Power Systems All

7/29/2019 Power Systems All

1/236

Notes on

Power SystemsBy

Dr. Khaled Ali Al-Attab


2/236

Out lines Introduction

Non-renewable energy conversion

(conventional, advanced & direct).

Energy storage and transmission.

Conventional fuels.

Nuclear power.


3/236

Out line cont.

Renewable energy:1. Solar power.

2. Wind power.

3. Biomass bower.4. Hydro-electric power.

5. Geothermal power.

6. Hydrogen power.

7. Fuel cell power.

8. Ocean power: thermal, tidal and wave energy.

Energy and environment.

Energy sources in Yemen.


4/236

Introduction Energy (J):

1. Simply is the capability to do work or thermal load.

2. It can be stored.

3. It is associated with time (Watt-hr)

Power (Watt):

1. Energy measurement, which calculates the time by

which the energy has been used or the rate ofenergy per unit time.

2. It can not be stored.

3. Power is an instantaneous quantity.


5/236

UnitsMTOE: Mega tons of oil equivalent.

1 MTOE=4.1868 104 TJ=3.968 1013 BTU.

GTOE: Giga tons of oil equivalent.

Quadrilion Btu (Quad): 1015 British thermalunits (Btu), where, 1Btu=1055J


6/236

Energysource

Renewable

Non-renewable

Energysource

Conventional

Non-conventional


7/236

Power sources usage Power generation.

Transport.

Heat generation. Industrial.

Cooking.

Others.


8/236

2009 Renewable Energy Data Book (Aug. 2010)http://www1.eere.energy.gov/maps_data/pdfs/eere_databook.pdf

Global renewable electricity installations (excluding

hydropower) have more than tripled from 20002009.

Including hydropower, renewable energy accounts for 21% of

all global electricity generation; without hydropower,

renewable energy accounts for 3.8% of global generation.

Wind and solar energy are the fastest growing renewable

energy technologies worldwide. Wind and solar PV generation

grew by a factor of more than 14 between 2000 and 2009.

In 2009, Germany led the world in cumulative solar PV

installed capacity. The United States leads the world in wind,

geothermal, biomass, and CSP installed capacity.


9/236

Renewable Electricity Generation

Worldwide by Technology (20002009)


10/236

AssignmentGlobal Renewable Energy Power Generation:

Renewable energy installed/tested technologies.

Renewable energy worldwide installations for the

last three years. Renewable energy worldwide power generation

share for the last three years.

Renewable energy installation/power share for

the last three years in Arab Nations. Conclusion (you opinion)

References


11/236

Conventional Sources of Energy The sources of energy which have been in use for

a long time, e.g., coal, petroleum, natural gas and

water power.

They are exhaust-able (will deplete) except water.

They cause pollution when used, as they emit

smoke and ash.

They are very expensive to be maintained, storedand transmitted as they are carried over long

distance through transmission grid and lines.


12/236

Non-conventional Sources of Energy The resources which are yet in the process of

development over the past few years. It

includes solar, wind, tidal, biogas, and

biomass, geothermal.

They are inexhaustible.

They are generally pollution free.

Less expensive due to local sue and easy to

maintain.


13/236

Non-renewable conventional energy

conversion Rankin Cycle (steam power generation).

Brayton Cycle (Gas turbine generation).

Otto Cycle & Diesel Cycle (Internal combustionengine generation).

Stirling engine generation.


14/236

Steam power generation

System components Steam boiler.

Steam turbine.

Condenser & cooling tower.

Water pump.

Auxiliary components

Safety and control.

Lubrication.


15/236

Steam power generation


16/236

Steam turbineImpulse turbine Reaction turbine

Steam expands through the nozzle with

constant pressure at the blades

Most of the expansion accurse through the

blades with partial expansion at the nozzle

Steam velocity remains almost constant

through the blades

Steam velocity increases through the

blades

Turbine blades has same pressure at bothsides

Steam inters at high pressure at the bladeinlet and exits at low pressure

High pressure drop in each stage, thus,

less stages required

Low pressure drop in each stage, thus,

more stages required

Lower steam speed (i.e. lower turbine

rotation speed)

Higher steam speed (i.e. higher turbine

rotation speed)Symmetric blade as shown below Airfoil blade design as shown below


17/236

Steam generator (Boiler)

Critical point: 374C and 22.06 MPa


18/236

Types of boilers Fire tube: (also known as smoke tube boilers;

shell boilers; package boilers) for low pressuresystems. Usually contains multiple tube

passes. Water tube: medium and high pressure

systems.

Waste heat: Heat recovery steam generator(HRSG) commonly used in combined cyclepower plants.


19/236

Fire tube boiler


20/236

Water tube boiler


21/236

HRSGVarious types and designs such as:

Shell and tube heat exchanger.

Water tube boiler.

Multiple drum system.


22/236

Gas turbine

Gas turbine(GT)

Micro gasturbine(MGT)

SizeDirectly

fired (DFGT)& (DFMGT)

Externallyfired (EFGT)& (EFMGT)

Firingmethod


23/236

Directly fired gas turbine (DFGT) Gas turbine engine contains: Axial flow gas

turbine & Axial flow air compressor mounted onsame shaft.

Pressurized combustor.

Speed reduction (if required).

Electrical generator.


Safety and control. Lubrication.

Air filters.

Compressor

Combustor

Turbine

Fuel


24/236

Externally fired gas turbine (EFGT) Gas turbine engine contains: Axial flow gas

turbine & Axial flow air compressor mounted onsame shaft.

Atmospheric combustor.

High temperature Heat Exchanger.

Speed reduction (If required).

Electrical generator.

Auxiliary components Safety and control.

Lubrication.

Air filters.

Compressor

Heat exchanger

Turbine

Combustor


25/236

Micro gas turbine (MGT) Gas turbine engine contains: Radial flow gas

turbine & Radial flow air compressor mountedon same shaft.

Pressurized combustor.

High speed generator mounted onturbine/compressor shaft.


Safety and control.

Lubrication.

Air filters.


26/236

Micro gas turbine (MGT)


27/236

DFGT & EFGT

DFGT EFGT

Pressurised combustion Atmospheric combustion

Requires additional cleaningand pretreatment systems to

operate with solid fuels

Can use solid type offuels without additional

cleaning systems

Can not switch between

different types

of fuels without major

modifications

Much easier in switching

between different types

of fuels.


28/236

DFGT & EFGT

DFGT EFGT

Requires fuel compression

and injection equipments

No fuel compression and

injection equipments

Higher turbine inlet

temperature

Lower turbine inlet

temperature

Higher thermodynamic

efficiency

Lower thermodynamic

efficiency

Lower initial cost Higher initial cost


29/236

Internal combustion

Compression

spark

Ignition Two stroke

Four stroke

Six stroke

Eight stroke

operation


30/236

Diesel & Otto Cycles


31/236

Two stroke Engine


32/236

Four stroke Engine

Suction Compression Power Exhaust
http://en.wikipedia.org/wiki/File:Four_stroke_cycle_exhaust.pnghttp://en.wikipedia.org/wiki/File:Four_stroke_cycle_power.pnghttp://en.wikipedia.org/wiki/File:Four_stroke_cycle_compression.pnghttp://en.wikipedia.org/wiki/File:Four_stroke_cycle_intake.png


