1. HISTORICAL DEVELOPMENT AND FUTURE TRENDS IN HYDRAULIC TURBINE DESIGNHISTORYWaterwheels are considered to be the ancient version of a modernhydraulicturbine. Waterwheels were used as far back as the first century B.C. The Romans and Greeks used waterwheels to grind corn as early as 70 B.C.Eventually harnessing the power of water by means of a waterwheel spread to the rest of the ancient world and eventually throughout Europe where the early use of them was primarily limited to grinding grain andpumpingwater. Throughout the Middle Ages, waterwheels developed inhorsepowerfrom three to 50.There were four main types of water wheels.The Undershot WaterwheelThe first type of waterwheel ever devised as early as the first century B.C. was called an undershot waterwheel. The undershot waterwheel consisted of a horizontal shaft connected to a vertical paddle wheel with the lower segment of the paddle wheel being completely submerged into the stream or creek bed. The undershot waterwheel can be viewed as the prototype of animpulse turbinein that it was driven by the force of fluid striking directly against its paddles or vanes, and produced kinetic energy. The undershot waterwheel was located in rapidly flowing rivers but only had about a 25 percent efficiency rate. In the 19th century, the concept of an undershot was revisited with substantial improvements being made to its design. The Overshot WaterwheelThe overshot waterwheel came in to use around the 14th century. Also called a gravity wheel, the overshot water wheel used the force of gravity acting vertically on the water as it traveled from the top of the wheel to the bottom.It this manner, the energy source for the overshot waterwheels is potential energy because the weight of the water acts under gravity to essentially turn the wheel. As a result, the overshot waterwheel became served as the prototype for a modernreaction turbine.The overshot waterwheel was particularly well suited for use in hilly terrain, often being built right into the side of a hill as was done in grain grinding.The Pitchback WaterwheelThe pitchback waterwheel was very similar to an overshot waterwheel except that excess water typically flowed away in the direction of the rotating wheel. In an overshot waterwheel, the water would flow away in the opposite direction of the rotating wheel. The Breastshot WaterwheelThe breastshot waterwheel was developed during the Middle Ages and was a hybrid of an overshot and undershot waterwheel.Early Hydraulic Turbine DevelopmentThe leap from the use of waterwheels to modern hydraulic turbines was a lengthy, extended process that started during the Renaissance when engineers began to study the operational characteristics of waterwheels with greater scrutiny. They soon realized that more power could be harnessed if the waterwheel was actually enclosed in some type of a chamber or encasement and that only a small amount of falling water actually struck the wheel paddle or blade, leading to the loss of energy from the onrush of water not being captured. This discovery did not immediately translate into a new type of hydraulic machine however. A lack of hydraulic knowledge and the specialized tools needed to build such a machine hampered such progress well until the late 18th century. Both problems were somewhat resolved with what is considered one of the earliest reaction turbines and the precursor to todays modern hydraulic water turbine invented by German mathematician and naturalist Johann Andres von Segner in 1750. Segners archaicreaction turbineinvolved capturing flowing water on a horizontal axis inside a cylindrical box that contained ashafton a runner orrotorand then flowed out through tangential openings, while the weight of the water acted upon the wheels inclined vanes. In 1828, Claude Bourdin, a French engineer, coined the term turbine from the Latin derivative turbo which means whirling or a vortex. The term reflected the primary difference between waterwheels and the new turbines that would soon come into development that featured a swirling motion of water by passing energy to a spinning rotor.A turbine would prove to process more water, spin faster, and harness bigger heads. Another distinguishing feature of early turbines from waterwheels was they were built on a vertical axis opposite of a basic waterwheels horizontal axis connected to a vertical shaft configuration. The blades also resembled spoons or shovels, therefore, early turbines were sometimes called spoon