Development in BOMBS

                                                              Abstract 

Smart bombs are the weapons capable of destroying enemy targets without the need for launch aircraft to penetrate the envelopes of the air defense systems. These essentially comprise a terminal guidance unit that guides them in the last phase to achieve pinpoint accuracy. Increase accuracy means that a single, moderate size bomb can give a better result than multiple strikes with larger ,non-guided bombs.

Smart bombs are desirable both from ethical and tactical standpoints. On ethical grounds, the military desires that each warhead deployed should strike only its intended targets so those innocent civilians are not harmed by misfire. From tactical standpoint, it wants weapons with pinpoint accuracy to inflict maximum damage on valid military targets and minimize the number of strikes necessary to achieve mission objectives. Gravity bombs with laser or GPS/INS guidance is smart bombs that have changed the face of modern warfare.

You can see how lethal and merciless smart bombs can be a realistic battlefield scenario was amply demonstrated in Gulf War and recently reiterated during US attack on Iraq. This paper will explain you the operational mechanisms, salient feature and limitations of this rapidly grooming smart bomb

Introduction

"In World War II it could take 9,000 bombs to hit a target the size of an aircraft shelter. In Vietnam, 300.Today we can do it with one laser-guided munition from an F-117."
USAF, Reaching Globally, Reaching Powerfully: The United States Air Force in the Gulf War (Sept. 1991) The United States Army began experimenting with radio-controlled remotely guided planes in the First World War, but the program had few successes. The first successful experiments

with guided bombs were conducted during World War II when television-guided bombs, flare sighted bombs and other steerable munitions, such as the 450 kg (1000 lb) AZON bomb, were developed. The Germans developed several types of steerable munitions, such as the 1400 kg (3085 lb) Fritz X, the closest Axis equivalent of the US Army Air Force's AZON device. There was even an attempt to produce a glider bomb that was released from a larger plane over the target, but the program stopped with the nuclear attacks in Japan.

The programs started again in the Korean War, where the political ramifications of nuclear war would have been unthinkable. In the 1960s, the electro-optical bomb (or camera bomb) was introduced. They were equipped with television cameras and steerable flare sights, in which the bomb would be steered until the flare superimposed the target. The camera bombs transmitted a "bomb's eye view" of the target back to a controlling aircraft. An operator in this aircraft then transmitted control signals to steerable fins fitted to the bomb. Such weapons were used increasingly by the USAF in the last few years of the Vietnam War because the political climate was increasingly intolerant of collateral damage.

Laser Guided Bombs: -

The development of laser-guided weapons has dramatically improved the accuracy of weapon guidance and delivery. With the assistance of build-up guidance kits, general GP bombs are turned into laser-guided bombs (LGBs). The kits consist of a computer- control group (CCG), guidance canards attached to the front of the warhead to provide steering commands, and a wing assembly attached to the aft end to provide lift. LGBs are maneuverable, free-fall weapons requiring no electronic interconnect to the aircraft. They have an internal semi active guidance system that detects laser energy and guides the weapon to a target illuminated by an external laser source. The designator can be located in the delivery aircraft, another aircraft, or a ground source.

All LGB weapons have a CCG, a warhead (bomb body with fuze), and an airfoil group. The computer section transmits directional command signals to the appropriate pair(s) of canards. The guidance canards are attached to each quadrant of the control unit to change the flight path of the weapon. The canard deflections are always full scale (referred to as "bang, bang" guidance).

The LGB flight path is divided into three phases: ballistic, transition, and terminal guidance. During the ballistic phase, the weapon continues on the unguided trajectory established by the flight path of the delivery aircraft at the moment of release. In the ballistic phase, the delivery attitude takes on additional importance, since maneuverability of the UGB is related to the weapon velocity during terminal guidance. Therefore, airspeed lost during the ballistic phase equates to a proportional loss of maneuverability. The transition phase begins at acquisition. During the transition phase, the weapon attempts to align its velocity vector with the line-of-sight vector to the target. During terminal guidance, the UGB attempts to keep its velocity vector aligned with the instantaneous line-of- sight. At the instant alignment occurs, the reflected laser energy centers on the detector and commands the canards to a trail position, which causes the weapon to fly ballistically with gravity biasing towards the target.

Target designators are semi-active illuminators used to "tag" a target. Typical laser guided bomb receivers use an array of photodiodes to derive target position signals. These signals are translated into control surface movements to direct the weapon to the target. An airborne detector can provide steering information to the pilot, via his gun sight, for example, and lead him on a direct heading to the target, finally giving him an aim point for a conventional weapon. Alternatively, a laser guided "smart" bomb or missile may be launched when a pilot is satisfied that the detector head has achieved lock-on and launch envelope requirements are satisfied. In either of these cases, the pilot may never see the actual target, only the aim point as indicated by the laser.

Laser designators and seekers use a pulse coding system to ensure that a specific seeker and designator combination work in harmony. By setting the same code in both the designator and the seeker, the seeker will track only the target designated by the designator. The pulse coding is based on Pulse Repetition Frequency (PRF). The designator and seeker pulse codes use a truncated decimal system. This system uses the numerical digits 1 through 8 and the codes are directly correlated to a specific PRF. Dependent upon the laser equipment, either a three digit or a four-digit code can be set. Coding allows simultaneous or nearly simultaneous attacks on multiple targets by a single aircraft, or flights of aircraft, dropping laser guided weapons (LGWs) set on different codes. This tactic may be employed when several high priority targets need to be expeditiously attacked and can be designated simultaneously by the supported unit(s).

Fire control laser systems are laser rangefinders (LRFs) and laser designators (LDs). These laser systems can be far more harmful to the eye than laser training devices such as MILES and Air-to-Ground Engagement System/Air Defense (AGES/AD) laser simulators. Consequently, fire control lasers require control measures to prevent permanent blindness to an unprotected individual viewing the laser system from within the laser beam.

