewable Resources: water, wind, solar, tide, and biomass

Electrical Energy GenerationElectrical Energy Generation-- Conventional Methods: HydroelectricConventional Methods: Hydroelectric

Electrical Energy GenerationElectrical Energy Generation-- Conventional Methods: HydroelectricConventional Methods: Hydroelectric

Electrical Energy GenerationElectrical Energy Generation-- Conventional Methods: ThermoelectricConventional Methods: Thermoelectric

Electrical Energy GenerationElectrical Energy Generation-- Conventional Methods: ThermoelectricConventional Methods: Thermoelectric

Electrical Energy GenerationElectrical Energy Generation-- Conventional Methods: ThermoelectricConventional Methods: Thermoelectric

Electrical Energy GenerationElectrical Energy Generation-- Conventional Methods: NuclearConventional Methods: Nuclear

Electrical Energy GenerationElectrical Energy Generation-- Conventional Methods: Nuclear (Cont.)Conventional Methods: Nuclear (Cont.)

In a nuclear power plant, the heat energy released by nuclear fission is used to produce the steam that rotates the turbine that drives the electric generator.

Electrical Energy GenerationElectrical Energy Generation-- NonNon--conventional Methodsconventional Methods

• Thermionic Converters

• Electrochemical Cells

• Solar Power– Solar Cells

– Solar Thermoelectric

• Biomass

• Ocean Power

• Geothermal Power

• Wind Power

• Hybrid Power Systems

• Very high growth predicted– Recent European Commission

white paper on renewable energy sources

– Rooftop programs in Europe, USA, Japan

– 5.5% renewable generation by 2010 in USA

– 2% renewable generation by 2010 in Australia

• 25% average growth rate

Solar PowerSolar Power-- Solar CellsSolar Cells

Solar PowerSolar Power-- Solar ThermoelectricSolar Thermoelectric

BiomassBiomass Geothermal Power PlantGeothermal Power Plant

Ocean PowerOcean Power• Oceans cover three quarters of the

earth’s surface and represent a vast natural energy resource in the form of waves

• The World Energy Council estimates that 2TW of energy could be harvested from the world’s oceans, the equivalent of twice the world’s electricity production

• If less than 0.1% of the renewable energy within the oceans could be converted into electricity it would satisfy the present worlddemand for energy more than five times over

(from www.wavegen.co.uk)

Ocean PowerOcean Power–– Energy densityEnergy density

• Figures in kW/m• Source: Wave Energy paper, IMechE, 1991 and European Directory of

Renewable Energy (Suppliers and Services) 1991

Ocean PowerOcean Power-- FacilityFacility Wind PowerWind Power

Wind GeneratorsWind Generators

• Installed world-wide end 1997 7700 MW

• Generated energy 19 TWh p.a.

• Germany has largest capacity 2002 MW

• Market is growing 22 % p.a.

• Average size 600 kW, doubling in last 5 yrs

• (Snowy Hydro 10,000 GWh = 10 TWh p.a.)

Fuel CellsFuel Cells-- FundamentalFundamental

• The electrolyte provides a physical barrier to prevent the direct mixing of the fuel and the oxidant, allows the conduction of ionic charge between the electrodes, and transports the dissolved reactants to the electrode.

• The electrode structure is porous, and is used to maximise the three-phase interface between the electrode, electrolyte and the gas/liquid, and also to separate the bulk gas phase and the electrolyte.

• The gas/liquid ionisation or de-ionisation reactions take place on the surface of the electrode, and the reactant ions are conducted away from or into the three-phase interface.

Hydrogen

Oxygen

Electricity

Heat

Water

FUEL CELL

Load

Depleted Fuel andProduct Gases Out

H2

Negative Ion

Positive Ion

Fuel In

2e-

Anode

½ O2

CathodeElectrolyte(Ion Conductor)

