Renewable Energy
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Known as Non-Conventional energy
Inexhaustible
No Pollution
Eg: Solar Energy
Wind Energy
Biomass Energy
Hydro Power
Fuel Cell
Energy from Wastes
Wave Energy
Tidal Energy
Geothermal Energy
Fundamentals of Solar Energy
• Solar Constant
• Solar Insolation
Solar Energy
Solar Thermal Energy
Solar Electrical Energy
Solar Thermal Energy
• Solar Water Heating System (Flat-plate collector & Evacuated tube collector)
• Solar Thermal Power Systems (Power tower, Parabolic through collector)
Solar Water Heating System
• Consists of
1. Flat plate / Evacuated tube solar collector
2. Storage tank
3. Connecting pipes
• Installed on roof or on open ground
Figure 1 : Solar water Heating System
Solar Flat Plate Collector
• Heats the circulating fluid to 40-60°C
• Highly dependent upon ambient temperatures
• Usually comprises of copper sheets with toughened glass sheet on top for cover and insulating
material at bottom. The entire assembly is placed in a flat box.
Figure 2 : Solar Flat Plate Collector
Evacuated Tube Collector
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Used for higher temperature
Less dependent upon ambient temperature
Can reach temperature up to 150°C
Evacuated glass tubes are used instead of copper
Comprises of two concentric glass tubes fused in the ends
Air is evacuated from the gap between the conductors
The vacuum permits the heat radiation to enter the outer tube
Absorbent coating on the inner tube converts short wave radiation to long wave radiation
Heat loss is less than 10% compared with 40% in flat plate collector
Figure 3 : Solar Flat Plate Collector
Figure 4 : Cut view of Evacuated Tube Collector
Solar Electrical Energy
• Through Solar Thermal Power Stations
• Direct conversion through photovoltaic
Solar Thermal Power Stations
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Power Tower
Parabolic through collector
Power Tower
1. Sunlight is concentrated and directed from a large field of heliostats (mirrors) to a receiver on a
tall tower
2. Molten salt (for example liquid sodium) from the cold salt tank is pumped through the central
receiver (where it is heated to 566°C)
3. The heated salt from the receiver is stored in the hot salt thermal storage tank
4. Molten salt is pumped from the hot salt tank through a steam generator, that creates steam,
which drives a steam turbine generating electricity
5. Cold salt at 288°C flows back to the cold salt thermal storage tank and is re-used
Figure 5 : Solar Thermal Power Stations
Parabolic Through Collector
• The system uses a series of specially designed parabolic curved, trough shaped reflectors that focus
the sun’s energy onto a receiver tube running at the focus of the reflector
• Water in the receiver is heated to a temperature of about 400°C
Figure 6 : Parabolic Trough Collector
Solar Photovoltaic Technology
• Based on the principle of Photoelectric Effect
• Photoelectric effect or Photovoltaic effect is the process in which two dissimilar materials in close
contact produce an electrical voltage when struck by light or radiant energy
• The photoelectric effect occurs when a photon which has the correct amount of energy strikes an
atom in the solar cell
Figure 7 : Solar Photovoltaic Effect
Solar PV System
• A photovoltaic (PV) module comprise of PV panels (Solar Panels), battery system, charge controller
and inverter
• Solar cells are connected in series and parallel combinations to form modules that provide the
required power
• Different types of PV systems are,
1. Stand-alone SPV Power Plant
2. Grid connected Solar System
3. Building-integrated PV System
Figure 8 : PV System
Stand-alone SPV Power Plant
• In an SPV power plant, electricity is centrally generated and made available to users through a local
grid in a `stand-alone mode’
• Used for electrification of remote villages, hospitals, hotels, communication equipment, railway
stations, border outposts etc.
Grid Connected Solar System
• Uses an inverter that synchronizes with utility power
• Do not require batteries
• Easier to install and maintain
Figure 9 : Grid Connected Solar
Building-integrated PV Systems
• PV panels are integrated into the roof or facade of a building
• BIPV provides photovoltaic power as well as weather proofing and glazing of buildings
Figure 10 : BIPV
Wind Energy
• Modern windmills are normally called as wind turbines
• They are also called as wind energy conversion systems (WECS), and those are used to generate
electricity are described as wind generators
• The most common type of wind turbine is horizontal-axis machines
• Horizontal axis wind turbines have a main rotor shaft and electrical generator at the top of a tower,
and must be pointed into the wind
• Blades on rotor of horizontal-axis machines can be in the front (upwind) or behind (downwind) of
the tower
Components of wind turbine system
1. Rotor
• The shape of rotor blade and angle in relation to the relative wind direction affect the aerodynamic
performance of the blades
• Rotors can be single-bladed, two-bladed or three-bladed
• Two and three-bladed rotors are commonly used for power generation
2. Nacelle Assembly
• Nacelle is the part of wind turbine at the top of tower housing containing gear box, generator
assemblies and any control component
Figure 11 : Rotor and Blades
Figure 12 : Nacelle Assembly
3. Low-speed shaft
• Main shaft, connected directly to the rotor hub
• Rotor turns the low-speed shaft at about 30 to 60 rpm
4. High-speed shaft
• Connected to the low-speed shaft by gear box and drives the generator
• Will turn at between 1,000 and 1,800 rpm
5. Gear box
• Connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from about
30 to 60 rpm to about 1,000 to 1,800 rpm
6. Generator
• Converts turning motion of wind turbines blades into electricity
7. Disc Brake
• Located on the main shaft before the gear box or on high speed shaft after the gear box
• Used to slow down the motor
8. Yaw Control
• Used to align rotor axis with wind direction
Operating Characteristics of Wind Turbine
Figure 13 : Idealised Power Curve for a Wind turbine
Biomass Energy
• Biomass is basically organic matter such as wood, straw, crops, sewage sludge, animal waste etc.
