F&ES 86025 Energy Systems Analysis

86025 Energy Systems Analysis Arnulf Grubler

F&ES 86025Energy Systems Analysis

86025_1

Introduction to Energy Systems


Energy Systems

Interaction between:-- Society-- Economy-- Technology-- Policythat shape both-- Demand-- Supplyin terms of quantity, quality, costs, impacts.


Definitions & IS Units• Energy: Capacity to do work• Power: Rate of energy transfer

• Newton (N): 1 kg m/s (force)• Joule (J): 1 N applied over 1 m (energy)• Watt (W): 1 J/second (power)

• Example: 1 HP = 745 W (745 J/s) for 1 hr = 0.745 kWh

Energy = Power x Time Hence importance of load factors and load curves!

Examples of Power and Energy (both kill!)

Mercedes SLK 350Power: 200,000 W (200 kW, 3.5L 6-cycl)= 200,000 W/s = 0.2 MJ/s

Energy:max: 720 MJ/hr0.2 MJ/s (x 3600 s/hr)actual:Fuel use: 10 l/100km= 10 x 32 MJ/l = 320 MJ/hr(assuming 100 km/hr)

Lightning boltPower:10,000,000 kW(1 109 Volt x 1 104 Ampere)for 1 second = 10,000 MJ/s

Energy:max. equiv.: 2.8 MJ/hr

Fazit: Even if storable/useablea lightning bolt’s energycould fuel a SLK for less than 1 km!

Power Examples

Human heart ~1 W

Light bulb 100 W

Horse 1000 W = 1 kW (kilo Watt)

Car 100,000 W = 100 kW

Yale PPL 20,000,000 W = 20 MW (Mega Watt)

Boeing 747at max thrust

250,000,000 W 250 MW =

.25 GW

Niagara Falls 2,000,000,000 W 2 GW (Giga Watt)

All US PPL 885,000,000,000 W 885 GW

All World PPL 3,500,000,000,000 W 3500 GW

All US Automobiles 230 million with ~ 100 kW each

23,000 GW

Source: updated and modified after Tester et al., 2005.


Energy Units and Scales(Source: IPCC Energy Primer)

zettajoule (ZJ)

Quick recap: exponentials to common basis are additive!103 x 106 = 10(3+6) = 109 or 1000 MJ = 1 GJ


Energy Orders of Magnitude (EJ = 1018 J)

5,500,000 EJ Annual solar influx 1,000,000 EJ Fossil occurrences 50,000 EJ Fossil reserves 440 EJ World energy use 2000

100 EJ USA primary energy supply 50 EJ OECD transport energy use

20 EJ Saudi Arabia oil prod. 4 EJ Italy oil reserves 1 EJ NY city or Singapore

energy use

Stocks; flows (yr-1)


Rough Equivalences

10 Gtoe = 420 EJ 1 Gtoe = 42 EJ 1 Quad = 1 EJ 1 Mtoe = 42 PJ 1 toe = 42 GJ 1 boe = 6 GJ 1 m3 gas = 40 MJ 1 kWh = 4 MJ 1 Btu = 1 kJ


Converting Units

conv_fac.xls

v2 class server“Resources/data”


Energy Flow Characteristics

• Physical: chemical, kinetic, electric, radiant,…

• Processing depth: primary→secondary→final

• Transaction levels: producer→producerproducer→consumerconsumer→consumer (future?)

• System boundaries:secondary→final→useful→service

Energy Conversions & Efficienciesconversion 1st Law efficiency

Electric generator m → e ~99%

Gas furnace c → t 90-95%

Small electric drive e → m 60-65%

Steam turbine t → m 40-45%

Best PV cells r → e 20-30%

Trad. Cook stove c → t 10-15%

Beef production c → c 5-10%

Fluorescent light e → r ~10%

Incandescent light e → r 2-5%

Paraffin candle c → r 1-2%

Global photosynthesis

r → c 0.3%

Adapted from Smil, 1998.c = chemical, e = electrical, m = mechanical, r = radiant, t = thermal

Efficiency depends on form adequacy, technology, scale,…!!


Conversions are far from trivial: Example of combustion (c → t)

• Fuel + oxidizer = Products ± energy• In ideal conditions: energy is the net sum of

creation/destruction of chemical bonds-- exothermic: producing energy(e.g. CH4 as fuel)-- endothermic: needing energy(e.g. CH4 as chemical feedstock)

• But combustion is generally far away from ideal leading to accounting complexities (HHV, LHV) and most important of all: emissions beyond ideal combustion conditions


Example of Methane(ideal combustion)

• CH4 + O2 → CO2 + H2O (general reaction EQ)

• Balancing for C, H, and O:1 C + 1 O2 → 1 CO2

4 H + 1 O2 → 2 H2Ono oxygen in this fuel (but e.g. in wood!)

• Therefore: CH4 + 2O2 → CO2 + 2H2O

• Net energy: - 2628 kJ from bonds broken+3438 kJ from bonds created+ 810 kJ net energy

