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considering energy policy issues, it is helpful to remember there
are a variety of different, and sometimes conflicting, imperatives
to be balanced. These include: 1) Assurance of Supply -
avoiding blackouts and lines for gasoline; 2) Low Total Cost
– where total costs include building costs and utilization, fuel
costs, operating costs and other grid costs; 3) Environmental
Issues – pollutants, green house gases, nuclear waste, land use
issues, etc; and 4) Energy Independence - the political,
foreign policy, military and balance of trade concerns with energy
imports. In general, wind generated electricity meets these needs
fairly well. Certainly with tax credits its cost is acceptable;
there are some bird kill and land use issues, but these are modest
compared to the environmental concerns with others energy sources;
and wind has significant energy independence benefits. All of these
strengths have been reflected in a truly dramatic growth of planned
and installed wind generation facilities during this first decade of
the 21st century.
While wind generation has the benefits outlined above and is
enjoying wide success, there has been a remaining controversy about
its availability 24/7. It is virtually a cliché that the wind is
fickle; it blows in different directions and different strengths
seemingly at random. As such there has been some concern about how
often will the wind blow and produce electricity, and when
electricity is needed will the wind be there? Everyone has
experienced a really hot day when the air is absolutely still, or a
really cold, still night. This concern with the 24/7 availability of
wind generation translates to questions about backup capacity to
satisfy peak demand, i.e. the first energy policy imperative -
Assurance of Supply. This question may be academic most of the year
when there is adequate back up capacity and even if the wind is
still for a while other electric plants will pick up the slack. But
during periods of peak demand, typically in mid-summer or mid-winter
the question is very important. That was certainly the case this
July during the record heat waves in California, then the East Coast
and finally the Southern States. Each region in turn experienced
record demand and issued pleas for conservation; commentators
expressed concern about blackouts. Under these conditions, the 24/7
availability of wind generation is not an academic question.
Over the last few years, two schools of thought have developed
about wind’s 24/7 availability. The first – ‘this is really not a
problem’. Proponents argue, ‘yes the wind is fickle, but wind
turbines are being installed in many, many windy locations and when
one location is still, you may expect others to be gusty. Thus wind
will have excellent 24/7 availability’. Others are concerned,
‘blackouts are very dangerous and simply not acceptable. Maybe we
need to build back-up generation for wind assets and maybe include
such backup in cost calculations, or otherwise significantly
discount wind generation when analyzing total grid capacity vs. peak
demand?’ Both schools have their advocates, and to date the
controversy is unresolved.
With this understanding of the 24/7 availability controversy in
mind, the recent experience of California is interesting. California
has been a pioneer in alternative electricity generation with many
decades of service from significant geothermal and wind facilities.
The Alamont Pass area, about 50 miles south east of San Francisco
was the nation’s first significant wind facility. With that start,
California today has 2,500 MW of installed wind capacity. That is,
these facilities are not being planned or under construction, they
are built and on line. 2,500 MW is a big number; a large nuclear
plant is 1,000 MW, a large coal plant is 500 to 800 MW, individual
wind turbines are 2 to 20 MW. Most significantly, wind is now
approaching 5% of California’s total electric generating capacity.
California’s electric grid planners want 7% to 15% of reserve
capacity between predicted total demand and total generating
capacity; as such the 24/7 reliability of their wind capacity, again
5% of California’s total capacity, is important.
So what happened in California during the mid-July heat storm
when that electric grid was put to the test, and California avoided
rolling blackouts amid a Level 1 Emergency in which Californian’s
were asked to raise their thermostats to 77 and many manufactures
and business voluntarily shutdown? By most people’s analysis, wind’s
performance was disappointing. Specifically during this period of
peak demand, statewide wind often operated at only 5% of capacity,
or less. The specific data is plotted in the attached graph. The
upper line shows the peak daily electric demand as recorded by the
California Independent System Operator, CASIO, during the heat
storm. Daily peak power usage increased fairly steadily in mid July,
reaching its peak on July 24 at 50,270 MW. Wind’s availability
during this same period is presented in the lower line. Specifically
this is the percent of the CASIO available wind capacity, 2,500MW,
which was actually putting electricity into the CASIO grid at the
time of peak demand on each day plotted.
By most measures these numbers are disappointing. On the day of
peak demand, August 24, 2006, wind power produced at 254.6 MW at the
time of peak demand. 254.6 MW represents only 10.2% of wind’s rated
capacity of 2,500MW. Another perspective on the data, over the
preceding seven days, August 17 to 23, wind produced at 89.4 to
113.0 MW, averaging only 99.1 MW at the time of peak demand or just
4% of rated capacity.
This data presents wind’s performance during roughly two week’s
of only one heat storm, California’s July ’06 storm. This author
recommends caution in reaching larger conclusions about its
significance. However as a minimum the data suggests that analysis
of wind’s performance during periods of peak demand in other grid
systems with different wind sited facilities would be useful. And
until other such data is available, this experience implies caution
in assuming a significant fraction of wind capacity will be
available for periods of peak demand such as California’s July level
1 emergency.
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Copyright 2005 CyberTech, Inc.
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