answ2. Hydroelectric dams are temporary features. They will eventually fill up with gravel and silt from the river. This is very expensive to remove.

Otherwise the maintenance is things like removal of debris that may damage the turbines. The actual maintenance of turbines and generators is small - occasionally bearings need replacement and so on. Pretty minimal overall.

Hydroelectricicity is expensive to install, but the annual running costs are very small.

You will need a water reservoir, some form of turbine, and something connected to the turbine to represent a generator.

The water reservoir can be just about anything that can contain water at an elevation above that of your turbine. In the real world, this is usually a dam, so you may want to model something that looks like a dam.

Water from the elevated source is allowed to flow from the source past a water turbine. You could make a waterfall and paddlewheel so that people can see the workings, but in an actual generation station, this is a pipe and the turbine is enclosed.

The turbine turns as a result of the water flow. A generator is connected to the shaft of the turbine. You can use a permanent magnet motor for your generator. Just hook up a voltmeter to what would normally be the battery leads of the motor to show the voltage being generated. Chances are, your model won't be able to generate enough power to light a bulb, so showing the voltage with a voltmeter is a simple way of demonstrating the principle.

1.cardboard

2.aluminium foil or butter paper

3.chart paper

4.a generator

5.a turbine made of plastic

6.a 1.5 volt battery

Hydro comes from the Greek word for water. Hydro-electricity, or hydro-power, is usually generated by turbines in a dam in a river. The dam means that a great body of water builds up in the river valley behind the dam. This is released through the turbines when electricity is needed.

Smaller than dams are barrages across the mouths of rivers which capture water from high tides and release it to generate electricity. Smaller still are turbines in river and tidal streams which do the same thing.

A. Advantages:

• Does not depend on costs of uranium, oil, or other fuels
• Pollution is rarely created
• It doesn't require as many employees
• It can be set up in many sizes
• Stations can operate and run for long periods of time
• Reduces greenhouse emissions
• Relatively low maintenance costs
• Can be used throughout the world
• It is renewable
• Hydroelectricity produces no gas emissions or waste.
• Hydroelectric stations are inexpensive to operate.
• Makes barely any pollution compare to other ways of creating electricity
• Hydroelectric power is one of the most responsive (easy to start and stop) of any electric power generating source.
• The conversion of the forces of water to electric energy can be up to 90 percent efficient.
• Hydroelectric power produces no chemical or waste heat pollution.
• Hydroelectric power plants require little maintenance.
• Reservoir lakes can be used for recreation, and can provide considerable flood protection to downstream areas.
• Groundwater reserves are increased by recharging from reservoirs.
• Plants usually have an expected life span two to three times longer than conventional thermal power plants.
• Hydroelectric installations can be used to breed fish and other aquatic products
• It is more reliable than solar and wind power - because water can be stored and there is more of it, more often.Once a dam is constructed, electricity can be produced at a constant rate.
• If electricity is not needed, the sluice gates can be shut, stopping electricity generation. The water can be saved for use another time when electricity demand is high. The build up of water in the lake means that energy can be stored until needed, when the water is released to produce electricity.
• Dams are designed to last many decades and so can contribute to the generation of electricity for many years / decades.
• The lake that forms behind the dam can be used for water sports and leisure / pleasure activities. Often large dams become tourist attractions in their own right.
• The lake's water can be used for irrigation purposes.
• When in use, electricity produced by dam systems do not produce green house gases. They do not pollute the atmosphere.
• Hydropower is a fueled by water, so it's a clean fuel source. Hydropower doesn't pollute the air like power plants that burn fossil fuels, such as coal, oil or natural gas.
• Hydropower is a domestic source of energy, produced locally near where it is needed.
• Hydropower relies on the water cycle, which is driven by the sun, thus it's a renewable power source so long as the rain keeps falling on the dam catchment area.
• Hydropower is generally available as needed; engineers can control the flow of water through the turbines to produce electricity on demand.
• Hydropower is not only a cleaner source of energy than oil but is it more cost effective as well. The most efficient coal burning plants are only able to convert around 50 percent of their energy into electricity, whereas modern day hydro power turbines convert up to 90 percent of their energy into electricity.
• Hydropower can cost less than a penny per kWh (Kilowatt Hour) compared to fossil fuel power plants at around 2 to 3 cents per kWh. That may not seem like a big difference, but when factored out over a year and the millions of kW hours Americans burn, it adds up to a huge savings.
• Hydropower plants also have an added bonus as they create recreational opportunities for people as well as electricity. Hydro power dams provide not only water-based activities, but since much of the surrounding land is public they also encourage numerous other outdoor activities aside from boating, skiing, fishing, and hunting.
• Hydropower plants provide benefits in addition to clean electricity. Hydro power plants create reservoirs that offer a variety of recreational opportunities, notably fishing, swimming, and boating. Most hydro power installations are required to provide some public access to the reservoir to allow the public to take advantage of these opportunities. Other benefits may include water supply and flood control.
• Can help regulate river flows (flood prevention), stores water, creates recreational lake (though these uses often conflict).

