Renewable Energy Systems Course Overview

EE8703 – RENEWABLE ENERGY SYSTEMS Department of EEE 2022-2023
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DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
SUBJECT CODE & NAME: EE8703- RENEWABLE ENERGY SYSTEMS
YEAR/SEMESTER: IV/VII
QUESTION BANK
UNIT – I: RENEWABLE ENERGY (RE) SOURCES
PART – A
1. What are Fossil Fuels?
Fossil fuels are buried flammable geologic deposits of organic substances such as dead
plants, and animals that got deposited under several thousand feet of silt. These deposits
decayed with the passage of time and got converted to natural gas, coal, and petroleum due
to the extreme heat and pressure inside the earth’s crust. They are also known as non-
renewable sources of energy as it takes a very long time for it to replenish.
2. Give the types of fossil fuels.
Fossil fuels are of the following types:
• Coal
• Petroleum
• Natural gas
3. Brief about the fossil fuel coal.
Coal
• It is a hard, black coloured substance made up of carbon, hydrogen, nitrogen,
• oxygen, and sulphur.
• The major types of coal are- anthracite, bituminous and lignite.
• Anthracite has a higher carbon concentration and is the hardest type of coal.
• Lignite has a high concentration of oxygen and hydrogen but a low
• concentration of carbon.
• Bituminous is a moderate form of coal.
• Coal is processed industrially to obtain derivatives like coke, coal tar, and coal gas.
4. Discuss on the formation of coal.
Formation of Coal:
• The process of formation of coal is known as carbonization.
• The dense forest present in the low-lying wetland got buried in the earth
• millions of years ago.
• Soil kept depositing over them and they got compressed.
• As they went deeper and deeper, they faced high temperature and pressure.
• As a result, the substances slowly got converted into coal.
5. What are the uses of coal?
Uses of Coal
• Coal was used to produce steam in the railway engines initially.
• It is used to cook food.
• It is used to generate electricity in thermal plants.
• It is used in industries as fuel.

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6. Brief on petroleum
Petroleum
• It is a clear, oily liquid, usually green or black in colour.
• It has a very strange smell and is a mixture of petroleum gas, diesel, paraffin wax, petrol,
lubricating oil, etc.
• It is also termed as “Black Gold” because of its wide range of uses in many industries.
7. Discuss on the formation of petroleum.
Formation of Petroleum
• The sea animals and plants died and their bodies settled at the bottom of the sea.
• They got compressed by the layers of sand and clay.
• Their encounter with high temperature and pressure converts them into
o petroleum.
• The petroleum is separated from the crude oil by a series of processes in a refinery. This is
known as petroleum refining.
8. What are the uses of Petroleum?
• It is used to power internal combustion engines in the form of petrol.
• It is used in roofing, road pavements, and as a water repellent.
• It is used in manufacturing detergents, plastics, fibres, polyethene, etc.
9. Brief on Natural gas
• It is a clean and non-toxic fossil fuel.
• It is colourless and odourless and can be easily transferred through pipelines.
• It is stored as compressed natural gas (CNG) under high pressure.
• It is less polluting and less expensive fossil fuel.
• Methane is the most important natural gas.
10. Brief on the formation of Natural Gas.
The phytoplankton and zooplankton sink to the bottom of the ocean and mix with organic
materials to form an organic-rich mud.
• The mud buried under more sediments and lithifies to form an organic shale. This prevents
its exposure to oxygen. This is done to protect the organic materials from being
decomposed by bacteria.
• The increasing pressure and temperature transform the shale into a waxy material known as
the kerogen.
• At temperatures between 90-160°C kerogen is transformed into natural gas.
11. What are the uses of Natural gas?
Compressed Natural Gas is used for generating power.
• It is used as fuels in automobiles.
• It can be used at homes for cooking.
• It is used as a starting material in chemicals and fertilizers.
12. Are fossil fuels renewable?
Fossil fuels are a non-renewable source of energy. They are found everywhere, from the air
we breathe to the water in the seas. Most of the energy used by us is obtained by the burning
of fossil fuels. These fossil fuels are used up at a faster rate. They cannot be regrown at a
scale compared to their consumption. With the increased demand for the production of
various energies, fossil fuel energy is declining. It is difficult to replace them. That is why
they are known as a non-renewable source of energy.

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13. What are the advantages and disadvantages of fossil fuel?
Advantages:
• Fossil fuels can generate a large amount of electricity at a single location.
• They can be found very easily.
• They are cost effective.
• Transportation of oil and gas can be done easily through pipelines.
• They have become safer over time.
• Despite being a finite resource, it is available in plenty.
Disadvantages
• Fossil fuels emit carbon dioxide when burnt which is a major greenhouse gas and the
primary source of pollution. This has contributed to global warming.
• They are a non-renewable resource, i.e., once used they cannot be replaced.
• Combustion of fossil fuels makes the environment more acidic. This has led to unpredictable
and negative changes in the environment.
• Harvesting of fossil fuels also causes fatal diseases among the people. For eg., the coal
miners often suffer from Black Lung Disease. The natural gas drillers are constantly
exposed to chemicals and silica which is dangerous for their health.
14. What are the effects of fossil fules on the environment?
• Carbon fuels such as wood, coal, petroleum release unburnt carbon particles in the
environment. These particles are very dangerous pollutants and cause respiratory diseases for
example asthma.
• When fuels are incompletely burnt, they release carbon monoxide gas into the atmosphere.
This gas is very dangerous as it is poisonous in nature. If we burn coal in a closed room, then
the person sleeping in that room will be killed by the action of carbon monoxide.
• The combustion of fossil fuels also releases a large amount of carbon dioxide into the
atmosphere. Carbon dioxide is a greenhouse gas which is responsible for global warming.
Global warming is a rise in the overall temperature of earth’s surface. This leads to melting of
polar caps and rise in the sea level and further results in flooding of coastal regions.
• Burning of coal and diesel releases sulphur dioxide gas. This gas is extremely corrosive and
suffocating in nature. Petrol gives off oxides of nitrogen. The oxides of sulfur and nitrogen
get dissolved in rainwater and form acids. This is known as acid rain. This water is very
harmful to plants, animals, and various monuments.
15. What is renewable energy?
Renewable energy is energy that has been derived from earth’s natural resources that are not
finite or exhaustible, such as wind and sunlight. Renewable energy is an alternative to the
traditional energy that relies on fossil fuels, and it tends to be much less harmful to the
environment.
16. What are the types of renewable energy?
Solar, Wind, Hydroelectric, Geothermal. ocean, hydrogen and biomass are the types of
renewable energy.
17. What is solar energy ?
Solar energy is derived by capturing radiant energy from sunlight and converting it into heat,
electricity, or hot water. Photovoltaic (PV) systems can convert direct sunlight into
electricity through the use of solar cells.

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18. What are the benefits and limitations of solar energy?
Benefits:
One of the benefits of solar energy is that sunlight is functionally endless. With the
technology to harvest it, there is a limitless supply of solar energy, meaning it could render
fossil fuels obsolete. Relying on solar energy rather than fossil fuels also helps us improve
public health and environmental conditions. In the long term, solar energy could also
eliminate energy costs, and in the short term, reduce your energy bills. Many federal local,
state, and federal governments also incentivize the investment in solar energy by providing
rebates or tax credits.
Current Limitations:
Although solar energy will save you money in the long run, it tends to be a significant
upfront cost and is an unrealistic expenses for most households. For personal homes,
homeowners also need to have the ample sunlight and space to arrange their solar panels,
which limits who can realistically adopt this technology at the individual level.
19. How wind energy is generated?
Wind farms capture the energy of wind flow by using turbines and converting it into
electricity. There are several forms of systems used to convert wind energy and each vary.
Commercial grade wind-powered generating systems can power many different
organizations, while single-wind turbines are used to help supplement pre-existing energy
organizations. Another form is utility-scale wind farms, which are purchased by contract or
wholesale. Technically, wind energy is a form of solar energy. The phenomenon we call
“wind” is caused by the differences in temperature in the atmosphere combined with the
rotation of Earth and the geography of the planet.
20. What are the benefits and limitations of wind energy?
Benefits:
Wind energy is a clean energy source, which means that it doesn’t pollute the air like other
forms of energy. Wind energy doesn’t produce carbon dioxide, or release any harmful
products that can cause environmental degradation or negatively affect human health like
smog, acid rain, or other heat-trapping gases.[2] Investment in wind energy technology can
also open up new avenues for jobs and job training, as the turbines on farms need to be
serviced and maintained to keep running.
Since wind farms tend to be built in rural or remote areas, they are usually far from bustling
cities where the electricity is needed most. Wind energy must be transported via transition
lines, leading to higher costs. Although wind turbines produce very little pollution, some
cities oppose them since they dominate skylines and generate noise. Wind turbines also
threaten local wildlife like birds, which are sometimes killed by striking the arms of the
turbine while flying.
21. Brief on the concept of hydroelectric energy generation.
Dams are what people most associate when it comes to hydroelectric power. Water flows
through the dam’s turbines to produce electricity, known as pumped-storage hydropower.
Run-of-river hydropower uses a channel to funnel water through rather than powering it
through a dam.

