Menu
Search
3 Photovoltaic Installation Terms To Be Familiar With
3 Photovoltaic Installation Terms To Be Familiar With (150 kilowatt solar photovoltaic array at Food Bank of Northern Nevada; by BlackRockSolar via Flickr)

Photovoltaic (PV) installation

In order to understand a photovoltaic (PV) installation and its components we must be familiar with the following terms:

  1. Standard Test Conditions (STC)
  2. PV modules
  3. PV string and Array

1. Standard Test Conditions (STC)

The output of a PV module is not stable it depends on irradiation, temperature etc., thus, we need fixed conditions in order to compare them, size and design our installation. These conditions are called as standard test conditions (STC):

a) Incident irradiance on the PV module surface: 1000W/m²

The 4 curve of a PV module proportionally to irradiance
Figure 1 – The 4 curve of a PV module proportionally to irradiance

We consider that the output power of the module is the point of the IV curve which shapes the greatest area. As we can see the irradiance influences mostly the current.


b) Cell temperature: 25°C

The output of a PV module proportionally to cell temperature
Figure 2 – The output of a PV module proportionally to cell temperature

We consider that the output power of the modules is the point of the IV curve which shapes the greatest area. As we notice the output voltage of a PV module depends mostly on its temperature.


c) Air Mass: 1.5

The Air Mass is the path length which light takes through the atmosphere normalized to the shortest possible path length (that is, when the sun is directly overhead AM=1).

The Air Mass quantifies the reduction in the power of light as it passes through the atmosphere and is absorbed by air and dust.

The Air Mass is defined as:

AM = 1 / cos(Θ)

Air Mass 1.5
Figure 4 – Air Mass 1.5

Go back to Index ↑


2. PV Modules

All the datasheets include their electrical characteristics data in STC. For instance:

El. characteristicsUnitValue
 Nominal output (Pmpp)W280
 Voltage at Pmax (Vmpp)V36.5
 Current at Pmax (Impp)A7.7
 Open circuit voltage (Voc)V44.5

Go back to Index ↑


3. String and Array PV Modules

Is a series electrical connectivity of PV modules. An example of string is the following:

A string consist of 18 PV modules
Figure 5 – A string consist of 18 PV modules

Assuming that our PV module’s output at STC is: Imp 7A, Vmp 30V, 210W If we will measure at points 1 and 2 we will find: 7A and 540V (18 PV modules X30V) and we get 3,78kW

An example of Array (parallel strings)

Two parallel strings each one consists of 18 PV modules
Figure 6 – Two parallel strings each one consists of 18 PV modules

If we will measure at points 3 and 4 we will find: 14A and 540V (18 PV modules X30V) and we get 7,56kW. Taking in to consideration the above you can understand the attached Single Line Diagram (SLD) of a 2MW plant.

Download SLD

 

Go back to Index ↑

About Author //

author-pic

Erin Ndrio

Erin Ndrio - Electrical & Electronic Engineer. Specialized for design, sizing and energy analysis of a Photovoltaic installation (more than 50 PV projects of Nominal Power > 30MW). Sizing of MV/LV components of a substation. Experienced in MV and LV operations. Expert in AutoCAD.

5 Comments


  1. Arunraj
    Nov 11, 2014

    Enroll me on all activities, am also electrical engineer


  2. christian jacob
    Oct 01, 2014

    Enroll me on all activities, am also electrical engineer.


  3. Kumar
    Sep 27, 2014

    This is something new and creative.


  4. Rudra
    Sep 26, 2014

    Hi Erin, I want to start a solar panels installation business….how should i be prepared for that…kind request to guide me…


  5. Hassan Mohammed
    Sep 26, 2014

    Good work, and keep it up! I am really impressed with the work.

Leave a Comment

Tell us what you're thinking... we care about your opinion!


Get PDF