D-NEXT ACADEMY

Renewable energy technologies

By: Hitesh Avhad sir
UNIT NO -2 SOLAR PHOTOVOLTAIC
SYSTEM
Introduction to Photovoltaic (PV) Technology

• Photovoltaic technology changes sunlight (solar energy) into

electricity.
• “Photo” means light and “Voltaic” means electricity.
• The sunlight contains small energy packets called photons.
• When photons hit a special material (called semiconductor, like
silicon), they can release electrons.
• These free electrons create an electric current, which is how we get
electricity from the sun.

Photovoltaic Effect

• The photovoltaic effect is the direct conversion of sunlight into

electricity using semiconductors.
• When photons hit the semiconductor:
o They give energy to electrons.
o If the energy is more than the “band gap”, electrons jump to the
conduction band and become free.
o These free electrons move and generate electric current.

Advantages of PV Technology

1. No moving parts.
2. No need for fuel like coal or petrol.
3. No pollution.
4. No transport of fuel – sunlight is everywhere.
5. Solar energy is freely and widely available.
6. Long life of the system and low maintenance.

Semiconductor Technology

• Semiconductors like silicon are used in PV cells.

• Pure silicon has no free electrons.

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 • To make it useful:
o Add Boron (3 electrons) → creates a hole (positive) → called
p-type.
o Add Phosphorus (5 electrons) → gives extra electrons
(negative) → called n-type.
• When a p-type and n-type are joined, it makes a p-n junction.
• This junction is the heart of a solar cell.

How Solar Cell Works

1. Sunlight hits the cell.

2. Photons from sunlight hit the p-n junction.
3. Energy from photons releases electrons and holes.
4. Electrons move from n-type to p-type.
5. This movement creates electricity.
6. Metal contacts on both sides help the current flow to an external
circuit (like a light bulb or battery).

Construction of Solar PV Cell

A typical solar cell has:

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 1. n-type layer (top): Thin and transparent (about 0.2 μm), doped with
Phosphorus.
2. p-type layer (bottom): Thick (about 300 μm), doped with Boron.
3. Front metallic grid: Collects electrons.
4. Back metal contact: Acts as the positive end.

When sunlight hits:

• Photons pass through the n-layer and reach the p-n junction.
• Electrons and holes are created.
• Electric current flows if the cell is connected to a load.

A single PV cell typically produces 0.45 volts and 0.75 amps.

Working of Solar PV Cell – Step by Step

1. Sunlight (photons) hits the solar cell.

2. Energy from photons excites electrons in the semiconductor.
3. Electrons move from n-type to p-type.
4. Holes move from p-type to n-type.
5. If connected to a device (load), electricity flows.
6. This process continues as long as sunlight is available.

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Efficiency of Solar Cell

• Efficiency = (Electric power output) ÷ (Solar power input)

• It depends on:
o Material used (e.g., silicon)
o Design
o Manufacturing quality
o Testing conditions
• Maximum theoretical efficiency: Around 25%.

Factors Limiting Efficiency of Solar PV Devices:

1. Reflection Losses: Some sunlight gets reflected from the surface of

the solar cell and doesn’t enter inside.
2. Thin Cell Issue: If the cell is too thin, it cannot absorb all light
properly.
3. Unused Photon Energy: Some photon energy is not used because it’s
either too low or too high.
4. Collection Loss: Not all generated charge (electrons/holes) is
collected.
5. Voltage Loss: Some energy is lost inside the cell, reducing the voltage.
6. Fill Factor Loss: Power output is not perfect due to shape of current-
voltage curve.
7. Resistance Loss: Loss due to wires inside the cell (series and shunt
resistance).
8. Incomplete Collection: Some electron-hole pairs do not reach the
junction.
9. Internal Resistance: Reduces overall current and power.
10. Unstable Voltage: Output voltage keeps changing due to sunlight
variations.

Advantages of Solar PV Cells:

1. Directly convert sunlight to electricity.

2. Can generate from microwatts to megawatts.

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 3. Work well in remote areas.
4. Can work for a long time without anyone handling them.
5. Very long life.
6. No moving parts (less maintenance).
7. Work silently.
8. Pollution-free, eco-friendly.
9. Very reliable.
10. Easy to operate and take care of.
11. Easy to make.
12. Can start with very little sunlight.
13. Solar energy is free and unlimited.