33/236

2-stroke & 4-strokeFour-strokeTwo-stroke

Higher weigh/power ratioLower weigh/power ratio

Higher thermal efficiencyLower thermal efficiency

Lower mechanical efficiencyHigher mechanical efficiencyLower powerHigher power

Lower environmental pollutionHigher environmental pollution

AvailableNo oil pump, oil sump, valves

and cam shaft

Higher maintenance

requirement

Lower maintenance

requirement


34/236

Sixstroke

engine

Modified 4-stroke

Griffin BajulazVelozet

aCrower

Combined 2-stroke &4-stroke

Bearehead M4+2

Piston

charger

engine

M4+2


35/236

ComparisonDiesel power plantGT power plantSteam power plant

Peak and emergency loadBase and peak loadFor base load

Efficiency 35-45%Efficiency 20-45%Efficiency 30-42%

Can operate efficiently at

part load (shut down some

units)

Low efficiency at part loadCan operate efficiently at

part load (shut down some

boilers)

Moderate (higher than GT)Low pressure operationHigh pressure up to 30Mpa

Not continuousHigh 900-1400CLow temperature


36/236

Comparison cont.Diesel power plantGT power plantSteam power plant

Low power for single unit

up to 2MW

Medium power for single

unit up to 0.3GW

High power for single unit

up to 2GW

Low water consumptionLow water consumptionHigh water consumption

Moderate cooling systemElaborate cooling systemElaborate cooling system

Less sensitive to ambient

temperature and air

quality

Sensitive to ambient

temperature and air

quality

Not sensitive to ambient

temperature and air

quality

Short startup timeModerate startup timeLong startup time

High noiseHigh noiseLow noiseLow initial costHigh initial costModerate initial cost

Moderate maintenance

and lubrication

consumption

Low maintenance and

lubrication consumption

Low maintenance and

lubrication consumption


37/236

Ideal stirling EngineIsothermal expansion by external heating (Power

piston).

Isovolumetric (Isochoric) heat removal (regenerator).

Isothermal compression (second piston).Isovolumetric (Isochoric) heat addition.


38/236

Stirling Engine


39/236

Stirling Engine


40/236

Stirling Engine


41/236

Alpha stirling engine

1. Most of the working gas is in contact with the hot cylinder walls,

expansion pushes the hot piston to the bottom. The expansion

continues in the cold cylinder, which is 90 behind the hot piston,

extracting more work from the hot gas.

2. Gas is now at its maximum volume. Hot cylinder piston begins to

move most of the gas into the cold cylinder, where it cools and the

pressure drops.

3. Almost all the gas is now in the cold cylinder and cooling

continues. The cold piston, powered by flywheel momentum (or

other piston pairs on the same shaft) compresses the remaining part

of the gas.

4. Gas reaches its minimum volume, and it will now expand in the

hot cylinder where it will be heated once more, driving the hotpiston in its power stroke.
http://en.wikipedia.org/wiki/File:Alpha_Stirling_frame_8.pnghttp://en.wikipedia.org/wiki/File:Alpha_Stirling_frame_4.pnghttp://en.wikipedia.org/wiki/File:Alpha_Stirling_frame_16.pnghttp://en.wikipedia.org/wiki/File:Alpha_Stirling_frame_12.png


42/236

Beta stirling engine

1. Power piston (up)

has compressed the

gas, the displacer

piston (down) has

moved so that most

of the gas is adjacent

to the hot heat

exchanger.

2. The heated gas

increases in pressure

and pushes the power

piston to the farthest

limit of the power

stroke.

3. The displacer piston

now moves, shunting

the gas to the cold

end of the cylinder.

4. The cooled gas is

now compressed by

the flywheel

momentum. This

takes less energy,

since when it is

cooled its pressure

drops.


43/236

Gamma stirling engine1. Heating

During this phase, theengine piston movesslightly the overall volumeis minimal. In contrast, thedisplacer carries out a longrace and the gas is heated.

2. ExpansionThe displacer moves little.In contrast, the operatingpiston carries out morethan 70% of its race. Itrecovers energy.


44/236

Gamma stirling engine3. Cooling

The displaser carriesout most of its race:the gas is cooled. Theoperating piston

moves littel.

4. CompressionThe displacer remains atthe top: the gas is cold.However, the pistonengine performs themajority of its race: itcompresses the gas byyielding mechanicalenergy.


45/236

AssignmentCentral generation (CG) and distributed generation(DG):

Definition.

Technologies used in DG & CG.

Advantages and disadvantages.

Feasibility study on 100kW Wind/PV power plant(DG/CHP) for hospital with maximum 5 year

payback period. Conclusion (you opinion)

References

d d h f


46/236

Advanced techniques for energy

conversion Co-firing: combining two or more type of fuels

in one system

Combined cycle: combining two or more type

of generation technology in one system

Co-generation: Generate different types of

power outputs such as thermal output

additional to the electrical generation.


47/236

Co-firing Low grade fuels when available at low cost or

are co-fired with higher grade to maintain

acceptable generation efficiency.

Conventional fossil fuels are co-fired with

renewable fuels, Thus:

1. A significant drop in CO2 emissions can be

achieved, lowering green house effect.

2. A considerable pollution drop.

iffi l i f fi i bl d


48/236

Difficulties of co-firing renewable and

fossil fuels Renewable energy has higher volume with

lower heating value, thus, high co-firing ratio

results in a major modifications on the

system, which is not economical. Inevitable drop in overall system efficiency.

Additional modification and operation cost

even with low co-firing ratio.


49/236

Combined cycle This term is used for the systems with two or

more thermal engines commonly Gas/steam

turbines or IC engine/steam-turbine in one

system. Lately, hybrid systems term is used for IC

engine, GT or MGT and fuel cell combinations.

Combined cycle efficiency can increase up to50%.


50/236

Gas turbine combined cycleExamplesSteam turbine place

Efficiencycan go up to

80%

Combinedcycle

Boiler at GT exhaust

ICE-CC

IGCC

GT-CC

Boiler insidecombustor

CC -PFBC

G bi bi d l (GT CC)


51/236

Gas turbine combined cycle (GT-CC)

GT CC


52/236

GT-CC

I t l b ti i bi d


53/236

Internal combustion engine combined

cycle (ICE-CC)

I t t d ifi ti bi d l


54/236

Integrated gasification combined cycle

(IGCC)

Combined cycle with pressurized


55/236

Combined cycle with pressurizedfluidized bed combustor (CC-PFBC)

S lid id f l ll i t bi


56/236

Solid oxide fuel cell-micro gas turbine

hybrid system (SOFC-MGT)

C ti bi d h t d


57/236

Co-generation or combined heat and

power (CHP)Examples

Based on the thermalpower priority

Efficiencycan go up

to 80%

Co-gen.

Topping cycle (heatextraction at exhaust). Elec.

Gen. priority

ICE-CHP

GT-CHP

Bottoming cycle (heatextraction at combustor).Thermal power priority

Hightemperaturecement kiln



58/236


heat and power (ICE-CHP)

Gas turbine combined heat and power


59/236

Gas turbine combined heat and power

system (GT-CHP)


60/236

Direct energy conversion Thermionic energy conversion (TEC)

Thermoelectric Power Conversion

Magnetohydrodynamic Power Generation

(MHD)

Thermionic energy conversion


61/236

Thermionic energy conversionVacuum TEC: Not

practical due tomechanical losses

vapor-filled TEC: Filed

with ionized gas such ascesium

TEC

Direct Heat to elec. power

conversion. Electrons start to emit (boil-

off) out of the surface of hot

side and travel through the

gap and condense on coldmaterial

Can go up to 5MW power

plant with efficiency 5-20%.


62/236

Thermoelectric Power Conversion Invented in 1960s as a result of the semiconductor

material development.

It converts directly thermal power difference toelectrical power.

When electrical power is provided, the unitreversed its function and operates as refrigerator.


63/236


64/236

Thermoelectric Power Conversion


65/236

Thermoelectric Power ConversionAdvantages:

High reliability, long life,

Small-size and

No-vibrations

Can be used in a wide temperature range,

from 200 to 1300 K.