                                                                        Development:-

Laser-guided weapons were first developed in the United States in the early 1960s. The USAF issued the first development contracts in 1964, leading to the development of the Paveway™ series, which was used operationally in Vietnam starting in 1968. Although there were a variety of technical and operational problems, the results were generally positive. LGBs proved to offer a much higher degree of accuracy than unguided weapons, but without the expense, complexity, and limitations of guided air-to-ground missiles like the AGM-12 Bullpup. The LGB proved particularly effective against difficult fixed targets like bridges, which previously had required huge loads of "dumb" ordnance, and large numbers of sorties, to destroy.

It was determined that 48 percent of Paveways dropped during 1972–73 around Hanoi and Haiphong achieved direct hits, compared with only 5.5 percent of unguided bombs dropped on the same area a few years earlier.^[1] The average Paveway landed within 23 feet of its target, as opposed to 447 feet for gravity bombs.^[1] The leap in accuracy brought about primarily by laser guidance made it possible to take out heavily defended, point objectives that had eluded earlier air raids. The most dramatic example was the Thanh Hoa Bridge, 70 miles south of Hanoi, a critical part crossing point over the Red River. Starting in 1965, U.S. pilots had flown 871 sorties against it, losing 11 planes without managing to put it out of commission. In 1972 the “Dragon’s Jaw” bridge was attacked with Paveway bombs, and 14 jets managed to do what the previous 871 had not: drop the span, and cut a critical North Vietnamese supply artery.

In the wake of this success, other nations, specifically the Soviet Union, France, and Great Britain, began developing similar weapons in the late 1960s and early 1970s, while US weapons were refined based on combat experience.

The USAF and other air forces are now seeking to upgrade their LGBs with GPS guidance as a back-up. These weapons, such as the USAF Enhanced Guided Bomb Unit (part of the Paveway™ family), use laser designation for precision attacks, but contain an inertial navigation system with GPS receiver for back-up, so that if the target illumination is lost or broken, the weapon will continue to home in on the GPS coordinates of the original target.

                                                              Problems And Limitations:-

While LGBs are highly accurate under ideal conditions, they present several challenges for successful use, making them somewhat less than the "silver bullet" sometimes suggested.

The first problem is designation. To ensure accurate guidance, the target must be illuminated for several seconds before launch, allowing the weapon's seeker to obtain a positive lock, and the target must remain illuminated during much of the weapon's transit time. If the designator's "sparkle" is turned off, blocked, or moved, the weapon's accuracy will be greatly reduced.

For an accurate attack against a small target, uninterrupted designation is essential. But, the guidance controls of many LGBs (such as the American Paveway™ II) cause large deflections (visible as a noticeable wobble) which reduce the bomb's range. To compensate, crews will often release their weapons in an unguided, ballistic arc, activating the designator only to refine the bomb's final impact point. This is more demanding of crew and aircraft, requiring a high standard of basic, unguided bombing accuracy and more attention to the bomb's flight.

Laser designation is very sensitive and vulnerable to weather conditions. Cloud cover, rain, and smoke often make reliable designation impossible. In war conditions, many attacks have been aborted due to poor visibility.

In the 1970s and 1980s it was common for aircraft to rely on a separate designator, either carried by ground forces, operated by the forward air controller, or carried by another aircraft in the strike group. It was often deemed more practical for one aircraft to designate for its comrades. Modern conflicts and a growing emphasis on precision-guided weapons have pointed to the need for autonomous designation, and many fighter-bomber aircraft are now being fitted with designator pods to self-designate for laser-guided munitions.

Even if the launch aircraft is capable of autonomous designation, problems remain. Laser illumination can be interrupted by smoke, fog, or clouds, limiting the usefulness of LGBs in poor weather or very dusty conditions. In desert warfare, such as the 1991 Gulf War, laser designation sometimes reflected off the sand, causing weapons to home on false targets. Furthermore, the need to provide designation may leave the aircraft dangerously exposed to ground fire or enemy air support.

An additional concern is the limited "launch envelope" of an unguided weapon. The reflected laser "sparkle" can be described as a basket into which the weapon must be steered to hit the target. If the weapon is released too low or to far from the target, or in a trajectory that puts the weapon outside the seeker's field of view, it is likely to miss. Optimum altitude for an effective LGB attack is relatively high, increasing the aircraft's vulnerability to surface-to-air missile (SAM) attacks.

For these reasons, while all modern air forces have put an increasing emphasis on LGBs and other precision-guided munitions, some tacticians still see an important role for the accurate delivery of unguided bombs. During their 1981 raid on the Iraqi nuclear reactor at Osirak, the Israeli Air Force chose to use unguided Mark 84 bombs rather than laser-guided weapons because they felt the need to designate the target would leave the attackers unacceptably vulnerable.

 

Figure 1 A laser-guided GBU-24 (BLU-109 warhead variant) strikes its target

Figure 2 BOLT-117, the World’s  first laser guided bomb & Carrier

Specifications
Mission	Offensive counter air, close air support, interdiction
Targets	Fixed hard
Class	4,000 lb. Penetrator, Blast/Fragmentation
Service	Air Force
Contractor	Lockheed (BLU-113/B), National Forge (BLU-113A/B),
Program status	Production
First capability	1991
Weight (lbs.)	4,414
Length (in.)	153
Diameter (in.)	14.5
Explosive	6471bs. Tritonal
Fuze	FMU-143 Series
Stabilizer	Air Foil Group (Fins)
Guidance method	Laser (man-in-the-loop)
Range	Greater than 5 nautical miles
Development cost	Development cost is not applicable to this munition.
Production cost	$18.2 million
Total cost	$18.2 million
Acquisition unit cost	$145,600
Production unit cost	$145,600
Quantity	125 plus additional production
Platforms	F-15E, F-111F

NON- CONVENTIONAL ENERGY SOURCES

ABSTRACT

              Not only in industries but also in our economic life in general significance of energy generation or power shows a steadily increase productivity in most important industrial fields such as mining, metallurgical, civil engineering, architecture and in all types of machine construction etc. there is an impending need to make much more need to make Non Conventional Energy attain popular acclaim.  This is also very essential to preserve the conventional sources of energy and explore viable alternatives like sustainable energy (the energy which we are already utilizing but for some safety of other uses we are suddenly wasting it, that can be reutilized), solar, wind and biomass that can enhance sustainable growth.  What is more, such alternatives are environment friendly and easily replenish able.  Therefore, they need to be thoroughly exploited with a functionally expedient, energy matrix mix.

