What is Hydropower?

Hydropower, hydraulic power or water power is power that is derived from the force or energy of moving water, which may be harnessed for useful purposes.

Prior to the widespread availability of commercial electric power, hydropower was used for irrigation, and operation of various machines, such as watermills, textile machines, sawmills, dock cranes, and domestic lifts.

“is power that is derived from the force or energy of moving water.”

History…

Saqia - a wheel used by the Persians to

raise water from a river to higher place. 250 BC, water power was used as a

clock. 80 BC, the Antipater of Thessalonica

wrote, "Cease your work, ye maids who labour at the mill . . . for Ceres has commanded the water-nymphs to perform your task." The work of grinding grains such as corn was automated by water power.

762 AD, water mills became popular by the Saxons in England. A millwright traveled the countryside and fixed broken mills.

1086 AD, the Domesday survey found that there were more than 5000 mills.

1400 –1500, iron works exploited the power of the water to cool the blast furnace. In Sheffield and Sussex, England iron works were employed next to the water.

1581, Peter Morise installed a water wheel under the old London Bridge. It worked on the ebb and flood tides, meaning it was reversible.

1824, the Catrine cotton mill used a water wheel and through gearing shafting and belting achieved 9000 rev/s.

1838, 28 Tide mills existed in England even though the era of steam engines was beckoning.

1882, the transmission of hydroelectric power was demonstrated

at the Exposition in Munich with direct current of 2400 volts The first central hydroelectric station of a capacity of 250 lights was installed in Appleton, Wisconsin.

1883, a hydro-electric plant was developed at Portrush in Ireland.

1885, also in Ireland, a 65 horsepower turbine was opened for the Bessbrook and Newry railway.

1900, Oliver Evans developed a completely water powered mill that handled everything from unloading sacks of grain to packing flour in turbines.

2000, water power is becoming highly implemented and extremely utilized.

A renewable ENERGY source

Hydropower is the leading source of renewable energy. It provides more than 97% of all electricity generated by renewable sources.

Why is it renewables?

• The sun provides the water by evaporation from the sea, and will keep on doing so.

• The water on the earth is continuously replenished by precipitation.

• The fall and movement of water is part of a continuous natural cycle called the hydrologic cycle.

Hydrologic Cycle:

The hydrologic cycle begins with the evaporation of water from the surface of the ocean. As moist air is lifted, it cools and water vapor condenses to form clouds. Moisture is transported around the globe until it returns to the surface as precipitation. Once the water reaches the ground, one of two processes may occur; 1) some of the water may evaporate back into the atmosphere or 2) the water may penetrate the surface and become groundwater. Groundwater either seeps its way to into the oceans, rivers, and streams, or is released back into the atmosphere through transpiration. The balance of water that remains on the earth's surface is runoff, which empties into lakes, rivers and streams and is carried back to the oceans, where the cycle begins again.

Advantages:

Emissions-free, with virtually no CO2,NOx, SOx, hydrocarbons, or particulates.

Renewable resource with high conversion efficiency to electricity ( 80+ %).

Dispatchable with storage capability. Usable for base load, peaking, and

pumped storage applications Scalable from 10 kWe to 10,000

MWe Low operating and maintenance costs Long lifetime – 50+ years typical

Disadvantages:

Frequently involves impoundment of large amounts of water with loss of habitat due to land inundation

Variable output – dependent on rainfall and snowfall

Impacts on river flows and aquatic ecology, including fish migration and oxygen depletion

Social impacts of displacing indigenous people

Health impacts in developing countries

High initial capital costs Long lead time in construction of

mega-sized projects

How Hydropower Works

Hydropower plants capture the energy of falling water to generate electricity. A dam impounds water to form a reservoir and raises the water level to create head. Water from the reservoir flows due to gravity to drive the turbine. Turbine is connected to a generator. Power generated is transmitted over power lines.

In other words, it uses a reservoir to create potential energy from the dammed water. This water flows through an intake and into a large pipe called a penstock. This boosts the power generation capabilities of the dam. The penstock feeds water into a turbine which powers a generator.

The dam is usually built on a large river that has a drop in elevation, so as to use the forces of gravity to aid in the process of creating electricity. A dam is built to trap water, usually in a valley where there is an existing lake.

Reservoir - area behind the dam where water is stored, the water there is called gravitational potential energy. The water is in a stored position above the rest of the dam facility so as to allow gravity to carry the water down to the turbines. Because this higher altitude is different than where the water would naturally be, the water is considered to be at an altered equilibrium.