Disadvantages: low conversion efficiency, thus, it

is limited only for special applications



66/236


A pressurized, electrically conducting fluid flowsthrough a magnetic field in a channel or duct.Electrodes located on the channel walls parallel tothe magnetic field and connected through an

external circuit enable the electromotive force todrive an electric current.

The fluid has to achieve adequate ionization to getenough conductivity. Alkali materials are the most

suitable candidates. Combined cycle Steam/MHD plant can achieve

about 52.5% efficiency at best, while it can go upto 60% with nuclear, GT and fuel cell.



67/236

Magnetohydrodynamic Power GenerationCan be coupled to DFGT

Can be fired externally through external heat source(i.e. nuclear, steam plant ..etc.)

MHDgenerator


68/236

Energy storageWhy energy storage?1. Periodic energy production (e.g. Solar

power and wind turbine)

2. High load demand (e.g. Peak hours

and emergency use)


69/236

Energy storage typesMechanical energy storage1. Pumped hydro electric storage

2. Compressed air

3. flywheel

Electrical energy storage (batteries)

Chemical energy storage1. Hydrogen

2. Ammonia

3. Reversible chemical reaction

Electromagnetic energy storage

E


70/236

Energy storage cont.Electromagnetic energy storageThermal energy storage1. Sensible heat

2. Latent heat3. Chemical reaction

Biological energy storage

Pumped hydroelectric storage


71/236

p y g(mechanical) Storage plant efficiency is about 65-75%.

High reliability, moderate cost, pollution free.

Flexibility and can go to full load in short time.

Can be cooperated with large power plants.

Eff. =Pp/Pt= mp Hp/mt Ht ; m (kg/s) ; H (m)

Where: HP=H+Hl ; Ht=H-Hl (Ht: head losses)

Compressed air storage (mechanical)


72/236

Compressed air storage (mechanical) Storage plant efficiency is also about 65-75%.

lower reliability (leakage), low cost and pollution free.

Can be cooperated with wind turbine to generatepower at low wind period.

Can be added to GT system with low cost to add morepower at peak period.


73/236

Fly wheel energy storage (mechanical) Flywheels is used widely for smoothening the

reciprocating engines and compressorsoperation.

Energy recovery efficiency can go up to 90%

Steel flywheel and store maximum power of0.06MJ/m3

Materials other than steel were studied widely toincrease maximum power storage.

Storage efficiency can be increased by operatingthe wheel in vacuum.

Fly wheel energy storage (mechanical)


74/236

Fly wheel energy storage (mechanical)Main factors affecting fly wheel storage performance:

Geometry

Materials (density/strength)

Rotation speed

Friction losses.


75/236

Electrical storage (battery)Wh/literJoules/kgWh/kgCost

$ per WhBattery

Type

100146,00041$0.17Lead-acid

320400,000110$0.19

Alkaline

long-life

92130,00036$0.31Carbon-zinc

300340,00095$0.99NiMH

140140,00039$1.50NiCad

230460,000128$0.47

Lithium-ion


76/236

Lead-acid battery

It was invented by Plante in 1860.

It is the most commonly used type.

Pb is twice as dense as PbSO4 in discharge reaction,thus, PbSO4 crystals doesnt fit totally in Pb placesresulting in some PbSO4 dropping to the batterybottom irreversibly.

Total discharge results in consuming all Pb material,Thus, the reverse reaction can not be initiated.

It is recommended not to discharge the batterybelow 50%

Hydrogen energy (chemical)


77/236

H2

O2

H2O

Hydrogen energy (chemical)Reversed reaction torecover power and

produce H2O

Combustionthermal power

Fuel cell


78/236

Hydrogen energy cont. Conversion efficiency can not exceed 60% H2 storage:

1. It has the lowest weight and volume

resulting in low gas storage efficiency2. It has low boiling temperature (-253C)

resulting in higher liquefying requirement

and cost3. Reversible chemical large volume storage asmetal hydrides: FeTiH1.7 FeTiH0.1+0.8H2

( h l)


79/236

Ammonia energy (chemical) Reversible ammonia chemical reaction:

N2+3H2 2NH3

Thus, it is considered as renewable energy.

Direct combustion with no CO2 emissions since it hasno (C) atoms.

Fuel Density,

kg/lt

LHV

MJ/kg

LHV

MJ/lt

Ammonia 0.76 18.6 14.1

bl h l


80/236

Reversible chemical reaction Heat source or concentrated solar power (CSP)

can be used for the forward reaction

High reverse temperature is desirable

Complete reversible reaction without side

reactions

Rapid reaction with high enthalpy changes

(i.e. high energy storage/unit volume)

Separable reaction outputs with stable storage

Reversible chemical reaction cont


81/236

Reversible chemical reaction cont.

One of the disadvantages in first and second reactions is the gas

output where gases should be stored at high pressure (100 bar).

Second reaction was suggested for large 100MW capacity CSPEFGT with helium as the working fluid.

Third reaction satisfies most of the reversible chemical reaction

criteria mentioned in last slide.

Reversible chemical reaction cont


82/236

Reversible chemical reaction cont.

Alkali materials such as (Na, K and Mg) can react in reciprocal

salt pairs double conversion: (alk)(OH)2+heat= (alk)O+H2O

as been investigated by the power system group of Rockwell

International.

El i


83/236

Electromagnetic energy storage Super-conducting material has low resistance

0 in the range (-150 to -273C)

Commercial alloys such as Niobium-titanium

(Nb-Ti) and Niobium-tin (Nb3-Sn)

Electromagnetic energy storage cont.


84/236

Electromagnetic energy storage cont. Highest energy store (EB) is for the square coil, a=b

R=(3/2)b, for Brooks coil:

EB = 3.028x10-8 V5/3 j2

Where: j (current density)=N(number of coil turns) I(current) /ab For cylindrical coils other than Brook coil:

E = EB .F where F


85/236

Sensible heat storage (thermal)

Sensible heat is thermal energy that results intemperature rise when added to material.

Energy storage depends on the material properties

and temperature rise: Qs/V = .Cp.T


86/236


87/236

Sensible heatstorage

Single tank

Singlemedium

Dual medium

Dual tank(hot-coldsystem)

Single tank heat storage


88/236

Single tank heat storage


89/236


90/236

Ad t f l t t h t t


91/236

Advantages of latent heat storage L>>Cp, thus, latent heat provides more

thermal compared to sensible heat.

Thermal storage and discharge occurs at

constant temperature with limited changes involume that simplifies the system significantly.

The wide variety of materials with different

fusion and evaporation temperatures thatmeets wider range of requirements.

Suggested materials for latent heat


92/236

gg

storage1. Glaubers salts (Na2SO4.10H2O). Fusion reaction

occurs at low temperature of 32C as following:

Na2SO4.10H2O+243kJ/kg Na2SO4+ 10H2O

2. Water has very high latent heat of evaporationof 2250kJ/kg, however, steam storage with high

capacities is not practical. Thus, ice melting is

more suitable.

3. Fe(NO3)2.6H2O that has congruent melting.


93/236



94/236

gg

storage cont.5. Salt eutectics: allow melting temperature of

the mixture to be lower than that for the

individual mixture compounds.



95/236

gg

storage cont.6. High temperature storage materials: For high

temperature applications (200-450C), materials withhigh fusion temperature provide the advantage ofthermal storage at constant temperature with lowvolume.

Biological storage


96/236

Biological storage Solar energy stored in plants through

photosynthetic process is considered as a

biological energy storage.

Similarly, fossil fuels presents a biologicalstorage of energy for millions of years.

Energy recovery of discharge is achieved by

the combustion of fossil and biomassmaterials.


