Solar Energy IV HydroelectricityandOTEC

Hydro power has a very long history with watermills appearing as early as 100 BC. Hydro power has a very long history with watermills appearing as early as 100 BC. By 1200 it was used to operate hammers in ironworks By 1200 it was used to operate hammers in ironworks

By 1500 it was the primary source of industrial power. By 1500 it was the primary source of industrial power. Rivers and streams were a critical source of power and transportation in the settling of America. Rivers and streams were a critical source of power and transportation in the settling of America.

First Hydroelectric Generator Located at Cragside, a country house in Northumberland, England. Located at Cragside, a country house in Northumberland, England. country house Northumberland England country house Northumberland England In 1870, water from one of the estate's lakes was used to drive a Siemens dynamo in what was probably the world's first hydroelectric power station. In 1870, water from one of the estate's lakes was used to drive a Siemens dynamo in what was probably the world's first hydroelectric power station.1870Siemens dynamo power station1870Siemens dynamo power station

Today Hydropower is used mainly for generating electricity

Water cycle as a great big heat engine

Generators inside Hoover Dam

Convert Potential Energy of Water Into Kinetic Energy to Run a Generator mgh=mv 2 /2 mgh=mv 2 /2 h is called the “head” of the dam h is called the “head” of the dam Modern hydroelectric plants convert ~90% of PE into electricity Modern hydroelectric plants convert ~90% of PE into electricity

High Head Dams h is up to 1000ft. h is up to 1000ft. A lot of energy per liter of water that flows through. A lot of energy per liter of water that flows through. Can get by with smaller flows. Can get by with smaller flows.

Low Head Dams As low as 10 ft. As low as 10 ft. Not much energy per liter of water. Not much energy per liter of water. Need a higher flow rate to get as much electricity Need a higher flow rate to get as much electricity

Sample Calculation Useful information: 1 liter of H 2 O has a mass of 1kg. Useful information: 1 liter of H 2 O has a mass of 1kg. Height of Hoover Dam = 221 m Height of Hoover Dam = 221 m Power rating of Hoover Dam is 2,451 MW. Power rating of Hoover Dam is 2,451 MW. Find the amount of water that flows through the dam per second if it is 90% efficient. Find the amount of water that flows through the dam per second if it is 90% efficient.

Electrical power form 1 liter of water per second. Electrical power form 1 liter of water per second. P=(0.9)(1kg/s)(9.8 m/s 2 )(221m) P=(0.9)(1kg/s)(9.8 m/s 2 )(221m)=1.949kW

US Hydroelectric Production

Existing hydroelectric plants (yellow) and potential high head/low power energy sites (orange)

Principal Dams in the US

Top Ten Countries for Hydroelectricity CountryAnnual Hydroelectric Production (TWh) Installed Capacity Capacity Factor Percent of all electricity China Canada Brasil United States Russia Norway India Venezuela Japan Sweden

Top Ten Largest Hydroelectric Plants DamCountryCompletedPower (GW) Three Gorges DamChina2008/1118.3/22.5 ItaipuBrazil/Paraguay1984/91/ Guri (Simon Bolivar)Venezuela TucuruiBrazil Grand CouleeUnited States1942/ Sayano ShushenskayaRussia1985/896.4 krasnoyarskayaRussia Robert-BourassaCanada Churchill FallsCanada Longtan DamChina /6.3

Three Gorges Dam (World’s Largest)

Ten largest Dams Under Construction ProjectCountryCapacity (GW)Completion Xiluodu DamChina Siang Upper HE Project India TaSang DamBurma Xiangjiaba DamChina Nuozhadu DamChina Jinping 2 HP Station China Laxiwa DamChina Xiaowan DamChina Jinping 2 HP Station China Pubugou DamChina

