dan o. popa, intro to ee, spring 2015 ee 1106 : introduction to ee freshman practicum lab - lecture:...

Dan O. Popa, Intro to EE, Spring 2015

EE 1106: Introduction to EEFreshman Practicum

Lab - Lecture: Maximum Power TransferNonlinear Circuit Elements

Photovoltaic Effect


Thevenin and Norton Equivalents


Norton Equivalent

VTh

RTha

b

IN RTh

a

b

=

Th Th NV R I ThN

Th

VI

R


Maximum Power Transfer

Maximum power transfer when Rs=RL

(Impedance matching)


Intellectual Themes of EE

• Modularity (ex: device)– Resistor, Capacitor, Inductor, Transistor, Diode, Op-

Amp

• Abstraction (ex. circuit)– Signal, System, Circuit, Block diagrams, Data

flow diagrams (state machines), signal flow graphs

• Modeling (ex: linear)– KVL, KCL equations


Linear Systems have the Superposition Property

• Fundamental Property of Linear Circuits

• Replace all but one source in the circuit with a short (voltage source) or an open (current sources).

• Apply analysis to find nodal voltages.

• Repeat for all sources

• Add all nodal voltages to find the total result.


RLC Circuit as a Linear System

Kirchoff’s Voltage Law (KVL):


Nonlinear Circuit Elements- Diode

Semiconductors (Si, Ge) can be doped with impurities

Image Sources: Internet


Nonlinear Circuit Elements- Diode

Image Sources: Internet


Nonlinear Circuit Elements- Transistor

Image Sources: Textbook


Transistor use: Digital Inverter

Image Sources: Textbook


• Sunlight strikes the cell, photons with energy above the semiconductor bandgap impart enough energy to create electron-hole pairs.

• This separation induces a fixed electric current and voltage in the device. The electricity is collected and transported by metallic contacts on the top and bottom surfaces of the cell.

A typical silicon PV cell is composed of a thin wafer consisting of an ultra-thin layer of phosphorus-doped (N-type) silicon on top of a thicker layer of boron-doped (P-type) silicon.

When sunlight strikes the surface of a PV cell, this electrical field provides momentum and direction to light-stimulated electrons, resulting in a flow of current when the solar cell is connected to an electrical load

Solar cells - PN Junction using PV effect

Source: MIT Solar Decathlon


•silicon (Si), •gallium arsenide (GaAs), •cadmium telluride (CdTe), •copper indium diselenide (CIS), •hydrogenated amorphous silicon.

Solar cells – material and efficiency



In the case of a single-junction device, the efficiency of the solar cell, the ratio of the power produced, and the incident light power are limited.

Photons with energies below the bandgap of the material produce only heat. Excess energy above that needed to generate electron-hole pairs also produces heat.

Power – [W]

Efficiency= Electrical Power/Sun Power

Power density – W/m2 – Irradiance (Flux)

Energy – Wh

Photovoltaic cells are connected electrically in series and/or parallel circuits to produce higher voltages, currents and power levels.

Photovoltaic modules consist of PV cell circuits sealed in an environmentally protective laminate, and are the fundamental building block of PV systems.

Photovoltaic panels include one or more PV modules assembled as a pre-wired, field-installable unit. A photovoltaic array is the complete power-generating unit, consisting of any number of PV modules and panels.

PV Cells, Modules, Arrays



PV Power

Sun Power – [W]

Power density – W/m2 – Irradiance (Flux)

Image Sources: http://www.nrel.gov/gis/solar.html, Wikipedia


Subsystems:DC-AC power inverter,

battery bank,

system and battery controller,

auxiliary energy sources

specified electrical load (appliances).

Direct Coupled PV System

PV Systems



Next Time: Dynamical Circuits (RC, RL, RLC)

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dan o. popa, intro to ee, spring 2015 ee 1106 : introduction to ee freshman practicum lab - lecture:...

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