97/236

Oil and gas transmission


98/236

Oil and gas transmission


99/236

Electricity transmission


100/236

Electricity transmission I(current)=P(power)/V(volt)

P=I2/R(resistanse)

Heat transmission


101/236

Simple heat pipe: for short distances and depends on

thermal losses and insulation materials:Qloss. = -kA T/x

(k: thermal conductivity; x: insulator thickness)

Chemical heat pipe: for long distances up to 100km,

using reversible chemical reaction.

Conventional petroleum


102/236

p

In general petroleum refers to all liquid, gaseous, and

solid inside oil well. An oil well produces predominantly crude oil, with some

natural gas dissolved in it.

The petroleum industry generally classifies crude oil by

the geographic location it is produced in (e.g. Brent, orOman), its API gravity (an oil industry measure ofdensity), and its sulfur content.

Crude oil may be considered light, medium and heavy

based on density. It may be referred to as sweet if it contains relatively

little sulfur or sour if it contains substantial amounts ofsulfur.

Light and heavy crude oil


103/236

The lighter grades of crude oil have the advantage

of yielding more useful products with simpler andcheaper refining process, but, with more light andmedium oil depletion, oil refineries are increasinglyhaving to process heavy oil and bitumen, and use

more complex and expensive methods to producethe products required.

Heavy crude oils contains high carbon and lowhydrogen, thus, additional processes are required

to add hydrogen to the molecules, and also usingfluid catalytic cracking to convert the longer,complex molecules in the oil to the shorter, simplerones in the fuels.

Crude oil refining


104/236

Fractional distillation is the oldest and most common way of oil

refining. Different oil fractions are separated based on its boiling

temperature. Basically, oil is heated up until it evaporate and then

condense the vapor.

Newer techniques were added to the conventional refining methods.

Chemical processing is used to enhance the conversion process and

to improve the products quality. For example, breaking longer chainsinto shorter ones, That allows a refinery to turn diesel fuel into

gasoline depending on the demand for gasoline.

Additional treatment for the fractions is required to remove

impurities.

Refineries combine the various fractions (processed, unprocessed)

into mixtures to make desired products. For example, different

mixtures of chains can create gasoline with different octane ratings.

Products are stored for the market delivery and wastes are treated

for the further processing.

Fractional distillation


105/236

Steam boiler is usually used to evaporate the oil.

Oil vapor is then inserted from the bottom of thevertical distillation column that contains oilcollection trays.

Vapor cools down gradually toward the column top,and the different compositions condense atdifferent temperatures through the column height.Collected oils are then discharged through different

ports. Oils (or light gas) are further cooled and then

passed to chemical processing or directly to thecollection tanks.

Chemical processing


106/236

Main chemical process are:

Cracking: breaking large hydrocarbons into

smaller pieces

Unification: combining smaller pieces to makelarger ones

Alteration: rearranging various pieces to make

desired hydrocarbons


107/236

Cracking (catalytic cracking)


108/236

Catalytic: catalysts are used to speed up the

cracking reaction. Catalysts include zeolite,

aluminum hydrosilicate, bauxite and silica-

alumina. A hot, fluid catalyst at 538C cracks

heavy gas oil into diesel oils and gasoline. Asimilar type is the hydrocracking, but uses a

different catalyst, lower temperatures, higher

pressure, and hydrogen gas. It takes heavy oiland cracks it into gasoline and kerosene (jet

fuel).

Unification


109/236

Smaller hydrocarbons are combined to make

larger ones to be more useful. The major

unification process is called catalytic reforming

and uses a catalyst (platinum, platinum-rhenium

mix) to combine low weight naphtha intoaromatics, which are used in making chemicals

and in blending gasoline. A significant by-

product of this reaction is hydrogen gas, which isthen either used for hydrocracking or sold.


110/236


111/236

Distillation column with chemical


112/236

processing

Crude oil refining outputs


113/236

Boiling

rangeContainsUsesFuel name

< 40Csmall alkenes (1 to 4

carbon atoms)

methane, ethane,

propane and butane

Usually converted to

liquefied petroleum gas

(LPG) for heating, cooking

and transport fuel

Petroleum

gas

60-

100C

alkenes (5 to 9

carbon atoms)

Intermediate for gasoline

manufacturing process

Naphtha or

Ligroin

40-

205C

mix of alkenes and

cycloalkanes (5 to 12carbon atoms)

Motor fuelGasoline

175-

325C

mix of alkenes and

aromatics(10 to 18

carbon atoms)

Fuel for jet engines and

tractors; can be converted

to other products

Kerosene

Crude oil refining outputs cont.


114/236

Boiling

rangeContainsUsesFuel name250-

350C

alkenes containing 12 or

more carbon atoms

Engine fuel and heating

oil; can be converted to

other products

Diesel

distillate

300-

370C

long chain (20 to 50

carbons) alkenes,cycloalkanes, aromatics

motor oil, grease, other

lubricants

Lubricating

oil

370-

600C

long chain (20 to 70

carbon atoms) alkenes,

cycloalkanes, aromatics

Industrial fuel; starting

material for making

other products

Heavy Fuel

oil

>600

C

multiple-ringed

compounds with 70 or

more carbon atoms

Starting material for

making other products

Solid

Residuals

asphalt, tar,

waxes, coke


115/236

Oil sands


116/236

Oil that escapes the reservoirs are biodegrade by

bacteria. Oil sands are reservoirs of partiallybiodegraded oil still in the process of escaping andbeing biodegraded, but they contain so muchmigrating oil that, although most of it has escaped,

vast amounts are still presentmore than can befound in conventional oil reservoirs. The lighterfractions of the crude oil are destroyed first,resulting in reservoirs containing an extremelyheavy form of crude oil, called crude bitumen inCanada, or extra-heavy crude oil in Venezuela.These two countries have the world's largestdeposits of oil sands.

Oil shales


117/236

Oil shales are organic-rich sedimentary rocks that

have not been exposed to heat or pressure longenough to convert their trapped hydrocarbons intocrude oil. These rocks containing an insolubleorganic solid called kerogen.

USA has the world's largest oil shales deposits.

Oil extraction from the rock can be done bypyrolysis were heat is supplied (340-370C) in the

absence of Oxygen. Refining the oil presents more technical and

environmental difficulties compared to crude oil.

Natural gas


118/236

Natural gas can be found in oil fields or isolated

in natural gas fields, and is also found in coalbeds as coal-bed methane.

It consisting primarily of methane, typically with020% higher hydrocarbons (primarily ethane).

It is considered as the most environment-friendly fossil fuel due to its low emissions.

Compressed Natural Gas (CNG) is the most used

from of the gas for power generation. For vehicular usage, Liquefied Natural Gas (LNG)

is also used.


119/236

Coal

It is in the middle stage between wood and coal. It has high moisture content85% and low fixed carbon 5%. After drying, peat can be converted into brackets

or pellets and used in furnaces. In its dehydrated form, peat is a highly effective

Peat


120/236

absorbent for fuel and oil spills on land and water. It is also used as a conditioner

for soil to make it more able to retain and slow release water.

lowest rank of coal and used almost exclusively as fuel for electric power

generation. It has high moisture content (35-70%), thus it has to be dried before

using in power plants.

Lignite

(brown coal)

properties range from those of lignite to those of bituminous coal, is used

primarily as fuel for steam-electric power generation and is an important sourceof light aromatic hydrocarbons for the chemical synthesis industry.

Sub-

bituminous

dense sedimentary rock, black but sometimes dark brown often with well-

defined bands of bright and dull material, used primarily as fuel in steam-electric

power generation, with substantial quantities used for heat and power

applications in manufacturing and to make coke.

