OEE351 RENEWABLE ENERGY SYSTEM

UNIT 1 SOLAR ENERGY

PART B
1. As an engineer, identify the favorable points for developing a solar thermal based power
generation project at your home town. Also share the merits and demerits of the same based on
their performance.
You must have seen wet clothes being kept in the sun to dry, do you know what energy is being
used here? It is the heat energy from the sun that makes the clothes dry. The energy radiated from the
sun can be used in many forms on Earth. The energy produced by the sun and received by Earth in one
hour is strong enough to meet global energy needs for almost a year. Solar energy exists in two forms;
humans can utilize heat and light, and both of them. Solar power can also cause chemical reactions and
generate electricity. Harnessing and using Solar energy are some of the significant ways of achieving a
clean future. As the green market is growing in many countries, Solar power’s share is also becoming
a big part of sustainable development.
If you have been asked to write a short note on solar energy or need solar energy information in
English, this article is for you. Here we will give you a solar energy definition and also equip you with
solar energy project information.
Types of Solar Panels
Solar energy can be converted into usable energy, and there are many ways of doing it to get heat,
electricity, hot water, and even cooling buildings and industrial complexes. Solar panels are equipment
that can absorb the Sun's rays and generate heat or electricity with it. The most common types of solar
panels fit into three broad categories; monocrystalline, thin-film, and polycrystalline. These solar
panels are different from each other in the way they are made, the cost involved in making them, their
performances, appearance, and the kind of installation they are best suited for. Each of these panels has
unique features and capabilities. Solar cells have semiconducting material that converts light into
electricity. Silicon is used widely as the semiconducting material in solar panels.
Based on the types of installation you require, you can choose the best fit from these three explained
below:
1. Monocrystalline and Polycrystalline Solar Panels
The Monocrystalline and Polycrystalline Solar panels have solar panels made from silicon wafers. The
wafers are assembled into rows and columns in both of these panels to form a rectangle. They are then
covered with a glass sheet and framed together. The difference between these two panels lies in the
composition of silicon used in each of them. To make a monocrystalline panel, a single pure silicon
crystal is used. For a polycrystalline panel, fragments of silicon crystals are used that are melted
together to form a mould and then cut into wafers.
2. Thin Film Solar Panels
The thin-film panels are made up of different materials and not just silicon. CdTe or Cadmium
telluride is the most common material used in making thin-film solar panels. Layers of CdTe are
placed between transparent conducting panels. These layers help capture sunlight. A top layer of glass
protects the panels. Thin-film panels could also be made from amorphous Si (a-Si) which are non-
crystalline wafers sitting on top of glass, metal, or plastic. Another popular material used in thin-film
solar panels is CIGS (Copper Indium Gallium Selenide).
Uses of Solar Energy
The use of solar energy greatly reduces long-term utility expenses like gas, electricity, etc. They are
renewable energy sources that have applications in the following sectors:
Residential Application
The residential applications comprise solar water heaters for heating water. This is achieved by
installing a photovoltaic cell on the roof of the house which collects the solar energy to warm water.
Solar energy is also used to generate electricity in residential complexes. During the daytime, solar
energy is captured in batteries and used to supply power through the day and night. These uses of solar
energy cut down energy expenditures greatly.
Industrial Applications
The thermal energy from the Sun supplies power to warehouses, offices, and industries. Even radio
and TV stations are being powered through solar energy. In aircraft, solar energy provides power to
warning lights, and lighthouses also use solar energy.
Remote Applications
Remotely situated places like schools, hospitals, buildings, and clinics can also benefit from the power
generated by solar energy. Desalination plants also use solar energy instead of electricity.
Transportation
Public transportation means like light-rails, buses, and trolleys use solar energy.
Pool Heating
During the cold season, solar energy is used to heat swimming pools.
Advantages and Disadvantages of Solar Energy Usage
Solar energy notes are not complete without talking about its miscellaneous advantages and
disadvantages.
Advantages of Solar Energy Systems
A Renewable Source of Energy
 There is no way we can run out of solar energy. Solar energy can be applied around the world
in many areas. Sunlight will be available to us for 5 billion years, as per the scientists.
Reduction in Electricity Consumption and Bills
 Since some of your energy needs will be met by solar energy, the amount of electricity you
consume from other sources would decrease, which in turn reduces your electricity bills.
Low Maintenance Costs
 All you need to do to maintain a solar system is to keep them clean. Most solar equipment from
reliable manufacturers has 20 to 25 years of warranty. There is no wear and tear on a solar
system since there are no moving parts involved in its working.
 It creates jobs as you employ solar panel manufacturers and installers, thereby helping the
economy.
 Solar systems are eco-friendly as there is no green gas emitted from them after installation.

Disadvantages of Solar Energy Systems

High Initial Cost
  The cost of purchasing a solar energy system is quite high initially. The various costs involved
are the solar panel cost, batteries, inverters, wiring, and installation.
They are Dependent on the Weather
 On a cloudy or rainy day, it is still possible to collect solar energy, but its efficiency takes a hit.
Since solar systems depend on sunlight for their power, less sunlight can bring down a solar
system's performance.
Storing Solar Energy is Expensive
 If solar energy systems are not used up right away, they need huge batteries to be stored. These
batteries are used in off the solar grid systems and have to be charged throughout the day to use
them at night. This is an expensive solution to make solar energy available during the night too.
Needs a Lot of Space
 Depending on the level of electricity you want to produce, solar panels would increase in
number. These panels take a lot of space, and some roofs might not even fit in all the solar
panels you require.
2. Discuss the construction and working of central principle of Central Receiver power plant.

 Such plants uses central tower receiver. It uses an array of plane mirrors called heliostats which
are individually controlled and tracked to reflect the solar radiations on a receiver kept on a tower
of about 500 m height. Schematic diagram of a solar tower receiver power plant is shown in
Figure D.
 The feed water in the absorber-receiver called boiler is converted into high temperature steam of
about 600°C-700°C. This steam is supplied in a conventional steam power plant coupled to an
electric generator to generate electrical power as shown.
 A thermal storage system (not shown) can be provided for use on cloudy days. A pilot plant of 50
kW was built in Itly.
 However, the plants based on the system have been commissioned in various countries in
capacities 1 MW to 10 MW. The present cost of power generation is very high, it is approximately
Rs. 4.6 Crores/MW.
3. Explain the perturb and observe MPPT algorithm with a flow chart.

Solar cells convert sun light into electricity, but have the major drawbacks of high initial cost,
low photo-conversion efficiency and intermittency. The current-voltage characteristics of the solar
cells depend on solar insolation level and temperature, which lead to the variation of the maximum
power point (MPP). Herein, to improve photovoltaic (PV) system efficiency, and increase the lifetime
of the battery, a microcontroller-based battery charge controller with maximum power point tracker
(MPPT) is designed for harvesting the maximum power available from the PV system under given
insolation and temperature conditions. Among different MPPT techniques, perturb and observe (P&O)
technique gives excellent results and thus is used. This work involves the design of MPPT charge
controller using DC/DC buck converter and microcontroller. A prototype MPPT charge controller is
tested with a 200 W PV panel and lead acid battery. The results show that the designed MPPT
controller improves the efficiency of the PV panel when compared to conventional charge controllers.
4. With the help of schematic diagram, explain the working of solar pond.
A solar pond is a body of water that collects and stores solar energy. Water warmed by the sun
expands and rises as it becomes less dense. Once it reaches the surface, the water loses its heat to the
air through convection, or evaporates, taking heat with it. The colder water, which is heavier, moves
down to replace the warm water, creating a natural convective circulation that mixes the water and
dissipates the heat. The design of solar ponds reduces either convection or evaporation in order to store
the heat collected by the pond. A solar pond can store heat much more efficiently than the body of
water of same size because the salinity prevent convectional current.
Working Principle
The solar pond works on a very simple principle. It is well-known that water or air is heated they
become lighter and rise upward. Similarly, in an ordinary pond, the sun’s rays heat the water and the
heated water from within the pond rises and reaches the top but loses the heat into the atmosphere. The
net result is that the pond water remains at the atmospheric temperature. The solar pond restricts this
tendency by dissolving salt in the bottom layer of the pond making it too heavy to rise.
5. With the help block diagram, explain the operations of standalone and grid interactive solar
PV systems.
Standalone Power System
A standalone photovoltaic system requires storage to meet the energy demand during period of low
solar irradiation and night time. The provision of cost-effective electrical energy storage remains one
of the major challenges for the development on improved PV power systems. Typically, lead acid
batteries are used to guarantee several hours to a few days of energy storage. Their reasonable cost and
general availability have resulted the widespread application of lead-acid batteries for remote are
power supplies despite their limited lifetime compared to other system components. An inverter is
used to convert DC power produced by the modules into alternating current that can plug into the
existing infrastructure to power lights, motors and other loads.

Grid Connected System

In this system, PV panels are connected to a grid through inverters without battery storage and
all excess power is fed to grid. Also during the absence of inadequate sunshine, power is maintained
from grid and thus, the battery is eliminated. The grid interactive inverter must be synchronized with
grid in terms of voltage and frequency. DC power is first converted to AC by an inverter. PV module
along with inverters as an integrator component in the junction box of the module. These are proposed
 in few MW range to meet daytime peak lead only. The capital cost of the system is slightly high for
their commercial exploitation.

