ppe unit 5

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UNIT 5 -NON-CONVENTIONAL

POWER GENERATION

Solar Energy

Geothermal resources

Wind power plants

Tidal power plants

MHD power generation-principle

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Solar Energy

….and it’s many uses

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SOLAR ENERGY

A FEW FACTS

Every day the earth receives thousands of timesmore energy from the sun than is consumed in all

other resources. If a 140x140 mile parcel of land in Arizona was

covered with solar cells, the electricity needs of theentire United States could be met.

The sunlight falling on a typical house can providefrom 1/3 to 1/2 of the heating needs of that house.

Today solar energy accounts for only 1% of thetotal renewable energy consumed in the UnitedStates

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Characteristics of

Isolation Isolation is the amount of solar

radiation reaching the earth. Also called Incident Solar

Radiation. The sun’s energy is created

from the fusion of hydrogennuclei into helium nuclei.

Components of Solar Radiation:Direct radiation

Diffuse radiation

Reflect radiation

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SOLAR HEATING TODAY

Used mostly forheating pools anddomestic hot water(DHW)

Two types of solarheating systems: Active Solar Heating

System

Passive SolarHeating System

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ACTIVE SOLAR HEATING

SYSTEM A system that uses

water or air that the

sun has heatedand is thencirculated by a fanor pump.

Three Types:Flat Plate Collectors

Batch WaterHeaters

Thermosiphon

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FLAT PLATE COLLECTORS

A thin flat metal plateis used to absorb thesun’s radiation.

Tubes carry water intothe absorber platewhere it is heated bythe sun and sent to a

pump or fan intostorage and distributedfrom there to the livingspace.

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BATCH WATER HEATERS

Pre-heats water using thesun by having a blacktank inside an isolatedbox with a glass cover.

Solar energy is absorbedwithin the box to heat thewater.

The water outflow is sentinto a conventional water

heater for further heating. They are also called

“Bread-Box” heaters.

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PASSIVE SOLAR HEATING

SYSTEMS The house itself acts as the solar collector

and storage facility.

No pumps or fans are used. This system makes use of the materials of

the house to store and absorb heat.

Three Types: Direct-Gain

Indirect-Gain

Attached Greenhouse

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DIRECT-GAIN

Large south facingwindows that let in

the sunlight. Thermal mass is

used to absorb theradiation.

At night theabsorbed heat isradiated back into

the living space.

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INDIRECT-GAIN

Collects and stores thesolar energy in onepart of the house and

use natural heattransfer to distributeheat to the rest of thehouse.

Popular method is to

use a Trombe Wallwhich is a massiveblack masonry thatacts as a solar collectorand a heat storagemedium.

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GEOTHERMAL ENERGY

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Sources of Earth’s

Internal Energy•70% comes from the decay of radioactive nuclei with long half

lives that are embedded within the Earth

•Some energy is from residual heat left over from Earths formation.•The rest of the energy comes from meteorite impacts.

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Normal Geothermal Gradient: At any place on the planet, there is a normal

temperature gradient of +300C per km dug into the earth. Therefore, if one

digs 20,000 feet the temperature will be about 1900C above the surface

temperature. This difference will be enough to produce electricity. However,

no useful and economical technology has been developed to extracted this

large source of energy.

Hot Dry Rock: This type of condition exists in 5% of the US. It is similar to

Normal Geothermal Gradient, but the gradient is 400C/km dug underground.

Molten Magma: No technology exists to tap into the heat reserves stored

in magma. The best sources for this in the US are in Alaska and Hawaii.

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How Direct Uses Work

•Direct Sources function by sending water down a well to be heated by the

Earth’s warmth.

•Then a heat pump is used to take the heat from the underground water to thesubstance that heats the house.

• Then after the water it is cooled is injected back into the Earth.

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Ground Heat Collectors This system uses horizontal loops filled with circulating water at a depth of

80 to 160 cm underground.

Borehole Heat Exchange

This type uses one or two undergroundvertical loops that extend 150 meters belowthe surface.

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Generation of Electricity isappropriate for sources

>150oCDry Steam Plants: These were the first type of plants created. They

use underground steam to directly turn the turbines.