Disadvantages of Solar PV Cells:

1. Only about 20% of sunlight is converted into electricity.

2. Need large space to install more panels for more power.
3. PV modules are costly.
4. Need batteries or backup due to cloudy or night times.
5. High initial cost.
6. Voltage output is not steady.
7. Generates only small amount of power per cell.

Solar PV Module:

• A PV module is a group of solar cells joined together.

• Reason: A single cell gives very small power and is not protected.
• Covered with transparent glass and sealed to avoid damage.
• Usually, 32 or 36 cells are joined in a module to charge a 12V battery.
• Modules are non-divisible, waterproof, and give DC power.

Solar PV Panel:

• A solar panel is a group of modules joined in a metal frame.

• Series connection: Voltage adds up, current stays same.
• Parallel connection: Current adds up, voltage stays same.
• Used when higher power is needed than a single module can give.

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Solar PV Array:

• A solar array is a group of panels arranged together.

• Stepwise:
1. Cells → String (series of cells)
2. Strings → Module
3. Modules → Panel
4. Panels → Array
• Delivers DC power when sunlight hits it.
• Can be fixed or have solar trackers to follow the sun.
• Must be installed without shadows falling on each other.

Solar Photovoltaic (PV) System –

What is a Solar PV System?

A Solar PV system converts sunlight into electricity using solar panels. This electricity
can be used for homes or sent to the electric utility grid.

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Main Components of a Solar PV System:

1. PV Array:
o Group of solar panels.
o Converts sunlight into DC electricity.
2. Charge Controller (Power Conditioning Unit – PCU):
o Protects battery from overcharging or over-discharging.
3. Battery:
o Stores electricity for use at night or during cloudy weather.
4. Inverter:
o Converts DC (12V) from solar panels to AC (240V or 415V) for
use in homes and industries.
5. Other Parts:
o Mounting structures, cables, switches, etc.

Working of Solar PV System:

• Sunlight hits the PV cell (made of silicon).

• Generates electrons (electricity).
• Single cell gives small power, so multiple cells are combined →
Module → Panel → Array.
• DC power can be:
o Used directly,
o Stored in battery,
o Converted to AC for appliances,
o Sent to grid (if extra power is produced).

Types of Solar PV Panels (Based on Generation):

1st Generation – Traditional Crystalline Panels:

1. Monocrystalline (Mono-SI):
o Made from single silicon crystal.
o High efficiency (17–20%).
o Expensive.
o Uniform dark color.
o Works better in hot weather.
2. Polycrystalline (Poly-SI):
o Made from melted silicon.
o Lower efficiency (12–14%).

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 o Cheaper.
o Bluish color.
o Less efficient in hot climate.

Tip to identify:

• Dark color = Monocrystalline

• Bluish color = Polycrystalline

2nd Generation – Thin Film Panels:

1. Thin Film Panels (TFSC):

o Made by placing thin layers of material like silicon, cadmium,
copper on a surface.
o Flexible and low cost.
o Lower efficiency.
2. Amorphous Silicon (A-Si):
o Triple-layer tech.
o Cheap, flexible, good for indoor uses (calculators, clocks, etc.).
o Shorter life.

3rd Generation – Advanced Panels (Still in R&D):

1. Cadmium Telluride (CdTe):

o Low cost, quick payback.
o Uses less water.
o Toxic – must be handled carefully.
2. Concentrated PV (CPV):
o Uses lenses/mirrors to focus sunlight.
o Very high efficiency (~41%).
o Needs solar trackers and cooling.
3. Biohybrid Panels:
o Experimental panels using organic materials.

Types of Solar PV Systems (Based on Application):

1. Grid-Connected Solar PV System:

• Connected to the power grid.

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 • No battery needed – grid stores extra power.
• If solar power is more than needed → excess sent to grid.
• If less → power taken from grid.
• Stops working when grid is down (for safety).

Advantages:

• Low cost and maintenance.

• No battery needed.
• Efficient.

