Dan O. Popa, Intro to EE, Spring 2015 EE 1106 : Introduction to EE Freshman Practicum Lab - Lecture: Maximum Power Transfer Nonlinear Circuit Elements Photovoltaic Effect

Dan O. Popa, Intro to EE, Spring 2015 Thevenin and Norton Equivalents

Dan O. Popa, Intro to EE, Spring 2015 Norton Equivalent

Dan O. Popa, Intro to EE, Spring 2015 Maximum Power Transfer Maximum power transfer when R s =R L (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 RLC Circuit as a Linear System Kirchoff’s Voltage Law (KVL):

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- Diode 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 Transistor use: Digital Inverter 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: Wikipediahttp://

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

Dan O. Popa, Intro to EE, Spring 2015 Next Time: Dynamical Circuits (RC, RL, RLC) 17