14.1 Renewable & Non-Renewable Energy Resources and India's Energy Transition

Renewable & Non-Renewable Energy Resources and India's Energy Transition

Core Principle: Energy resources form the thermodynamic foundation of industrial civilization and economic development. Transitioning from depletable, carbon-heavy fossil fuels to sustainable, low-carbon renewable flows is the defining technological and environmental challenge of the twenty-first century, anchored in India by ambitious policy targets and indigenous nuclear and renewable missions.

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1. Taxonomy of Energy Resources

In environmental science and energy economics, energy resources are classified along two fundamental conceptual axes: renewability (rate of natural replenishment relative to extraction rate) and tradition of usage (conventional versus non-conventional).

                           ┌─── Non-Renewable (Finite Geological Stocks)
                           │    ├── Coal (Anthracite, Bituminous, Lignite, Peat)
       ┌─── Conventional ──┤    ├── Petroleum (Crude oil, Diesel, Gasoline)
       │    (Traditional)  │    └── Natural Gas (Methane, CNG, LNG, PNG)
       │                   └─── Large Hydroelectric (> 25 MW, historic classification)
Energy ┤
       │                   ┌─── Solar (Photovoltaic & Concentrated Solar Power)
       │                   ├─── Wind (Onshore & Offshore)
       └─── Non-Conventional ── Small Hydro Power (SHP <= 25 MW)
            (Renewable)    ├─── Biomass & Biofuels (1G, 2G, 3G, 4G)
                           ├─── Geothermal (Hydrothermal & Hot Dry Rock)
                           └─── Ocean Energy (Tidal, Wave, OTEC)

1.1 Conventional Non-Renewable Energy Resources

Conventional energy resources refer to traditional, highly centralized sources that have powered industrial societies since the Industrial Revolution. Because their geological formation requires hundreds of millions of years of subterranean heat and pressure acting upon decayed organic matter, their extraction depletes finite terrestrial stocks:

• Coal: The most abundant fossil fuel, formed from ancient peat swamps in the Carboniferous and Permian eras. Coal is categorized by carbon content, volatile matter, moisture, and calorific value:
  • Anthracite: Highest metamorphic grade; 85% to 95% carbon content; hard, lustrous, burns with an almost smokeless blue flame; highest calorific value (~30–33 MJ/kg). Found in limited quantities in Jammu and Kashmir.
  • Bituminous: 60% to 80% carbon content; medium calorific value; dominant coal type in India, primarily located in Gondwana rock formations (Jharkhand, Odisha, Chhattisgarh, West Bengal). Subdivided into coking coal (metallurgical steel smelting) and non-coking coal (thermal power generation).
  • Lignite: 40% to 55% carbon content; brown, soft coal with high moisture (~35–50%) and high sulfur content; lower calorific value (~15–20 MJ/kg). Prominent deposits occur at Neyveli in Tamil Nadu, Rajasthan, and Gujarat.
  • Peat: First geological stage of coal formation; <40% carbon content; spongy, highly fibrous, high moisture content, burns with dense smoke and low heat output. Not commercially viable for power generation.
• Petroleum (Crude Oil): Complex liquid mixture of hydrocarbons formed from ancient marine zooplankton and phytoplankton buried under sedimentary layers. Refined via fractional distillation into liquefied petroleum gas (LPG), petrol (gasoline), naphtha, kerosene, diesel, and bitumen. Major Indian domestic reserves are located at Mumbai High (offshore), Digboi and Naharkatiya (Assam), and the Barmer Basin (Rajasthan).
• Natural Gas: Cleanest-burning fossil fuel, composed primarily of methane ($CH_4$, 70–90%), along with ethane, propane, and butane. Produces approximately 50% less carbon dioxide per unit of energy generated compared to coal, and minimal particulate matter:
  • Compressed Natural Gas (CNG): Methane compressed to 200–250 bar, utilized as a clean transportation fuel.
  • Liquefied Natural Gas (LNG): Natural gas chilled to approximately -162°C at atmospheric pressure, condensing into a liquid that occupies 1/600th of its gaseous volume, enabling global cryogenic maritime transport.
  • Piped Natural Gas (PNG): Low-pressure distribution of methane directly to domestic households and commercial buildings via utility pipelines.