B. Disadvantages:

• High investment costs
• Dependent on precipitation
• Sometimes messes up wildlife
• Loss of fish species
• Change in river or stream quality
• Cost for construction
• Hydroelectric power production require flooding of entire valleys and scenic areas.
• Disrupts natural seasonal changes in he river, and ecosystems can be destroyed.
• Ends flooding that help to clean out the silt in rivers, causing them to clog (Energy Laboratory).
• The silt that usually flows down to the Beaches and Estuaries is block by the dam.
• Studies show that the plant decay caused downstream of major dams produces as many greenhouse gasses as more conventional methods of producing electricity.
• Dams are expensive to build, and due to drought may become useless, or produce much less power than originally planned.
• A dam being built in Quebec may end up flooding a land area as large as Switzerland.
• Dams can break in a massive flash flood
• Construction costs of large-scale hydroelectric projects are high.
• Damming rivers causes changes in ecological cycles and surrounding landscapes; self-regulating ecosystems are changed into ones that must be managed.
• Sedimentation can progressively curtail a dam's ability to store water and generate energy.
• There are a limited number of feasible sites for large dams.
• Damming can cause loss of land suitable for agriculture and recreation.
• Drought can affect power production.
• Dams are vulnerable to natural forces. There is a high direct death rate from the failure of dams.
• River channels downstream from dams are more susceptible to erosion.
• A disadvantage of hydroelectric power stations is that it destroys wildlife and habitats of any creatures living in the area.
• Dams are extremely expensive to build and must be built to a very high standard.
• The high cost of dam construction means that they must operate for many decades to become profitable.
• The flooding of large areas of land means that the natural environment is destroyed.
• People living in villages and towns that are in the valley to be flooded, must move out. This means that they lose their farms and businesses. In some countries, people are forcibly removed so that hydro-power schemes can go ahead.
• The building of large dams can cause serious geological damage. For example, the building of the Hoover Dam in the USA triggered a number of earth quakes and has depressed the earth's surface at its location.
• Although modern planning and design of dams is good, in the past old dams have been known to be breached (the dam gives under the weight of water in the lake). This has led to deaths and flooding.
• Dams built blocking the progress of a river in one country usually means that the water supply from the same river in the following country is out of their control. This can lead to serious problems between neighboring countries.
• Building a large dam alters the natural water table level. For example, the building of the Aswan Dam in Egypt has altered the level of the water table. This is slowly leading to damage of many of its ancient monuments as salts and destructive minerals are deposited in the stone work from 'rising damp' caused by the changing water table level.
• Hydro power dams can damage the surrounding environment and alter the quality of the water by creating low dissolved oxygen levels, which impacts fish and the surrounding ecosystems. They also take up a great deal of space and can impose on animal, plant, and even human environments.
• Fish populations can be impacted if fish cannot migrate upstream past impoundment dams to spawning grounds or if they cannot migrate downstream to the ocean. Upstream fish passage can be aided using fish ladders or elevators, or by trapping and hauling the fish upstream by truck. Downstream fish passage is aided by diverting fish from turbine intakes using screens or racks or even underwater lights and sounds, and by maintaining a minimum spill flow past the turbine.
• Hydro power can impact water quality and flow. Hydro power plants can cause low dissolved oxygen levels in the water, a problem that is harmful to riparian (riverbank) habitats and is addressed using various aeration techniques, which oxygenate the water. Maintaining minimum flows of water downstream of a hydro power installation is also critical for the survival of riparian habitats.
• Hydro power plants can be impacted by drought. When water is not available, the hydro power plants can't produce electricity.
• New hydro power facilities impact the local environment and may compete with other uses for the land. Those alternative uses may be more highly valued than electricity generation. Humans, flora, and fauna may lose their natural habitat. Local cultures and historical sites may be flooded. Some older hydro power facilities may have historic value, so renovations of these facilities must also be sensitive to such preservation concerns and to impacts on plant and animal life.
• By 2020, it is projected that the percentage of power obtained from hydro power dams will decrease to around four percent because no new plants are in the works, and because more money is being invested in other alternative energy sources such as solar power and wind power.
• Dams usually flood large river valleys, covering a lot of native habitat with water, displacing animals and sometimes people. In China more than one million people were moved when they built their big "Three Gorges" dam. Many archaeological sites are now unreachable under water and there is environmental damage along the banks of the many tributaries of the Yangtze River

