MED 003: Unit 13 – Solar Energy Technologies

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 UNIT 13: SOLAR ENERGY TECHNOLOGIES

13.0 Introduction

The rising concerns over depleting fossil fuels, energy insecurity, and environmental degradation have prompted a global shift toward renewable energy. Among the renewable sources, solar energy stands out for its abundance, sustainability, and widespread availability. India, located in the tropical zone, receives substantial solar radiation, making solar technologies a crucial component of its renewable energy strategy.

This unit explores solar energy technologies, focusing on both thermal and photovoltaic applications, their working principles, and practical uses in domestic, industrial, and rural settings.

13.1 Objectives

After studying this unit, you should be able to:

  • Understand the basic principles of solar energy conversion.
  • Explain the working and applications of solar thermal and photovoltaic (PV) technologies.
  • Identify various devices used for solar heating and electricity generation.
  • Appreciate the role of solar technologies in sustainable development.

13.2 Solar Thermal Technologies

Solar thermal technologies use solar radiation to heat a fluid or a surface, which is then used directly or indirectly for applications like heating water, cooking, drying, or generating electricity.

13.2.1 The Principle Underlying Solar Thermal Technologies

Solar thermal systems operate on the principle of converting sunlight into heat energy. This is typically done using collectors that absorb solar radiation and transfer the heat to a working fluid—such as air, water, or oil—which is then used in various heating applications.

13.2.2 Devices for Solar Thermal Applications

  1. Flat Plate Collectors (FPCs):
    These are simple panels that collect heat from sunlight and are mainly used for domestic water heating. A flat absorber plate, usually coated with a black surface, absorbs solar radiation and heats up the fluid running through pipes attached to it.
  2. Evacuated Tube Collectors (ETCs):
    These consist of glass tubes with vacuum insulation that reduce heat loss, making them more efficient in colder climates. Common in modern water heating systems.
  3. Solar Water Heaters (SWHs):
    A widely used application, especially in homes and institutions. These heaters can reduce electricity consumption by up to 70% for water heating.
  4. Solar Cookers:
    These use reflective surfaces to concentrate solar rays and cook food. They are economical, portable, and widely promoted in rural India.
  5. Solar Dryers:
    Used in agricultural and industrial settings to dehydrate products such as fruits, vegetables, and herbs, improving shelf life and reducing post-harvest losses.
  6. Concentrated Solar Power (CSP):
    These systems use mirrors or lenses to concentrate a large area of sunlight onto a small area to produce high-temperature heat, often used to drive turbines for electricity generation.

13.3 Solar Photovoltaic Technology

Photovoltaic (PV) technology directly converts sunlight into electricity using semiconductor materials.

13.3.1 The Principle Underlying Solar Photovoltaic Technologies

The PV effect involves the creation of voltage or electric current in a material upon exposure to light. Silicon, the most commonly used semiconductor, is treated to form a p-n junction. When sunlight hits the cell, electrons are knocked loose and flow through the material, generating electricity.

13.3.2 SPV Applications

  1. Home Lighting Systems:
    Stand-alone rooftop PV systems power lights, fans, and small appliances, particularly in rural and remote areas.
  2. Solar Lanterns:
    Portable lighting solutions using PV panels and LED lights. Useful in regions with limited grid access.
  3. Solar Street Lighting:
    Widely deployed in urban and rural areas for public lighting with automatic dusk-to-dawn operation.
  4. Water Pumping Systems:
    Solar PV-powered pumps provide a reliable solution for irrigation and drinking water in off-grid areas.
  5. Mini and Micro Grids:
    Community-based PV systems that supply electricity to clusters of homes or small businesses.
  6. Building-Integrated Photovoltaics (BIPV):
    PV modules integrated into the architecture of buildings—such as roofs and facades—offering both energy and aesthetic benefits.
  7. Grid-Connected PV Systems:
    These systems are connected to the main electricity grid and can feed excess electricity back into the grid through net metering policies.

13.4 Summary

Solar energy technologies, including thermal and photovoltaic systems, offer scalable and sustainable alternatives to conventional energy sources. Solar thermal applications such as water heating and cooking are effective in reducing fuel consumption and promoting clean energy use. Photovoltaic technologies play a critical role in electrification, especially in remote and rural areas.

By tapping into the sun’s immense energy potential, India can move closer to energy self-sufficiency, reduced carbon emissions, and a more resilient energy future.

13.5 Keywords

  • Solar Thermal Energy – Technology that uses sunlight to generate heat.
  • Photovoltaic (PV) Technology – Technology that converts sunlight directly into electricity.
  • Flat Plate Collector – A device used in solar water heaters to collect solar radiation.
  • Solar Cooker – A device that uses solar energy to cook food.
  • Solar PV System – A system comprising solar panels and components to produce electricity.
  • Net Metering – A billing system that credits solar energy system owners for the electricity they add to the grid.

 

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