6. Explain briefly the radiation measurement.

The atmosphere is made up of ions and other particles including clouds. when the incident radiation
passes through the atmosphere, some radiation penetrates and falls directly on to the panel, some
radiation diffuses in atmosphere and travels to the panel and some radiation gets reflected from the
surroundings of the panel and reaches the panel, the effect being called albedo effect. It becomes
extremely important to know the amount of energy that has reached the panel through all the paths.
There are several factors on which this energy is dependent. They are as follows :
 Latitude and longitude of the geographical location.
 Climatic conditions such as presence of clouds, water vapor etc.
 Time of the day.
 Time of the year.
 Angle of tilt.
 Collector design.
Now, let us see how we make use of this information in calculating the solar energy available at the
panel. Find the sun position with respect to the location. This is a function of latitude ,hour angle and
declination angle
Sun Position = f(Φ) ... (3.2.1)
Find the available solar energy or irradiance with no atmosphere, HO. This is a function of sun
position.
HO = f(Sun Position) ... (3.2.2)
Find the solar energy available on horizontal surface with atmospheric effects, HOA.
This is a function of HO and clearness index KT
HOA = KT HO ... (3.2.3)
Find the actual solar energy available at the panel, Ht. this is a function of HOA and the
tilt factor RD.
Ht = RD HOA ... (3.2.4)
 All the above mentioned steps can be written as an algorithm so that the moment available data is fed,
the actual solar energy available at the panel can be calculated instantly.
7. Describe the solar thermal power plant.
A solar thermal collector collects heat by absorbing sunlight. The collector receive the heat from solar
rays and give it to the heat transport fluid. Solar collector surface is designed for high absorption and
low emission. So, the utilization of solar energy requires solar collectors. These collectors are
classified into two types. They are follows,
 Non-concentrating or flat plate solar collector
 Concentrating type solar collector.
In non-concentrating collectors, the aperture area (i.e., the area that receives the solar radiation) is
roughly the same as the absorber area (i.e., the area absorbing the radiation). Concentrating collectors
have a much bigger aperture than absorber area (additional mirrors focus sunlight on the absorber) and
only harvest the direct component of sunlight.
8. Explain the Flat and liquid heating solar collector with neat sketch.
Flat Plate Solar Collector
Flat plate solar collector (Non- concentrating) are convenient particularly for space and service water
heating where temperature below about 90 °C are adequate. Flat plate can collect and absorb both
direct and diffuse solar radiation. They are consequently partially effective even on cloudy days when
there is no radiation. Flat plate collectors are m

ainly divided into

 Liquid heating collector
 Air heating
 Evacuated tubular collector.
Liquid Heating Collector
The majority of the flat plate collectors have five components :
 Transparent cover of glass, Teflon, marlex.
 Black end absorber plate usually of copper, aluminium or steel.
 Tubes, channels or passages in thermal contact with the absorber plate. They aresoldered,
brazed or clamped to the bottom of the absorber plate.
 Thermal insulation usually of foam, expanded polystyrene or glass wool typically5-10 cm
thickness.
 Tight container is to enclose above components.
9. Draw and explain solar air heater.
When an air steam is heated by back side of the collector plate, fins attached to the plate increase the
contact surface. The backside of the collector is heavily insulated with mineral wool or some other
material. Basically, air heaters are classified into following two types
 Solar air heater with non-porous absorber
 Solar air heater with porous absorber
A well-researched example of a convecting pond is the shallow solar pond. This pond consists of pure
water enclosed in a large bag that allows convection but hinders evaporation. The bag has a blackened
bottom, has foam insulation below, and two types of glazing (sheets of plastic or glass) on top. The sun
heats the water in the bag during the day. At night the hot water is pumped into a large heat storage
tank to minimize heat loss. Excessive heat loss when pumping the hot water to the storage tank has
limited the development of shallow solar ponds.

 In a non porous type, the air stream does not flow through the absorber plate.In a porous type,
the absorber include slit and expanded meyal, transpired honey comb and over-lapped glass
plate absorber. The performance of air heaters is improved by the following ways,
 Roughing the rear of the plate to promote turbulence and improve the convectiveheat transfer
coefficient, (or)
 Increasing the heat transfer surface by adding fins.
10. Explain the operation of evacuated tubular collector with neat sketch.
Evacuated tube collectors are the most common solar thermal technology in China and in the
World. They make use of a glass tube to surround the absorber with high vacuum and effectively resist
atmospheric pressure. The vacuum that surrounds the absorber greatly reduces convection and
conduction heat loss, therefore achieving greater energy conversion efficiency. The absorber can be
either metallic as in the case of flat plate collectors or being a second concentric glass tube ("Sydney
Tube"). Heat transfer fluid can flow in and out each tube or being in contact with a heat pipe reaching
 inside the tube. For the later, heat pipes transfer heat to the fluid in a heat exchanger called a
"manifold" placed transverse in respect to the tubes. The manifold is wrapped in insulation
(glasswool) and covered by a protective metal or plastic case also used for fixing to supports.

Glass-metal evacuated tubes are made with flat or curved metal absorber sheets same as those
of flat plates. These sheets are joined to pipes or heat pipes to make "fins" and placed inside a single
borosilicate glass tube. An anti-reflective coating can be deposited on the inner and outer surfaces of
such tube to improve transparency.
11. Sketch the solar concentrating collector & parabolic through collector with operation.
It is a device to collect solar energy with high intensity of solar radiation on the energy
absorbing surface. It is a special collector modified by introducing a reflecting surface between solar
radiation and absorber.It may classified as,
 Parabolic trough collector
 Minor strip reflector
 Fresnel lens collector
 Compound parabolic concentrator.
Parabolic Trough Collector
When the reflector is manufactured in the form of a trough with the parabolic crosssection, the
solar radiations gets focused along a line. An absorber pipe is placed along this line and a working
fluid water flows through it. When the focused solar radiations fall on the absorber pipe, it heats the
fluid to a high temperature. Then the heat absorbed by the working fluid is transferred to water for
producing steam.

12. Describe the mirror strip reflector & Fresnel lens collector operation with neat sketch.
Mirror strip reflector:
 In this collector, a number of plane or slightly curved mirror strips are mounted on a flat base.
The angle of the individual mirrors is arranged in such a way that they reflect solar radiation from a
specific direction on to the same focal line. The angle of the mirrors must be adjusted to allow the
change in the sun’s elevation while the focal line remains in a fixed position.

Fresnel lens collector:

In this collector, a Fresnel lens which consists of fine, linear grooves on the surface of
refracting material of optical quality on one side and flat on the other side is used. The angle of each
groove is so designed that the optical behavior of the fresnel lens is similar to that of a common lens.
The solar radiations which fall normally to the lens are refracted by the lens and are focused on a line
where the absorber tube (receiver) is placed to absorb solar radiations.
13. Describe the operation of compound parabolic concentrator.

It is a non-focusing type but the radiation from many directions is reflected towards the bottom
of the trough. Due to this the large proportion of the solar radiation including diffuse radiation entering
the trough opening is collected on a small area. An advantage of this collector is that it provides
moderately good concentration although less than a focusing collector is an east-west direction without
adjustment for sun tracking.
 A large solar thermal power plant in the range of 50 MW to 200 MW comes under central
receiver schemes. Such systems are economical in MW range for network connected plants. The high
capacity is possible due to high temperature steam in the central receiver results high efficiency of
plants.
14. List the components of central receiver system.
This system can be subdivided into the following subsystems. They are,
 Central receiver
 Heat conversion sub system
 Heat storage device
 Field of orientation mirrors.

Central receiver
The central receiver at the top of the tower has a heat absorbing surface by which the
heat-transport fluid is heated. There are two basic receiver,
 Cavity receiver type
 External receiver type.
In the cavity receiver type, the solar radiation reflected by heliostats enters through an aperture at the
bottom of the cavity whereas the absorber surfaces are on the exterior of a roughly cylindrical structure
in the external receiver type.
Heat conversion subsystem
Liquid water under pressure enters the receiver. Then the heat energy is absorbed by the water
and it leaves as superheated steam. Typical steam conditions might be a temperature of 500 ºC and
pressure of 100 atm. The steam is piped to a ground level where it drives a conventional turbine
generator system.
Heat storage device
Short term storage of heat can be provided by fire bricks, ceramic oxides, fused salts and
Sulphur. The choice of a conventional storage material is determined by its energy density, thermal
conductivity, corrosion characteristics, cost and convenience of use as well as by the operating
temperature of working fluid.
Mirrors
The flat mirror surface can be manufactured by metallization of float glass or flexible plastic
sheets. The mirror must be steerable. The glass mirrors would not be capable of withstanding the wind
load which often occurs in arid lands without any supporting structure.
15. Explain the operation working of central receiver system.
The incoming solar radiation is focused to a central receiver or a boiler mounted on a tilt tower
using thousands of plane reflectors which are steerable about two axes called heliostats. Electric power
generation using a gas turbine or gas turbine power plant working on brayton cycle. The mirrors
installed on the ground are oriented so as to reflect the direct radiation into an absorber or receiver
which is mounted at the top of a tower located near the center in the field of mirrors to produce high
temperature. Beam radiation incident in the boiler is absorbed by black pipes in which the working
 fluid is circulated and heated. The working fluid is allowed to drive a turbine thereby producing
mechanical energy. The turbine which is coupled to an alternator produces electrical energy. Suitable
heat storage is also provided to supply the heat energy during the period of cloudiness.
Advantages
1. Very high temperature is obtained. High temperature is suitable for density generation using
conventional methods such as a steam turbine.
2. It provides good efficiency. By concentrating the sunlight, this system can get better efficiency than
simple solar cells.
3. A large area can be covered by using relatively inexpensive mirrors rather than using expensive
solar cells.
4. Concentrated light can be redirected to a suitable location via, optical fiber cable.