Bituminous

the highest rank of coal is a harder, glossy, black coal used primarily for

residential and commercial space heating and it has blue smokeless short flame.

Anthracite

technically the highest rank is difficult to ignite and is not commonly used as

fuel: it is mostly used in pencils and, when powdered, as a lubricant.

Graphite

Coal


121/236

BTU/lb=2.3kJ/kg


122/236

Nuclear power

Nuclear fuel processing


123/236

Nuclear fuel processing


124/236

After raw material mining, milling process includes:

crushing and grinding to small pieces. Leaching in acid to dissolve metals, then, ion-

exchange to separate Uranium from other metals.

Milling output (U3O8) is the yellow cake. In processing stage: Yellow cake is purified

chemically with Fluorine to produce UF6.

Enrichment: mechanical separation between U235

and U238 by pressing UF6 gas through porous barrieror by more modern gas centrifugal separators.

Natural uranium (U235


125/236

In Fabrication, UF6 is converted first to UO2 that is

fabricated into cylindrical pellets to form the fuelpins.

During the reactor operation, careful fuelmanagement for homogeneous fuel consumptionthat can extend up to 18-24 month.

The highly radioactive fuel is stored and cooled ininterim stage for at least 90 days.

Residual Uranium and plutonium are processed forrecycling and then fuel is disassembled.

In waste disposal, fuel is liquefied and stored for atleast 5 years, then solidified for final disposal.

Basic common reactors in the world


126/236

Number of coolant loops


127/236

1-Single loop 2-two loops 3-three loops

1 2

3


128/236

Nuclear economics (reactor and steam efficiency)


129/236

Nuclear plants has lower steam efficiency of about

29% with normal or heavy water primary cooler dueto the limitation in temperature.

Steam efficiency can go up to 39% with helium forthe primary cooler since it can go up to 700C.

Pressurized water reactors provide better reactorthermal power utilization compared to boiling waterreactor. Gas cooling provides higher utilization butwith more technical risk:

1. Higher working temperature.

2. Much longer cooling time for emergency shut-down.


130/236

nuclear reactors crisis


131/236

Discuss the following:1. Reactors comparison based on Hazarders potential.

2. Two case-studies (Russia, Japan).

3. Safety aspects in nuclear reactors.

Finally, conclude with your opinion on future safe

reactors.


132/236

Renewable energyFirst:

Wind power

Commercial WT sizes in USA


133/236

Betz limit


134/236

Betz's law was developed in 1919 by the

German physicist Albert Betz.

The theory estimates the maximum possible

energy to be derived from a wind turbine isabout 59.3% of the kinetic energy in wind.

power coefficient (Cp) = power output from

wind machine / power available in wind. Modern horizontal axis wind turbine can

reach 65% to 75% of the theoretical Betz

limit

Modern wind turbines


135/236

Vertical axis

VAWT

Darrieus

Giromill Savonius

TwistedSavonius

Horizontal axis

HAWT

Downwind

upwind

Horizontal and vertical wind turbines


136/236

VAWTHAWTTurbine doesnt require to face the

windNeed to faces the windLower efficiencyHigher efficiency

Higher pulse torque (reciprocating)

Lower continuous torque (smooth)

Gear box and generator are on the

ground, resulting in lighter construction

(shorter construction)Generator and gear box has to be lifted

above high tower resulting in heavy

construction tower.Lower rotation speed

Higher rotation speed

Can operate at low wind speedOperates only at high wind speed

Many designs require startup motorSelf starting

HAWT

D i d U i d


137/236

Downwind Upwind

HAWT


138/236

UpwindDownwindThe rotor is in the front of the

unitThe rotor is behind the towerRequires stiff blades to avoid

hitting the tower

Flexible blades can be used

More expensive bladesLess expensive bladesLess wind turbulence on the

blades

suffer from fatigue and structural

failure caused by turbulence when a

blade passes through the tower's wind

shadowseparate long yaw mechanism is

required

Shorter yaw mechanism

Preferred for small scaleBecoming more popular for largescales

HAWT


139/236

It has air foil design blades like that spin on the

horizontal axis.

The blades gearbox and electrical generator are

all at the top of a tower, and they must be

pointed into the wind. Small turbines are

pointed by a simple wind vane, while large

turbines generally use a wind sensor coupledwith a motor.

Tall tower allows access to stronger wind in sites

with wind shear. In some wind shear sites, every

ten meters up the wind speed can increase by20% and the power output by 34%.

Massive tower construction is required to

support the heavy blades, gearbox and

generator.

HAWT cont.Hi h ffi i i th bl d l


140/236

High efficiency, since the blades always move

perpendicularly to the wind, receiving power through the

whole rotation. In contrast, all vertical axis wind turbines

involve various types of reciprocating actions, requiring

airfoil surfaces to backtrack against the wind for part of the

cycle. Backtracking against the wind leads to inherently

lower efficiency.

HAWTs generally require a braking device in high winds to

stop the turbine to prevent damage.

When the turbine turns to face the wind, the rotatingblades act like a gyroscope, resulting in forward or

backward twist for the blades. This cyclic twisting can

fatigue and crack the blade roots, hub and axle of the

turbines

Darrieus or Eggbeater wind turbines


141/236

by Georges Darrieus in 1931.

Moderate efficiency. Large torque ripple and cyclic stress

on the tower, which contributes to

poor reliability.

Starting torque is very low, thus, it

requires external startup power

source.

Torque ripple is reduced (smoothoperation) by using three or more

blades which results in a higher

solidity for the rotor.

Helical blades wind turbines


142/236

It is a modified Darrieus wind turbine.

It has three blades and a helical twist of 60 degrees. Torque is spreader evenly over the entire revolution

resulting in smoother rotation and preventing

destructive pulsations.

Giromill


143/236

It is like Darrieus turbinewith straight blades.

Simpler and cheaper but

less efficient compared toDarrieus turbine.

Requires startup motor.

Giromill (cyclo-turbine)


144/236

Each blade can rotate around its own vertical axis.

The blade changes its angle of attack relative to the wind,resulting in smoother torque.

Torque remains near maximum for longer rotation angleproducing more net torque.

More efficient operation in turbulent winds with lower bladebending stress.

Self starting.


145/236

Twisted Savonius


146/236

It is a modified savonius withlong helical scoops.

Low cost high reliability.

Low efficiency.

Produces smooth torque.

Can be used for low heights low

power applications such as onroof or on boat wind turbine.


147/236


148/236

Biomass


149/236

Biomass refers to any organic substance from

plant materials or animal wastes used as fuels. Itincludes for example, agricultural residues,

urban wastes even sewage sludge waste.

Three main biomass conversion processes:1. Direct combustion

2. Biological conversion

3. Thermochemical conversion:

Pyrolysis

Gasification


150/236

Biological conversion


151/236

Biomass is converted into biogas by anaerobic

digestion process in the absence of air, eitherin landfill or modern biogas plans.

wet organic waste decomposing by bacteria

into biogas, however, in landfill digesters, theconversion takes long time (about month).

In modern biogas plans, CHP gas engines are

used for electrical out put as well as providingheat for the digesting tanks to accelerate the

conversion process.


152/236


153/236

Biological conversion

b b b


154/236

Anaerobic digesters can be designed based on:

1. Process flow: Batch (simpler and cheaper design)or continues (complex and more efficient)

2. Temperature: Mesophilic (20-40C) orthermophilic (50-70C) more stable with fasterproduction rate.

3. Solids content: High solids or low solids (liquidform).

4. Complexity: Single stage (less reaction control) ormultistage (different type of bacteria in differentstages to achieve maximum control andperformance.


155/236

Biogas cont.


