Wednesday, 14 September 2011
Options to connect geothermal electricity to the market
We all know that the best known geothermal resources in Australia are away
from the power grid. Therefore, transmission lines up to a thousand kilometers
are needed to bring geothermal electricity to the grid. These lines are feasible
to build only at a minimum capacity of several hundreds of megawatts. This has
two implications. The first one is obvious, no one will make this investment
in a transmission line unless the potential resource is large enough and we
are confident that it can be exploited as planned. The second implication is
more subtle but probably as important from the point of view of the utility
planners. A 1000-MWe transmission line cannot be connected to any point in a
power network. There are technical issues such as voltage and small signal stability
as well as the reliability of supply. These depend on the characteristic of
the network and the local parameters around the node(s) the transmission line
is connected to.
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The QGECE transmission program has a been investigating these issues
for some time. Tapan Saha and Mehdi Eghbal will present a paper at the
AGEC 2011 Conference this November in Melbourne about their progress.
Yesterday, a QGECE PhD student supervised by Tapan and Mehdi presented
at the QGECE weekly seminar about the progress in his PhD and a preview
of a paper he will present in the IEEE Power and Energy Society Innovative
Smart Grid Technologies (ISGT) Asia Conference 2011 in Perth later this
year. Kazi has been developing analytical tools to examine the stability
and reliability and congestion issues as a part of his PhD thesis. In
the seminar yesterday, he presented his results as applied to a IEEE benchmark
network shown in the above image.
In his analysis, Kazi examined different transmission topologies. Every
generator of a remote generation cluster can be connected to the grid
on their own, which will create the so called ‘spaghetti network’. Alternatively,
a high-capacity line can connect the generation zone to load centers and
successive generators can connect to the high-capacity line. This is referred
to as the scale efficient network extension (SENE). The cost allocation
in this approach is of course the most debatable issue. Kazi's work indicates
that hub SENE approach appears to be the most economic option considering
capital investment. Moreover, proper selection of the hub location could
be useful to make this approach more attractive. This work so far has
been limited to a benchmark network which has a size comparable to the
Queensland grid but is not its representative. Kazi and the rest of the
transmission team are applying these tools now to the Queensland grid
using the power network models provided to the QGECE by Power Link.
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