المــــركــز الوطنــــــي لبحــــــوث الطـــاقــــــة National Energy Research Center PV Modules Characteristics Diala Haddad MSc Energy and Sustainability with Electrical Power Engineering-University of Southampton/UK BSc Electrical Engineering-Jordan University of Sience and Technology

What is a PV module?

Silicon PV cells The silicon PV cell is the basic photovoltaic device that is the building block for PV modules.

Assembling PV cells Cells are attached together with a thin ribbons of wire, top to bottom (in series).

Module Materials

Crystalline based module structure Front surface: mainly glass cover. 1. High transmission 2. Low reflection capability Low iron glass is commonly used because of its low cost, strong, stable, highly transparent Encapsulant: is used to provide a strong bond between the solar cells in the module: 1. Should be stable at different operating temperatures 2.Should be transparent with low thermal resistance. EVA (ethyl vinyl acetate) is commonly used with a very thin layer at the front and back surface of the assembled cells PV cells: is the part which is responsible for producing power. Back surface: It must have low thermal resistance it can be made from Tedlar (thin polymer sheet) or glass.

Frame -lightweight -supports easy assembling -4 seasons suitability, weather resistance frame junction box cable connectors

Junction box frame junction box cable connectors

Connectors MC3 or MC4 solar cell | PVF film | EVA foil | glass | frame | junction box | bypass diode | cable and connectors Cable -Flexible -Resistant against abrasion, chemicals, extreme heat, cold and UV 9

Quality Check  IEC61215: Crystalline silicon terrestrial photovoltaic (PV) modules – Design qualification and type approval.  IEC 61646: Thin film silicon terrestrial photovoltaic (PV) modules – Design qualification and type approval.

Module Circuit Design

Solar Cells in Series Simplest thing to consider is when we have two identical solar cells connected in series Since the cells are in series, the currents will be matched (not a problem as they are identical), voltages will add. Useful for when we want a specific voltage, typical voltages for a single solar cell will be < 0.6 V.

Final Combination + -

Recall the solar cell’s IV-curve Solar Cells in Series

Peak Power of one cell (1.36 W) Peak Power of two cells in series (1.36*2 =2.72 W)

Characteristics of PV modules: The Maximum Power Point The I-V and P-V of a module, if the irradiance and cell temperature are held constant. Locating the MPP (Maximum Power Point)

Characteristics of PV modules: Fill Factor

The fill factor (FF) of a PV module is an important performance indicator. Why is the fill factor important? The Fill Factor (FF) is essentially a measure of quality of the PV module. If the I-V curves of two individual PV modules have the same values of Isc and Voc, the module with the higher fill factor (squarer I-V curve) will produce more power Fill Factor

Curve of high FF panel Curve of low FF panel Fill Factor

Protection Diodes - Introduction IV curve extension: What a solar cell does depends on its bias condition

Protection Diodes - Introduction Diodes are semiconductor devices that allow current to flow in only one direction. The two uses of diodes in a PV module electrical design: – Bypass diodes – Blocking diodes + -

Bypass Diodes Used to pass current around, rather than through a group of cells. Normally reverse-biased (OFF) Permit the power produced by other parts of the array to pass around groups of cells that develop an open-circuit or high resistance condition.

Bypass Diodes Most 36-cell crystalline modules have 2 bypass diodes. Most 60-cell and 72-cell modules have 3 bypass diodes. Size for 1.5 times the module I sc rating. Size for greater than 1.5 times the V oc of cells bypassed. In the junction box

Protection Diodes

Mismatch for Cells Connected in series

Shading Effect- Partial Shading Normal runningPartially shading one Cell 26 In series connected solar cells the current for the chain is set by the current of the worst performing cell.

What a solar cell does depends on it’s bias condition Partial shading: Shift of graph origin 0 current,0 Voltage New operating point of the module X

Shading Effect- Full Shading

Full shading: Shift of graph origin 0 current, 0 Voltage New operating point of the module X

This is called hot spot heating Can severely damage the module

Which diode is ON?

Particulate build up ”Soiling” These particulates block the amount of light reaching the module and therefore reduce the power produced by the module The reduction in power from particulate build up can range from 5%-30% in dry areas.

Snow Snow does not usually collect on the modules, because they are angled to catch the sun. If snow does collect, it quickly melts. Mechanically, modules are designed to withstand golf ball size hail.

Electrical Characteristics of Solar Panels (PV Modules)

STC Conditions Each solar panel, or module, is rated to produce a certain wattage, voltage and amperage under specific conditions, called the STANDARD TEST CONDITIONS (STC) according to EN

STC includes three factors:

Normal Operating cell temperature-NOCT Normal Operating cell temperature-NOCT condition is the case when the PV module operates under the following standard operating condition- SOC 1.Global solar irradiation as 800 W/m² 2.Ambient temperature 20 o C 3.Tilt angle 45° 4.Wind speed of (1 m/s) With the back side of the solar panel open to that breeze, together with the solar spectrum of corresponding AM1.5.

STC versus NOCT

PV module technologies

Polycrystalline module Efficiency: 14% to 17 %. Form: Square to maximize energy yield. Thickness: 0.24mm to 0.3mm. Color: blue, silver, grey, brown, gold and green.

Polycrystalline Comparisons

Monocrystalline module Efficiency: 16% to 21.5%. Form: round, semi round or square shape. Thickness: 0.2mm to 0.3mm. Color: dark blue to black (with ARC), grey (Without ARC).

Thin film Technology Despite the relatively low efficiency per unit area, thin film technology has many advantages: –Better utilization of diffuse and low light intensity. –Less sensitive to higher operating temperature –Less sensitive to shading because of long narrow strip design, while a shaded cell on crystalline module will affect the whole module. –Energy yield at certain condition is higher than crystalline technology.

13% efficiency

Nameplate Ratings versus Real- World Performance (or STC v. PTC)

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