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2. Renewable Energy Technologies: Principles, Physics & Deployments

Renewable energy encompasses inexhaustible or rapidly replenishing natural processes driven directly or indirectly by solar radiation, planetary gravitational dynamics, and radioactive crustal decay.

2.1 Solar Energy

The sun radiates electromagnetic energy generated by nuclear fusion ($4\text{ }^1H \to \text{ }^4He + 2e^+ + 2\nu + \text{energy}$) in its stellar core. At the top of the Earth's atmosphere, the mean incoming solar flux is measured as the Solar Constant (approximately $1361\text{ to }1367\text{ W/m}^2$). At ground level, solar radiation is characterized by two metrics:

• Irradiance: Instantaneous power density received per unit surface area, measured in watts per square meter ($\text{W/m}^2$).
• Insolation: Cumulative incident solar radiation energy delivered over a designated time period, measured in kilowatt-hours per square meter per day ($\text{kWh/m}^2/\text{day}$). India receives an average insolation of 4 to 7 $\text{kWh/m}^2/\text{day}$ with 250 to 300 clear sunny days annually.

Solar energy conversion proceeds along two technological pathways:

                          ┌── Photovoltaic (PV) ──> Direct conversion of light to
                          │                         electricity via semiconductor bandgaps
Solar Radiation Pathways ─┤
                          └── Concentrated Solar ─> Thermal reflection via mirrors/heliostats
                              Power (CSP)           heating working fluid to drive steam turbines

1. Solar Photovoltaics (PV):
   • Physics of Conversion: Operates on the photoelectric effect within semiconductor materials (primarily silicon). A standard silicon solar cell comprises a p-n junction. When incident photons possess energy exceeding the semiconductor's bandgap ($E_g \approx 1.1\text{ eV}$ for crystalline silicon), they elevate valence electrons to the conduction band, generating electron-hole pairs. The built-in electric field at the p-n junction separates these charge carriers, establishing a direct current (DC) voltage across external contacts.
   • Cell Typologies: Monocrystalline silicon (highest laboratory efficiency: 20–24%, higher manufacturing cost), Polycrystalline silicon (15–18% efficiency, lower cost), and Thin-Film technologies (Amorphous Silicon, CdTe, CIGS: flexible, lower efficiency 10–13%).
2. Concentrated Solar Power (CSP):
   • Uses optical tracking mirrors (heliostats, parabolic troughs, or parabolic dishes) to concentrate direct beam solar irradiance onto a central receiver.
   • The concentrated heat elevates a working fluid (synthetic oil, molten nitrate salts) to temperatures between 400°C and 1000°C. The molten salt transfers heat to water in a heat exchanger, generating superheated steam that drives a conventional Rankine-cycle steam turbine.
   • Major Advantage: Thermal Energy Storage (TES) using molten salt tanks allows CSP plants to dispatch electricity continuously during night hours and peak grid demand periods.

National Solar Policies in India

• Jawaharlal Nehru National Solar Mission (JNNSM): Launched in January 2010 as one of the eight core missions under the National Action Plan on Climate Change (NAPCC). Originally targeting 20 GW of grid-connected solar power by 2022, the target was aggressively scaled up in 2015 to 100 GW (divided into 60 GW utility-scale solar parks and 40 GW rooftop solar).
• Key Solar Initiatives: Ultra Mega Renewable Energy Power Parks (UMREPPs) such as the Bhadla Solar Park in Rajasthan (~2,245 MW) and Pavagada Solar Park in Karnataka (~2,050 MW); PM-KUSUM (Pradhan Mantri Kisan Urja Suraksha evam Utthaan Mahabhiyan) for solarizing agricultural irrigation pumps; and PM Surya Ghar Muft Bijli Yojana targeting 10 million rooftop solar installations.

