MODULE 1:
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: Extraterrestrial radiation, spectral distribution of extraterrestrial radiation, solar
constant, solar radiation at the earth’s surface, beam, diffuse and global radiation.
INTRODUCTION TO RENEWABLE ENERGY:
Overview of Global Energy Demand
• Definition: Global energy demand refers to the total energy required to support economic
activities, industrial operations, transportation, residential needs, and technological
development worldwide.
• Importance: Energy is the backbone of modern civilization, influencing economic growth,
technological advancements, and overall development.
• Growth Drivers: Population growth, urbanization, industrialization, and technological
progress are primary drivers of rising energy demand.
1. Factors Affecting Global Energy Demand
• Population Growth: More people result in higher energy consumption.
• Economic Development: Industrial activities in developing nations; Strong correlation
between GDP growth and energy consumption increases energy demand.
• Technological Advancements: While some technologies improve energy efficiency, others
(like digital infrastructures) increase demand; Automation, digitalization, and new
industries (like data centres) drive demand; Innovations in energy conversion (like more
efficient turbines, batteries, and smart grids) influence demand patterns.
• Climate and Geography: Energy needs vary by region due to heating/cooling demands.
• Energy Prices: Higher energy costs can reduce demand by encouraging efficiency and
alternative energy sources.
• Government Policies: Regulations, subsidies, and international agreements (like the Paris
Accord) significantly impact energy consumption trends.
2. Energy Consumption Patterns
• Regional Variations:
Developed Countries: Higher per capita energy consumption focus on energy efficiency
and renewable sources.
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Developing Countries: Rapidly increasing demand due to industrial growth relies on fossil
fuels.
• Sector-Wise Energy Consumption:
Industrial: Heavy energy use for manufacturing, chemical processing, and materials
production.
• Transportation: Predominantly depends on petroleum fuels, though electric vehicles are on
the rise.
• Residential & Commercial: Growing demand due to electrification, appliances, and
urbanization.
• Agriculture: Energy for irrigation, mechanization, and processing.
3. Primary Energy Sources
• Fossil Fuels: Oil, coal, and natural gas dominate global energy supply but contribute to
environmental issues.
• Renewable Energy: Solar, wind, hydropower, geothermal, and biomass are growing
rapidly to meet sustainable goals; Environmentally friendly, sustainable, and increasingly
cost-effective.
• Nuclear Energy: Provides a significant share in some countries, offering low-carbon energy
but faces challenges like safety concerns and waste disposal.
4. Global Energy Demand Trends
• Shift Toward Cleaner Energy: Global efforts to reduce carbon emissions are accelerating
the transition to renewables and to combat climate change.
• Electrification: Expanding electricity use in transportation (EVs), heating, and industrial
applications.
• Energy Efficiency Improvements: Increasing focus on energy efficiency in appliances,
vehicles, and industrial processes; Technological advancements in energy conversion
systems reduce wastage, lowering overall demand growth.
• Increasing Global Demand: Driven by population growth, industrialization, and
urbanization, particularly in developing countries, Growing importance of energy storage
and smart grids to manage supply and demand effectively.
• Decarbonization: Policies focusing on reducing carbon emissions (e.g., net-zero targets
by 2050).
• Technological Innovations: Advances in energy storage, smart grids, and efficient energy
systems.
5. Challenges in Meeting Energy Demand
• Resource Depletion: Limited reserves of fossil fuels and the need for sustainable resource
management.
• Environmental Concerns: Greenhouse gas emissions from fossil fuels contribute to climate
change, necessitating a shift toward low-carbon energy.
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• Energy Security: Political and economic instability in key energy-producing regions affect
the reliability of energy supplies globally.
• Infrastructure: Need for investment in modern, resilient energy infrastructure.
• Energy Equity: Disparities in energy access between developed and developing regions
highlight the need for inclusive energy policies.
• Geopolitical Risks: Energy supply chains are vulnerable to political instability, conflicts,
and trade disputes.
6. Outlook for Global Energy Demand
• Growing Role of Renewables: Rapid growth in renewable energy adoption worldwide;
Solar and wind expected to dominate new energy installations.
• Electrification: Shift towards electric vehicles (EVs), smart homes, and digital
infrastructure.
• Hydrogen Economy: Emerging as a clean energy carrier, especially for heavy industries.
• Energy Storage Solutions: Development of large-scale batteries to support renewable
integration.
• Decarbonization: Growing investment in carbon capture, utilization, and storage (CCUS)
to reduce emissions.
• Integration of Renewables: Advances in solar PV, wind turbines, and battery storage to
manage intermittent energy sources.
