From: ems@michael.apple.com (E. Michael Smith)
Newsgroups: sci.energy
Subject: Re: SOLAR efficiency
Date: 29 Sep 92 07:02:12 GMT
Organization: Apple Computer Inc, Cupertino, CA

In article <19vd9fINNahj@gap.caltech.edu> carl@SOL1.GPS.CALTECH.EDU writes:
>In article <1992Sep21.203259.17083@michael.apple.com>, ems@michael.apple.com (E. Michael Smith) writes:
>===Does anyone know the present percentage supplied by PEAKing capacity?
>===This is the immediate penetration available to the solar market.  
                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>==
>==Not really.  You see, current peaking capacity is dispatchable.  I.e., when
>==it's needed, it's available.  Not so with solar.  
>=
>=On a stochastic basis, it is!  That is, you can choose NOT to use it
>=when you have excess (just like a gas turbine) and MOST of the time
>=MOST sites will have available power matching demand peaks (just as a 
>=turbine site can be down at the wrong time.  BOTH are stochastic, they
>=just have differing degrees and differing reasons for being 'down')
>
>My point was that the penetration available to solar is considerably less
>thanthe total peaking capacity;  i.e., that your estimate of penetration
>available was too high.  Certainly solar can replace SOME peaking capacity.

So we are arguing over the middle ground with no numbers on either side.
This could drag on a long time ...

>=Note that I said this market is 'available' to solar, not that solar
                                   ^^^^^^^^^^^^^^^^^^^
>=could dominate it or could completely obsolete all other forms of peaking
>=plant.  The difference?  Right now we have to use expensive peaking 
>=plant to meet a demand surge that exactly matches solar.  To the extent
>=that this is true, solar can eliminate the need for that peaking capacity.
>=That doesn't make solar a pure peaking plant, but it reduces the NEED for
>=such completely dispatchable plant.
>
>True.  Meaning that it can replace some fraction of the current peaking
>capacity, not that it can replace it ALL as your original post claimed.

My original post is quoted at the top.  It, too, says 'penetration 
available to solar'.  I have NOT claimed that solar CAN or WILL 
replace ALL peaking plant, as you assert I did in the above sentence.

I have only said that the peak market is the one that is available
for solar to penetrate.  It 'has a shot' at replacing peak plant.  
It has no hope, for one hell of a long time to come, of replacing
baseload.  Are we arguing over something we agree on?

>=IN A GIVEN AREA.  Just as a single GW nuke can be down, or a turbine
>=site, or a Hydro site, or ...  It has been a LONG time since the entire
>=SUNBelt was cloudy on the same sunny day ... or even an entire region...
>
>Again, that simply means that solar can't replace ALL of our current peaking
>capacity.

Actually, it means that it has to be very very cheap to replace all
our current peaking capacity ... a level of cheapness that is not 
likely to happen.  Even then, things like hydro exist due to flood
control with or without peak rate charges.

>==When one of
>==those days occurs, the utilities still need their current conventional peaking
>==plants available.  
>=
>=OR the Arizona Solar Plant will be asked to ship some extra MWatt-hrs to
>=Texas for a day,
>
>And what of the customers who would've been getting that energy otherwise?

On a stochastic basis, there will always be SOME clouds SOMEWHERE so
you build enough plant to allow for that percent of the total to be 
shaded and still deliver the total quantity you need.  Today it may
be Arizona selling to Texas, tomorrow Texas selling to Arizona.  In
both cases there is more power shipped, but still no need for conventional
peaking plant.

The only problems come in when there is an abnormally high AVERAGE 
cloud cover or an abnormally low average cloud cover.  In the first
case it is just like a nuke scraming or a turbine site being down
for unexpected failure.  Handled the same way.  In the second case,
you have some extra watts you can throw away or sell cheap (or 
even throttle back your hydro or nuke a little bit).  

>=Yes, there WOULD be more frequent interchange of power from region to
>=region needed (since clouds can be a regional thing), but that does not
>=prevent solar from displacing much of the present peak supply (all but
>=the fraction needed to handle demand that didn't coorelate with solar 
>=availability)  Truely extraordinary events that take out an entire
>=section of the country would be handled much as they are today, I'd wager.
>
>To the extent that total solar energy available from all over the country
>varies from day to day, solar power will be unable to displace its full
>capacity in other peaking plants.

OR you overbuild the quantity of solar plant such that it has enough
power produced on bad days to match the prior peaking plant.  That 
decision rests entirely on the marginal cost of solar vs other peaking
plant.  This is the same as overbuilding gas turbins to ensure that
there are enough megaW-hrs when you want them, even if you lose a 
couple from thrown blades ...  The time scale may be shorter, but
the reasoning is the same ...  Thus the market penetration available 
to solar is the present peaking plant and the degree of actual 
penetration achieved is dependent on how low solar cost gets.  The
most likely scenario is one like LUZ, solar thermal with gas fire
available as backup.  

-- 

E. Michael Smith  ems@apple.COM

'Whatever you can do, or dream you can, begin it.  Boldness has
 genius, power and magic in it.'  -  Goethe

I am not responsible nor is anyone else.  Everything is disclaimed.