wheels.Around the same time, a student of Claude Bourdin by the name of Benoit Fourneyron invented the first modern hydraulic turbine. His first turbine was not very powerful at only six horsepower. Another drawback was that the radial outflow of water that passed through it created a problem if the water flow was reduced or load removed. Eventually, he did master the building of larger sized turbines that could withstand higher pressures and delivered greaterhorsepower.For example, his most powerful water turbine achieved a speed of 2,300 revolutions per minute at 60 horsepower, translating into an efficiency of about 80 percent.Another significant contribution Fourneyron made to his machine was the addition of a distributor to control and guide water flow.With Fourneyrons machine, the advent of modern hydraulic turbines was well underway and the development of a number of different types of hydraulic turbines followed.The Francis TurbineIn 1849, an American by the name of James Francis built a hydraulic reaction turbine that was to be an improvement of other hydraulic turbines already operating at the time. Most of these hydraulic turbines were produced with the water entering into the runners at the machines center and then flowed radially outward. His design changed the shape of the runner blades so they curved and the water flow turned from a radial to an axial path.The Francis turbine became widely used in rivers or waterways where with water pressures or heads equivalent to 33 to 328 feet (10 to 100 m). The Pelton TurbineIn the mid 1800s, another American by the name of Lester Allen Pelton invented a hydraulic turbine for use in water heads of 295 to 2,953 feet (90 to 900 m).With the Pelton turbine the water could be channeled from a high levelreservoirthrough a long duct or penstock to a nozzle. The energy of the flowing water was then converted into kinetic energy through a high-speed jet. The jet spray of water was concentrated directly onto curvedbucketsaffixed around the parameter of a wheel. These curved buckets turned the flow of water at 180 degrees and extracted momentum. Since the action of the wheel was contingent on the impulse created by the jet on the wheel rather than the reaction of expanding water, the Pelton turbine is considered to be an example of animpulse turbine. The Turgo TurbineThe Turgo turbine, also called a Half Pelton turbine was invented shortly after thePelton Wheelin 1920 by Eric Crewdson. With a Turgo turbine, the water entered on one side and then was channeled through the runner blades at a 145-degree angle before exiting out the other end. The Turgo turbine operated most effectively in water heads similar to a Pelton turbine and also sometimes featured multiple jets.Another difference between the two was that a Turgo turbine was smaller than a Pelton turbine and also proved cheaper to produce. The Kaplan TurbineThe growing demand for hydroelectric power in the 20th century spearheaded the development for a turbine that could work in small water heads of 10 to 30 feet (3 to 9 m). In 1913, an Austrian engineer named Viktor Kaplan proposed a propeller type turbine. His turbine, called the Kaplan turbine, operated very similar to a boat propeller but in reverse. He also eventually changed the blade design to swivel on an axis.Advancements in Hydraulic TurbinesThe trend in the use of hydraulic turbines today has been toward higher water heads and larger sized units. For example, Kaplan turbines are now typically used in heads of about 200 feet (60 m). Francis turbines are used in water heads of up to 2,000 feet (610 m) and the Pelton turbine is used in water head installations of up to 5,800 feet (1,700 m).The Francis turbine exists today as a hydropower reaction turbine that contains a runner and has water passages and anywhere from nine to 19 curved non-adjustable blades or vanes. When the water passes through the runner, it strikes the curved blades causing them to rotate and theshaft, connected to agenerator, immediately transmits this into rotational movement.Kaplan turbines have retained a design like a marine propeller but may also contain gates to control the angle of fluid flow through the blades. Recent developments have also sparked an increase in the number of application Kaplan turbines are being used for. Hydro sources once abandoned due to economic and environmental fallout are now applying Kaplan turbines. Interestingly enough, Kaplan turbines have even been used aswind turbines.