Depleted Oxidant andProduct Gases Out

Oxidant In

H2O H2O

Fuel CellsFuel Cells-- PrinciplePrinciple

Anode reactionCathode reactionOverall reaction

−+ +→ eHH 222

OHeHO 2221 22 →++ −+

OHHO 22221 →+

Fuel CellsFuel Cells-- StructuresStructures

Fuel

OxidantDC Power

Control

Control

Con

trol

Hea

t

Reactants

Application

Heat

Fuel CellStack

FuelManagement

Unit

HeatManagement

Unit

ControlUnit

UnprocessedFuel

Oxidant

PowerConditioning

Unit

Fuel CellsFuel Cells-- ClassificationsClassifications

CLASS ABBREVIATION

Solid Oxide SOFC

Polymer Electrolyte Membrane PEMFC

Phosphoric Acid PAFC

Molten Carbonate MCFC

Alkaline AFC

Fuel CellsFuel Cells-- Fuel requirementFuel requirement

Gas species PEMFC AFC PAFC MCFC SOFC H2 Fuel Fuel Fuel Fuel Fuel CO Poison(>10ppm) Poison Poison(>0.5%) Fuel Fuel CH4 Diluent Diluent Diluent Diluent/Fuel Diluent/Fuel CO2 and H20 Diluent Poison Diluent Diluent Diluent S (as H2S and COS)

Unknown Unknown Poison Poison (>0.5ppm)

Poison (>1ppm)

Fuel CellsFuel Cells-- ElectrochemicalElectrochemical

Fuel CellsFuel Cells-- ApplicationsApplications

ACF MCFC

SOFC

PEM FC

PAFC

TYPICALAPPLICATIONS

Portable electronicsequipment.

Cars, boats, anddomestic CHP.

Distributed powergeneration, CHP,and buses.

MAINADVANTAGES

Higher energydensity to batteries,faster recharging.

Potential for zeroemissions, higherefficiency.

Higher efficiency,less pollution, quietoperation.

POWER (W) 1

APPLICATIONRANGE FORFUEL CELLCLASS

10 100K10K1K100 1M 10M

Fuel CellsFuel Cells-- Advantages and disadvantagesAdvantages and disadvantages

Advantages• Efficiency - Fuel cells are generally more efficient than combustion engines

as they are and are not limited by temperature as is the heat engine.• Simplicity - Fuel cells are essentially simple with few or no moving parts.

High reliability may be attained with operational lifetimes exceeding 40,000 hrs.

• Low emissions - Fuel cells running on direct hydrogen and air produce only water as the by-product.

• Silence - The operation of fuel cell systems are very quiet with only a few moving parts if any. This is in strong contrast with present combustion engines.

Disadvantages• Relatively high cost of the fuel cell, and• to a lesser extent the source of fuel.

Hybrid Power Hybrid Power SystemsSystems

Electrical Power TransmissionElectrical Power Transmission Electrical Power TransmissionElectrical Power Transmission-- SubstationSubstation

Utilisation of ElectricityUtilisation of Electricity

• Industrial Applications– Motor drive systems, e.g. machine tools

– Electrical furnaces

• Domestic Electrical Appliances– TV, air conditioning, and washing machine, etc.

• Computer Peripherals– Disk drives (floppy, hard disk and CD), printers,

etc.

Solar powered submersible water pumpSolar powered submersible water pumpCSIRO-UTS project• brushless DC,

NdFeB, 4 pole, surface magnet

• water filled

• >1000 produced

• 300, 600, 1200 W

• sensorless, current impulse starting

• MPPT

BrushlessBrushless DC Transmission DC Transmission Drives for Electric CarsDrives for Electric Cars

• Electric Lotus Elise - Zytek

• Ethos 3 EV - Pininfarina & Unique Mobility

• EV Plus - Honda

• Prairie Joy - Nissan

• RAV-4-EV - Toyota

Electrical VehiclesElectrical Vehicles

InIn--wheel Motors wheel Motors -- Solar CarsSolar Cars• CSIRO-UTS / Aurora - 5.5 kW, 50 Nm peak for 72 s

• Direct-drive, axial flux

SolarSolar--Wind Hybrid FerryWind Hybrid Ferry• Solar Sailor/UTS - 2x40 kW, 400 Nm

• Direct-drive, PM brushless DC motor

• The concentrations of green house gasses in the atmosphere have increased over recent year and are still increasing.

• The increased concentrations of green house gasses will have some effect on the earth’s climate.