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22. What are the benefits and limitations of hydroelectric energy?
Benefits:
Hydroelectric power is very versatile and can be generated using both large scale projects,
like the Hoover Dam, and small scale projects like underwater turbines and lower dams on
small rivers and streams. Hydroelectric power does not generate pollution, and therefore is a
much more environmentally-friendly energy option for our environment.
Most U.S. hydroelectricity facilities use more energy than they are able to produce for
consumption. The storage systems may need to use fossil fuel to pump water.[3] Although
hydroelectric power does not pollute the air, it disrupts waterways and negatively affects the
animals that live in them, changing water levels, currents, and migration paths for many fish
and other freshwater ecosystems.
23. Brief on the concept of geothermal energy generation.
Geothermal heat is heat that is trapped beneath the earth’s crust from the formation of the
Earth 4.5 billion years ago and from radioactive decay. Sometimes large amounts of this heat
escapes naturally, but all at once, resulting in familiar occurrences, such as volcanic
eruptions and geysers. This heat can be captured and used to produce geothermal energy by
using steam that comes from the heated water pumping below the surface, which then rises
to the top and can be used to operate a turbine.
24. What are the benefits and limitations of geothermal energy?
Benefits:
Geothermal energy is not as common as other types of renewable energy sources, but it has
a significant potential for energy supply. Since it can be built underground, it leaves very
little footprint on land. Geothermal energy is naturally replenished and therefore does not run
a risk of depleting (on a human timescale).
Cost plays a major factor when it comes to disadvantages of geothermal energy. Not only is
it costly to build the infrastructure, but another major concern is its vulnerability to
earthquakes in certain regions of the world.
25. What is Ocean energy?
The ocean can produce two types of energy: thermal and mechanical. Ocean thermal energy
relies on warm water surface temperatures to generate energy through a variety of different
systems. Ocean mechanical energy uses the ebbs and flows of the tides to generate energy,
which is created by the earth’s rotation and gravity from the moon.
26. What are the benefits and limitations of ocean energy?
Benefits :
Unlike other forms of renewable energy, wave energy is predictable and it’s easy to estimate
the amount of energy that will be produced. Instead of relying on varying factors, such as
sun and wind, wave energy is much more consistent. This type of renewable energy is also
abundant, the most populated cities tend to be near oceans and harbors, making it easier to
harness this energy for the local population. The potential of wave energy is an astounding as
yet untapped energy resource with an estimated ability to produce 2640 TWh/yr. Just 1
TWh/yr of energy can power around 93,850 average U.S. homes with power annually, or
about twice than the number of homes that currently exist in the U.S. at present
Those who live near the ocean definitely benefit from wave energy, but those who live in

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landlocked states won’t have ready access to this energy. Another disadvantage to ocean
energy is that it can disturb the ocean’s many delicate ecosystems. Although it is a very
clean source of energy, large machinery needs to be built nearby to help capture this form
energy, which can cause disruptions to the ocean floor and the sea life that habitats it.
Another factor to consider is weather, when rough weather occurs it changes the consistency
of the waves, thus producing lower energy output when compared to normal waves without
stormy weather.
27. What are the benefits and limitations of hydrogen energy?
Benefits:
Hydrogen can be used as a clean burning fuel, which leads to less pollution and a cleaner
environment. It can also be used for fuel cells which are similar to batteries and can be used
for powering an electric motor.
Current Limitations
Since hydrogen needs energy to be produced, it is inefficient when it comes to preventing
pollution.
28. What is Biomass energy?
Bioenergy is a renewable energy derived from biomass. Biomass is organic matter that
comes from recently living plants and organisms. Using wood in your fireplace is an
example of biomass that most people are familiar with.
There are various methods used to generate energy through the use of biomass. This can be
done by burning biomass, or harnessing methane gas which is produced by the natural
decomposition of organic materials in ponds or even landfills.
29. What are the benefits and limitations of biomass energy?
Benefits:
The use of biomass in energy production creates carbon dioxide that is put into the air, but
the regeneration of plants consumes the same amount of carbon dioxide, which is said to
create a balanced atmosphere. Biomass can be used in a number of different ways in our
daily lives, not only for personal use, but businesses as well. In 2017, energy from biomass
made up about 5% of the total energy used in the U.S. This energy came from wood,
biofuels like ethanol, and energy generated from methane captured from landfills or by
burning municipal waste.
Although new plants need carbon dioxide to grow, plants take time to grow. We also don’t
yet have widespread technology that can use biomass in lieu of fossil fuels.
30. Brief on renewable energy scenario in India.
•The Indian renewable energy is ranked fourth in wind power, fifth in solar power and fifth in
renewable power installed capacity as of 2018. India ranked third in EY Renewable Energy
Country Attractive Index 2019. Installed renewable power generation capacity has increased at a
fast pace over the past few years, posting a CAGR of 19.78 per cent between FY14–18. Power
generation from renewable energy sources in India reached 101.84 billion units in FY18 and
126.76 billion units in FY19. The renewable energy will account 55 per cent of the total
installed power capacity by 2030.
•As on November 30, 2019, the installed renewable energy capacity is 84.4 GW, of which solar
and wind comprises 32.52 GW and 37.27 GW respectively. Biomass and small hydro power
constitute 9.80 GW and 4.64 GW, respectively. Overall, India added 8.62 GW of grid interactive
renewable energy capacity in FY19. The renewable energy sector’s capacity during the first
quarter of fiscal year 2019-20 is higher at 2,151 MW.

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31. Brief on renewable energy scenario at national and international level.
• It As India looks to meet its energy demand on its own, which is expected to reach 15,820
TWH by 2040, renewable energy is set to play an important role. By 2030, renewable
sources are expected to help meet 40 per cent of India’s power needs. New investments in
clean energy in the country reached US$ 11 billion in 2017. In the first half of 2018,
investments in clean energy in India reached US$ 7.4 billion.
• As of 2019, India is building a solar power plant in Rajasthan, which will be world’s
largest, with a capacity of 2,255 MW. The international equity investment in the India’s
clean energy sector was US$ 283 million in 2016, US$ 532 million in 2017 and US$ 1.02
billion in 2018. India plans to add 30 GW of renewable energy capacity along a desert on its
western border such as Gujarat and Rajasthan.
• The renewable energy space in India has become very attractive from investors’ perspective
and has received FDI inflow of US$ 8.69 billion between April 2000 and September 2019.
PART – B
1. What do you mean by fossil fuel? Explain any one in detail with its formation, benefits and
limitations.
2. Explain the formation of coal, natural gas and petroleum.
3.Explain the benefits and limitations of coal, natural gas and petroleum.
4. What do you mean by renewable energy? List its types and explain.
5. How solar energy and wind energy is generated. Explain its benefits and limitations.
6. How geothermal energy and hydroelectric energy is produced? Give its benefits and limitations.
7. Explain the concept of biomass energy production and hydrogen energy with its
benefits and limitations.
8. Why renewable energy has a sustainable development? Explain
9. Present Indian and international energy scenario of conventional and RE
sources.Explain .
10. What is fuel cell? Why it plays a vital role now-a-days? Explain.

