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bankercordMechanics

Oct 27, 2013 (4 years and 10 days ago)

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1



Chapter 1

INTRODUCTION

1.1

Background

Energy is one of the essential needs of a functional society. As the demand for energy is
increasing globally, strenuous efforts are required
to increase the efficiency of energy use. The
most available and affordable sources of energy in today’s economic structure are fossil fuels
(about 85% of all commercial energy is derived from them). Efficiency improvement and new
technologies are a part o
f the solution. Renewable Energy technologies can meet much of
growing demands lower than those usually forecast for conventional energy. By the middle of the
21
st

century renewable sources of energy could account for three fifth of the world electricity
m
arket and two fifth of the market for the conventional fuels

[1]
. Moreover making the transition
to renewable
-
intensive energy economy would provide environmental and other benefits.

This outlook for renewable energy reflects impressive technical gains ma
de during the past
decade. Renewable energy system has benefited from developments in electronics, bio
-
technology, material science and other energy areas. For example fuel cells developed originally
for space programs have opened doors to the use of hydro
gen as a nonpolluting fuel for
transportation

Such concerns have led to the creation of political movements pressing for changes in our
demand for the environment. These pressures have ranged from criticism of individual practices
(growth in the heavy vehi
cle portion of the passenger automobiles economy) to demands that the
overall structure and economic basis of societies be changed. Many pressures are focused on
energy, in terms of its uses, supply technologies and efficiencies. These concerns have often
been



2


expressed in demands for less use, greater end use efficiencies, and more reliance on solar and
geothermal powered technologies rather than fossil and nuclear energy, which extract their f
uel
from finite earth resources
[1]
.

In the most extreme guise
sustainable energy is that which can be provided without change in the
earth’s biosphere. However no such form of energy supply exists. All require some kind of land
use, with attended disruptions of the associated eco
-
system extractions, which can be disr
uptive
for nuclear ones. Ultimately all this extracted material re
-
enter the biosphere as wastes where
their sequestration practices are at least as important as their masses in determining the
accompanying ecological disruptions.

Energy production or util
ization is often intertwined with consumption of other precious natural
resources, such as mineral, forest, water, food and land. Further the everyday use of energy can
damage human health and earth’s ecosystem over wide length and timescale. Yet in the
de
veloped countries the availability of stable supplies of energy at manageable prices has
propelled has propelled economic development and enfranchised most of the populace with
mobility and a host of life style which were unimaginable a century ago. Develo
pment countries
are now dramatically expanding there to extend economic prosperity within their borders. At the
same time continued dominance of the world’s energy by fossil fuels is expected to be challenged
not by the red herring of scarcity but by conce
rn that emission of fossil derived CO2 and fugitive
CH4 to the atmosphere will cause serious global climatic modifications.

For more sustainable energy future we need to develop a rich set of energy technology and
technology intensive policy options. These

options include increased efficiency of energy



3


production and use, reduced consumption, a new generation of renewable energy technologies,
nuclear options that can retain public acceptance, and means to use fossil fuels in a climate
friendly way. If fossi
l fuel prices rise to include cost of carbon management, consumers may also
modify their consumption patterns. Environmental and ethical concerns may also contribute to
new attitudes about unconstrained economic growth patterns. Sustainability concepts pro
vide a
framework to focus the evaluation of energy technology and policy options and their tradeoffs
and to guide the decision making on energy futures. The key to these concepts right is to develop
a solid understanding of the multi facet technological, g
eopolitical, sociological, and the
economic impacts of energy use and abuse.

Sustainability is necessary subjective because it reflects human values
-

the relative importance
stakeholders assign to the activity to be sustained, to the perceived benefits of
the activity, and to
other values “tradeoffs” to sustain the activity in question. Many sustainability tradeoffs are an
inevitable result of tension between the benefits derived and the adverse consequences of the
activity that provides those benefits for
instance the tension includes time horizons for reform i.e.
taking the best now versus preserving it from future generations, individual versus national verses
global interest and expansion of economic opportunity versus stewardship of resources

[1]
.

1.2 O
bjective

The objective
of this project is to provide information
on
the

various types of renewable energy
resources available, with major focus on the wind energy. The project outlines what is renewable
and sustainable energy alone with brief discussion on

the available resources such as Biomass,
Hydropower, Solar and major focus on Wind Energy and

research
review

on

Energy Generation



4


in Tall Buildings

. The review ‘Energy Generation in Tall Buildings” is focused on latest concept
of producing energy by wi
nd turbine augmented/mounted in tall buildings. The project mainly
summarizes how the resources are used in energy production, what has been done till now in that
field of development and what is the research which is going on in that field of development
for
future. It also details the meaning of Sustainable and Renewable resources.

T
he research review on Energy Generation in Tall Building is the latest concept which got
recognition due to the energy losses in transmission from wind mills. The research rev
iew
discusses all the latest research in the field along with
feasibility features design and complete
assessment of wind flow characteristics.

1.3 Methodology

To achieve the above mentioned objective the concept of S
ustainable/Renewable energy
requirement
s is explained from the very basic fundamental as to what is energy, and the how is it
related to the first and second law of thermodynamics. Explanation of Sustainable Energy and
Renewable Energy and the relationship they share. A brief introduction to t
he
resources such as
biomass, hydro
-
power and solar which provides us this

Sustainable/Renewable energy. As Wind
Energy from the economic stand is the most deserving green supply option for more widespread
deployment is discussed at length along
-
with the w
ind resources, wind speed and the factors
attributed to technological aspects to see the advances of the sort that improved the rotor
efficiency to 30% over past two decades. Last but not the least

a research review on Energy
Generation in Tall Building is

discussed as to the elaborate the modern concept of wind energy
.





5


Chapter 2

OVERVIE
W ON CRUCIAL SUSTAINABLE ENERGY

2.1

What is Sustainable Energy?

Energy is one of the essential needs of functioning society. With the increasing population of the
world
which has tripled since 1930 there is more need for energy. The most available and
affordable sources of energy in today’s world are fossil fuels, efficiency improvements and new
technologies are part of the solution. Concerns have often been expressed in
demands of less use,
greater end use efficiencies and more reliance on solar and geothermal powered technologies
rather than fossil and nuclear energy. In most extreme guise, sustainable energy is that which can
be provided without change to the earth’s bi
osphere.

Sustainable energy

is the provision of energy that meets the needs of the present without
compromising the ability of future generations to meet their needs. Sustainable energy sources are
most often regarded as including all renewable sources, su
ch as plant matter, solar power, wind
power, wave power, geothermal power and tidal power. It usually also includes technologies that
improve energy efficiency.

Energy technologies are being considered as sustainable if their net effects upon the biospher
e
don’t significantly degrade its capabilities for supporting existing species in their current
abundance and diversity.


Energy efficiency and renewable energy are said to be the twin pillars of sustainable
energy. Some ways in which sustainable energy ha
s been defined are

[1]
:




6




"Effectively, the provision of energy such that it meets the needs of the future without
compromising the ability of future generations to meet their own needs. ...Sustainable
Energy has two key components: renewable energy and ener
gy efficiency."



"Dynamic harmony between equitable availability of energy
-
intensive goods and services
to all people and the preservation of the earth for future generations." And, "the solution
will lie in finding sustainable energy sources and more effi
cient means of converting and
utilizing energy."



"Any energy generation, efficiency & conservation source where: Resources are available
to enable massive scaling to become a significant portion of energy generation, l
ong
term, preferably 100 years
"



"Ener
gy which is replenish able within a human lifetime and causes no long
-
term damage
to the environment."

2.2
Defining

Energy
-

Scientific and Engineering Foundation

To understand the energy suitable for quantitative study for sustainability we must understand

the, energy

2.2
.1

What

is Energy?

Basically energy embodies animated and possible productive physical or mental activity
presumably by humans, animals, machines, nature, electricity etc. The first definition of energy
which came out in 1805 and was given
by Thomas Young was “ability to do work” We think of



7


work as physical or mental exertion, to comprehend the concept of sustainable energy we need to
understand 4 key concepts namely energy, work, heat and power.

