John
Coalescence can be reduced if they can make drops the same size and give
them an electrostatic charge. There is usually a potential gradient of
about 100 volts per metre, positive upwards, in the earth's
electrostatic field. If the drops are charged negatively there will be
a small upward force. This would be good if you want a long drop life
but bad if you change you mind following a second Pinatubo.
Stephen
Emeritus Professor of Engineering Design
Institute for Energy Systems
School of Engineering
Mayfield Road
University of Edinburgh EH9 3JL
Scotland
Tel +44 131 650 5704
Mobile 07795 203 195
www.see.ed.ac.uk/~shs
On 06/10/2011 14:22, John Nissen wrote:
Dear Matt,
It was good to talk to you this morning. I've sent you the agenda for
the workshop, 15th-16th October.
You make an interesting point about good dispersal, partly to
reduce/delay coalescence. Mark Massmann has suggested that LAIR
(liquid air) could be used. I'm copying this from a separate thread
on [geo]:
[quote]
John-
I agree that Lair could be an ideal "agent" for evenly dispersing
particles in the stratosphere (or even for dispersing salt particles
over marine clouds), if those particles remained evenly suspended in
the liquid or could be evenly "mixed" prior to expulsion. Simple
laboratory testing should be able to answer these questions for
different materials and particle sizes.
I think it's important to emphasize that the expansion of Lair
into air increases dramatically with altitude, so that a sea level
expansion ratio of 870 times would increase to 7,500 times at 50,000
ft (15.2 km) and 12,000 times at 60,000 ft (18.3 km)! This might play
a key role in attaining a globally-scaled SRM effect, enabling each
payload to evenly spread particles over a volume that is thousands of
times larger than other methods.
When also considering the use of very large tanks (i.e. very
large payloads) and a fleet of heavy-lift aircraft, it becomes more
feasible to imagine how a globally-scaled effect could be attained.
Mark
[end quote]
Best wishes,
John
---
On 05/10/2011 23:05, John Nissen wrote:
---------- Forwarded message ----------
From: *matthew watson* <[email protected]
<mailto:[email protected]>>
Date: Tue, Oct 4, 2011 at 11:12 AM
Subject: [geo] Re: SPICE Testbed Delay
To: geoengineering <[email protected]
<mailto:[email protected]>>
Hi Mark,
Dispersion is not an explicit part of SPICE, but we do approach the
problem
during the lab measurements (where dispersal is key to good optical
measurements).
There are studies out there that suggest particles would have issues
with
coalescence (particularly Heckendorn). We are also looking at a
precursor gas,
although this would obviously give you (potentially) much less control
over
particle size.
The general consensus I think is that aircraft have a better chance of
overcoming
the problem.
Matt
On Oct 3, 2:21 pm, Mark Massmann <[email protected]
<mailto:[email protected]>> wrote:
> Does the SPICE testing include some kind of measurement for how well
> particles will disperse?
>
> It seems that an aerosol approach which discharges from a stationary
> nozzle, as would be the case with a tethered balloon, would cause
> unwanted coalescing of smaller particles onto larger particles,
> limiting albedo benefit and lifetime before fallout.
>
> Unless I'm mistaken, my understanding was that even if an aerosol was
> spread using high altitude aircraft, re-seeding over the same region
> could cause this same problem to occur. If that is the case, can
> someone explain how this wouldn't be a problem for a stationary
> approach?
>
> Thanks-
> Mark
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