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Flash Steam Plants: These are the most common plants. These systems pull

deep, high pressured hot water that reaches temperatures of 3600F or more to

the surface. This water is transported to low pressure chambers, and the

resulting steam drives the turbines. The remaining water and steam are theninjected back into the source from which they were taken.

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Binary Cycle Plants: This system passes moderately hot geothermal water

past a liquid, usually an organic fluid, that has a lower boiling point. The

resulting steam from the organic liquid drives the turbines. This process

does not produce any emissions and the water temperature needed for

the water is lower than that needed in the Flash Steam Plants (2500F – 3600F).

Casa Diablo

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Hot Dry Rocks: The simplest models have one injection well and two

production wells. Pressurized cold water is sent down the injection well

where the hot rocks heat the water up. Then pressurized water of

temperatures greater than 2000F is brought to the surface and passed

near a liquid with a lower boiling temperature, such as an organic liquid

like butane. The ensuing steam turns the turbines. Then, the cool water

is again injected to be heated. This system does not produce any

emissions. US geothermal industries are making plans to commercialize

this new technology.

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Geothermal’s Harmful

Effects Brine can salinate soil if the water is not injected back into the reserve after

the heat is extracted.

• Extracting large amounts of water can cause land subsidence, and this canlead to an increase in seismic activity. To prevented this the cooled water

must be injected back into the reserve in order to keep the water pressure

constant underground.

• Power plants that do not inject the cooled water back into the ground can

release H2S, the “rotten eggs” gas. This gas can cause problems if largequantities escape because inhaling too much is fatal.

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Geothermal’s Positive

Attributes Useful minerals, such as zinc and silica, can be extracted from

underground water.

Geothermal energy is “homegrown.” This will create jobs, a betterglobal trading position and less reliance on oil producing countries.

US geothermal companies have signed $6 billion worth of contractsto build plants in foreign countries in the past couple of years.

• In large plants the cost is 4-8 cents per kilowatt hour. This cost isalmost competitive with conventional energy sources.

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•Geothermal plants can be online 100%-90% of the time. Coal plants can

only be online 75% of the time and nuclear plants can only be online 65% of

the time.

•Flash and Dry Steam Power Plants emit 1000x to 2000x less carbon dioxide

than fossil fuel plants, no nitrogen oxides and little SO2.

•Geothermal electric plants production in 13.380 g of Carbon dioxide per

kWh, whereas the CO2 emissions are 453 g/kWh for natural gas, 906g

g/kWh for oil and 1042 g/kWh for coal.

•Binary and Hot Dry Rock plants have no gaseous emission at all.

•Geothermal plants do not require a lot of land, 400m2 can produce a

gigawatt of energy over 30 years.

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•Electricity generated by geothermal plants saves 83.3 million barrels of fuel

each year from being burned world wide. This prevents 40.2 million tons of

CO2 from being emitted into the atmosphere.

•Direct use of geothermal energy prevents 103.6 million barrels of fuel each

year from being burned world wide. This stops 49.6 tons of CO2 from beingemitted into the atmosphere.

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Availability of Geothermal

Energy On average, the Earth emits 1/16

W/m2. However, this numbercan be much higher in areas suchas regions near volcanoes, hotsprings and fumaroles.

As a rough rule, 1 km3 of hotrock cooled by 1000C will yield 30MW of electricity over thirtyyears.

It is estimated that the worldcould produce 600,000 EJ over 5

million years.

There is believed to be enoughheat radiating from the center ofthe Earth to fulfill human energydemands for the remainder ofthe biosphere’s lifetime.

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WIND POWER

What is it?

How does it work? Efficiency

U.S. Stats andExamples

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WIND POWER - What is it?

All renewable energy (except tidal and geothermal power),ultimately comes from the sun

The earth receives 1.74 x 1017 watts of power (per hour) from

the sun

About one or 2 percent of this energy is converted to windenergy (which is about 50-100 times more than the energyconverted to biomass by all plants on earth

Differential heating of the earth’s surface

and atmosphere induces vertical and horizontal

air currents that are affected by the earth’s

rotation and contours of the land WIND.

~ e.g.: Land Sea Breeze Cycle

• Winds are influenced by the ground surface at altitudes up to

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• Winds are influenced by the ground surface at altitudes up to

100 meters.

• Wind is slowed by the surface roughness and obstacles.

• When dealing with wind energy, we are concerned with

surface winds.

