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Advanced Photovoltaic Systems

AET 230-8204 Notes-Week 3

The highlight of this week is our Guest:

James Caling, Electrical Engineer

James has experience with PV design, large commercial, project management, site supervision & site inspections.

James is due to arrive at 12:30pm.

Johan Alfsen, QuickmountPV

Johan is the Dealer Trainer for QuickmountPV

You can see some good videos at

Johan will do a demonstration and give us some hands on time with the flashed mounting system.

They are located in Concord, CA and ship their product everywhere.

Johan is due to arrive at 10:30am.

Ryan Jones, Electrical Engineer (our classmate)

Will do a Power Point presentation on the p-n junction and how the semi-conductor properties of silicon make electricity from light.

Think of doing your own presentation for extra credit.

PV News

Just released was the World PV Industry Report Summary. You can see it here at:

Here you can see how Spain in 2008 passed Germany as the number 1 PV installer and that 82% of the installations in the world were in Europe in 2008.

Stimulus money is here

Grid Alternatives with AmeriCorps is looking for employees.

Here is the link:

Field Trip on May 2 with Tony Diaz

This is an aerial image of the 200kW system we will visit.

The address is 2000 San Pablo Ave. in Oakland and it is the Alameda County Social Services building. (click on the picture for directions).

Topics for this week:

System Components & Configurations

PV cells, Types, Characteristics & Inverters

(Chapters 4, 5 & 8 in the book Photovoltaic Systems)

Components & Configurations

The main focus of this class will be battery-less, grid-connected, utility-interactive systems, although we will go over some of the other components briefly.

Component definitions:

Inverter-convert DC current to AC current

Battery-electrochemical energy storage

Flywheel-kinetic energy storage

Capacitor-store charge (supercapacitors store more)

PCU-power conditioning unit (often in the in the inverter housing) often called the inverter for simplicity.

Charge controller-regulates battery charging

Rectifier-converts AC to DC

Charger-A rectifier with filters, transformers, etc. to charge batteries with.

DC to DC converter-change voltage

Maximum Power Point Tracker (MPPT)-changes input voltage in order to maximize power from PV on IV curve

Configuration definitions:

Utility-interactive-grid tied-PV/inverter/utility-parallel to the grid-our main focus of study

Stand-alone-operates independent of the grid

Bimodal-can act alone or with the grid, charging batteries if the grid is down with PV

Battery backup-has batteries that will work when the grid is down until the batteries go dead. Will not charge batteries when the grid is down.

PV cell types (typical)

Monocrystalline-from one crystal-solid color and square with rounded edges usually. More efficient.

Here is a link to where you can see where they are selling silicon:

Polycrystalline-Multiple crystals-usually square shaped with rainbow hues. Almost as efficient.

String Ribbon-Made like bubbles with a string. Here is a link to the process:

Thin film-There are various types of thin film PV. Half as efficient. Has better thermal characteristics.

Here is a link to the latest on thin film:


p-n junction-where the conversion of light to electricity happens

n-type semiconductor-the top of the cell facing the light which is doped with phosphorous. This is the negative charge side of the cell where the electrons come from

p-type semiconductor-the bottom of the cell where the boron doping is. The boron is melted with the silicon before the crystal is made.


High frequency inverter-lighter without iron core transformer-less surge capacity and by some considered lighter duty. Fronius inverters are very light.

DC to AC (20,000 Hz) to DC to AC

Low frequency inverter-Has an iron core transformer and is heavy. SMA inverters are low frequency.

DC to AC (60 Hz) to transformer

Transformerless not common in the US. Ungrounded without transformer. Can be bipolar. Common in Europe & may become more common here in the future.

Power factor has to do with the current and the voltage being in phase. When everything is in phase, it is called a resistive load and the power factor is 1. When it is out of phase, it is called a reactive load and the power factor is less than 1.

Inverters only generate a power factor of 1.

Your electric bill is for reactive power.

You can measure PF (Power Factor) with a Kill A Watt

According to Marvin Hamon, EE, the other instructor of AET 230

"Large inverters over 100kW almost never work out of the box & you need a factory representative to make them work."

AC modules: they are a thing of the future. We have not seen one yet.

An Enphase inverter is not factory wired to a module.

Enphase is a microinverter and there is a lot of interest, especialy from high-tech consumers.

Enphase has said that they will come to our class for a talk. You can see their product at

Remember, next week is spring break, so don't come to class.

In 2 weeks, the subjects we will cover are system sizing & mechanical integration, which you can read about in chapters 9 & 10 of the book Photovoltaic Systems. We will have a presentation by Brian Swanson of Fidelity Roof Company.

Quiz with answers:

quiz week 3 answers.pdf (PDF — 34 KB)