• Smart Grids and Digitalization: Use of AI, IoT, and advanced analytics for efficient energy
distribution and demand management.
• Emerging Technologies: Hydrogen economy, advanced nuclear reactors, and bioenergy
innovations are shaping future energy landscapes.
Need for Renewable Energy:
The importance of renewable energy is due to increasing energy demand, environmental concerns,
and resource depletion. The need for the shift towards renewable energy are as follows:
1. Depletion of Fossil Fuels
• Fossil fuels (coal, oil, and natural gas) are finite and are being consumed at a rapid rate.
• The world's energy demand is rising, leading to faster depletion of non-renewable
resources.
• Renewable energy sources (solar, wind, hydro, biomass) provide a sustainable alternative
to meet long-term energy needs.
2. Environmental Pollution & Climate Change
• Fossil fuel combustion releases CO₂, SO₂, NOₓ, leading to global warming, acid rain, and
air pollution.
• Non-renewable energy sources are the main contributors to climate change and
environmental degradation.
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• Renewable energy produces low or zero emissions, making it an environmentally friendly
choice.
3. Energy Security & Self-Sufficiency
• Many countries import oil, coal, and gas, making them dependent on foreign energy
sources.
• Renewable energy ensures energy independence by utilizing local resources such as
sunlight, wind, and water.
• Reducing dependency on fossil fuels enhances national energy security.
4. Rising Energy Demand
• Global population and industrialization are increasing energy consumption.
• Fossil fuel reserves are limited and cannot meet long-term demands.
• Renewable energy provides a continuous and sustainable energy supply.
5. Economic Benefits & Job Creation
• Renewable energy industry creates employment opportunities in manufacturing,
installation, and maintenance.
• Investment in renewables reduces the economic burden of fuel imports.
• The falling cost of solar panels, wind turbines, and batteries makes renewables more cost-
effective in the long run.
6. Decentralized Power Generation
• Renewable energy allows for distributed generation (e.g., rooftop solar, micro-hydro, and
wind farms).
• Ideal for rural electrification where grid access is limited.
• Reduces transmission and distribution losses.
7. Government Policies & Global Initiatives
• Governments worldwide are promoting renewable energy policies, subsidies, and
incentives.
• Global agreements like the Paris Agreement aim to reduce carbon footprints and promote
sustainability.
• Incentives such as feed-in tariffs, tax benefits, and green energy certificates make
renewable energy more attractive.
8. Advancement in Energy Storage & Smart Grids
• Earlier, renewables were criticized for intermittency (solar at night, no wind on calm days).
• Advancements in battery storage (Li-ion, pumped hydro, hydrogen fuel cells) make
renewables more reliable.
• Smart grids help in efficient energy management and integration of renewables into the
power system.
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Environmental Benefits of Renewable Energy:
1. Reduction in Greenhouse Gas Emissions
• Renewable energy sources like solar, wind, hydro, and geothermal do not release carbon
dioxide (CO₂) or other greenhouse gases.
• Unlike fossil fuels, which contribute to global warming and climate change, renewables
offer a clean and sustainable alternative.
• The adoption of renewables helps in mitigating the effects of climate change.
2. Air and Water Pollution Reduction
• Fossil fuel combustion releases pollutants such as SO₂, NOₓ, and particulate matter, leading
to acid rain and respiratory diseases.
• Renewable energy sources produce little to no air pollution, improving air quality.
• Unlike coal-based thermal power plants, solar and wind energy do not require water for
cooling, reducing water consumption and contamination.
3. Conservation of Natural Resources
• Coal, oil, and natural gas are finite resources that take millions of years to form.
• Renewable energy sources do not deplete natural reserves and ensure long-term energy
sustainability.
• Hydropower and biomass energy use natural cycles to generate power, reducing
dependency on non-renewable resources.
4. Reduction in Land Degradation and Deforestation
• Coal mining and oil drilling cause deforestation, soil erosion, and habitat destruction.
• Renewable energy projects, especially rooftop solar and offshore wind farms, require less
land compared to coal mines or oil refineries.
• Bioenergy, if sourced sustainably, can utilize agricultural waste instead of cutting down
forests.
5. Waste Reduction
• Nuclear energy produces hazardous radioactive waste, while coal power generates ash and
heavy metals.
• Renewable energy systems, especially solar and wind, generate minimal waste over their
lifetime.
6. Promotion of Sustainable Development
• Renewable energy fosters environmental sustainability while supporting economic and
social growth.
• It provides clean energy access to rural and remote areas, improving quality of life.
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Environmental Challenges of Renewable Energy:
1. Land Use & Habitat Disruption
• Large-scale renewable energy projects (hydropower dams, wind farms, solar farms) require
significant land, which can disrupt ecosystems and biodiversity.