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UNIT II
WIND ENERGY
PART - A
1. What is wind power?
Wind power is the conversion of wind energy into more useful forms, such as electricity,
using wind turbines. Wind power is used in large scale wind farms for national electrical grids
as well as in small individual turbines for providing electricity to rural residences or grid-
isolated locations.
2. Mention two important wind turbine generator installations in India.
There is a growing number of wind energy installations in states across India. some of
them are
RANK
POWER
PLANT
PRODUCER LOCATION STATE MW
1
Muppandal
windfarm
Muppandal
Wind
Kanyakumari Tamil Nadu 1500
2
Jaisalmer
Wind Park
Suzlon
Energy
Jaisalmer Rajasthan 1064
3
Brahmanvel
windfarm
Parakh Agro
Industries
Dhule Maharashtra 528
4
Dhalgaon
windfarm
Gadre Marine
Exports
Sangli Maharashtra 278
5
Vankusawade
Wind Park
Suzlon
Energy Ltd.
Satara
District.
Maharashtra 259
3. Write and explain wind power equation.
The wind power equation is expressed as follows:
P = 0.5*ρ*A*V³*E
Where: P = Power in Watts; ρ= Air Density in Kg/m³ (about 1.225Kg/m³ at sea level, less
higher up); A = Rotor Swept Area in m² = πr² (r= radius or blade length); V = Wind Speed in
m/s (cubed); E = Efficiency in percent
4. What is the type of generator used in wind power plant?
Several different types of generators which are used in wind turbines are as follows.
Asynchronous (induction) generator and synchronous generator. Squirrel cage induction

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generator (SCIG) and wound rotor induction generator (WRIG) are comes under
asynchronous generators. Wound rotor generator (WRSG) and permanent magnet generator
(PMSG) are comes under synchronous generator.
5. Define Tip speed ratio.
The Tip Speed Ratio (TSR) is an extremely important factor in wind turbine design. TSR
refers to the ratio between the wind speed and the speed of the tips of the wind turbine
blades.
TSR (λ) = Tip Speed of Blade /Wind Speed
TSR is the speed of the blade at its tip divided by the speed of the wind. For example, if the
tip of a blade is traveling at 100 mph (161 kph) and the wind speed is 20 mph (32 kph or 9
m/s), then the TSR is 5 (100 mph/20 mph). Simply put, the tip of the blade is traveling five
times faster than the speed of the wind. The Tip Speed Ratio (TSR) is used by wind turbine
designers to properly match and optimize a blade set to a particular generator (i.e. the
permanent magnet alternator).
6. State the significance of induction generator based wind power generation.
Induction Generator construction is based on the very common squirrel-cage induction
motor type machine as they are cheap, reliable, and readily available in a wide range of
electrical sizes The induction generator can be connected directly to the utility grid and
driven directly by the turbines rotor blades at variable wind speeds. For economy and
reliability many wind power turbines use induction motors as generator which are driven
through a mechanical gearbox to increase their speed of rotation, performance and
efficiency.
7. What are wind farms?
A wind farm or wind park, also called a wind power station or wind power plant, is a group
of wind turbines in the same location used to produce electricity. Wind farms vary in size
from a small number of turbines to several hundred wind turbines covering an extensive
area. Wind farms can be either onshore or offshore.
8. How the wind mills are classified?
There are different types of windmills,Which windmill to use is dependent on the
requirement.
Post Mill
One of the basic use of post mill is for grinding stone,but since it is small in size , there is
limitation in grinding. The two types of post mill, open and close post mill for open bottom
timber is exposed to the elements and for closed bottom timber are enclosed and is used for
storage.
Simple Drain Mill
As the name suggest Simple Drain Mill is used in irrigation to pump water into irrigation
canals. This small mill is designed with sails fixed in hollow pipe with archimedean screw.
This drain mill is used in extremely swampy lands
American windmill
This windmill does not require attention by the operator. Initially the windmill was build
from wood and required lot of maintenance. As time went the wood was replaced by metal
and found lot of reliability .Also there was improvement with self-oiling gearboxs and
pivoting wind wheels used by windmill. This were more efficient and maintenance free.
Tower Mill

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Tower mill are install across the sea shore facing the sea to generate energy.The sail of the
tower is similar to sail of the boats. The sails have several masts–structure above the upper
part of the boat to hold sails–are fixed to a rotating shaft.
9. What are the advantages of wind power?
 Clean & Environment friendly Fuel source:– It doesn’t pollute air like power plant
relying on combustion of fossil fuel. It does not produce atmospheric emissions that cause
acid rain or green house gases (carbon dioxide (CO2) or methane (CH4)). Noise and visual
pollution are both environmental factors, but they don’t have a negative effect on the earth,
water table or the quality of the air we breathe.
 Renewable & Sustainable:– Winds are caused by heating of atmosphere by the sun, earth
surface irregularities and the rotation of the earth. For as long as the sun shines the wind
blows, the energy produced can be harnessed and It will never run out, unlike the Earth’s
fossil fuel reserves.
 Cost Effective:– Wind energy is completely free. There’s no market for the demand and
supply of wind energy’s, It can be used by anyone and is one of the lowest price renewable
technologies available today, depending upon the wind resource and the particular project’s
financing.
 Industrial and Domestic Installation:– Wind turbines can be built on existing farms or
ranches where most of the best wind sites are found. Wind turbines uses only a fraction of
the land which causes no trouble in work for the farmers and rancher, providing landowners
with additional income paid by the owners of the wind power plants. Many landowners opt
to install smaller, less powerful wind turbines in order to provide part of a domestic
electricity supply.
 Job Creation:– Jobs have been created for the manufacture of wind turbines, the
installation and maintenance of wind turbines and also in wind energy consulting.
According to the Wind Vision Report, wind has the potential to support more than 600,000
jobs in manufacturing, installation, maintenance, and supporting services by 2050.
10. What are the disadvantages of wind power?
 Fluctuation of Wind and Good wind sites:– Wind energy has a drawback that it is not a
constant energy source. Although wind energy is sustainable and will never run out, the
wind isn’t always blowing. This can cause serious problems for wind turbine developers
who will often spend significant time and money investigating whether or not a particular
site is suitable for the generation of wind power. For a wind turbine to be efficient, the
location where it is built needs to have an adequate supply of wind energy.
 Noise and aesthetic pollution:– Wind turbines generate noise and visual pollution. A single
wind turbine can be heard from hundreds of meters away. Although steps are often taken to
site wind turbines away from dwellings. Many people like the look of wind turbines, others
do not and see them as a blot on the landscape.
 Not a profitable use of land:– Alternative uses for the land might be more highly valued
than electricity generation.
 Threat to wildlife:– Birds have been killed by flying into spinning turbine blades. However
it is believed that wind turbines pose less of a threat to wildlife than other man made
structures such as cell phone masts and radio towers. Most of the problems have been
resolved or greatly reduced through technological development or by properly siting wind
plants.

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11. Define Vertical Axis Wind Turbine (VAWT).
A vertical-axis wind turbines (VAWT) is a type of wind turbine where the main rotor shaft
is set transverse to the wind (but not necessarily vertically) while the main components are
located at the base of the turbine. This arrangement allows the generator and gearbox to be
located close to the ground, facilitating service and repair. A vertical axis wind turbine has
its axis perpendicular to the wind streamlines and vertical to the ground.
12. What is meant by pitch angle?
The angle of pitch is the angle between the main body axis and the horizon. Wind
turbines use this to adjust the rotation speed and the generated power. The pitch angle is a
potential parameter to enhance the performance of VAWTs.
13. How the turbine is rotated at variable speed?
Most wind turbines run at almost constant speed with direct grid connection. With indirect
grid connection, the wind turbine generator runs in its own AC-grid. This grid is controlled
by an inverter, so that the frequency of the alternating current in the stator of the generator
may be varied. In this way it is possible to run the turbine at variable rotational speed.
14. Draw the schematic diagram of grid integrated PMSG based WECS
15. How to assess the wind energy pattern for a particular location? Towers equipped
with anemometers, wind vanes, and temperature, pressure, and relative humidity sensors are
installed. Data from these towers must be recorded for at least one year to calculate an annually
representative wind speed frequency distribution.
16. Draw torque speed characteristics of Induction Generator (Nov/Dec 2018)
17. Why are Induction generators preferred over DC generators?
The Induction generator is preferred over DC generators for the following reasons:
 It is less expensive and more readily available than a synchronous generator.
 It does not require DC field excitation voltage
 It automatically synchronize with the power system, so its controls are simple and
less expensive