Disadvantages
1. Concentrated collector systems required dual axis sun tracking to maintain the sunlight focus at the
collector.
2. Inability to provide power in diffused light condition. Solar cells are able to provide some output
even if the sky becomes a little bit cloudy but power output from concentrating systems drop
drastically in cloudy conditions as the diffused light cannot be concentrated passively.
16. Classify the solar pond with neat sketch.
Convecting solar ponds
A well-researched example of a convecting pond is the shallow solar pond. This pond consists of pure
water enclosed in a large bag that allows convection but hinders evaporation. The bag has a blackened
bottom, has foam insulation below, and two types
of glazing (sheets of plastic or glass) on top. The sun heats the water in the bag during the
day. At night the hot water is pumped into a large heat storage tank to minimize heat loss. Excessive
heat loss when pumping the hot water to the storage tank has limited the
development of shallow solar ponds.
Non-convecting solar ponds
The main types of non-convecting ponds is salt gradient ponds. A salt gradient pondhas three
distinct layers of brine (a mixture of salt and water) of varying concentrations.Because the density of
the brine increases with salt concentration, the most concentratedlayer forms at the bottom. The least
concentrated layer is at the surface. The saltscommonly used are sodium chloride and magnesium
chloride. A dark-colored materialusually butyl rubber lines the pond. As sunlight enters the pond, the
water and the liningabsorb the solar radiation. As a result, the water near the bottom of the pond
becomeswarm up to 93.3 °C. Even when it becomes warm, the bottom layer remains denser thanthe
upper layers, thus inhibiting convection. Pumping the brine through an external heatexchanger or an
evaporator removes the heat from this bottom layer. Another method ofheat removal is to extract heat
with a heat transfer fluid as it is pumped through a heatexchanger placed on the bottom of the pond.
Advantages
 Environment friendly energy – no pollution
 Renewable energy source
  It can be used for many purpose such as generation of electricity, heating of fluids
 No need of a separate collector for this thermal storage system
 Low maintenance costs.
17. Explain the operation of Thermal Energy Storage System with PCM.
Thermal energy storage captures heat from a hot fluid, and stores the energy for later use.
Energy storage can usually be found in renewable energy systems due to renewable energy sources
being diffuse and intermittent.
The primary components in a thermal energy storage consists of the following :
 Storage medium, heat transfer fluid, and the insulation.
 The heat transfer fluid captures heat from solar irradiation, and transfers portion of the heat to
the storage medium.
 When the heat transfer fluid goes cold after sunset, the storage medium replaces the sun as a
heat source and heats the fluid.
 Thermal Energy Storage or TES is defined as a technology that allows transfer and storage of
heat energy or energy from ice or water or cold air. This method is built into new technologies
that complement energy solutions like solar and hydro. PCM is a substance with a high heat of
fusion which, melting and solidifying at a certain temperature, is capable of storing and
releasing large amounts of energy. Heat is absorbed or released when the material changes
from solid to liquid and vice versa.
Working principle
 The water is passed through the parabolic reflector from the inlet.
 The parabolic reflector is heated by absorbing solar energy from sun using parabolic collector.
 It is designed in such a way that they are liquid flowing through the tubes get heated by
absorbing heat from source which is integral within it.
 The heated water is passed through the outlet tank.
 The Phase Changing Materials (PCM) are kept inside the tank.

18. Explain briefly the Solar Photovoltaic (PV) Power Systems.

Solar PV system convert solar energy directly into electrical energy. The basic conversion
device is known as solar photovoltaic cell. Energy conversion device which are used to convert into
electricity by the use of photovoltaic effect are called solar cell. When semiconductor materials are
exposed to light, the some of the photons of light ray are absorbed by the semiconductor crystal which
causes a significant number of free electrons in the crystal. This is the basic reason for producing
electricity due to photovoltaic effect. Photovoltaic cell is the basic unit of the system where the
photovoltaic effect Is utilized to produce electricity from light energy. Silicon is the most widely used
semiconductor material for constructing the photovoltaic cell.
Working of Solar PV
Solar cell consists of a PN junction formed in a semiconductor material similar to a diode. Fig.
3.7.1 shows a schematic diagram of the cross section through a crystalline solar cell. It consists of a
 0.2–0.3 mm thick monocrystalline or polycrystalline silicon wafer having two layers with different
electrical properties formed by ‘‘doping’’ it with other impurities (e.g., boron and phosphorus). An
electric field is established at the junction between the negatively doped (using phosphorus atoms) and
the positively doped (using boron atoms) silicon layers. If light is incident on the solar cell, the energy
from the light (photons) creates free charge carriers, which are separated by the electrical field. An
electrical voltage is generated at the external contacts, so that current can flow when a load is
connected. The photocurrent(Iph), which is internally generated in the solar cell, is proportional to the
radiation intensity.

19. Describe the solar PV generation with neat sketch.

A basic photovoltaic system integrated with the utility grid. It contains of the following elements,
 Solar array
 Blocking diode
 Battery storage
 Inverter/converter
 Switches and circuit breakers.
Solar array
Solar array is large or small element which converts the isolation into useful DC electrical power.
Blocking diode
It lets the array generated power flow only towards the battery or grid. Without a blocking, the battery
would discharge back through the solar array at the time of no isolation.
Battery storage
It is used to store the solar energy.
Inverter/ converter
It converts the battery bus-voltage to AC of frequency and phase to match to integrate with the utility
grid. It contains a suitable output step up transformer and power correction circuits.
Switches and circuit breakers
It permits isolating parts of the system as the battery.
20. Explain the operation of standalone power system.
Charge controllers are used to regulate the charge transfer and prevent the battery from being
excessively charged and discharged. Blocking diodes in series with PV modules are used to prevent
the batteries from being discharged through PV cells at night where there is no sun available to
generate energy. Those blocking diodes also protect the battery from short circuit. In a solar power
system consisting of more than one string connected in parallel if a short - circuit occurs in one of the
strings and the blocking diode prevents the other PV strings from discharged through the short-
circuited string. The output of the array after converting to AC is fed to loads and the excess of load
requirement is used to charge the battery. When the sun is not available, the battery supplies the load
through the inverter.
 UNIT 2-SOLAR SYSTEM
21. Explain the operation of Grid connected power system.

In this system, PV panels are connected to a grid through inverters without battery storage and
all excess power is fed to grid. Also during the absence of inadequate sunshine, power is maintained
from grid and thus, the battery is eliminated. The grid interactive inverter must be synchronized with
grid in terms of voltage and frequency. DC power is first converted to AC by an inverter. PV module
along with inverters as an integrator component in the junction box of the module. These are proposed
in few MW range to meet daytime peak lead only. The capital cost of the system is slightly high for
their commercial exploitation.
22. Explain the operation of hybrid power system.
Conventional power systems used in remote area often based on manually controlled diesel
generators operating continuously or for a few hours. Extended operation of diesel generators at low
load levels significantly increase maintenance cost and reduce their useful life. Renewable energy
sources such as PV can be added to remote area power systems using diesel and other fossil fuel
powered generators to provide 24-hour power
economically and efficiently.
Advantages
 It has no moving parts.
 It has no pollution.
 It has wide power handling capacity.
 It has long effective life.
 It is highly reliable.
 Power to weight ratio is high.
 It can be used with or without sun tracking.
Disadvantages
 The system needs high cost.
23. Describe the solar cell concept.

Solar power or electricity from the solar system is obtained from solar photovoltaic (PV) cells. The PV
cell made from the silicon material, a semiconducting material. It is called the photovoltaic (PV) cells
because in Greek language phos means light, and volt, measurement unit named for Alessandro Volta
(1745-1827), a pioneer in the study of electricity. Therefore, it's called photovoltaic. Solar cells are
small devices, which can convert sunlight into electricity. One cell has 0.5 to 0.6 volt. in series to get
higher voltage.
24. Describe the importance of renewable energy sources.
The most significant feature of renewable energy is its availability is plenty in nature. It is infinite.
Renewable energy sources are hygienic sources of energy that have a much lesser negative
environmental impact than conventional fossil fuel energy technologies.
 Most renewable energy investments are spent on materials and personnel to build and maintain
the facilities, rather than on costly energy imports. With technological advancements in digital
communication, people have now become aware of the demerits of burning fossil fuels.
 Renewable energy is the need of the hour. Its clean and sustainable nature has compelled the
human beings to think seriously about it. Scientists and engineers, around the world, are
continuously working and doing research in this domain. They are finding new ways to use
these sources of energy effectively and efficiently.
  Global warming is a huge hazard which is being caused by burning of coal, oil and natural gas.
It is very harmful for the planet and the living beings on it. Moreover, fossil fuels cause many
unfortunate mishaps in the past. To put an end to this apocalypse; we must resort to renewable
sources. This is because they are cleaner and do not produce poisonous harmful gases.
 Renewable energy is key in achieving these international goals. Using renewable (as oppose to
fossil fuels) brings other advantages and opportunities, ranging from environmental to socio-
economic and political.
 Energy and sustainability had become an important aspect and current issue around the global.
Energy is an important and essential commodity in contributing towards the economic growth
of the country.
 Natural resources are one of the resources that human consume to generate the energy. But the
most important issue is how technology can contribute to generating the solution maintaining
sustainability. Energy production, primary and end-use of energy and quality of energy are the
important aspect while discussing
25. Explain briefly sustainable design and development.
Sustainable energy is the practice of using energy in a way that "meets the needs of the present
without compromising the ability of future generations to meet their own needs. The concept of
sustainable development was described by the World Commission on Environment and Development
in the year 1987.
The commission described four key elements of sustainability with respect to energy :
 The ability to increase the supply of energy to meet growing human needs.
 Energy efficiency and conservation.
 Public health and safety.
 Protection of the biosphere and prevention of more localized forms of pollution.
 Various definitions of sustainable energy have been offered since then which are also based on
the three pillars of sustainable development, namely environment, economy, and society.
 Environmental criteria include greenhouse gas emissions, impact on biodiversity, and the
production of hazardous waste and toxic emissions.
 Economic criteria include the cost of energy, whether energy is delivered to users with high
reliability, and effects on jobs associated with energy production.
 UNIT III WIND ENERGY

PART-B

1. Draw the line diagram of various types of wind mill blades and write their advantages
and disadvantages. [APR/ MAY 23]

HORIZONTAL AXIS WIND TURBINE

 Single Blade
 Double Blade
 Triple Blade
 Farm wind mill multi Blade
 Upwind
 Down wing
VERTICAL AXIS WIND TURBINE
 Savonious
 Gyro mill
 Darrieus mill
 Magnus
 Vortex