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2.2 Wind Energy

Wind is an indirect form of solar energy, generated by differential solar heating of the Earth's atmosphere, thermal land-sea contrasts, and planetary rotation mediated by the Coriolis force.

Aerodynamic Physics & The Betz Limit

The theoretical kinetic power ($P$) available in an airstream moving with velocity $v$ through a turbine rotor swept area $A$ is formulated as:

$P = \frac{1}{2} \rho A v^3$

Where:

• $\rho$ (rho) is air density (approximately $1.225\text{ kg/m}^3$ at sea level and 15°C).
• $A$ is the rotor swept area ($A = \pi r^2$, where $r$ is blade length).
• $v$ is wind velocity.

Critical Mathematical Insight for the Exam: Wind power exhibits a cubic relationship with wind speed ($P \propto v^3$). If wind velocity doubles (e.g., from 5 m/s to 10 m/s), the power delivered to the rotor increases by a factor of eight ($2^3 = 8$). A modest increase in sustained wind speed produces an exponential gain in electrical output.

• The Betz Limit (Albert Betz, 1919): An aerodynamic conservation law demonstrating that no wind turbine can extract 100% of the kinetic energy in wind without completely stopping the airflow behind the blades (which would halt airflow through the rotor). The maximum theoretical aerodynamic efficiency factor is:

$C_{p,\text{max}} = \frac{16}{27} \approx 59.26\%$

In real-world commercial turbines, mechanical friction, blade wake rotation, and generator losses limit actual conversion efficiency to approximately 35% to 45%.

• Turbine Operational Parameters:
  • Cut-in Speed: Minimum wind velocity required to initiate rotation and power generation (~3 to 4 m/s).
  • Rated Speed: Velocity at which the turbine reaches its maximum design electrical capacity (~12 to 15 m/s).
  • Cut-out Speed: Critical maximum wind velocity at which mechanical brakes or aerodynamic blade pitch systems feather the rotor to prevent structural destruction (~20 to 25 m/s).
• Onshore vs. Offshore Wind: Onshore wind is technologically mature with lower capital expenditure, but constrained by land acquisition and surface roughness. Offshore wind harnesses stronger, smoother, and more persistent oceanic winds without topographical drag, yielding higher capacity factors (~45–55% vs. ~25–35% onshore). India possesses an estimated 70 GW of offshore wind potential along the coastlines of Gujarat and Tamil Nadu.
• Leading Indian States in Wind Capacity: Gujarat, Tamil Nadu, Karnataka, and Rajasthan.

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2.3 Hydro Power

Hydroelectric energy converts the potential energy of elevated water bodies into mechanical torque via hydraulic turbines, driving synchronous electromagnetic alternators.

$\text{Power } (P) = \eta \cdot \rho \cdot g \cdot Q \cdot H$

Where $\eta$ is overall turbine-generator efficiency, $\rho$ is water density ($1000\text{ kg/m}^3$), $g$ is acceleration due to gravity ($9.81\text{ m/s}^2$), $Q$ is volumetric flow discharge rate ($\text{m}^3\text{/s}$), and $H$ is effective hydraulic head (vertical drop in meters).

Indian Administrative Classification

In Indian energy governance, hydroelectric projects are strictly categorized by capacity:

