Environmental Energy Technology(NOTE 6-7)

Joonhong ParkYonsei CEE Department

2014. 10. 13.

Unsustainable Energy Technologies: Coal, Oil, Gas and

Non-Conventional Hydrocarbons

Nuclear Power

Physical basis

• 235 U + n => 92 Kr + 141 Ba + 3n + gamma ray

• Mass reduction (△m): 3.57 X 10-28

• E = mc2 = △m * (3 x 108)2 = 3.2X10-11 J per fission.

• The fission of 1 kg of 235U releases 8.2 X 1013 J per kg (cf. Chemical energy from 1 kg Oil = 35 MJ)

• WOW!

Technologies for Use

There is only one commercial use for nuclear fission: the generation of electricity for supply to consumers via a national grid.

- Connected to steam engine (again?!)

-Nuclear fission is used simply as a heat source.

-Requires a coolant.

- Differences lie primary in the design of the core of the reactor and the fluid used to remove heat from it.

Basic Reactor Design

-The need for a reactor to absorb excess neutrons.

-Requires the initializing neutrons to be moving relatively slowly (thermal neutrons)

-A moderator: water or graphite

-Uranium oxide (U3O8) consists of only 0.7 % 235U. (mainly in a form of 238U).

- 238U + n => 239U

239U => 239Np + e (beta-decay)

239Np=>239Pu + 3 (beta-decay)

Reactor Physics

-Multiplication factor (k): the number of additional neutrons going on to produce fission from each fission event (k =1 under steady state power generation)

A variety of thermal reactors

Type ThermalPower (MW)

Coolant

Moderator

CoreVolume(m3)

Vol. PD (MW/m3)

FuelRating(MW/tonne)

ExitCoolant Temp (oC)

Magnox

225-1875

CO2 Graphite 449-2166

0.5-0.87

2.2-3.15

400

AGR 1500 CO2 Graphite 550 2.5 11.2 650

CANDU 3425 D2O D2O 280 12.2 26.4 293

PWR 3800 H2O H2O 40 95 38.8 332

BWR 3800 H2O H2O 75 51 24.6 290

RBMK 3140 H2O Graphite 765 4.1 15.4 -

Fast Breeder

1000 Liquid Na

None 1.5 400 150 -

Environmental Concerns

Waste materials from the mining of the uranium ore:

-Radioactive radon gas

-Radioactive materials from the enrichment process

-Ratocative gases (krypton and xenon)

-Radioactive tritium (3H).

-Low-level and high-level wastes

Two greatest concerns

-A large scale accident (mostly due to poor operation and human errors)

-What to do with the spent fuel rods.

Options for high-level waste storage

Enrichment

Fuelfabricatio

n

Reactor

PU Store Reprocessin

g

InterimLiquid

storage

Solidification

Spent fuelstorage

Natural U

Fast ReactorEngineered

Surface Storage

Ultimate Disposal

(Sea Bed)

Pu

U

World Resource

Estimated known uranium reserves: 3.12 Mt (1400 EJ), 70 yr

Economical feasible to extract U from diluted source: 28 Mt

Ocean: 3 ppb

Fast reactor: using 238U rather than 235U.

Discussion

Is nuclear power the solution to global warming?

Hydropower

Technologies for Use

Low head

Medium head

High head

Technologies for Use

The Francis turbine (reaction turbine): suitable for medium heads

Propeller (reaction turbine): suitable for low heads

The Pelton wheel (impulse turbine): suitable for very high heads (>250 m)

Efficiency: 70%

Environmental impacts

The need to resettle large number of people

The low of important archaeological remains

Loss of habitats

Loss of rare species

Major impacts on river wildlife and humans on the downstream side of the dam

Methane production from rotting vegetation in the flooded area

Loss of human life from dam failures

Amplification of interstate tensions from diverting water resources

Pumped Storage

A method to storage a large amount of electrical energy

More dams?

Discussion

In Korea, most of annual rain precipitation occurs during the Monson period (July-August).

How to maximize the hydro-resource for electricity generation? How to store them in our land?

Introduction to Sustainable Energy Technologies

Energy Conversion Efficiencies

ChemicalEnergy(fossil fuels etc.)