Observation has shown that a certain quantit
ies remain constant during physical, chemical and
biological changes. This conserved or immutable quantity is energy. First of all let us understand
the meaning or conservation of energy which means we cannot get rid of the energy. Let us
divide the entire

universe into specific regions with well
-
defined boundaries and other particular
characteristics. We define such a region into a system for example


(System 1


combustion
chamber of an automobile engine and all the rest of the universe as System 2 which

we define as
the surroundings). What is important here is not the absolute energy content of the universe or the
system or even set of systems but rather the change in energy content of particular system within
the universe and their interaction with thei
r surroundings during the course of that change. In such
analysis it is important to know foe particular circumstances the total amount of energy a system
can give to or take from its surroundings and what fraction of that changed energy can be
converted t
o useful purpose such as the motion of an automobile or generation of electricity
[1]
.

The first and second law of thermodynamics provides useful the theory to explain this concept
assuming that we have necessary data to implement the tool of thermodynamics

for practical
calculation. It is important to know the how rapidly the energy can be generated within or
assimilated by or released from one or more systems example to this is how fast the chemical
energy of fuel be converted to kinetic energy of an autom
obile or thrust that propels a rocket. To
address these questions we need to rely on thermodynamics chemical kinematics, physical
transport and fluid mechanics to describe the rates of chemical reaction and the exchange of heat
material and the momentum wi
thin and between a single and multi
-
phase media.

[4]




8


The position or motion of matter causes energy to exhibit diverse forms. Many of them are
rapidly observed such as (changes in pressure, temperature, volume, surface area and
electromagnetic properties).

Thermodynamically heat and all forms of energy are related to
mechanical work such as raising and lowering of weights in a gravitational field.

A closed thermodynamic system is completely surrounded by movable boundaries permeable to
heat but no matter ex
ample of this is a vertical cylinder filled with gas and covered with piston
that can be moved up and down. By adding weights to the piston we can compress the gas and
store energy in analogy to pushing on a coiled spring. This addition of weights is a exa
mple of
work performed by the surroundings on our system. The resulting downward movement of the
piston is the work obtained by the system from its surroundings regardless of how meticulously
the weights were added. The amount of work taken by the system i
s always less than the work
done on the system by its surroundings by an amount of energy exactly equal to the heat gained
by the system which is the basic concept of second law of thermodynamics. Hence we can say
heat is a form of energy. In the example o
f the piston it arises from wasted of lost work. Thus we
can say that heat is a mode of energy transfer to or from a system by virtue of contact with
another system at higher or lower temperature. “Work is a defined as any mode of energy transfer
other tha
n heat that changes the energy of the system”. Power is a energy change between two
systems it has units of energy per time and may represent a flow of work heat or both.

[3]

Thus formal thermodynamic statement of law of conservation of energy is the First

Law of
Thermodynamics. Thus mathematically for a closed system




∆E = Q + W






(
2.1
)





9


Where ∆E is the change in energy content of a system, Q is the
amount of heat transferred to the
system from its surroundings and W is the amount of work done on the system by its
surroundings.

In many practical problems we come across problems where system is not closed but is a open
system where matter can flow inwa
rd outward or in both directions across the system boundaries.


∆E = ∆U + ∆Ep + ∆Ek = Q + Wsh


Wpv



(2
.2
)

This expression tells us that the change in the energy content E of a closed system can be d
ivided
into chances in the internal energy U , potential energy Ep and kinetic energy Ek of the system .
The internal energy of the system can be changed by modifying the system temperature, changing
its phase (solid or liquid), by chemical reaction (ie by

changing its molecular architecture) or
changing its atomic structure (ie by fragmenting (fission) or coalescing (fusion) nuclear particles.
The potential energy is changed by shifting the system location in the force field (gravitational ,
magnetic or el
ectric).The kinetic energy of a system is varied by increasing or decreasing the
system velocity. The above equation disintegrates in to PV Work and SH Work.

Shaft work can be defined as any work other than PV work and it may involve rotation of the
shaft
but may not include electrical work and other forms. PV work arises from the fact that every
system, however small, has some volume. As previously discussed applying weights on the
piston at the cylinder head we concluded that the change in system volume c
hanges the system
potential energy. So any system at equilibrium (i e fixed temperature, pressure and composition)
has a constant volume. To attain that volume the system has to push its surroundings out of the



10


way to make room for itself. The work done by

the system to reach the volume V by showing
back a pressure P is PV work and is given by the expression.



Wpv = ʃ PdV




(
2.3
)

It is often convenient t
o combine the systems internal energy U with the energy it has by virtue of
its volume V and pressure P. The resulting thermodynamic quantity is the enthalpy H which is
mathematically defined as



H = U + PV







(
2.
4)


Where P is the pressure in the system in some cases it may also
include the pressure of the surroundings (atmospheric pressure) but this is not always the case. As
with other forms of ener
gy we are interested in the change in enthalpy when the system changes
from state
2.
1 to state

2.
2



∆H = H2


H1 = ∆U + ∆(PV)




(
2.
5)



= (U2 + P2V2)


(U1 + P1V1)



(
2.
6)


Equation
2.1 and 2.

2
apply

to closed and open system. If a
closed system undergoes a change in energy but remains at constant volume, there is no PV work
and the basic equation at

constant volume for a closed system reduces to


∆U + ∆Ep + ∆Ek = Q + Ws


(2.7)

The second case is when pressure remains constant so the equation becomes




11



∆U + ∆Ep +

∆Ek = Q + Wsh


(P2V2

P1V1)




(2.8)



(U2 + P2V2)


(U1 + P1V1) + ∆Ep + ∆Ek = Q +Wsh

(2.9)



∆H + ∆Ep + ∆Ek = Q + Wsh


(2.10)

For change in energy content of a closed system at constant pressure we can write the law of
energy conservation directly in terms of change in the system enthalpy, potential energy and
kinetic energy. Further
to that is if the system is at rest and moves at a constant velocity or any
motion in a forced field which does not modify its potential energy which means the system
remains at the same height in the gravitational field than the enthalpy change accounts f
or all the
change in energy brought by addition and removal of shaft work.

2.3

What is Renewable Energy?

Renewable Energy
-

Any energy resource that is naturally regenerated over a short time scale and
derived directly from the sun (such as thermal,
photochemical, and photoelectric), indirectly from
the sun (such as wind, hydropower, and photosynthetic energy stored in biomass), or from other
natural movements and mechanisms of the environment (such as geothermal and tidal energy).
Renewable energy do
es not include energy resources derived from fossil fuels, waste products
from fossil sources, or waste products from inorganic

sources
."

Renewable energy flows involve natural phenomena such as sunlight,
w
ind
,
tides
,
plant growth
,
and
geothermal h
eat
.

Renewable energy is derived from natural processes that are replenished constantly. In its various
forms, it derives directly from the sun, or from heat generated deep within the earth. Included in



12


the definition is electricity and heat generated from

solar, wind, ocean, hydropower, biomass,
geothermal resources, and bio
-
fuels and hydrogen derived from renewable resources.

2.4

Kinds of Renewable Energy

Renewable energy is the energy which comes from the natural resources such as sunlight, wind,
rain ti
des and geothermal heat which are renewable. Classifying an energy form as “renewable”
encompasses a range of assumptions regarding the time scale. The implication is that the
renewable energy is available continuously without depleting and degrading. For
example solar
energy is available for some time period every day virtually everywhere on the surface of the
earth. There is a natural 24 hour diurnal cycle, as well as seasonal vibration due to the changes in
the relative angle of our rotating earth tilted

on its axis as it makes its yearly orbit around the sun.
Due to these effects are the daily fluctuations that result because of the cloud cover. Other
renewable types such as Biomass, Hydro Power and Wind Energy have analogous variat
ions over
different ti
me scale

[6]
.

