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Human Energy Generation
and Electrical Signal Measurement
Energy Generation and Usage
Earth’s Energy Balance
Yearly energy resources (TWh) Solar energy absorbed by atmosphere, oceans, Earth[1] 751,296,000.0 Wind energy (technical potential) [2] 221,000.0
Yearly energy consumption (TWh)Electricity (2005) [3] -45.2 Primary energy use, non-electric (2005) [4] -369.7
From Wikipedia, 2008-11-20:1. Smil (2006), p. 12 2. Archer, Cristina. "Evaluation of Global Wind Power". Stanford. Retrieved on 2008-06-03. (72 TW at 0.35 capacity factor) 3. "World Total Net Electricity Consumption, 1980-2005". Energy Information Administration. Retrieved on 2008-05-25. 4. "World Consumption of Primary Energy by Energy Type and Selected Country Groups, 1980-2004". Energy Information Administration. Retrieved on 2008-05-17.
Energy Generation: Solar
The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately 3,850 zettajoules(ZJ) per year.In 2002, this was more energy in one hour than the world used in one year.Photosynthesis captures approximately 3 ZJ per year in biomass.The amount of solar energy reaching the surface of the planet is so vast that in one year it is about twice as much as will ever be obtained from all of the Earth's non-renewable resources of coal, oil, natural gas, and mined uranium combined. From Wikipedia, 2008-11-20, http://en.wikipedia.org/wiki/Solar_power
U.S. Energy Sources
Petroleum 38%Natural Gas 26%Coal 22%Nuclear 8%Renewable 6%
U.S. Energy Usage
http://en.wikipedia.org/wiki/Energy_conservation
Energy Information Administration, http://www.eia.doe.gov/emeu/aer/pecss_diagram.html, 2008-11-20
Wikipedia, 2008-11-20, http://upload.wikimedia.org/wikipedia/commons/a/a0/World_Energy_consumption.png
World Power Capability versus Time
Wikipedia, 2008-11-20, http://upload.wikimedia.org/wikipedia/commons/0/0b/Energy_consumption_versus_GDP.png
Power Demands per Country per GDP
Energy: Definitions and Units
Energy Definitions 1
Energy: The ability to do work.Power: The rate of energy usage.
An energetic person is not necessarily powerful or forceful, why?
dttdEtP )()(
t
EdPtE0
)0()()(
Energy Measures: Units
1 Btu777.9 ft-lbs
1055 joules=1055 watt-sec252 calories
0.000293 kilowatt-hour
Power Measures: Units
1 hp2545 Btu/hr
550 ft-lbs/sec178.2 cal/sec745.7 watts
Energy Definitions 2
Usually measure power, then integrate to get energy generated or used.
Mechanically, power equals force times velocity, or torque times rotational speed,
Electrically, power equals voltage x current,)()()()()( ttTtxtFtP
)()()( tItVtP
Fundamental TheoremsOf Electromagnetic Energy
Generation
Ampere’s Law
Charge in motion, I(t) ,creates a magnetic flux, .
Flux always comes out of the north pole, according to the right-hand rule.
)(t
I(t))(t
I
Ampere’s Law states that an electric current produces a magnetic field. The magnetic field curls around the current using the right-hand-rule, that is, with your right thumb pointing in the directionof the current, your fingers point in the direction of the magnetic field.
Faraday’s Law
A changing magnetic field creates a voltage (or current).
dttdNtV )()(
Lenz’ Law
Current is induced so as to oppose a changing magnetic field.
Faraday’s Law states that a changing magnetic field produces a voltage. For a coil with N-turns, the magnitude of the voltage is equal to the number of turns multiplied by the rate of increase or decrease of the magnetic flux inside the coil, V = -N(d/dt).
N
S
Magnet velocity
N
S
Magnet velocity
I I
Lenz’ Law states that current is induced so as to oppose a changing magnetic field.
Lorentz Force Equation
Explains forces acting on charged particles in electric and magnetic fields.
A charged particle moving in a magnetic field will be deflected. If the velocity of the particle is
perpendicular to the magnetic field, the particle will deflect perpendicularly to the plane of the velocity
and the magnetic field.
vqqFvq
F
A Simple AC Generator
N
S )(t
)(t
Tdt
tdNtV )()(
N
S
)(t
)(t
T
iron iron
Electrical Energy Generation
N
S
+
-
Working fluid
(water, steam)
Turbine, drives generator
Permanent Magnet DC-Motors
Permanent magnet DC-motors can also act as DC generators. They rectify the output voltage using a mechanical commutator. Often the coil rotates in a magnetic field.