Whacky Idea (2007) Red Sea Dam The idea is to dam the Red Sea at its southern end where the Bab-al-Mandab Strait is only 18 miles (29 km) wide. Natural evaporation would rapidly lower the level of the enclosed Red Sea. Water allowed back into the sea would drive turbines to generate electricity. It is claimed that up to 50 gigawatts would be generated, dwarfing all other power schemes. The idea is to dam the Red Sea at its southern end where the Bab-al-Mandab Strait is only 18 miles (29 km) wide. Natural evaporation would rapidly lower the level of the enclosed Red Sea. Water allowed back into the sea would drive turbines to generate electricity. It is claimed that up to 50 gigawatts would be generated, dwarfing all other power schemes.Red Sea Bab-al-Mandab StraitRed Sea Bab-al-Mandab Strait

Advantages to hydroelectric power :  Fuel is not burned so there is minimal pollution.  Water to run the power plant is provided free by nature.  Hydropower plays a major role in reducing greenhouse gas emissions.  Relatively low operations and maintenance costs.  The technology is reliable and proven over time  It's renewable - rainfall renews the water in the reservoir, so the fuel is almost always there.

Reservoirs can be used for other purposes such as irrigation, recreation, flood control Reservoirs can be used for other purposes such as irrigation, recreation, flood control

Disadvantages Lifetime of 50 to 200 years because of silting. Lifetime of 50 to 200 years because of silting. Large environmental changes downstream. Large environmental changes downstream. Loss of free flowing water. Loss of free flowing water. Loss of land flooded by reservoir. Loss of land flooded by reservoir. Often upstream from large population centers (Huge catastrophe if dam fails.) Often upstream from large population centers (Huge catastrophe if dam fails.)

High investment costs High investment costs Hydrology dependent (precipitation) Hydrology dependent (precipitation) Inundation of land and wildlife habitat Inundation of land and wildlife habitat Loss or modification of fish habitat Loss or modification of fish habitat Fish entrainment or passage restriction Fish entrainment or passage restriction Changes in reservoir and stream water quality Changes in reservoir and stream water quality Displacement of local populations Displacement of local populations

Dam Failures From there were 33 dam failures in the US resulting in 1680 deaths. From there were 33 dam failures in the US resulting in 1680 deaths. Between 1959 and 65 there were 9 large failures worldwide. Between 1959 and 65 there were 9 large failures worldwide. It is unusual, but a significant hazard. It is unusual, but a significant hazard. Terrorists? Terrorists?

Water pouring out of the reservoir of the Teton Dam in Idaho following its catastrophic failure on June 5, 1976.Teton DamIdaho Teton Dam Failure

Ocean Thermo Electric Conversion Use temperature difference between the surface and deep water to drive a heat engine. Use temperature difference between the surface and deep water to drive a heat engine. Typically very low efficiency, but no cost for fuel. Typically very low efficiency, but no cost for fuel. Typically T 20K and T h 20K, thus Typically T 20K and T h 20K, thus e c =T/T h 20/300=6.7% e c =T/T h 20/300=6.7% Real efficiency more like 2-3%

Requires a huge flow of water. Requires a huge flow of water. A 100 MW plant would require approximately 25,000,000 liters per second of both warm and cold water. A 100 MW plant would require approximately 25,000,000 liters per second of both warm and cold water.

Use in locations with warm surface waters. T>17C Use in locations with warm surface waters. T>17C Predictable power output since T is very stable over the course of a day. Predictable power output since T is very stable over the course of a day.

Not a whole lot currently being developed. Not a whole lot currently being developed. 1930’s : concept plant built near Cuba generated 22kW of power, but used more than it generated. 1930’s : concept plant built near Cuba generated 22kW of power, but used more than it generated. 1970’s : small test plant built in Hawaii. 1970’s : small test plant built in Hawaii. No government support since the 1980’s. No government support since the 1980’s.

Other Ideas Large underwater turbines anchored to the sea floor. Large underwater turbines anchored to the sea floor. Ex: Gulf stream has a steady flow that is 1000 time larger than the Mississippi River with a maximum velocity of 4mph. Ex: Gulf stream has a steady flow that is 1000 time larger than the Mississippi River with a maximum velocity of 4mph.