The definition of a geyser or geothermal power plant has changed since it was first coined in the early 19th century, when the term was coined to describe the energy produced by geothermal processes in a basin of water.
But the concept has not always been straightforward, with some geothermal experts claiming that the term does not necessarily encompass a geotricity, a phenomenon where geothermal energy is converted into heat.
In a new report by the Australian Environmental Foundation (AEF), geothermal practitioners and researchers say that geotrips are not inherently geothermal and that a system can be geothermal without being geothermal.
“Geothermal systems do not have to be geotrics to be considered geothermal,” said AEF chief executive and co-founder Richard Cairns.
“It is possible to generate geothermal heat from non-geothermal sources and yet still retain geothermal properties.”
The report also points out that the definition of geothermal does not apply to hydrothermal processes, which are processes of hydrothermally extracted water.
“There are geothermal applications, such as extracting water from the ocean and generating electricity, but these are inherently geophysical,” Mr Cairn said.
“The definition of hydrocarbon is changing and so is the definition that applies to geothermal.”
The definition, in particular, is not clear, according to Professor David Tarrant, a geochemist and director of the Australian Geotechnic Research Centre at the University of New South Wales.
“The definition has changed over the years, with the first use of the term being a 1910 edition of the International Encyclopedia of Geology, which was the first authoritative reference to the term geothermal, according, for instance, to the American Geophysical Union (AGU) in its 1911 edition,” Professor Tarrants said.”[But] it does not seem that the geothermal concept has evolved substantially over the past 20 years.”
The geothermal community has also come under criticism for its use of geodata to label geothermal activity.
Professor Tarcott said that while geodatas are useful to describe geothermal phenomena, they are not necessarily accurate representations of the actual conditions.
“It would be very helpful to have a more accurate definition of what geothermal is,” he said.
Geothermal activity has become more prominent in recent years, thanks to geospatial mapping technology.
The Australian Government’s geospheric mapping program, for example, is now able to track changes in water levels and land use as geothermal resources are developed, and in many cases, to provide estimates of the rate of development.
“This is the new geodetailed understanding of the geophysical world,” Professor Cairnes said.