Limits of sustainable energy availability
Wim J. van der Zande
Eindhoven
October
2011
Preambule
- Climate and energy challenges are enormous!
- Students now will (have to) be problem solvers soon!
- I would like to introduce concepts and numbers and would
like to formulate questions, that should have objective
answers!
- Complexity: The step from physics (providing answers on
simple aspects) to decision (also based on experience/
intuition and the necessity of being convincing politically)
is large
Contents
- Climate and energy: accidentally or logically connected
- The greenhouse effect: a model to remove all doubts?
- From solar radiation to solar- and wind energy: limits
- If insights imply a required growth of 10.000% within 50
years: How to create a new ‘Manhattan’ project?
Climate and/or energy?
- Climate and energy: accidentally or logically connected
What if we had at this stage of technological complexity only
108 Earth inhabitants and were running out of C-fuels?
Remark:
(a) Exponential growth always cause catastrophes (Malthus)
(b) Chemical energy in the form of coal/oil is sufficiently
present to tip the climate in an irresponsible way!
Climate and/or energy?
Our atmosphere is frail:
(a) Effective thickness only 8 km on an
Earth diameter of 12000 km.
(b) Its mass is 5 1018 kg
(c) The mass of CO2 2.9 1015 kg, added
CO2 mass since industrial revolution 8
1014kg, at present yearly addition 2.3 1013
kg.
The energy issue
The energy issue: intrinsically complex!
Natural limitations
(conservation laws, physics principles, primary
availability)
Technical limitations
(implementation issues, energy costs, time constraints)
Political limitations
(simultaneously serving calls for increasing wealth, reelection (popularity) issues, safety and access to energy)
Societal acceptance
(transitions without wealth sacrifices, public (dis)trust,
nimby)
The energy issue
- The energy issue: intrinsic complex because of the
playing field
Subsidies, it’s a
public interest
Economic
growth is the
key
(economist)
Doe es normaal,
(politician)
(industrialist)
Problem?, Only 6%
of the North sea for
turbines
(lobbyist)
Don’ts . . .
The energy issue
‘Only’ 6% of the North Sea with
Turbines enough electricity for
all Northsea countries
Don’ts . . .
The energy issue
6% North Sea =
100% of the Netherlands,
750.000 km2
versus 41500 km2
Simple? A densely packed
collection of windmills
over the full surface area
of the Netherlands?
‘Only’ 6% of the North Sea with
Turbines enough electricity for
all Northsea countries
Greenhouse effect
- The greenhouse effect: a model without doubts?
The standard picture
Green house effect
- Doubling CO2 has a negligible effect?
Site: Kees le Pair, broeikasgezeur
Green house effect
- Doubling CO2has a negligible effect?
Correct for the
situation of
radiation with
E>>kT
Site: Kees le Pair, broeikasgezeur
Greenhouse effect
The energy issue
High “Temperature” radiation (for example visible)
I0
Absorption
I=I0 e-σnl=I0 e-χ
σ (cm2), n (cm-3), L (cm)
Low Temperature radiation (with respect to kT)
Spontaneous
emission
Absorption +
Stimulated
emission
I0
Thermal (T)
σ(cm2), n (cm-3), L (cm);
σn ~ emission (Einstein)
I=I0 (1-a/L)
Greenhouse effect
The energy issue
Boundary: up (IR), T= Te (255 K)
A continuum
model: IR only
dχ = n σ dz:
optical thickness
change
Boundary:
T=T0
Greenhouse effect
The energy issue
Boundary: up (IR), T= Te (255 K)
A continuum
model: IR only
dχ = n σ dz:
optical thickness
change
Boundary:
T=T0
(I) One dimensional: in the other directions as much light comes in as goes out . .
(II) BB effect: layer radiates as it is in local thermal equilibrium: B~ σBT4 (function of T)
up and down
(III) BB effect scales with density and cross section. No molecules no BB emission, He
gas no BB radiation
Greenhouse effect
The energy issue
Boundary: up (IR), T= Te (255 K)
A continuum
model: IR only
dχ = n σ dz:
optical thickness
change
Boundary:
T=T0
STEP 1: dIup= dIdown
stable
steady state, the temperature distribution T(z) is
Greenhouse effect
The energy issue
Boundary: up (IR), T= Te (255 K),
χ=0
A continuum
model: IR only
dχ = n σ dz:
optical thickness
change
Boundary: T=T0 , χ =
total column CO2
STEP 2: Solve
With dIup=dIdown
Greenhouse effect
The energy issue
This yields:
(note χ = χ(z))
With:
We find:
NO SATURATION
Greenhouse effect
Notes:
- at higher CO2 the effect of an addition is less
- no saturation effect
- the thermal radiation is the driving force in
establishing the T gradient in the atmosphere
- CO2 is better mixed than H2O therefore CO2 is
relatively more effective (380 ppm CO2, 1-2% H2O)
Solar energy and
limits
Solar radiation solar- and wind energy
(reference world energy use: 5 1020 J/year)
- Solar energy input:
1.7 1017 Watt (100%) 5.5 1024 J/year (1.5 1018 kWh/year)
- Correction for albedo and absorption in upper atmosphere:
0.9 1017 Watt
2.8 1024 J/year (0.8 1018 kWh/year)
The differentiation with latitude:
- Variation over latitude (input): 1374 cos(θ) W/m2
Useful for the Netherlands about 350 W/m2,
With as daily average 120 W/m2
(Tidal energy=extra gravitational energy 6 mW/m2 world average)
Physical limits
(reference world energy use: 5 1020 J/year)
Energy in the Earth Rotation:
3 1029 J (2 105 years of solar radiation)
Change, decrease due to tidal working
22 µs/year, or 2.4 1010 J/year
Physical limits
The unequal radiation pattern over Earth “should”
generate an enormous T gradient
(20 degrees more than now).