2.
5

Bio Mass Energy

Biomass (plant material) is a renewable energy source because the energy it contains comes from
the sun. Through the process of photosynthesis, plants capture the sun's energy. When the plants
are burned, they release the sun's energy they contain. In this

way, biomass functions as a sort of
natural battery for storing solar energy. As long as biomass is produced sustainable, with only as
much used as is grown, the battery will last indefinitely.




13


In general there are two main approaches to using plants for

energy production: growing plants
specifically for energy use, and using the residues from plants that are used for other things. The
best approaches vary from region to region according to climate, soils and geography.

Biomass, a renewable energy source,

is biological material from living, or recently living
organisms, such as wood, waste, (hydrogen) gas, and alcohol fuels. Biomass is commonly plant
matter grown to generate electricity or produce heat. In this sense, living biomass can also be
included, a
s plants can also generate electricity while still alive. The most conventional way in
which biomass is used however it, still relies on direct incineration. Industrial biomass can be
grown from numerous types of plants, including miscanthus, switch grass,

hemp, corn, poplar,
willow, sorghum, sugarcane, and a variety of tree species, ranging from eucalyptus to oil palm
(palm oil). Biomass qualifies as a renewable energy resource because commercially meaningful
quantities are generated in time scale that is
comparable to or less than typical time scale for
human use of resources.

Indeed biomass is the natural engine for conversion of solar energy to high energy content
products that are stored that can be stored, transported and used conveniently. To explain
this
better plants grow by the process of photosynthesis in which sunlight transforms two naturally
abundant raw materials water and carbon did oxide , to carbohydrates and other complex organic
compounds of great natural and commercial value by photosynth
esis which is as follows

6CO2 + 6H2O → C6H12O6 + 6O2 (with sunlight and catalyst)


(2.11)





14


The above equation represents the process of pumping energy “uphill” because carbon di oxide
and water hav
e zero heating value and reside at one extreme of the energy spectrum. The energy
content comes from solar input , which plants convert to biomass energy with conversion
efficiencies of about 1
-
2%. The catalyst chlorophyll and other plant ingredients facil
itate in the
reaction.

2.5
.1

Bio
-
Mass Relevance to Energy Production


There are thermal and biological routes can be converted into wide range of useful forms of
energy, including process heat, steam, motive power, liquid fuels and electricity as well as
s
ynthesis gas (syngas) and fuel gases of various heating value. Syngas is a precursor to many
other useful products such as methanol, substitute natural gas, ammonia (for fertilizers) and other
liquid transportation fuel.

2.5
.2

Conversion of Bio
-
Mass to
Fuels


Thermal and Hydrothermal processes can also be used to convert various biomass
feedstock’s

into gaseous and liquid fuels. Pyrolysis involves thermal treatment in the
absence of oxygen to gasify the biomass to carbon monoxide and hydrogen (syngas). T
he
mixture could be chemically converted to the liquid and gaseous fuels using suitable
catalyst. Alternatively food processing waste that have high level of fats and oils can be
easily hydrolyzed to produce low Btu gas and high

bio
-
diesel grade liquid fue
l.
[7]




15





Fig
ure

2.1

Gasification process

[38]

2.5.3 Bioconversion


Bioconversion or biochemical processing refers to the direct or adaptive use of the chemistry of
living things to transform one substance to another. Fermentation is a bio
-
conversion process
known for centuries as a means to transform carbohydrates (sugar)

to ethyl alcohol. It is a basis of
production of a host of beverages as well as ethanol for production of fuel. Bioconversion is
appealing as is it accepts feed materials that vary appreciable in chemical composition and
generates useful products moreove
r it enables the human understanding in biology and
biochemistry to be applied to the manufacture of fuels and other energy producing products such
as chemicals. This provides engineers and scientists with tools to devise processes that will run at
milder
conditions synthesis chemically complex products from structurally simple starting
materials. The disadvantage of bioconversion is that the fuels manufactured are dramatically



16


slower rates than thermal processes and the need to separate the desired product
s from the dilute
mixtures. Slower rates translate to lower throughputs per unit time or the need for large process
vessels, resulting in higher capital costs. Moreover recovery from dilute mixtures consumes
energy and increase operating expense.

[5]

2.5.4

Bio
-
Gas


Biogas typically refers to a gas produced by the biological breakdown of organic matter in the
absence of oxygen. Biogas originates from biogenic material and is a type of bio
-
fuel. Biogas is
produced by anaerobic digestion or fermentation of bio
degradable materials such as biomass,
manure, sewage, municipal waste, green waste,
and plant material

and energy crops. This type of
biogas comprises primarily methane and carbon dioxide. Other types of gas generated by use of
biomass are wood gas, which
is created by gasification of wood or other biomass. This type of
gas consists primarily of nitrogen, hydrogen, and carbon monoxide, with trace amounts of
methane
.

Table 2.5

Schematic of overall process chemistry for production of biogas by
anaerobic dige
stion of wet bio mass
.
.


Complex
organic
matter


Bacteria

that promotes
fermentation and
acetic acid
formation


Short chain fatty
acids, alcohols,
hydrogen etc


Bacteria that
promotes
methane
formation


CH4, CO2,
minerals
and
nitrogen
enriched
slurry




17



Even though CO2 has zero heating value (for combustion in air or oxygen) biogas is still a high
quality fuel gas because pure methane has HHV of 1000 Btu/SCF giving typical biogas a 500
Btu/SCF.

2.5.5 Bio
-
Gas Grid Injection


Gas
-
grid injection is the
injection

of biogas into the
methane grid

(
natural gas grid
). Injections
includes biogas until the breakthrough of
micro combined heat and power

two
-
thirds of all the
energy produced by
biogas power plants

was lost (the heat), using the grid to transport the gas to
customers, the electricity and the heat can be used for
on
-
site generation

resulting in a reduction
of losses in the transportation of energy. Typical energy losses in natural gas transmission
systems range from 1

2%. The current energy losses on a large
electrical syste
m range from 5

8%.



Fig
ure

2.2

SCADA system for pipe lines

[39]




18


The
SCADA

system at the Main Control Room receives all the field data and presents it to the
pipeline operator through a set of screens or
Human Machine Interface
, showing th
e operational
conditions of the pipeline. The operator can monitor the hydraulic conditions of the line, as well
as send operational commands (open/close valves, turn on/off compressors or pumps, change set
points, etc.) through the SCADA system to the fie
ld.

To optimize and secure the operation of these assets, some pipeline companies are using what is
called
Advanced Pipeline Applications
, which are software tools installed on top of the SCADA
system, that provide extended functionality to perform leak de
tection, leak location, batch
tracking (liquid lines), pig tracking, composition tracking, predictive modeling, look ahead
modeling, operator training and more

2.5.6
Environmental

Issues

of Bio
-
Mass Energy


There have been various researches in the field
of environmental issues of biomass energy to
evaluate the assessment and implementation of biomass energy options. Environmental control
becomes more challenging with smaller installations such as residential wood stoves; new units
are equipped with cataly
tic convertors to reduce the adverse emissions. On the positive side
carefully managed growth and harvesting biomass for energy and other application can be used to
restore forests and other sensitive ecosystem. Thus we can say that utilization of biomass
are
important in designing comprehensive strategies to reduce atmospheric buildup of greenhouse
gases while preserving options for supply and use of clean energy and energy intensive consumer
products.




19


2.5.7 Summary


Biomass currently contributes about 3% of total US energy consumption. Since some biomass is
used commercially it represents a slightly higher percentage of total primary energy use. The
major use of combustion of various bio
-
fuels roughly 2 quads in the i
ndustrial and 0.5 quads in
the residential sector. Biomass has several potential benefits in
electric power sector.
It has l
ow
So
x

(sulphur oxide)

emission
,

better

co firing wi
th coal or other fossil fuels for

smooth supply
disruptions and facilitate gradu
al transitioning to reduce fossil dependency and the potential to be
CO2 neutral. In long term it may be possible to apply innovations in biotechnology to breed
plants that directly convert sunlight to directly gasoline and other premium products. To achie
ve
this goal methods are yet to be discovered that utilize the modern tools of bio
-
technology
including genomics, metabolic engineering and molecular level understanding of biocatalysts.