• Bioenergy is the energy derived from biomass
Methods used to generate energy from biomass are:
1. Direct Combustion of Biomass
2. Gasification of Biomass
3. Biomethanation of Biomass
4. Biofuels from Biomass
1. Direct Combustion of Biomass
• Combustion of biomass in a grate, stoker or fluidized bed with excess air followed by capturing the
release of energy, which is used to produce electricity
• Solid biomasses include coconut shells, rice husks, baggage, wood waste etc.
• Biomasses of low bulk density are processed into pellets or briquettes
2. Gasification of Biomass
• Partial combustion of biomass and takes place at temperature of about 1000°C
• Facilitated by supplying less than stoichiometric requirement
• The product of combustion are combustible gases like Carbon monoxide (CO), Hydrogen (H₂) and
traces of Methane (CH₄) and non-useful products like tar and dust
• The biogas produced through gasification is called as producer gas
• A gasification system consists of four main stages
1. Feeding of feedstock
2. Gasifier reactions where gasification takes place
3. Cleaning of resultant gas
4. Utilization of cleaned gas
Figure 14 : Gasifier
3. Biomethanation of Biomass
• The process is based on biological digestion/anerobic digestion
• The raw materials include manure, sewage sludge, municipal solid waste etc.
• The biogas process is also known as anaerobic digestion or fermentation
Figure 15 : Biogas Plant
4. Biofuels from Biomass
• Biomass can be converted into liquid fuels such as Ethanol and biodiesel partially replace
conventional petroleum fuels
• Ethanol is commonly produced by fermentation of molasses, a by-product in sugar manufacture
• Ethanol is also produced by fermenting any biomass feedstock rich in carbohydrates
• The most economical way of producing biodiesel is by transesterification of extracted oil (e.g.
Jatropha seeds oil) with alcohol such as methanol
Figure 16 : Biodiesel Cycle
Hydro power
• The most common way of using hydro power is to use a turbine which is turned by water moving
in a controlled manner
Classification of Hydropower by Size
Large-hydro​
More than 25 MW and feeding into utility grid​
Small-hydro​
2001 kW - 25 MW – usually feeding a grid​
Mini-hydro​
101 kW to 2MW ; either stand-alone or feeding a grid​
Micro-hydro​
From 11 kW to 100 kW; usually providing power
for remote areas away from grid
Pico-hydro​
From a few hundred watts up to 10 kW​
Figure 17 : Main Components and Layout of a run-of-the river micro-hydro Scheme
Water into Watts
Theoretical Power (P) = Flow rate (Q) x Gravity (g)
P = 9.81 x Q x H
Fuel Cell
• Input to fuel cell is hydrogen
• Hydrogen combines with oxygen to produce electricity through an electrochemical process
Operation of Fuel Cell
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A fuel cell consists of two catalyst coated electrodes surrounding an electrolyte
One electrode is anode and other is cathode
The process begins when hydrogen molecules enter the anode
The catalyst coating separates hydrogen's electrons from protons
The electrolyte allows the protons to pass through to the cathode
The oxygen and the protons combine with electrons after they have passed through the external
circuit producing water and heat
• Individual fuel cells can be placed in a series to form a fuel cell stack. The stack can be used in a
system to power a vehicle or to provide stationary power to a building
Figure 18 : fuel cell
Energy from wastes
• Energy can be recovered from wastes via combustion of waste in incinerators
Power Generation from landfill gas
• Biogas produced from landfill is known as Landfill gas
• This process is based on anaerobic digestion
• Landfill gas is composed of mainly methane and carbon dioxide
Figure 19 : Energy from wastes
Figure 20 : Power Generation from landfill Gas
Wave Energy
• Contains 1000 times the Kinetic energy of wind
• Kinetic energy from waves can be used to power a turbine
• When the wave rise into the chamber it forces the air out of the chamber leads to the
rotation of turbine
• When wave goes down, air flows back to chamber through turbine leads to the rotation
of energy
Figure 21 : Wave Energy
Tidal Energy
• When tides come into the shore, they can be trapped in reservoirs behind dams
• When tide drops, the water behind dam can be let out just like in a regular hydroelectric
power plant
• Height difference needs to be at least 5m for practicable energy production
Figure 22 : Tidal Energy
Geothermal Energy
• Hot water from magma layer is used to produce electricity
• No fuel is burned to heat water into steam
• Different types of geothermal power plants are,
1. Dry Steam Power Plants
2. Flash Steam Power Plants
3. Binary Cycle Power Plant
1. Dry Steam Power Plant
• Steam from hydrothermal production well used to generate electricity
• After usage steam is condensed and returned to geothermal reservoir
Figure 23 : Dry Steam Power Plant
2. Flash Steam Power Plant
• Draws hot water from hydrothermal production well to flash tank
• Drop in pressure at flash tank flashes the hot water (182°C) to steam
Figure 24 : Flash Steam Power Plant
3. Binary Cycle Power Plant
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Operate on lower temperature waters (107°C to 182°C)
Geothermal water is used to heat working fluid
Hot working fluid is vaporised and used to turn turbine
Geothermal water and working fluid are confined to separate loops
Figure 25 : Binary Cycle Power Plant