Today, let’s dig the «technico-scientiﬁc» soil · 2016-06-11 · 1860 Lenoir’s engine 1876...

Technico-scientifique

Economico-politique

Ethico-anthropologique

Ontologie/métaphysique

Théologique

source: Ch. Luyckx

Today, let’s dig the «technico-scientific» soil

mardi 24 février 2015

Selandia (1912)

Not suprisingly, efficiency was already a must one century ago and long before that


Jobs for the engineers: efficiency and «green» energy

Kaya’s identity

Reduce CO2 emissions using renewable energy

Reduce energy intensity


Efficiency of (energy) conversion

Definition of efficiency

Is ‘always more with less’ realistic?

What are the limits?

Cost of doing the same with less

Access to energy

The difficult concept of exergy

There is (not so) plenty of renewable exergy

EROEI, a central issue

Having plenty of renewable energy, a benefit?


The fuel consumption of an airplane is a function of its drag (aerodynamics) of its mass (materials) and of its propulsion system

(fuel conversion)

L

D T

Mgsource: flightglobal.com

To define efficiency, let’s look at a flying airplane


R = ηglob.

�L

D

�PCI

gln

�Mi

Mf

�

Improving all technologies helps improving the fuel consumption and thus the range of an airplane

Improve propulsion Improve materials

Improve aerodynamics

Breguet’s range equation

Improving is similar to being more efficient


Chemical energy

Mechanical work

Heat Thrust

ηc ηth ηp

ηc =Heat produced

Fuel consumption

\eta_c =\frac{\textnormal{Heat produced}}{\textnormal{Fuel consumption}}

ηth =Mechanical work

Heat produced

ηp =Thrust

Mechanical work

Focusing on the propulsion system, efficiency is what you get from what you paid for

ηe = ηc × ηth × ηp







Access to energy






Chemical energy

Mechanical work

Heat Thrust

ηc ηth ηp

ηth

ηpKoff, 1991

What are the trends in overall efficiency? Getting closer to 0.4 only. So it seems there is room for

improvement.


UDF (unducted fan) GTF (geared turbofan)

Advanced propulsion systems : a technology marvel leading to an overall efficiency of 0.5 only. Why?


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6 7 8 9

5

T2T1

!

Moteur Diesel routier

Moteur Essence

Moteur Diesel marin

Turbine à gaz (grande puissance)

Turbine à gaz (petite puissance)

1200 900 600 300 1500 T2 =

Thanks to the second principle of thermodynamics (i.e. physical limits), conversion of thermal energy into work is

limited

Amplitude of driving forces

Increasing constraints

Reducing irreversibili

ties


Both technology level and size matter

1860 Lenoir’s engine 1876 Otto’s engine1896 Diesel’s engine1912 Selandia’s engine

1986 Marine Diesel engine

2011 Gas engine 2011 Vehicle Diesel engine2011 Vehicle gasoline engine2011 Marine Diesel engine

5%20%25%30%

48%

45%42%35%54.4%

Engine Efficiency


MAN S80ME-C7

Both technology level and size matter


Yes, size does really matter : example of ship transportation

Source: HKND, Drewry


Thanks to Betz (i.e. physical limits), wind turbine efficiencies are also limited. The standard technology is already close to

the limit

Source: Wind turbine by Hau and von Renouard, Springer


This is true for a majority of processes (example of cement production) where expected gains are limited.


There are some exceptions like heating needs in buildings that could go down to zero







Access to energy






It is also usually possible to obtain the same service for less. It is another form of efficiency.

Porsche 911mass = 1600 kg

21 kW @ 120 km/h

260 kW @ 300 km/h (max speed)

Combined fuel economy = 12.3 l/100kmmardi 24 février 2015

Renault Cliomass = 1100 kg

P=20 kW @ 120 km/h

50 kW @ 167 km/h (max speed)

Small cars have a better fuel economy using less mass and a lower max speed

Combined fuel economygasoline : 4.3...5.5 l/100km diesel : 3.2...3.4 l/100km


We can go even further by still reducing the mass and improving the shape. However, the service is not exactly the same.

VW xl1mass = 795 kg !

9 kW @ 120 km/h21 kW @ 167 km/h

Combined fuel economy1l/100km (NEDC standards)2l/100km in practice


Down to this highly efficient transportation system. Is it still really a car? Does it impact our economy?

Peraves Monotracermass = 250 kg

5 kW @ 120 km/h

67 kW @ 300 km/h

Combined fuel economy <1l/100km







Access to energy






Energy is never lost. It is thus better to use the quality of energy, i.e. the exergy.

Chemical energy

Mechanical work

Heat Thrust

ηc ηth ηp

Unburns Cold source Kinetic losses

W =

�1− Tatm

T

�Q

Max theoretical conversion into work Heat source

Exergy contentmardi 24 février 2015

Electricity Heat

exergy = 1

energy = 1

exergy = 0.1

energy = 1

Energy conversion is subject to strong exergy losses

Source: Thomasnet.com


Examples of exergy content of energy

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Source: ENEA Consulting


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Source: ENEA Consulting

We get more insight following the decreasing exergy content through the different conversion

steps than following the conserved energy







Access to energy






7 Source: Hermann (2006)

Flux et stocks d‘exergie Exergy flux, accumulation, destruction, and useExergy flux, accumulation, destruction, and use

W. Hermann. Quantifying Global Exergy Resources. Energy 2006;31(12):1349-1366.Source: Hermann (2006)

This is true for renewable energy


8

Flux et stocks d‘exergie : le soleil et les autres sources Exergy flux, accumulation, destruction, and useExergy flux, accumulation, destruction, and use

W. Hermann. Quantifying Global Exergy Resources. Energy 2006;31(12):1349-1366.Source: Hermann (2006) Source: Hermann (2006)

The main source of renewable energy is the sun. Conversions to wind, biomass, etc. suffer from

large exergy losses.

