Electrical Energy Systems

(1)

Electrical Energy

Systems

(2)

Electricity

A secondary energy source

•

Electrical energy does not exist in nature



In a useful shape



Secondary energy source

o

Produced from primary sources



Not storable

o

Production = consumption + losses

(3)

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MW – MWh – MW/h

•

MW – MWh – MW/h



MW

o

Capacity

o

Instantaneous power production



MWh

o

Produced energy

o

1 MW produced constantly during 1 hour



MW/h

o

Dynamic ramping rates

(4)

The grid of today

•

Transmission network



To

transport

the electric power

from the point of generation to

the load centers



All above a certain voltage

•

(Subtransmission)

•

Distribution network



To

distribute

the electric power

among the consumers

(5)

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Structure of the power grid

What’s the difference?

•

Transmission system



Higher voltage (typical at least 110 kV and higher)



Power injection by generation and import, large consumers



Interconnected internationally



Meshed nature - Redundancy

•

(Subtransmission system)



Between transmission system and distribution system



Connection of large industrial users and cities



Open loop/partly meshed

•

Distribution system



400 V to some ten of kV



Industry, commercial and residential areas



Radial

(6)

(7)

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(8)

(9)

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(10)

Securing supply of

electrical energy

Security of supply

Short-term

Access to

primary fuels

System

adequacy

Market

adequacy

Long-term

Operational security

Generation adequacy

Network adequacy

Connecting

renewables

Facilitating

market

Security of

supply

(11)

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(12)

Electricity Generation

EU15

Source: IEA

Coal (TWh) Oil (TWh) Gas (TWh) Nuclear (TWh) Renewables (TWh) (*) Other (TWh) (***)

Belgium 2005

(13)

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Power plant technologies

(14)

Nuclear

•

Nuclear reactors



Thermal efficiency of ~33%



Very inflexible

o

Constant operation at rated power output

o

May take up to a couple of weeks to re-start



Lowest (not at all) CO

2

and NO

x

emissions



Relatively cheap electricity



Extremely large stored primary energy



Very small footprint

(15)

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(16)

Coal-lignite

•

Conventional thermal

•

Thermal efficiency of ~33-40%



Prospects 2015: coal gasification CC - up to 55%

•

Limited flexibility



Thermal cycle decisive

•

Fuel needs



1000 MW – 7000 tons coal

A DAY (modern plant)

•

High emissions



1000 MW – 7 mln. Tons CO

2



Candidate for CO

2

capture and storage (sequestration)?

(17)

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(18)

Gas

•

Combined cycle gas turbine

CCGT



Gas and steam turbines



High thermal efficiency ~54%

o

Prospects 2015: advanced CC up to 60%



Low ramping rates

o

Higher flexibility at cost of efficiency

•

Gas turbines

GT



Peak units



Very fast start up



High ramping rates

(19)

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Power plant technologies

(20)

Hydro

•

Uses natural facilities (geographical

possibilities)



Rivers



Lakes



Dams

•

Flexibility

•

Cheap and clean source of energy

(21)

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(22)

Renewables

•

Fuel availability



Not always available

•

No division into base or peak load



Produce if available

•

Technologies



Hydro (of course, 28 % of electricity in the world)



Wind: unpredictable



Biomass: comparable to coal



Geothermal: not everywhere (e.g. in Italy, Iceland)



Solar: still expensive

(23)

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Reality show

How far are we:

2001 EU15

RES share in total consumption:

15,20%

Biogas

Solid biomass

Biowaste

Geothermal electricity

Hydro (large-scale)

Hydro (small-scale)

Photovoltaics

Wind onshore/offshore

(24)

Reality show

DGTREN: Not reaching targets!

•

18% - 19% RES by 2010 instead of 22%

(25)

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Reality show

Demand growth

•

International Energy Agency



Forecasts 1.4% average

demand growth

till 2030

EU15 …underestimated?