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

70-95 %

20-40 %100 %

85-95 %

90-95 %

Cogeneration/CHP

ChemicalEnergy(fossil fuels etc.)

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

70-95 %

20-40 %100 %

85-95 %

90-95 %

Recovery of WasteHeat (CombinedHeat and Power)

Solar Power

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

20-40 %100 %

85-95 %

90-95 %

Recovery of WasteHeat (CombinedHeat and Power)

Solar Power

Solar Power Systems

• Low temperature• High temperature - Dish collectors - Stirling engines - Power towers - Trough collectors

Operational principle of an ocean thermal energy

converter (pilot scale)

Pump

CondenserEvaporator

Turbine

Electric power generator

AmmoniaLiquid

AmmoniaVapor

ColdWater(5oC)

WarmWater(25oC)

Photovoltaics

Sunlight

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

100 %85-95 %

90-95 %

Photovoltaics90-95 %

Turning sunlight intoElectricity with high efficiencyat low cost using common materials.

(n-p junction in a solar cell)

Wind power

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

100 %

85-95 %

90-95 %

Wind power

Horizontal axis wind turbine: rotor diameter, machine rating, rotational speed & number of blades, the generator

Environmental impacts: electromagnetic interference, ecological impact, noise

Wave power

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

100 %

85-95 %

90-95 %

Wave power

Global energy densities: New Zealand (100), South Africa (70), North east France (70), Korea-Japan ( 15)

Power is a function of wave height (h)

Onshore devices, Offshore devices (Salter Duck, Pelamis)

Tidal and small-scale hydropower

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

100 %

85-95 %

90-95 %

Tidal and small-scalehydropower

Tidal stream

Small-scale hydropower

Biomass

ChemicalEnergy

(Biomass)

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

70-95 %

20-40 %100 %

85-95 %

90-95 %

Recovery of WasteHeat (CombinedHeat and Power)

CO2

Oxidation

C-fixation

Geothermal

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

20-40 %100 %

85-95 %

90-95 %

Recovery of WasteHeat (CombinedHeat and Power)

Geothermal

Environmental impact?

Fast Breeder & Fusion

NuclearEnergy

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

70-95 %

20-40 %100 %

85-95 %

90-95 %

Recovery of WasteHeat (CombinedHeat and Power)

Fast Breeder

Fusion

Fast Breeder (Fission)

100 fissions

292 neutrons produced

39lost

32 by Pu

121 by 238U

84 in Pu13 in 238 U3 in 235 U

A variety of thermal reactors

Type ThermalPower (MW)

Coolant

Moderator

CoreVolume(m3)

Vol. PD (MW/m3)

FuelRating(MW/tonne)

ExitCoolant Temp (oC)

Magnox

225-1875

CO2 Graphite 449-2166

0.5-0.87

2.2-3.15

400

AGR 1500 CO2 Graphite 550 2.5 11.2 650

CANDU 3425 D2O D2O 280 12.2 26.4 293

PWR 3800 H2O H2O 40 95 38.8 332

BWR 3800 H2O H2O 75 51 24.6 290

RBMK 3140 H2O Graphite 765 4.1 15.4 -

Fast Breeder

1000 Liquid Na

None 1.5 400 150 -

Fusion

NuclearEnergy

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

70-95 %

20-40 %100 %

85-95 %

90-95 %

Recovery of WasteHeat (CombinedHeat and Power)

Fusion

Potential uses of Fusion technology

SOLAR

NUCLEAR

Fast Fission

Thermal Fission

Fusion

Geothermal (radioactivit

y)

Heat

THERMAL Electricity

ELECTRICAL

Biomass

FossilFuels

Hydrogen Batteries

CHEMICAL

Wind

Wave

Mechanical

Hydro TidalGeothermal

(original accretion)

GRAVITATIONAL

KINETIC

Fuel Cells

ChemicalEnergy

Thermal

Energy(heat)

Electricalenergy

Mechanical energy

100 %85-95 %

90-95 %

Fuel Cells

90-95 %

The current uses of unsustainable energy technologies. How about the potential uses of sustainable energy

technologies?