FUTURE TRENDSHIGHLY EFFICIENT HYDRAULIC TURBINE ON THE BASIS OF THE SPECIFIC THERMODYNAMIC EFFECT

AbstractTraditional free flow turbines slow down water stream using its kinetic energy. This article describes a method for deriving energy from a free water stream using a unique hydraulic turbine which unlike traditional hydraulic turbines speeds up the water stream using potential energy thanks to a specific hydraulic effect. The article also describes a method of mathematic calculations of output capacity of this kind of turbines. The design of a turbine which also uses this special hydraulic effect is described in the article.Keywordsenergy, hydrodynamics, turbine, flow, turbulent, hydraulic jump, ejection effect, "Froude number"INTRODUCTIONA group of engineers has constructed a hydraulic turbine to receive energy from a free flow of water (a free flow hydraulic unit). However, when its capacity was measured it was established that it generated more energy than it was designed for. It is well-known that a flow of water has kinetic energy that can be extracted (which is what free-flow turbines do ). However, it is impossible to extract all of its kinetic energy. In order to do this, the flow should be stopped completely and then it would cease to be a flow. That is why the velocity of water flow at the exit from a working unit of turbine is slower than its flow at the entrance it is precisely this difference that defines the efficiency of any facility. Considering the fact that the kinetic energy is known as being proportional to the square of the speed, and that the energy decreases by four times when the speed decreases, it will be easy to calculate that, lets say, when the water flow speed at the turbine input and output is equal to 1m/sec and 0.5 m/sec, respectively, we will be able to extract 75% of the kinetic energy from the flow.Strictly speaking, the power of the free-flow turbine is calculated by a semiempirical formula (1) (this formula can also be applied to calculate the power of wind turbines)(1)whereV- incoming flow speedS- the square of the turbines effective cross section across the flowp- moving medium densityK- constant coefficient that depends on a turbine type and is usually equal to 0.1 - 0.35This formula represents the very kinetic energy of the flow per a time unit, becauseV* S * pis right the water mass that goes through the turbine at one second and the formula (1) takes on the following form, which is familiar to us:

However, it should be considered that, according to the flow continuity condition, the flows square must increase when the outward flows speed drops. This leads to degradation in the flow evenness at the turbines outlet and an increase in turbulence, which negatively affects the units efficiency. In order to decrease these factors adverse effect in traditional turbines, expanding cones are installed at their outlets, which partly increases the efficiency.Because empirical coefficientKof the formula (1) includes the twain from the kinetic energy formula denominator, the hydraulic and mechanical efficiency coefficient of the turbine, losses per irregularity and turbulence in the incoming flow and so on, it accepts values of less than 0.3. This coefficient is measured through an empirical way by means of natural tests of a specific turbine.This coefficient is often called the WEUC, the watercourse energy utilization coefficient, by an analogy with the wind turbine WEUC the wind energy utilization coefficient.

THEORETICAL ANALYSISLets get back to our machine. As we have already mentioned, this facility produced even a greater amount of energy than the total kinetic energy of the flow. Lets try to answer the following questions. Where does this additional energy received from the facility come? Does the flow of water have kinetic energy only? (here we do not consider the internal (thermal) energy of water or the energy of the intermolecular and interatomic bonds of water as a substance.)Let us take one ton of water (with dimensions of 1m * 1m * 1m) flowing with a velocity of 1 m/s.There is no doubt about its kinetic energy, which is:(2)However, there is also pressure by the top layers of water on the bottom ones (potential energy). If we let this cube of water spread, then we can extract it. Considering that the gravity centre of the cube is at the middle of its height, that is h = 0.5 m, it is equal to:(3)This means that the potential energy of this cubic meter of water is up by almost 10 times on its kinetic energy. It is easy to calculate that, at a speed of 0.5m/sec, this difference will amount to almost 40 times!It should be noted that in the formula (3) a half of the water column height is taken as h because a separate water volumes height will decrease from the overall to zero as it will flow. For an infinite water flow with constant depth, which will be reviewed later, the incoming flows full depth is taken as water column height.Now let us imagine that we are extracting part of kinetic energy from a cubic meter of water, which is flowing within a current, and use it to move aside the cubic meter of water that follows it (downstream). That is we will speed up the downstream cubic meter of water by slowing down the upstream volume of water. As a result, a level difference arises between them and potential energy emerges in the difference between these levels, which can be extracted from the current. The following question arises: will the amount of the extracted potential energy be more, less or equal to the energy used to speed up the second cubic meter of water or, in other words, the energy expended to increase its kinetic energy?Let us resort to mathematics. As an example, we will consider a machine that is shown as a diagram on Figure 1, which makes it possible to speed up the outflowing stream of water by extracting part of the inflowing streams energy - that is, a machine with positive feedback between the energies of the inflowing and outflowing streams. By the way, a machine that works on this very principle has been invented. It is this machine that our article started with.Figure 1. Scheme of the deviceExplanations for Fig. 1:1- Working parts of the inflowing stream of water;2- Working parts of the outflowing stream of water;3- Working parts ensuring positive feedback between the inflowing and outflowing streams of water;4- Mark showing the level of the inflowing stream of water;5- Mark showing the level of the outflowing stream of water;6- Channel bedH1 Actual depth of the inflowing stream of waterH2 Depth of the outflowing stream of waterV1 Velocity of the inflowing stream of waterV2 Velocity of the outflowing stream of waterh Drop between the levels of the inflowing and outflowing streams of waterThe device works based on the following principle:The working parts of the inflowing stream1extract part of the kinetic energy from the stream and transmit it - with the help of the positive feedback3- to the working parts of the outflowing stream2, which give the outflowing stream additional acceleration.Because the amount of water entering the device is equal to the amount of outflowing water, and the speed of the outflowing stream is higher than that of the inflowing stream, then the sectional area of the outflowing stream will be less than that of the inflowing stream.Therefore, its depthH2will be less than the depth of the inflowing streamH1by the valueh. As a result of this, potential energy appears between the different levels of the inflowing and outflowing streams.The devices energy balance is as follows:(4)The total output of energy from the device is equal to the potential energy of the difference between the marks plus the kinetic energy of the inflowing stream and minus the kinetic energy of the outflowing stream. After omitting all the computations, we have:(5)or(6)whereMis the weight of the water entering the device in a unit of time, which is equal to the density of water multiplied by the active area of the inflowing stream and multiplied by its velocity.Then the most interesting aspect occurs. It can be seen that the left side of the equation, which is in brackets, will increase in a linear fashion when it depends onhor in a hyperbola when it depends onV2, whereas the right part will decrease, and in a parabola at that. Which side will gain the upper hand?Let us plot a graph showing energys dependence on the drop between the levelsh. The graph will be plotted to show the various levels of the inflowing streams velocityV1after designating it as a constant.

