Free Resources | Energy | Currents Newsletter | Mar/Apr 2003

Geodynamics Ltd. Begins Drilling Historic “Habanero 1”

The first commercial endeavor to develop geothermal power from a hot dry rock (HDR) resource is now underway in Australia. With the help of a $5 million federal grant, Geodynamics Limited began drilling its "Habanero 1" well. The well will extend about 3 miles under South Australia's Cooper Basin to tap one of the world's hottest geothermal resources. When the well is complete in 10 to 12 weeks, it is expected to reach an underground "hot spot" where rocks achieve temperatures of about 554 degrees Fahrenheit. The well represents the hottest ever drilled as well as Australia’s first deep geothermal well.

Chief executive Dr. Bertus de Graaf said the drilling of Habanero 1 was the first stage in developing an underground heat exchanger, to demonstrate the economic extraction of hot dry rock geothermal energy.

"Establishing this underground heat exchanger will open up the full potential of the world-class, high-grade HDR geothermal resource," he said.

"Habanero 1 is part of the first step of achieving our goal, to be an emission free base-load electricity generator using renewable HDR geothermal energy."

Dr de Graaf said Australian and international drilling experts had contributed to the design of Habanero 1, which is situated near Innamincka in South Australia.

How the Power Plant Works

The HDR geothermal process is a closed system, with two loops.

The first loop uses water to extract heat from the buried hot rocks. The simplest hot dry rock power plant comprises one injection well and two production wells. Cold water is pumped under pressure down an injection well where it flows through an underground heat exchanger in the hot granite. It is then returned to the surface through production wells.

Because this loop operates under pressure, the super heated water remains a liquid, with no steam generated.

The heated water (> 200°C) returns to the surface under pressure. The high temperatures of the hot water are transferred to the geothermal power station loop via a heat exchanger. This second closed loop uses liquids with a low boiling point (similar to those used in fridges and air conditioners) and this drives a turbine system.

The cooled geothermal water returns to the underground heat exchanger where it is reheated.

The twin loop system is known as a binary geothermal power plant.

Source: Geodynamics Limited (with permission)

Background and Potential

HDR geothermal energy is a source of renewable energy with a capacity to carry large base loads 24 hours per day, creating a strong potential to replace fossil fuels, rather than just augment them.

The identified energy potential locked up in known high heat producing granites in Australia is enormous. In principle, there is sufficient energy to meet the total electricity requirements of Australia for hundreds of years to come.

One cubic kilometer of hot granite at 240°C has the stored energy equivalent of 40 million barrels of oil when the heat is extracted to a temperature of 140°C. Australia is known to have several thousand cubic kilometers of identified high heat producing granites.

The energy stored at a depth of less than 5 km (i.e. within the “oil window”) within Geodynamics’ two geothermal Exploration Licenses totaling 985 square kilometers, is equivalent to 50 billion barrels of oil. By comparison, the proved oil reserves in the USA are estimated at about 30 billion barrels, and in Australia, 3 billion barrels.

Benefits of HDR Geothermal Energy

One of the main advantages of HDR geothermal energy is the low environmental impact. As the energy is derived from converting heat extracted from hot rocks there are no gas emissions. Unlike burning fossil fuels, no CO₂ is released into the atmosphere.

In addition, the process does not produce any waste dumps and has a low noise impact. The construction of a HDR geothermal power plant leaves only a small environmental footprint. Site disturbance is limited to drill holes and pipelines, and a building to house the power plant.

Since the known high temperature granite rocks in the Cooper Basin are at depths accessible by standard drilling rigs, the exploration and tapping of the resource is competitive with conventional fossil fuel power stations.

Conventional vs. HDR Geothermal Energy Technology

Conventional geothermal energy is generated from naturally occurring hot water and steam in rocks near volcanic centers. They are based on wet systems, from which the hot water and steam is harvested.

Conventional geothermal energy stations are well established across the globe, in countries such as the USA, Iceland, Italy, New Zealand, Japan and others. A total installed capacity of 9,000 MW is in place worldwide.

The energy of the hot geothermal fluids is converted into electricity using well-established geothermal power generating technology. This technology is also applicable to hot dry rock geothermal energy systems.

Because conventional geothermal stations rely on harvesting naturally occurring hot water and steam they are limited in scope and size. Over time the source of these fluids often diminishes. What’s more, these fluids are often linked to emissions of volcanic gasses and toxic elements (e.g. CO₂, H₂S, arsenic, mercury) and they are often corrosive.

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