156/236

High H2S content presents a technical

difficulty for running IC engines and gasturbines directly (corrosion problem). Biogas

has to be passed through water scrubber to

remove H2S.

Biogas is upgraded to bio-methane (80-90%

methane) by purification process thatremoves CO2 and the corrosive H2S to be

useful in electrical generation and transport.

Biodiesel

Bi C ll l th l


157/236

Biomass Cellulose sugar methanol

Vegetable oils or animal fats are mixed withmethanol to produce biodiesel.

Biodiesel has more viscosity compared to

diesel, thus, it has to be preheated or mixedwith normal diesel for IC engine.

Biodiesel grades:B100 for 100% biodiesel; B20

for 20%biodiesel and so on.

Pyrolysis Thermochemical reaction or decomposition of


158/236

Thermochemical reaction or decomposition of

biomass material in the absence of air toproduce combustible materials such as char,gas and oil. The product mix depends on thetemperature, heating rate and time of the

process. Types of pyrolysis:

Fast and flash pyrolysisFast and flash pyrolysis are the most studied types


159/236

Fast and flash pyrolysis are the most studied types

since they yield high amount of bio-oil. Followingconditions are required:

Very high heat transfer rates is required, thus,

biomass has to be finely ground. Carefully controlled reaction temperature.

Low residence time of pyrolysis vapors in the

reactor. Quenching (rapid cooling) of the pyrolysis vapors

to give the bio-oil product.


160/236

Gasification


161/236

Thermochemical reaction of biomass material

that occurs in limited presence of oxygen with

a higher temperature levels. The output

product is a low heating value gas fuel known

as producer gas or syngas.

Oxidizer types:

1. Oxygen: gas heating value can go up to

2. Steam: gas heating value

3. Air: gas heating value (4-8Mj/m3)

Gasification cont. Thermochemical Zones inside Gasifiers:


162/236

Thermochemical Zones inside Gasifiers:

1. Drying zone: heat from combustion zone is used todry biomass.

2. Pyrolysis zone: oxygen doesnt reach to this zone,

dry biomass is converted into char coal , volatilesand tar at 200-350C.

3. Oxidation or Combustion Zone: crated at the

oxidizer inlet and its size depends on oxidizer flow

rate. Provides heat for other zones.

4. Reduction or Gasification Zone: produces the gas at

400-800C with limited amount of oxidizer

GasifiersFixed Fluidized Suspension


163/236

bed

Updraft

Downdraft

Crossdraft

bed

Bubbling

BFB

Circulating

CFB

Suspension

Cyclone

Fixed bed gasifiers


164/236

Other biomass benefits: bio-products

The petrochemical industry makes many products from fossil


165/236

The petrochemical industry makes many products from fossil

fuels such as plastics, chemicals, and other product. Thesame or similar products can, for the most part, be made

from biomass.

Bioproducts that can be made from sugars include antifreeze,

plastics, glues, artificial sweeteners, and gel for toothpaste. Bioproducts that can be made from carbon monoxide and

hydrogen of syngas include plastics and acids, which can be

used to make photographic films, textiles, and synthetic

fabrics. Bioproducts that can be made from phenol, one possible

extraction from pyrolysis oil, include wood adhesives,

molded plastic, and foam insulation.


166/236

Renewable energy

Geothermal

Introduction Core of earth can reach up to 4000C due to the


167/236

Core of earth can reach up to 4000 C due to thedecay of radioactive materials.

The temperature at the base of crust is about1000C and the average heat flow towards thesurface is about 0.063W/m2.

Certain regions on earth has the molten rocks(magma) pushes towards the surface throughweak zones and cracks creating hot spots 2-3kmbelow surface.

One of the main advantages of geothermal is theavailability around the clock (constant all day long)unlike solar or wind energy.


168/236

Geothermal systeml


169/236

Main elements:

Heat source: can be high-temperature magmatic

instruction (5-10km depth) or low-temperature

earths normal temperature graduation (2.5-3

C/100m).

Reservoir: is a volume of hot permeable rocks

where fluid circulates.

Fluid: pure water or mixed with othercompositions such as CO2, H2S, etc.


170/236

Geothermal resources and use


171/236

Low enthalpy resources 150C.

Geothermal uses:

Direct use using hot springs for bathing.

Electrical generation.

Thermal uses:

1. Cooling2. Heating

Green house heating (plantation)

Geothermal for electrical generation For research geothermal is studied widely with


172/236

For research, geothermal is studied widely with

thermal to electric devises. However, Rankin based systems are the most

commercially used for electrical generation.

Based on gen.size & position

Generation plant

Wellhead gen. Central gen.

Wellhead & central generationcentralWellhead


173/236

Large scale(average of 30-50MW)

Small scale


174/236

Atmospheric exhaust turbine is simpler, cheaper but lower in efficiency

(exhaust 1bara)

Condensing plant: turbine is more complicated and expensive but more

efficient (exhaust 0 2bara)


175/236

Commercial geothermal power plants


176/236

Dry steam power plants.

Flash steam power plants.

Binary power plants.

Biphase steam power plants:

1. Topping cycle arrangement.

2. Bottoming cycle arrangement.

Dry steam power plants One of the first


177/236

One of the first

technologies in 1904,at the same Larderellodry steam field.

Limited availability,depends on the wellproperties and theextraction depth.

Simple design since itdoesnt require water

separator. The largest dry steam

field in the world is theGeysers in USA.

Flash steam power plants It is the most common technology.


178/236

It is the most common technology.

Pressurized hot water >150C remains inliquid form with.

This very hot water flows up through wells inthe ground under its own pressure.

As it flows upward, the pressure decreasesand some of the hot water boils into steam ina flash tank and steam is separated from the

water. Separated water and condensed steam are

injected back into the reservoir.

Flash steam power plants


179/236

Binary power plants Can operate on water at lower temperatures


180/236

p p


181/236

Steam vs. hydrocarbon fluid


182/236

Steam vs. hydrocarbon fluid cont.HydrocarbonSteam


183/236

Operates with wider range of

temperatures

Operates with medium and

high temp. wells

Much higher pressure at similar

temp.

Low pressure cycle

Higher overall eff.Lower overall eff.Dry gas expansionSaturated steam expansion

Low enthalpy, simple single stage

turbine is enough

High enthalpy, multi-stage

turbine is required

Smaller turbine and condenser is

required

Higher density and volume,

larger system components

Positive pressure condenserLow pressure condenser, air

can leak to the system

Biphase rotary separator turbo-alternator Can extract power from two-phase water/steam


184/236

flow trough three main components:1. Two-phase nozzle: increasing kinetic energy ofwater/steam (pressure drop).

2. Rotary separator: separates them by centrifugal

force. Steam is passed to steam turbine.3. Liquid turbine: power is generated from the

pressurized water then re-injected to the well.

It can be put before the steam turbine (toppingcycle).

It can be put after the steam turbine cycle(bottoming cycle).

Biphase topping cycle plant


185/236

Smaller biphase units can be used due to the lower

specific volume

Biphase bottoming cycle plant


186/236

Larger biphase units is required due to the higher specific

volume

Geothermal heat pump (GHP) Works in principle as the conventional air-con.


187/236

Works in principle as the conventional air con.

Heat pump but takes the advantage of theconstant geothermal temp. (7-21C) through

the year.

Works as cooler in summer and as heater inwinter.

Provides 25%-50% electrical savings depends

on temperature range available. GHP piping can be drilled under ground (soil) or

submerged in water (lake or well).

GHP


188/236

Closed loop

Pondor

lake

Vertical

Horizontal

Open loop

Lakeor

drilledwell


189/236


190/236

Require pond or lake.

Low cost.

Lake or drilled well until wateris reached.

Lowest cost.

