(SEM VII) THEORY EXAMINATION 2022-23 RENEWABLE ENERGY RESOURCES

SECTION A (2 Marks Each)

(a) Importance of Solar Cells

Solar cells convert sunlight directly into electricity, reduce dependence on fossil fuels, and provide clean, renewable energy with low operating cost.

(b) Scope of Renewable Energy

The scope includes power generation, heating, transportation fuels, rural electrification, energy security, and environmental protection.

(c) Solar Radiation and Its Benefits

Solar radiation is energy received from the sun. It is abundant, free, renewable, and useful for electricity generation, heating, and drying.

(d) Solar Irradiance and Sun Peak Hours

Solar irradiance is the power of solar radiation per unit area (W/m²). Sun peak hours represent equivalent hours of full-sun intensity in a day.

(e) Sources of Geothermal Energy

Geothermal energy comes from hot springs, geysers, volcanic regions, and underground hot water reservoirs.

(f) Types of MHD System

Open cycle MHD system and closed cycle MHD system.

(g) Thermionic Conversion

Thermionic conversion converts heat energy directly into electrical energy using electron emission from a heated surface.

(h) Cut-in Speed and Tip Speed Ratio

Cut-in speed is the minimum wind speed at which a turbine starts generating power. Tip speed ratio is the ratio of blade tip speed to wind speed.

(i) Advantages of Anaerobic Digestion

It produces biogas and reduces organic waste while generating useful manure.

(j) Methanogenesis

Methanogenesis is the biological process in which microorganisms produce methane gas under anaerobic conditions.

SECTION B (10 Marks Each – Any Three)

(a) Conventional vs Renewable Energy Resources

Conventional energy resources such as coal, oil, and gas are limited and polluting, while renewable energy sources like solar, wind, biomass, and geothermal are clean, sustainable, and environmentally friendly. Renewable energy reduces carbon emissions and ensures long-term energy availability.

(b) Solar Cell Power Plant and Applications

A solar cell power plant converts sunlight into electricity using photovoltaic panels. Major components include solar panels, inverters, batteries, and control systems. Applications include residential power supply, street lighting, water pumping, and grid-connected power generation.

(c) Geothermal Energy Resources and Direct Uses

Geothermal resources include hydrothermal reservoirs, hot dry rocks, and magma. Direct uses include space heating, greenhouse heating, drying of crops, and industrial process heating.

(d) Tidal and Wave Energy Mechanism

Tidal energy uses the rise and fall of sea levels to drive turbines, while wave energy captures surface wave motion. Both are predictable and renewable but location-specific.

(e) Solid Biomass, Liquid Biofuels, and Biogas

Solid biomass includes wood and agricultural waste, liquid biofuels include ethanol and biodiesel, and biogas is produced by anaerobic digestion of organic matter.

SECTION C (10 Marks Each)

Q3 (a) Renewable Energy Classification and Solar Conversion

Renewable energy includes solar, wind, hydro, biomass, geothermal, and ocean energy. Solar energy is absorbed by collectors or photovoltaic cells and converted into thermal or electrical energy. High efficiency depends on material quality, radiation intensity, temperature, and system design.

Q3 (b) Solar Thermal Power Plant

A solar thermal power plant uses mirrors or collectors to concentrate sunlight and produce heat, which generates steam to run turbines. The process includes collection, heat transfer, steam generation, turbine operation, and electricity generation.

Q4 (a) Solar Flat Plate Collector

A flat plate collector consists of an absorber plate, transparent cover, insulation, and fluid tubes. It absorbs solar radiation and transfers heat to the working fluid for water or space heating.

Q4 (b) Solar Concentrators

Solar concentrators use mirrors or lenses to focus sunlight onto a receiver. Types include parabolic troughs, parabolic dishes, and heliostat fields, mainly used in solar thermal plants.

Q5 (a) Flash Steam and Dry Steam Plants

Flash steam plants use high-pressure hot water that flashes into steam, while dry steam plants directly use natural steam from underground reservoirs to drive turbines.

Q5 (b) MHD Power Generation System

MHD power generation converts thermal energy of ionized gas directly into electricity. It is classified into 

open and closed cycle systems and is used for high-efficiency power generation.

Q6 (a) Wind Energy and Windmill Components

Wind energy converts kinetic energy of wind into electrical energy. Main components include blades, rotor, nacelle, gearbox, generator, and tower.

Q6 (b) Thermoelectric Power Generator

Thermoelectric generators convert heat directly into electricity using the Seebeck effect. They are reliable and compact but have low efficiency and high material cost.

Q7 (a) Anaerobic Digestion Process

Anaerobic digestion involves hydrolysis, acidogenesis, acetogenesis, and methanogenesis to convert biomass into biogas and slurry.

Q7 (b) OTEC and Its Types

OTEC uses temperature difference between warm surface water and cold deep water to generate electricity. Types include closed cycle, open cycle, and hybrid OTEC systems.