Hydroelectricity

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# Hydroelectricity - PowerPoint PPT Presentation

Hydroelectricity. Solar Power From Water Andrea Joy. What is Hydroelectricity?. Hydroelectricity is an electrical generation system that creates electrical current from the movement of water through turbines. A Little History.

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Presentation Transcript

### Hydroelectricity

Solar Power From Water

Andrea Joy

What is Hydroelectricity?

Hydroelectricity is an electrical generation system that creates electrical current from the movement of water through turbines.

A Little History
• Since ancient times humans have used moving water as an energy source. At least 5000 years ago simple water wheels were being used for irrigation and water distribution.
• Development created increasingly efficient designs until Benoit Fourneyron invented the first water turbine in 1832, with an efficiency of 80%.
• A few years later James Francis began experimenting with inward flow radial turbines and these led to the modern turbine most commonly used today called the Francis turbine.
• In the last quarter of the nineteenth century, hydro technology proceeded to develop exponentially.
How much Power?
• How much power a hydroelectric system generates depends on input:
• Effective head (height through which water falls) H
• Flow rate (cubic meters of water per second) Q

INPUT : P(kW) = 10 × Q × H

Stored Energy and Available Power

Potential energy = MgH

M = mass of water in kilograms

g = acceleration due to gravity (9.81 ms-2)

Output Power : P(kW) = 9.81ηQH

η = Turbo-generator efficiency

Q = Flow rate

Key Components
• Dam or Barrage (a solid wall to back up the water creating a reservoir)
• Reservoir (created by the dam or barrage)
• Penstock (for medium or high head systems, to transport water from reservoir to turbine)
• A turbine runner (a set of curved blades on a radial frame through which water flows and creates direct power)
• Generator (converts the direct (kinetic) power into electric current)
Types of Modern Hydroelectric Plants
• Low Head (small height of drop)
Impacts

Insults

• Disturbance of natural habitats
• Potential catastrophes from a breech in the dam
• Relocation of communities
• Aesthetic implications
• Power storage difficulties

Benefits

• Clean renewable sustainable energy
• Creation of ‘waterfront property’
• Can aid in flood control and irrigation
Benefits
• The energy produced by hydroelectric generation systems is clean, creating little to no atmospheric pollution, no radioactive compounds, and no particulates or chemical compounds that are harmful to human health.
• It is renewable, and can function for as long as the structures themselves are maintained.
• It is sustainable and can be depended on by future generations
• Artificial reservoirs create waterfront property which has economic and aesthetic value.
• Reservoirs can aid in irrigation and flood control.
Insults
• Often, large scale projects require deforestation, flooding of riparian areas, and disturbance in fish spawning and breeding behaviors, and if the trees are not cut and removed they rot at the bottom of the reservoir creating methane, a potent greenhouse gas.
• Creation of reservoirs and diversion or piping water can result in increased evaporation leading to a fall in the water table.
• It can threaten and kill flora and fauna that depended on the natural flow such as fish who must swim up river to spawn.
• Construction can cause major disturbances pollution and alteration of land.
• Silt accumulation reduces the useful volume and thus output capacity of the reservoir and it does not make it down stream to areas that really need it for soil building.
Insults continued…
• Dam failure can kill thousands of humans as well as other species downriver by creating a surge that devastates the land much like a Tsumani.
• Relocation of communities in reservoir areas is difficult for people who have lived in these areas and established their communities there.
• Aesthetic value of the Dam itself is usually negative.
• Storage of Power to compensate for peak demand or generator failure is difficult, although pumped storage offers a viable option in certain instances.
Scale and Need
• In considering the cost/benefit analysis for a hydro system it is important to consider the scale as many of the potential insults can be avoided in the creation of small scale hydroelectric systems.
• It is also important to consider that in general if a hydro plant is being considered, it is necessary to generate power for the region in some form, and thus would be better than a more conventional fossil fuel based system, all things considered.
Summary
• Hydroelectric systems are not entirely free of negative impacts, but all things considered they are often far better than non-renewable alternatives, but this depends heavily on the site.
• Hydroelectricity is a well established technology that already accounts for about 1/6 of world’s electrical output, and over 90% of electricity from renewable energy sources.
• Site, scale, and need are all important in deciding where and how to construct a dam.
Hydroelectricity in Belize
• Mollejon Dam (on Macal)
• Challilo Dam (on Macal, downstream)

Challilo Dam Project

Specifications:

Will deliver 30 GWh of electricity and increase capacity of Mollejon by about 55 GWh annually.

49.5 m high storage Dam

7 MW power house at toe of Dam

Located on Macal River 18 kilometers upstream from existing 25 MW Mollejon plant

Will flood 9.5 sq km including 1.5 sq. km of existing river (2,800 acres of rainforest that is a home to jaguars, ocelots, Tapirs and some of the last known Scarlet Macaws)

Cost estimated at US \$30 million

Insults of Dam

Destruction of habitats for already endangered species such as the Jaguar and Scarlet Macaws

Absence of promised economic benefits to Belizean people (Fortis raises light bills 12% in May 2005 and another 13% in January 2006.)

Being built near a fault line, so it is a very unstable and dangerous site

Loss of cultural heritage ("A total of 298 structures have been identified in the project area.  This is a very high density and is consistent with heavy settlement in other river valleys in Belize.” )

Methane emissions from rotting vegetation will contribute further to Global Warming.

But how much is Challillo really considering the people of Belize’s desires…..

"This is the prettiest river in the country," says Mick Fleming, who owns the Chaa Creek Lodge, an ecotourism resort set in the jungle 20 miles downstream from the dam site. "We're going to lose something incredibly valuable in return for an extremely small amount of power."

Plenty of people in Cayo agree with Fleming's assessment. The city council in the district capital, San Ignacio, opposes the dam, and the vice mayor testified against the project during an unsuccessful attempt to block construction brought before the Privy Council in London last year. T-shirts and banners bearing such slogans as "The Macal is Ours" are seen all over town. "We use the river for drinking and swimming and tourism and canoeing," explains San Ignacio hotel owner Maria Preston. "The river is everything for us.“

Is it really good for Belize?

While the dam will substantially boost domestic electricity production, most of the power will be generated at times of day when it is more expensive than importing it from Mexico. A 2000 study by the California-based Conservation Strategy Fund estimated the project would be a net drag on the Belizean economy. The dam is also being built near an active fault line, and Fortis admitted that it mischaracterized the geological properties of the site.

"This a bad project all the way around," says Grainne Ryder, policy director of Probe International in Toronto, which has led a campaign against Chalillo in Canada. "Fortis may make a quick profit out of it, but Belizeans will be left with the real costs for generations."