               The Stair case electricity generator is specially planned to design and fabricate the conversion unit for utilizing the available unconventional energy source. That is tremendously available energy in low intensity with ample quantity can be utilized. This machine converts reciprocating motion in to rotary motion. The rotational power is stored in flywheel & flywheel rotate alternator that generate electricity.

                This source of power can be used at the station building, platform and waiting rooms. Also by accumulating this low intensity electricity in Batteries, it can be supplied to the commercial complexes or shopping complexes near by the railway station or in big villages or in towns where there is scarcity of electric supply.

                                                                    GENERATION OF ENERGY

The development planning process designs strategies and activities to use, enhance or conserve both natural and economic goods and services. In big modern cities, economic goods and services almost completely replace the natural ones.

Energy is the prime source of all socio-economic activities of the human community. The demographic rate of growth globally and the widening spectrum of economic growth would result in demands of energy at an incremental rate of 7 to 8% annually.  This can easily support a GDP growth of 8 to 9% per annum. Projections point toward a doubling of global energy demands in the decade starting 2020.   There will be a marked shift in patterns of energy consumption whereby developing economies of the world would have a share exceeding two-third of global energy consumption by that period.

Fossil fuels' consumption would remain the major source of energy generation and globally employed power generation technologies. The apportionment of renewable energy in the entire energy supply will continue to be marginal in the real sense.  The contribution of renewable energy-excepting hydel energy and conventional biomass as a proportion of global energy output is pegged at a paltry 2%. This scenario in all likelihood is not going to be altered therefore, guaranteeing the possibility of nudging the renewable contribution up to 5% by 2020. The global sources of fossil fuel will have become dearer due to their depletion thereby, making the viability of fossil fuel plants restoring parity with the renewable sources.  60% of the cumulated energy needs world-wide would be met through renewable sources.

Growing economies, especially of Asia are gifted with sufficient resource base and non-conventional energy technologies are consistent both for grid linked energy generation and transmission in out of the way locales that are islanded from the grid.  Adaptation of technology and employing them should be pursued right from this moment to have a head start, be informed of the barriers in technology applications of the renewable variety and synergising them with the existing, traditional power production technology and T&D networks.  It is known that in coming times, wind energy will be the most cost-effective renewable resource. Yet, it is doubtful if any individual technology would hold centre-stage.

It was in the 1970s that the real potential and role of renewable energy sources was sensed and identified in India for sustainable energy growths. During the past quarter of a century, a significant thrust has been given to the development, trial and induction of a variety of renewable energy technologies for use in different sectors.  The activities cover all major renewable energy sources, such as biogas, biomass, solar energy, wind energy, small hydro power and other emerging technologies.

India has presently among the world's plentiful agenda on renewable energy. In the 8th Plan, vis-à-vis a proposal of 600 MW generations, close to 1050 MW of power generating capacity fastened to renewable energy sources was added. About 1500 MW of the total grid capacity in the country is now based on renewable energy sources. India is rated fourth in the world with a wind power capacity of 1000-1100 MW.  Small hydel power generation, which is especially ideal for remote, hilly regions, presently not exploited but holds a potential of 500 MW in today's scenario. India has an extensive cane sugar production and we are implementing the world's biggest biogases based cogeneration programmed in agglomeration with sugar mills. There is substantial leverage as regards to deducing energy from urban and industrial wastes. The National Programmes lays special emphasis on supplying energy to rural areas. Close to 2.75 million biogas plants and over 28 million upgraded wood-stoves are also in use in the country.

In the sphere of solar energy use, solar photovoltaic and solar thermal technologies are gaining immediate reception for a host of industrial and commercial applications, as well as in Non Electrified and Rural Zones (NERZ). The country has the world's largest assemblage of solar photovoltaic, consisting of about 500,000 PV systems totaling to 39 MW, and encompassing over 30 variegated operations.

There is an added emphasis on venturing into grid quality power generation Programmes oriented on solar thermal and solar photovoltaic technologies. A 140 MW Integrated Solar Combined Cycle (ISCC) Power Project is being accorded conclusive shape to be established at Methane near Jodhpur in Rajas than. This will be the first of its kind, and the largest such project in the world.

To give a fillip to power generation from renewable energy, State Governments and utilities provide remunerative power purchase agreements and arrangements for wheeling, banking and buy back of power. 12 States have so far announced policies for non-conventional energy based power generation. The Indian Renewable Energy Development Agency (IREDA), the corporate financing arm of the Ministry, is the only Agency of its kind in the world dedicated to financing of renewable energy projects. Interest rates vary from 0% to 16%, with special rates being offered for projects.

There is an impending need to make much more forays to make Non Conventional energy attain popular acclaim.  This is also very essential to preserve the conventional sources of energy and explore viable alternatives like solar, wind and biomass that can enhance sustainable growth.  What is more, such alternatives are environment friendly and easily replenish able.  Therefore, they need to be thoroughly exploited with a functionally expedient, energy matrix mix.