• Small Hydro Power (SHP): Projects with a total installed capacity of $\le 25\text{ MW}$. These fall under the administrative jurisdiction of the Ministry of New and Renewable Energy (MNRE). SHP is universally classified as non-conventional renewable energy due to its minimal reservoir footprint, low submerged biomass, and negligible community displacement.
• Large Hydro Power: Projects with capacity $> 25\text{ MW}$. Historically administered by the Ministry of Power and classified as conventional power. However, in March 2019, the Union Cabinet formally approved measures declaring large hydro projects as a renewable energy source, introducing Hydro Purchase Obligations (HPOs) within the Non-Solar Renewable Purchase Obligation (RPO) basket to incentivize grid flexibility.
• Operational Typologies:
  • Run-of-the-River (RoR): Diverts upstream river discharge through headrace tunnels to powerhouse turbines before returning it to the natural stream bed downstream, utilizing minimal or zero storage impoundment.
  • Reservoir / Storage Schemes: Impounds water behind massive dams, permitting seasonal dispatch control and peak shaving.
  • Pumped Storage Plants (PSP): Closed-loop or open-loop hydraulic batteries consisting of two reservoirs at different elevations. During off-peak surplus periods (e.g., midday solar peaks), water is pumped uphill; during peak demand, water releases downward through reversible pump-turbines, providing vital grid frequency stabilization and inertia.

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2.4 Biomass and Biofuels

Biomass represents organic matter in which chemical energy is stored via photosynthetic carbon fixation. When combusted, biomass releases carbon that was absorbed from the modern atmosphere, rendering it theoretically carbon-neutral across its lifecycle, provided harvesting rates do not exceed biological regrowth rates.

Conversion Pathways

1. Direct Combustion: Burning wood, agricultural crop residues, or bagasse in industrial boilers to generate steam for electricity generation and co-generation (combined heat and power - CHP).
2. Thermochemical Gasification: Sub-stoichiometric thermal oxidation of solid biomass at high temperatures (700°C–1000°C) with restricted oxygen, producing producer gas / syngas—a flammable mixture composed primarily of carbon monoxide ($CO$), hydrogen ($H_2$), methane ($CH_4$), and inert nitrogen ($N_2$).
3. Biochemical Anaerobic Digestion: Microbial decomposition of wet organic wastes (cattle dung, municipal sewage, distillery effluents) in the absence of elemental oxygen by methanogenic bacteria. Produces Biogas, typically composed of:
   • Methane ($CH_4$): 55% to 70%
   • Carbon Dioxide ($CO_2$): 30% to 45%
   • Trace components: Hydrogen sulfide ($H_2S$, corrosive), water vapor, and nitrogen.

The Four Generations of Biofuels

Generation       Feedstock Utilized                     Key Advantages & Environmental Trade-offs
──────────────   ────────────────────────────────────   ─────────────────────────────────────────────
1st Gen (1G)     Food crops (Sugarcane, Corn, Wheat,    Mature technology; triggers the severe
                 Edible vegetable oils)                 "Food vs. Fuel" dilemma and raises food prices

2nd Gen (2G)     Non-food lignocellulose (Crop residue, Avoids food competition; utilizes stubble
                 Rice straw/Parali, Bagasse, Jatropha)  (reducing air pollution); complex enzymes needed

3rd Gen (3G)     Aquatic microalgae & macroalgae        Extremely high lipid yield per acre; cultivable
                 (Seaweed)                              on brackish water/waste land; high CAPEX

4th Gen (4G)     Genetically engineered cyanobacteria   Photobiological direct hydrocarbon synthesis;
                 & synthetic metabolic microorganisms   Acts as a net carbon-negative sink

• National Policy on Biofuels (2018, Amended 2022): The Government of India originally targeted 20% ethanol blending in petrol by 2030. In the 2022 policy amendment, this target was aggressively advanced to 2025–26 (E20 Target). It expanded allowable feedstocks to include sugarcane juice, B-heavy molasses, damaged food grains (broken rice), and surplus food grains.
• SATAT Initiative: Sustainable Alternative Towards Affordable Transportation promotes the setup of Compressed Bio-Gas (CBG) plants from agricultural residues, cattle dung, and municipal solid waste.

