Jyothy Institute of Technology

DEPARTMENT OF MECHANICAL ENGINEERING

Subject : Renewable Energy Power Plants (REPP) Session : Feb 2025 – June 2025
Subject Code : BME654B (Open Elective) Semester : VIth Sem EC

Module – 1

Syllabus: Introduction to Renewable Energy: Overview of global energy demand and the need
for renewable energy, Comparison of renewable and non-renewable energy sources,
Environmental benefits and challenges of renewable energy.
Solar Radiation: Extra Terrestrial radiation, spectral distribution of extraterrestrial radiation,
solar constant, solar radiation at the earth’s surface, beam, diffuse and global radiation.

Overview of Global energy demand:

Global energy demand refers to the total amount of energy required to sustain human activities,

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including industrial production, transportation, residential consumption, and commercial
operations. As the global population grows and economies expand, energy consumption
continues to rise, driven by increasing industrialization, urbanization, and technological
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advancements. Fossil fuels such as coal, oil, and natural gas have historically dominated energy
supply, but concerns over climate change and resource depletion are pushing a transition
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toward renewable sources like solar, wind, and hydropower. The energy demand varies
regionally, with developed nations consuming high amounts due to industrialization, while
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developing countries experience rapid growth in demand as they modernize. Meeting this
demand sustainably requires energy efficiency improvements, advancements in storage
technologies, and global cooperation in energy policies to balance economic growth with
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environmental responsibility. Global energy demand continues to grow due to increasing

industrialization, urbanization, and population growth. As of 2025, total global energy demand
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is projected to exceed 600 exajoules (EJ) annually, with demand rising at approximately 1-2%
per year.

To better understand the global energy demand distribution, let’s visualize the data using pie
and bar charts. These charts illustrate the contribution of different energy sources to the total
demand

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1. Global Energy demand by Source

Figure 1: Global Energy demand by source

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The world's energy demand is met through a combination of fossil fuels, renewables, and
nuclear energy. The pie chart shown in figure 1 illustrates the global energy demand by source.
• Oil (30%): Dominates the transportation sector, used in cars, ships, and airplanes.
• Coal (20%): Primarily used for electricity generation, especially in developing nations.
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• Natural Gas (24%): Used for heating, electricity, and industrial processes.
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• Renewables (18%): Growing rapidly but still a small share; includes solar, wind, and
bioenergy.
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• Nuclear (6%): Provides stable, low-carbon electricity but has high initial costs.
• Others (2%): A major renewable source but limited by geographical constraints.

2. Energy demand by Sector

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Figure 2: Global Energy demand by sector

Global energy demand is distributed across multiple sectors. The industrial sector is the largest
consumer, followed by transportation, residential, and commercial usage. The pie chart shown
in figure 2 illustrates the global energy demand by sector.
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 • Industrial (40%): Manufacturing, mining, construction, and refining consume vast
amounts of energy.
• Transportation (30%): Includes automobiles, airplanes, ships, and trains, mostly
dependent on oil.
• Residential (18%): Homes use energy for heating, cooling, lighting, and appliances.
• Commercial (10%): Office buildings, malls, and service sectors consume energy for
operations.
• Other (5%): Miscellaneous sectors including agriculture, government services, and
military.

3. Global Energy Demand by Regions

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Figure 3: Global Energy demand by region

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Energy consumption varies significantly by region due to economic growth, industrialization,

and climate conditions. The pie chart shown in figure 3 illustrates the global energy demand by
region.
• Developed Countries (USA, Canada, Europe): High energy consumption per capita,
transitioning towards renewables.
• Emerging Economies (China, India, Brazil): Rapid increase in energy demand due to
industrialization.
• Least Developed Countries (Africa, parts of Asia): Low energy consumption but
increasing demand for electrification

4. The Future of Global Energy Demand

• Energy Efficiency: Smart grids, energy-efficient appliances, and industrial optimizations
can reduce demand.
• Renewable Energy Growth: Investments in solar, wind, and hydropower will increase,
reducing reliance on fossil fuels.

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 • Electrification of Transportation: The shift to electric vehicles (EVs) will reshape the
energy sector.
• Energy Storage & Grid Modernization: Improved battery technology and smart grids will
help balance demand.