A revolutionary step would be the advent of renewable energy co-operatives for power vending, installation and servicing of renewable energy systems in pockets like NERZs. With a view to take a long-term perspective, and to actualize the entire scope of Non-Conventional energy sources, it is incumbent to draw up a capacious Renewable Energy Policy involving all players in the field, together with the active participation of consumers as well

In the Ninth Plan (1997-02), the accent is on according commercialization and development of entrepreneurship in all Renewable and Non Conventional Energy Schemes and Plans.  An extra power generating capacity from Renewable and Non Conventional Energy sources of about 1500 MW is envisaged.  The immediate challenge is to reconcile the reduced budgetary allocations in the 9th Plan due to fiscal control.   The Ministry of Non Conventional Energy has stated objective of propping up 24,000 MW from Renewable and Non Conventional Energy by the year 2012.

The need is however to have adequate policy framework to be in place with an aim to provide impetus through streamlining the structure of Renewable and Non Conventional Energy.  The high potential is what should spur maximum efforts. The bottlenecks are that although there are good plans, we often fall short in measuring up to meet the desired levels of optimization of our potential. If there is a strict regiment by which Renewable and Non Conventional Energy Sources are utilized, India is sure to have adequate measure of success. The Numero Uno position in Renewable and Non Conventional Energy is well within reach with a little bit of concerted effort.

STAIR  CASE  ENERGY  GENERATOR

INTRODUCTION

                               Thus we selected stair case power generator means the “Energy in motion when it is suddenly applied with a sort of obstacle, then according to Newton’s law for every action there is an equal and opposite reaction. Utilization of this reaction is the basic reason behind the selection of this project work.”

FIG 1:  the set up flow diagram

We can install generator along with the arrangement of converting the       reciprocating motion to the rotary motion. This rotary motion is further magnify using reciprocating motion in to rotary motion-belt & pulley drive. The output of pulley is attached with flywheel it stored kinetic energy and transfer to alternator which generate electricity with zero cost.

WORKING OF PROJECT

                  STAIR CASE STEP POWER GENERATOR Converters basically new concept of non-conventional energy generation. It is electro-mechanical energy generating machine. This machine converts reciprocating motion in to rotary motion. The rotational power is stored in flywheel & flywheel rotates dynamo, which generates electricity.

Here first important point is how we get reciprocating motion, which is prime input in the system. For that we use weight of stepping person on the stair case step that climbs or get down the over the overhead bridges. We put our machine underneath the stair case installing different  units below every step foot space. Each person stepping on the every foot step will press the individual unit separately. All the units are connected to the common shaft using chain and sprocket drive. For stepping moment only the energy is generated and for that instant sprocket wheel will rotate the common shaft summing up the rotating motion altogether.

                The head of rack is brought up to level beneath the stair foot plate surface. When person move on the step, the rack on it will be pushed down. The rack is attached with free wheel type pinion that rotates in one direction only. The rack & pinion arrangement convert reciprocating motion in to rotary motion.

                This rotary motion is further magnified using reciprocating motion in to rotary motion-belt & pulley drive. The output of pulley is attached with flywheel

which stores kinetic energy and transfer to dynamo which generate electricity with zero cost.

                 A "generator" and "motor" is essentially the same thing: what you call it depends on whether electricity is going into the unit or coming out of it. A generator produces electricity. In a generator, something causes the shaft and armature to spin. An electric current is generated, as shown in the picture (lighting bolt).Lots of things can be used to make a shaft spin - a pinwheel, a crank, a bicycle, a water wheel, a diesel engine, or even a jet engine. They're of different sizes but it's the same general idea. It doesn't matter what's used to spin the shaft - the electricity that's produced is the same.

The sizes of major components are flywheel is with 1m dia, 10cm rim width, and 20mm rim thickness. It is a six-armed flywheel.   Mounted on a shaft with 4/5 cm. Dia. A bicycle mechanism is arranged with the help of which limb movement of the operator is converted into rotation of big sprocket of the chain drive.   The speed of small sprocket is further amplified using G’ a speed rise gear pair.  A young lad of age group 20-25, slim stature 165cm height, speeds up this flywheel up to 800 rpm in duration of 1 minute.

      

                                                                 TRANSMISSION OF SYSTEM

                                                                                       

       

TIDAL ENERGY

ABSTRACT

Twice each day, thanks to a gravitational pull on earth from our rotating moon, the world's oceans produce powerful water currents and rising and falling tides. Humans have studied and exploited the tremendous power of the tides for millennia, including harnessing tidal power in 10^th century dams to turn millwheels for grinding flour. Forty years ago, the first tidal dams were constructed to convert tidal power into electricity. One of the first such tidal dams was constructed on Canada’s Bay of Fundy, where tides rise by as much as 12 meters (45 feet). Now, new energy technologies (NOT dams) that generate electricity from tidal currents could help produce as much electricity as the largest hydroelectric dams or nuclear and fossil fuel generating stations, without producing greenhouse gases or harming the environment. This paper focuses on need of renewable energy sources, tidal power superiority over other types of renewable energy sources. Paper also gives brief information of construction, basic components& types of tidal power plants.Information regarding turbines used in tidal plants are also given. Advantages& disadvantages of tidal power plant is also discussed. The paper also includes case study of La-Rance in France is given for more information regarding this important power source.

                                                                             INTRODUCTION

Creating power using water flow is not a new idea. A Frenchman known only as Monsieur Girard filed the first-ever patent for a wave energy device on July 12, 1799. He thought that if someone used the “motion and successive inequality of waves, which after having been elevated like mountains fall away in the following instant. . One has conceived the idea of the most overfull machine which has ever existed” (Ross 1991). This simple yet inventive idea has changed drastically since its introduction. Today, hydroelectric power, or energy produced by water, is used in various forms ranging from dams to tidal generation.

The sources for 90% of the electric energy generated today are non- renewable (Edinger 2000). Renewable sources of energy are necessary because the Earth will eventually run out of the resources to create non-renewable energy. There are three types of renewable energy sources: solar, wind, and waterpower. Both solar and wind power are drastically affected by weather variations, while tidal power varies little when the weather changes. Seawater is 832 times as dense as air; therefore the kinetic energy available from a 5-knot ocean current is equivalent to a wind velocity of 270 km/m (Blue Energy Canada 2000). Thus, tidal power generation may be the most viable of the three types of renewable sources of energy.