IDC by Lorentz force eqnN
S
+
-
VDC commutator
A diode is needed to prevent stored energy in the battery from driving
the motor backward.(We will use this overall arrangement for the
experiment.)
N
S
+
-
VDC commutator
IDC
Energy Storage
Electrical Energy Storage
Two different metals and an electrolyte-separator are required for an electrochemical cell.
According to Benjamin Franklin, a collection of individual cells is called a battery.
Cell voltages depend on the metals involved.
An Electrochemical Cell Discharging
Electrolyte+Electrode Interface
Voltage
Current Current
e-
qs
e-
qd+
- ElectrodeInterface
No load voltage
ions diffusing
Cell Voltages
Non-rechargeable or primary cellsDry cell 1.5V per cell
Rechargeable or secondary cellsLead-acid cell 2V per cellNiCad 1.2V per cellNiMH 1.2V per cellLi-ion 3.7V per cell
Comparison of Various Chemistries
From wikipedia, rechargeable batteries, 2008-24-2008
Battery Management
Some newer chemistries require great effort for battery management systems (BMS) to
prevent cell damage due to overcharge, overdischarge, overcurrent, overtemperature, while maintaining charge balance among the
cells.
Older chemistries, such as lead-acid, allow some overcharge, which works to balance the
cells. We will use lead-acid cells.
Humans as Energy Sources
Energy Generation and Storage
Power = Voltage * Current
Energy = Power * Time, or
0
( ) ( )t
E t P d 1 2 3( ) nE n t P t P t P t P t
Windstream DC generator
DC ammeter
DC voltmeter
portable power pack
http://www.windstreampower.com/Human_Power_Generator_Series.php
Humans as energy sources
2008-11-20, http://www.recumbents.com/mars/tetz/E-Assist.htm, John Tetz
Source to Load Matching
Component Matching 1
All humans have a maximum power-out point, with an individualized torque and speed.
This maximum power point is easily matched to a load by having gears on a bicycle. Using gears, the human can continue to operate at the maximum power-out point for any load.
Component Matching 2
A DC generator is chosen to be attached to the bicycle wheel so that it will be able to
provide as much power as the human can generate, assuming about 80% efficiency in
the generator.
From the human power vs time plot, a 300W generator should be adequate for most
people.
DC generator power curves
2008-11-20, http://www.windstreampower.com/443902_PMDCG.php
Component Matching 3
The storage battery nominal voltage should be chosen in conjunction with the DC
generator voltage output.
If the DC generator can produce 15V out, then a single deep-cycle 12V lead-acid
battery will work. The size of the battery, and thus the weight, depends on how much charge and energy you want to store.
Energy Conversion and Usage
Kill-a-wattAC Watt-hours out
Energy efficiency is watt-hours removed divided by watt-hours stored
portable power packAC appliance
http://www.windstreampower.com/Human_Power_Generator_Series.php
Inverters
Inverters are power-electronic devices that convert DC to AC. Many families presently
have these in their automobiles. These devices convert 12V DC to 120 Vrms AC.
The power rating of the device determines its size and cost.
Component Matching 4
The inverter should be chosen so that its input voltage matches that of the storage
battery.
Fortunately, most inverters are designed to operate at about 12V in order to function with
standard lead-acid batteries.
Matching Battery to Inverter to Load
When attaching devices to the 120V AC inverter output, it is important that the power
rating of the inverter not be exceeded.
Many inverters have some overcurrent(overpower) protection, but users should do a
power calculation before attaching the AC loads.
The Lab
Measurements and Calculations
Power = Voltage * Current
Energy = Power * Time, or
0
( ) ( )t
E t P d 1 2 3( ) nE n t P t P t P t P t
Windstream DC generator
DC ammeter
DC voltmeter
portable power pack
http://www.windstreampower.com/Human_Power_Generator_Series.php
Energy Conversion and Usage
Kill-a-wattAC Watt-hours out
Energy efficiency is watt-hours removed divided by watt-hours stored
portable power packAC appliance
http://www.windstreampower.com/Human_Power_Generator_Series.php
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