2.6 Hydro
-
Power


Hydropower is a renewable energy resource resulting
from stored energy in water that flows
from a higher to a lower elevation under the influence of earth gravitational field.

Hydropower or
water power is
power

that is der
ived from the
force

or
energy

of moving water, which may be
harnessed for useful purposes. Prior to the widespread availability of commercial
electric power
,
hydropower was used for
irrigation
, and operation of various machines, such as
watermills
,
textile

machines,
sawmills
, dock
cranes
, and domestic
lifts
.






20


2.6.1
Basic

Energy Conversion Principles


The primary energy source for hydropower is solar and
gravitational. The overall process is tied
to the natural hydrologic cycle of evaporation and condensation in the earth atmosphere which
redistributes water from lower elevations (sea level at the oceans) to the higher elevations on the
land. The redistrib
ution increases the potential energy of the water which then flows back to the
rivers and then to the oceans under the influence of gravity. Due to the rainfalls and the snow falls
the water stored or flowing at any times varies diurnally and seasonally. T
he change in potential
energy that occurs as the water makes its way back to the oceans provides an opportunity to
extract a portion of that energy in form of hydropower. Hydropower can be produced from any
change in water elevation but for practical purpo
se the tidal flows and ocean waves or currents
are classified differently.

In today’s hydropower application, changes in both potential and kinetic energy of the flowing
water are used to generate mechanical power to drive a generator to produce electric
power.
Before 1900 direct mechanical power applications were prevalent in number of industries such as
weaving, fiber spinning and grain grinding.
[8]

2.6.2

Types of Hydro
-
Power System

1.

Impoundment

which uses a natural or manmade dam for maintaining a water supply
.




21



Fig
ure

2
.3

An impoundment hydro
-
power plant dams water in a
reservoir

[
40]
.

The most common type of hydroelectric power plant is an impoundment facility. An
impoundment facility, typically a large hydropower system, uses a dam to store river water in a

reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn
activates a generator to produce electricity. The water may be released either to meet changing
electricity needs or to maintain a constant reservoir level.

2.

D
iversion

or a run of river system that intercept a portion of natural flow of a river without
employing an artificial dam.




22



Fig
ure

2
.4

The Tazimina pr
oject in Alaska[40]

This is an example of a diversion
hydropower plant. No dam was required

3.

Pumped
Storage

is an application which depends on the demand of electric power. It is used when
the demand of electric power is low water is pumped from a source to storage

reservoir located at
a higher elevation. During peak l
oad period, the stored water is
rele
ased, passing through a
hydraulic turbine to generate power.

Facilities range in size from large power plants that supply many consumers with electricity to
small and micro plants that individuals operate for their own energy needs or to sell power to
util
ities.





23


2.6.3

Principle


The main device used to capture hydro energy is the hydraulic turbine, which produces rotating
shaft work that powers the electric generator. Although there are many types of hydraulic
turbines, the basic approach is similar. They use th
e change in potential energy to increase the
fluid pressure and/or velocity and then deposit a portion of this hydraulic or kinetic energy on a
turbine bucket to rotate a centrally located shaft. Thus, as the fluid passes through the turbine the
change in
its potential energy is continuously converted mechanical power. The step to electric
power is straightforward and is achieved by connecting the rotating shaft from the hydraulic
turbine to an electric generator. The hydro generator operates in similar man
ner to those used in
fossil
-
fired,

gas turbine or steam or even wind power applications . Hydro machines tend to be
larger and slower in rotation speed than vapor or gas turbo expanders and may be oriented
vertically or
horizontally

[1]
.

The overall power
that can be extracted from any device will depend on the available potential or
kinetic energy as reflected by magnitude of the total (static plus dynamic) hydraulic head and
conversion efficiency of the particular hydraulic turbine/ device


electric gene
rator combination.
Power output can be represented by a simple formula.

Power = (total hydraulic head) x (volumetric flow rate) x (efficiency)


=
(

gZ + ½
) x Q x

(2.6)

The first term on the right hand sidecontains the static head

gZ and the dynamic head




24



½ p

contributions in units kg/m
. Q is the volumetric flow
rate in units

. Z is the net
height of the water head in “m”,

is the density of water in kg/
and g is the acceration due to
gravity 9.8 m/

and

is the difference in square of the inlet and
existing fluid velocity
across energy converter. A is the cross
-
sectional area of energy converter that is open to flow. For
the hydro installations that are impounment structure with the static head providing the energy,
the dynamic head given by ½

term is effectively zero. For a low head run of river system
the dynamic head could be comparable to or greater than the static head,

gZ.

The efficiency of the conversion process is represented by term

≤ 1 which captures the losses
that occur due to friction and other disspatative effects . The latest state of art technology turbine
generator efficiencies can approch 0.9 for large flow machines

2.6.4

Conversion Equipment a
nd Civil Engineering Operations


Th
e natural condition that exist at site, including surface topography, river flows, water quality
and annual rainfall and snow fall determines the paticular design for a hydropower installation.
When suiatble hydraulic heads are not present , dams are const
ruction across the rivers to store
water and create the hydraulic head needed to drive the turbo machinery. Dams are typically
designed to last for 50 to 100 years and, as such, are constructed of durable materials such as
reinforced concrete, earth and c
rushed rock. There are several design approches that are used for
concrete dams, including solid and hallow, gravity and arch geometries. On life cycles basis the
CO2 emmissions associated with the production of concrete for dams should be considered, many

of the largest disasters associated with the energy system and their infrastructure has been a result



25


of dam failure. Due to improved construction methods and materials and new technology for
diagnostic testing the realiablity and intergerity of dam struc
ture has improved drasstically

[1]
.

In addition to the actual dam strcture there are number of other major factors of design to be taken
into consideration. Foe example turbine inlet manifold or penstock which usually include screens
to keep debris and
fish out from entering the turbine and the discharge or tailrace system must be
designed to maintain the hydraulic head and minimize the effects of sedimentation and silt
buildup.





Fig
ure

2
.5

The

characteristic components of hydroelectric pla
nt

[40]






26



2.6.5

Potential for Growth

Although hydropower is currently the largest and most important producer of electricity from
renewable energy source with over 600Gwe of capacity and 2600TWhr annually its future role is
less certain in long term. While the potential for adding additional
hydropower stations
worldwide is substantial in terms of availability and reasonable capital investment but the other
factors like environmental related concerns related with mega
-
scale projects that involve dams
and their subsequent land inundation pose s
ubsequent barriers to deployment and growth of
hydropower as a renewable energy resource.

Environmental concerns can be addressed by accelerating the level of scientific attention being
directed at by achieving quantitative understanding the impacts and b
enefits of hydro and to
develop me technologies that will mitigate these effects. More sustainable opportunities can be
achieved from hydropower system but one must keep in mind the low level of R&D support for
such undertakings.

Advance technology needs c
an be divided in to 2 categories a) near term improvements and
improvements for the existing hydro stations to address varies issue such as fish migration and
oxygen depletion issues and the b) long term innovations for utilizing low head and run of wat
er
resources in an environmentally and economically sustainable manner.
[9]

Near term improvements
-

Many people have this perception that as hydropower is a mature
technology with sustainable capital investment in place it cannot be influenced by modern
tec
hnology but this is not true, the problems of fish migration and oxygen depletion are being



27


dealt with number of new technological approaches such as understanding the reason for cause of
such high level of mortality rate of young fish, followed by the tur
bine design which is more fish
friendly. Various research labs have been working on improving hydro technology for a few
years and the research has led to better understanding of what causes fish morality in hydro
turbines and has generated a lot of innova
tions that would reduce the problem.