Figure 2. Energy's dependence on the difference in the levels and the input flow velocityIt is remarkable that the graph showing the energys dependence on the drop between the levelshhas an extremum. On the rising branch of the graph, the energy balance will be positive (the power factor > 1), i.e. the extracted potential energy will be mostly expended as kinetic energy on speeding up the outflowing stream, and the device will self-accelerate until it reaches the maximum.The energy produced by the device at this point will be several times the kinetic energy of the inflowing stream - and under certain conditions, tens and even hundreds of times!The speed of the outflowing stream will be significantly higher (2 to 3 times as higher at times) than the speed of the inflowing stream. Therefore, the kinetic energy of the outflowing stream is 4 to 9 times the kinetic energy of the inflowing stream.Furthermore, the graphs show that not everything appears to be quite right with the inflowing speed. It also has an extremum. To see this better, let us plot a 3D diagram.

Figure 3. Energy's dependence on the difference in the levels (left) and exit speed (right).However paradoxical this may seem at first glance, but the diagrams show there is an optimal speed for the inflowing stream. When it is exceeded, the devices power capacity will sharply fall. This is due to the fact that a significant amount of energy needs to be spent on speeding up a stream that is flowing fast already.One parameter has been left unaccounted for in these diagrams, the entry depthH1to be precise.But because the diagrams are three-dimensional now, to plot the output energy's dependence on this parameter, too, we will show the sequence of 3-D graphs for various values of the flow's entry depth.

Figure 4.Energy depends on three parameters: the difference in levelsh, the entry speedV1and the effective entry depthH1(0.9, 1.2, 1.5 and 1.8 )The diagrams show that depending on the entry depth, the machine's energy output grows in a non-linear fashion, almost in quadratic dependence. Below we will examine what exactly this dependence looks like.The question may arise: How does the outflowing stream, which has a shallower depth, interact with the water flow around it, which has a normal constant depth? Here we have to recall that the velocity of the outflowing stream is higher than that of the surrounding medium and this creates what is called in hydraulics hydraulic jump as a result of ejection effect, which equalises the discrepancy between the kinetic and potential energies of the two flows. This jump is in essence surf, a vortex in the flow.Let us examine in detail what happens with the flow, what the depth and velocity of the outflowing stream depend on and what conditions need to be met to produce such an effect.In all of the mathematical computations, only the Bernoulli equation (energy conservation law) and the flow continuity equation (mass conservation law) are used.Considering the fact that the turbine, which is located on the water flow, extracts some energy from this flow, the Bernoulli generalized equation for two cross-sections of the free voluntary flow the first one (before incoming the unit) and the second one (at the units outlet), without taking into consideration losses, will take on the following form:

