INTRODUCTION TO ENERGY SCIENCE Wind for Schools Webinar: August 12 th, 2010

Ability to do work or cause change Produces Warmth Produces Light Produces Sound Produces Movement Produces Growth Powers Technology What is energy? Courtesy of NEED

POTENTIAL KINETIC Stored energy or energy of position Gravitational, Stored Mechanical, Nuclear, Chemical Energy of motion Motion, Electrical, Sound, Radiant, Thermal Classes of Energy Courtesy of NEED

Gravitational Energy – energy an object or substance has because of its position Anything “up high” Potential Energy

Stored Mechanical Energy – stored in an object by the application of force Must push or pull on an object Potential Energy

Nuclear Energy – energy stored in the nucleus of an atom Holds the atom together Nuclear Energy – energy stored in the nucleus of an atom Holds the atom together Potential Energy

Chemical Energy – energy stored in the bonds between atoms Holds molecules together Potential Energy

Mechanical (Motion) Energy – movement of objects or substances from one place to another Kinetic Energy

Electrical Energy – movement of electrons NOT AN ELECTRON PARADE! Kinetic Energy

Sound Energy – movement of energy through substances in the form of longitudinal/compressi on waves Kinetic Energy

Radiant Energy – electromagnetic energy that travels in transverse waves Kinetic Energy

Thermal (Heat) Energy – internal energy of a substance due to the vibration of atoms and molecules making up the substance

1 – Energy can not be created nor destroyed, only changed. Law of Conservation of Energy First Law of Thermodynamics 2 – Energy will always transfer from high to low. 3 – No energy transfer is 100% efficient. Energy Transfers

Conservation of Energy

Units of Energy Energy requires a force. Each form of energy has it ’ s own force: gravity, strong & weak nuclear forces, electrical, and kinetic forces.  Kinetic Force = Mass x Acceleration  Unit of force = 1 Newton = 1 Kilogram x 1 m/s Energy is a measurement of work accomplished by a force  Energy = Force x Distance  1 Joule = 1 Newton x 1 Meter

Energy and Power  Energy is a quantity, like distance.  1 kilowatt-hour = 1000 Watts x 1 hour  1 kilowatt-hour = 3.6 x 10 6 Joules  Power is a rate, like speed, it is the rate that energy is converted from one form to another.  1 Watt = 1 Joule / Second

The Difference Between Energy and Power Energy Power Quantity Rate Unit kWh kW, MW* Water analogy Gallons Gal / Min Car analogy- - How far? - Gallon of gas - How far? - Gallon of gas Engine HP Cost example 12 ¢/kWh $1,500,000/MW Grid Consumption & production Installed capacity

Laws of Thermodynamics  First Law: In any transformation of energy from one form to another, the total quantity of energy remains unchanged. “ Energy is neither created nor destroyed, it only changes forms. ”  Second Law: In all energy changes, the potential energy of the final state will be less than that of the initial state – (useful energy is always lost.)  “ Lost ” energy is usually energy that has been converted to heat, but it could be noise (kinetic energy of air), or other forms of wasted energy.

Efficiency  The ratio of the amount of useable energy obtained to the amount of energy input is the efficiency of a process.  This is usually expressed as a percent and it is always less than 100%.

Energy definitions  Primary Energy – amount of energy contained in the initial source of energy  Delivered Energy – amount of useable energy delivered to the customer  Useful Energy – amount of energy attributed to the amount of work accomplished

What is Electricity? Electricity is energy transported by the motion of electrons Electricity is energy transported by the motion of electrons **We do not make electricity, we CONVERT other energy sources into electrical energy** Conversion is the name of the game

Energy Conversion Options for Electricity Non-Thermal Paths Source to Electrical SourceConverter SunPhotovoltaic (photon to electron) ChemicalFuel Cell Source to Potential/Kinetic to Mechanical to Electrical SourceConverterKinetic to MechanicalMech to Electrical DamPenstocksTurbine (water)Generator TidesMachineTurbine (air or water)Generator WindN/ATurbine (air)Generator