- the Inter tropical Convergence Zone motors the heat
transport and the possibility of performing work (wind
energy)
- Heat transport (equatorian-poles):
about 20 W/m2
- Efficiency of work (wind energy):
∆T = 30 K, T= 300 K εmax 10%
2 W/m2 (horizontal)
- Yearly total kinetic energy (wind) :
6 1020 Joule/year (2 10-3 solar influx)
Reference: world use: 5.1020 Joule
(thanks: Peter Siegmund)
Solar energy and limits
- From solar radiation to solar- and wind energy: limits
Technological realizations:
- wind energy
Output about 1.2 W/m2 (averaged over a park, suitable place with high
boundary layer wind; near maximum) (see also Jo Hermans, David
McKay)
Solar energy and limits
- From solar radiation to solar- and wind energy: limits
Technological realizations:
- solar energy (I): Photovoltaics
Output: (year average, Nl: 12 W/m2 with 10% efficiency (no
transport/storage!)
Note: Physics efficiency-range: 8-40 %
Part of solar spectrum, finite absorption, recombination losses.
Peaks near 30 % (GaAs technology, concentrators, multi layers)
Routine: 8-12 % efficiency
Solar energy and limits
- From solar radiation to solar- and wind energy: limits
Technological realizations:
- solar energy (II): Concentrated solar power
Output: (no examples in Nl, In deserts, spain, US:
15-30 W/m2 (because of deserts)
Note: Physics efficiency-range: heat tot electricity (30-50%)
Full solar spectrum, low tech concentrators,
But direct solar radiation (60%)
High T in heated oil hence high Carnot efficiency
The human demand
The energy issue
A step back: the human demand now
Total energy use
6.1020 J/year, 2 1013Watt, 1.7 1014 kWh/year energy
Electricity:
6.1019 J/year, 2.1012 Watt, 1.7 1013 kWh (making electricity
is a 30% efficient process)
The David MacKay Unit: kWh/day/person: 65
The human demand
The energy issue
A step back: the human demand now
The home need (Netherlands):
4.1018 J/year, 1.1 1012kWh/year, 7 kWatt/person continuous
energy need!
Electricity:
5.1017 J/year, 1.3 1011 kWh/year, 800 Watt/person
The David MacKay Unit: kWh/day/person: 160
Wind turbines
The energy issue
The largest (Emden):
7 Mwatt == 2 Mwatt (reality)
0.0005 kWh/person/day=0.5 Wh/p/d
Windpark Egmond
Solar concentrators
The energy issue
Solar concentrators
The energy issue
• Gemasolar (20 MWatt
peak, 110 GWh/year (about
60%)
• Space 185 hectares:
• 6.7 W/m2 24h
The human factors
The energy issue
Distribution over energy sources: now
Wikipedia
Wind: 0.3%
x100
30%
Solar concent: 0.5% x60
30%
Photovolt: 0.04% x700
30%
Biomass: 4% (also primitive cooking)
The human factors
The energy issue
Distribution over energy use: 2009 US
Energy Costs
TURBINE 0.25 MW
Steel
1.05 105 kg
1.6 106 kWH
Copper
2.7 103 kg
6.7 104 kWh
Fibre/com- 9.6 103 kg
posite/rotor
2.7 105 kWh
Concrete
1 105 kg
5.6 105 kWh
2 106 kWh
40 GJ/ton 4 107J/kg
or 11 kWh/kg, including
ore: 15 kWh/kg
Energy Costs
TURBINE 0.25 MW
Steel
1.05 105 kg
1.6 106 kWH
Copper
2.7 103 kg
6.7 104 kWh
Fibre/com- 9.6 103 kg
posite/rotor
2.7 105 kWh
Concrete
1 105 kg
5.6 105 kWh
2 106 kWh
Doubling time: 3.5
year
0.25 MW turbine produces
about 106 kWh/year:
Pay back time: 2 year.
Conclusion: half of energy goes
macro-economocally into realising
new windmills until saturation sets in.
Questions and . .
The energy issue
We need education in terms of comparable objective
numbers and not of slogans.
We need an increase in efforts which is enormous. Are
‘adiabatic’ scenarios sufficient? Is a Manhattan project
called for?
The question whether to try it all or whether to wait until
maturity and clarity is reached could not be afforded in
1941, and also not in 2011!
Start with a book like Jo Hermans’ energy survival guide or
David McKay sustainable energy without the hot air and
pose and sort out questions from the many numbers . . .
Conclusion. .
The energy issue
Thank you for your
attention
Steel energy costs
The energy issue
Steel energy costs
The energy issue
Steel energy costs
The energy issue