Advanced modeling methods employing computational fluid dynamics have identified location
and conditions inside existing turbines that are problematic to successful fish migration. The main
injury to the fish is due to
rapid pressure changes, impingement and abrasion of turbine blades
and damage induces by
cavitation’s
. One optimistic approach that causes both CFD modeling and
experimental validation methods with electronically tagged fish has resulted in proposed design

of internal turbine bladding that could be retrofitted in Fransis and Kaplan units to reduce
morality. Another important aspect of these proposed fish friendly retrofits is that the conversion
efficiency would be preserved or even increased. Another conce
pt of designing a new turbine is
worked on where the turbine would use a centrifugal fuel concept that would facilitate migration
of small fish and operate at efficiencies which is
approx.

90%.

Oxygen depletion in the water discharge from hydro turbines al
so is a problem in installations.
Aerating weirs and turbine runners are being developed by scientist to increase oxygen content.
Development is being carried out on smaller dams with existing low heads that increase power
output with little environmental
damage.

LONG TERM INNOVATIONS
-

If the
ultra
-
low

head (1 m) or run
-
of
-
river energy converters
concepts could be developed economically then there could have been large jump in potential of



28


hydro power which would fulfill if not all but desirable sustainabil
ity attributes of energy system.
These concepts would allow for fish migration, maintain the natural flow and flooding cycles of
river by eliminating or minimizing impoundment and keep water quality at high levels.

Matrix turbines are specially designed fo
r
ultra
-
low

heads turbines are being considered by a
number of groups. Many researches are going on to develop several low cost alternatives such as
slow rpm turbines made of composite plastics that operate efficiently with
ultra
-
low

heads (less
than 1 m) and can capture both the potential and kinetic energy of flowing water in rivers or tidal
basins. Another development is design of high rpm, air driven Fransis turbine that are powered by
hydraulically activated chambers that compres
s air using river flows and using low hydraulic
heads (1
-
3m).

Schneider and associates have taken a different approach in which a river or tidal basin’s hydro
energy is captured directly as kinetic energy ½


using a hydro
-
engine that consist o
f a
horizontal cascade of foils that are mechaniically connected to the drive mechanism by looping
around two axles resembling a venetian blind structure. Schneider hydro
-
engine utilizes natural
river flows enhanced by two hydraulic heads (less than 3m) wh
ile keeping fluid pressure changes
and velocity and accelration levels within safe ranges for fish passage. Some other renouned
companies are also working on ultra low head machines employing matrix turbines and a desired
power wheel concept. Although init
ial testing of these concepts have been successful but
durability, validated performance including efficiency and to ensure reasonable cost remians to be
done before these advanced machines

will be deployed commercially.[10]





29


2.7

Solar Energy

Thought
-
out the h
uman history, solar energy has been utilized for domestic use in heating and
cooking. . In general, its ubiquitous nature and ability to be effectively used over a range of scales
makes solar the popular choice among popular renewable enthusiast. The Sun’s

energy incident
on the earth is the intrinsic source for many forms of renewable energy (including wind, ocean
thermal, and bio energy) and over a long time scales all of the fossil energy.

Solar
radiation
, along with secondary solar
-
powered resources such as
wind

and
wave power
,
hydroelectricity

and
biomass
, account for most of the available
renewable energy

on earth. Only a
minuscule fraction of
the available solar energy

is used.

Solar technologies are broadly ch
aracterized as either
passive solar

or
active solar

depending on
the way they capture, convert and distribute solar energy. Active solar te
chniques include the use
of photovoltaic panels and
solar thermal

collectors to harness the energy. Passive solar techniques
include orienting a building to the Sun
, selecting materials with favorable
thermal mass

or light
dispersing properties, and designing spaces that
naturally circulate air
.

[4]


The Sun’s energy incident on the earth is the intrinsic source for many forms of renewable energy
(including wind, ocean thermal, and bio energy) and over a long time scales all of the fossil
energy.

2.7.1
Resource

Assessment

As we all appreciates the variability of suns intensity during the day as the sun passes overhead
and as its radiations encounters through the clouds and reaches the earth surface. Seasonal
variations are then superimposed on the top of

these diurnal changes. Fortunately the daily and
seasonal movements of the sun are both predictable and known in precise mathematical form.



30


Changes in weather are less regular, but can be averaged from estimating the solar potential in
different regions.
The intermittent and variable characteristics of the solar energy must be
reckoned with to make effective use of it as a source of thermal and electrical energy. Passive and
active storage is always coupled to the solar energy system.

The intrinsic source
of the sun’s energy is a direct result of thermonuclear fusion of hydrogen
nuclei to form helium, which occurs at phenomenally high rate of about 4000000000 Kg of mass
conversion per sec. Solar fusion reaction results in temperature of about 6000 degree Ce
lsius at
the sun’s surface, induces a large solar radiative flux that travels 93 million miles to the earth.

The distribution of solar energy flux that intercept the earth is a strong function of wavelength of
incident light, as the variation in the absorp
tion and reflection characteristics of different
molecules contained in the earth’s atmosphere, the distribution changes from the top of the
atmosphere to the earth surface. Most of the short wavelength ultraviolet is absorbed by the
oxygen (O2), ozone (O3
) and nitrogen (N2) in the upper atmosphere while water (H2O) and
carbon
-
mono
-
oxide (CO2) captures a good portion of the longer wavelength radiation in the
visible and infrared region.





31




Fig
ure

2.6

Schematic of Incomi
ng solar energy [41]


About half of t
he incoming solar energy reaches the Earth Surface

The Earth receives 174

petawatts

(PW) of incoming solar radiatio
n (
insolation
) at the upper
atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by clouds,
oceans and land masses. The
spectrum

of solar light at the Earth’s surface is mostly spread across
the
visible

and
near
-
infrared

ranges with a small part in the
near
-
ultraviolet
.

Earth’s land surface,
oceans

and atmosphere absorb solar radiation, and this raises their
temperature. Warm air containing evaporated water from the oceans rises, causing
atmospheric
circulation

or
convection
. When the air reaches a high altitude, where the temperature is low,
water vapor condenses into clouds, which rain onto the Earth’s surface, comple
ting the
water
cycle
. The
latent heat

of water condensation amplifies convection, producing atmospheric



32


phenomena such as
wind
,
cyclones

and
anti
-
cyclones
. Sunlight absorbed by the oceans and land
masses ke
eps the surface at an average temperature of 14

°C
. By
photosynthesis

green plants
convert solar energy into
chemical energy
, which produces food, wood and the
biomass

from
which fossil fuels are derived.

Table 2.8

Yearly solar fluxes and Hum
an
energy Consumption

[4]

Yearly Solar fluxes & Human Energy Consumption

Solar

3,850,000

EJ

Wind

2,250

EJ

Biomass

3,000

EJ

Primary energy use (2005)

487

EJ

Electricity (2005)

56.7

EJ

The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately
3,850,000 (EJ) per year. In 2002, this was more energy in one hour than the world used in one
year. Photosynthesis captures approximately 3,000

EJ per y
ear in biomass. The amount of solar
energy reaching the surface of the planet is so vast that in one year it is about twice as much as
will ever be obtained from all of the Earth's non
-
renewable resources of coal, oil, natural gas, and
mined uranium combin
ed.

In mathematical terms the capture efficiency (η solar) of the solar collector can be represented as




33


η solar = useful energy recovered/ total solar flux incident on the collector x 100%

Recovered energy can be in the form of thermal energy (heat) or el
ectrical energy (current x
voltage). In thermal energy recovery applications, efficiencies can be high ranging from 30
-
60%
or more whereas in photovoltaic efficiencies are considerably low 8
-
15%.

An operating variable that can influence the capture efficie
ncy of the solar collector is the
pointing error ψ which can be represented as


Ψ = pointing error = €
-

β in degrees

And α

= collector tilt relative to the latitude = β


φ


Where


β = tilt angle of the collector in degrees from the horizontal

Φ =
latitude in degrees, € = pointing angle of the sun, θ = altitude angle in degrees

ω = azimuth in degrees

The altitude angle θ and azimuth ω are defined as the angle of the sun above the horizon and the
angle from true south, respectively. The hourly variation of the sun’s position are usually
represented by the azimuth or hour angle, ω that varies about 15 de
grees per hour and ranges
from 0 to a maximum value that changes depending on the time of the year. The value of ω is
zero at solar noon when the sun reaches its highest position in the sky for its specific location and
reaches its maximum value when the s
un sets below the horizon. The maximum value is less than
90 degrees in fall and winter months and greater than 90 during spring and summer months.



