Engineering Energy: Hydroelectric

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Engineering massive structures

Some of today’s greatest engineering accomplishments can be viewed around the world in the form of hydroelectric dams. Engineers from different disciplines that include mechanical engineers, electrical engineers and civil engineers, collaborate to design some of the tallest and most massive structures on the planet.

Using water, or hydropower, to create electricity is the most widely used form of renewable energy. By building these dams, some of which exceed 900 feet in height, we are able to utilize the water stored in the enormous reservoirs and rivers to generate immense amounts of electricity. As with most sources of renewable energy, the initial cost is usually high, but the rewards come in money saved once the plants are online and running. Most of the cost savings are due to the fact that hydroelectric power plants, once operational, are mostly automated and need very few people to run and maintain during operating hours. These plants also have the ability to generate electricity as needed, meaning they can ramp up or down the output as demand is needed resulting in costs as little as 3-5 U.S. cents per kilowatt-hour. There are downsides to building these dams such as the negative effects on ecosystems and wildlife. The large reservoirs needed for the process can have an effect on lowland and river valleys.

Once constructed, the process is pretty simple. The basic concept is to release water from the upper reservoir into the dam, through the turbines and release to the river or spillway below. How that is achieved, is a combination of great engineering feats.

Mechanical Engineers utilized from the start

It starts with civil and mechanical engineers working on the design and implementation of choosing the most efficient and economical area to construct the dams, waterways and reservoirs. The dam itself is built in an area and way that will maximize the use of the river and surrounding topography. Computer controlled openings within the dam, also known as gates, control the amount of water needed at any given time to generate the electricity.

Once open, the water is directed through a series of turbines which are used to create the electricity. The concept behind a water turbine is fairly simple. You push water through a series of blades positioned as an impeller that spins the connected shaft attached to a rotor. The spinning rotor in conjunction with the stator completes the initial conversion of water to electricity and is ready to be delivered to the grid. The engineering behind the turbine itself has come a long way since the earliest known use of a water turbine. The Roman Empire showed signs of using turbines as early as the 3rd or 4th century AD.  Mechanical engineers have worked through the years changing and perfecting the turbines to be more efficient and last longer. The two most common types of water turbines in use today are either reaction or impulse. Reaction turbines are completely encased and submerged and use the suction on the pressure changes in water as it moves through the turbine. As it moves, the water transfers its energy to the blades. These are the more commonly used type of water turbine. The impulse turbine work using the potential energy from water compressed though a stationary nozzle to spin the blades that are attached to the rotor. This type of turbine does not need an encasement due to the fact that there becomes no pressure change at the blades as it takes place at the nozzle.

CAD and FEA play their part in the design

The engineering that goes into the construction of the hydroelectric plants uses the tools of all different engineering disciplines. Mechanical, architectural and electrical engineers will use tools that we have previously discussed, such as CAD/CAM for computer aided design, FEA (Finite element analysis) and CFD (computational fluid dynamics) to create the computer modeling needed to construct the structures and also the components used in the energy production stages. The civil engineers will play a large role in the layouts and design of not only the structure, but the land area needed to create the reservoirs and spillways and their effect on the surrounding ecosystems.

There are many hydroelectric plants in development and under construction around the world today that will dwarf the current ones in size and electrical output. One can only wonder what the next breakthrough will bring in utilizing one of our most abundant resources to create the energy that we need.


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