MEV 014: Unit 11 – Solar and Hydropower Energy

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 UNIT 11: SOLAR AND HYDROPOWER ENERGY

11.0 Introduction

The growing demand for energy and the negative impacts of fossil fuels have driven the world towards clean and renewable energy sources. Among them, solar and hydropower energy are the most widely used and sustainable. Solar energy harnesses the sun’s radiation, while hydropower utilizes the energy of moving water to generate electricity. Both are renewable, environment-friendly, and crucial for reducing dependency on fossil fuels. This unit explores the principles, technologies, advantages, and limitations of these two essential energy resources.

11.1 Objectives

After studying this unit, you will be able to:

·         Understand the importance and working of solar and hydropower energy systems.

·         Describe the mechanisms of solar heat transfer and the role of collectors and concentrators.

·         Learn about the applications of solar energy in daily life and industry.

·         Understand the working of hydropower plants and their classification.

·         Compare the advantages and disadvantages of solar and hydro energy.

·         Recognize the current status and potential of both energy sources globally and in India.

11.2 Harnessing of Solar Energy

Solar energy is derived from the sun’s radiation. It can be converted into thermal or electrical energy using various devices. The technology used depends on whether we aim to heat a material or generate electricity.

11.2.1 Heat Transfer Mechanism in Solar Systems

Solar systems transfer heat through three basic mechanisms:

1.      Conduction – Transfer of heat through solid materials.

2.      Convection – Transfer of heat through liquids and gases.

3.      Radiation – Direct transmission of heat energy from the sun to the absorber without any medium.

These mechanisms are vital in designing solar devices like heaters and dryers.

11.2.2 Solar Radiation and Collectors

Solar radiation consists of electromagnetic waves from the sun. Two main types of collectors capture this energy:

·         Flat Plate Collectors (FPC) – Simple design, used in water heating, cooking, etc.

·         Evacuated Tube Collectors (ETC) – More efficient in colder regions.

11.2.3 Solar Thermal Collectors

These collectors absorb solar radiation and convert it into heat. Types include:

·         Flat-plate collectors

·         Evacuated tube collectors

·         Solar ponds

·         Central receiver systems (used in solar power plants)

11.2.4 Solar Concentrators

Solar concentrators focus sunlight onto a small area to increase intensity. Common types:

·         Parabolic Trough

·         Parabolic Dish

·         Heliostat Field with Central Receiver

These are used in generating high-temperature heat for power generation and industrial applications.

11.3 Solar Energy Utilization

11.3.1 Solar Heaters

Used to heat water or air for domestic and industrial purposes. Simple systems use FPCs or ETCs with insulated tanks.

11.3.2 Solar Dryers

Remove moisture from agricultural products using solar heat. Improves food preservation and reduces post-harvest losses.

11.3.3 Solar Cookers

Box-type or parabolic solar cookers use solar radiation for cooking food without fuel. Eco-friendly and cost-effective.

11.3.4 Solar Stills

Used to purify water. Solar radiation heats the water, which then evaporates, condenses, and is collected as clean water.

11.3.5 Solar Electricity Generation – Photovoltaic (PV) Cells

·         Convert sunlight directly into electricity using semiconductors.

·         PV cells are used in homes, calculators, satellites, and solar power plants.

·         Solar panels consist of many PV cells connected in series/parallel.

11.3.6 Solar Photovoltaic Thermal Collectors (PV/T)

These hybrid systems generate both heat and electricity from solar energy. Useful in space heating and power generation.

11.3.7 Advantages and Disadvantages of Solar Energy Systems

Advantages:

·         Renewable and abundant

·         Environmentally clean

·         Low operating cost

·         Suitable for remote and off-grid areas

Disadvantages:

·         High initial cost

·         Intermittent energy (dependent on weather)

·         Requires large area for installation

·         Energy storage needed for night-time use

11.4 Hydroelectric Energy

Hydropower harnesses the energy of flowing or falling water to generate electricity. It is one of the oldest and most widely used renewable energy sources.

11.4.1 Principle and Working of Hydropower Plants

Hydropower plants work on a simple principle:

1.      Water from a reservoir or river is directed to a turbine.

2.      The flowing water turns the turbine blades.

3.      The turbine is connected to a generator that produces electricity.

The amount of electricity depends on the flow rate and head (height).

11.4.2 Classification of Hydropower Plants/Systems

·         Large Hydro Plants – More than 25 MW capacity.

·         Small Hydro Plants – 2 MW to 25 MW.

·         Mini Hydro – Up to 2 MW.

·         Micro Hydro – Up to 100 kW.

·         Run-of-the-river systems – Do not require large reservoirs.

·         Pumped storage – Stores water during low demand and releases during peak demand.

11.4.3 Global and Regional Status of Hydropower

·         Globally: Hydropower contributes about 16% of electricity generation.

·         India: Accounts for about 12% of total electricity generation.

o    Major projects: Bhakra Nangal, Tehri, Sardar Sarovar, Hirakud.

·         Significant potential remains untapped, especially in the Himalayan and North-Eastern regions.

11.4.4 Advantages and Disadvantages

Advantages:

·         Renewable and clean source

·         Provides irrigation and flood control benefits

·         Long life and low operating cost

·         Provides energy storage and grid stability

Disadvantages:

·         High construction cost

·         Displacement of people

·         Disturbance to aquatic life and ecosystems

·         Risk of dam failure and sedimentation

11.5 Let Us Sum Up

Solar and hydropower energy are vital alternatives to conventional energy sources. Solar energy, through thermal and photovoltaic systems, provides versatile applications for homes, industries, and electricity generation. Hydropower remains a major contributor to the renewable energy sector, particularly for large-scale electricity generation. Both sources are environment-friendly and sustainable, though they come with certain limitations like intermittency, high setup cost, and ecological impact. The integration of these renewable energy systems into national energy planning is crucial for ensuring energy security and environmental sustainability in the future.

 

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