34


Seasonal variations are usually given as a function of declination angle δ, which provides a
qualitative mea
sure of tilted earth’s position relative to the sun as the earth moves around the sun
annually. Value of δ is zero at autumn and vernal equinoxes September 21 and
March

21
respectively and in northern latitude +23.5 degrees and at summer solstice on june21

and
-
23.5
degrees at

winter solstice on December 21.





Fig
ure

2
.
7

Sun’s
Position Vector[42]




The sun’s position vector relative to the earth
-
center= frameⰠin=the=earth
-
center=frameⰠCMⰠIb=an搠Cm=re灲esent=three=潲th潧潮al= axes=fr潭=the=
center=潦=the
=
earth=灯pnti湧= t潷ar摳=meri摩anⰠ east=an搠m潬arisⰠ
res灥ctively.
=




35





Fi
g
ure

2
.8

Collector

reference frame[42]







In the collector
-
center frame, the origin O is defined at the center of the collector

surface

and it coincides with the origin of earth
-
surface frame. OV is defined as vertical axis

in this coordinate system and it is parallel with first rotational axis of the solar collector.

Meanwhile, OR is named as reference axis and the third orthogonal axis,

OH, is named as

horizontal axis. The OR and OH axes form the level plane where the collector surface is

driven relative to this plane. The simplest structure of solar collector that can be driven in

two

rotational axes: the first rotational axis that is parallel with OV and the second rotational

axis that is known as EE′ dotted line (it can rotate around the first axis during the sun tracking

but must always remain perpendicular with the first axis). Fro
m the diagram, θ is

the amount of rotational angle about EE′ axis measured from OV axis, whereas β is the

amount of rotational angle about OV axis measured from OR axis. Furthermore, α is solar

altitude angle in the collector
-
center frame, which is express
ed as π/2
-

θ





36



2.7.2
Passive

and Active Solar Thermal Energy for the Buildings

About one third of the energy we consume is used to heat, cool and humidify/dehumidify the
building we live and work in. In developed countries and mega cities worldwide
people send 80%
of their time inside such buildings. As such indoor air quality can be significant health issue that
is strongly linked to the energy use. The amount and type of energy required to condition
buildings depends on the dependent on the climati
c conditions of the region where they are
located. Solar thermal energy utilization in buildings usually involves one or more of the
following approaches:

1.

Passive thermal gain and reuse

2.

Active capture of solar heat using solar collectors

3.

Direct and indirec
t day lighting.

The first two require the same type of thermal energy storage and a means for distributing the
thermal energy. All require in corporation in the design of the building. In most instances both
direct and diffuse solar radiation are collected

on a flat surface exposed to the sun radiation where
the absorber area is equal to the collector area. In some cases a concentrating approach may be
used to achieve higher storage temperatures where the collector is larger than the absorber area.

In addit
ion to capturing a portion of solar spectrum for use, proper building design should strive
for high performance by maximizing energy efficiency. This approach usually leads to increased
building insulation (higher R values, reduced air infiltration and lea
kage) in the walls floor and



37


roof and better window placements and materials. There are tradeoffs with the given the cost
associated with the reducing heat losses or heat gains that must be balanced against the benefits of
having lower energy demands. For
instance indoor air quality can be compromised in a
well
-
insulated

building, with air infiltration rates. In these cases properly designed system for air
exchange with energy recovery are needed. Nonetheless it is safe to assume that a building that
has a
passive or active solar thermal system is also designed for high energy efficiency.

Passive System

The basic approach with passive system is to utilize the building structure to capture solar heat
and transmit light, where appropriate, to reduce artificia
l lighting needs. The natural characteristic
of certain building materials, such as stone, cement or concrete and adobe clay are ideally suited
to capture and store heat. In the daily cycle, heat is collected during the day and transferred by
natural conve
ction of air or water to condition the inside of the building over a period of time that
extends into the evening.

Location and orientation relative to the sun’s movement is important in determining exactly what
type of passive design will work best. In
addi
tion the type of building gives

different challenges.
For instance the windowless or closed commercial office building that are loaded with people,
lighting and fixtures and their computer workstation represent a discrete set of small heat sources
that

introduce a substantial cooling load even in winter months. Residential units with a lower
density of people greater opportunity for natural ventilation and day lighting are better suited for
classical passive design.




38


Adobe and Trombe walls represent popu
lar options for certain locations. These options take
advantage of relatively high heat capacity and lower thermal diffusivity of the solid stone and
masonry material to store and transfer heat to the inside of the building. Normally the wall is
placed on
the south facing side of the building and may be placed and may be coated with black
or darkened surface to increase the solar absorptivity and covered with glass on the side facing
outward with an air space between it and the solid wall. To reduce heat lo
sses the back and side
surface may be insulated. A roof overhanging is often used to limit the amount of solar gain
d
uring the hotter summer months.
Most recently the variation of Trombe wall concept has made
them more flexible and adaptable to the wider v
ariety of building applications. The transpiring
wall is one such idea which was introduces by scientists at National Renewable Energy
Laboratory, transpiring wall has been effective for both passive heating and cooling applications.




Fig
ure

2
.9

Modifie
d Trombe Wall
[43]




39




Hot Air

Fig
ure

2
.10

Transp
ired Collector [43]


Active System

Active solar thermal system is usually applied in residences and commercial buildings for
providing hot water, heating and air conditioning. What makes them different from passive
system is that they employ collectors that capture solar energy and rapidly
transfer thermal energy
to circulating working fluid which can be used immediately in the dwelling or stored for later use.
Control systems are almost always employed to turn circulating pumps on and off and to divert
fluid to storage vessel when collector

temperature reaches specified levels. Active system has
been in operation for over 80 years mostly employed in homes. Here we see a flat plate collector
that consists of a selectively coated metal plate with attached channels. A circulating fluid is
heate
d as it is pumped through the channels on the collector and then passed through coil
contained inside of a hot water storage tank where it transfer heat to the water in a tank, an
antifreeze mixture (typically a propylene glycol
-

water mixture) is used as
the working fluid to
avoid freezing and subsequent damage to the collector system during the winter. Alternatively
water could be employed with a gravity drain back loop to eliminate concerns about freezing.




40


The most flat collectors are modules that can b
e mounted on the roof or can be build in the roof
structure. Each one contains a metal receiver that has been coated with special material to
produce a selective surface that has a high absorbtivity for solar energy in the visible and
ultraviolet region
at shorter wavelength and low emissivity in longer wavelength, thermal infrared
region. This selectivity lowers the radiative heat
loss from

collector surface. As many materials
have been used as selective surface a favored material is black chrome oxide C
r2O3. To reduce
the heat losses from the collector, insulation surrounds the sides and
back,

and one or two
transparent glass or plastic plates are positioned on the top side of the collector with an air gap of
1 cm or more. The choice of a transparent cov
er material is based on a number of factors,
including its ability to transmit solar energy with small losses, durability to weather and cost.
Tempered glass is often selected for solar hot water heaters given its low cost and durability even
though it is
opaque to radiation in the infrared region. An electronic control unit regulates the
flow of working fluid and operates in response to a difference in temperature between the
measured storage tank temperature and temperature of the collector surface on the

roof.




41



Fig
ure

2.11

Solar Ho
t Water System [41]

Although the reliability of the commercial solar hot waters heater was not universally good when
they were extensively deployed in the 1970’s and early as 1980’s, today’s system are very robust,
carrying warranties of 20+ years. Beside hot water heating so
lar flat plate system can be used for
space heating and cooling. In heating applications air is often circulated through channels in the
panel to capture the solar energy. It can then be used immediately for heating rooms by being
forced through a set of r
oom by room registers to distribute the heat or stored in a crushed rocking
bed for later night time use. Alternatively water can be used as a heat transfer fluid in a similar
manner; only difference is that the set of room radiators would be used to distr
ibute the heat. Air
has
an

advantage over water in that it does not freeze and/or cause corrosion problems, but it has
lower heat capacity and higher parasitic losses in distribution and storage system.

