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

World Power Capability versus Time Wikipedia, 2008-11-20, http://upload.wikimedia.org/wikipedia/commons/a/a0/world_energy_consumption.png

Power Demands per Country per GDP Wikipedia, 2008-11-20, http://upload.wikimedia.org/wikipedia/commons/0/0b/energy_consumption_versus_gdp.png

Energy: Definitions and Units

Energy Definitions 1 Energy: The ability to do work. Power: The rate of energy usage. P( t) t de( t) An energetic person is not necessarily powerful or forceful, why? dt E( t) P( ) d E(0) 0

Energy Measures: Units 1 Btu 777.9 ft-lbs 1055 joules=1055 watt-sec 252 calories 0.000293 kilowatt-hour

Power Measures: Units 1 hp 2545 Btu/hr 550 ft-lbs/sec 178.2 cal/sec 745.7 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, ) ( ) ( ) ( ) ( ) ( t t T t x t F t P ) ( ) ( ) ( t I t V t P

Fundamental Theorems Of Electromagnetic Energy Generation

Ampere s Law Charge in motion, I(t), creates a magnetic flux,. (t) (t) I(t) Flux always comes out of the north pole, according to the right-hand rule.

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 direction of the current, your fingers point in the direction of the magnetic field. I

Faraday s Law A changing magnetic field creates a voltage (or current). V ( t) N d( t) dt

Lenz Law Current is induced so as to oppose a changing magnetic field.

Lenz Law states that current is induced so as to oppose a changing magnetic field. I I N S N S Magnet velocity Magnet velocity 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).

Lorentz Force Equation Explains forces acting on charged particles in electric and magnetic fields. F q qv F qv 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.

A Simple AC Generator (t) (t) N S S (t) N (t) V ( t) N d( t) dt T T iron iron

Electrical Energy Generation + Turbine, drives generator N Working fluid (water, steam) S -

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. + N S I DC by Lorentz force eqn V DC - commutator

N S 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.) I DC + V DC - commutator

Energy Storage

Electrical Energy Storage Two different metals and an electrolyteseparator 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 Current Current e - No load voltage Voltage e - q s q d + ions diffusing +Electrode Interface Electrolyte Interface - Electrode

Cell Voltages Non-rechargeable or primary cells Dry cell 1.5V per cell Rechargeable or secondary cells Lead-acid cell 2V per cell NiCad 1.2V per cell NiMH 1.2V per cell Li-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 t E( t) P( ) d 0 E( n t) P1 t P2 t P3 t Pn 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 portable power pack AC appliance Kill-a-watt AC Watt-hours out Energy efficiency is watt-hours removed divided by watt-hours stored 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 t E( t) P( ) d 0 E( n t) P1 t P2 t P3 t Pn t Windstream DC generator DC ammeter DC voltmeter portable power pack http://www.windstreampower.com/human_power_generator_series.php