where E - is energy that the turbine takes from the flow.Therefore, the energy released at the turbine is equal to(7)Let us defineorwhere k is a dimensionless coefficientThen(8)Let us express V2 in terms of V1 taking into account the flow continuity equation, namely H * V = const (when the flows width is constant in two clear sections). We will get the following:(9)orand(10)So the ratio of the velocities of the inflowing and outflowing streams depends only on the ratio of the height (depth) of the streams (with the width being the same).Accordingly, the formula (8) assumes the form:(11)or(12)Let us find the extreme of the energy in relation tok.To do this, let us differentiate the formula (11) on k(13)By equating (13) to zero, we getHence,(14)Conclusion: The turbine generates the maximum energy when the ratio of the levels of inflowing and outflowing streams istherefore(15)If we look up any textbook on hydraulics, for example [2], we will see that formula (15) above agrees with formula (7-49) [2], which correspond to the so-called critical depth of the flow, the depth at which a flow is in the border state between being calm (sub critical) and turbulent (super critical).But why will the depth of the outflowing stream be equal to the critical depth? The thing is that the streams energy density is minimal at the critical depth (this is exactly why it is called critical), and, as one can observe, an increase in the velocity of the outflowing stream - with the unit rate of flow being constant and, therefore, its depth decreasing yields a positive power factor (above 1).That is to say, the stream releases energy, which is partially spent on the additional acceleration of the outflowing stream through the [positive] feedback ensured by the machine. This process will continue until the power factor becomes equal to 1, that is to say until the stream enters the critical state.It is thus possible to conclude that the device described above extracts all the additional energy from a flow by bringing the outflowing stream to the critical state, that is to say to the border state where the flow turns from being sub critical to being super critical.In accordance with [2]the specific velocity head of the flow in the critical state is equal to half of its depth and the energy density of the flow is equivalent to its gross head (the sum of its potential and velocity heads).or (16)(17)where Ek is the flows energy density at the critical depth and velocity.The flow strength at the effective cross-section is equal to the flows energy density multiplied by the weight of the water passing through the effective cross section per unit of time, or unit rate of flow, i.e. V1*H1.Taking into account (15) and (17), formula (7) can be re-written as follows:

And the flow strength at the effective cross section per unit of time is(18)Or, ultimately,or(19)Knowing that the depth of the outflowing stream is equal to the critical depth, it is now possible to plot, as a function, the dependence of the generators output power on the depth and velocity of the inflowing stream.

Figure 5. The energy diagram of the sub critical and super critical states in relation to the critical state.The critical flow will be determined as a ratio of the velocity and depth and is shown as the graph (a parabola) lying at the gulley of the 3-D diagram. The flows specific energy density on this graph has been accepted as zero. The total energy of the sub critical and super critical flows are calculated relative to it. In this diagram, all the sub critical flows are on the left and the all the super critical flows are on the right.The graph and formula (19) show that the output power's dependence on the flow's entry depth is pretty complex. It grows in a quadratic fashion if it depends on the first term in the polynomial formula and in a linear fashion if it depends on the second term. It decreases by the power 5/3 if it depends on the third termEnergy balance on the exit of the turbine shows on the fig. 6Figure 6. Hydraulic jump at the exit from the deviceExplanations for Fig. 6:H1, H2 the depth (potential head) of the inflowing and outflowing streams respectively;V 12/2g, V22/2g the velocity head of the inflowing and outflowing streams respectively;E the difference between the energy density of the inflowing and outflowing streams;Lj the length of the hydraulic jump;Fig. 6 shows that there is a lack of energy density in the hydraulic jump area between the original and the emerging (after the jump) flow regimes.The simplest and most graphic example of such a turbine is the device shown in Figure 7

Two undershot water wheels linked with a feedback mechanism, which is a chain or belt drive in this instance. The feedback ensures that the second wheel rotates somewhat faster than the first one, which is what accelerates the outflowing stream of water. Also, another variant of such a turbine is presented in [1], [3], [6].

