Brightsource and Bechtel Missed the Opportunity for Co-generation at Ivanpah Solar-Thermal Station
Less than two years ago, I wrote about the rush to industrialize the Mojave Desert with ever-larger solar thermal arrays. The most notable example was Brightsource Energy’s
mega-solar plant in California’s Ivanpah Valley, near Primm, Nevada.
Together, the three Brightsource units at Ivanpah obliterated 3,500
acres of fragile desert habitat, replacing it with 170,000 motorized,
articulating mirrors and three massive receiving towers.
On September 24, 2012, Brightsource confirmed that it had synchronized their Unit 1 station with the existing electrical power grid. Although a photo on their website
shows most, if not all of the Unit 1 mirrors in operation, no one
other than the plants operators knows how many of the articulating
mirrors pointed at the receiving tower during synchronization.
While testing prior to synchronization, operators focused many of the
Unit 1 mirrors to either side of the receiving tower. Photos taken
during the test procedures show an ominous “solar flux”
to either side of the receiving tower. As additional heat for steam
generation was required, operators quickly moved standby mirrors to
focus directly on the receiving tower. Although it amounted to a
“proof-of-concept” connection, in the months that have followed,
Brightsource has yet to announce repetition of the synchronization
process.
Since
the Ivanpah project represents a quantum leap in solar thermal power
generation, no one knows if it will work as planned. Will plant
operators be able to point all 170,000 panels at the three receiving
towers on any given day? Will the intensity of the reflected solar flux
destroy the steam generators at the top of each tower? If Brightsource
knows the answer to these questions, they are not talking. Their press releases
featured platitudinous and self-congratulatory rhetoric about their
first synchronization, but little else about testing protocols and
procedures.
Maybe the Ivanpah mega-solar plant will succeed and maybe it will fail,
but one mega-mistake is obvious. When Bechtel Corporation planned the
facilities for Brightsource, they omitted any onsite thermal storage
capability. If the plant ever works, it will produce power only when
the sun is shining. When 
questioned,
Brightsource said that they needed to get “several” plants working
without onsite thermal storage prior adding that complexity to future
projects. In other words, the technology is not yet ready to do it
right.
As we know, the electrical grid is a complex and vulnerable
infrastructure. Adding or subtracting too much power too quickly can
cause cascading shutdowns of the adjacent grid. If Brightsource and
Bechtel can simultaneously synchronize all three units with the grid,
the lack of onsite thermal storage will limit electrical power
production. If liquid-sodium thermal storage was present at Ivanpah, it
could help balance and augment power generation at the site. With
onsite thermal storage, co-generation could begin prior to sunrise and
the mirrors could come online as 
the
thermal storage dissipated. That would allow for a smooth ramp up of
power entering the electrical grid. Without co-generation from onsite
thermal storage, operators must bring each unit slowly up to power.
Once operators achieve that elusive synchronization with the electrical
grid, they can then focus additional mirrors on the receiving towers.
At some point during the day, one would hope that all 170,000 mirrors
would focus on the towers.
In the late afternoon, operators would refocus more mirrors away from
the receiving towers. By sunset, the towers would go dark, steam
generation would cease and the process of disconnecting each of the
three units from the power grid would commence. The following morning,
each unit would go through the delicate process of reheating and
synchronization with the grid. The situation almost guarantees that the
massive plant will rarely achieve maximum power output and will spend
much of its time ramping up and ramping back down.
No one has said what would happen if a desert thunderstorm
were to move rapidly over the solar array. What effect would so rapid a
withdrawal of power do to power generation and synchronization to the
electrical grid? What effect would a downpour have on the superheated
receiving towers? If storms were in the forecast, the plant would have
to operate at lower power, in anticipation of possible weather related
shutdowns.
Like an old-fashioned steam locomotive, contemporary steam generators are more efficient and last longer when they operate continuously. Unlike a diesel electric locomotive, which can be brought up to operating temperature quite quickly, the firebox of a steam locomotive is kept hot until it is taken out of operation for maintenance or repair. Restarting these ancient “steam generators”
is a time consuming and delicate process. Likewise, daily thermal
cycling of the super-heated steam generators at Ivanpah guarantees
premature wear and increased operating costs.
In
their haste to design and build the largest solar thermal energy
station ever, Brightsource and Bechtel have made two potentially fatal
errors. First was the aforementioned lack of onsite thermal storage and
co-generation. Second was their use of single-sided mirrors for
focusing sunlight on to the receiving towers. Had Bechtel taken a
little more time in designing the systems, they could have designed the
170,000 articulating mirrors to flip over, thus exposing passive solar electrical panels affixed to their undersides.
If they had utilized this scheme, the majority of panels could start
each day in passive solar mode, generating sufficient electrical energy
to synchronize with the grid. Upon achieving synchronization,
operators could begin flipping panels so that their mirrored sides
would focus on a receiving tower. As sundown or a 
thunderstorm
approached, operators could begin flipping panels from reflecting mode
to passive reception mode, thus smoothing the ramping down of
electrical generation and eventual disconnection from the grid.
The key to this plan is to switch quickly from solar reflecting mode to
solar receiving mode. Before state and federal regulators approve
construction of any additional solar thermal plants in our fragile
desert environment, they should require both thermal storage and
passive solar additions as part of any new plant construction.
By James McGillis at 05:42 PM | Environment | Comments (0) | Link