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18. How the turbine is rotated at variable speed?
Most wind turbines run at almost constant speed with direct grid connection. With indirect
grid connection, the wind turbine generator runs in its own AC-grid. This grid is controlled
by an inverter, so that the frequency of the alternating current in the stator of the generator
may be varied. In this way it is possible to run the turbine at variable rotational speed.
19. What are the advantages and disadvantages of self-excited Induction generator?
Advantages: a) It has robust construction requiring less maintenance. Also it is relatively
cheaper b) It has small size per kW output power c) It runs in parallel without hunting d) No
synchronization to the supply line is required like a synchronous generator.
Disadvantages: a)It cannot generate reactive volt amperes from the supply line to furnish
its excitation.
20. What are the main site selection consideration foe WECS?
Some of the main site selection consideration are given below:
 High annual average wind speed:
 Availability of anemometry data:
 Availability of wind V(t) Curve at the proposed site:
 Wind structure at the proposed site:
 Altitude of the proposed site:
 Terrain and its aerodynamic:
 Local Ecology.
21. What are the basic principles of wind conversion?
The wind mill works on the principle of converting Kinetic energy of the wind to
mechanical energy. We know that power is equal to energy per unit time. The energy available
is the kinetic energy of the wind. The kinetic energy of any particle is equal to one half its mass
times the square of its velocity.
22. What are the main components of WECS?
The electrical aspect of WECS can be divided into three main components, which are wind
turbine generators (WTGs), power electronic converters (PECs) and the utility grid.
23. What are some of the main points of installation?
 Dig a hole . The depth of the hole will depend upon your location and soils. Hard rock
obviously needs a smaller hole than sandy or loose soils.
 Place the anchor bolts, rebarand pour concrete.
 Unload the turbine, bolt the pole together, assemble ladder, platform, blades, wiring, tail
assembly.
 Run the wiring through the center of the pole, dig a trench, put wire in conduit, run to
building,
 Rent a crain and they will lift the pole up so it can be bolted onto the anchors. Use the crain
to lift the turbine up, screw on the blades
 Hook the electric lines to your inverter (grid tie) and attach controller, inverter and dump
load to system, turbine and breaker box.
 Some utilities require a contract, the owner will need to fill this out and deal with them, or
ask the electrician to do so.
 Turn it on.

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24. How Efficient is Wind vs Coal?
Coal fired power plans lose about 2/3 of the energy that is burned, the losses mean that only
33% of the energy in the coal becomes electricity. The electricity leaves the power plant and
depending on the efficiency of the energy "lines" and the distance, we see transmission
losses from 11% to 15%. So, let's assume a transmission loss of 13%,(making transmission
efficiency 87 percent. So the end to end efficiency of coal fired power is probably .33 x . 87
= 28.71 %.(71.29% of the energy never makes it to the consumer). Of course in the process
coal leaves coal sludge, dirty air, and a huge health problem for millions of people. Coal
also uses millions of gallons of water and leaves that water residue toxic.
An average wind turbine converts about 30% of the energy in the wind into electricity.
Line losses for locally used industrial or commercial turbiines are 1 to 2% (vs 12% line loss
for the central grid system. So .30 x .98 =29.4 So wind is more efficient, and also uses no
water, creates no pollution, and is much cheaper to build and install, with no negative
impacts upon the land, water or air.
PART B
1. Explain about wind turbine generators?
2. Explain the operating principle of Squirrel cage induction generator SCIG coupled with
wind turbine.
3. Explain the principle and operation of induction generator for wind energy conversion
system.
4. Discuss about the cooling system adopted for generators?
5. Explain the operation of DFIG based wind power generation with its characteristics and
limitations? Illustrate the independent dq control strategy adopted for dq control.
6. Explain machine capacity factor and capacity utilization factor. Explain the principle of
operation of double output induction generator system with a neat diagram.
7. Describe the power conditioning schemes used in WECS.
8. i) Explain the working and operation of PMSG with neat diagram.
ii) Draw and explain the characteristics of DFIG.
9. Using the schematic explain the working of doubly fed induction generator.
10. Distinguish between induction generator and synchronous generator .
11. Draw the equivalent circuit and show the steady state analysis of PMSG Explain the
merits and demerits of PMSG for wind energy conversion system.
12. Show the relative merits of wind energy conversion system with PMSG,SCIG and DFIG.
13. A. Explain the construction and working of PMSG and analyze the system using steady
state equation with phasor diagram.
B. A horizontal axis wind turbine has a diameter of 6m.whn the wind speed unaffected by
the turbine is 10m/s. the turbine rotates at 300 rpm and produces 5kW of mechanical power.
Find the tip speed ratio and the power coefficient.

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14. Explain the steady state equivalent circuit model and performance characteristics of
squirrel cage induction generator in detail.
15. Draw the equivalent circuit and explain the steady state analysis of induction generator.
UNIT III
SOLAR PV AND THERMAL SYSTEMS
PART - A
1. What is solar Radiation?
Solar radiation is radiant energy emitted by the sun from a nuclear fusion reaction that
creates electromagnetic energy. The spectrum of solar radiation is close to that of a black
body with a temperature of about 5800 K. About half of the radiation is in the visible short-
wave part of the electromagnetic spectrum. The other half is mostly in the near-infrared part,
with some in the ultraviolet part of the spectrum.
2. How is Solar Radiation Measured?
Solar radiation is measured in wavelengths or frequency. The energy of the wavelength
increases with the frequency and decreases with the size of the wavelength. In other words,
shorter wavelengths are more energetic than longer ones.
3. Indicate the instruments for measuring solar radiation and sun shine
There are two important types of instruments to measure solar radiation:
 Pyrheliometer is used to measure direct beam radiation at normal incidence.
 Pyranometer is used to measure total hemispherical radiation - beam plus diffuse - on a
horizontal surface.
 Photoelectric sunshine recorder: The device has two selenium photovoltaic cells, one
of which is shaded, and the other is exposed to the available solar radiation. When there
is no beam radiation, the signal output from both cells is similar, while in bright
sunshine, signal difference between the two cells is maximized. This technique can be
used to monitor the bright sunshine hours.
4. Compose the extraterrestrial and terrestrial solar radiation
Extraterrestrial solar radiation:
The extraterrestrial radiation is the solar radiation which is incident outside the earth’s
surface. The extraterrestrial radiation is 1367 watts/m2.
terrestrial solar radiation:
It is the electromagnetic radiation which originates from earth and its atmosphere.
Terrestrial Radiation is a longer wavelength which is totally infrared.
5. Write the difference between beam radiation and diffuse radiation?
Beam Radiation is the radiation which moves through the atmosphere in a straight line
without being scattered, reflected or absorbed by particles in the air.
Diffuse Radiation is the solar radiation which is being scattered, reflected or absorbed by the
particles while passing through the atmosphere but ultimately reaches the earth’s surface.
6. What are the main components of a flat plate solar collector?
The main components of a typical flat-plate solar collector are:
 Black surface - absorbent of the incident solar energy
 Glazing cover - a transparent layer that transmits radiation to the absorber, but
prevents radiative and convective heat loss from the surface
 Tubes containing heating fluid to transfer the heat from the collector

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 Support structure to protect the components and hold them in place
 Insulation covering sides and bottom of the collector to reduce heat losses
7. What are the advantages and disadvantages of a flat plate collector?
The main advantage of a flat plate collector is that the beam and diffuse components of the
solar radiation. In addition because of its simple stationary design, its construction is easy.
Moreover it does not require sun tracking and therefore it can be properly secured in a rigid
platform, and thus becomes mechanically stronger than those requiring flexibility for
tracking purpose. As the collector is installed outdoors and exposed to atmospheric
disturbances like rain, storm etc., the flat plate collector is more likely to withstand harsh
outdoor conditions.
The principal disadvantage of a flat plate collector is that because of the absence of optical
concentration, the area from which heat is lost is large. Also due to the same reason high
temperatures cannot be attained and as a result the collection efficiency is generally low.
8. What is solar collectors?
Solar Flat Plate Collector (FPC) is basically a solar thermal energy collector in which solar
energy is collected by absorbing radiation in an absorber and then transferring to a fluid.
The liquid flat plate collector is the most widely used solar collector because it is simple in
design, has no moving parts and requires little maintenance. It can be used for a variety of
applications in which temperatures ranging from 40 degree Celsius to about 100 degree
Celsius are required. Flat plate collectors have no optical concentrator and the collector area
as well as the absorber area is numerically the same. A flat plate collector is placed at a
location in a position such that its length aligns with the line of longitude and is suitably
tilted towards south if located in a northern hemisphere to have maximum collection.
9. What are the different types of solar thermal hot water technologies?
 Evacuated tube solar thermal systems
 Flat plate solar thermal systems
 Thermodynamic panels
 Solar thermal air collectors
 Solar thermal bowl collectors
 Domestic Solar Hot Water Systems
10. List out the classification of concentrating collectors.
Types of concentrating sunlight collectors:
(a) tubular absorbers with diffuse back reflector, (b) tubular absorbers with specular cusp
reflectors, (c) plane receiver with plain reflectors (V-trough), (d) multisectional
planar concentrator, (e) compound parabolic concentrator (f) parabolic trough, (g)
fresnel concentrator, (h) array reflectors (heliostats) with central receiver.
11. Differentiate flat plate collectors and concentrating collectors.
Flat plate collectors concentrating type collectors
Absorber area is large. Absorber area is small.
Concentration ratio is 1. Concentration ratio is high.
It is uses both beam and diffuse
radiation. It is uses mainly beam radiation.