2. In a practical site, the atmospheric pressure is 1.01325 bar and temperature is 25°C.
The wind is available at 9 m / sec. Evaluate the following.
(i) Power density available in the site.
(ii) Maximum power density possible.
(iii) Obtainable power density assuming the overall efficiency is 35%.
(iv) Power density of the windmill if the diameter is 50 m and
(v) Axial thrust force action on the wind mill blade. [APR/ MAY 23]
3. Compare vertical and horizontal axis wind turbine. [NOV/DEC 22]

Horizontal Axis Wind Turbine Vertical Axis Wind Turbine

Axis of rotation is parallel to the air stream Axis of rotation is perpendicular to the air stream.
Yaw control mechanism is required to adjust the No orientation of rotor is required; these turbines can
rotor around a vertical axis to keep it facing the generate power with the wind coming from any
wind. direction.
The heavy nacelle containing the gearbox, The nacelle is not required because the gearbox,
generator, etc. is mounted at the top of the tower, generator, etc., are located at the ground, thus the
thus the design and installation is complex. design and installation are simple.
The power coefficient and tip speed ratio are
The power coefficient and tip speed ratio are high.
considerably low.
4. Generalized the factor to be considered for the sitting to install the wind power plant.
[NOV/DEC 22]

Some of the main site selection consideration are given below:

1. High annual average wind speed:
2. Availability of anemometry data:
3. Availability of wind V(t) Curve at the proposed site:
4. Wind structure at the proposed site:
5. Altitude of the proposed site:
6. Terrain and its aerodynamic:
7. Local Ecology
8. Distance to road or railways:
9. Nearness of site to local centre/users:
10. Nature of ground:
11. Favourable land cost
5. How energy from wind can be extracted? Explain the progress by using suitable
diagram. [NOV/DEC 21]
 Before 1920-wind turbine only used for mechanical usage such as cutting and grinding
purpose.
 After 1920-wind turbine used for generating electricity.
 1930- local wind mill used for remote area location.
 1970-oil shortage so wind energy used instead of fossil fuel based power plant.
 1980-increase wind generation in California compare to other state.

6. Describe the working of wind power system and its components with a neat schematic
diagram. [NOV/DEC 21]
 Wind is simple in air motion. It caused by uneven heating of earth surface by the sun.
 Earth surface made up of different types of land such as land, water source and vegetation.
 During the day time-air heat up above the land and rise the air and form the wind
 During the night time-its reverse operation.
 Today wind energy is mainly used for generating electricity.
 Its renewable energy source and does not emit the emission.

7. Explain the types of wind energy?

 Utility scale wind-100kw to several mW electricity given to the power grid.
 Distributed wind-below 100kw for home, office.
 Offshore wind-provided on large bodies of water.
 Temperature difference according to the amount of heat liberated by the sun.
 Uneven heating of the earth surface and atmo9sphere.
 Balance between the warm and cold sir is constantly changing.

8. What are the cause of wind energy formation?

 Wind caused by uneven heating the atmosphere by the sun.
 The irregular of the earth surface.
 The rotation of the earth.
 The flow pattern of the wind is modified by the earth terrain, water bodies and vegetative
cover
 Temperature difference according to the amount of heat liberated by the sun.
 Uneven heating of the earth surface and atmo9sphere.
 Balance between the warm and cold sir is constantly changing.

9. Explain the creation of wind energy?

 Temperature difference according to the amount of heat liberated by the sun.
 Uneven heating of the earth surface and atmo9sphere.
 Balance between the warm and cold sir is constantly changing.
 Wind caused by uneven heating the atmosphere by the sun.
 The irregular of the earth surface.
 The rotation of the earth.
10. Briefly discuss about the wind power and wind farm.
 Wind turbine to make electricity.
 Wind mill to make mechanical power.
 Wind pump for water pumping.
 A wind farm is group od wind turbine.
 It delivery the more output electrical energy.

11. List the major wind farm in tamilnadu.

 Kanyakumari-33MW
 Kayathar.-30MW
 Chennai-15 MW
 Perungudi-12 MW
 Muppandal-10 MW

12. Discuss about the fundamental of wind energy.

 It reduce the global warming, environmental pollution, and energy security.
 Renewable source such as solar energy, wind energy, bio gas,etc.
 Wind is moving air it caused by uneven heating of earth surface.
 Hot air above the land rise up and cool air above the water down to form circular motion this
cycle is repeated.

13. Explain the basic parts of wind turbine.

 Rotor with blade arrangement.
 Generator.
 Braking system.
 Control system
 Yaw control mechanism.
 Pitch control mechanism.
 Tower.
 Foundation.
 Anemometr.

14. How controlling the output frequency of wind turbine.

 Variable frequency AC from wind turbine.
 Rectifier changes (AC to DC).
 Capacitor and inductor filter (get pure DC).
 Inverter changes (DC to AC).
 Transformer (increase voltage).
 Constant frequency ac power.

15. What are the size and application of wind turbine.

According to size and application.
Small (10KW)
Homes
 farms
Medium (10-250KW)
Village power
Hybrid system
Large (660KW-2MW)
Community wind.
Distributed wind.
16. What are the advantage and disadvantage of wind turbine.
Advantage:
 No pollution.
 Low price renewable enrgy source.
 It does not produce emission.
 The wind blow all time day and as well as night time.
 Wind power lis low cost.
 Its clean energy.
 Remote area location is very useful

Disadvantage:

 Noise disturbance.
 Threat to wildlife.
 Large scale construction and large are required.
 Strength of wind is not constant.

17. What are the system components of wind turbine.

 Foundation.
 Tower.
 Nacelle.
 Generator.
 Generator shaft.
 Drive shaft.
 High speed shaft
 Low speed shaft.
 Gear box

18. Explain about the wind energy systems.

 The kinetic energy is converted ibto the mechanical energy by using wind turbine.
 The wind turbine is directly connected to the generator.
 The mechanical energy is converted into the electrical energy by using generator.
 There are two types of wind energy system:
 Horizontal axis wind turbine.
 Vertical axis wind turbine.
19. What are the factor affecting the cost of wind power?
 Reliability.
 Cost of material.
 Geographical location of wind turbine.
 Effect of winter on wind turbine.
 Wind power PTC,subsidies, and rebates.

20. What are the site selection of wind farms?

 Technical consideration.
• Wind speed.
• Turbine size
• Grid structure
 Economic consideration.
 Capital cost
 land cost
 Maintenance cost
 Environmental consideration.
 Visual impact.
 Noise impact.
 Social consideration.
 Regulatory boundaries.
 Land use
UN EXPECTED QUESTION
21. Discuss the benefits of system performance of wind turbine.
 An existing machine can increase its annual output.
 A smaller machine can replace a larger machine at a low cost.
 Shipping cost, erection cost, will be less.
 Total elimination of transformer, inverter, gear box.
 Low operation and maintenance cost.
 Technically simpler machine.
 Program for seasonal condition.
 Power down feature.
 Off the shelf components.
 Low cost generator.

22. Explain about the utilization of biogas as energy source.

 Utilization for cooking.
 Utilization for lighting.
 Utilization for refrigerator.
 Utilization for biogas fuelled engines.

23. Briefly discuss about the IC engine operation and economic aspects.
 Electricity generation.
 Economic aspects.
 Benefit to the environmental.
 Benefits of biogas to agriculture.
 Biogas and forest.
 Benefits of biogas to women.

24. What are the performance of wind turbine and factor affecting the wind turbine?
 Wind prediction.
 Variable speed transmission.
 Constant speed generator.
 Sophisticated programming of load and RPM.
 Factors affect wind turbine:
 Blade strength, weight and performance of wind turbine.
 Economic characteristics of wind turbine.

25. Explain about the principle of biomass conversion.

Biomass is a bio logical material derived from living organism.
It directly convert combustion to produce heat , indirectly after converting it to various form of
biofuel.
Different method of conversion of biomass:
Thermal, chemical, and biochemical methods.
The extraction of energy from biomass:
Solid biomass.
Biogas and.
Liquid biofuels.
 UNIT IV
BIOMASS ENERGY

1. (i) Explain with neat sketch of various methods of energy harvesting technique in geo
thermal source. List out their merits and demerits. (April/ May 2023)
What is geothermal energy? Explain the working principle of a geothermal power plant with
the help of a neat sketch. (Nov/Dec 2021)

