PV Technology 101

These days everyone has seen or heard of PV or photovoltaics panels, but few know what they are made of and how they really work.  The information provided below is for general knowledge.

The first piece in making a PV module is the solar cell which is made up mostly with Silicon Technology

Types of Silicon Cell
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Monocrystalline

Single crystal, complex and expensive, but also the most efficient. Easy way to recognize is by the white space in between the cells as shown above.

Many crystals resulting from molten silicon poured in a casting. Slightly less efficient and cheaper than monocrystalline. Easily recognized by non-visible white spaces and visible crystal when looking closely

Created by depositing multiple layers of photovoltaic material on substrate. Less expensive, but also tends to be less efficient. More flexible way to use as it does not need to be encased as Monocrystalline or Polycrystalline.

PV Modules and Electricity

These solar cells are the ones that will create electricity once being stoke by the sun. Each solar cell at its P-N junction will create a .5volt Dc potential. When wired in series, 36 cells as shown below on this PV producing about 18V.

When mechanically fastening PV modules together, you get a PV Panel. Wiring and mounting together multiple PV panels will result in the PV array which will have a specific current and voltage.

PV Module Components
  • PV Modules these days come with a “module Quick Connect box” which have a positive and negative conductors coming out of it. These conductors are the ones you will connect to other PV modules or eventually to a homerun which will connect to a DC Combiner box. PV Schematics will be provided in more advance Education Section.
PV Modules characteristics
  • Electricity in your home comes in AC-alternative current.  AC is the current your utility is providing you and most likely every appliance in your home is AC.  PV modules generate electricity that will be DC, and therefore, that DC electricity will need to be converted to AC electricity at the panel levels - Micro-Inverters- or after going through an inverter that will convert DC to AC-This will be explored in more details in more advance Section.
Other PV general characteristics
  • PV generate electricity in DC- see section about DC and AC in later section
  • Irradiance, heat, and shading affect PV output. While irradiance increase the output, both heat and shading lower it.
  • Weight about 3 pounds per square foot for mono and polycrystalline. Important consideration to take for roof loading.
  • Efficiency- panels have different efficiency and while a panel with more efficiency might be more expensive at first, it will produce more watts per square foot. It can be very useful when space is limited.
  • Monocrystalline and Polycrystalline come in different size:
  • Panels are warrantied for up to 25 years for most
  • Most solar panels size for residential is about 65’by 39’ and come with 60 cells. You can get bigger panels that come with 72 cells or even 96, but these are often used for commercial projects.