Water is the transfer medium.

Geothermal for refrigeration and airconditioning


191/236

Two fluids are used such as Lithiumbromide/water or Ammonia/water (one of it hashigh absorption capacity for the other).

Main power input is thermal (hot water orsaturated steam) with very low elec. Required forliquid pumps.

Low COP usually


192/236

Ocean Thermal Power Conversion (OTPC) power plants Water T

between surface


193/236

between surface

and deep wateris limited


194/236

Close-cycle turbine: Low

boiling temp. fluids are

used such as ammonia torotate the turbine.

Open-cycle turbine: some of ocean water boils at lowpress./temp. condition and saturated steam drives theturbine.

Steam condenses to a desalinated water.


195/236


196/236

Renewable energy

Hydrogen energy

(Fuel cell)

What is Fuel cell? It is an electrochemical device that generates electricity

directly from the chemical energy in fuel (mainly hydrogen)


197/236

directly from the chemical energy in fuel (mainly hydrogen)

although some other hydrocarbons were also studied.

When hydrogen is used, reversed electrolysis process occurs.

In electrolysis, water molecules split into hydrogen and

oxygen molecules by consuming electricity whereas in fuel cell

reaction, hydrogen and oxygen molecules combine to produce

water and electricity.

Unlike conventional power generation systems, fuel cells do

not involve intermediate conversion of chemical energy to

thermal and mechanical energies. Consequently, of all the

existing energy conversion systems, fuel cells offer the highest

efficiency along with the lowest levels of pollutant emissions.

Electrolyte: Potassium hydroxide (KOH)

solution retained in an asbestos matrix

Electrodes: Transition metals loaded

with platinum or other electro-catalysts

Operating temperature: 65-220C
http://2.bp.blogspot.com/_y61ZSLn8jyE/TQttIdYPaaI/AAAAAAAAAFw/Qtxq6Edw8T4/s1600/fctype_AFC.jpghttp://2.bp.blogspot.com/_y61ZSLn8jyE/TQttIdYPaaI/AAAAAAAAAFw/Qtxq6Edw8T4/s1600/fctype_AFC.jpghttp://2.bp.blogspot.com/_y61ZSLn8jyE/TQttIdYPaaI/AAAAAAAAAFw/Qtxq6Edw8T4/s1600/fctype_AFC.jpghttp://2.bp.blogspot.com/_y61ZSLn8jyE/TQttIdYPaaI/AAAAAAAAAFw/Qtxq6Edw8T4/s1600/fctype_AFC.jpg


198/236

Electrical efficiency: ~60%. Applications: Military, space.

Advantages

- Superior cathode reaction kinetics

- Quick start-up due to low temperatureoperation

- Low weight and volume

Disadvantages

- Extremely intolerant to carbon dioxide(as a result pure oxygen or the air free

of carbon dioxide should be used as the

oxidant)

- Electrolyte handling problems

- Relatively short lifetimeAlkaline fuel cell (AFC)

Electrolyte: Liquid phosphoric acid

soaked in a silicon carbide (SiC) matrix

Electrodes: Carbon loaded with platinum


Electrical efficiency: ~40%.
http://2.bp.blogspot.com/_y61ZSLn8jyE/TQttIdYPaaI/AAAAAAAAAFw/Qtxq6Edw8T4/s1600/fctype_AFC.jpghttp://2.bp.blogspot.com/_y61ZSLn8jyE/TQttIdYPaaI/AAAAAAAAAFw/Qtxq6Edw8T4/s1600/fctype_AFC.jpghttp://2.bp.blogspot.com/_y61ZSLn8jyE/TQttIdYPaaI/AAAAAAAAAFw/Qtxq6Edw8T4/s1600/fctype_AFC.jpghttp://4.bp.blogspot.com/_y61ZSLn8jyE/TQtuA73TOeI/AAAAAAAAAF4/zbTleRdfWYc/s1600/fctype_PAFC.jpghttp://4.bp.blogspot.com/_y61ZSLn8jyE/TQtuA73TOeI/AAAAAAAAAF4/zbTleRdfWYc/s1600/fctype_PAFC.jpghttp://4.bp.blogspot.com/_y61ZSLn8jyE/TQtuA73TOeI/AAAAAAAAAF4/zbTleRdfWYc/s1600/fctype_PAFC.jpghttp://4.bp.blogspot.com/_y61ZSLn8jyE/TQtuA73TOeI/AAAAAAAAAF4/zbTleRdfWYc/s1600/fctype_PAFC.jpghttp://4.bp.blogspot.com/_y61ZSLn8jyE/TQtuA73TOeI/AAAAAAAAAF4/zbTleRdfWYc/s1600/fctype_PAFC.jpg


199/236

y

Applications: DGAdvantages

- Less sensitive to CO poisoning than

PEFC and AFC

- Waste heat can be utilized in combined

heat and power (CHP)applications/bottoming Rankin (steam

turbine) cycle

Disadvantages

- Corrosive nature of electrolyte which

necessitates the use of expensive

materials in the stack

- Poor operating reliability in the long

term

Phosphoric acid fuel cell (PAFC)

Electrolyte: Fluorinated sulfuric acid polymer (commonly Nafion)


Fuel: Pure hydrogen

Polymer electrolyte fuel cell (PEFC)
http://4.bp.blogspot.com/_y61ZSLn8jyE/TQtuA73TOeI/AAAAAAAAAF4/zbTleRdfWYc/s1600/fctype_PAFC.jpghttp://4.bp.blogspot.com/_y61ZSLn8jyE/TQtuA73TOeI/AAAAAAAAAF4/zbTleRdfWYc/s1600/fctype_PAFC.jpg


200/236

Fuel: Pure hydrogen


Electrical efficiency: 40-60%.

Applications: Automotive, portable applications, small scale DG.

Advantages- No corrosion and electrolyte management problems.

- Quick start-up due to low temperature operation.

- High power density (over 2 kW/l and 2 W/cm2).

Disadvantages

- Highly sensitive to impurities of hydrogen (Pure hydrogen only).

- Difficulty in water management ensuring sufficient hydration of the

electrolyte membrane against flooding.

Electrolyte: Mixture of molten carbonate

salts (lithium carbonate + potassium

carbonate/sodium carbonate) retained

in a ceramic matrix (LiAlO2)

Electrodes: Nickel (anode) and nickel

id ( th d )
http://3.bp.blogspot.com/_y61ZSLn8jyE/TQtuq2g-Y2I/AAAAAAAAAGA/jqRofuW2boQ/s1600/fctype_MCFC.jpg


201/236

oxide (cathode)


Electrical efficiency: : ~60 %.

Applications: Electric utility, large DG.

Advantages

- No need of expensive electro-catalysts- Fuel flexibility (Hydrogen, CO, methane,

etc)

- High grade waste heat (suitable for CHP

applications/bottoming cycles)

Disadvantages

- Very corrosive nature of the electrolyte

- Material problems due to high

temperature operation

- Sulfur content (1.5 ppm max.)

- Slow start-upMolten carbonate fuel cell (MCFC)
http://3.bp.blogspot.com/_y61ZSLn8jyE/TQtuq2g-Y2I/AAAAAAAAAGA/jqRofuW2boQ/s1600/fctype_MCFC.jpg


202/236

Electrolyte: Fluorinated sulfuric acid polymer


Fuel: Methanol

Direct methanol fuel cell (DMFC)


203/236

Fuel: Methanol

Operating temperature: 50-130 deg. C

Electrical efficiency: ~40%

Applications: consumer electronics (as a replacement of batteries)

Advantages

- Direct use of liquid fuel (can be recharged like batteries by simply

changing the cartridge of fuel)

Disadvantages- Lower efficiency due to methanol crossover problem

- Higher cost due to increased loading of noble metal at anode


204/236

Renewable energy

Wave energy

Wave power The common measure of wave power: P(W/m)


205/236

where:

= the density of seawater = 1,025 kg/m3, g = 9.8 m/s,T = period of wave (s), and H = wave height (m).

