Environmental Engineering Reference
In-Depth Information
region. Second, the considerable transmission bottlenecks and few inter-
connection points with neighboring facilities present significant curtail-
ment risks for wind developers as wind penetrations continue to increase.
Finally, domal salt formations such as those used at the existing Huntorf
and McIntosh sites exist in Texas. This geology has been proven to work
well under CAES operating conditions and thus poses limited risk.
Consequently, several parties have announced plans to develop CAES
projects in Texas including a 540 MW (4 × 135 MW) system in Matagorda
County based on the McIntosh Dresser-Rand design and utilizing a pre-
viously developed brine cavern.
CAESOperationandPerformance
Ramping, Switching and Part-Load Operation
The high part-load efficiency of CAES (see Figure 5.10) makes it well suited
for balancing variable power sources such as wind. The heat rate increase at
part-load is small relative to a conventional gas turbine because of the way
the turbo expander output is controlled. Rather than changing the turbine
inlet temperature as in a conventional turbine, the CAES output is controlled
by adjusting the air flow rate with inlet temperatures kept constant at both
expansion stages. This leads to better heat utilization and higher efficiency
during part-load operation [56].
The McIntosh CAES plant delivers power at heat rates of 4330 kJ/kWh
(LHV) at full load and 4750 kJ/kWh (LHV) at 20% load [58]. This excellent
part-load behavior could be enhanced in modular systems such as the pro-
posed Norton plant where the full output would be delivered by multiple
modules. In this case, the system could ramp down to 2.2% of the full load
output and still be within 10% of the full load output heat rate.
The ramp rates for a CAES system are also better than those of equiv-
alent gas turbine plants. The McIntosh plant can ramp at approximately
18 MW per minute—about 60% greater than for typical gas turbines. The
Matagorda plant proposed by Ridge Energy Storage is designed to bring its
four 135 MW power train modules to full power in 14 minutes (or 7 minutes
for an emergency start)—which translates to 9.6 to 19 MW per minute per
module. These fast ramp rates together with efficient part load operation
make CAES an ideal technology for balancing the stochastic variations in
wind power.
To initiate compression operation, the turbine typically brings the machin-
ery train to speed. After synchronization, the turbine is decoupled and shut
off and the compressors are left operating. This means that the turbines are
called upon to initiate both compression and generation. At the Huntorf
Search WWH ::




Custom Search