Energy Conversion Options for Electricity Thermal Paths Heat to Mechanical to Electrical SourceHeat to MechanicalMech to Electrical GeothermalTurbine (vapor)Generator OTECTurbine (vapor)Generator Stored Energy to Heat to Mechanical to Electrical SourceReactor Heat to Mechanical Mech to Electrical FuelCombustorTurbine (gas or vapor)Generator U, PuReactorTurbine (gas or vapor)Generator SunCollector*Turbine (gas or vapor)Generator H, H 2, H 3 ReactorTurbine (gas or vapor)Generator * More a modifier or concentrator than a reactor

Faraday Effect Basic Concepts Voltage – V – Potential to Move Charge (volts) Current – I – Charge Movement (amperes or amps) Resistance – R – V = IxR (R in =ohms) Power – P = IxV = I 2 xR (watts)

Electric Motor M Electrical Energy Mechanical Energy DC Motor

Model Electric Motor Beakman Motor What do you need? 1.Electric Energy 2.Coil 3.Magnetic Field 1.Electric Energy 2.Coil 3.Magnetic Field

Electric Generator G Mechanical Energy Electrical Energy Stationary magnets - rotating magnets - electromagnets

AC/DC (not the band)  Alternating Current  Large-scale generators produce AC  Follows sine wave with n cycles per second  1, 2, 3-phase?  US:120 V,60 Hz  Europe: 240 V,50Hz  Transforming ability  Direct Current  Batteries, Photovoltaics, fuel cells, small DC generators  Charge in ONE direction  Negative, Positive terminals  Easy conversion AC to DC, not DC to AC

Generator Phases 1 Phase – 2 Phase – 3 Phase…Smooth Power Polyphase Systems  3 phases for smoother torque delivery Force Driving Motor (Red) Single Phase Two Phase Three Phase

WHERE DO WE GET ENERGY FROM AND WHAT DO WE USE IT FOR?

Energy Sources  Non Renewable  Fossil Fuels  Natural Gas  Shale Oil  Tar Sands  Nuclear Fusion Fuel  Renewable  Solar  Geothermal  Tidal

Solar  Direct Sunlight  Wind  Hydroelectric  Ocean Currents  Ocean Thermal Gradients  Biomass

World Primary Energy Consumption

Energy Consumption Versus GDP

2008 US Energy Flow

US Energy Consumption

Alaska Energy Consumption

 The United States uses more energy per capita than any other country in the world, and Alaska as a state has the highest energy per capita energy use in the narration at 1112 MMBtu per person. This is three times higher than the national average of 333 MMBtu.  This is due to our cold harsh winters, high level of air travel  43% of total energy is from jet fuel most of which is for international flights.

Alaska Energy Consumption

Climate Change Logic 1. The Burning of fossil fuels cause carbon dioxide concentrations to rise. 2. Carbon dioxide is a greenhouse gas. 3. Increasing the greenhouse effect increases average global temperatures (among other impacts)

“Does Skeptic mean a person who has not looked at the data?”

1000 years of CO2 Concentration

1000 Years of Temperature Changes

Every Year an Average Coal Plant Releases  3,700,000 tons of CO2  10,000 tons of SO2.  500 tons of particulates  10,200 tons NOx  720 tons of CO  220 tons of volatile organic compounds (VOC)  170 pounds of mercury  225 pounds of arsenic  114 pounds of lead And there are over 600 of them in the US. Source: Union of Concerned Scientists:

Types of Pollutants  CO 2 – Global Warming  CO – Health problem  PM – Respiratory and heart disease, haze  SOx – Acid Rain, respiratory illness, haze  NOx – Ozone formation, acid rain, smog, nutrient loading, global warming  Mercury – Neurotoxin  Lead – Neurotoxin  Arsenic - Poison  VOCs – Numerous health problems  Ozone – Health problems, damage to flora & fauna  Hundreds of other toxic chemicals

Power in the Wind Power = Work / t = Kinetic Energy / t = ½mV 2 / t = ½( ρ Ad)V 2 /t = ½ ρ AV 2 (d/t) = ½ ρ AV 3 d/t = V Power in the Wind = ½ρAV 3

A couple things to remember…  Swept Area – A = π R 2 (m 2 ) Area of the circle swept by the rotor.  ρ = air density – in Colorado its about 1-kg/m 3 Power in the Wind = ½ρAV 3 R