The global energy demand is steeply increasing in response to the growing world population,
rising living standards, and ever-increasing industrialization. According to the projection made
by the International Energy Agency (IEA), the global energy demand will double by 2050. Today,
over 80% of the global energy supply is derived from fossil-based fuels such as petroleum, coal,
and natural gas. Besides the depletion of fossil fuel resources, their exploitation, refining, and
combustion have led to large amounts of environmental pollutants. Therefore, energy-efficient
and environment-friendly technologies must be developed and implemented in various sectors
of the economy.

Conclusion

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Global energy demand continues to grow, driven by economic development and population
expansion. While fossil fuels still dominate, a major energy transition is underway, with
renewables gaining ground. Investments in sustainable energy, technological innovations, and
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policy measures will shape the future of global energy consumption.
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Need for renewable energy (Disadvantages of Non-renewable Energy)
The use of conventional energy resources such as coal, oil, and natural gas has significant
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environmental impacts. Some of the key effects include:

1. Air Pollution
• Greenhouse Gas Emissions: Burning fossil fuels releases large amounts of carbon dioxide
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(CO₂), a major contributor to global warming and climate change.

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• Particulate Matter & Smog: Coal and oil combustion produce fine particulate matter
(PM2.5), nitrogen oxides (NOₓ), and sulfur dioxide (SO₂), which contribute to respiratory
diseases and urban smog.
• Acid Rain: SO₂ and NOₓ emissions mix with atmospheric moisture, leading to acid rain,
which harms ecosystems, buildings, and water bodies.

2. Climate Change
• Global Warming: Fossil fuel combustion is the largest source of CO₂ emissions, leading
to the greenhouse effect and rising global temperatures.
• Extreme Weather: Climate change increases the frequency of hurricanes, droughts, and
heatwaves, causing disruptions to ecosystems and human societies.
• Melting Ice Caps & Rising Sea Levels: The warming effect contributes to the melting of
polar ice caps, which raises sea levels and threatens coastal communities.

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3. Water Pollution & Consumption
• Oil Spills: Transport and drilling accidents release oil into oceans, devastating marine
life.
• Thermal Pollution: Power plants using fossil fuels release heated water into rivers and
lakes, disrupting aquatic ecosystems.
• Groundwater Contamination: Extraction and refining processes can lead to the leakage
of toxic chemicals into groundwater supplies.

4. Soil Degradation & Habitat Destruction

• Deforestation & Land Use Changes: Mining and drilling activities clear forests and
disrupt ecosystems.
• Soil Erosion & Contamination: Open-pit coal mining and oil extraction degrade soil
quality, making it unsuitable for agriculture.
• Loss of Biodiversity: Fossil fuel infrastructure threatens wildlife by destroying habitats
and polluting natural areas.

5. Human Health Impacts

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• Respiratory Diseases: Exposure to air pollutants from fossil fuels causes asthma, lung
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cancer, and other respiratory illnesses.
• Toxic Exposure: Heavy metals like mercury and lead released from burning coal affect
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human health.
• Occupational Hazards: Workers in the coal, oil, and gas industries face high risks of
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accidents, lung diseases, and chemical exposure.

6. Resource Depletion & Energy Security

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• Finite Resources: Fossil fuels are non-renewable, leading to concerns about depletion
and future energy security.
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• Geopolitical Conflicts: Competition over oil and gas resources has contributed to
international conflicts and economic instability.

Renewable Energy and Non-Renewable Energy:

Renewable energy: is energy obtained from sources that are essentially inexhaustible. Theses
energy resources are continuously restored by nature. It is so named because they recur are
seemingly inexhaustible and are freely available. solar, wind, Geothermal, hydro power and
oceans are the examples of renewable resources. The most important feature of renewable
energy is that it can be harnessed without the release of harmful pollutants.

Non-renewable energy: is the conventional fossil fuels such as coal, oil and gas, which are likely
to deplete with time. The existence of non-renewable energy sources extremely limited because
the process of their formulation (renewal) needs a very long time (millions of years).

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conventional fossil fuels such as coal, oil and gas, which are likely to deplete with time are
examples of non-renewable resources.