There is plenty of renewable energy but renewable exergy is much more scarce


9

Flux et stocks d‘exergie : le vent

870 TW

300 GW 60 TW

3 TW

0 TW

Vagues

Vagues proche des côtes

Potentiel exploité

Energie cinétique de l’air

Eolien

31000 TW

Example of wind energy


Flux et stocks d‘exergie : le cycle de l’eau

18 Tg/s

3.9 Tg/s

2.0 Tg/s 1.9 Tg/s

0.4 Tg/s 1.5 Tg/s

1.1 Tg/s

300 TW 90 TW

25 TW 19 TW

7.2 TW 5.4 TW

précipitations

sur terre

évaporation

vers océans via cours d’eau

1000 GW

gravité chimique

Example of hydraulic energy


18

Flux et stocks d‘exergie : la biomasse

90 TW

65 TW 25 TW

16 TW

5 TW

1.5 TW

0.2 TW

0.02 TW

biomasse

terre océan

exploité

Exploité pour le bois de chauffe

Bois de chauffe ethanol

Example of biomass







Access to energy






L’EROI (Energy Return On Investment) est très élevé comparé aux autres technologies

EROI = énergie électrique produite / énergie primaire consommée

Source: Kubiszewski et al., Ren. En., 2010




EROEI Energy Return On Energy Invested

To get energy we must invest energy


In Meadows’ work, EROEI is killing us

Source: Limits to growth - The 30 year update


By the way, having plenty of cheap resources is not sufficient to save us

Source: Limits to growth - The 30 year update


Source: Hall & Day, American Scientist, May 2009

Other examples of EROEI


Il est préférable énergétiquement d’installer de grandes éoliennes





But again size does matter


RE development

RE extension

RE extension

EROEI

η

EROEI and renewable energy development







Access to energy






Consommation électrique en Belgique : 82700 GWh (2008)!

Pour satisfaire cette consommation il faudrait environ 11000 éoliennes de 3 MW (facteur de charge 0.3). !Actuellement, l’équivalent de 300 d’entre-elles est installé. !

Pour satisfaire cette consommation il faudrait exploiter plus de 41000 km2 de biomasse (10t/ha/an, rendement des centrales 0.4). !

Pour satisfaire cette consommation il faudrait installer 827 km2 de panneaux photovoltaïques (100kWh/m2/an). En 2012, 15 km2 étaient installés. !

et si tout devenait électrique nous devrions construire 8 fois plus de tout !

Extensive use of renewable energy?


Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.

28 — Putting costs in perspective 215

Figure 28.2. A plan that adds up, forScotland, England, and Wales.The grey-green squares are windfarms. Each is 100 km2 in size and isshown to scale.The red lines in the sea are wavefarms, shown to scale.Light-blue lightning-shapedpolygons: solar photovoltaic farms –20 km2 each, shown to scale.Blue sharp-cornered polygons in thesea: tide farms.Blue blobs in the sea (Blackpool andthe Wash): tidal lagoons.Light-green land areas: woods andshort-rotation coppices (to scale).Yellow-green areas: biofuel (to scale).Small blue triangles: wasteincineration plants (not to scale).Big brown diamonds: clean coalpower stations, with cofiring ofbiomass, and carbon capture andstorage (not to scale).Purple dots: nuclear power stations(not to scale) – 3.3GW averageproduction at each of 12 sites.Yellow hexagons across the channel:concentrating solar power facilities inremote deserts (to scale, 335 km2

each). The pink wiggly line in Francerepresents new HVDC lines, 2000 kmlong, conveying 40GW from remotedeserts to the UK.Yellow stars in Scotland: newpumped storage facilities.Red stars: existing pumped storagefacilities.Blue dots: solar panels for hot wateron all roofs.

Renewable energy will affect our environment

source: D. Mc Kay (scenario M, 2050) mardi 24 février 2015

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Alta Wind Energy Center (USA)500 éoliennes

1320 MWmardi 24 février 2015






Access to energy






L’économie néoclassique a besoin de progrès technique pour assurer la croissance

Y = AL1−αKα

Y=Production

Productivité multifactorielle=

Progrès technique

L=Travail

K=Capital

Pourquoi a-t-on besoin de croissance?


L’économie écologique a besoin d’énergie et de progrès technique pour assurer la croissance

Stern 2011

Y =�(1− γ)

�ALL

αK1−α�φ

+ γ (AEE)φ�1/φ

Productivité multifactorielle=

Progrès technique

meilleure technologie et

meilleure qualité de l’énergie

E=Energie


Exemple 4 : Les améliorations restent possibles (cas des automobiles)

l/100km

source: Bureau fédéral du plan


source: Bureau fédéral du plan

millions de km

parcourus

Exemple 4 : Mais les km parcourus augmentent. C’est l’effet rebond !


Source: ICEDD


Today, let’s dig the «technico-scientiﬁc» soil · 2016-06-11 · 1860 Lenoir’s engine 1876...

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