With reference to technology for solar power production, consider the following statements: 1. 'Photovoltaics' is a technology that generates electricity by direct conversion of light into electricity, while 'Solar Thermal' is a technology that utilizes the Sun's rays to generate heat which is further used in electricity generation process 2. Photovoltaics generates Alternating Current (AC), while Solar Thermal generates Direct Current (DC) 3. India has manufacturing base for Solar Thermal technology, but not for photovoltaics Which of the statements given above is/are correct?
Contents19
- A1 only
- B2 and 3 only
- C1, 2 and 3
- DNone
Show answer
Answer: (A) 1 only
Statement 1 — CORRECT:
Photovoltaic (PV) technology converts sunlight DIRECTLY into electricity using semiconductor cells (like silicon).
Solar Thermal technology uses mirrors/lenses to concentrate sunlight → generate heat → boil water → produce steam → spin turbines → generate electricity (indirect conversion via heat).
Statement 2 — WRONG:
It's the reverse!
PV generates Direct Current (DC), which is then converted to AC using an inverter.
Solar Thermal, using turbines, generates Alternating Current (AC) directly.
Statement 3 — WRONG:
India DOES have a PV manufacturing base (companies like Tata Solar, Vikram Solar, Adani Solar).
India actually has a larger PV manufacturing base than a solar thermal one.
Only statement 1 is correct.
Solar power has two main technologies: photovoltaics (direct light-to-electricity conversion using semiconductors) and solar thermal (using concentrated sunlight to create heat, then steam, then electricity through turbines).
The key trap is the current type confusion - PV cells generate DC current like batteries, while thermal plants with spinning turbines generate AC current like conventional power plants.
UPSC is testing whether students can distinguish between direct conversion technology (PV) versus heat-based conversion technology (thermal) and their respective electrical outputs.
Photovoltaic Technology
Science And Technology Photovoltaics direct conversion light into electricity
Photovoltaic Technology: Direct Solar-to-Electric Conversion
PV cells convert sunlight directly into electricity using semiconductor materials
PV generates Direct Current (DC) — needs inverters to convert to AC
India has established PV manufacturing base with companies like Tata Solar, Vikram Solar
Common materials: silicon, gallium arsenide, cadmium telluride
How It Works
Photovoltaic effect occurs when photons from sunlight knock electrons loose from atoms in semiconductor material, creating electrical current. No moving parts, no heat conversion — pure light-to-electricity transformation.
PV Electricity Generation
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Sunlight hits PV cell**
Photons carry energy`"]
s2["`**Electrons get excited**
Silicon atoms release electrons`"]
s3["`**Electric field separates charges**
Built-in electric field in cell`"]
s4["`**DC electricity flows**
Electrons flow through external circuit`"]
s5["`**Inverter converts DC to AC**
For grid connection and home use`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5PV Cell Types
Type | Efficiency | Cost | Applications |
|---|---|---|---|
Monocrystalline Silicon | 18-22% | High | Rooftop, premium installations |
Polycrystalline Silicon | 15-18% | Medium | Most common commercial use |
Thin Film | 10-15% | Low | Large-scale installations, flexible panels |
Key Characteristics
No fuel needed — only sunlight, making it truly renewable
Modular — can scale from watts to megawatts
Silent operation — no mechanical parts, minimal maintenance
Decreasing costs — prices dropped 90% between 2009-2019
Trap: PV generates DC, not AC — Statement 2 reverses this basic fact
Trap: Confusing 'direct conversion' — PV is light→electricity, Solar Thermal is light→heat→electricity
Trap: India does have PV manufacturing — Statement 3 claims we don't
Solar Thermal Technology
Science And Technology Solar Thermal Sun's rays generate heat electricity generation process
Solar Thermal Technology: Heat-Based Power Generation
Uses mirrors/lenses to concentrate sunlight and generate heat
Indirect conversion: light→heat→steam→turbine→electricity
Generates Alternating Current (AC) directly through turbines
Can include thermal storage for power generation after sunset
Core Principle
Solar thermal concentrates sunlight using mirrors to create intense heat (500-1000°C). This heat boils water into steam, which spins turbines connected to generators — same principle as coal/nuclear plants, but using solar heat.