CONCLUSIONTo summarize all of the above, it can be concluded that such a machine creates a head of water for itself and is able to extract potential energy from an evenly-flowing stream of water [4],[5].In addition, analyzing the diagram on Figures 3, 4 and 5, a few important conclusions can be drawn.First of all, one can see on these diagrams that this effect exists and it is very capricious a number of conditions for the flows efflux must be strictly met, namely the proportion between the flows incoming speed and its depth. Only with the specific combination of these parameters, we can get to the diagrams peak and extract the maximum power from the flow. At these parameters insignificant deviation from the optimal values, the effect either becomes blurred, or disappears at all and it will be very difficult to find it, and it can well be mistaken for measuring errors.Secondly, it is interesting that the effect disappears when the flows kinetic energy increases (when its speed increases), or in other words, when it approaches critical or super critical state. Judging by the diagrams, the optimal speed is the speed of 1 1.5 m/sec. However, because the water flow with this speed is considered to be of low potential and it is not often used for extracting energy by free-flow turbines, there have been carried out just few experiments under such conditions and, therefore, it has not been possible to reveal this kind of effect.Thirdly, the flows incoming effective depth is very critical to the appearance of this effect. It is obvious (the left diagram on Figure 4), that if the depth is less than one meter (the overall dimensions of most of the free-flow turbines are usually less than these values) this effect is barely noticeable, commensurate with measurement errors and "spreads" in turbines hydraulic and mechanical efficiency.Fourthly, in order to reveal this kind of effect it is necessary to use special machines that have feedback between the incoming and outward flows.Also, another interesting aspect should be noted. Unlike traditional free-flow turbines, a machine working on a similar principle does not slow down the outward flow by extracting its kinetic energy, but speeds it up by extracting its potential energy.

The advantages of this technology before the conventional hydropower engineering are the following: low investment by approximate calculations the cost of electricity produced will stand at $150-$450 /kW unlike hydropower station dams where it costs more than $1,000 and traditional free-flow turbines in which case the cost will amount to 3,000 per kW and more Short commissioning terms (60-180 days after the start of construction). It takes years and decades to build a hydroelectric dam; No water reservoir is required (ecological effect). Free-flow turbines work as artificial water aerators, saturating water with oxygen, which has a favourable effect on fauna and the general ecosystem of water flow. No costs of flood damages as there will be no water reservoir; No auxiliary mechanisms and equipment are required (such as oil and compressor units, servomotors and etc.), which increases reliability; Low maintenance costs; No need to create infrastructure around the hydropower plant (motor and rail roads, settlements of constructors and operators and etc.); No need to select a dam location as the unit is mobile and can be mounted in any suitable location; Its proximity to power consumers (no need to build power transmission lines and high-voltage transformers); No risk of station flooding because of the absence of a station (like an incident in Sayno-Shushenskaya hydropower station (Russia, 2009); No risk of dam destruction because of the absence of one (there have been cases of this kind of catastrophes in the world: Malpasset dam, France 1959, Vajont dam, Italy 1963, Teton dyke, USA 1976 , Banqiao and Shimantan dam, China 1975); decentralization of power generation. A decrease in the concentration of generating facilities in one locality, which in case of an accident may cause a failure of most of the power generation network. Power density is up by 5-10 times on conventional free-flow hydropower stations; Usable in low-speed flows (between 0.2 m/s and 2.0 m/s) in which conventional free-flow hydropower stations have low efficiency. More hydropower resources are used. it can replace a great number of heat power stations running on diesel and coal, which reduce the burning of fossil fuels and CO2 emissions.