• Hydropower plants can cause river flow alterations, affecting aquatic life.
• Wind turbines may impact bird and bat populations if not properly located.
2. Resource Consumption & Manufacturing Impact
• Manufacturing solar panels, wind turbines, and batteries requires rare earth metals (lithium,
cobalt, silicon), leading to mining-related pollution.
• The energy-intensive manufacturing process results in CO₂ emissions if powered by fossil
fuels.
• Disposal of solar panels and batteries create electronic waste if not recycled properly.
3. Energy Storage & Waste Management
• Since solar and wind energy are intermittent, energy storage solutions (batteries, pumped
hydro) are required.
• Battery storage systems have environmental concerns due to the mining and disposal of
lithium, cobalt, and lead.
• Developing sustainable battery recycling and alternatives like hydrogen storage is crucial.
4. Hydropower’s Environmental Impact
• Large hydropower dams can lead to:
o Displacement of communities and destruction of natural habitats.
o Alteration of river ecosystems, affecting fish migration and biodiversity.
o Methane emissions from decomposing organic material in reservoirs.
5. Noise & Aesthetic Concerns (Wind & Solar Energy)
• Wind turbines generate noise, which can be problematic in residential areas.
• Solar and wind farms are visually unappealing, affecting tourism and land value.
6. High Initial Cost & Infrastructure Challenges
• Setting up renewable energy infrastructure requires a high initial investment in technology
and grid integration.
• Developing countries may struggle with financing solar and wind energy projects.
• Renewable energy transmission requires smart grids, which need additional investment.
Renewable energy is crucial for a cleaner and sustainable future, but its environmental challenges
must be addressed through better policies, technological advancements, and sustainable resource
management. Innovations in energy storage, recycling of materials, and improved land use
planning can minimize the negative impacts of renewable energy.
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Comparison of Renewable and Non-renewable energy sources:
• Renewable energy is environmentally friendly, abundant, and sustainable but faces challenges
like high initial costs, lower efficiency, and intermittent availability.
• Non-renewable energy is highly efficient, cost-effective (short term), and widely used but
contributes to pollution, resource depletion, and climate change.
• The future of energy lies in transitioning towards renewables with better energy storage and
grid integration to ensure energy security.
Sl.
Criteria Renewable Energy sources Non-renewable Energy sources
No.
Energy sources that are Energy sources that exist in finite
replenished naturally within a amounts and take millions of
1 Definition
short time (e.g., solar, wind, years to form (e.g., coal, oil,
hydro, biomass, geothermal). natural gas, nuclear energy).
2 Availability Abundant and inexhaustible Limited and depleting
Unsustainable due to finite
3 Sustainability Sustainable for long-term use
reserves
Generally lower (e.g., solar PV High efficiency (e.g., thermal
4 Efficiency
~15-20%) power plants ~35-45%)
Intermittent (depends on sun,
5 Dependability Continuous supply possible
wind, etc.)
Carbon
6 Low or zero emissions High emissions (CO₂, SO₂, NOₓ)
Emissions
Causes air, water, and soil
7 Pollution Minimal impact
pollution
Major contributor to climate
8 Climate Change Helps reduce global warming
change
High (installation of solar Lower (existing infrastructure is
9 Initial Cost
panels, wind turbines, etc.) well-established)
High (fuel extraction,
10 Operating Cost Low (sun and wind are free)
transportation, and refining)
High (coal and oil plants require
Moderate (wind, solar require
11 Maintenance maintenance and fuel
regular upkeep)
procurement)
Used for electricity generation
Power Used in thermal power plants,
12 (solar farms, wind power,
Generation nuclear reactors
hydroelectricity)
Limited (except biomass and Major source for industries (steel,
13 Industrial Use
hydro) cement, chemicals, etc.)
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Primary fuel for transport (petrol,
14 Transportation Limited (biofuels, EVs)
diesel, jet fuel)
Storage Needs energy storage systems No storage needed, as fuel can be
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Requirements (batteries, pumped hydro) burned as required
Requires smart grids for Easily integrated into the power
16 Grid Integration
stability grid
Solar Energy, Wind Energy,
Coal, Oil, Natural Gas, Nuclear
17 Examples Hydropower, Biomass,
Power, Diesel, Petrol
Geothermal Energy
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SOLAR RADIATION:
Extra terrestrial radiation:( Solar Radiation Outside the Earth’s Atmospheres)
• The intensity of solar radiation keeps on attenuating as it propagates away from the surface
of the sun, though the wavelengths remain unchanged.