There is a rise in the temperature of Earth from the surface to the core. This gradual shift in its
temperature is called the geothermal gradient, which is around 25° C per 1 kilometre of depth in the
majority parts of the world. Under the hottest part of the Earth's core, the vast majority of heat
emanates from the continual decay of different radioactive isotopes. Temperatures in this part of the
Earth's surface rises above 5,000° C that helps to create this source of energy. The heat always
radiates outside and warms the water, rocks, gas, and different geological elements.
When rock formations in the mantle and lower crust of Earth heat to roughly 700 to 1,300° C, they
can turn into magma. It's a molten rock penetrated by gas as well as gas bubbles that sometimes
erupts as lava to the Earth's surface. This magma melts nearby rocks and underground aquifers that
emit out geothermal energy on the Earth's surface in diverse forms throughout the world. The source
of geothermal energy is lava, geysers, steam vents, or dry heat. The heat can be seized and utilised
directly for heating purposes, whereas the application of geothermal energy steam is to generate
electricity.
Uses of Geothermal Energy
More than 20 countries are utilising this natural energy today. Amongst them, the USA is the
biggest generator of geothermal energy in the world with the most extensive geothermal field. We
can divide the uses of geothermal energy into three categories:
Direct Uses Of Geothermal Energy
It is the most common application of geothermal energy in which low-temperature
geothermal resources are used, such as natural hot springs, therapeutic spas, aquaculture ponds, and
greenhouses. Also, it is an excellent source for cooking, milk pasteurisation, drying fruit, vegetables,
and timber in industries.
Electric Power Generation
One of the most popular uses of geothermal energy is to produce electricity. Since most of the
geothermal energy from the Earth's crust can't bubble out as magma, steam, or water, it's extracted by
building thermal plants. This renewable source of energy generates through three different
techniques, i.e., dry steam, binary and flash.
 After digging wells one or two miles deep into the ground, power produces from geothermal
energy by entering the hot water and steam into it. This generated energy runs turbines connected to
electricity generators.
The USA, Indonesia, and the Philippines are successfully using this energy. Apart from these
countries, Kenya and Turkey are also efficiently establishing geothermal energy plants.
(Geothermal energy extracted from Earth through dry steam technique. Steam from hot water is
converted into power using the turbine and generator then injected back into the Earth's surface after
cooling down)
Geothermal Heat Pumps
Geothermal heat pumps or GHPs function by using geothermal energy found within 300
metres of Earth's surface, which has a moderate temperature. This GHP system is made with a pump
and a loop of pipes implanted in the ground that transfers heat energy between the surface air and
Earth. The GHPs help draws warm air from a building to cool them down during summer. On the
contrary, it warms the buildings in the winter season.
Advantages of Geothermal Energy
 There are plenty of hot springs and natural pools across the world that emit geothermal
energy. The water from such a natural source of geothermal energy is commonly used for
bathing, warmth, and cooking.
 GHPs powered heating, and air-conditioning systems are more efficient as they use 25 to 50%
less electricity than conventional systems. Ultimately, there is a decrease in greenhouse gas
emissions as well.
 Many buildings, sidewalks, and parking lots are heated using geothermal energy.
 Also, known as a green source of energy because it does not release hazardous greenhouse
gases. Thus, it is safe for both environmental and human health.
 Geothermal energy systems can adjust to various conditions.
 One of the best advantages of geothermal energy is that cold countries use geothermal energy
to heat greenhouses or heat water for irrigation.
 Iceland mostly uses geothermal energy to heat buildings and water using magma and molten
rock resources.
 It is a renewable, carbon-free, and sustainable source of energy. The Earth will continuously
transmit heat from its core for billions of years.
Disadvantages of Geothermal Energy
 Geothermal energy emits sulphur dioxide and hydrogen sulphide.
 The regions that consist of geothermal plants often experience minor seismic activity.
 The power plants can also damage roadways, buildings, pipelines, and natural drainage
systems.
 Land subsidence can also occur in case geothermal energy yielders fail to inject back the
extracted water from the reservoir into the Earth.
 The method of drilling geothermal plants deep under the Earth proves to be dangerous for the
people involved in the process that is one of the greatest disadvantages of geothermal energy.
 It is hard for developing countries to build thermal plants because of their high initial cost.
 Geothermal energy emits out at a gradual speed from the Earth's mantle.
 The construction of geothermal sites may be hazardous for the environment as the process
may discharge highly toxic gases.

(ii) Elaborate the site selection process for Micro hydro power plant erection. (April/ May 2023)
The following factors must be considered while on site selection for hydroelectric power plant.
 Water availability
 Water storage
 Water head
 Accessibility of the site
 Distance from load centre
 Environment Aspects
2. Explain any one type of gasifier with neat line diagram. Mention the merits and demerits of
the same. (April/ May 2023)
Gasification is a process that converts the fossil fuel or organic waste into gases. These gases
include Hydrogen (H2), Carbon Dioxide (CO2) and Carbon Monoxide (CO). The process involves
oxidation and reduction of the organic matter at high temperatures. The product is a gas mixture/fuel
called producer gas or synthesis gas. This product is combustible at higher temperatures, hence is more
efficient than the combustion of the original fuels. This process is extensively used to generate the
electricity in varied industries.
Types of Gasifier
On the basis of the flow of oxygen in the gasifier equipment, categorization of gasifier can be done
into further types. The primary classification involves – Updraught, Downdraught and Cross-
draught.
The choice and type of the gasifier depends on the
 Type of fuel
 Size of fuel
 Solid Wastes
 Form
 Moisture and ash content
 The flow of oxygen in the Gasifier
Updraught Gasifier
Also called the countercurrent gasifier, this is the simplest and the oldest one. In the upper part of the
gasifier, the pyrolysis occurs due to the heat transfer. While in the lower part, combustion takes place
followed by reduction. This takes place at a potentially higher temperature. During the process, the tars
and volatiles are carried in the gas stream. The ashes and other residues are also removed from the
bottom of this reactor.
Advantages:
 The major advantage is its simplicity.
 The internal heat exchange and high charcoal release gases at low temperatures.
 High gasifier equipment efficiency.
Drawbacks:
 Explosive situations may arise if there is channelling in the equipment. This is can be the cause
for oxygen breakthrough. This is extremely dangerous and is one of the major drawbacks of
this gasifier.
 Tars can be burnt if the gas is used for applications with some direct heat exposure.
 The disposal of condensates that contain tar can also be a minor problem.
Downdraught Gasifier
This serves as a solution to the problem of tar in the gas stream. This designed gasifier is also
called the co-current one. Here, the air/oxygen is introduced above the oxidation zone. The produced
producer gas or synthetic gas is removed from the bottom thus, making the gas and fuel move in the
same direction. Due to the fuel and gases in motion, the distilled products and acid are converted into
gases like Methane, Carbon Monoxide, Hydrogen and Carbon Dioxide.
Advantages:
 The product obtained is the tar-free gas that can be used for engine applications.
 Due to the presence of a lower level of organic components in the condensate, these gasifiers
suffer less from any environment sort of objections.
Drawbacks:
 Unable to operate on the majority of unprocessed fuels.
 They suffer from problems due to fuels with high ash content.
 There is a lack of internal heat exchange in comparison to the updraught gasifier.
 Less efficiency due to the low heating value of gases.
 The gasifier can turn inefficient under high uniform temperatures and may become impractical
for power ranges above 350 kW.
Cross-draught gasifier
Cross-draught gasifiers are used for the gasification of charcoal. This takes place at extremely
high temperatures in the zone where oxidation occurs.
Advantages:
 The installations can be economically feasible below power range of 10kW.
 It can be operated on a very small scale.
 These type of gasifiers can be a fit for the small engines.
Disadvantages:
 It needs a consequent supply of high-quality charcoal.
 These gasifiers have minimal tar-converting capabilities.

3. Discuss the biomass conversion technologies and explain any one in detail. (Nov/Dec 2022)
With the help of neat sketch, explain the working of floating drum type biogas plant.
(Nov/Dec 2021)

The KVIC biogas plant was the first application of biogas plant in India which was developed
in 1954, after which all other types of biogas plants were introduced. It is known as KVIC plant
because, the application of the KVIC plant in the villages was started in year 1962 by Khadi and
Village IndustryCommission, Bombay.

The available designs are varies in the size from 1 m3 to 140 m3 gas per day. The main
design principle is that, it consists of a digester or pit for fermentation and a floating drum for the
collection of gas. Digester is 3.5 to 6.5 m in depth and 1.2 to 1.6 m in diameter. There is a partition
wall in center, which divides the digester vertically and submerges the slurry when it is full. The
digester is connected to the inlet and outlet by two pipes. Through the inlet, the dung is mixed with
water (4:5) and loaded into the digester. The fermented material will flow out through outlet pipe.
The outlet is generally connected to a compost pit. The gas generation takes place slowly in two
stages. In the first stage, the complex organic substances contained in the waste are acted upon by a
certain kind of bacteria, called acid formers and broken up into small-chain simple acids. In the
second stage, these acids are acted upon by another kind of bacteria, called methane formers and
produce methane and carbon dioxide.
4. Describe the various components and working of hydroelectric system. (Nov/Dec 2022)

Components of Hydro electric power plant:

 Reservoir
 Dam
 Surge tank
 Valve house
 Penstock
 Turbine
 Draft tube
 Power house
 Generator
Working:
To produce hydroelectricity, three things must be present; moving water, a turbine, and a
generator. Hydropower stations are designed to harness the kinetic energy from moving water.
Ideally, they are factories that convert the energy of falling water into the flow of electrons,
commonly known as electricity. In most scenarios, a dam is constructed across a river to elevate the
water level and offer the fall needed to develop a driving force. The falling water is then channeled to
a turbine wheel at a lower level. The flowing water turns a turbine wheel that is connected to a
generator. The generator has a rotor, which is turned by the turbine. The turning of the generator
rotor produces electricity.
The functioning of a generator is pegged on the principles revealed by Faraday. His discovery
states that when a magnet is moved past a conductor, it triggers electrons to flow. In a large-scale
hydroelectric generator, electromagnets are created by circulating direct current via wire loops that
are wrapped around heaps of magnetic steel laminations known as field poles. The field poles are
mounted on the perimeter of the rotor. The rotor is connected to the turbine shaft and spins at a set
speed. When the rotor spins, it triggers the electromagnets (field poles) to go beyond the conductors
mounted in the stator, causing electrons (electricity) to flow and a voltage to occur at the output
terminals of the generator.
The electricity produced is then stepped up in voltage through the hydroelectric power station
transformers and sent across transmission lines. The used water having performed its intended
purpose is channeled out of the power generation station to the mainstream of the river to continue
the cycle of power generation.
5. List the various advantages and disadvantages of hydro – electric power station.
Advantages:
 Once a dam is constructed, electricity can be produced at a constant rate.
 If electricity is not needed, the sluice gates can be shut, stopping electricity generation. The
water can be saved for use another time when electricity demand is high.
 Dams are designed to last many decades and so can contribute to the generation of
electricity for many years / decades.
 The lake that forms behind the dam can be used for water sports and leisure / pleasure
activities. Often large dams become tourist attractions in their own right.
 The lake's water can be used for irrigation purposes.
 The build up of water in the lake means that energy can be stored until needed, when the
water is released to produce electricity.
 When in use, electricity produced by dam systems do not produce green house gases. They
do not pollute the atmosphere.