Disadvantages:

• Doesn’t work during power cuts.

Applications:

• Homes, malls, hotels, schools, etc.

2. Off-Grid or Stand-Alone System:

• Works independently of the grid.

• Used in remote areas.

Two Types:

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 1. Without Battery (Direct Coupled):
o Solar panel directly powers DC load (like water pumps).
o Works only when sunlight is available.
2. With Battery:
o Stores solar power in batteries.
o Can power both DC and AC loads.

Advantages:

• Good for remote places without electricity.

Disadvantages:

• Battery is needed (adds cost).

Applications:

• Solar lanterns, street lights, water pumps, village homes, etc.

3. Hybrid Solar PV System:

• A Hybrid PV System uses more than one source to generate

electricity.
• The main source is always a solar photovoltaic (PV) system.
• The second source can be:
o A renewable source (like a windmill), or
o A non-renewable source (like a diesel generator), or

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 o Electricity from the utility grid.

Main Components:

1. PV Array – Converts sunlight into DC electricity.

2. Charge Controller – Controls charging of batteries.
3. Battery Storage – Stores excess electricity for later use.
4. Rectifier – Converts AC to DC if needed.
5. Inverter – Converts DC from PV/battery to AC for home use.
6. Loads – Can support both DC and AC appliances.
7. Backup Source – Windmill / Diesel Generator / Grid.

Key Feature:

• Works for both DC and AC loads at the same time.

Advantages of Solar PV Systems

1. Modular system – Can be made small or big by adding more panels.

2. No need for long transmission lines – Can be installed near the
usage point.
3. Low maintenance – No moving parts.

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 4. Environment friendly – No pollution or greenhouse gases.
5. Works in remote areas – Stand-alone systems are possible.
6. Silent working – No noise.
7. Reliable and durable – Long-lasting.
8. Long life – Good performance for many years.

Disadvantages of Solar PV Systems

1. High initial cost – Buying and installing is expensive.

2. Low efficiency in bad weather – Less power on cloudy/rainy days.
3. No power at night – Needs storage.
4. Expensive batteries – Storage makes the system costlier.
5. Needs large space – More panels need more area.
6. Transport and setup cause pollution – Though running is clean.
7. Toxic materials – Some harmful materials used in manufacturing.

Applications of Solar PV System

Solar PV systems are used in many places for power generation. Some common
applications are:

1. Water pumps – For irrigation and drinking water in villages.

2. Navigation lights – For guiding ships at ports.
3. Community radios and TVs – In rural or remote areas.
4. Cathodic protection – Prevents corrosion in oil pipelines.
5. Weather stations – For climate and weather monitoring.
6. Railway signals – To run railway equipment in remote areas.
7. Battery charging – For personal or public use.
8. Street lights – Especially useful in remote locations.
9. On-site power supply – For houses, offices, or farms.
10. Satellites – Main power source in space.
11. Meteorology tools – For data collection and analysis.
12. Marine warning lights – Used on buoys or sea markers.
13. Telecom towers – In isolated or off-grid areas.
14. Microwave towers – For communication relay stations.

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Charge Controllers (or Regulators)

A charge controller protects the battery in a solar PV system. It manages the charging
and discharging process.

Why it's needed:

• Prevents overcharging (which can damage the battery).

• Prevents deep discharge (which reduces battery life).

Working:

• Turns ON charging when battery voltage is low.

• Turns OFF charging when battery is full.

Operating Modes:

1. Normal Mode – Battery voltage is within safe range.

2. Overcharge/Over-discharge Mode – Voltage goes above or below
safe range.

Types of Charge Controllers (used in stand-alone systems):

1. Shunt Type – Cuts off charging by short-circuiting the solar panel.

2. Series Type – Uses a switch to disconnect the solar panel from the
battery.
3. MPPT Type (Maximum Power Point Tracking) – Always extracts
maximum power from the solar panels using a smart circuit.