• Solar radiation incident on the outer atmosphere of the earth is known as Extraterrestrial
Radiation, Iext.
• The extraterrestrial radiation deviates from solar constant value due to two reasons.
• The first is the variation in the radiation emitted by the sun itself. The variation due to this
reason is less than ±1.5 per cent with different periodicities.
• The second is the variation of earth–sun distance arising from earth’s slightly elliptic path.
The variation due to this reason is ±3 per cent and is given by:
where, n is the day of the year starting from January 1.
• The extraterrestrial radiation, being outside the atmosphere, is not affected by changes in
atmospheric conditions.
• While passing through the atmosphere it is subjected to atmospheric absorption and
scattering depending on atmospheric conditions, depleting its intensity.
• A fraction of scattered radiation is reflected to space while remaining is directed
downwards.
• Solar radiation that reaches earth surface after passing through the earth’s atmosphere is
known as Terrestrial Radiation.
• The terrestrial radiation expressed as energy per unit time per unit area (i.e. W/m2) is
known as Solar Irradiation.
• The term Solar Insolation (incident solar radiation) is defined as solar radiation energy
received on a given surface area in a given time (in J/m2 or kWh/m2).
• The positions of extraterrestrial and terrestrial regions are indicated in Fig. 1.
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Fig. 1: Propagation of solar radiation through atmosphere
Solar Constant:
• It is a measure of flux density and is the amount of incoming solar electromagnetic
radiation per unit area that would be incident on a plane perpendicular to the rays at a
distance of one AU.
• It includes all types of solar radiation, not just the visible light.
• Solar Constant, Isc is defined as the energy received from the sun per unit time, on a unit
area of surface perpendicular to the direction of propagation of the radiation, at the earth’s
mean distance from the sun.
• The solar energy reaching the periphery of the earth’s atmosphere is constant for all
practical purposes and is known as the solar constant.
• The exact value of solar constant is not known with certainty but is believed to be between
1,353 and 1,395 W/m2.
• The solar constant value is estimated based on the solar radiation received on a unit area
exposed perpendicularly to the rays of the sun at an average distance between the sun and
the earth.
• Its average value is approx. 1,366 W/m².
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Spectral Distribution of Extraterrestrial Radiation:
• Variations of solar irradiance with wavelength of solar radiation is called solar radiation
spectrum as given in Fig. 2.
• This spectrum of electromagnetic radiation striking the earth’s atmosphere spans a range
of 0.1 µm to about 3 µm. This can be divided into five regions in increasing order of
wavelengths as given below:
1. Ultraviolet C or (UVC) range:
• It spans a range of 0.1 µm to 0.28 µm.
• The term ultraviolet refers to the fact that the radiation is at higher frequency than violet
light (and hence also invisible to the human eye).
• Owing to absorption by the atmosphere, only mere amount reaches the earth’s surface
(lithosphere).
2. Ultraviolet B or (UVB) range:
• It spans 0.28 µm to 0.315 µm.
• It is also greatly absorbed by the atmosphere.
• Along with UVC, UVB is responsible for the photochemical reaction leading to the
production of the ozone layers.
3. Ultraviolet A or (UVA) range:
• It spans 0.315 µm to 0.4 µm.
• It is less damaging to the DNA and hence used in tanning and PUVA (Photo-chemo UVA)
therapy for psoriasis.
4. Visible range or light:
• It spans 0.38 µm to 0.78 µm.
• It is this range that is visible to the naked eye.
5. Infrared range:
• It spans 0.7 µm to 100 µm.
• It is responsible for an important part of the electromagnetic radiation that reaches the earth.
• It is also divided into three types based on wavelength:
(a) Infrared-A: 0.7 µm to 1.4 µm
(b) Infrared-B: 1.4 µm to 3.0 µm
(c) Infrared-C: 3.0 µm to 100 µm
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Fig. 2: Solar radiation spectrum
• Biologically important effects of sunlight are necessarily due to wavelengths in the range
0.28–100 µm and divided into four wavelength regions: ultraviolet B (UVB, 0.28 µm to
0.78 µm), ultraviolet A (UVA, 0.315 µm to 0.4 µm), visible light (0.38 µm to 0.78 µm),
and infrared (0.7 µm to 100 µm).
• Ultraviolet wavelengths shorter than 0.28 µm are heavily absorbed by molecular oxygen,
ozone, and water vapour in the upper atmosphere and do not reach the surface of the earth
in measurable amounts.
• Except in special circumstances, such as photo drug reactions and certain disease states,
visible light does not appear to be harmful to normal individuals.