Tides, the daily rise and fall of ocean levels relative to coastlines, are a result of the gravitational force of the moon, the gravitational force of the sun, and the revolution of the Earth. The tides produce the electricity for tidal power by flowing in and out of turbines. A hydrostatic head or adequate water height difference on either side of the turbine is all that is necessary to run the turbine, and the turbines turn an electric generator that produces electricity. The simple idea of utilizing hydrostatic head to power turbines will be the crux of our article.

Chart illustrating the comparative energy advantage of Blue Energy’s Vertical-axis tidal current turbine system over other renewable energy options. (Courtesy, Blue Energy Canada)

BASIC PRINCIPLES OF TIDES

Gravitational Effects and the Centrifugal Force:-The interaction of the Moon and the Earth results in the oceans bulging out towards the Moon, whilst on the opposite side the gravitational effect is partly shielded by the Earth resulting in a slightly smaller interaction and the oceans on that side bulge out away from the Moon, due to centrifugal forces. This is known as the Lunar Tide. This is complicated by the gravitational interaction of the Sun which results in the same effect of bulging towards and away from the Sun on facing and opposing sides of the Earth. This is known as the Solar Tide. As the Sun and Moon are not in fixed positions in the celestial sphere, but change position with respect to each other, their influence on the tidal range (difference between low and high tide) is also affected. For example, when the Moon and the Sun are in the same plane as the Earth, the tidal range is the superposition of the range due to the lunar and solar tides. This results in the maximum tidal range (spring tides).Alternatively when they are at right angles to each other; lower tidal differences are experienced resulting in neap tides. Tidal basics

1. Most locations have two tidal cycles per day: 12 hours, 25 minutes

2. Essentially caused by interaction of moon, earth, and sun centrifugal forces

3. Diurnal tides are generated because the maxima and minima in each daily rotation are unequal in amplitude

                                                              Fig.1 Generation of Tides’

  TYPE OF TIDAL POWER PLANTS

                                                                                                                                        

• First-generation, barrage-style tidal power plants

The oldest technology to harness tidal power for the generation of electricity involves building a dam, known as a barrage, across a bay or estuary that has large differences in elevation between high and low tides. Water retained behind a dam at high tide generates a power head sufficient to generate electricity as the tide ebbs and water released from within the dam turns conventional turbines. Though the American and Canadian governments considered constructing ocean dams to harness the power of the Atlantic tides in the 1930s, the first commercial scale tidal generating barrage rated at 240 MW was built in La Rance.

• Second-generation, tidal current power production

Engineers have recently created two new kinds of devices to harness the energy of tidal currents (AKA ‘tidal streams’) and generate renewable, pollution-free

Electricity. These new devices may be distinguished as Vertical-axis and Horizontal axis models, determined by the orientation of a sub sea, rotating shaft that turns a gearbox linked to a turbine with the help of large, slow-moving rotor blades. Both models can be considered a kind of underwater windmill. While horizontal-axis turbine prototypes are now being tested in northern Europe (the UK and Norway) a vertical-axis turbine has already been successfully tested in Canada. Tidal current

Energy systems have been endorsed by leading environmental organizations, including Greenpeace, the Sierra Club of British Columbia and the David Suzuki Foundation as having “the lightest of environmental footprints,” compared to other large-scale energy system.

TYPE 1ST: BARRAGE TYPE TIDAL

POWER PLANT CONSTRUCTIONAL DETAILS BASIC COMPONENTS:

The four main components of a tidal power generation plant will be subsequently discussed. These components (as shown in Figure 2) are a tidal basin, a tidal barrage, sluice gates, and the tidal turbines themselves.

The first component of a tidal power generation plant is a tidal basin, or estuary. Finding a proper site containing an estuary is essential for the successful operation of a tidal power generation plant. One must note that the estuary will not be man-made; rather, the tidal basin will be a geographical feature that is not easily

Figure 2: Ebb generating system with a bulb turbine

replicated. A suitable estuary is typically a large body of water that is almost entirely surrounded by land with a small opening to the sea. The amount of power that a tidal power generation plant can produce is proportional to the size of the estuary (Taylor 1982).

The second component of a tidal power generation plant is the tidal barrage. This barrage looks like a wall that cuts off the estuary from the remainder of the sea. The bottom of the barrage sits on the sea floor, and the top of the barrage sits above the highest level that seawater can reach at high tide (Edinger 2000). The tidal barrage serves the purpose of cutting off seawater from water in the estuary so that water can be channeled through the wall in a beneficial manner for tidal power to be created.

 The third component of tidal power generating plants is sluice gates. Basically defined, sluice gates are areas of the barrage where water can freely flow in and out of the estuary. These gates are not always open: rather, they are controlled by the power plant operators such that water flows in and out of the estuary in a favorable method to the tidal turbines. Sluice gates do not have a uniform location on the tidal barrage.

The fourth major component of tidal power generation plants is the tidal turbines themselves. These turbines are located within the tidal barrage, and sit near the bottom of the sea floor. The turbines are designed in the same manner as a steam turbine. The turbines lie between sluice gates located on both the estuary and seaside of the tidal barrage. When these gates are opened, water rushes through the turbines, spinning the blades and creating electricity.

SINGLE EFFECT &DOUBLE EFFECT POWER GENERATION

There are two unique designs for tidal power generation plants. The first is single effect, which is also referred to as ebb generating flow. The second, more complex, design is termed double effect and will be discussed after single effect is understood. Single effect tidal power generation plants create power from water flowing through turbines in only one direction (Ross 1995). In the same way that steam turbines cannot operate if steam flows through in the opposite direction, single effect turbines cannot function unless water is run through them in a uniform direction. The tidal cycle of single effect operation is discussed below. Assume that water in the estuary is low and high tide conditions exist outside of the estuary

Figure 3: The tidal cycle for single effect turbines (Newsome 2002).