•

Despite all demand reducing policies



Energy efficiency: save 1% per year due to better

technologie



demand response, interruptible demand



New applications (heat pumps, PHEV?) and

(26)

Power plant portfolio

EU15

Source:

VGB

(27)

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DG technologies

Introduction

• Limited number of loads

• Energy supplied top-down from

central power station

TRADITIONAL VOLTAGE GRID

• Increased loading

• Increased distortion: due to

non-linear (power electronic) and

sensitive loads power quality

problems arise)

• Local generation

• Local storage

• Controllable loads

• Power quality and reliability is a

big issue

(28)

Gas turbine

Gas engine

DG technologies (1)

Fuel cell

Stirling engine



Use fossil fuels

used as Combined Heat and Power (CHP) system: an efficient and effective way of

converting fuel into electrical and thermal energy (~15% energy saving).

(29)

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DG technologies (2)

Photovoltaic system

Wind turbines

Biomass energy

Wave energy

Tidal energy

Geothermal energy

Small hydro power



Use renewable

energy

(30)

DG technologies

Photovoltaics - Technology

•

Photovoltaic devices

can be made from various types of

semiconductor

materials, deposited or arranged in various

structures, to produce solar cells

(31)

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DG technologies

Biomass - Operation

(32)

DG technologies

Biomass - Concept

•

Biomass

is plant matter such as trees, grasses,

agricultural crops or other biological material. It can

be used as a solid fuel, or converted into liquid or

gaseous forms, for the production of electric power,

heat, chemicals, or fuels.

(33)

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DG technologies

Internal Combustion Engines - Concept

•

The

internal combustion engine

is a

heat engine in which the burning or fuel

occurs in a confined space called a

combustion chamber.

•

This

exothermic

reaction of a fuel with an

oxidizer creates gases of

high

temperature and pressure

, which are

permitted to expand.

•

Useful work is performed by the

expanding hot gases acting directly to

cause movement, for example by acting

on pistons, rotors...

(34)

DG technologies

Internal Combustion Engines - Operation

•

The most common fuels in use today are made up of

hydrocarbons

.

These include

diesel

,

gasoline

and

liquified petroleum gas

. Most internal

combustion engines designed for gasoline can run on

natural gas

or

liquified petroleum gases without modifications. Biofuels, such as

Ethanol

can also be used. Some can run on

Hydrogen

; this can be dangerous (It

burns with a colorless flame)

•

All internal combustion engines must have a means of

ignition

to promote

combustion. Most engines use either an

electrical

or a

compression

heating ignition

system.

•

Once successfully ignited and burnt, the combustion products, hot

gases

,

have more available energy than the original compressed fuel/air mixture.

•

The available energy is manifested as high

temperature

and

pressure

which can be translated into

work

by the engine.

•

Once the available energy has been removed the remaining hot gases

are

vented

(often by opening a

valve

or exposing the exhaust outlet) and

this allows the piston to return to its previous position.

(35)

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DG technologies

Microturbines - Technology

(36)

DG technologies

Fuel cells - Concept

• A

fuel cell

is an

electrochemical

energy conversion device

similar to a

battery

.

• BUT it is designed for continuous

replenishment of the reactants consumed

• It produces electricity from an external

supply of fuel and

oxygen

• Additionally, a fuel cell's electrodes are

catalytic and relatively stable

.

• Typical reactants: H

ydrogen

on the

anode

and oxygen on the

cathode

(a

hydrogen cell)

• Other reactants:

Hydrocarbon

fuels,

including

diesel

,

methanol

(

Direct-methanol fuel cells

) and chemical

hydrides. The waste product with these

types of fuel is

carbon dioxide

.

(37)

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DG technologies

Fuel cells - Technology

(38)

DG technologies

Fuel cells - Technology

• A

proton

-conducting membrane, (the

electrolyte

), separates the

anode and cathode sides.

• On the anode side, hydrogen diffuses to the anode where it

dissociates into protons and electrons.

• The protons are conducted through the membrane to the cathode,

but the electrons are forced to travel in an external circuit (supplying

power) as the membrane is electrically insulating.

• On the cathode, oxygen reacts with the electrons (which have

traveled through the external circuit) and protons to form water.

• In this example, the only waste product is

water vapor

and/or

liquid

water

.

(39)

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DG technologies

Fuel cells - Types

Gas engine

hydrocarbons.

diesel,

gasoline

liquified petroleum gas.

natural gas

Ethanol

on Hydrogen

ignition

combustion. Most engines use either an

electrical

gases

temperature

pressure

o work

vented

valve

battery.

oxygen

including

, methanol

Direct-methanol fuel cells

carbon dioxide.

A proton

electrolyte)

water vapor

water