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2.5 Geothermal and Ocean Energy

• Geothermal Energy: Exploits the thermal gradient of the Earth's crust (typically increasing by 25°C to 30°C per kilometer depth). Deep hydrothermal reservoirs contain steam or pressurized hot water that can be tapped to drive steam turbines. Key Indian geothermal geothermal provinces identified by the Geological Survey of India (GSI) include:
  • Puga Valley and Chumathang: Located in Ladakh, exhibiting the highest geothermal potential in India (ONGC has executed India's first pilot geothermal exploration project at Puga).
  • Manikaran: Parbati Valley, Himachal Pradesh.
  • Tattapani: Balrampur-Ramanujganj district (carved out of Surguja), Chhattisgarh.
  • Bakreshwar: West Bengal.
  • Narmada-Son-Tapti and Godavari grabens.
• Ocean Energy Systems:
  • Tidal Energy: Exploits gravitational ocean tides driven by the moon and sun. Requires a mean tidal range of at least 5 meters between high and low tide. Major Indian prospective sites: Gulf of Khambhat and Gulf of Kutch in Gujarat, and the Sundarbans in West Bengal.
  • Wave Energy: Harnesses surface wave kinetic and potential energy through oscillating water columns.
  • Ocean Thermal Energy Conversion (OTEC): Exploits the temperature differential (minimum $\Delta T \ge 20^\circ\text{C}$) between warm tropical ocean surface water (~25–28°C) and cold deep ocean water (~4–7°C at 1,000 meters depth) via closed-cycle ammonia Rankine systems.

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3. Nuclear Energy and India's Three-Stage Programme

Nuclear energy generates electricity by harnessing the mass defect binding energy released during the fission of heavy atomic nuclei. When a fissile nucleus such as Uranium-235 ($^{235}U$) absorbs a thermal neutron, it splits into lighter fission products, releasing 2 to 3 prompt neutrons and approximately 200 MeV of thermal energy per fission event:

$^{235}_{92}\text{U} + \text{ }^1_0n \longrightarrow \text{ }^{141}_{56}\text{Ba} + \text{ }^{92}_{36}\text{Kr} + 3\text{ }^1_0n + \sim 200\text{ MeV}$

• Fissile Materials: Isotopes capable of sustaining a chain reaction with slow (thermal) neutrons: $^{235}U$, $^{239}Pu$, $^{233}U$.
• Fertile Materials: Isotopes that cannot sustain a thermal chain reaction directly, but can capture a neutron to transmute into fissile isotopes: $^{238}U$ (transmutes into $^{239}Pu$) and $^{232}Th$ (transmutes into $^{233}U$).

Dr. Homi J. Bhabha's Three-Stage Nuclear Power Programme

Because India possesses limited domestic uranium reserves (less than 2% of global reserves) but approximately 25% of the world's thorium reserves (contained within the monazite sands along the coastlines of Kerala, Tamil Nadu, and Odisha), Dr. Homi Bhabha designed a closed, self-sustaining sequential fuel cycle:

[Stage 1: PHWR] ──────────> [Stage 2: FBR] ──────────> [Stage 3: AHWR]
Natural Uranium (0.7% U-235)  Plutonium-239 + U-238 / Th-232  Thorium-232 + Bred U-233
Moderator/Coolant: D2O (Heavy Water)  Coolant: Liquid Sodium (Fast Neutrons)  Self-Sustaining Thorium Cycle
Byproduct: Plutonium-239      Breeds: More Pu-239 & Fissile U-233   Taps India's Vast Monazite Reserves