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Application limited to low
temperature uses suitable for all
places as it can work in clear and
cloudy days.
High temperature application such as
power generation suitable where there
are more clear days in a year.
Simple in maintenance. Difficult in maintenance.
12. What are the types of absorber plate?
• The absorber plate can be broadly divided into three basic types depending on the extent of
wetted area relative to the absorbing surface area.
• Pipe and Fin type: Here the liquid flows only in the pipe and hence they have a
comparatively low wetted area and liquid capacity.
• Rectangular or Cylindrical Full sandwich type: In this type both the wetted area and water
capacity are high.
• Roll bond or Semi sandwich type: It is an intermediate between the above two types.
13. Examine the effects of various parameters affecting the performance of a flat plate
collector.
• A large number of parameters influence the performance of a liquid flat plate collector.
These parameters could be classified as design parameters, operational parameters,
meteorological parameters and environmental parameters. Some of the parameters are given
below:
• Selective Surface: Absorber plate surfaces which exhibit characteristics of a high value of
absorptivity for solar radiation incoming and low value emissivity for re-radiation outgoing
called selective surfaces. Such surfaces are desirable because of the net energy collection.
Some examples of selective surface layers are copper oxide, nickel black and black chrome.
• Number of covers: With the increase in the number of covers, the value of heat loss from the
absorber plate decreases. However the amount of decrease is not the same in both cases.
Maximum efficiency is obtained with one or two covers.
• Spacing: Heat loss also varies with spacing between two covers and that between the
absorber plate and first cover. The spacing at which minimum loss occurs varies with
temperature and also with tilt. Since collectors are designed to operate at different locations
with varying tilts and under varying service conditions, an optimum value of spacing is
difficult to specify. Spacing in the range from 4 to 8 cm is normally suggested. Also large
spacing reduces the collector area requirements.
• Effect of shading: The main problem associated with the use of larger spacings is that
shading of the absorber plate by the side walls of the collector casing increases. Some
shading always occurs in every collector and needs to be corrected for. In some collectors
the inside of the side walls is lined with reflecting surface in order to alleviate the effects of
shading.
• Collector tilt: Flat plate collectors are normally used in a fixed position and do not track the
sun. Therefore the tilt angle at which they are fixed is very important. Optimum tilt depends
on the application.
• Dust on the top of the cover: When a collector is deployed in a practical system, dust gets
accumulated over it, reducing the transmitted flux through the cover. This requires
continuous cleaning of the cover, which is not possible in a practical situation. Cleaning is
generally done once in a few days. For this reason it is recommended that the incident flux

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be multiplied by a correction factor which accounts for the reduction in the intensity because
of accumulation of dust.
• Fluid inlet temperature: The efficiency of the collector decreases more or less linearly with
the increasing value of fluid inlet temperature. This decrease is because of the higher
temperature level at which the collector as a whole operates when the fluid in let
temperature increases.
• Cover transmissivity: The transmissivity of the cover affects the performance of a collector
significantly. The higher the transmissivity, the better is the performance of the collector.
14. Compose the energy balance equation for solar collector.
The energy balance can also be expressed via the following key equation:
Qu=Ac[S−UL(Tplate−Tambient)]
where S is the absorbed solar radiation, UL is the total losses, Tplate is the temperature of the
absorbing plate, and Tambient is the temperature of the air, and Ac again is the area of the
collector surface.
15. Summarize the Concentration Ratio (CR).
The term "concentration ratio" is used to describe the amount of light energy concentration
achieved by a given collector. Two different definitions of concentration ratio are in general
use. They are defined briefly here so that the terms may be used.
Optical Concentration Ratio (CRo). The averaged irradiance (radiant flux) (Ir ) integrated over
the receiver area (Ar), divided by the insolation incident on the collector aperture.
Geometric Concentration Ratio (CRg). The area of the collector aperture Aa divided by the
surface area of the receiver Ar
16. What is solar charge controller sizing?
The solar charge controller is typically rated against Amperage and Voltage capacities.
Select the solar charge controller to match the voltage of PV array and batteries and then
identify which type of solar charge controller is right for the application. The solar charge
controller has enough capacity to handle the current from PV array.
17. Write the various aspects of battery sizing.
Sizing a stationary battery is important to ensure that the loads being supplied or the power
system being supported are adequately catered by the battery for the period of time (i.e.
autonomy) for which it is designed. Improper battery sizing can lead to poor autonomy times,
permanent damage to battery cells from over-discharge, low load voltages, etc.
18. Define Sensible in solar energy storage.
Sensible heat storage means shifting the temperature of a storage medium without phase
change. It is the most common simple, low-cost, and longstanding method. This storage system
exchanges the solar energy into sensible heat in a storage medium (usually solid or liquid) and
releases it when necessary. The amount of stored sensible heat in a material depends on its heat
capacity (energy density) and the thermal diffusivity (rate at which the heat can be released and
extracted) :
Q =mCp(Tf−Ti)

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where Q is the amount of heat stored, Ti is the initial temperature, Tf is the final
temperature, m is the mass of heat storage medium, and Cp is the specific heat.
19. List out the types of batteries.
Lead-acid, nickel-cadmium, lithium, zinc bromide, zinc chloride, sodium–sulfur, nickel–
hydrogen, redox and vanadium batteries.
20. What is a solar pond?
A solar pond is a pool of saltwater which collects and stores solar thermal energy. The
saltwater naturally forms a vertical salinity gradient also known as a "halocline", in which low-
salinity water floats on top of high-salinity water. The layers of salt solutions increase in
concentration (and therefore density) with depth. Below a certain depth, the solution has a
uniformly high salt concentration
21. Draw the block diagram of solar photo voltaic system.(Nov/Dec 2017, April/May 2018)
22. What is battery sizing?
(i)The battery type recommended for using in solar PV system is deep cycle battery.
Deep cycle battery is specifically designed for to be discharged to low energy level and
rapid recharged or cycle charged and discharged day after day for years. The battery should
be large enough to store sufficient energy to operate the appliances at night and cloudy days.
(ii) Sizing a stationary battery is important to ensure that the loads being supplied or
the power system being supported are adequately catered for by the battery for the period of
time (i.e. autonomy) for which it is designed. Improper battery sizing can lead to poor
autonomy times, permanent damage to battery cells from over-discharge, low load voltages,
etc.
23. What is inverter sizing?
An inverter is used in the system where AC power output is needed. The input rating
of the inverter should never be lower than the total watt of appliances. The inverter must have
the same nominal voltage as your battery. For stand-alone systems, the inverter must be large
enough to handle the total amount of Watts you will be using at one time.
24. Draw the equivalent circuit diagram of solar cell.

