The solar cell is the fundamental block of solar photovoltaic(PV) technology. It is a device that converts sunlight into electricity without any intermediate conversion steps. The input to the solar cell is energy in the form of radiation and output from the solar cell is energy in the form of electricity.
As discussed in the previous article that the amount of solar energy reaching the Earth surface in the form of solar radiation is extremely large in amount, many thousand times more than our energy consumption from all other resources. Using solar cell, the solar radiation energy converted into electrical energy which is the most desirable form of energy. Therefore if we manufacturer a large number of solar cells, a huge amount of electricity generated to fulfill our entire energy requirement.
Solar photovoltaic(PV) module
The solar cell is a small device in terms of area and also the electricity generated in the range of 6Wh to 10Wh which is very small compared to our daily electricity need. Therefore, in order to generate more electricity, many solar cells are connected together to form PV module. The number of solar cells to be connected together and the way they are connected together determine the output current and voltage, and the average energy they produce.
Some important features of solar photovoltaic(PV) module
- Output –
PV module generates electricity only when sunlight falls on it. Thus in non-sunshine hours or night, the energy output from PV module is zero.
- Size –
The amount of electricity generated from PV module depends on the physical size of the module, larger is the size, more the output.
- Ratings –
PV modules mainly characterized in terms of their power rating, which is known as ‘peak power’ rating. The unit of power is watt and to emphasize the ‘peak’ power a subscript ‘p’ is added. Therefore peak power symbol of PV module is ‘Wp’. T describes the maximum power that a PV module can produce under STC(standard test conditions).PV modules are available in Wp rating starting from 1Wp to 325Wp like 1Wp, 3Wp, 5Wp, 10Wp, 15Wp, 18Wp, 36Wp, 50Wp, 75Wp, 150Wp, 175Wp, 220Wp, 250Wp, 270Wp, 310Wp, 325Wp etc..
- Storage –
Since PV module generates electricity only during daytime
, therefore for night applications, the storage of electrical energy in batteries is required.
- Conversion –
Electricity generated from PV module is DC (direct current) in nature. The conventional electricity supply available to us is AC (alternating current) in nature. All our appliances like TV, CFL, tube light, refrigerator etc works on AC supply. Therefore, if we want to use PV we must need to convert it into AC. An additional device called ‘Inverter’ is used to convert DC supply into AC, however certain dc types of equipment are available in the market like CFL, DC Bulbs, Fans etc that can be run directly on dc supply.
- Types –
Solar PV modules get different names depending on the types of solar cells used. Commonly available PV modules are monocrystalline silicon PV module, multi/polycrystalline silicon PV module, amorphous silicon PV module, cadmium telluride PV module, CIGS PV module etc. Mono and multi/Polycrystalline modules are the most commonly manufactured and used.
- Array –
PV modules connected together to generate energy at large level. This interconnection of PV module is called ‘PV module Array’.
Solar photovoltaic(PV) system
Electricity generation and its reliable supply to the appliances require not only PV modules but also, several other components that form the complete solar PV system. The other components includes are
For storing electrical energy for nighttime applications and for the time when the demand for electricity is more than its generation. Grid-connected PV systems are battery-less systems.
For converting PV module DC output into AC for general applications. Inverters are available as Grid-tie, Off-grid/stand-alone and Hybrid Inverter.
- Charge controller:
Charge controllers used to protect batteries from overcharge and over discharge conditions, which otherwise reduces the life of the batteries. Two type of charge controllers available depending on the technology used – MPPT or PWM
Solar PV systems characterized depending on the way the energy generated and used.
Categories of solar photovoltaic(PV) system:
Standalone solar PV systems
Grid-connected solar PV systems, and
Hybrid Solar PV systems