Gravity will force the water to fall to a lower position through the intake and the control gate. They are built on the inside of the dam. When the gate is opened, the water from the reservoir goes through the intake and becomes translational kinetic energy as it falls through the next main part of the system: the penstock. Translational kinetic energy is the energy due to motion from one location to another. The water is falling (moving) from the reservoir towards the turbines through the penstock.

The intake includes the head works which are the structures at the intake of conduits, tunnels or flumes. These structures include blooms, screens or trash - racks, sluices to divert and prevent entry of debris and ice in to the turbines. Booms prevent the ice and floating logs from going in to the intake by diverting them to a bypass chute. Screens or trash-racks are fitted directly at the intake to prevent the debris from going in to the take. Debris cleaning devices should also be fitted on the trash-racks. Intake structures can be classified in to high pressure intakes used in case of large storage reservoirs

and low pressure intakes used in case of small ponds. The use of providing these structures at the intake is, water only enters and flows through the penstock which strikes the turbine.

Control gates arrangement is provided with Spillways. Spillway is constructed to act as a safety valve. It discharges the overflow water to the down stream side when the reservoir is full. These are generally constructed of concrete and provided with water discharge

opening, shut off by metal control gates. By changing the degree to which the gates are opened, the discharge of the head water to the tail race can be regulated inorder to maintain water level in reservoir.

The penstock is a long shaft that carries the water towards the turbines where the kinetic energy becomes mechanical energy. The force of the water is used to turn the turbines that turn the generator shaft. The turning of this shaft is known as rotational kinetic energy because the energy of the moving water is used to rotate the generator shaft. The work that is done by the water to turn the turbines is mechanical energy. This energy powers the generators, which are very important parts of the hydroelectric power plant; they convert the energy of water into electricity.

The generators are comprised of four basic components: the shaft, the excitor, the rotor, and the stator. The turning of the turbines powers the excitor to send an electrical current to the rotor. The rotor is a series of large electromagnets that spins inside a tightly wound coil of copper wire, called the stator. “A voltage is induced in the moving conductors by an effect called electromagnetic induction.” The electromagnetic induction caused by the spinning electromagnets inside the wires causes electrons to move, creating electricity. The kinetic/mechanical energy in the spinning turbines turns into electrical energy as the generators function.

The transformer, another component, takes the alternating current and converts it into higher-voltage current. The electrical current generated

in the generators is sent to a wire coil in the transformer. This is electrical energy. Another coil is located very close to first one and the fluctuating magnetic field in the first coil will cut through the air to the second coil without the current. The amount of turns in the second coil is proportional to the amount of voltage that is created. That current is then sent by means of power lines to the public as electricity

Now, the water that turned the turbines flows through the pipelines (translational kinetic energy, because the energy in the water is being moved,) called tailraces and enters the river through the outflow. The water is back to being kinetic/mechanical/potential energy as it is in the river and has to potential to have the energy harnessed for use as it flows along (movement.)

Forms Of Hydropower:Waterwheels, used for hundreds of years to power mills and machineryA water wheel consists of a large wooden or metal wheel, with a number of blades or buckets arranged on the outside rim forming the driving surface. Most commonly, the wheel is mounted vertically on a horizontal axle, but the tub or Norse wheel is mounted horizontally on a vertical shaft. Vertical wheels can transmit power either through the axle or via a ring gear and typically drive belts or gears; horizontal wheels usually directly drive their load.

Hydroelectricity, usually referring to hydroelectric dams, or run-of-the-river setups (eg hydroelectric-powered watermills)is electricity generated by hydropower, i.e., the production of power through use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy. Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO2) than fossil fuel powered energy plants.

Damless hydro, is a renewable technology based on capturing the kinetic energy of rivers, channels of chutes, spillways, irrigation systems, tides and oceans without the use of dams

Vortex power, which creates vortices which can then be tapped for energyis a form of hydro power which generates energy by placing obstacles in rivers/oceans in order to cause the formation of vortices which can then be tapped to a usable form of energy such as electricity.Vortex-induced vibrations (VIV) are motions induced on bodies facing an external flow by periodical irregularities on this flow. Vortices are then formed changing the pressure distribution along the surface.

Tidal power, which captures energy from the tides in horizontal directionTidal power is the only form of energy which derives directly from the relative motions of the Earth–Moon system, and to a lesser extent from the Earth–Sun system. The tidal forces produced by the Moon and Sun, in combination with Earth's rotation, are responsible for the generation of the tides.

Wave power, is the transport of energy by ocean surface waves,Waves are generated by wind passing over the sea surface. As long as the waves propagate slower than the wind speed just above the waves, there is an energy transfer from the wind to the waves. Both air pressure differences between the upwind and the lee side of a wave crest, as well as friction on the water surface by the wind shear stress causes the growth of the waves.

