Large-Scale Geological Carbon Sequestration - Introduction to Carbon Capture and Sequestration - page 508

anemometer. Eddy-covariance towers can range from 1 m in height to
many hundreds of meters with higher towers providing greater spatial
averaging. Figure 10.5.9 (b) depicts the turbulent eddies that the sonic
anemometer measures at high frequency along with CO 2 concentration
to estimate a net vertical CO 2 fl ux. The eddy-covariance method has
proven capable of detecting a known leakage signal in the shallow-
release test carried out in Montana [10.54].
The other proven fl ux-measuring approach uses an accumulation
chamber. This simple device consists of a headspace sealed to the
ground surface and connected by inlet and outlet tubes to a gas analyzer
and a pressure transducer. The tubing carries gas from the chamber to
the analyzer and back to the chamber while keeping the pressure con-
stant in the chamber. The rate of change of CO 2 concentration in the
chamber is a measure of the fl ux of CO 2 into the chamber. Figure 10.5.10
shows an example of an accumulation chamber deployed on the soil
surface. Accumulation chambers provide accurate measures of soil CO 2
fl ux, but many measurements are needed to provide spatial coverage
(e.g., Lewicki et al . [10.53]).
In this chapter, we have taken a continuum scale view of geological
carbon sequestration and reviewed the modeling approach to under-
standing sequestration processes, the methods of capacity assessment,
potential hazards, and monitoring approaches. Overall, based on these
Figure 10.5.10 Accumulation chamber
Accumulation chamber (approximately 10 cm in diameter) deployed on the soil surface
showing inlet and outlet tubing that connects to a gas analyzer. Picture by USGS .