For cooling, both vapor compression refrigeration an
d absorption cycle can be used. In vapor
compression cycle, solar energy can be used as heat source to power a turbine in a closed loop
Rankine cycle, which in turns drives the compressor of the refrigeration cycle. A disadvantage of



42


these cycles is that t
hey need to be fairly large to have reasonable operating efficiencies. For both
large and scale cooling loads a lithium bromide (LiBr) absorption cycle can be employed. Here
solar thermal energy at temperatures 70
-
80 degrees is used to evaporate water from

the low
pressure LiBr solution in the generator section of the cycle. Heat is rejected from the system as
the water is condensed while cooling occurs in the evaporator section, again operated under
vacuum condition at about 40 degrees. The cycle is comple
ted as the LiBr solution reabsorbs the
water vapor to complete the cycle.

It is to estimate the cost for passive solar system because they often become a integral part of the
building structure. For example partial cost offsets results when a passive solar

greenhouse,
Trombe or transpiring wall is incorporated into a design of a new building. In addition
guaranteeing trouble free performance or other desirable attributes, such as enhanced day lighting
is as importance as reducing heating costs in determinin
g whether passive system are deployed.

Seasonal

storage of captured solar energy would enhance its value for space heating
tremendously.
[12]

Several innovative concepts have been proposed for using the earth sub
-
surface in form of water
contained in a con
fined aquifer or as heat rock. While both of these concepts are technically
possible there are drawbacks. For example additional cost is incurred to put such storage system
in place. Give these limitations and constraints deployment of existing passive and

active solar
heating and cooling technology for building has been severely limited by the high front end
capital cost that are incurred when the building is constructed. The potentially lower net life
-
cycle
cost for the solar system
cannot

be realized. Th
e traditional low cost of the conventional fuels and



43


base load electricity with the exception of occasional price shocks is often the single most
important factor that deflates interest in investing in energy and solar energy capture.

There are several w
ays of making solar heating system more attractive. One is to achieve lower
unit cost by improving and scaling up production levels and the other is by introducing policy
incentives. The high capital cost of solar hot water system is partly driven by limit
ed production
to the million units per year in US which would have substantial impact
-
reducing the current cost
for these systems by 30
-
40% or more to levels of $2500
-
$5000 or less, depending on the size of
the system. Introducing incentives to home owner
s of commercial operators to install a solar
system would also have an impact. Such incentives could be in form of tax credits or lower
mortgage rates.

2.7.3
Recent

Patents of Solar

Energy

Collectors

The first patent included in this review concerns an alt
erable solar collector. A solar collector of a
solar water heating system comprises a conduit formed by two circular cross
-
sectioned manifolds
running parallel with each other. The manifolds are able to rotate vertically about the central line
of the manif
olds. The manifolds have

(I). a number of T
-
shaped members

(II). a number of seal means connecting the T
-
shaped members together in a watertight way

(III). at least one heat insulating means covering outside of the T
-
shaped members and the seal
means, and




44


(IV). at least one cover means supporting and protecting the heat insulating means, as well as the
T


shaped members and the seal means inside the heat insulating means.

The solar collector also comprises a number of solar absorbers perpendicularly posit
ioned along
the conduit and connected to the side holes of the T
-
shaped members of the manifolds of the
conduit, at least one bottom support means at each side of the conduit holding the low ends of the
solar absorbers to keep them in position and at least

two connection means riding on a roof on
which the solar collector is installed to connect the bottom support means to the manifolds.

Another patent in stationary collectors concern a heliothermic flat plate collector module. The
heliothermic flat plate c
ollector module comprises a sheet metal panel, whose rear face lies
opposite to the face exposed to solar radiation. It is covered by a bonded grid type arrangement of
capillary tubes, positioned at a distance one below the other, permitting the passage of

a liquid
medium, in addition to connections for admitting and evacuating the liquid to and from the grid
-
type arrangement. The capillary tubes are attached to the rear face of the sheet metal panel by
means of a coating that encases the capillary tubes, o
r an accumulation of thermally sprayed
metal particles, which adhere to the rear face of the sheet metal panel and to the surface of the
capillary tubes.

The first invention relating to concentrating collectors concerns a parabolic trough collector,
whose

supporting structure is configured as a dual
-
shell torsion box, which increases the rigidity
of the collector. The objective of a second patent in this area is to provide a tubular cover for a
parabolic trough collector for helping accumulation of sun rad
iation more than a conventional
receiver tube and having an uptake factor of the best capability. In the case that the absorption



45


tube is provided in the tubular cover, the tubular cover of the parabolic trough collector has four
structure elements at whic
h sunlight is focused, at the absorption tube provided in the tubular
cover. Another invention on parabolic trough collectors concerns a collector which includes a
single
-
axis parabolic mirror and a receiver tube arranged at the focal point (F) of the para
bolic
mirror. The receiver tube includes an absorber tube and an outer tubular glass jacket around it. To
compensate for focusing errors in the parabolic collector and thus to reduce associated geometric
optical losses, the tubular jacket is provided by fo
ur structural elements, which focus the sunlight
on the absorber tube arranged in the tubular jacket by reflection and/or refraction. The receiver
tube is preferably arranged relative to the parabolic mirror, so that its center is displaced from the
focal
point (F) in the direction of the mirror by a distance equal to half the spacing between the
tubular jacket and the absorber tube.

In another patent, the parabolic trough collector has a receiver formed by several single absorber
tubes. The single absorber

tubes are supported by absorber tube supports and surrounded by a
glass tube. Because of different expansion behavior of the absorber tube and the glass tube during
collector operation flexible unions are foreseen between absorber tube and glass tube. In
order to
use the radiation coming to the non
-
active
-
area where the absorber tube supports and the flexible
unions are located, a mirror collar is installed. The mirror collar is able to reflect the solar
radiation, which is coming from different directions
, to the active absorber part of the single
absorber tubes even when the sun incident angle is changing. A high concentration central
receiver system and a method which provides improved reflectors and a unique heat removal
system is presented. The central

receiver has a number of interconnected reflectors coupled to a
tower structure at a predetermined height above ground for reflecting solar radiation. A number



46


of concentrators are disposed between the reflectors and the ground such that the concentrators

receive reflective solar radiation from the reflectors. The central receiver system further includes
a heat removal system for removing heat from the reflectors and an area immediately adjacent
to

the concentrators. Each reflectors use mirror, a facet and

an adhesive is disposed between the
mirror and the facet such that the mirror is fixed to the facet under a comprehensive stress
[1]
.

2.7.4
Recent

Patents of Tracking Mechanism

As we know that the tracking mechanism are required in concentrating mechanism
for following
the trajectory of the sun in the sky with certain accuracy. In fact, the concentrating collector
performance depends on the effectiveness of the tracking mechanism as any large deviations will
focus solar radiation away from the receiver.

The

first invention in this category, concerns a solar tracking mechanism utilized in connection
with a solar energy collection system. The collection system includes a light reflective shell
shaped to focus solar radiation on a radiation absorbing segment of

a tube which carries a heat
transfer fluid. The shell is pivotally mounted on a support frame. An actuator mounted between
the support frame and the shell is able to rotate the shell. A solar sensor is mounted deep within a
sighting tube which is fixed to

the shell such that a line of sight through the sighting tube is at
least parallel to the optical axis of the shell. The solar sensor generates a sensor signal which is
used as a control input to an actuator control system. End limit switches generate a l
imit stop
signals when the shell reaches maximum angular positions. The actuator control system generates
fluid flows to the actuator based on the solar sensor signal and the limit stop signals. The method
of tracking the sun includes the provision of a so
lar cell array, which activates the solar collection



47


system when solar radiation illuminating the array exceeds a predetermined threshold. This
provides a solar sensor shielded from the solar radiation except for direct, aligned radiation,
pivotally rotati
ng the shell westward based upon the solar sensor signal, stopping the shell at a
maximum angular positions, and rotating the shell westward if the shell does not reach the
maximum westward angular orientation during a predetermined daylight time period. T
he solar
energy collection system may be further configured to include a bisected shell, which is hinged
together. The shell halves can be collapsed onto each other thereby protecting the light reflective
surface and the radiation absorbing segment of the
tube carrying heat transfer fluid.