 When the water level in the sea is sufficiently high, sluice gates located away from the tidal turbines are opened and water rushes into the estuary, eventually filling the tidal basin to the level of the sea. When the water level inside the estuary reaches the water level of the sea, the sluice gates are closed and the high water sits inside of the estuary. While the water level inside of the estuary stays constant, the water level in the sea goes down and low tide conditions are ultimately reached. When the sea water level is suitably low, sluice gates located in front of and behind the turbines are opened. By opening these sluice gates, water is forced to flow through the turbine, spinning the blades and creating electricity. The sluice gates are closed when the estuary water level reaches the low tide water level of the sea. The water level in the sea rises back to high tide, and the cycle starts over again (Banal   1981).

The tidal cycle of double effect turbines (see Figure 4) is shown below. The cycle begins as the single effect cycle does, with the water level in the estuary low nd the water level in the sea at high tide conditions. Sluice gates in front of and behind the turbines are opened so that water rushes through the turbines, creating electricity. When the water level inside the estuary gets to the same level as the sea water level, the sluice gates are closed. The water in the estuary stays high, and the water in the sea will finally reach low tide conditions. When the water level in the sea is low enough, the same sluice gates in front of and behind the turbine are reopened and water flows out of the estuary through the turbines (Banal 1981).

Figure 4: The tidal cycle for double effect turbines.

Turbines that generate electricity when water flows over the blades in two directions are the largest innovation in tidal power technology. The blades are designed such that they spin in the same direction regardless of the direction that water flows over them. Allowing the blades to spin due to multi-directional flow allows double effect turbines to have a greater power output than comparable single effect turbines. Intuition tells people that double effect turbines should create about twice as much power as single effect turbines. Double effect turbines do produce more power than comparable single effect turbines: however, double effect turbines do not produce twice the amount of power that single effect turbines create (Ross 1991).

 TURBINES USED IN TIDAL POWER STATION

Tidal Turbines:

Several different turbine configurations are possible. For example, the La Rance tidal plant near St Malo on the Brittany coast in France uses a bulb turbine (figure 5). In systems with a bulb turbine, water flows around the turbine, making access for maintenance difficult, as the water must be prevented from flowing past the turbine. Rim turbines (figure 6), such as the Straflo turbine used at Annapolis Royal in Nova Scotia, reduce these problems as the generator is mounted in the barrage, at right angles to the turbine blades. Unfortunately, it is difficult to regulate the performance of these turbines and it is unsuitable for use in pumping. Tubular turbines have been proposed for use in the Severn tidal project in the United Kingdom.

In this configuration, the blades are connected to a long shaft and orientated at an angle so that the generator is sitting on top of the barrage.

Fig.5 Bulb Turbine (Copyright Boyle, 1996)

Fig.6 Rim Turbine (Copyright Boyle, 1996)

Details of Bulb turbine:

The Bulb turbine is a reaction turbine of Kaplan type which is used for the lowest heads. It is characterized by having the essential turbine components as well as the generator inside a bulb, from which the name is developed. A main difference from the Kaplan turbine is fore over that the water flows with a mixed axial-radial direction into the guide vane cascade and not through a scroll casing. The guide vane spindles are inclined (normally 60o) in relation to the turbine shaft. Contrary to other turbine types this results in a conical guide vane cascade. The Bulb turbine runner is of the same design as for the Kaplan turbine, and it may also have different numbers of blades depending on the head and water.

                                                 Fig7. Constructional Details of Bulb Turbine

Basic components of bulb turbine

- Stay cone

- Runner chamber

- Draft tube cone- stay cone

- Runner chamber

- Draft tube cone

- Generator hatch

- Stay shield

- Rotating parts

- Turbine bearing

- Shaft seal box

- Guide vane mechanism

 

The power available from the turbine at any particular instant is given by

 

Where,

Cd = Discharge Coefficient

A = Cross sectional area (m2)

G = gravity = 9.81

r = density (kg/m3)

The discharge coefficient accounts for the restrictive effect of the flow passage within the barrage on the passing water.

The equation above illustrates how important the difference between the water levels of the sea and the basin, (Z₁-Z₂), is when calculating the power produced

 

TYPE 2ND: TIDAL CURRENT POWER GENERATION

Advantages of tidal current power generation Like the ocean dam models of France, Canada and Russia, vertical and horizontal axis tidal current energy generators are fueled by the renewable and free forces of the tides, and produce no pollution or greenhouse gas emissions. As an improvement on ocean dam models, however, the new models offer many additional advantages:- because the new tidal current models do not require the construction of a dam, they are considered much less costly, they are considered much more environmentally-friendly., further cost-reductions are realized from not having to dredge a catchments area.- tidal current generators are also considered more efficient because they can produce electricity while tides are ebbing (going out) and surging (coming in),whereas barrage-style structures only generate electricity while the tide is ebbing. Vertical-axis tidal generators may be stacked and joined together in series to span a passage of water such as a fiord and offer a transportation corridor (bridge), essentially providing two infrastructure services for the price of one. Vertical-axis tidal generators may be joined together in series to create a ‘tidal fence’ capable of generating electricity.

