Start: The Technical Basics >>>


You are intending to purchase a Photovoltaic system?
 Where and how to start, what is important to consider, how to calculate the efficiency and return-on-investment  ... Our guideline 5 steps to your solar system

Photovoltaic power plants convert sunlight to electric energy. This is obvious. But how does it work and what are the componetns of a PV system?

Get an technical introduction here. Before you start with planing your photovoltaic system or hiring an installer make sure to understand at least the technical basics. Only if you understand the basics you can go ahead in an efficient and good way and you are able to compare any quotations from solar installation companies.

Solar energy sounds complicated to many folks, but compared to other kinds of power systems it is fairly easy. Learn how a solar PV system works:

A/  How a Grid-Connected Solar Photovoltaic System Convert Sunlight to Electricity

How a Solar Photovoltaic System Works

 

(1) Photovoltaic modules convert sunlight to electricity. The modules are typically connected to "strings". The modules in each string is connected in series, which leads to a higher voltage. The total voltage of the string is the sum of each module. Whereas the current (Ampere) keeps constant. The PV modules generate DC electricity - or direct current - sending it to the solar inverter.

(2) The solar inverter transforms the DC power into AC (Alternating Current)  electricity for ordinary household needs.

(3) (4) The electricity produced during the daytime is either used by the property owner, or directed back into the electricity grid and purchased by a utility company, an arrangement called 'net metering'.

 

B/  Types of Photovoltaic Modules

Manufacturing Process PV Module

Photovoltaics (PV) modules are arrays of cells containing a solar photovoltaic material that converts solar radiation into direct current electricity. Solar cells conducting an electrical current and producing electricity from sunlight - the so called photovoltaic effect.

Materials presently used for photovoltaics include monocrystalline and polycrystalline silicon or cadmium telluride, and copper indium selenide/sulfide. Silicon is the main component of quartz sand and, after oxygen, is the second most common element in the Earth's crust.

Photovoltaic nominal power capacity is measured as maximum power output under standardized test conditions (STC) in "KWp" (Kilowatts peak). The higher the efficiency of the solar cells, the less surface area required.

There are 3 common types of commercial solar cell used today:

  • Monocrystalline,

  • Polycrystalline,

  • Thin Film Modules.

Differences: 

  Type of Cell  

Efficiency  

  Surface Area required for 1 KWp  

  Comments  

Monocrystalline 

 13% - 15%

 Around 8 spm (86 sq ft)

Highest efficiency = least surface area required  

Polycrystalline

10% - 13%

Around 10 spm (86 sq ft) 

 Good efficiency at reasonable cost

Most common used today

Thin Film

 Amorphous

 5% - 7%

Around 18 spm (194 sq ft)

 Low efficiency = large surface area, low costs

 Works better in diffuse light than mono & polycrystalline and often used for roofs with east or west direction

 

C/ The Physics

The yearly sum of solar radiation changes with the region. The further south you are living (on northern hemisphere) and the more sunshine in your region the better is the so called global radiation (insolation). With other words the more solar electricity you can harvest from your photovoltaic system. The maximum values of solar radiation occur south and north of the equator.

Solar Electricity Potential in Europe and USA:

Photovoltaic - Radiation Map

Source: JRC European Commision, Solar Radiation Map, http://re.jrc.ec.europa.eu/pvgis/cmaps/eur.htm

Photovoltaic - Radiation Map North Amercia

 Source: NRL , Solar Radiation Map North America, http://www.nrel.gov/

 

 

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