1. Stage 1: Pressurized Heavy Water Reactors (PHWRs):
   • Fuel: Natural Uranium (containing only 0.7% fissile $^{235}U$ and 99.3% fertile $^{238}U$).
   • Moderator & Coolant: Heavy Water (Deuterium Oxide, $D_2O$). Heavy water has an exceptionally low neutron absorption cross-section, allowing un-enriched natural uranium to sustain a critical chain reaction.
   • Byproduct: Fertile $^{238}U$ absorbs excess neutrons to breed fissile Plutonium-239 ($^{239}Pu$), which is extracted via chemical reprocessing of spent fuel.
2. Stage 2: Fast Breeder Reactors (FBRs):
   • Fuel Core: Plutonium-239 extracted from Stage 1 mixed with uranium oxide (MOX fuel).
   • Blanket: Fertile $^{238}U$ or Thorium-232 ($^{232}Th$).
   • Coolant: Liquid Sodium metal (operates at high temperatures with unpressurized fast neutrons; requires no moderator).
   • Breeding Principle: The reactor generates more fissile material than it consumes. The $^{232}Th$ blanket absorbs fast neutrons and undergoes beta decay to breed fissile Uranium-233 ($^{233}U$).
   • Flagship Installation: 500 MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam, Tamil Nadu.
3. Stage 3: Advanced Heavy Water Reactors (AHWRs):
   • Fuel: Thorium-232 coupled with bred Uranium-233.
   • Operation: Complete utilization of India's vast domestic thorium reserves in an indefinitely sustainable, closed nuclear fuel cycle.

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4. India's Clean Energy Commitments & Targets (Panchamrit)

At the COP26 United Nations Climate Change Conference in Glasgow (2021), India announced five monumental national climate commitments, termed the Panchamrit (Five Nectars):

1. 500 GW Non-Fossil Electricity Capacity: Achieve 500 gigawatts of non-fossil fuel installed electric power capacity by 2030.
2. 50% Renewable Energy Requirement: Meet 50% of the country's energy requirements from renewable energy by 2030. In the updated NDC of August 2022 this was formalised as about 50% of cumulative electric power installed capacity from non-fossil sources by 2030.
3. 1 Billion Tonnes Carbon Reduction: Reduce projected total carbon emissions by 1 billion tonnes between 2021 and 2030.
4. 45% Carbon Intensity Reduction: Reduce the carbon emission intensity of India's Gross Domestic Product (GDP) by 45% by 2030 compared to 2005 baseline levels.
5. Net-Zero Emissions by 2070: Attain absolute net-zero greenhouse gas emissions by 2070.

India reached the NDC capacity goal early: in June 2025, non-fossil sources (solar, wind, large and small hydro, biomass and nuclear) crossed 50% of installed electricity capacity, five years ahead of 2030. By 31 March 2026, non-fossil capacity stood at about 283 GW. The 500 GW target is still some distance away, and the non-fossil share of electricity actually generated is lower than its share of capacity, because coal plants run for more hours than solar and wind plants.

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5. Comprehensive Energy Comparison Matrix

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6. Exam Traps & Common Misconceptions

• Trap 1: The Wind Power Scaling Law: Examination questions often state: "If the wind speed at a site doubles, by what factor does power output increase?" Many candidates incorrectly answer 2 times or 4 times. Because power varies with the cube of wind speed ($P \propto v^3$), doubling wind speed increases the power output by $2^3 = 8\text{ times}$.
• Trap 2: Thorium's Fissility Status: A recurring exam trap asks whether Thorium-232 can be used directly as reactor fuel in Stage 1 nuclear plants. Thorium-232 is fertile, not fissile. It cannot sustain a chain reaction on its own and cannot be used in Stage 1 PHWRs; it must first be irradiated with neutrons in a breeder reactor to transmute into fissile Uranium-233.
• Trap 3: Administrative Classification of Hydro Power: Small Hydro Power (SHP) is strictly defined in India as installations with capacity $\le 25\text{ MW}$, governed by the Ministry of New and Renewable Energy (MNRE). Projects exceeding 25 MW are Large Hydro, historically under the Ministry of Power (though reclassified for renewable purchase obligations in 2019).
• Trap 4: Biofuel Feedstock Generations: Remember that First Generation (1G) biofuels utilize edible human food crops (competing with nutrition), Second Generation (2G) biofuels utilize non-food crop residues and lignocellulosic stubble, Third Generation (3G) relies on algae, and Fourth Generation (4G) utilizes synthetic genetically engineered microbes.