Today

Electric Power LectureCarbon Trading Game Assignment 2 posted

Thursday

Electric Power Distribution and Storage LectureHomework 3 (Conservation) due at start of class

Group homework using eQUESTOne homework/group

Discuss Homework 3Present an example problem to help with Homework 4At 6 pm, reading quiz for Electric Power due

Week 4

ElectricityGeneration, Transmission, and Storage

World Energy Consumption by Service

electricity

transportation

heat

electricity, fossil

electricity, other

transportation, fossil

transportation, other

heat, fossil

heat, other

37 %

25 %

38 %

13 %

11 %

Why Care?

Electricity Consumption by Source

coal

oil

gas

biomass

waste

nuclear

hydro

geothermal

solar PV

solar thermal

otherInternational energy agency, 2003

Where is this electricity coming from?

39.9%

19.3%

16.3%

15.7%

6.9%

0.83%

0.37%

0.0033%

0.0033%

0.40% Includes wind

steam turbine

steam turbinegas and steam turbines

steam turbine

water turbine

How is it created?

So, what are we going to talk about most of the day?

Steam Trivia:

How much water do we (earthlings) change to steam every year in the name of electricity demands?

A. 10 km3

B. 55 km3

C. 6,000,000 m3

D. 190,000,000 m3

Salt Lake holds 16 km3 of water

1200 1500s 1603 1661 17001712

1776 1880 1900

1911 1920 1950 1967 1970

1306 1890

1973

19691940

1942 19481960

1963

19781976

19871988-92

1982 1996-97 20032002 2004

future2001

Britain producing 5x more coal than rest of the world.

Running out of accessible supply.Coal mines had to stop at the water table.

mine

coal

water table

1200 1500s 1603 1661 17001712

1776 1880 1900

1911 1920 1950 1967 1970

1306 1890

1973

19691940

1942 19481960

1963

19781976

19871988-92

1982 1996-97 20032002 2004

future2001

1st Newcomen engine (steam engine) was installed at a mine,to pump water out so they could dig deeper.

And, humans crossed the threshold.

control volume

1st Law of Thermodynamics:

Energyin – Energyout = ∆Energycv

chemical potential energy of coalelectrical energy

zero(on average)

& heat33% 67%

How do we analyze?

workin

boiler

turbine

pump

fuel

air

workout

heatout

heatin

no heatconstant s

no heatconstant s

no workconstant P

no workconstant P

Tboiler

External Combustion Engine

Closed Cycle Reversible Heat Engine

Most efficient type?

condenser

generator

electricity

Carnot

Steam Engine

Tpond

What is the Carnot efficiency?high

lowcarnot T

T1

%67600273

102731

carnot

%50300273

102731

carnot

For coal-fired power plants, maximum Tboiler = 600 °C

Ambient water (or air), Tpond = 10 °C

For nuclear power plants, maximum Tboiler = 300 °C

We keep reading that steam power plants are closer to 33 % efficient. Why the discrepancy?

Reversible closed cycle involving a two-phase substance cannot realize the Carnot efficiency.

T

s

boiler

turbine

pumpworkin

workout

heatout

heatin

condenser

1

2

3

4

What is this plot describing?

superheatedvaporsaturated

liquid & vapor

compressedliquid

Saturation Dome for Water/Steam

criticalpoint constant

pressurelines

Rankine Cycle

1

2

4

wpump,in

wturb,out

qcond,out

qboiler,in3

T

s

boiler

turbine

pumpworkin

workout

heatout

heatin

condenser

1

2

3

4

How do we improve efficiency?

1

2

4

3

Increase area of shape 1234

4’1’

2’

lower condenserpressure

Problems:Pmin

T

s

boiler

turbine

pumpworkin

workout

heatout

heatin

condenser

1

2

3

4

How do we improve efficiency?

1

2

4

3

Increase area of shape 1234

superheat steam tohigher T

4’

3’

Problems:Tmax

Qin limits

T

s

boiler

turbine

pumpworkin

workout

heatout

heatin

condenser

1

2

3

4

How do we improve efficiency?

1

2

4

3

Increase area of shape 1234

increase boiler

pressure

4’

2’

3’

Can we fix this?

Add Reheat

T

s

boiler

turbine

pumpworkin

workout

heatout

heatin

condenser

1

2

3

4

How do we improve efficiency?

1

2

5

Increase area of shape 1234

Preheat feedwater

7

3

4

Regeneration

6

boiler

turbine

pump

fuel

air

workin

workout

heatout

heatin

Tboiler

Tpond

generator

condenser

electricity

in

netcycle q

w

generatorturbinecycleboilercombustionpowerplant

+ air products + heatcoal

heating value of coal = 24 – 35 MJ/kg

CH0.67O0.043N0.010S0.003

(O2 + N2) CO2 + H2O + NO + SO2 + N2

+ air products + heatcoal

CO2 + 0.33 H2O + 0.010 NO + 0.003 SO2 + N2

+

Moles of O2 per mole of C = ½ (2 + 0.33 + 0.010 + 0.006 – 0.043) = 1.1515

1.152

4.261

CH0.67O0.043N0.010S0.003 (O2 + 3.7 N2)

Greenhouse gas

No worries

No worriesToxic & ozone friend

Toxic & PM friend

Toxic

More

Toxic

incompletecombustion

(1-x) CO2 + x CO + 0.33 H2O + (0.010+y) NO + 0.003 SO2 + (4.261-y) N2 + PM

completecombustion

+ mercury

Total = 3500 deaths/year (1200-6200 – 95% confidence)

If we were to use the numbers from that study, along with western air pollution values …

(310)

(1560)

(110)

(450)(860)

(100)

(200)

(50)

You tell me – how efficient can you make a heat exchanger?

How do you get this efficiency?

Heat Heat

You tell me – how efficient can you make a turbine?

How do you get this efficiency?

Internal Kinetic

Design

Turbine picture

!91 MW from coal-fired steam

Valmont Power Station

Boiler operates at 21 MPa and 534 °C

The condenser is at