Dan O. Popa, Intro to EE, Spring 2015 EE Freshman Practicum Lab - Lecture: Maximum Power Transfer Nonlinear Circuit Elements Photovoltaic Effect
Dan O. Popa, Intro to EE, Spring 2015
EE 1106: Introduction to EEFreshman Practicum
Lab - Lecture: Maximum Power TransferNonlinear Circuit Elements
Photovoltaic Effect
Dan O. Popa, Intro to EE, Spring 2015
Norton Equivalent
VTh
RTha
b
IN RTh
a
b
=
Th Th NV R I ThN
Th
VI
R
Dan O. Popa, Intro to EE, Spring 2015
Maximum Power Transfer
Maximum power transfer when Rs=RL
(Impedance matching)
Dan O. Popa, Intro to EE, Spring 2015
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
Dan O. Popa, Intro to EE, Spring 2015
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.
Dan O. Popa, Intro to EE, Spring 2015
Nonlinear Circuit Elements- Diode
Semiconductors (Si, Ge) can be doped with impurities
Image Sources: Internet
Dan O. Popa, Intro to EE, Spring 2015
Nonlinear Circuit Elements- Transistor
Image Sources: Textbook
Dan O. Popa, Intro to EE, Spring 2015
• 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
Dan O. Popa, Intro to EE, Spring 2015
•silicon (Si), •gallium arsenide (GaAs), •cadmium telluride (CdTe), •copper indium diselenide (CIS), •hydrogenated amorphous silicon.
Solar cells – material and efficiency
Source: MIT Solar Decathlon
Dan O. Popa, Intro to EE, Spring 2015
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
Source: MIT Solar Decathlon
Dan O. Popa, Intro to EE, Spring 2015
PV Power
Sun Power – [W]
Power density – W/m2 – Irradiance (Flux)
Image Sources: http://www.nrel.gov/gis/solar.html, Wikipedia
Dan O. Popa, Intro to EE, Spring 2015
Subsystems:DC-AC power inverter,
battery bank,
system and battery controller,
auxiliary energy sources
specified electrical load (appliances).
Direct Coupled PV System
PV Systems
Source: MIT Solar Decathlon