FISH-FRIENDLY TURBINE DESIGNHydropower is a tremendous renewable energy resource in the Pacific Northwest that is managed with considerable cost and consideration for the safe migration of salmon. Recent research conducted in this region has provided results that could lessen the impacts of hydropower production and make the technology more fish-friendly. This research is now being applied during a period when great emphasis is being placed on developing clean, renewable energy sources.The configuration and operation of hydropower facilities on the mainstem Columbia and Lower Snake rivers is greatly influenced by the need to recover and sustain salmon and steelhead that are protected under the Endangered Species Act. The U.S. Army Corps of Engineers (USACE) maintains and operates eight hydropower projects on the Lower Snake and Columbia rivers that form part of the Federal Columbia River Power System.As a component of a much larger effort to improve salmon passage through these hydropower projects, USACE implemented the Turbine Survival Program (TSP) to evaluate the turbine passage environment and to optimize the design and operation of large propeller-style turbines for safe fish passage. In 2004, the USACE TSP team, with support from other regional engineers and fish biologists, began developing criteria and guidance toward the design of new turbines with potential to reduce direct and indirect sources of mortality to seaward-migrating juvenile salmon. A primary focus of the design and operational changes is minimizing the differential turbine pressures and resulting risk of barotraumas, which are injuries caused by a rapid decrease in pressure.

How pressure affects fishFish passing through hydroturbines are exposed to various forces that may cause injury (e.g., shear forces, blade strike and pressure changes).1,2,3,4,5Although blade strike is one of the most apparent sources of injury, the probability of strike from a large propeller-style turbine runner blade is relatively low, especially for small fish.6However, all fish passing through turbines are exposed to various levels of pressure change. As fish pass between the runner blades, they are exposed to a sudden drop in pressure. Fish then return to near surface pressure as they exit the draft tubes and enter the tailrace. The severity of this pressure change depends on many variables, including the design and operation of the turbine and the specific route a fish follows as it passes through the turbine.The exposure of fish to differential turbine pressures can lead to barotrauma, which may include a ruptured swim bladder; eyes popped outward (exopthalmia); rupture of blood vessels (hemorrhaging); and gas bubbles (emboli) in the vasculature, organs, gills and fins.4,5Research conducted by Pacific Northwest National Laboratory (PNNL), a Department of Energy Laboratory operated by Battelle, in cooperation with and funded by USACE, has defined the relationship between survival and exposure to differential pressures that lead to barotrauma in juvenile chinook salmon. In what is the most comprehensive research on barotrauma to date, PNNL scientists have examined injuries from barotrauma among a broad range of fish sizes and conditions, pressure changes and rates of pressure change, as well as a range of total dissolved gas levels.Results from the extensive biological tests conducted by PNNL indicated the primary source of injury results from exposure to a sudden drop in pressure and the associated expansion and rupture of the fish's swim bladder.7The swim bladder is like a balloon inside the body cavity of the fish that aids in buoyancy regulation. When the swim bladder expands as a result of a rapid decrease in the surrounding pressures, it can crush the blood vessels and internal organs of the fish. In addition, rupturing of the swim bladder can cause severe injury or death as escaping gas can pop the eyes outward on the fish and tear through the organs, muscles and blood vessels.7However, if the differential in pressure change is minimized during hydroturbine passage, then mortality from barotrauma would be reduced or eliminated because the potential for excessive expansion and rupture of the swim bladder is reduced.

Fish exposed to rapid decompression can suffer from exopthalmia (eyes popped outward).

Pressure criteria for design of new turbinesUSACE is using information provided from the PNNL barotrauma studies to establish new pressure limits for replacement turbines. Applying a minimum pressure criterion will reduce the differential turbine pressures juvenile fish are exposed to and will minimize the risk of barotraumas. Selecting an acceptable limiting pressure criterion requires consideration of the acclimation depth of fish prior to turbine passage and the maximum change in pressure the fish can be exposed to without risk of injury.For application to design of replacement turbines within the Columbia River system, the likelihood of barotrauma injury and mortality to seaward migrating juvenile chinook salmon was evaluated. PNNL researchers have found that the average maximum depth at which a juvenile chinook can attain neutral buoyancy (acclimation) is about 23 feet (6.9 meters).8Based on the PNNL research, the expected mortal injury (mortality or injury highly associated with mortality) resulting from barotraumas for juvenile chinook acclimated to 23 feet with exposure to a minimum turbine pressure of 7.5 psia (50.5 kPa or atmospheric pressure) is about 29%. However, if the minimum pressure exposure for these same fish were increased to twice this level, to 14.7 psia (surface pressure, 101 kPa or 1 atmospheric pressure), the expected mortal injury resulting from barotrauma would be reduced to about 2%.