Installation of Grid-Connected Solar Rooftop Systems

Step-by-step Procedure:

1. Layout Planning
o Plan the position of panels and rails on paper.
o Mark where to fix footers (support anchors).
o Use chalk to draw lines and mark drill points.
2. Install Footers and Rails
o Fix the support structure securely on the rooftop.
3. Prepare for PV Module Installation
o Start attaching parts of the solar panel frame.
4. Install Microinverters and Ground Wire

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 o Fix microinverters on rails.
o Connect them together.
o Ground them properly (to prevent electric shocks).
o Pull wire to the junction box location.
5. Install Junction Box
o Mount the box near the array.
o If using microinverters, connect A.C. cables.
o If using string inverters, use D.C. cables.
6. Mount PV Modules
o Fix the first panel carefully and connect it.
o Repeat for the rest of the panels.
7. Connect All Modules
o Attach all panels to inverters or optimizers.
8. Install Wiring and Conduits
o Run cables from the rooftop box to the main control system
inside the house.
9. Install Ground-Level Equipment
o Fix inverters, shutdown controls, disconnect switches, meters,
and breakers.

Stand-Alone Solar Street Light System

Main Components:

1. SPV Module (Solar Panel) – Converts sunlight into electricity.

2. Foundation – Strong base to support the pole.
3. Module Mounting Structure – Holds the solar panel.
4. LED or CFL Lamp – Used for lighting.
5. Light Pole – Holds all components at a height.
6. Control Box – Contains:
o Battery
o Charge Controller
o Wiring
7. Battery Stand – For keeping the battery safe and elevated.

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Installation Steps:

1. Foundation Preparation:

• Choose an open area with direct sunlight.

• Dig a pit: 80 cm × 80 cm × 80 cm.
• Insert a steel cage (with bolts).
• Pour concrete to fix the cage firmly.

2. Pole Preparation:

• Place pole on 1 m high support.

• Pass solar cables through pole to the top.
• Fix solar panel and lamp (LED/CFL) on top.

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3. Control Box Installation:

• Attach metal box to pole.

• Insert battery and controller inside.
• Make correct wiring as per the diagram.

4. Erection of Pole:

• Lift and fix the pole on foundation bolts using a crane.

• Tighten bolts and apply oil to prevent rust.
• Fill cement around the base and cover screws.

Advantages of Solar Street Light:

1. Independent from electricity grid.

2. Low maintenance.
3. No external wiring – fewer accidents.
4. Pollution-free power.

Disadvantages:

1. High initial cost.

2. High risk of theft.
3. Dust or snow may block sunlight.
4. Batteries need replacement after some years.

Typical Specifications:

Recent Trends in Solar PV:

• Technology improved, cost decreased.

• Solar power now cost-competitive.
• Global use: Over 120 countries, 40,000 MW capacity installed.
• Silicon solar cells are most used (93% market share).
• Thin film and concentrators help reduce cost.
• Large-scale projects are increasing.

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Future Trends in Solar Energy:

1. Solar Tower Plants:

• Use mirrors (heliostats) to reflect sunlight on a central receiver.

• Generates steam for electricity.

2. Solar Satellites:

• Solar panels in orbit convert sunlight to microwaves.

• Energy is sent to Earth and converted to electricity.

3. Electro-Chemical Plants:

• Sunlight splits water into hydrogen and oxygen.

• Hydrogen used as clean fuel in fuel cells.

Government Promotional Schemes:

1. Subsidy on Installation:
o Up to 30% (General states)
o Up to 70% (Special states)
2. Incentives:
o Tax holiday (10 years)
o Accelerated depreciation
o Generation-based incentive (up to ₹12/kWh)
o Zero customs & excise duty
o 100% FDI allowed
3. Loans:
o Concessional loans from World Bank, ADB, NDB via SBI, PNB,
Canara Bank.
4. SECI Scheme:
o 500 MW grid-connected rooftop projects
o 30% subsidy for residential and institutional sector

Net Metering:

o Allows users to export extra power to the grid

o Meter tracks electricity import/export
o Users pay only for net electricity use

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Advantages of Net Metering:

1. Reduced Electricity Bills – Sell excess power to grid.

2. No Need for Large Batteries – Grid stores your extra power.
3. Low Maintenance – Only solar panel and inverter needed.
4. Job Creation – Boosts employment in solar sector.
5. Supports the Grid – Helps balance peak demand.

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