Tidal current energy, though intermittent, is predictable with exceptional accuracy many years in advance. Present tidal current or tidal stream technologies are capable of exploiting and generating renewable energy in many marine environments that exist worldwide. It is proximal to existing, significant electro transportation infrastructure - is blessed with exceptional opportunities to generate large scale, renewable energy for domestic use and export

            TURBINES USED IN TIDAL CURRENT TYPE POWER PLANT

                                                         Fig .8 Tidal Turbine

• Vertical-axis tidal turbine– Canadian connection

A Canadian company – Blue Energy Canada Inc. – has completed six successful prototypes of its vertical-axis ‘Davis Hydro Turbine, named after its inventor, the late Barry Davis. Barry Davis trained as an aerospace engineer, working on the renowned Canadian Avro ‘Arrow’ project, then on the equally-remarkable ‘Bras D’Or’ hydrofoil project of the Canadian Navy. Barry then decided to apply his knowledge of hydrodynamics in creating a tidal energy generator. Barry received support from the Canadian National Research Council and successfully tested 5 turbine prototypes in the St. Lawrence Seaway and on the eastern seaboard. Blue Energy is presently raising funds for a commercial demonstration project of the Davis Hydro Turbine.

Figure 9: cutaway graphic depicting an array of vertical-axis tidal turbines stacked and joined in series across a marine passage.

              Tidal currents push on vertical mounted hydrofoils that apply a torque force to rotating shafts, which are coupled to generators housed just above the water level. A transportation corridor (bridge, etc.) may be constructed along the top surface providing two-for-one infrastructure service (courtesy, Blue Energy Canada Inc.).

Figure 10: cutaway graphic of a ‘mid-range scale’ (2 x 250 kW) vertical-axis tidal turbine. (Courtesy, Blue Energy Canada Inc.)

Trends in Generation Technologies:-

It has been over 30 years since the world's largest tidal power station was constructed on the Rance Estuary in France. At 240MW, it easily dwarves the 18MW

Station at Annapolis Royal, Canada which was completed in 1984 and smaller, (less than 500 kW) systems in the Bay of Kislaya and Janga Creek completed around the time of the La Rance project. Concerns over the environmental effects of barrage tidal plants since the construction of the La Rance tidal power station have lead to the development of technologies which have less impact on the environment. Two key areas of development have been in tidal fences and tidal turbines (also known as tidal mills) Tidal Fences Tidal fences are composed of individual, vertical axis turbines which are mounted within the fence structure, known as a caisson, and they can be thought of as giant turn styles which completely block a channel, forcing all of the water through them as shown in figure in operation.

                                                    Figure 11: Artists impression of a tidal fence

Unlike barrage tidal power stations, tidal fences can also be used in unconfined basins, such as in the channel between the mainland and a nearby off shore island, or between two islands. As a result, tidal fences have much less impact on the environment, as they do not require flooding of the basin and are significantly cheaper to install. Tidal fences also have the advantage of being able to generate electricity once the initial modules are installed, rather than after complete installation as in the case of barrage technologies. Tidal fences are not free of environmental and social concerns, as a caisson structure is still required, which can disrupt the movement of large marine animals and shipping. A 2.2GWp tidal fence using the Davis Turbine is being planned for the San Bernadino Strait in the Philippines. The project, estimated to cost $US 2.8 Billion and take 6 years to complete. Tidal Turbines Proposed shortly after the oil crisis of the 1970s, tidal  turbine s have only become reality in the last five years, when a 15kW 'proof of concept' turbine was operated on Loch Linnhe. Resembling a wind turbine, tidal turbines offer significant advantages over barrage and fence tidal systems, including reduced environmental effects.

Figure12: Schematic of an axial flow, seabed mounted marine current turbine

Tidal turbines utilize tidal currents which are moving with velocities of between 2 and 3 m/s (4 to 6 knots) to generate between 4 and 13 kW/m2. Fast moving current (>3 m/s) can cause undue stress on  he blades in a similar way that very strong gale force winds can damage traditional wind turbine generators, whilst lower velocities are uneconomic. Little research and development has been until taken until very recently in this area, with only the small 3kW, Australian Tyson turbine, for river systems, available commercially. Funding for a 300kW tidal turbine, manufactured by IT Power Ltd has just been funded by the European Commission and is expected to be installed during the year 2000.

 CONSTRAINTS TO TIDAL POWER GENERATION

There are also some significant environmental disadvantages which make tidal power, particularly barrage systems less attractive than other forms of renewable energy. Tidal Changes The construction of a tidal barrage in an estuary will change the tidal level in the basin. This change is difficult to predict, and can result in a lowering or rising of the tidal level. This change will also have a marked effect on the sedimentation and turbidity of the water within the basin. In addition, navigation and recreation can be affected as a result of a sea depth change due to increased sedimentation within the basin. A rising of the tidal level could result in the flooding of the shoreline, which could have an effect on the local marine food chain.

             Ecological Changes Potentially the largest disadvantage of tidal power is the effect a tidal station has on the plants and animals which live within the estuary. As very few tidal barrages have been built, very little is understood about the full impact of tidal power systems on the local environment. What has been concluded is that the effect due to a tidal barrage is highly dependent upon the local geography and marine ecosystem energy.

CASE STUDY

La Rance Tidal Generation Plant the La Rance Tidal Generation Plant is currently the world’s largest and oldest operational tidal power plant. Some brief historical and background information about the plant will first be provided, followed by the advantages and disadvantages of the plant. Background

                                                      Fig.13 La Rance Tidal Generation Plant

The La Rance tidal power plant was initially designed in 1954, but construction was not complete until 1967. This tidal power plant is so named because it sits on the La Rance River, near St. Malo, on the Brittany coast in France. Although the La Rance plant sits on a river, it has the same mannerisms as any other tidal power plant located in the sea. The La Rance plant is located on the river close enough to the sea for the river water to have tides similar to the sea tides. The enclosed estuary of the La Rance has tidal range of up to 13.5 meters this large tidal range provides a large hydrostatic head, which aids the plant’s power production. The plant has 24 separate horizontal 10 MW turbines. The La Rance plant utilizes double effect instead of single effect turbines. When all turbines are functioning, the turbines provide an overall output of 240 MW of power. This 240 MW is enough power to meet the electricity needs of about 300,000 homes (Banal 1981).