• A wind turbine obtains its power input by converting the

force of the wind into a torque (turning force) acting on the

rotor blades.

• The amount of energy which the wind transfers to the rotordepends on the density of the air, the rotor area, and the wind

speed.

• The kinetic energy of a moving body is proportional to its

mass (or weight). The kinetic energy in the wind thus depends

on the density of the air, i.e. its mass per unit of volume.In other words, the "heavier" the air, the more energy is

received by the turbine.

•at 15° Celsius air weighs about 1.225 kg per cubic meter, but

the density decreases slightly with increasing humidity.

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WINDMILL DESIGN

A Windmill captureswind energy and thenuses a generator toconvert it to electrical

energy. The design of a

windmill is an integralpart of how efficient itwill be.

When designing awindmill, one mustdecide on the size ofthe turbine, and thesize of the generator.

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SMALL TURBINES:

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SMALL TURBINES:

Local electrical grids may not be able to handle the large electrical

output from a large turbine, so smaller turbines may be more

suitable.

High costs for foundations for large turbines may not beeconomical in some areas.

Landscape considerations

Wi d T bi N b f Bl d

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Wind Turbines: Number of Blades

Most common design is the three-bladed turbine. The most important reason is the

stability of the turbine. A rotor with an odd number of rotor blades (and at least three blades) can be considered to be similar to a disc when calculating the dynamic

properties of the machine.

A rotor with an even number of blades will give stability problems for a machine

with a stiff structure. The reason is that at the very moment when the uppermost blade

bends backwards, because it gets the maximum power from the wind, the lowermost blade passes into the wind shade in front of the tower.

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• Wind power generators

convert wind energy

(mechanical energy) to

electrical energy.

• The generator is attachedat one end to the wind

turbine, which provides

the mechanical energy.

• At the other end, the

generator is connected to

the electrical grid.

• The generator needs to

have a cooling system to

make sure there is nooverheating.

WIND TURBINE

GENERATOR

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SMALL GENERATORS: Require less force to turn than a larger ones, but give much lower

power output.

Less efficient

i.e.. If you fit a large wind turbine rotor with a small generator itwill be producing electricity during many hours of the year, but it

will capture only a small part of the energy content of the wind at

high wind speeds.

LARGE GENERATORS:

Very efficient at high wind speeds, but unable to turn at low wind

speeds.

i.e.. If the generator has larger coils, and/or a stronger internal

magnet, it will require more force (mechanical) to start in motion.

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Advantages of Wind Power

• The wind blows day and night, which allows windmills to

produce electricity throughout the day. (Faster during the day)

• Energy output from a wind turbine will vary as the wind varies,

although the most rapid variations will to some extent becompensated for by the inertia of the wind turbine rotor.

• Wind energy is a domestic, renewable source of energy that

generates no pollution and has little environmental impact. Up to

95 percent of land used for wind farms can also be used for other

profitable activities including ranching, farming and forestry.

• The decreasing cost of wind power and the growing interest in

renewable energy sources should ensure that wind power will

become a viable energy source in the United States and worldwide.

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Tidal Power

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Tidal power is dependant on tides createdby the moons gravitational pull on the

earth

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Types of Tidal Power

Generation Barrages

Tidal Streams

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Tidal Barrage

Turbines

Sluice gates

Embankments

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Bulb Turbine

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Straflo or Rim Generator

Turbine

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Tubular Turbine

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Benefits

Renewable

Can help protection of ports in storms

Can help navigation for shipping

Reliable, more so than solar or wind

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Tidal streams

Instead of damming estuaries the tidalcurrents are harnessed using wind like

turbines

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Benefits of Tidal stream

Far less intrusive

Can generate same amount of power

as wind with smaller blades movingslower due to density of water

More available sites

More reliable than wind

Usually less expensive than barrage

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MHD power generation uses theinteraction of an electrically conducting

fluid with a magnetic field to convert partof the energy of the fluid directly intoelectricity

Converts thermal or kinetic energy intoelectricity

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Conversion Efficiency

MHD generator alone: 10-20%

Steam plant alone: ≈ 40%

MHD generator coupled with a steamplant: up to 60%

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Losses

Heat transfer to walls

Friction

Maintenance of magnetic field

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MHD + Steam plant

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