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25. List the applications of solar energy.
Some of the major application of solar energy are as follows: (a) Solar water heating (b) Solar
heating of buildings (c) Solar distillation (d) Solar pumping (e) Solar drying of agricultural
and animal products (f) Solar furnaces (g) Solar cooking (h) Solar electric power generation (i)
Solar thermal power production (j) Solar green houses.
Part B
1. Express solar constant with neat diagram.
2. Explain and derive expression for beam and diffuse radiation.
3. Tabulate the different types of solar energy measuring instruments.
4. Demonstrate the working of a pyrheliometer.
5. Interpret the working of a Pyranometer.
6. Describe extraterrestrial and terrestrial solar radiation.
7. Compose the instrument used for measuring total radiation.
8. Describe the classification of solar energy collectors.
9. What is flat plate collector? Explain its operation.
10. Examine the working principle of various types of concentrating solar collectors with neat
sketch.
11. Explain the principle of operation of Fresnel lens collector.
12. Demonstrate the operation of solar cell with equivalent circuit and its I-V characteristics.
13. Describe in detail about the different methods of solar storage systems.
14. What are the applications of solar ponds?
15. Working of a solar power plant-Investigate.
16. Compare solar PV system with solar thermal system.
17. Analyze about PV effect and state the advantage and disadvantage of PV Solar Energy
UNIT IV
BIOMASS ENERGY
1. What is meant by biomass energy and biomass energy resource?
Organic matters derived from biological organisms are called Biomass. The energy obtained
from biomass is called biomass energy. The raw organic matter obtained from nature for
extracting secondary energy is called biomass energy resource.
2. Classify the biomass resources.
Biomass resources are broadly classified into two categories: Biomass from cultivated
fields, crop, forest and harvested periodically. Biomass derived from waste e.g., municipal
waste, animal excreta/dung, forest waste, agricultural waste, bioprocess waste,butcharry
waste, fishery waste/processing waste etc.

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3. What do you mean by fossil fuels?
Fossil fuels (coal, petroleum oil and natural gases) are produced fromdead, buried biomass
under pressure and in absence of air during severalmillions of years. However; they are
considered separately as fossils and arenot included in the category of biomass.
4. What are the categories of scope of biomass energy?
The scope of biomass energy is of three categories. They areRural application of biomass
energyUrban and industrial applications of biomass energyBiomass as a primary source for
large scale electrical power generation.
5. Name the three categories of Biomass resources.
Bio mass resources fall into three categories:
 Biomass in its traditional solid mass (wood and agricultural residue),and
 Biomass in non-traditional form (converted into liquid fuels).
The first category is to burn the biomass directly and get the energy. In thesecond category,
the biomass is converted into ethanol and methanol to be usedas liquid fuels in engines. The
third category is to ferment the biomassanaerobically to obtain a gaseous fuel called biogas.
6. List the general principles of Energy Conservation
The general principles of Energy Conservation are:
• Recycling of waste
• Modernization of technology
• Waste heat utilization
• Proper house keeping
• Judicial use of proper types of energy
• Judicial use of proper type of fuel
• Training of manpower
• Adopting daylight saving time
• Proper operation and maintenance
• Cogeneration
7. What are the draw backs on bio gas?
• Biomass combustion produces air pollution
• Large scale production of biomass and its harvesting accelerate soil erosion and nutrient.
• Domestic use of biomass in rural areas creates air pollution
8. What are the adverse effects produced by geo thermal energy source?
• Ammonia is used as working fluid in closed cycle OTEC system. Its leakagemay
cause great damage to the ocean eco system.
• An OTEC plant displaces 4 cumec water/ MW generation. Massive flowdisturbs
thermal balance, changes salinity gradient and turbidity. It createsadverse impact on
marine environment.
• Mining of warm & cold water near the surface develops convection of sinkingcold
water. It creates a temporary variation at 40
C forcing mortality amongcoral and fines.
9. What are the applications of bio mass?
• Cooking
• Lightning
• Mechanical power
• Generation of small electricity

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10. What are the environmental concerns of geo thermal energy?
 Gases containing H2S are oxidized to SO2 and H2So4 and drops down as acidrain.
 Chemicals like sulphates, Chlorides and Carbonates of lead, boron andarsenic
pollute soil and water
 Discharge of waste hot water infects rivers and affect drinking water, farmingand
fisheries
 Noise pollution caused by exhausts is a health hazard and is controlled byusing
silencers
11. List the secondary energy forms of biomass.
The biomass can be converted to useful secondary energy forms suchas
 Heat
 Gaseous
 fuels
 Solid fuels
 Organic chemical
 Liquid fuels
12. Point out the cultivated biomass.
 The cultivated biomass (biomass from energy farms) includes:
 Sugar cane crops, sweet sorghum crops, sugar beets.
 Herbaceous crops which are non-woody plants which can be converted into biogas
or biochemical fuels.
 Cereals, potatoes and other carbohydrate fruit crops, etc. grown for producing in
feeds to the fermentation plants
 Forests crops of fast growing energy intensive trees specially grown assource of
energy.
 Aquatic crops grown in fresh water, sea water, muddy water etc., andthese crops
include submerged plants, surface plants and include seaweeds, marine algae, water
hyacinth, floating kelp etc. algae is considered to be a promising aquatic biomass
13. List out the biomass energy resources from waste.
The waste to energy processes convert organic wastes to intermediate orsecondary
energy forms such as heat, biogas, alcohol, fuels, chemicals, etc.Thewaste is
classified as
 Urban (municipal) waste
 Industrial organic waste, process waste
 Agricultural farm waste
 Rural animal waste
 Forest wasteFishery,poultry,butcharrywaste
 Animal and human excreta
14. What is meant by biogas plant?
The plant which converts biomass to biogas (methane plus carbondioxide) by the process of
anaerobic digestion is generally called a biogasplant.
15. Mention advantages of biomass energy
It is a renewable source.The energy storage is an in-built feature of it.It is an indigenous
source requiring little or no foreign exchange.The forestry and agricultural industries that

22
supply feed stocks alsoprovide substantial economic development opportunities in
ruralareas.The pollutant emissions from combustion of biomass are usuallylower than those
from fossil fuels.
16. Mention disadvantages of biomass energy
It is a dispersed and land intensive source.It is often of low energy density.It is also labour
intensive and the cost of collecting large quantities forcommercial application is significant.
Most current commercial largequantities for commercial application are significant. Most
currentcommercial applications of biomass energy, use material that has beencollected for
other reasons, such as timber and food processingresidues and urban waste.Capacity is
determines by availability of biomass and not suitable forvarying loads.Not feasible to set
up at all locations.
17. What is meant by biomass gasification?
The word gasification (or thermal gasification) implies converting solidfuel into a gaseous
fuel by thermo chemical method without leaving any solid carbonaceous residue.
18. Classify the biogas plant.
The biogas plant are classified into:
 Continuous and batch types
 The dome and drum types
19. List the factors affecting biodigestion or generation of gas.
The factors affecting biodigestion or generation of gas are:pH or the hydrogen-ion
concentrationTemperatureTotal sold content of the feed materialLoading
rateSeedingUniform feedingNutrientsType of feed stocksToxicity due end
productPressureAcid accumulation inside the digester
20. Why the biogases are mainly utilized?
Biogases are mainly utilized.The biogas can be utilized effectively forHousehold
cooking,Lighting,Operating small engines,Utilizing power for pumping water,Chaffing
fodder andGrinding flour.
21. List the Feature of continuous plant
It will produce gas continuously.It requires small digestion chambers.It needs lesser period
for digestion.It has less problems compared to batch type and it is easier inoperation.
22. List the Features of batch plant.
 The gas production in it is intermittent, depending upon the clearingof the digester.
 It needs several digesters or chambers for continuous gas production,these are fed
alternatively.
 Batch plants are good for long fibrous materials
 This plant needs addition of fementated slurry to start the digestionprocess.
 This plant is expensive and has problems comparatively; thecontinuous plant will
have less problems and will be easy foroperation.
23. Write the advantages of floating drum plant.
 It has scum troubles because solids are constantly submerged.
 In it, the danger of mixing oxygen with the gas to form anexplosive mixture is
minimized
 No problem of gas leakage