Comparison of renewable and non-renewable energy sources:

The following table represents the comparison between renewable and Non-renewable energy
sources
Sl.
Parameter Renewable Resources Non-renewable Resources
No.
1 Depletion Renewable resources cannot be Non-renewable resources
depleted over time. deplete over time.
2 Sources Renewable resources include sunlight,
Non-renewable resources
water, wind and also geothermal
include fossil fuels such as coal
sources such as hot springs and
and petroleum.
fumaroles.
3 Environmental Non-renewable energy has a
Most renewable resources have low
Impact comparatively higher carbon
carbon emissions and low carbon

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footprint and carbon emissions
footprint and does not harm the
and causes huge harm to the
environment
environment
4 Cost Non-renewable energy has a
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The upfront cost of renewable energy
comparatively lower upfront
is high.
cost.
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5 Infrastructure Infrastructure for harvesting Cost-effective and accessible
Requirements renewable energy is prohibitively infrastructure is available for
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expensive and not easily accessible in non-renewable energy across

most countries. most countries.
6 Area Requires a large land/ offshore area,
Comparatively lower area
Requirements especially for wind farms and solar
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requirements.
farms.
7 Recycling Non-Renewable resources
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Renewable resources can be recycled

cannot be recycled
8 Sustainable These resources are sustainable These resources are not
resources sustainable resources
9 Pollution These resources are eco / environment These resources are not
friendly as low carbon emission and environment friendly and
does not cause pollution causes lots of pollution
10 Usage / These resources cannot be used
These resources can be used again
Depletion again and again as it is limited
and again throughout its life
concern and depleted one day
11 Energy These resources are present in These resources are present in a
limitation unlimited quantity limited quantity

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Environmental benefits of Renewable energy (Advantages of Renewable Energy):
Renewable energy offers several environmental benefits that are increasingly crucial in
combating climate change and reducing environmental impact. Here are some environmental
benefits

1. Reduced Greenhouse Gas Emissions: Renewable energy sources like wind, solar, hydro,
and geothermal produce little to no greenhouse gas emissions during electricity
generation. This contrasts sharply with fossil fuels, which emit significant amounts of
carbon dioxide and other pollutants when burned.
2. Improved Air and Water Quality: By replacing fossil fuels with renewable energy
sources, we can reduce air pollutants such as sulfur dioxide, nitrogen oxides, and
particulate matter. This leads to cleaner air and improved respiratory health for
communities near power plants.
3. Mitigation of Climate Change: Generating energy from renewable sources helps
mitigate climate change by reducing the dependence on fossil fuels, which are the

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primary drivers of global warming due to their carbon emissions.
4. Job Creation and Economic Benefits: The renewable energy sector has been a significant
source of job creation, offering opportunities in manufacturing, installation,
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maintenance, and research. This growth contributes to economic stability and resilience.
5. Enhanced Energy Security and Independence: Diversifying our energy sources with
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renewables reduces dependence on imported fossil fuels, enhancing energy security and
decreasing vulnerability to geopolitical disruptions.
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6. Promotion of Sustainable Development: Embracing renewable energy aligns with

sustainable development goals by fostering a cleaner and more sustainable energy
system for future generations.
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7. Conservation of Natural Resources: Renewable energy sources harness naturally

replenishing resources such as sunlight, wind, water, and geothermal heat, which are
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less likely to be depleted over time compared to finite fossil fuel reserves.

Challenges of Renewable Energy (Disadvantages of Renewable Energy):

1. Intermittency: Renewable sources like solar and wind are intermittent, depending on
weather conditions, which makes consistent energy generation a challenge.
2. Storage: Efficient energy storage solutions are needed to store excess energy generated
during peak times for use during periods of low generation.
3. Grid Integration: Integrating renewable energy into existing grids requires infrastructure
upgrades and smart grid technologies to handle variability and maintain stability.
4. Cost: Initial setup costs for renewable energy infrastructure can be high, although they
typically have lower operational costs once installed.
5. Public Perception and Policy: Public acceptance and supportive policies are crucial for
widespread adoption of renewable energy technologies.
6. Geographical Limitations: Some renewable sources are location-dependent (e.g.,
hydroelectricity, geothermal), limiting their universal applicability.
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 7. Land & Environmental Impact: Large-scale solar farms and wind turbines require
significant land use and Hydropower can disrupt ecosystems and affect local
communities.
8. Efficiency & Technological Limitations: Solar panel and wind turbine efficiency
improvements are still needed. Research is ongoing to develop next-generation energy
solutions.
9. Economic Competition with Fossil Fuels: Fossil fuels still benefit from existing
infrastructure and subsidies. Price fluctuations in fossil fuels impact the competitiveness
of renewables.

Solar Energy:
Solar radiation refers to the energy emitted by the Sun in the form of electromagnetic waves,
which included visible light, infrared, and ultraviolet radiation. The spectrum of solar radiation is
close to that of a black body with a temperature of about 5800 K. The solar spectrum is
described by their electromagnetic spectrum within the wavelength range of 0.20µm to 4.0µm.