Although applying a minimum pressure requirement that eliminates the risk of barotraumas may be desirable, it must be weighed against other potentially off-setting factors, such as risk of decreased direct injury and reduced turbine efficiencies.

USACE recently contracted with Voith Hydro in a collaborative effort to design and supply two new turbines for installation at the 603-MW Ice Harbor Lock and Dam on the Lower Snake River in southeast Washington State. The contract is for the design and supply of a fixed-blade runner and one optional adjustable-blade runner.

A primary goal of this effort is to develop design guidelines and criteria to significantly reduce the risk of injury to migrating juvenile salmonids. As such, the USACE and Voith Hydro design team selected 14.7 psia (1 atmospheric pressure) as a minimum design pressure target. During the design phase, modifications to the existing stay vanes, runner, discharge ring, and draft tube geometries also are being developed and evaluated using computational fluid dynamics (CFD) models and physical hydraulic models. These tools allow designers to target safe pressure limits for juvenile fish, reduce potential for blade strike and minimize exposure to mechanical and hydraulic shear forces. As the design progresses, turbine performance is evaluated and trade-offs are assessed to assure reasonable levels of power generation and turbine efficiency are maintained.

The new turbine runners, which are about 290 inches in diameter, are being designed for a head range of 84 to 103 feet, typical of many Lower Snake and Columbia river hydropower projects. Installation of the new turbines at Ice Harbor Lock and Dam will begin in 2015. Once they are installed, USACE will conduct field tests to determine estimates of survival of juvenile fish passing through the new runners. The implementation of an acoustic telemetry study will provide appropriate passage survival estimates for comparison with existing runners. If successful, the minimum pressure design criterion and other design concepts resulting in improvements to the turbine water passageway may provide a more biologically, economically and mechanically sustainable alternative for future turbine replacements.

PNNL researcher John Stephenson observing juvenile chinook salmon inside of a hyper/hypobaric chamber used to expose fish to simulated pressure changes associated with turbine passage.

The need for barotrauma research on other speciesMost of the research on barotrauma related to dam passage has been limited to juvenile salmon, specifically chinook. Continued research is needed to determine the thresholds of pressure change to which other species and age groups of fish can be safely exposed. Some species may be at a disadvantage compared to salmon because salmon have a connection between their swim bladder and the back of their throat called the pneumatic duct. This allows them to expel gas from their swim bladder when decompressed, likely reducing injury during hydroturbine passage.7Many other species do not have this opening and are likely more susceptible to injury when exposed to the rapid pressure changes of passage through a hydro turbine.In addition, unlike juvenile chinook salmon, many other fish species add gas to their swim bladder using a bed of vasculature, which allows them to be neutrally buoyant at much greater depths.9Because these fish may enter the turbine after residing in deeper water than do downstream migrating salmon, there is a higher likelihood that these fish may experience barotrauma during turbine passage.

ConclusionDOE has a goal of adding more turbines to existing hydro infrastructure, with emphasis on environmentally sound and sustainable solutions. However, the lack of information regarding the effects turbine passage may have on non-salmonid fish species has slowed this process. As such, additional research is necessary to identify pressure tolerances of other fish species so further advances in fish-friendly turbines continue to be developed for riverine environments throughout North America and the rest of the world. Partnerships among scientists and engineers as we have described above could hasten the realization of DOE's goal.

2. a) CAN A PERSON GENERATE ELECTRICITY FROM A FAST FLOWING RIVER WITHOUT A FALLIn theory this is possible but the amount of energy available is very small in comparison to sites where thehead(fall) of water is at least 2 metres.so practically they are not recommended. b) COST OF HYDROPOWER SYSTEMHydropower projects require a capital cost of nearly Rs7 crore per MW. But the 86MW Malana hydroelectric power project in Himachal Pradesh was set up at a competitive capital cost of Rs3.75 crore per MW.