In brief:

Hydro was the first commercial source of power of any size. The uses were understood right away, but there certainly are drawbacks.

They destroy farmland and alter the course of rivers. They must also be located at the discretion of the plant rather than our choosing. Much of our power that we use today is not even used constructively. There is a large portion of our energy that is used in transporting it across the country. The major disadvantage I would put against this form of power would be the land and energy consumed in transporting the power away from the plants. Grid loss is a major issue for energy users.

It is a renewable energy source. Unlike fossil fuels which will eventually run out, hydro power plants do not use up the energy source. It is also not polluting to the environment. They output power at a relatively reliable rate (compared to solar or wind, especially). On the other hand, they drastically affect all ecosystems upstream of the dam, and are much more environmentally destructive than nuclear power plants.

Advantages

• Inexhaustible fuel source
• Minimal environmental impact
• Viable source--relatively useful levels of energy production
• Can be used throughout the world

Disadvantages

• Smaller models depend on availability of fast flowing streams or rivers
• Run-of-the-River plants can impact the mobility of fish and other river life. NOTE: Building a fish ladder can lessen this negative aspect of hydroelectric power.

Hydroelectric power, or hydroelectricity, is generated by the force of falling water. (Hydro comes from the Greek word for water.) It’s one of the cleanest sources of energy, and it’s also the most reliable and costs the least. Water is needed to run a hydroelectric power-generating unit. The water is held behind a dam, forming an artificial lake, or reservoir. The force of the water being released from the reservoir through the dam spins the blades of a giant turbine. The turbine is connected to the generator that makes electricity as it spins. After passing through the turbine, the water flows back into the river on the other side of the dam.

Electricity is produced by spinning electromagnets within a generator’s wire coil that creates a flow of electrons. To keep the electromagnets spinning, hydroelectric stations use falling water. Hydroelectric power plants convert the kinetic energy contained in falling water into electricity. The energy in flowing water is ultimately derived from the sun, and is therefore constantly being renewed. Energy contained in sunlight evaporates water from the oceans and deposits it on land in the form of rain. Differences in land elevation result in rainfall runoff, allowing some of the original solar energy to be captured as hydroelectric power. Most hydroelectric stations use either the natural drop of the river or build a dam across the river to raise the water level and provide the drop needed to create a driving force. Water at the higher level (the forebay,) goes through the intake into a pipe, called a penstock, which carries it down to the turbine. The turbine is a type of water wheel that converts the water's energy into mechanical power. The turbine is connected to a generator, and (4) when the turbine is set in motion it causes the generator to rotate, producing electricity. The falling water, having served its purpose, exits the generating station through the draft tube and the tailrace where it rejoins the river.

At Ontario Power Generation (OPG), hydroelectric generation is their lowest-cost power source, producing approximately 34 terawatt-hours in 2002. OPG operates 36 hydroelectric stations, as well as 29 small hydroelectric plants and 240 dams on 26 river systems. The smallest station has a generating capacity of just 1 megawatt; the largest more than 1,300 megawatts.