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 Constant gas pressure
24. Write the disadvantages of floating drum plant.
It has higher cost, as cost is dependent on steel and cement.Heat is lost through the metal
gas holder, hence it troubles incolder regions and periodsGas holder requires painting once
or twice a year, depending onthe humidity of the location.Flexible pipe joining the gas
holder to the main gas piperequires maintenance, as it is damaged by ultraviolet rays in
thesun. It may be twisted also, with the rotation of the drum formixing or scum removal.
25. Mention some advantages of fixed dome type plant
It has low cost compare to floating drum type, as it uses onlycement and no steel.It has no
corrosion trouble.Heat insulation is better as construction is beneath the ground.Temperature
will be constant.Cattle and human excreta and long fibrous stalks can be fed. No
maintenance.
26. Mention some disadvantages of fixed dome type plant
This type of plant needs the service of skilled masons, who arerather scarce in rural
areas.Gas production per cum of the digester volume is also less.Scum formation is a
problem as no stirring arrangement.It has variable gas pressure.
27. What are the techniques or methods of maintaining biogas production?
The methods for maintaining biogas production are Insulating the gas plantCompostingHot
water circulationUse of chemical solar energy systems
28. What is meant by cogeneration?
A procedure for generating electric power and useful heat in a singleinstallation is known as
cogeneration. Heat may be supplied in the form ofsteam, hot water or hot air. The net result
is overall increase in the efficiencyof fuel utilization.
29. Mention the types and explain the cogeneration principles
Types of cogeneration principles are:
The Topping Cycle:
Primary heat is used to generate high pressure andtemperature steam for electrical energy
generation. The discharged low gradeheat, which would otherwise be dispersed to the
environment, is utilized inan industrial process or in other ways.
The Bottoming Cycle:
Primary heat at high temperature is used directly forindustrial process requirements. The
remaining low grade heat is then usedfor electrical power generation, e.g. high temperature
cement kiln.
30. Three general types of cogeneration systems
The three general types of cogeneration principles systems are: Waste heat utilizationspace
heating and coolingwarm water in agriculturewarm water in aquaculture Total/Integrated
energy system for residential complex Total energy system (TES) for industry.
31. What is meant by incineration?
Organic matter can be burnt in presence of oxygen/air to produce heatand byproducts. This
is the well-known process called combustion. Completecombustion to ashes is called
incineration.

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32. What are the types of Gasifiers?
In down draft gasifier fuel and air move in a co current mannerIn update gasifier fuel and air
move in a counter current manner. But thebasic reaction zones remain the same.
33. What are the types of biomass resources?
 Forests
 Agricultural crops residues
 Energy crops
 Vegetable oil crops
 A quatic crop
 Animal waste
 Urban waste
 Industrial waste
34. What is Transestarification?
The Process where the raw vegetable oils are treated with alcohol(Methanol or ethanol with
a catalyst) to form methyl or ethyl esters is known as transesterfication.
35. Definition of Hydro-Electric Power Plant?
A generating station which utilizes the potential energy of water at a high level for the
generation of electrical energy is known as a hydro-electric power station.
36. Basic Principal of Hydro-Electric Power Plant.
(PE↔KE↔ME↔EE
(Potential Energy↔ Kinetic Energy ↔Mechanical Energy ↔Electrical Energy)
We know that, water is stored in dam by using rain water. This stored water contains
Potential energy, due to height or head of dam. When this water is flow towards turbine, at
that time the Kinetic Energy is Converted into Mechanical Energy. The turbine or prime
mover is mechanically coupled with generator. Whenever turbine starts to rotate with the
help of high pressure water, automatically generator starts to rotate & it produced an
electrical energy.
37. Schematic arrangement of Hydro-Electric Power Plant?
38. Classification of plants According to Nature of Load?
a. Base-Load Plants
b. Peak-Load Plants
c. Pumped Storage Hydro-Electric Power Plant for Peak Load.

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39. Classification of Hydro-Electric Power Plant
PART-B
1. Describe in detail the construction and working of various types of bio-gasplants. State the
merits and demerits of the biogas power plant.
2. Write short notes on: a) Energy from industrial and municipal waste b) Applications of Bio-
Energy.
3. What is the principle involved in the production of biogas and what is the chemical composition
of the gas? What are the various applications of this gas? Draw a sketch to illustrate the
constructional features of a typical biogas plant and describe its operation.
4. a) Compare the advantages and disadvantages of power generation from industrial wastes,
municipal waste and agricultural wastes.
b) How do we get energy from various types of wastes?
5. a) Name the various model of biogas plant.
b) What are the main problems in straw fermentation?
6. Sketch and describe any one type of bio-mass gas generation plant. Mention 4uses of the Biogas
produced.
7. How are biogas plant classified? Explain continuous and batch type plants and compare them
with regard to operation and efficiency.
8. Write short notes on a) Continuous type plant b) Flexible dome type plant
9. What is community biogas plant? What is the main problem encountered with operation?
10. List out the various points to be carried out for selection of site for a biogas plant.
11. Draw schematic diagram of biogas power plant and explain its operation. State and justify the
potential of this in satisfying energy demand of our country.
12. Write briefly on power production from agricultural waste. Draw relevant sketches and point
out the relative merits of this technique.
13. What is biomass gasification? Explain its classification with neat diagram.

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UNIT – V
OTHER ENERGY SOURCES
PART-A
1. How tidal energy is generated?
Tidal power or tidal energy is the form of hydropower that converts the energy obtained
from tides into useful forms of power, mainly electricity. Although not yet widely used, tidal
energy has the potential for future electricity generation. Tides are more predictable than the
wind and the sun.
2. Mention the four generating methods of tidal power.
Tidal stream generator, Tidal barrage, Dynamic tidal power and Tidal lagoon.
3. What is tidal stream generator?
Tidal stream generators make use of the kinetic energy of moving water to power turbines, in
a similar way to wind turbines that use the wind to power turbines. Some tidal generators can
be built into the structures of existing bridges or are entirely submersed, thus avoiding
concerns over the impact on the natural landscape. Land constrictions such as straits or inlets
can create high velocities at specific sites, which can be captured with the use of turbines.
These turbines can be horizontal, vertical, open, or ducted.
Stream energy can be used at a much higher rate than wind turbines due to water
being denser than air. Using similar technology to wind turbines converting the energy in
tidal energy is much more efficient. Close to 10 mph (about 8.6 knots in nautical terms)
ocean tidal current would have an energy output equal or greater than a 90 mph wind speed
for the same size of the turbine system.
4. What is tidal barrage?
Tidal barrages make use of the potential energy in the difference in height (or hydraulic
head) between high and low tides. When using tidal barrages to generate power, the potential
energy from a tide is seized through strategic placement of specialized dams. When the sea
level rises and the tide begins to come in, the temporary increase in tidal power is channelled
into a large basin behind the dam, holding a large amount of potential energy. With the
receding tide, this energy is then converted into mechanical energy as the water is released
through large turbines that create electrical power through the use of generators. Barrages are
essentially dams across the full width of a tidal estuary.
5. what is dynamic tidal power?
The Dynamic tidal power (or DTP) is a theoretical technology that would exploit an
interaction between potential and kinetic energies in tidal flows. It proposes that very long
dams (for example: 30–50 km length) be built from coasts straight out into the sea or ocean,
without enclosing an area. Tidal phase differences are introduced across the dam, leading to
a significant water-level differential in shallow coastal seas – featuring strong coast-parallel
oscillating tidal currents such as found in the UK, China, and Korea. Induced tides (TDP)
could extend the geographic viability of a new hydro-atmospheric concept 'LPD' (lunar pulse
drum) discovered by a Devon innovator in which a tidal 'water piston' pushes or pulls a
metered jet of air to a rotary air-actuator & generator.
6. What is Tidal lagoon?
A new tidal energy design option is to construct circular retaining walls embedded with
turbines that can capture the potential energy of tides. The created reservoirs are similar to
those of tidal barrages, except that the location is artificial and does not contain a pre-
existing ecosystem. The lagoons can also be in double (or triple) format without pumping or

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with pumping that will flatten out the power output. The pumping power could be provided
by excess to grid demand renewable energy from for example wind turbines or solar
photovoltaic arrays. Excess renewable energy rather than being curtailed could be used and
stored for a later period of time. Geographically dispersed tidal lagoons with a time delay
between peak production would also flatten out peak production providing near base load
production though at a higher cost than some other alternatives such as district heating
renewable energy storage.
7. What are the disadvantages of tidal power?
The various disadvantages of tidal power are High initial capital investment, Effect on
marine life, Difficulty in transmission of tidal electricity and Long gestation time.
8. Brief on tidal barrage flood generation.
A Tidal Barrage Flood Generation uses the energy of an incoming rising tide as it moves
towards the land. The tidal basin is emptied through sluice gates or lock gates located along
the section of the barrage and at low tide the basin are affectively empty. As the tide turns
and starts to comes in, the sluice gates are closed and the barrage holds back the rising sea
level, creating a difference in height between the levels of water on either side of the barrage
dam
9. Brief on tidal barrage Ebb Generation.
A Tidal Barrage Ebb Generation uses the energy of an outgoing or falling tide, referred to as
the “ebb tide”, as it returns back to the sea making it the opposite of the previous flood tidal
barrage scheme. At low tide, all the sluice and lock gates along the barrage are fully opened
allowing the tidal basin to fill up slowly at a rate determined by the incoming flood tide.
Tidal Barrage Ebb Generation
10. Give the diagram of power generation during ebb tide.