Disadvantages:

 Dams are extremely expensive to build and must be built to a very high standard.
 The high cost of dam construction means that they must operate for many decades to become
profitable.
 The flooding of large areas of land means that the natural environment is destroyed.
 People living in villages and towns that are in the valley to be flooded, must move out. This
means that they lose their farms and businesses. In some countries, people are forcibly
removed so that hydro-power schemes can go ahead.
 The building of large dams can cause serious geological damage. For example, the building of
the Hoover Dam in the USA triggered a number of earth quakes and has depressed the earth’s
surface at its location.
 Although modern planning and design of dams is good, in the past old dams have been known
to be breached (the dam gives under the weight of water in the lake). This has led to deaths
and flooding.
7. Dams built blocking the progress of a river in one country usually means that the water
supply from the same river in the following country is out of their control. This can lead to
serious problems between neighboring countries.
 Building a large dam alters the natural water table level. For example, the building of the
Aswan Dam in Egypt has altered the level of the water table. This is slowly leading to
damage of many of its ancient monuments as salts and destructive minerals are deposited in
the stone work from ‘rising damp’ caused by the changing water table level.
6. What is low head hydro power plant? Explain its function.
Though there is no rule regarding water head height but below 30 meters is considered as low
head hydro power plant.
FUNCTION:
When watching a river roll by, it's hard to imagine the force it's carrying. If you have ever
been white-water rafting, then you've felt a small part of the river's power. White-water rapids are
created as a river, carrying a large amount of water downhill, bottlenecks through a narrow
passageway. As the river is forced through this opening, its flow quickens. Floods are another
example of how much force a tremendous volume of water can have.
 Hydropower plants harness water's energy and use simple mechanics to convert that energy
into electricity. Hydropower plants are actually based on rather simple concept water flowing through
a dam turns a turbine, which turns a generator.

7. Show and explain the different layers in the cross section of the earth. Also explain the
hydrothermal base geothermal source.

Geothermal energy is produced by the heat of Earth’s molten interior. This energy is
harnessed to generateelectricity when water is injected deep underground and returns as steam (or hot
water, which is later converted to steam) to drive a turbine on an electric power generator.
Moderate- to low-temperature geothermal resources are also used to heat buildings directly
and to provide space heating through district heating systems in which heat is distributed to
residences and commercial buildings from a central source.
Geothermal energy is the energy stored in the form of heat beneath the earth's
surface.Geothermal energy is a carbon free, renewable, sustainable form of energy that provides a
continuous, uninterrupted supply of heat that can be used to heat homes and office buildings and to
generate electricity.Our planet is a huge source of energy. In fact 99.9 per cent of the planet is at a
temperature greater than 100°C; so geothermal energy is a significant renewable resource.
Geothermal energy has been used to provide heat for as long as people have been around to take
advantage of it. For example, in some places the natural groundwater, heated by this geothermal
energy, finds its way to surface and emerges in hot springs or steam geysers, which have been used
by humans for bathing and agriculture since pre-history.

8. List some turbines used in hydro electric power plant.

Based on type of energy at inlet to the turbine:
 Impulse Turbine : The energy is in the form of kinetic form. e.g: Pelton wheel, Turbo wheel.
 Reaction Turbine : The energy is in both Kinetic and Pressure form. e.g: Tubular, Bulb,
Propellar, Francis turbine.
Based on direction of flow of water through the runner:
 Tangential flow: water flows in a direction tangential to path of rotational, i.e. Perpendicular
to both axial and radial directions.
 Radial outward flow e.g :Forneyron turbine.
 Axial flow: Water flows parallel to the axis of the turbine. e.g: Girard, Jonval, Kalpan turbine.
 Mixed flow: Water enters radially at outer periphery and leaves axially. e.g : Modern Francis
turbine.
Based on the head under which turbine works:
 High head, impulse turbine. e.g : Pelton turbine.
 Medium head, reaction turbine. e.g : Francis turbine.
 Low head, reaction turbine. e.g : Kaplan turbine, propeller turbine.
Based on the specific speed of the turbine:
 Low specific speed, impulse turbine. e.g : Pelton wheel.
  Medium specific speed, reaction turbine. e.g : Francis wheel.
 High specific speed, reaction turbine. e.g : Kaplan and Propeller turbine.
5) Based on the name of the originator:
 Impulse turbine – Pelton wheel, Girard, Banki turbine.
 Reaction turbine – Forneyron, Jonval, Francis, Dubs, Deriaze, Thomson kalpan, Barker,
Moody, Nagler, Bell.
9. List the classification of dams:
1. Based on their functions:
(a) storage dams
(b) Diversion dams
(c) Detention dams
2.Based on their shape:
(a) Trapezoidal dams
(b) Arch dams
3.Based on the materials of construction:
(a)Earth dams (b) Rock pieces dams
(c) Stone masonary dams (d) concrete dams
(e) RCC dams (f)Timber and Rubber dams
4.Based on hydraulic design:
(a) Overflow type dam
(b) Non-overflow type dam
5.Based on structural Design:
(a) Gravity dam
(b) Arch dam
(c) Buttresses dam

10. With neat diagram explain the working of bio gas power plant.

Construction & Working of bio gas power plant:

The multi-stage process of producing biogas needs a large amount of micro organisms, which
are able to use the stored energy in carbon hydrates, fats and proteins under anaerobic conditions for
their metabolism. Nearly 70% of the contained methane bacteria use acetic acid for their metabolism,
while 30% of the known species use hydrogen and carbon dioxide. For an optimised setting a
temperature of 30-40°C for mesophilic bacteria and 55 to 60°C for thermophilic bacteria should be
adjusted. The pH-value should be neutral up to low alkaline.
The bacteria of every degradation stage are addicted to each other, because the metabolism products
of one group form the agar for the next group. It is also possible that different groups can inhibit
other groups of bacteria, depending on the amount of contained bacteria at a time. Due to the
occurring order of the processes the production of biogas starts after 4 to 6 weeks after starting the
fermentation process.
According to the requirements of the different substrates for the production of biogas different
technologies are used. These technologies can be classified by the type of reactor into wet
fermentation reactor (up to ~15% dry matter content) and dry fermentation reactor (~25-50% dry
matter content), by the type of feeding (continuous or batch reactor), by the process temperature
(psychrophilic operation up to 20°C; mesophilic operation 30-40°C; thermophilic operation 55-60°C)
and by the number of stages (single-stage, two-stage, multi-stage operation).
In agriculture the wet fermentation is used generally, where over the intervening years several plant
types have been developed. The wet fermentation technology became accepted due to the possibility
of using liquid substrates like manure, which is available in most of the farms, which is ideal for
fermentation. Also the technologies for spreading the liquid fertilizer (digestate) on the fields already
exist. For the production of biogas from stackable biomass the dry fermentation was developed. This
technology can be found less often than the wet fermentation.

11. Explain the construction and working of fuel cell also mention its merits and demerits.

 Compressed hydrogen and oxygen fuel

 Potassium hydroxide (KOH) electrolyte
 70% efficiency
 150˚C - 200˚C operating temp.
 300W to 5kW output

(ii) List the advantages and disadvantages of wind energy system.

Advantages of Wind Energy
1) Wind Energy is an inexhaustible source of energy and is virtually a limitless resource.
2) Energy is generated without polluting environment.
3) This source of energy has tremendous potential to generate energy on large scale.
4) Like solar energy and hydropower, wind power taps a natural physical resource.
5) Windmill generators don’t emit any emissions that can lead to acid rain or greenhouse effect.
6) Wind Energy can be used directly as mechanical energy.
7) In remote areas, wind turbines can be used as great resource to generate energy.
8) In combination with Solar Energy they can be used to provide reliable as well as steady supply of
electricity.
9) Land around wind turbines can be used for other uses, e.g. Farming.
Disadvantages of Wind Energy
1) Wind energy requires expensive storage during peak production time.
2) It is unreliable energy source as winds are uncertain and unpredictable.
3) There is visual and aesthetic impact on region.
4) Requires large open areas for setting up wind farms.
5) Noise pollution problem is usually associated with wind mills.
6) Wind energy can be harnessed only in those areas where wind is strong enough and weather is
windy for most parts of the year.
12. Write on the factors that should be consider while selecting a site for a hydroelectric plant.
1. AVAILABILITY OF WATER
The river run off data pertain to many years should be available so that and estimate of the
power potential of the project and the made .the data should include minimum Flo and maximum
flow and their periods.
2. WATER STORAGE
Because of white fluctuation in stream flows storage is needed most hydroelectric project to
store the water during high flow periods and use it during the leading flow periods. the storage
capacity can be calculated from the hydro graph.
3. GEOLOGICAL INVESTIGATION
It is need to see that the foundation roof from the demand and other structure is stable and
strong enough to with stand water thrust and other stress.
4. WATER POLLUTION
Polluted water may cause excessive corrosion and damage to metallic structure . This may
make the operation of the plant un reliable and UN economical so it is necessary to sea the water is of
good quality.
5. SEDIMENTATION
The capacity of storage reserve wire is reduced dew to the gradual deposition of snit
snit may cause damage to turbine plate .
6. ENVIRONMENTAL EFFECT
Hydro project submerge use areas and many villages the environmental effect are also
importation . The site should ensure safe soundings, avoid heath hazard and presser important
cultural and storage aspect of the area.
7. ACCESS TO SITE
A hydro electric plant installed at the suitable location should be connected threw the rail and
road facilities so that row material and heavy machinery can be transfer at the suitable location very
easily it is also a important factor for selecting the suitably location for hydroelectric plant.
13. What is pumped storage plant? Explain with a sketch.
Pumped-storage hydroelectricity allows energy from intermittent sources (such as solar, wind) and
other renewables, or excess electricity from continuous base-load sources (such as coal or nuclear) to
be saved for periods of higher demand. The reservoirs used with pumped storage are quite small
when compared to conventional hydroelectric dams of similar power capacity, and generating periods
are often less than half a day.
14. Enumerate the advantage of fuel cell power sources with specific reference to environment.
• Fuel cells have a higher efficiency than diesel or gas engines.
• Most fuel cells operate silently, compared to internal combustion engines. They are therefore
ideally suited for use within buildings such as hospitals.
• Fuel cells can eliminate pollution caused by burning fossil fuels; for hydrogen fuelled fuel
cells, the only by-product at point of use is water.
• If the hydrogen comes from the electrolysis of water driven by renewable energy, then using
fuel cells eliminates greenhouse gases over the whole cycle.
• Fuel cells do not need conventional fuels such as oil or gas and can therefore reduce
economic dependence on oil producing countries, creating greater energy security for the user
nation.
• Since hydrogen can be produced anywhere where there is water and a source of power,
generation of fuel can be distributed and does not have to be grid-dependent.
• The use of stationary fuel cells to generate power at the point of use allows for a decentralised
power grid that is potentially more stable.
• Low temperature fuel cells (PEMFC, DMFC) have low heat transmission which makes them
ideal for military applications.
• Higher temperature fuel cells produce high-grade process heat along with electricity and are
well suited to cogeneration applications (such as combined heat and power for residential
use).
• Operating times are much longer than with batteries, since doubling the operating time needs
only doubling the amount of fuel and not the doubling of the capacity of the unit itself.
• Unlike batteries, fuel cells have no "memory effect" when they are getting refuelled.
• The maintenance of fuel cells is simple since there are few moving parts in the system.