Example – Calculating Power in the Wind V = 5 meters (m) per second (s) m/s ρ = 1.0 kg/m 3 R =.2 m >>>> A =.125 m 2 Power in the Wind = ½ ρ AV 3 = (.5)(1.0)(.125)(5) 3 = 7.85 Watts Units= (kg/m 3 )x (m 2 )x (m 3 /s 3 ) = (kg-m)/s 2 x m/s = N-m/s = Watt Power in the Wind = ½ρAV 3 (kg-m)/s 2 = Newton

Wind Turbine Power Power from a Wind Turbine Rotor = C p ½ ρ AV 3  C p is called the power coefficient.  C p is the percentage of power in the wind that is converted into mechanical energy. What is the maximum amount of energy that can be extracted from the wind?

 Betz Limit when a = 1/3  V ax = 2/3V 1  V 2 = V 1 /3 Actuator Disk Model of a Wind Turbine Where Free stream velocity, V 1 Wake velocity, V 2 =(1 2a) Velocity at rotor, V ax = V 1 (1- a) Induction factor, a Rotor Wake Rotor Disc

Tip Speed Ratio Capacity Factor

Reality Check  What’s the most power the.6 ft turbine in the example can produce in a 5 m/s wind? 7.85 Watts x.5926 (Betz Limit) = 4.65 Watts

Maximum Possible Power Coefficient

Tip-Speed Ratio Tip-speed ratio is the ratio of the speed of the rotating blade tip to the speed of the free stream wind. ΩR V = ΩR R Where, Ω = rotational speed in radians /sec R = Rotor Radius V = Free Stream Velocity

Blade Planform Types Which should work the best?? Rectangular Reverse Linear Taper Linear Taper Parabolic Taper

Airfoil Nomenclature w ind turbines use the same aerodynamic principals as aircraft α V R = Relative Wind α = angle of attack = angle between the chord line and the direction of the relative wind, V R. V R = wind speed seen by the airfoil – vector sum of V (free stream wind) and ΩR (tip speed). V ΩRΩr V

Airfoil Behavior  The Lift Force is perpendicular to the direction of motion. We want to make this force BIG.  The Drag Force is parallel to the direction of motion. We want to make this force small. α = low α = medium <10 degrees α = High Stall!!

Airfoil in stall (with flow separation) Stall arises due to separation of flow from airfoil Stall results in decreasing lift coefficient with increasing angle of attack Stall behavior complicated due to blade rotation

 Gradual curves  Sharp trailing edge  Round leading edge  Low thickness to chord ratio  Smooth surfaces Making Good Airfoils Good Not so good

Energy Production Terms Power in the Wind = 1/2  AV 3 Betz Limit - 59% Max Power Coefficient - C p Rated Power – Maximum power generator can produce. Capacity factor –Actual energy/maximum energy Cut-in wind speed where energy production begins Cut-out wind speed where energy production ends. Typical Power Curve

Performance Over Range of Tip Speed Ratios Power Coefficient Varies with Tip Speed Ratio Characterized by Cp vs Tip Speed Ratio Curve

Considerations for Optimum Blade Optimum blade will have low solidity (10%) and tip speed ratio, λ, about 5-7. (match speed to generator) High λ means lower pitch angle (blade tip is flat to the plane of rotation). Lower λ means higher pitch angle (feathered). Pitch angles should be equal for all blades. Optimum blade has large chord and large twist near hub and gets thinner near the tip. Optimum blade is only "optimum" for one tip speed ratio. The optimum blade will have smooth streamlined airfoils.

Number of Blades – One  Rotor must move more rapidly to capture same amount of wind  Gearbox ratio reduced  Added weight of counterbalance negates some benefits of lighter design  Higher speed means more noise, visual, and wildlife impacts  Blades easier to install because entire rotor can be assembled on ground  Captures 10% less energy than two blade design  Ultimately provide no cost savings

Number of Blades - Two  Advantages & disadvantages similar to one blade  Need teetering hub and or shock absorbers because of gyroscopic imbalances  Capture 5% less energy than three blade designs

Number of Blades - Three  Balance of gyroscopic forces  Slower rotation  increases gearbox & transmission costs  More aesthetic, less noise, fewer bird strikes