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11. What is Two-way Tidal Barrage Generation Scheme?
A Two-way Tidal Barrage Scheme uses the energy over parts of both the rising tide and the
falling tide to generate electricity.
12. What is wave energy?
Wave energy (or wave power) is the transport and capture of energy by ocean surface waves.
The energy captured is then used for all different kinds of useful work, including electricity
generation, water desalination, and pumping of water. Wave energy is also a type of
renewable energy and is the largest estimated global resource form of ocean energy.
13. What are the advantages and disadvantages of wave energy?
Wave energy has a lot of potential. Oceans cover 71% of the Earth, so it's very accessible.
Wave energy also has many different positive aspects. First, the energy is green. Harnessing
wave energy doesn't emit any harmful gases, and it can easily replace energies that do, such
as using fossil fuels. Second, the energy is renewable. Ultimately, the energy is caused by
heat which is emitted from the Sun, and this energy will not be disappearing any time soon.
Third, there is an incredible potential in wave energy.
However, as with any energy resource available, there are negatives as well. Wave energy
effects the environment. As with wind farms being an eye-sore, wave energy could cause
conflicts with appearance of oceans, which in turn could conflict with tourism and local
acceptance. It is also currently unclear on how harvesting wave energy affects marine life.
Because of these, installations on the coast and land facilities are held to higher restriction on
size and location for wave energy farms. Wave energy also has issues in terms of cost. It still
is in the early stages of development, so costs of wave power are still fairly high compared to
other forms of technology. Wave energy devices also require regular maintenance which
isn't cheap
14. What is Ocean thermal energy conversion (OTEC) cycle?
Ocean Thermal Energy Conversion (OTEC) is a process that can produce electricity by
using the temperature difference between deep cold ocean water and warm tropical surface
waters. OTEC plants pump large quantities of deep cold seawater and surface seawater to
run a power cycle and produce electricity. OTEC is firm power (24/7), a clean energy
source, environmentally sustainable and capable of providing massive levels of energy.
15. What is thermodynamic efficiency?
A heat engine gives greater efficiency when run with a large temperature difference. In the
oceans the temperature difference between surface and deep water is greatest in the tropics,
although still a modest 20 to 25 °C. It is therefore in the tropics that OTEC offers the
greatest possibilities.OTEC has the potential to offer global amounts of energy that are 10 to
100 times greater than other ocean energy options such as wave power. OTEC plants can
operate continuously providing a base load supply for an electrical power generation system.
16. What are the two different types of OTEC power plants?
The two different types of OTEC power plants are Closed cycle systems and open cycle
systems.
17. What is closed type OTEC system?
Closed-cycle systems use fluid with a low boiling point, such as ammonia (having a boiling
point around -33 °C at atmospheric pressure), to power a turbine to generate electricity.
Warm surface seawater is pumped through a heat exchanger to vaporize the fluid. The
expanding vapor turns the turbo-generator. Cold water, pumped through a second heat
exchanger, condenses the vapor into a liquid, which is then recycled through the system.

29
18. What is open type OTEC system?
Open-cycle OTEC uses warm surface water directly to make electricity. The warm seawater
is first pumped into a low-pressure container, which causes it to boil. In some schemes, the
expanding vapor drives a low-pressure turbine attached to an electrical generator. The vapor,
which has left its salt and other contaminants in the low-pressure container, is pure fresh
water. It is condensed into a liquid by exposure to cold temperatures from deep-ocean water.
This method produces desalinized fresh water, suitable for drinking water, irrigation or
aquaculture.
19. Explain the principle of fuel cell.
A fuel cell is a device that converts chemical potential energy (energy stored in molecular
bonds) into electrical energy. A PEM (Proton Exchange Membrane) cell uses hydrogen gas
(H2) and oxygen gas (O2) as fuel. The products of the reaction in the cell are water,
electricity, and heat.
20. What is PEM fuel cell?
Proton-exchange membrane fuel cells, also known as polymer electrolyte membrane (PEM)
fuel cells (PEMFC), are a type of fuel cell being developed mainly for transport applications,
as well as for stationary fuel-cell applications and portable fuel-cell applications. Their
distinguishing features include lower temperature/pressure ranges (50 to 100 °C) and a
special proton-conducting polymer electrolyte membrane. A proton exchange membrane
fuel cell transforms the chemical energy liberated during the electrochemical reaction of
hydrogen and oxygen to electrical energy, as opposed to the direct combustion of hydrogen
and oxygen gases to produce thermal energy.
21. What are the chemical reactions of fuel cell?
22. What is the efficiency of PEM fuel cell?
The maximal theoretical efficiency applying the Gibbs free energy equation ΔG =
−237.13 kJ/mol and using the heating value of Hydrogen (ΔH = −285.84 kJ/mol) is 83% at
298 K
The practical efficiency of a PEMs is in the range of 50–60%
23. What are the main factors to create losses in fuel cell?
The Activation losses, Ohmic losses and Mass transport losses.
24. Mention few applications of fuel cell.
Some portable fuel cell applications include laptops, cellular phones, power tools, military
equipment, battery chargers, unattended sensors, and unmanned aerial and underwater
vehicles

30
25. What do you mean by energy storage system?
Energy storage is the capture of energy produced at one time for use at a later time. A device
that stores energy is generally called an accumulator or battery. Energy comes in multiple
forms including radiation, chemical, gravitational potential, electrical potential, electricity,
elevated temperature, latent heat and kinetic. Energy storage involves converting energy
from forms that are difficult to store to more conveniently or economically storable forms.
26. Brief some types of energy storage.
Mechanical : Spring,Compressed air energy storage (CAES),Fireless locomotive
Flywheel energy storage,Solid mass gravitational,Hydraulic accumulator
Pumped-storage hydroelectricity (pumped hydroelectric storage, PHS, or pumped storage
hydropower, PSH),
Electrical, electromagnetic :Capacitor,Supercapacitor,Superconducting magnetic energy
storage (SMES, also superconducting storage coil)
27. What is hybrid energy system?
A hybrid energy system, or hybrid power, usually consists of two or more renewable energy
sources used together to provide increased system efficiency as well as greater balance in
energy supply.
28. Give examples of hybrid energy systems.
A hybrid energy system, or hybrid power, usually consists of two or more renewable
energy sources used together to provide increased system efficiency as well as greater
balance in energy supply. The basic types of hybrid energy systems are
Biomass-wind-fuel cell , Photovoltaic and wind, and Completely Renewable Hybrid Power
Plant (solar, wind, biomass, hydrogen)
29. What are the drawbacks of standalone systems?
Solar panels, are expensive to set up, and are peak output is not obtained during the night or
cloudy days. Similarly, Wind turbines can’t operate safely in high wind speeds, and low
wind speeds produce little power. Biomass plants collapse at low temperatures.
30. What is solar hybrid systems?
Solar hybrid power systems are hybrid power systems that combine solar power from a
photovoltaic system with another power generating energy source. A common type is a
photovoltaic diesel hybrid system, combining photovoltaics (PV) and diesel generators, or
diesel gensets, as PV has hardly any marginal cost and is treated with priority on the grid.
The diesel gensets are used to constantly fill in the gap between the present load and the
actual generated power by the PV system.

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PART – B
1. How tidal power is generated. Explain in detail
2. Explain in detail about barrage and non-barrage systems in tidal power generation.
3. Give the difference between wave energy and tidal energy. Explain wave energy
production in detail.
4.Explain OTEC cycle and its types in detail.
5.What is hydrogen fuel cell? Explain the principle of working.
6. Give the types of fuel cell and what is PEM fuel cell? Explain its working.
7. Explain one application of fuel cell in detail.
8. What do you mean by energy storage system? Explain its significance.
9. What do you mean by hybrid energy system? Give one example of hybrid system and
explain.
10. Explain a case study of an hybrid system.
PREPARED BY
Dr.N.ARUNKUMAR,
ASP/EEE

Renewable Energy Systems Course Overview

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