• Infrared is essentially heat, and although non-solar sources can cause skin tumours and
cataracts, it is uncertain at present if the infrared in sunlight contributes significantly to the
problem of skin cancer.
• The major source of damaging effect of sunlight comes primarily from the UV portion of
the spectrum between 0.29 µm and 0.4 µm (UVB and UVA). The different ultraviolet
wavelengths penetrate the skin to different depths and have different biological
consequences.
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Solar radiation at the earth’s surface (Solar Insolation):
• The rate at which solar energy reaches a unit area at the earth is called the solar irradiance
or insolation.
• In other words, solar insolation means the sun’s energy received over a horizontal surface.
• The units of measure for irradiance are watts per square metre (W/m2).
• Total insolation on a horizontal surface on a clear day even for two different locations are
not same.
• A normal (perpendicular) surface to the sun’s rays does increase energy received over a
horizontal surface.
• Solar radiation before reaching the earth’s surface is subjected to the mechanism of
absorption and scattering while passing through several gases (e.g., water vapour, ozone,
carbon dioxide, oxygen, etc.), maximum radiation reaches the earth’s surface during clear
sky (no clouds).
• Thus, on the surface of earth we have two components of solar radiation:
(i) direct or beam radiation, unchanged in direction and
(ii) diffuse radiation, the direction of which is changed by scattering and reflection.
• Total radiation at any location on the surface of earth is the sum of beam radiation and
diffuse radiation, what is known as global radiation
Beam, Diffuse and Global Radiation:
In view of the absorption and scattering, solar radiation reaching the earth’s surface is defined by
the following terms:
1. Beam radiation (direct solar radiation):
• Solar radiation that has not been absorbed or scattered and reaches the ground directly from
the sun is called Beam or Direct radiation.
• It is the solar radiation received on the earth’s surface without change of direction (without
any attenuation) in line with sun.
• It is the radiation which produces a shadow when interrupted by an opaque object.
2. Diffuse radiation:
• Solar radiation is subjected to attenuation and reaches the earth’s surface from all parts of
the sky hemisphere.
• Solar radiation received from the sun after its direction has been changed by reflection and
scattering by the atmosphere is called Diffuse radiation.
• Solar radiation scattered by aerosols, dust and molecules is known as diffuse radiation. It
does not have a unique direction.
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• Even on clear days, there will be some diffuse radiation depending upon the amount of dust
particles, ozone and water vapour present in the atmosphere.
• On overcast days when the sun is not visible, all the radiation reaching the ground will be
diffuse radiation.
• Since solar radiation is scattered in all directions in the atmosphere, diffuse radiation comes
to the earth from all parts of the sky.
• In general, the intensity of diffuse radiation coming from various directions in the sky is
not uniform. The diffuse radiation is therefore said to be anisotropic in nature.
3. Global radiation:
• The sum of beam radiation and diffuse radiation received at any point on the earth’s surface
is known as Global radiation or the Total Solar radiation.
• Insolation is defined as the total solar radiation energy received on a horizontal surface of
unit area on the ground in unit time.
Fig. 3: Beam, Diffuse and Global Radiation
The radiation data of global and diffuse radiation versus solar time on a horizontal surface for a
clear day and partially cloudy day are shown in Fig. 4.
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Fig. 4: Daily variation of global and diffuse radiation on a
(a) clear and (b) cloudy days on horizontal surface
Air mass:
• Air mass is a term used as a measure of the distance travelled by beam radiation through
the earth’s atmosphere before it reaches a location at the earth’s surface.
• It is defined as the ratio of the mass of atmosphere through which the beam radiation passes
to the mass of the atmosphere through which it will pass if the sun is directly overhead
(i.e., at its Zenith).
Fig. 5: Tilted Surface
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2. Calculate the sunset hour angle and day length at a location latitude of 35° N on February 14.
Solution:
For February 14, n = 31+14 = 45
Latitude, ϕ = 35°
Declination,
= - 13.62 degrees.
Sunset hour angle,
= cos-1[ - tan (-13.62o) tan(35o)]
= 80.33o
Day length,
= (2/15) * 80.33
= 10.71 hours
3. Calculate hour angle when it is 3 h after solar noon.
Solution:
Given, Solar time = 12:00 + 3 = 15:00 hr
Hour angle at any moment,
= [12:00 – 15:00] (in hours) × 15 degrees = – 45 degrees
4. Calculate hour angle when it is 2 h 20 min before solar noon.
Solution:
Given, Solar time = 12:00 – 2:20 = 9:40 hr
Hour angle at any moment,
= [12:00 – 9:40] (in hours) × 15 degrees
= 2 h 20 min *15 = 30h 300 min = 30 + 300/60 = 35 degrees
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