Solar Thermal Process
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Mirrors concentrate sunlight**
Parabolic mirrors or heliostats focus light`"]
s2["`**Heat transfer fluid gets hot**
Oil, molten salt, or water heated to 400-1000°C`"]
s3["`**Water converts to steam**
Heat exchanger boils water`"]
s4["`**Steam spins turbine**
High-pressure steam drives turbine blades`"]
s5["`**Generator produces AC**
Turbine rotation generates alternating current`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5Solar Thermal Technologies
Technology | Concentration | Temperature | Scale |
|---|---|---|---|
Parabolic Trough | 30-80x | 400°C | 50-300 MW plants |
Solar Power Tower | 200-1000x | 800-1000°C | 50-400 MW plants |
Dish Sterling | 1000-3000x | 750°C | 5-50 kW units |
Linear Fresnel | 30-100x | 300-500°C | 50-200 MW plants |
Advantages Over PV
Energy storage — molten salt can store heat for 6-15 hours
Grid stability — AC generation matches grid requirements
Higher efficiency at utility scale in high solar radiation areas
Dispatchable — can generate power when needed, not just when sun shines
Trap: Solar Thermal generates AC directly, not DC — Statement 2 swaps this
Trap: Remember it's indirect conversion — light becomes heat first, then electricity
Trap: Don't confuse with solar water heaters — this is for electricity generation
Solar Manufacturing in India
Science And Technology India manufacturing base Solar Thermal technology photovoltaics
India's Solar Manufacturing Ecosystem & Policy Support
India has strong PV manufacturing base — Statement 3 is wrong
Major PV companies: Tata Solar, Vikram Solar, Adani Solar, Waaree
National Solar Mission target: 100 GW solar capacity by 2022
Solar thermal manufacturing is limited compared to PV
Manufacturing Reality
India has a well-established PV manufacturing base with domestic companies producing solar panels, inverters, and balance-of-system components. Solar thermal manufacturing is more limited due to lower demand and technical complexity.
Major Indian Solar Companies
Company | Technology Focus | Capacity | Key Strengths |
|---|---|---|---|
Tata Solar | PV panels, systems | 300+ MW | Integrated solutions |
Vikram Solar | PV modules | 1.3+ GW | Largest Indian manufacturer |
Adani Solar | PV cells, modules | 1.3+ GW | Vertically integrated |
Waaree Energies | PV modules, EPC | 1.5+ GW | Export-focused |
Premier Energies | PV cells, modules | 600+ MW | Technology innovation |
Policy Support Measures
PLI Scheme — ₹4,500 crore production-linked incentives for solar PV
ALMM List — Approved List of Models and Manufacturers ensures quality
DCR Policy — Domestic Content Requirements in government projects
MNRE support — Ministry of New and Renewable Energy provides subsidies
Challenges & Opportunities
Import dependency — still imports cells and wafers from China
Scale advantage — Chinese manufacturers benefit from larger scale
Technology gap — working to develop advanced cell technologies
Growing market — domestic demand creates expansion opportunities
Trap: India does have PV manufacturing — don't fall for Statement 3's claim
Trap: Manufacturing exists for both technologies, but PV base is much stronger
Remember: Tata Solar, Vikram Solar are household names in UPSC energy questions
AC vs DC Power Generation
Science And Technology Alternating Current Direct Current AC DC
AC vs DC in Power Generation: Key Distinctions
PV generates DC — needs inverters to convert to AC for grid
Turbine-based systems generate AC — including solar thermal, wind, hydro
Grid uses AC — easier to transmit over long distances
DC is coming back — HVDC transmission, electric vehicles, LED lights
Why This Matters
Understanding AC vs DC generation helps distinguish power technologies. Mechanical rotation (turbines) naturally produces AC. Electronic processes (PV, batteries, fuel cells) produce DC.
Power Generation Types
Technology | Current Type | Conversion Needed | Reason |
|---|---|---|---|
Photovoltaic | DC | DC→AC inverter | Electronic process |
Solar Thermal | AC | None | Turbine rotation |
Wind Power | AC | None | Turbine rotation |
Hydroelectric | AC | None | Turbine rotation |
Coal/Gas Plants | AC | None | Turbine rotation |
Batteries | DC | DC→AC inverter | Chemical process |
Fuel Cells | DC | DC→AC inverter | Electrochemical process |
AC vs DC Characteristics
AC advantages: Easy voltage transformation, long-distance transmission, standard grid compatibility
DC advantages: No reactive power losses, better for electronics, efficient for short distances
Inverter technology: Converts DC to AC with 95%+ efficiency in modern systems
Future trend: More DC applications due to electronics, EVs, and energy storage
Trap: PV = DC, Solar Thermal = AC — Statement 2 reverses this completely
Trap: Don't confuse the source (what generates) with end use (what we consume)
Memory aid: 'PV = DC' — both have same letters, both are electronic/direct