Thursday, 16 June 2011
Geothermal Energy Renaissance
At the end of the Queensland Geothermal Workshop last month I expressed the
view that the geothermal energy sector could be about to start an upswing after
a disappointing year. Since then I have become even more optimistic. Admittedly,
there is no solid proof yet but there are many positive signs that lead me to
believe that Australian geothermal energy sector will start rejuvenating after
our Annus Horribilis.
Some of the reasons for my optimism are based on overseas developments. I was
in the Geothermal Technology Program (GTP) review in Bethesda, Maryland, last
week. This is a program that has been investing over $500m over the last three
years in geothermal technology component development and demonstration projects.
This is in addition to the $1660m spent in 1976-2008 as shown in the following
graph.
During the review presentations last week, there were quite a few projects
showing good progress. Obviously, there were dud ones too as expected in any
large program like this. Across the portfolio, I think there is a very good
possibility that substantial improvements will be demonstrated on each one of
the three major challenges facing the EGS industry today, i.e. the flow rate,
the cost of drilling and the power conversion efficiencies.
How to Double the Flow rate
Under the heading of flow rate, there are two projects that I found
particularly interesting. One is the AltaRock Newberry project. This is a $44m
project with the aim of achieving a single well mass flow rate of 75 kg/s from
the Newberry Volcano EGS site. The project team is hoping to achieve this through
multi-zone stimulation and drawing the fluid from three horizons. While there
is a large team of participating organisations, the crucial technology, i.e.
the diverter technology, seems to be AltaRock proprietary technology. The second
project under the same heading is a more modest one. It is a project by Sandia
Laboratories and involves constructing a gas generator at the reservoir level
to create detonation waves as a new method of reservoir stimulation. This should
be particularly useful in creating near-hole permeability.
How to reduce the Cost of Drilling by 20%
At the GTP Review meeting, under the heading of drilling, the most noteworthy
project was the Potter Drilling project. Readers of this blog will remember
the Potter Drilling project and should be pleased to know that it is progressing
well. There are other projects on drilling as well. But even incremental improvements
in drilling should be able to achieve the 20% cost reduction target.
How to increase the Power Conversion Efficiencies by 20%
The readers of this blog will know of the QGECE project to develop a supercritical
turbine over the next three years with the purpose of achieving up to 50% increase
in power production from a typical Cooper basin EGS resource, compared with
the existing alternative. It was very encouraging that there were three more
projects presented in the GTP Review last week with similar aims, i.e. aiming
to develop supercritical power cycles and supercritical power turbines. There
are two companies (General Electric and UTC) and one national lab (ORNL) with
research projects to develop supercritical cycles and turbines based on optimised
fluids and fluid mixtures. The following chart is for example from the GE presentation:
GE examined an array of fluids and the two charts above compare the performance
of the best fluid at any temperature against the baseline cycle performance
(R245fa and n-Butane).
Under the power conversion heading, another exciting development last week
(although not in the GTP review) was the announcement by Wasabi that there is
going to be a combined heat & power plant in Taufkirchen in he next couple
of years producing 4.5MWe of electricity using the Kalina Cycle technology.
This is good news because there has been a hiatus in Kalina Cycle deployment
since 2009 when the 3.4-MWe Unterhaching project and the much smaller Bruchsal
projects were built by Siemens. The new Taufkirchen project will put Kalina
back into the competition and the geothermal industry desperately needs competition
in this area to achieve the targeted efficiency increases.
It is good news that the QGECE and its partner Verdicorp is finally facing
good competition in developing new Power Conversion technologies that fit the
EGS paradigm.
When we speak of power conversion, we need to talk about air-cooled condensers
as well since very few of the Australian geothermal power plants will have the
luxury of water cooling. There were two presentations last week on new technology
development in this area. One was from UTC on their work with microchannel heat
exchangers to replace the finned tube bundles. The QGECE research agrees with
the UTC that microchannel heat exchangers would be superior alternatives to
finned-tube bundles in future air-cooled condensers. However, our research also
demonstrates that the metal foam heat exchangers, the flagship QGECE projects
in the heat exchangers program, could even be better. The second presentation
last week was by Dr Desikan Bharathan of NREL on hybrid cooling. This is about
using water sprays on hot days to cool the air on hot days. The QGECE is also
working on this problem too. We put in a proposal as part of a large solar flagship
bid to try and demonstrate hybrid cooling on a natural draft dry cooling tower.
Judicious use of water sprays in hybrid systems may offer considerable benefits.
The following chart from DR Bharathan's presentation gives the potential for
achieving more power from an air-cooled plant during the hottest part of the
day, which incidentally is also the time when the electricity sale price is
the highest:
 |
|
| The major geothermal basins in Germany host a network of aquifers
containing geothermal fluids at temperatures of up to 140oC at depths of
less than 5,000m.. The above is the geological cross-section of the Molasse
basin where the new Kalina plant is going to be built. |
The chart shows the net power for the steam
cycle plants (175°C resource temperature) over the course of an average
day in July in Reno, Nevada, using hybrid cooling systems (Bharathan, 2011).
The hybrid curves in the chart are obtained by spraying water to cool the
inlet air during the hot hours. It looks like one can almost achieve the
nighttime performance and possibly double the revenue because the electricity
at peak hours can be sold at higher prices. Note that Heller systems (vertical
placement of bundles) are slightly better. |
***
This is enough on technology. I will continue on the topic of geothermal renaissance
in future blogs.
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QGECE Weekly Seminar Schedule
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