Moving beyond ideal combustion:Example of CH4 Cont’d

• Ideal combustion:810 kJ/mole = Lower Heating Value

• Incl. energy from condensation of water vapor:890 kJ/mole = Higher Heating Value

• Emissions:CO2 only in ideal case1 mole* CO2 = 12gC = (12+[2x16]) = 44 gCO2

• Emission factors:12gC/890 kJ = 0.0135 gC/kJ = 13.5 gC/MJ HHV12gC/810 kJ = 0.0150 gC/kJ = 15.0 kgC/GJ LHV

Σ : Fuel-specific energy conversion and emission factors that don’t specify basis (LHV or HHV) are useless!!*mole: mass in g equals molecular weight a mole contains 6.023 1023 molecules (Avogadro’s number)


The Real World

• Emissions under real conditions:-- combustion in air and not pure oxygen →N emissions (air: 21% O, 78% N, 1% other)-- fuel impurities (S, N, ash, heavy metals..) -- incomplete combustion (e.g. hydrocarbons, CO, soot, etc…)

• Important tradeoffs: higher efficiency → higher combustion temperature (cf. second law of thermodynamics) → higher N emissions

• Scale dependency (emissions, and control possibilities): preference for large, centralized combustion

Characteristics of Some FuelsSource: D. Castorph et al., 1999, GRI, 2005.

C%

H%

S%

O%

N%

Ash%

H2O%

LHVkJ/g

HHVkJ/g

HHV/LHV

Wood 50 6 0 44 0 <.5 10-20

14.6-16.8

15.9-18.0

1.07-

1.09

Coal(hard coal)

88 5 1 4.5 1.5 3-12 0-10 27.3-24.1

29.3-35.2

1.05-1.07

Diesel 86 13 .3 - - - - 43.0 45.9 1.07

Natural Gas*(Range)

CH4

74-98

CHs

0-20

H2S

0-5

CO2,O2

0-8

N2

0-5

- -

38-48 42-56 1.10-

1.17

H2* 100 - - 120 142 1.18

* Note difference to LHV on volume basis: gas: 40 MJ/m3 H2: 10.8 MJ/m3


More info:

v2 class server: Resources/data/doe_fueltable.pdf (useful even if non-metric)

NREL (liquids): http://www.nrel.gov/vehiclesandfuels/apbf/progs/search1.cgi

Engineering Toolbox (tons of info), e.g.:http://www.engineeringtoolbox.com/combustion-boiler-fuels-t_9.html


Non-physical Definition of Energy

• System boundaries, processing depth, upstream/downstream: primary→secondary→final → →useful→service

• Transaction levels/actors involved: producer→producerproducer→consumerconsumer→consumer (future?)


What means….

• Primary energy: Resources as extracted from nature (crude oil, solar heat)

• Secondary energy: Processed/converted energy (gasoline from crude oil, electricity from coal or hydropower)

• Final energy (as delivered to consumer)• Useful energy (converted by final appliances

(heat from radiator, light from bulb)• Services = actual demand: comfort,

illumination, mobility,… (units ephemeral!)


System Boundaries

• Energy sector: Primary→ Final (domain of supply bias)

• Energy end-use: Final→Useful (domain of consumer bias)

• Energy Integration (IRM, LC): Primary→Useful/Services

• Full Integration (IA): Whole environment (incl. “externalities”)


14.3 50.3 20.5 20.4 18.82.0Conversion loss 74.7

Crude oil133.2

Coal91.1

Natural gas70.6

Hydro-power

20.5

Nuclear-power

18.8Renewables**

46.6

ALS*9.3

ALS*4.7

Transportation Industry Residential & commercial

** I

nclu

des

trad

ition

al f

uels

TPC: 380.8

TFC: 270.0

ALS*8.0

Feedstocks

15.4

Internationalbunkers

5.0

Useful energy:137.5

*ALS = Autoconsumption, losses, stock changes

TPC: 380.8

7.6Trans-missionloss

TFC: 270.0

84.9

29.9Loss

60.0

108.9

Loss

60.9

42.6Loss

55.018.3

Central electricity & heat generation

48.9

ALS*1.3

ALS*0.1

14.10.1 1.2

Conversionlosses

ALS: 110.851.5

Oil:Coal:Gas:

Renewables:Hydro:

Nuclear:

133.291.170.520.518.846.6

106.044.540.836.134.87.8

Oil:Renewables:

Gas:Coal:

Electricity:Heat:

59.1 0.30.8 0.8 1.6 25.5 21.6 20.1 2.6 9.8 17.7 21.8 41.917.8

Global Energy Flows (EJ in 1990)Source: modified after Nakicenovic/Gilli/Kurz, 1996. Update: IEA, 2006.

In 2005:(#’s rounded)

Primary:500 EJ

Final:320 EJ

Useful:160 EJ

losses:-180 EJ

losses:- 160 EJ

2005: Total losses: 340 EJ for 160 EJ useful energy delivered

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F&ES 86025 Energy Systems Analysis

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