In another invention, the solar tracking mechanism is employed in relation with a solar energy
captivation system. The captivation system includes a light reflective cover, with a shape to focus
solar radiation over a seg
ment of radiation absorption from a tube that carries a heat transfer fluid.
The cover is mounted by pivot over a support structure. An actuator mounted between the support
structure and the cover is able to rotate around the cover. A solar sensor is mount
ed inside a visor
tube fixed to the cover, so that the visual line through the visor tube is at least parallel to the
optical axis of the cover. The solar sensor generates a sensor signal used as a control inlet for a
control system of the actuator. Limiti
ng switches generate end thrust block signals when the
cover reaches maximum angular positions. The actuator control system generates fluid flows in
the actuator according to the solar sensor signal and to the end thrust block signals. The sun
tracking met
hod includes also an arrangement of solar cells, actuating the solar captivation
system when the solar radiation that illuminates the arrangement surpasses a predetermined
threshold value. In this way the solar sensor is protected against solar radiation,
except from
direct radiation, aligned radiation, turning with pivot the cover to the west, according to the signal



48


of the solar sensor, stopping the cover in maximum angular positions and turning the cover to the
west if the cover does not reach the maximu
m angular orientation to the west, during a
predetermined period of daylight. The solar energy captivation can also be configured to include
a bisected cover joined by means of hinges. The cover halves can be folded one against the other
to protect the lig
ht reflective surface and the radiation absorption segment of the tube that carries
the heat transfer fluid.

2.7.5
Conclusion

It is evident from the above discussion that a large variety of collectors have been developed over
the period of time, which can
be used in variety of applications depending from the temperature
variation. Some areas in the field of solar energy are fully developed and needs less attention like
the flat plate collectors and parabolic collectors but still a lot of research is require
d in this field to
make it one of the major source of energy production. The major focus of the research should be
application based focusing on the particular application like pharmaceutical application where
solar reforming of low hydro
-
carbon fuels such

as LPG and natural gas into syngas which can be
used in gas turbines for better efficiency and manufacture of solar aluminum which is a very
energy intensive process, moreover the production of solar zinc which is a very valuable
commodities. Solar photoc
hemical process is a detoxification technology that can provide
environmental waste management industry with a powerful tool to destroy waste with clean
energy from the sun. The approach of research is more of application based rather than general
based ap
plication. The research on new materials for reflectors and heat absorption is important
for development in this field. The objective is to create materials with high reflectivity
approaching unity and high heat absorption and low emittance as to enhance t
he thermal behavior



49


of solar energy collectors. The ongoing research is the use of nanotechnology in various areas of
material science for more efficient solar conversion by employing
Nano
-
structured collectors on
the solar energy collectors.


















50


Chapter 3

WIND ENERGY

3.1
What is Wind Energy?

Wind power is the conversion of
wind energy

into a useful form of energy, such as using
wind
turbines

to make electricity,
wind mills

for mechanical power,
wind pumps

for
pumping water

or
drainage
, or
sails

to propel ships. Humans have been using wind power for at least 5,500 years to
propel
sailboats

and
sailing ships
.
Windmills

have been used for irrigation pumping and for
milling grain since the 7th century AD in what is now
Afgha
nistan
,
India
,
Iran

and
Pakistan
.

In the United States, the development of the
"water
-
pumping windmill"

was the major factor in
allowing the farming and ranching of vast areas otherwise devoid of readily accessible water.
Wind pumps contributed to the expansion of rail transport systems

throughout the world, by
pumping water from water wells for the
steam locomotives
. The multi
-
bladed wind turbine atop a
lattice tower made of wood or steel was, for many y
ears, a fixture of the landscape throughout
rural America. When fitted with generators and battery banks, small wind machines provided
electricity to isolated farms.

The first commercial machine of this genre in the US was constructed in Vermont starting i
n
1939 which had a rotor diameter of 53 m and full power rating of 1.25 megawatts of electric
wartime exigencies and cheaper alternatives led to its demise in 1945. However the oil supply
crisis of 1973 ignited widespread interest in and commitment to the
wind turbines as a potential
major component of the future electric energy generation system.




51


The Earth is unevenly heated by the sun, such that the poles receive less energy from the sun than
the equator; along with this, dry land heats up (and cools down
) more quickly than the seas do.
The differential heating drives a global
atmospheric convection

system reaching from the Earth's
surface to the
stratosphere

which acts as a virtual ceiling. Most of the energy stored in these wind
movements can be found at high altitudes where continuous wind speeds of over 160

km/h
(99

mph) occur. Eventually, the wind energy is converted through friction into diffuse heat
thr
oughout the Earth's surface and the atmosphere

[1]
.

The total amount of economically extractable power available from the wind is considerably
more than present human power use from all sources. The most comprehensive study as of 2005
found the potential o
f wind power on land and near
-
shore to be 72

TW, equivalent to 54,000
MToE

(million tons of oil
equivalents
) per year, or over five times the world's current
energy use
in all forms. The potential takes into account only locations with mean annual wind speeds


6.9

m/s at 80 m. The study assumes six 1.5 megawatt, 77 m diameter turbines per square
kilometer on roughly 13% of the total global land area (though th
at land would also be available
for other compatible uses such as farming). The authors acknowledge that many practical barriers
would need to be overcome to reach this theoretical capacity.

3.2
Wind Resources

As winds are produces by uneven solar heating
of the earth’s land and sea surface. Thus they are
a form of solar energy. On average the ratio of total wind power to incident solar power is on the
order of 2 percent, reflecting a balance between input and dissipation by turbulence and drag on
the surfa
ce. Only a small fraction is close enough to earth surface to be practically accessible and



52


only certain locations have winds that are sufficiently strong and steady to be attractive for
exploitation. The figure below shows the wind resource map for the US

as well as the potential in
the whole world.

The overview from the map shows that the best wind fields are generally near the coast and there
is commonly an overall decline in average quality in central regions of large continental land
masses. However th
e great plains of the US Midwest has extensive resources. If fully exploited
those in North Dakota and South Dakota alone can be used to generate enough electricity to equal
half of current US consumption and the totality of the US landscape could produce
several times
today’s needs.

While the potential resources are immense there are several constraints on use that limit near term
exploitation to perhaps 20% or so of total electric grid capacity

[1]
.

1.

Winds vary in speed, hence incident energy flux, during
the day and from season to
season and not necessarily in concert with demand for electricity.

2.

This non
-
dispatch able nature limits the portion of wind power in a utility generator mix,
with provision for spinning inexpensive way, at present to store energy

for future use.

3.

Other than the fortuitous proximity of pumped storage hydro installation there is no
sufficiently inexpensive way, at present to store energy for future use.

4.

The best wind fields may not be in reasonable proximity to large population cente
rs,
which necessitates the construction of expensive high
-
voltage transmission system and
results in large li
ne losses of the input energy.




53



Fig
ure

3.1 Wind Resources and Transmission Lines.
Map of available wind power for the
United States
. Color codes indicate wind pow
er density
Class [
44]


As with other solar
-
electric technology, advances in storage technologies, whether centralized or
dispersed, could greatly expand the prospects for market penetration by wind turbine generators.
Compressed air energy storage, superconducting magnets, supe
r capacitors, advanced batteries and
flywheels are potentials candidates. In addition connecting spatially dispersed winds plants, together with
an enhanced transmission system, could expand wind expand the wind generated contribution beyond
20%. The quali
ty of wind is sufficiently variable and localized that accurate long term site survey is
requisite to deployment. As soon as we see power in moving air is proportional to cube of velocity