15. Draw and Explain Pelton wheel?

 A pelton wheel is shown in figure. Itconsists of a
 Runner,
 Buckets,
 Nozzle,
 Guide Mechanism,
 Hydraulic Brake
 Casing.
16. Draw and Explain the construction and working principle of Francis turbine?

Figure shows the parts of a Francis turbine. It consists of a

 Scroll casing
 Stay ring
 Guide mechanism
 Runner
 Draft tube.

17. Draw and explain the construction and working principle of Kaplan turbine?

The main components of a Kaplan turbine are shown in figure. It consists of a

 Scroll Case
 Staring
 Guide Vane Mechanism
 Draft Tube
18. Explain with the neat sketchtidal power plant.
 It is a rise and fall of water level of sea
 Due to the action of sun and moon on the earth water.

Main components:
  Power house
 Dam to form basin
 Sluice gates

19. Explain the various methods of tidal power generation.

Classifications:
 Single basin arrangement.
 Double basin arrangement.
20. Explain the Geo-thermal power plant.
 The heat energy of interior of earth.
Classifications:
 Direct or dry steam PP
 Flash steam
 Binary fluid

Un expected Question
21. Explain with the neat sketch solar power plant.

Main components:
 Solar field
 Storage tank
 Solar steam generatorSteam turbine
 Condenser
 Generator
22. Explain the distributed generation.
 The integrated use of small generation units directly connected to the system.
 Operate on a renewable fuel such as sun light, wind, gas and biomass.
23. What are the technologies used distributed generation, explain it.
 Micro turbines
 Fuel cells
 Photovoltaic cell
 Internal combustion engines
24. Explain with the neat sketchMagneto Hydro Dynamic generation (MHD).

Components:
  Combustor
 MHD generator
 Air pre heater
 Purifier
 Inverter
 Seed recovery
 Stack
25. Explain the working of fuel cells.
 The familiar process of electrolysis requires work to proceed, if the process is put in reverse,
it should be able to do work for us spontaneously.
 The most basic “black box” representation of a fuel cell in action is shown below:

26. Explain the working of Molten Carbonate Fuel Cell (MCFC).

 Carbonate salt electrolyte
 60 – 80% efficiency
 ~ 650˚C operating temp.
 Cheap nickel electrode catylist
 Up to 2 MW constructed, up to 100 MW designs exist
 UNIT V OTHER ENERGY SOURCES
1. (i) Explain the methods of energy extraction technique on ocean tidal energy source. (April /
May 2023)
Below are six popular methods and technologies that are leading the way in capturing this
renewable ocean energy.
1. Tidal Stream Turbines
2. Archimedes Screws
3. Tidal Dams, Barrages, and Lagoons
4. Floating Structures
5. Tidal Kites
6. Artificially Intelligent Turbines
(ii) How do you estimate the power potential of ocean tidal energy source? (April / May 2023)
There are important issues to be addressed in the configuration of the tidal energy conversion
system. First, the Colvos Passage must remain navigable so it is assumed that tidal energy converter
may not extend beyond mid-channel, meaning turbines from 50 to 400m from shore. Also there are
limits to the amount of energy that can be extracted from an open flow channel. If too many turbines
are placed in the passage, the device will appear as a dam to the flowing water, which will simply stop
moving or it will bypass the turbines and there will be no energy capture. To avoid this problem, the
turbines in the conceptual design were placed in two rows, 5 turbines in top (near surface) row with 2
rotor diameter (2d) spacing and 4 in row at 3d depth (U.S. Department of Energy, 2002).
Environmental impacts
Tidal barrage schemes have a large impact on a estuary. With a reduced tidal range above the
barrage there are potential changes to the land drainage, fish migration, navigation of ships, wading
bird activities plus the possible increased sedimentation due to altered channel turbulence and flow in
the estuary. Several advantages follow from the building a barrage, however, through the provision of
the route for road traffic across an estuary and with the reduced tidal range comes increased
opportunities for recreational sailing and water sports.
Economics
The benefits derived from inclusion of a tidal power plant are due to the cost of the fuel saved. Primary
role of tidal power that would make it economically feasible:
 Replace fossil fuel
 Replace nuclear generated energy
 Reduce oil needs by one-half
 Save 3 million barrels of oil
 Save 330,000 tons of coal
 Save 90.8 tons of uranium
(iii) List out the limitations of tidal energy conservation system. (April / May 2023)
The limitations of harnessing tidal energy are given below:
 High construction costs for tidal power plants.
 They must be extremely strong in order to withstand the force of the sea.
 To convert tidal energy into electricity, high dams must be built.
 It has a negative impact on marine life forms.
2. Explain the construction of various types of fuel cells. (April / May 2023)
 The familiar process of electrolysis requires work to proceed, if the process is put in reverse, it
should be able to do work for us spontaneously.
 The most basic “black box” representation of a fuel cell in action is shown below:

3. Briefly discuss the components of tidal power system with neat diagram. (Nov / Dec 2022)

What is tidal energy? Explain the working of a tidal power plant with a neat sketch. (Nov / Dec
2021)
 It is a rise and fall of water level of sea
 Due to the action of sun and moon on the earth water.

Main components:
 Power house
 Dam to form basin
 Sluice gates

4. Describe the construction of Hydrogen –Oxygen fuel cell. (Nov / Dec 2022)

• Compressed hydrogen and oxygen fuel

• Potassium hydroxide (KOH) electrolyte
• 70% efficiency
• 150˚C - 200˚C operating temp.
• 300W to 5kW output
5. Discuss the theory and working principle of ocean thermal energy conversion
systems.(Nov / Dec 2021)
OTEC
OTEC or ocean thermal energy thermal conversion is a technology which converts solar
radiation absorbed by the oceans to electric energy. The ocean’s can be considered as the world’s
largest solar energy collector as it covers two third of the earth surface.
OCEAN TEMPRATURE DIFFRENCE
There is different temperature in the different layers of the oceans. This is because of the
heat input from the sun at the surface of ocean. The surface at the top of the oceans are warmest
and gradually the temperature decreases with in depth. But in the polar regions the temperature at
the surface of ocean is low,so there is no gradual change in temperature.
PRINCIPLES OF OTEC PLANT OPERATION
The working principle of an OTEC plant is that it uses the warm water to heat and vaporize
a liquid ( working fluid).And this working fluid develops pressure which forces it to evaporate and
the expanding vapour runs through a heat engine like turbine, generator, and it is condensed back
into a liquid by cold water brought up from depth and the cycle is repeated.
As we know that water is not perfectly transparent nearly all sunlight is absorbed in the surface
layer which heats up. As warm water raises and cold water sinks so this warm water stays near the
ocean’s surface. Now Wind and waves circulate the water in the surface layer distributing the heat
within it to some extend, and the temperature may remain quite uniform for the first hundred
metres, but below the mixed layer the temperature drops very rapidly, perhaps 20 degrees Celsius
with an additional of 150 m depth. This area of rapid transition is called thermo cline and below it
the temperature continues to drop with depth but very gradually.
Generally thermo cline varies with latitude and season but it is permanent in the tropics,
variable in the temperate climates is strongest during the summer and is weak to nonexistent in the
polar regions where the water is cold from the surface to the bottom.

There are basically three types of OTEC power plant:

• Closed cycle
• Open cycle
• Hybrid cycle
6. Describe the working of a wind power system and its components with a neat schematic
diagram?
The wind power plant comprises one or more wind turbine units operating electrically in parallel.
Each turbine is made of the following basic components :
1. Blades 2. Rotor 3. Pitch 4. Brake 5. Low speed shaft 6. Gear box 7. Generator 8. Controller 9.
Anemometer10. Wind Vane 11. Nacelle 12. High speed shaft 13. Yaw drive 14. Yaw motor 15.
Tower
Turbine Blades
The blade is the most distinctive and visible component of a wind turbine. It is also responsible for
carrying out one of the most essential tasks of the energy conversion process : Transforming the
wind kinetic energy into rotational mechanical energy.Blades have greatly evolved in aerodynamic
design and materials from the earlywindmill blades made of wood and cloth.
Rotor :
The blades and the hub together are called the rotor.
Pitch :
Blades are turned, or pitched, out of the wind to control the rotor speed and keep the rotor from
turning in winds that are too high or too low produce electricity.
Brake :
A disc brake, which can be applied mechanically, electrically, or hydraulically to stop the rotor in
emergencies.
Low-speed shaft :
The rotor turns the low-speed shaft at about 30 to 60 rotations per minute.
Gear box :
Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from
about 30 to 60 rotations per minute (rpm) to about 1000 to 1800 rpm, the rotational speed required
by most generators to produce electricity.
Wind vane :
Measures wind direction and communicates with the yaw drive to orient the turbine properly with
respect to the wind.
Generator :
Usually an induction generator that produces 50-cycle AC electricity.

7. What is pumped storage plant? Explain with a sketch.

Pumped-storage hydroelectricity allows energy from intermittent sources (such
as solar, wind) and other renewable, or excess electricity from continuous base-load sources (such
as coal or nuclear) to be saved for periods of higher demand. The reservoirs used with pumped
storage are quite small when compared to conventional hydroelectric dams of similar power
capacity, and generating periods are often less than half a day.