Osmotic power, which channels river water into a container separated from sea water by a semi permeable membrane.is the energy retrieved from the difference in the salt concentration between seawater and river water.

Marine current power, which captures the kinetic energy from marine currents.

Ocean thermal energy conversion, which exploits the temperature difference between deep and shallow waters.is hydro energy conversion system which uses the temperature difference that exists between deep and shallow waters to run a heat engine. As with any heat engine, the greatest efficiency and power is produced with the largest temperature difference. This temperature difference generally increases with decreasing latitude, i.e. near the equator, in the tropics.

Sizes:

Large HP - More than 100 MW feeding into a large electricity gridMedium - 15 - 100 MW usually feeding a gridMini HP - Capacity above 1MWSmall HP - Capacity 300kW to 1MWMicro HP - Capacity 0kW to 300kWPico HP - Up to 10kW, remote areas away from the grid

Types Of HP:

Hydro plants can be classified according to water flow/storage characteristics

Impoundment. The most common type of hydroelectric power plant is an impoundment facility. An impoundment facility, typically a large hydropower system, uses a dam to store river water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. The water may be released either to meet changing electricity needs or to maintain a constant reservoir level.

Diversion, sometimes called run-of-river, facility channels a portion of a river through a canal or penstock. It may not require the use of a dam.

Pumped Storage. When the demand for electricity is low, a pumped storage facility stores energy by pumping water from a lower reservoir to an upper reservoir. During periods of high electrical demand, the water is released back to the lower reservoir to generate electricity.

Types of Hydro plant TURBINES

Impulse TurbineThe impulse turbine generally uses the velocity of the water to move the runner and discharges to atmospheric pressure. The water stream hits each bucket on the runner. There is no suction on the down side of the turbine, and the water flows out the bottom of the turbine housing after

hitting the runner. An impulse turbine is generally suitable for high head, low flow applications.

A pelton turbine has one or more free jets discharging water into an aerated space and impinging on the buckets of a runner. Draft tubes are not required for impulse turbine since the runner must be located above the maximum tailwater to permit operation at atmospheric pressure.

A cross-flow turbine is drum-shaped and uses an elongated, rectangular-section nozzle directed against curved vanes on a cylindrically shaped runner. It resembles a "squirrel cage" blower. The cross-flow turbine allows the water to flow through the blades twice. The first pass is when the water flows from the outside of the blades to the inside; the second pass is from the inside back out. A guide vane at the entrance to the turbine directs the flow to a limited portion of the runner. The cross-flow was developed to accommodate larger water flows and lower heads than the Pelton.

Reaction TurbineA reaction turbine develops power from the combined action of pressure and moving water. The runner is placed directly in the water stream flowing over the blades rather than striking each individually. Reaction turbines are generally used for sites with lower head and higher flows than compared with the impulse turbines.

A propeller turbine generally has a runner with three to six blades in which the water contacts all of the blades constantly. Picture a boat propeller running in a pipe. Through the pipe, the pressure is constant; if it isn't, the runner would be out of balance. The pitch of the blades may be fixed or adjustable. The major components besides the runner are a scroll case, wicket gates, and a draft tube. There are several different types of propeller turbines:

Bulb turbine. The turbine and generator are a sealed unit placed directly in the water stream.

Straflo. The generator is attached directly to the perimeter of the turbine.

Tube turbine. The penstock bends just before or after the runner, allowing a straight line connection to the generator.

Kaplan. Both the blades and the wicket gates are adjustable, allowing for a wider range of operation.

Francis turbine has a runner with fixed buckets (vanes), usually nine or more. Water is introduced just above the runner and all around it and then falls through, causing it to spin. Besides the runner, the other major components are the scroll case, wicket gates, and draft tube.

Hydro Turbine Parameters(Power, discharge, Efficiency, Head, specific Speed) i.e, P = n x g x Q x H

Escudero Hydroelectric Power Planto It was built in 1937. located at Villa

Escudero Tiaong, Quezon, Philippines.

o it generated power for the Escudero coconut plantation.

o composed of 2 hydro units; a 75 kW(located below the 1937 unit) and a 37.5 kW plant (located 700meters down river).

CostHydropower is an efficient way to generate electricity.

Modern hydro turbines can convert as much as 90% of the available energy into electricity.

The best fossil fuel plants are only about 50% efficient.

25% the cost of natural gas 40% the cost of fossil fuel 50% the cost of nuclear

“Hydropower makes us wet”Prepared by: G5