This CF question is actually quite complex. You can have a CF of 0.7 for
a nuke but actually that's because it's working 70% of the time and for
30% it is broken or undergoing maintenance (often for longish periods of
days / weeks / months). A CCGT with a CF of 0.7 would most likely be
modulating its output to meet actual demand and the 30% of
non-generation would mainly represent times of low demand, with routine
maintenance timed to take place during low demand periods.
This means that the CCGT is making a far more valuable contribution to
electricity supply than the nuke: there are times while the nuke is down
when additional fossil supply will be needed to make good the shortfall
(adding to the nuke's effective emissions); and there are periods when
the nuke is generating when the CCGT would be on standby or shut down
for the night (reducing the nuke's effective emissions reductions). So a
KWh from a nuke does not directly compare to a KWh from a CCGT either in
terms of value, or in terms of CO2 emissions. This needs to be taken
into account.
Yes, can you contact the authors for their view? Oliver.
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On 23/08/2011 14:32, Stephen Salter wrote:
Oliver
Actual output for nuclear is typically around 0.7 but the carbon debt
was all incurred before operation and turning them off does not reduce
it. The carbon for the plant is all released before operation and if
this is delayed we may ask if there is a carbon equivalent of interest.
Let's ask Storm van Leeuwen.
Stephen
Emeritus Professor of Engineering Design
Institute for Energy Systems
School of Engineering
Mayfield Road
University of Edinburgh EH9 3JL
Scotland
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On 23/08/2011 13:36, Oliver Tickell wrote:
Stephen, I was interested to see your recent post, below.
Reading the paper, there is something I am not clear about. A nuclear
power station is typically on full blast all the time giving a
capacity factor of 1 (except when it has to go off). However a gas
plant will modulate its output according to demand, giving I would
guess a typical capacity factor of say 0.6 (guess).
So, when the authors compare nuclear power and CCGT emissions, are
they forcing the CCGT to have a CF of 1 like nuclear? If so this is
to greatly exaggerate the actual CO2 emissions that you would expect
from a CCGT.
Another factor to consider is that as we get more intermittent
renewables like wind and solar PV on the grid, the effect will be to
further reduce the CF of gas plant - since when wind is generating
strongly, CCGTs will scale back their output. This will further
reduce the CCGT's CO2 emissions
Regards, Oliver.
==========================================
Stephen Salter <s.sal...@ed.ac.uk> Aug 23 11:58AM +0100 ^
<mailbox:///C%7C/Documents%20and%20Settings/Oliver/Application%20Data/Thunderbird/Profiles/s4tkdjyp.Oliver/Mail/Local%20Folders/Inbox?number=128158075#digest_top>
Hi All
While a nuclear power station is working normally the main CO2 emissions
are the plant operators driving to work or slipping out for a smoke.
However quite a lot of oil is needed for more...
<http://groups.google.com/group/geoengineering/msg/6c0b24968aac4022>
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