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Solar Constant (𝑰𝒔𝒄 ): The rate at which solar energy arrives at the top of the atmosphere is
called solar constant. It is defined as “the amount of energy received in unit time on a unit area
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perpendicular to the sun’s direction at the mean distance of the earth from the sun”. It is most
accurately measured from satellites where atmospheric effects are absent. The value of the
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constant is said to be approximately 1.366 kW/m2. The solar constant includes radiation over
the entire electromagnetic spectrum. The Solar constant is fairly constant, increasing by only
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0.2 percent at the peak of each 11-year solar cycle.

Extraterrestrial radiation
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Extraterrestrial radiation refers to the total solar radiation received at the outer edge of Earth's
atmosphere before it is scattered, absorbed, or reflected by the atmosphere. It is measured at
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approximately 1,366 W/m², known as the solar constant, though this value slightly fluctuates
due to variations in solar activity. Unlike solar radiation at the Earth's surface, extraterrestrial
radiation is unaffected by atmospheric factors such as clouds, dust, and air molecules. It serves
as a baseline for calculating the amount of solar energy that ultimately reaches the ground,
which is critical for solar energy applications, climate modelling, and understanding the Earth's
energy balance.
As the distance between the earth and the sun varies a little through the year, the
extraterrestrial flux also varies. The sun is closest to the sun in the summer and farthest away in
the winter. The variation in distance produces a nearly sinusoidal variation in the intensity of
solar radiation that reaches the earth. This can be approximated by the equation
360𝑛
𝐼𝑛 = 𝐼𝑠𝑐 (1 + 0.033𝑐𝑜𝑠 ) (1)
365
where ′𝑛′ is the day of the year counted from the first fay of January

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Understanding extraterrestrial radiation is essential in fields like climate science, astronomy,
and solar energy research, as it serves as a baseline for calculating the amount of solar energy
reaching Earth's surface.

Spectral distribution of extraterrestrial radiation

The spectral distribution of extraterrestrial radiation refers to the range of electromagnetic
wavelengths emitted by the Sun and received outside Earth's atmosphere. It also describes how
the intensity of radiation is spread across different wavelengths within the electromagnetic
spectrum. Spectral distribution is often represented as a graph showing intensity versus
wavelength, helping to visualize how energy is distributed across the spectrum.

A typical spectral distribution of extraterrestrial radiation is shown in Figure 1. The curve rises
sharply with the wavelength and reaches the maximum value of 2074W/m2/μm at a
wavelength of 0.48 mm. It then decreases asymptotically to zero, showing that 99% of the sun’s
radiation is obtained up to a wavelength of 4 μm.

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Figure 1: Spectral distribution of extraterrestrial radiation

The percentage of radiation reaching the top of the earth’s atmosphere consists of the following
wave length represented in the following table

Wave length 0 – 0.38 0.38 – 0.78 0.78 – 4.0

(µm) (UV Rays) (Visible Rays) (Infrared Rays)
Approximate
95 640 618
energy (W/m2)
Approximate %age
9% 47.3% 45.7%
of Total energy
This concept is important in fields like astronomy, climate science, and optical engineering, as it
influences how materials absorb, reflect, or transmit light and affects processes like
photosynthesis, solar power generation, and remote sensing.

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Terrestrial radiation: Beam and diffuse radiations:
The solar radiation that penetrates the earth’s atmosphere and reaches the surface differs in
both amount and character from the radiation at the top of the atmosphere. In the first place,
part of the radiation is reflected back into the space, especially by clouds. Furthermore, the
radiation entering the atmosphere is partly absorbed by molecules in the air. Oxygen and ozone
formed by oxygen, absorb nearly all the ultraviolet radiations and water vapour and carbon
dioxide absorb some of the energy in infrared range. In addition, part of the solar radiation is
scattered by droplets in clouds by atmospheric molecules and by dust particles.

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Figure 2: Direct, diffuse and total radiation
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“Solar radiation that has not been absorbed or scattered and reaches the ground directly from
the sun is called direct or beam radiations”. It is the radiation which produces a shadow when
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interrupted by an opaque object. “Diffuse radiations are that solar radiation received from the
sun after its direction has been changed by reflection and scattering by the atmosphere”.
Because of the solar radiation is scattered in all directions in the atmosphere, diffuse radiation
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comes to the earth from all parts of the sky. The total radiation received at any point on earth’s
surface is the sum of the direct and diffuse radiation.
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