Green House Green House EffectEffect

Kyoto ProtocolKyoto Protocol-- Japan, December 1997Japan, December 1997

• 55 nations agreed to implement measures to reduce emissions to stabilize the global environment

• 38 industrialized nations agreed to reduce their 1990 level greenhouse emissions by 8% in 2008-2012

• European Union committed to reduce with 8%• The US by 7%• Japan by 6%• Australia’s “eventual” target of 8%

How to RHow to Reduce COeduce CO22 EmissionsEmissions??• Use clean energy source for electricity generation, e.g.

solar, wind, hydro, geothermal, and nuclear (?)

• Reduce power loss in power transmission lines

• Use high efficiency electrical appliances in households and industry

• Since motors account for 65% of the electric energy consumed in industrial applications, it is important to– Select right motor size (motor selector software package)

– Use high efficiency motors, e.g. PM motors

– Use high efficiency electric drive techniques, e.g. variable speed, direct drive

• Total annual consumption 50,000 GWh = 50 TWh

• Average household in Sydney consumes 20 kWh per day, 7,300 kWh p.a.

• Snowy Hydro 10,000 GWh = 10 TWh p.a.

• Largest wind farm (to be) Crookwell 5 MW power maximum, 10 GWh p.a. energy generation

• Australian Greenhouse commitment requires extra 2% = 10 TWh p.a. electricity generated by clean energy source by 2010

AustralianAustralianElectrical EnergyElectrical Energy

0

5

10

15

20

25

30

0.75-7.5 >7.5-37 >37-75 >75

M otor power (kW )

Annual saving (T Wh)

Desired efficiency

Mandatory

Best available now

Energy Saving from Induction Motor Energy Saving from Induction Motor Efficiency Improvement in Europe by 2010Efficiency Improvement in Europe by 2010

• For best available now, 28 TWh, 3% of motor consumption, 62% from motors in the 0.75-7.5 kW range

– increase of efficiency from 80 to 86%

– large number of units (83% of the total)

750 W Evaporative Cooler Fan 750 W Evaporative Cooler Fan Energy ConsumptionEnergy Consumption

• 200 W power saving at 600 rpm

– 50,000 units p.a., 25% duty cycle

– 22 GWh saved p.a.

– $50 per unit = 11.4c per kWh saved p.a.

• Crookwell 5 MW wind farm

– 10 GWh p.a.

– $2000 per kW

– $1.00 per kWh saved p.a.

Fan motor input power

0

200

400

600

800

1000

1200

0 500 1000 1500

Speed (rev/min)

Po

wer

in (

W)

Triac V V control Inverter 1 Inverter 2

Triac variable voltage

Inverter drives

Integrated VVVF Drive for 750 Integrated VVVF Drive for 750 W Evaporative Cooler FanW Evaporative Cooler Fan

• The Drive PCB a) attached to a heat sink for testingb) Mounted in the motor end plate with other required components

(a) (b)

Integrated VVVF Drive for 750 Integrated VVVF Drive for 750 W Evaporative Cooler FanW Evaporative Cooler Fan

• The assembled prototype motor and drive

Efficiency of 750 W Evaporative Efficiency of 750 W Evaporative Cooler Fan DrivesCooler Fan Drives

• Comparison of efficiency between a commercial 750 W triac controlled fan drive and the prototype inverter VVVF drive

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

0 200 400 600 800 1000 1200 1400 1600

Speed (rev/min)

Efficiency (%)

Triac Drive VVVF Drive

Future DirectionFuture Direction-- PMPM brushlessbrushless DC and SR motorsDC and SR motors

• PM brushless DC motors are more efficient (typical efficiency 90-95%) than induction motors, but more expensive.

• The cost can be reduced by using position sensor-less drive techniques and when PM materials become cheaper.

• The switched reluctance motors can be both more efficient and cheaper, but sensor-less drive still needs more work.

Single Phase

AC Supply

AC/DC

ConverterSensor-lessElectronic

PMMotor

DC Link

C C

L

3 Ph Square

SpecifiedSpeed

Commutator

Position

Wave Voltage

Refrigerator EfficiencyRefrigerator Efficiency

• Denmark: Variable speed PM motor compressor gave 40% reduction in energy use (Pedersen and Andersen EPE’97)

• USA: 1993 National Appliance Energy Conservation Act– maximum energy levels for

refrigerators, e.g. 732 kWh/year for a 570 L refrigerator-freezer

– to be lowered further by around 30% in 2001

Refrigerator Refrigerator EfficiencyEfficiency

• Mandatory energy labeling in NSW

• could reduce energy used by up to 50%