8. Explain the Geo-thermal power plant.

 The heat energy of interior of earth.
Classifications:
 Direct or dry steam PP
 Flash steam
 Binary fluid
9. Explain the distributed generation.
 The integrated use of small generation units directly connected to the system.
 Operate on a renewable fuel such as sun light, wind, gas and biomass.

10. What are the technologies used distributed generation, explain it.
 Micro turbines
 Fuel cells
 Photovoltaic cell
 Internal combustion engines

11. Explain with the neat sketchMagneto Hydro Dynamic generation (MHD).

Components:
 Combustor
 MHD generator
 Air pre heater
 Purifier
 Inverter
 Seed recovery
 Stack
12. Explain the working of fuel cells.
 The familiar process of electrolysis requires work to proceed, if the process is put in reverse, it
should be able to do work for us spontaneously.
 The most basic “black box”.
13. Explain the working of Molten Carbonate Fuel Cell (MCFC).
 Carbonate salt electrolyte
 60 – 80% efficiency
 ~ 650˚C operating temp.
 Cheap nickel electrode catylist
 Up to 2 MW constructed, up to 100 MW designs exist
14. Explain the working of Phosphoric Acid Fuel Cell (PAFC).
 Phosphoric acid electrolyte
 40 – 80% efficiency
 150˚C - 200˚C operating temp
 11 MW units have been tested
 Sulphur free gasoline can be used as a fuel

15. Explain the working of Proton Exchange Membrane (PEM).

 Thin permeable polymer sheet electrolyte
 40 – 50% efficiency
 50 – 250 kW
 80˚C operating temperature

16. Enumerate the advantage of fuel cell power sources with specific reference to environment.
• Fuel cells have a higher efficiency than diesel or gas engines.
• Most fuel cells operate silently, compared to internal combustion engines. They are therefore
ideally suited for use within buildings such as hospitals.
• Fuel cells can eliminate pollution caused by burning fossil fuels; for hydrogen fuelled fuel cells,
the only by-product at point of use is water.
• If the hydrogen comes from the electrolysis of water driven by renewable energy, then using fuel
cells eliminates greenhouse gases over the whole cycle.
• Fuel cells do not need conventional fuels such as oil or gas and can therefore reduce economic
dependence on oil producing countries, creating greater energy security for the user nation.
• Since hydrogen can be produced anywhere where there is water and a source of power, generation
of fuel can be distributed and does not have to be grid-dependent.
• The use of stationary fuel cells to generate power at the point of use allows for a decentralized
power grid that is potentially more stable.
• Low temperature fuel cells (PEMFC, DMFC) have low heat transmission which makes them ideal
for military applications.
• Higher temperature fuel cells produce high-grade process heat along with electricity and are well
suited to cogeneration applications (such as combined heat and power for residential use).
 • Operating times are much longer than with batteries, since doubling the operating time needs only
doubling the amount of fuel and not the doubling of the capacity of the unit itself.
• Unlike batteries, fuel cells have no "memory effect" when they are getting refueled.
• The maintenance of fuel cells is simple since there are few moving parts in the system.
17. Explain the various methods of tidal power generation.
Classifications:
 Single basin arrangement.
 Double basin arrangement.
18. Explain the working of Wave Profile Devices.

The pitching and heaving of the waves causes a relative motion between an absorber and
reaction point. The left hand wave energy device above, uses a heavy ballast plate suspended
below the floating buoy. The buoy is prevented from floating away by a mooring line attached to a
sea-floor anchor. This mooring line allows the point absorber to operate offshore in deeper waters.
As the buoy bobs up-and-down in the waves, a oscillatory mutual force reaction is generated
between the freely moving absorber and the heavy plate causing a hydraulic pump in between to
rotate a generator producing electricity. The middle wave energy device operates in a similar
manner to the previous floating buoy device.
The difference this time is that the freely heaving buoy reacts against a fixed reaction point
such as a fixed dead-weight on the ocean floor. As this type of point absorber is bottom mounted,
it is operated in shallower near shore locations.
The third device is an example of a linear absorber (wave attenuator) which floats on the
surface of the water. It to is tethered to the ocean floor so that it can swing perpendicularly towards
the incoming waves. As the waves pass along the length of this snake like wave energy device,
they cause the long cylindrical body to sag downwards into the troughs of the waves and arch
upwards when the waves crest is passing.
19. Explain the working of Oscillating Wave Column.

As the incident waves outside enter and exit the chamber, changes in wave movement on
the opening cause the water level within the enclosure to oscillate up and down acting like a giant
piston on the air above the surface of the water, pushing it back and forth. This air is compressed
and decompressed by this movement every cycle. The air is channeled through a wind turbine
generator to produce electricity as shown.
The type of wind turbine generator used in an oscillating water column design is the key
element to its conversion efficiency. The air inside the chamber is constantly reversing direction
with every up-and-down movement of the sea water producing a sucking and blowing effect
through the turbine. If a conventional turbine was used to drive the attached generator, this too
would be constantly changing direction in unison with the air flow. To overcome this problem the
type of wind turbine used in oscillating water column schemes is called a Wells Turbine.
The Wells turbine has the remarkable property of rotating in the same direction regardless
of the direction of air flow in the column. The kinetic energy is extracted from the reversing air
flow by the Wells turbine and is used to drive an electrical induction generator. The speed of the
air flow through the wells turbine can be enhanced by making the cross-sectional area of the wave
turbines duct much less than that of the sea column.
As with other wave energy converters, oscillating wave column technology produces no
greenhouse gas emissions making it a non-polluting and renewable source of energy, created by
natural transfer of wind energy through a wells turbine. The advantage of this shoreline scheme is
that the main moving part, the turbine can be easily removed for repair or maintenance because it
is on land. The disadvantage though is that, as with the previous wave energy devices, the
oscillating wave columns output is dependent on the level of wave energy, which varies day by
day according to the season.

20. Explain the working of Capture Wave Energy Devices.

The basic impoundment structure can be either fixed or a floating structure tethered to the
sea bed. The wave overtopping device uses a ramp design on the device to elevate part of the
incoming waves above their natural height.
As the waves hit the structure they flow up a ramp and over the top (hence the name
“overtopping”), into a raised water impoundment reservoir on the device in order to fill it. Once
captured, the potential energy of the trapped water in the reservoir is extracted using gravity as the
water returns to the sea via a low-head Kaplan turbine generator located at the bottom of the wave
capture device.
Other such wave capture devices are located at the shoreline were the waves are channeled
along a horizontal man made channel. This channel is funnel shaped which is wide towards the sea
where the waves enter and gradually narrows towards an impoundment reservoir at the other end.
As the waves propagate along the narrowing channel, the wave height is lifted due to the funneling
effect to a level exceeding the horizontal upper edge of the channel wall, excess water from the
wave is allowed to spill into a confined basin above the normal sea level. Since the water is now at
a height above the sea level, the potential energy of the water trapped in the basin is then extracted
by draining the water back to the sea through a low-head Kaplan turbine as before.
We now know how wave energy works and one of the main advantages of “wave energy
devices”, is that besides the generating turbine there are no moving parts. Unfortunately, shoreline
overtopping schemes have a relatively low power output due to their low head and are only
suitable for sites where there is a deep water shoreline and a low tidal range of less than about a
metre. To overcome some of these limitations, floating offshore capture devices have been
developed, but they too require sufficient wave power to fill the impoundment reservoir.
21. Explain the working of Hybrid Energy Systems.

According to many renewable energy experts, a small "hybrid" electric system that
combines home wind electric and home solar electric (photovoltaic or PV) technologies offers
several advantages over either single system.
In much of the United States, wind speeds are low in the summer when the sun shines
brightest and longest. The wind is strong in the winter when less sunlight is available. Because the
peak operating times for wind and solar systems occur at different times of the day and year,
hybrid systems are more likely to produce power when you need it.
Many hybrid systems are stand-alone systems, which operate "off-grid" that is, not
connected to an electricity distribution system. For the times when neither the wind nor the solar
system are producing, most hybrid systems provide power through batteries and/or an engine
generator powered by conventional fuels, such as diesel. If the batteries run low, the engine
generator can provide power and recharge the batteries.
Adding an engine generator makes the system more complex, but modern electronic
controllers can operate these systems automatically. An engine generator can also reduce the size
of the other components needed for the system. Keep in mind that the storage capacity must be
large enough to supply electrical needs during non-charging periods. Battery banks are typically
sized to supply the electric load for one to three days.

Un expected question:
22. Explain the working of Solid Oxide Fuel Cell (SOFC).
 Hard ceramic oxide electrolyte
 ~60% efficient
 ~1000˚C operating temperature
 Cells output up to 100 kW
23. Explain components ofBio- Mass, Municipal waste power generation.
 Enclosed receiving area
 Refuse feed hopper
 Crane
 Boiler
 Steam pipe to turbine generator
 Steam drum
 Turbine
 Generator
 Fabric bag filter
 Induced draft fan
 Stack
24. Explain the classifications of wind energy conversion?
 Horizontal axis wind mill
 Vertical axis wind mill
25. List the classification of dams:
1. Based on their functions:
(a) storage dams
(b) Diversion dams
(c) Detention dams
2.Based on their shape:
(a) Trapezoidal dams
(b) Arch dams
3.Based on the materials of construction:
(a)Earth dams (b) Rock pieces dams
(c) Stone masonary dams (d) concrete dams
(e) RCC dams (f)Timber and Rubber dams
4.Based on hydraulic design:
(a) Overflow type dam
(b) Non-overflow type dam
5.Based on structural Design:
(a) Gravity dam
(b) Arch dam
(c) Buttresses dam
26. List the equipment’s present in a power house:
 Hydraulic turbines
 Electric generators
 Governors
 Gate valves and rehet valves
 Water circulating pumps
 Air duct
 Switch board and instruments
 Storage batteries and cranes