Figure 14: This shows the difference in sea

Levels at high tide on the La Rance River (“The Rance Tidal Power Plant” 2002). Plant Advantages and Disadvantages Many traits have allowed the La Rance plant to successfully generate power over the past years. During the plant’s 30 years of operation it has produced a total of 16 billion kWh and maintained an average reliability of 90%. This reliability statistic means that at any given time, only 10%, or roughly two of the 24 turbines will be inoperative. Turbine efficiency is also an issue. Efficiency is the ratio of actual power output to expected power output (Moran 2000). The operating turbines in the La Rance power plant produce an output of 95% efficiency. While this efficiency statistic seems good, it seems even better when compared to the efficiency of traditional energy sources. Traditional coal burning technology operates at about 35% efficiency (Shaw 1980).

Reliability and efficiency are just a few of the many advantages from the La Rance tidal plant. La Rance’s minimal impact on the environment also illustrates advantages of tidal power. A tidal power station does not result in any chemical or thermal pollution of the natural environment. Expected consequences from the tidal plant stem from the obstacle that a tidal barrage creates. The La Rance plant greatly impacted the environment only at initial construction. Marine flora and fauna suffered as a result of human intervention in the environment. The biological diversity in the basin recovered once the construction phase of the plant ended.

The flooding of the estuary is another environmental problem that can be caused when building a tidal power plant. Although flooding of the estuary did not Happen with the La Rance tidal power generation plant, flooding could be a major Problem elsewhere. The La Rance bas in did not flood because the plant was carefully planned and is always monitored to ensure that water levels in the estuary do not become dangerously high. People do not inhabit the area around the plant, so no homes were lost when the La Rance plant was created (Banal 1981). If people have environmental concerns about tidal power plants, they can look to the La Rance tidal power generation plant and see that it is possible to build an effective plant without destroying the plant’s surrounding environment.

The 24 turbines not only give the La Rance plant its plentiful power source, but also make it possible to build a four-lane road on top of the tidal barrage. This barrage reduced the distance from two neighboring cities from 45 km to 15 km. A bridge averaging 26,000 vehicles per day now connects these cities, once separated by the river, and traffic rises to around 50,000 vehicles per day during the summer.

Research has shown that building a bridge over a tidal power generation plant will  ost little less than the initial construction cost of the La Rance plant (Shaw 1980). If this is true, the La Rance plant serves two purposes for the price of one. Now some of the disadvantages of La Rance will be explored, although the disadvantages are minimal.

The biggest disadvantage of the La Rance was the high initial cost of construction. When built 1967, the plant cost 617 million francs, which is equivalent to 3.7 billion U.S. dollars today (Banal 1981). Although the initial cost is high, the plant has been in operation over 30 years and maintenance costs are minimal. Therefore, the plant has paid for itself over the years. Several different turbine configurations are possible in tidal power plants. For example, the La Rance uses a Bulb turbine .Water surrounds bulb turbines, making access to the turbines difficult. The regular maintenance for the turbines includes work on the turbines for 6 days every 4 years and 4 weeks every 10 years. This sort of maintenance is typical for turbine operations. Double effect bulb turbines are more difficult to maintain as a result of the incoming and outgoing flow producing extra stress on the rotors. This extra stress resulted in non-functional turbines, which led to losses in reliability. As a result, La Rance does not generally run double effect because plant operators found that running the turbines in single effect was more cost effective than running double effect (Clark 1997). Thus, double effects urbane are not necessarily the proper choice for every tidal power generation plant.

 PROBABLE SITES IN INDIA

1) Gulf of cambay: The range is 10.8m.Some of the sites on western banks are Sonari & Bhavnagar creek & sites on eastern bank are Dhodar &Kim river outfalls. His potential estimate is around 15MW. The major problem is high sliy index 5000ppm causing erosion of barrage.

2) Gulf of Kutch: The maximum range is 7.5M. Lara creek & Wank creek near Navlakhi are of attraction. Power potential is greater than Cambay.Slit charge is much smaller than Cambay.

3) Sundarban area in West Bengal: The tide range 4.8m.Power of 40MW can be produced in this area.

                                                                                                                                                          

 ADVANTAGES &DISADVANTAGES OF TIDAL POWER

 PLANT

Advantages:

1) Exploitation will in no case make demand for large area of valuable land, because they are on bays.

2) It is free from any pollution as it does not use any fuel.

3) It is much more suitable than hydropower plant as it is independent of rain.

4) It is independent on season cycle.

5) It has unique capacity to meet the peak power demand effectively when it works in combination    with thermal or hydroelectric.

Disadvantages:

1) Can only be developed if natural sites are available.

2) Transportation cost is more as sites are away from the load center.

3) The navigation is obstructed.

4) The output is varies with lunar cycle.

5) Capital cost is considerably high.

6) Supply is not continuous as it depends on timing of tides.

CONCLUSION

Advances in tidal power technology have occurred in a relatively short amount of time, and engineers have more incentive than ever to improve tidal power Generation. When many engineers began experimenting with the idea of creating electricity from the tides, tidal power was not taken seriously. Currently, the search for renewable energy sources has become serious. More and more people are committed to finding alternatives to the burning of natural resources because people realize that soon enough, other power options must be explored. They see that there   is no reason to delay the switch to another power source. Although another source of energy will be needed in the future, tidal power will not be this source. Tidal power can help ease the strain on other types of power production. The entire United States could be powered by the tides; yet the cost is more than most people would be willing to pay. So long as engineers have the ability to dream up new ideas and constantly improve on them, humanity will have some sort of power source. Tidal power has the potential to generate significant amounts of electricity at certain sites around the world. Tidal power can be a valuable source of renewable energy, although the United States electricity needs could never be met by tidal power alone. The negative impacts of tidal barrages are much smaller than those of other sources of electricity; however this reason alone is not enough to pursue implementation on a global scale. The technology required for tidal power is well developed, and the main barrier to increase the use of tides is that of construction cost. The prospect of natural resources and cost of other forms of energy will ultimately decide the future of tidal power generation.