Bright Water
An illustrated elevator talk
Russell Seitz
Fellow of the Department of Physics
Harvard University
seitz@physics.harvard.edu1
Copyright 2012 Russell Seitz All rights reserved
Many of the nation’s power
plants are in hot water
But not for the reason
you think
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At high noon in summer, most of the heat
load on a power plant cooling pond
doesn’t come from the power plant
IT COMES FROM THE SUN
A new technology can reduce
solar overload risks
by raising pond reflectivity :
3
BRIGHT WATER
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Microbubbles are mirrors made of air
The coarse air bubbles in seawater raise Earth’s
albedo only slightly because their cross section is small
However
The air in one cubic centimeter can just as well fill a trillion
one micron bubbles as a single one centimeter one.
From paper submitted
to Climatic Change
That can increase the ‘Mie scattering’
cross section of 1cc of air from
square centimeters
to
square meters
So a gram of air can reflect megawatts
over an area the size of a football field!
7
Refractive Index Contrast allows
simple devices to mix materials of
low reflectivity, like air and water,
to create HYDROSOLS
as bright as clouds in the sky
Proprietary
Proprietary
9
Microbubbles can take a long
time to rise to the surface
4/13/2015
Proprietary
10
Hydrosols need very little mass to brighten
& cool large expanses of water fresh or salt,
which can
REDUCE EVAPORATION
Making
at an energy cost of roughly
tens to hundreds of watts per hectare.
The question R&D has to answer is :
‘For how long ?’
Microbubbles
With a simple
Vortex nozzle
In a 50 liter tank
Start
Cutoff
+ 2 minutes
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It’s an important question because…
The Earth is as warm as it is because the
deep blue sea covering most of it soaks up
solar heat like black asphalt
SO DO COOLING PONDS
SOLAR HEATING IS REDUCED
WHEN SUBMERGED BUBBLES & PARTICLES
BACKSCATTER SUNLIGHT IN A PROCESS
CALLED ‘UNDERSHINE ’
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Thermal power station:
Watts/M2
Brightening the water ~10%
could increase T by ~4O K,
which would raise baseline
thermodynamic efficiency ~1%,
and prevent shutdowns due to
hot weather outflow overheating
Hydrosol cooling
could cut US coal
consumption by
millions of tons
a year
Proprietary
Too bright to meter ? Not quite:
Energy cost of creating
a brightness-doubling hydrosol
is microbubble surface energy
plus PV =
2,
~100 miliJoules / M
or 1 kilojoule/hectare
4/13/2015
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What about the RISKS ?
Impact on phytoplankton of less light :
Can be kept within cloud cover variation limits
Altered photosynthetic compensation depth
Plankton move up and down every day
Surface temperature changes will
alter local ecosystems
Yes - But may save some from destruction
NONE OF THESE OPEN WATER ECOSYSTEM
RISKS APPLY TO ISOLATED COOLING PONDS
Dividing the problem :
Science & Engineering :
Explore the limits of surface chemistry
and gas solubility
Engineer energy cost reductions in
microbubble generation & dispersion
Economics:
Make evaporation control an integral
part of the water business
Quantifying albedo benefits to convert
water brightening into tradable carbon
permits & offsets
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Bright Water can
Reduce urban temperatures (Adaptation)
Reduce fossil CO2 emissions (Mitigation)
Slow global warming by increasing the reflectivity
of the hydrosphere ( Soft Geoengineering )
Save U.S. businesses billions in energy costs
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Bright Water works like White Roofs,
but on a bigger scale
The global roof supply
is only 50 M2 per capita
Global water area is
over 1,000 times larger!
It’s easier & cheaper
to brighten one lake
than 10,000 roofs
The world’s real water problem is
that water is too cheap to conserve
Water is worth only $50 an acre, so it’s
hard to imagine a material cheap enough to
affordably stem its evaporation: even the
cheapest geotextiles cost >$10,000 an acre.
Hard, but not impossible, because
Air is cheaper than water
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