Energy implications of global climate stabilization

Gregory Benford

Physics, Univ. California, Irvine

(based on the work of many, especially Marty Hoffert NYU)

“High technology paths to global climate stabilization”

(Science Vol 298, 2002)

Martin I. Hoffert, Department of Physics, New York University Ken Caldeira, Energy & Environment, Lawrence Livermore National Laboratory Gregory Benford, Department of Physics, UC-Irvine David R. Criswell, Institute of Space Systems Operations, Univ. of Houston Christopher Green, Department of Economics, McGill University L.D. Danny Harvey, Department of Geography, University of Toronto Howard Herzog, MIT Laboratory for Energy and the Environment John Katzenberger, Aspen Global Change Institute Haroon S. Kheshgi, ExxonMobil Research and Engineering Company Klaus S. Lackner, Columbia University John S. Lewis, Lunar and Planetary Laboratory, University of Arizona H. Douglas Lightfoot, Center for Climate and Global Change, McGill University Wallace Manheimer, Naval Research Laboratory John Mankins, NASA Headquarters Gregg Marland, Oak Ridge National Laboratory, Michael E. Mauel, Dept of Applied Physics & Applied Math, Columbia University L. John Perkins, Lawrence Livermore National Laboratory Tyler Volk, Department of Biology, New York University Tom M.L. Wigley, National Center for Atmospheric Research

Co-authors

Three strategies to climate stabilization

Climatestabilization

Developnon-fossil

energy sources

Sequestercarbon

Diminishend-usedemand

population (N)

energy intensity (E/GDP)

per capita GDP (GDP/N)

carbon intensity (C/E)

CO2 emissions

= N x (GDP/N) x (E/GDP) x (C/E)

= GDP x (E/GDP) x (C/E)

= GDP x (C/GDP)

20001900 210021501950

IPCC IS92a“Business as usual”scenario assumptions

•Human population quadrupled,

* power consumption increased X 16

• Carbon Dioxide ~270 ppm ---> ~ 370 ppm•>>> will pass 550 ppm in 21st Century

• Power demand reached ~ 12 TerraWatt, 85% fossil-fueled

• Business As Usual Assumption:• economic growth ~ 2 - 3 % /yr• sustained decline in (Energy use/ GDP) of 1%/yr

• The means to continue this rate for 100 years without greenhouse emissions do not exist operationally or as pilot plants

IN THE 20TH CENTURY:

Energy intensity decline and carbon-emissions-

free power required to stabilize at 2 x CO2

IPCC IS92a“Business as usual”scenario assumptions

10

0

20

30

40

50

60

Car

bon-

emis

sion

s-fr

ee p

ower

req

uire

d (T

W)

0 1 2Rate of improvement in energy intensity (%/yr)

0.5 1.5 2.5

21002075

2050

2025

2000

We need to push hard on bothimproving energy intensity anddeveloping carbon-emissions-free power sources

Greater than 1%/yr improvementmay be difficult to sustain

Over 100 years, 1% / yr = 2.7 2% / yr = 7.22.5% / yr = 11.8

The transportation sector

Battery-electric21-27% efficiency

Internal combustion18-23% efficiency

IC-Hybrid electric30-35% efficiency

Fuel cell30-37% efficiency

Without structural changes, we can only obtain a factor of 2 improvement in the transportation sector

Steam boiler efficiency is limited by

boiler hoop strength to 40%

Physical considerations limit efficiency increases. Assumptions of continuous exponential improvement are not physically justifiable.

Global Carbon ManagementTechnologies in the Current R&D Pipeline Are Not Enough

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

1990 2010 2030 2050 2070 2090

Gig

aton

s/yr

IS92a(1990 technology)

IS92a

550 Ceiling

Where today’s technologywill take us

Where our current aspirationsfor technology will take us

Where we need to go tostabilize carbon

480 Gigatons

1300 Gigatons

Energy intensity

Preliminary conclusion Without significant structural changes (i.e., changes to the

way we live), it may be difficult to sustain > 1 % per year improvements in energy intensity (See Lightfoot and Green, 2001)

Uncertainty in climate sensitivity introduces a huge uncertainty in allowable

emissions

Because of uncertainty in climatesensitivity, we do not know whichof these emission pathways would lead to a 2°C warming after 2150.

Climate sensitivity is the change inglobal mean temperature from a doubling of atmospheric CO2

We need a major research program directed at reducing uncertainty in climate sensitivity

IPCC IS92a “Business as usual” scenario(assumes 1% / yrimprovements in energyintensity)

Uncertainty in climate sensitivity and carbon-emissions-free power requirements

To stabilize climate,in the long term,most of our power will need to bederived from carbon-emissions-freeenergy sources

Uncertainty in climate sensitivityintroduces a large uncertainty in therate at which carbon-emissions-freepower will need to be deployed

2°C warming with IPCC IS92a “Business as usual” scenario assumptions

Mean rate of capacity addition over next 50 years needed to stabilize climate by

2150

IPCC IS92a“Business as usual”scenario assumptions

Uncertainty in climate sensitivity andwhat constitutes acceptable climatechange both introduce large uncertainties in the rate at which carbon-emissions-free power needsto be deployed

We need a major research program directed at understanding what constitutes “acceptable climate change”

Doing more now means doing less later, and vice versa (multiple pathsto same end). Nevertheless, amounts of carbon-emissions-freepower needed are quite large.

