in Solar Energy

March 28, 2019
A Complete Guide to Solar PV Modules:

The working principle of a solar PV module is harnessing radiant heat and light energy from the sun and converting that energy into electrical energy using photovoltaic effect.

A basic solar PV system consists of 4 essential components:

1) PV cells- It is the smallest unit of a solar PV system.

2) Solar PV modules- Several PV cells wired either in series or parallel interconnection, encapsulated with a transparent material (mostly tempered glass) on the front side and protective waterproof covering on the rear side make a solar PV module.

3) PV panels: a group of PV modules assembled makes a PV panel.

4) PV arrays: a solar PV array consists of groups of PV modules and panels connected to form a complete power-generating unit. A single PV cell produces a tiny amount of electric power, which is around 1 watt to 2 watts. This amount is too low for practical applications. So, the connection assembly has several (usually 36 PV cells) solar PV cells:

a) wired in “parallel” interconnection to produce a higher electric current, or

) wired in “series” to produce a higher voltage.

A solar PV module traps the solar energy; converts this energy into direct current (“DC”) electricity. A PV inverter converts this DC into an alternating current (“AC”) electricity for its end-use application.

PV cells are made up of light semiconductor materials. Based on the production technologies for PV modules, there are broadly two categories.

A) Crystalline Silicon: Crystalline cells made up of pure silicon wafers which are 150-200 microns thick.

1) Monocrystalline Silicon (Si)

2) Polycrystalline Silicon (Si)

B) Thin Film(Amorphous): Layers of semiconductor material (0.3 – 2 mm) deposited on the glass or stainless steel make a thin film solar cell

Monocrystalline Si Polycrystalline Si Thin Film (Amorphous)
Module efficiency 15%-20% (highest) 13%-16% 6%-8% (lower)
Warranty period 25 years 25 years 15-25 years
Estimated cost per Watt(W) 60-65 (high) 50-55 (medium) 35-40 (low)
Temperature coefficient (%/°C) -0.4 to -0.5 -0.5 -0.21

Important factors, which affect a PV module efficiency:

a) Solar irradiance: The current produced in a solar panel is directly proportional to the amount of solar energy received.

b) Ambient temperature: Voltage generated in a solar panel will be less if the ambient temperature is high.

c) Effect of insolation: If insolation is less than the amperage is also low while the voltage remains almost constant.

Hence, a solar PV module expressed under three testing conditions known as Standard Test Condition (STC): (1) 1000 W/m² of sunlight (2) 25°C ambient cell temperature (3) spectrum at air mass of 1.5, helps in determining the output. 1-kilowatt peak module is capable of producing 1 kilowatt of power (1kWH) at STC. But it is difficult to produce ideal solar output. Usually, the solar panel output expected is labelled by the manufacturers at the back side of a PV module.

Solar PVs has multi-varied applications from lightening up the household appliances to spacecraft propulsion. Below is the list of few of latest ones:

1) Utility interactive applications: Most solar PVs are installed on the rooftop or mounted on the ground of the buildings as per the space availability. In a grid-connected solar PV configuration, the building has two parallel power supplies. One from the solar PV setup and the other from the Power Grid station. At daytime, when there is a supply of solar energy, the building has the electricity supply from the Solar PV. When there is no or insufficient supply of solar energy to produce PV electricity, then the required electricity supply is fulfilled from the supply by power grid station.

2) Electricity in the remote areas: The other type of setup is Off-grid solar PV setup, done in the rural areas, construction sites or off-shore islands where the power grid stations are far away and tapping the electricity is difficult.

3) As roof tiles: Solar PV technology in solar roof tiles are replacing the conventional tiles in Europe as they are cheaper, only the one-time installation cost is higher, but the resale value of the building increases. It is soon to find its way in the US.

4) Portable device charging: As the number of personal electronic gadgets are increasing so are the means of charging facility increasing. Solar power chargers working on the principle of Solar PV technology are now available in the market that can charge for mobile devices at one time.

5) Electric car-battery charging: With the increasing number of electric cars on roads, and considering the duration of time the cars are parked outside in the sun, charging of electric car batteries can happen by solar PVs panelled on the roof of the electric car bodies.

Conclusion: Solar PV technology is finding broad applications for the reason that PV modules degrade slowly and are reliable. They are fossil-fuel free, and no greenhouse gas emissions happen, thereby making it environment-friendly. One-time installation might be a costly affair, but it comes with many financial incentives such as saving from utility rate hikes, price fluctuations in energy prices, the increase in the property resale value.