Because wind is generated by uneven solar heating,

wave energy can be considered a concentrated form of

solar energy. Incoming solar radiation levels that are onthe order of 100 W/m2 are transferred into waves with

power levels that can exceed 1,000 kW/m of wave crest

length.


206/236

point absorber

It is a floating devise fixed to a generator at


207/236

ocean floor by cable. The vertical motion (up/down) of the float is

used to drive electromechanical or hydraulic

energy converters to generate electricity.
http://ocsenergy.anl.gov/includes/dsp_photozoom.cfm?imgname=wave.jpg&caption=Point%20Absorber%20Wave%20Energy%20Farm&callingpage=/guide/wave/index.cfm&callingttl=Wave%20Energy&source=Source:%20Minerals%20Management%20Service


208/236


209/236

Terminator In terminators, wide wave area on or beside shore is

accumulated in a conical-shape barrier to rotate directly anaxial or horizontal axis turbine An other way is to use the


210/236

axial or horizontal axis turbine. An other way is to use thepressure of the collected water is by moving an oscillatingwater column that drives directly a turbine or pushescompressed air column to drive air turbine.


211/236

Renewable energy

Tidal energy

Tidal elec. power generation Tides are periodic


212/236

Tides are periodicvertical rise andfall of ocean waterbecause of the

gravitational forcesof sun and moon.

Three common configurations are used:

1. Single basin: single effect tidal power scheme.

2. Single basin: double effect tidal power scheme.

3. Linked basin: double basin, single effect.

Single basin single effect tidal power scheme Basin is filled by


213/236

Basin is filled by

keeping the

sluices open

during flood tied.

Sluices are closedand water flows

back through the

turbine (axial ofradial).

Water flows

Single basin double effect tidal power scheme


214/236

Water flows

through the

power house

during both

flood andebb tied

Flood tied fills the

Linked basin


215/236

low then highbasin.

Power house islocated betweenhigh and lowbasins.

Finally, water flows

to the sea from thelow basin duringebb tied.


216/236

Renewable energy

Hydro energy


217/236


218/236

Renewable energy

Solar energy


219/236

Photovoltaics (PV) It is a direct conversion device of light

into electricity at the atomic level.

PV materials absorb photons of light


220/236

PV materials absorb photons of light

and release electrons. When these

free electrons are captured, an electric

current results that can be used as

electricity.

photovoltaic cells, also known as solarcells are made of semiconductor

materials, such as silicon, used in the

microelectronics industry.

A number of solar cells electrically connected to each other and

mounted in a support structure or frame is called a photovoltaic

module. Modules are designed to supply electricity at a certain

voltage, such as a common 12 volts system.

A single-junction PV cell passes only the photons whose energy is equalto or greater than the band gap of the cell material, thus, single-junction PV cells response is limited to the portion of the sun'sspectrum whose energy is above the band gap of the absorbingmaterial, and lower-energy photons are not used.

One way to get around this limitation is to use


221/236

One way to get around this limitation is to usetwo (or more) different cells, with more thanone band gap and more than one junction, togenerate a voltage. These are referred to asmulti junction or cascade cells.

Multi junction devices can achieve a higher total

conversion efficiency because they can convertmore of the energy spectrum of light toelectricity.

As shown in the figure, a multi junction device isa stack of individual single-junction cells indescending order of band gap (Eg). The top cell

captures the high-energy photons and passesthe rest of the photons on to be absorbed bylower-band-gap cells.

photovoltaic (PV) & concentratedphotovoltaic (CPV) PV cells converts light photons directly to electrical


222/236

g p y

output in one-step conversion.

Tremendous amount of materials and designs

have been tested, however commercial PV

efficiency is only about 8% with higher eff. Up to20% for under research cells.

Overall system efficiency can be increased by

concentrating light beams


223/236


224/236

parabolic trough with curvedmirrors that concentrate

radiation on a pipe foreach mirror

linear Fresnel reflectorWith flat mirrors thatconcentrate radiation

on one pipe


225/236

1)Fresnellenses

2) power tower receivesradiation beams fromon-ground reflectingmirrors

3)Dish reflectorconcentrated on

stiriling engine

CSP cont. CSP plants offers high amount of thermal


226/236

p g

power that is usually utilized as CHP plant

for different thermal uses.

CSP is the main candidate for solarrefrigeration although low/medium

temp. solar panels are also used.

Low &medium temp. thermal panels Low and medium temperature collectors provides thermal

power without concentrating the sun radiation.


227/236

power without concentrating the sun radiation.

Low-temp. collectors are flat plates generally used to heatswimming pools and houses. Medium-temperaturecollectors are also usually flat plates but for larger scalewater or air heating for commercial use with moreeffective radiation absorbent materials.
http://en.wikipedia.org/wiki/File:Solar_panels,_Santorini.jpg


228/236

Renewable energy

comparison


229/236

Other

pollution

Green house

effectGas

pollution

Effect on

other life

formsVisualNonNonNonCSP


230/236

Waste materialNonNonLowPV&CPVNoise & visualNonNonLowWind

______NonNonNonWave______NonNonLow/mod.Tied______Mod.Mod./highLowGeo.______NonNonMod./highOTPCSmell, ash

disposalLowMod./highLow/mod.Biomass______High for large

scale hydroNonMod./highHydro


231/236

Wind it has the advantage that it doesn't require cooling

water nor water treatment, thus, no water


232/236

ate o ate t eat e t, t us, o ate

pollution is associated with it.

It generates a considerable noise pollution and

visual disturbance for the landscape view that can

affect the nearby community.

Construction hazards just like other high building

construction.

The effect on life forms especially birds where

many bird killing accidents by the blades were

recorded.

Biomass For biomass fuels, growing plantation or forests for ethanol

production or wood utilization presents a big challenge due tothe huge amounts of water and land is required for economical


233/236

g qbiomass utilization. The other challenge is the regular removaland re-plantation causes a disturbance for other life forms suchas birds and small animals.

High potential for air pollution for single stage combustion andeven in two-stage if combustion was not controlled properly.

The presence of CO2 emissions although it is circulated inbiomass growth cycle.

High machinery maintenance and operation requirement.

Solid waste (ash) disposal requirement. Ash contains valuable

minerals content that has to be returned to the plantation soilfor further plantation growth.

Non-controlled anaerobic digesters can cause an intensive smellpollution that can affect the plant neighbors.


234/236

Geothermal & OTPC Many pollutant gases are dissolved in the

geothermal water such as: carbon dioxide,


235/236

methane, hydrogen sulfide, ammonia, nitrogen andhydrogen, that can be either poisonous orcontributes in global warming.

Flash steam plants have high risk of releasing high

quantities of these gases if not been controlled. Binary plants has much lower risk since water is re-

injected directly to the well after the heatexchanger.

Ocean thermal power plants moves large waterquantities (4m3/s per MW) causing thermaldisturbance around the plant and affecting lifeforms.

Hydro power Large dams results in a submerge of large areas

of land that converts into a reservoir resulting in


236/236

g

a large scale deforestation and loss of wildlife.

For large scale hydro reservoirs, large amount of

greenhouse gas (methane) is emitted from the

stagnant water. This issue is totally avoided in

micro and Pico hydro where turbines are placed

i th i t

Date post:	14-Apr-2018
Category:	Documents
Upload:	-
View:	215 times
Download:	0 times

Power Systems All

Documents