How can we diminish carbon intensity?

Climatestabilization

Developnon-fossil

energy sources

Sequestercarbon

Diminishend-usedemand

Carbon sequestration:A carbon-emission-free fossil-fuel economy

Solving the climateproblem with sequestrationrequires a moreambitious programthan yet exists.

DOE goals:1 GtC/yr by 20254 GtC/yr by 2050

A Biomass Future

Emitted Carbon Increases as H/C Decreases

Forest regrowth may store carbon, but warm the world

-0.4

-0.2

0

0.2

0.4

0 100 200 300 400 500

Equilibrium temperature change (K)

Year

Albedo effect

Carbon dioxide effect

Net effect

We need a major research program directed at an integrated analysis of energy policy options: physics, Earth system science, engineering, economics, resource limitations, developmental paths, etc.

Regrowing forests storecarbon [cooling effect] butthe dark forest canopyabsorbs more sunlight[warming effect]

This preliminary calculationdemonstrates the needfor systems-level analysis.

Carbon sequestration strategies

Strategiesnot requiring

separation

Sequestercarbon

Strategiesrequiring CO2

or O2 separation

GeologicOcean

injection

Silicateweathering

Landbiosphere

Oceanfertilization

Carbonateweathering

Airremoval

Carbon blackstorage

Non-fossil energy strategies

FusionFission

Solar PV Wind

Waves &currents

Developnon-fossil

energy sources

Renewable

Hydro

Tokamaks

Advanced fuel cyclesand confinement schemes

LWR

He-cooledpebble bed

Advanceddesigns

GeothermalFusionbreeder

Solar and Wind

Storage and distributionremain challenges

Solutions:1. H2

2. Global superconductingpower grid

Platinum requirement for high-density electrolyzers /fuel cells to produce 10 TW= 30 x today’s global platinum mining rate

Fission power

Known uranium reserves can provide 10 TW of power for less than 30 years--> breeder reactors

Inherently safe reactor designs ProliferationWaste disposal Advanced breeding conceptsRecovery of 235U from low-grade ores or seawater

Fusion

Despite recentadvances, fusionis unlikely to be apower source inthe next 50 years

Fusion as aneutron sourcefor hybrid fusion/fission breeders

Space options

Space transmission

Space solar PV

Lunar solar PV

Asteroid/lunar mining

Geoengineering

Reflect or scatter incoming solarradiation

Preliminary conclusions on enabling technologies requiring additional

investment Analysis

Integrated analysis considering physics, engineering, resource limitations, environmental considerations, economics, developmental paths, etc.

Sequestration Separation technologies Geochemical strategies and other advanced concepts

Renewables Global superconducting electric grid with smart load-balancing H2 storage and distribution network

Fission Uranium exploration technologies Extraction of uranium from low-grade ores and seawater

Fusion Fission/fusion breeders

Space options Mining of asteroids and the moon Solar power satellites

IPCC WG III – MitigationFailure to quantitatively address the real problem

“A broad array of technological options have the combined potential to reduce annual global greenhouse gas emission levels close to or below those of 2000 by 2010 and even lower by 2020. “ IPCC TAR WGIII – “Mitigation”

IPCC TAR WGIII failed to quantitatively address carbon-emissions-free power

requirements beyond the Kyoto time frame address technical, physical, and resource limitations on

potential technologies

Develop Off-the-Shelf Albedo Changers

Whiten roofs and blacktop in cities

>> saves electrical power for air conditioning, cools planet

Explore cloud production

>> reflects visible, may retain infra-red

Increase clouds over tropical oceans

>> couple with coal-burning plants?

Examples of limitations

To add 1 GW of primary power capacity each day would require Biomass @ 5 W / m2 200 km2 land area suitable for agriculture

each day Wind @ 30 We / m2 20 km2 suitably windy land area each day [+

storage and distribution] Solar @ 66 We / m2 5 km2 of solar cells on suitably sunny land

each day [+ storage and distribution] Fission @ one 300 MWe fission plant coming on line each day

[assuming energy can be used as electricity! 1 GW if needed for heating, etc.]

If you don’t like my numbers, try this at home with your own!!!

Solutions must be applicable to developing countries, where most of the increase in emissions is expected to occur. Ideally, we would find low-capital, safe, environmentally acceptable

energy sources that could be applied on a large scale Such energy sources do not exist [yet?]