Solar Energy: Introduction, Collection, and Applications

Introduction to Solar Energy

Solar energy is the energy derived from the Sun’s radiation, which can be converted into heat, electricity, or mechanical energy using various technologies. It is the most abundant renewable energy source available to humanity and plays a key role in sustainable development.

🔹 Key Facts:

• The Sun emits energy in the form of electromagnetic radiation.
• Earth receives approximately 1.74 × 10¹⁷ watts of solar power continuously.
• Solar energy is non-polluting, sustainable, and available across the globe.

🔹 Relevance to India:

• India lies in the tropical region, receiving abundant sunshine (~300 sunny days/year).
• National Solar Mission aims for 500 GW renewable energy capacity by 2030.

Collection of Solar Energy; Solar energy can be collected and converted through two major methods:

1. Solar Thermal Energy Collection; These systems convert solar radiation into heat energy for various uses.

a) Flat Plate Collectors (FPC)

• A flat, black-painted metal plate that absorbs solar radiation.
• Covered with a transparent glass/plastic sheet to reduce heat loss.
• Water or air is circulated through tubes attached to the plate to collect heat.

🔸 Uses: Water heating, space heating, solar cooking, etc.

b) Concentrating Collectors; These use mirrors or lenses to focus sunlight on a small area to generate high temperatures.

i) Parabolic Trough Collectors

• Long parabolic mirrors focus sunlight on a pipe carrying fluid.
• The heated fluid can generate steam for electricity.

ii) Parabolic Dish Collector (SK-14)

• A parabolic mirror reflects sunlight to a central point.
• Can reach temperature of 400–700°C, suitable for cooking or industrial use.

iii) Heliostats (Solar Tower)

• A field of mirrors tracks the Sun and reflects sunlight to a central tower receiver.
• Used in large-scale solar thermal power plants.

• c) Solar Dryers These use solar heat to remove moisture from agricultural produce.

Types:

• Natural convection dryer: Relies on natural air flow.
• Forced convection dryer: Uses fans powered by PV or electricity.
• Solar Tunnel Dryer: Semi-cylindrical design, used for commercial drying of spices, fruits, vegetables.

2. Solar Photovoltaic (PV) Energy Collection; Photovoltaic cells convert sunlight directly into electricity using the photovoltaic effect.

🔹 Working Principle: When sunlight hits a semiconductor material (usually silicon), it excites electrons and generates a flow of electricity.

🔹 Components of a Solar PV System:

• Solar Panels (Modules)
• Battery Bank (for storage)
• Charge Controller
• Inverter (DC to AC)
• Mounting Structures and Wiring

🔹 Types of PV Systems:

• Off-Grid Systems – With battery storage, used in rural areas.
• Grid-Connected Systems – Feed electricity into the public grid.
• Hybrid Systems – Combination of solar and conventional sources.

Applications of Solar Energy; Solar energy has wide applications across agriculture, domestic, industrial, and community uses:

Agricultural Applications

• Solar Water Pumps; Used to extract groundwater for irrigation. Operate independently of the electric grid.
• Solar Dryers; Used for hygienic and faster drying of grains, fruits, vegetables, and spices. Reduces post-harvest losses and improves shelf life.
• Solar Greenhouses; Structures that trap solar heat for growing vegetables and flowers during winter. Help maintain required temperature and humidity.
• Solar Cold Storage; Maintain temperature for preserving fruits, vegetables, dairy, fish, and meat. Powered by PV panels, ideal for remote areas.
• Solar Fencing; Electrified fencing powered by solar PV. Prevents entry of wild animals and cattle.
• Solar Sprayers; Used for crop protection (pesticides, fertilizers). Lightweight, portable, and economical.

Domestic Applications

1. Solar Cookers; Use solar heat for cooking food.

• Types:
  • Box-type Solar Cooker: Simple and cheap; used for slow cooking.
  • Dish-type Solar Cooker (SK-14): High temperature; suitable for frying, boiling.

2. Solar Lanterns & Solar Home Lighting; Useful for rural electrification, study lamps, and household lighting.
3. Solar Water Heaters; Used for heating water for bathing and cleaning. Saves energy in households, hotels, hospitals.
4. Solar Street Lights; Automatic lighting at night; common in villages, highways, campuses.

Industrial Applications

• Solar Power Plants; Large PV fields or thermal systems produce electricity for supply to the grid. Examples: Bhadla Solar Park (Rajasthan), Pavagada Solar Park (Karnataka)
• Solar Desalination; Purify saline water for drinking or irrigation. Useful in coastal and arid regions.
• Solar Refrigeration; Used for cold chains in food and pharmaceutical industries.
• Process Heat; Solar heat is used for drying, preheating, pasteurization, etc.

Advantages of Solar Energy

Limitations of Solar Energy