Geothermal - Volcanic

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Geothermal and plate boundaries

A map of volcanoes and geothermal power stations shows the boundaries of plates where volcanic activity is heating the earth making geothermal relatively easy to generate.


This heat either comes from hot rock welling up as it spreads the plates apart.

Or from friction as the plates are subducted back down under the continents into the mantle.




Iceland and Philippines generate 30% of their power from geothermal. NZ 10%

Iceland is unusual in being part of the sea floor spreading. It is on the junction of the two plates making the floor of the Atlantic ocean.  As the plates pull apart long volcanoes appear where the earth is ripped apart.

 Photo: Gretar Ívarsson

The Nesjavellir Geothermal Power Plant in Iceland



Australian geothermal - Hot rocks

Australia is behind much of the world in geothermal, because the hot rocks in Australia are heated not by volcanoes, but by radioactive decay, and residual heat.

Sources of geothermal heat

The decay of radioactive isotopes uranium-238 and thorium-232 together contributed 20 trillion watts to the amount of heat Earth radiates into space.  The other half of the heat comes from the cooling of the Earth since its birth. 

The rocks will only be hot if they are covered by a layer of insulating material such as shale or coal.

​There is a plan to preheat the water in coal fired power stations with geothermal heat from beneath the coal beds.


Various forms of geothermal energy

1) Volcanic heat comes from magma circulating from deeper below.

4) Hot dry rock is a new form of power no one has yet developed commercially. (2011)

This means water has to be brought in, and pushed down into the rock through cracks, widening them if needed, then up another bore hole to the power station.

There are HDR or "enhanced geothermal" systems currently being developed and tested in France, Australia, Japan, Germany, the U.S. and Switzerland.

Video of Geodynamics well at Innamincka



Geothermal in Australia

We have enough geothermal for 20,000 years. If we can make it work.

There are 48 companies prospecting, 10 on the stock exchange.

On the coast of Victoria there are hot wet rocks. They  have a great advantage. Just drill two holes, if needed, widen the cracks between them,  then pump the hot water from one to the power station, and return the cooled water to the second hole.

It is predicted that this will be the cheapest form of energy for Australia. Hot wet rocks are being developed in Australia and will be online soon.

In Victoria they are looking at old oil wells or exploration holes. The advantage here is it is very near major power lines so costs will be reduced.


Company Name↓ Area of operations↓ Furthest project advancement↓   ASX code↓
Geodynamics Hunter Valley, Innamincka Advanced pilot plant development   GDY
Petratherm Paralana Resource drilling   PTR
New World Energy Pilbara, Perth basin Resource drilling    
Green Rock Energy Roxby Downs, Perth basin Resource drilling   GRK
Pacific Hydro   Tenement appraisals    
Panax Geothermal Limestone Coast Pilot plant production wells   PAX
Greenearth Energy Anglesea, Gippsland Pilot plant planning   GER
Torrens Energy Parachilna Validation drilling   TEY
Southern Gold Ltd Roxby Downs Temperature mapping   SAU
Hot Rock Ltd Penola, Otway Basin, Chile, Peru Validation drilling   HRL
Origin Energy Joint venture partner     ORG
Air conditioning can be made much more efficient if the outside coils run through the earth or a body of water. This way the temperature difference is less in both summer and winter.


Kalina cycle

One of the problems is that with very small temperature differences, the efficiency is very low. (See Carnot theorem).

One way to use low temperature for generating power is to use the Kalina cycle.

Two liquids of different boiling points are mixed in proportions producing the desired boiling point. The usual mixture is Ammonia and Water.

The patents for this process are owned by Wasabi Energy Corp.

Read more


The IEA  says it may be possible to exploit ocean-floor geothermal vents directly without drilling, using an encapsulated submarine binary plant to produce power. The main challenges for offshore geothermal development include the distance to shore, water depth, grid connection and disturbance of marine life around hydrothermal vents. It says technology developed to exploit offshore wind and ocean energy may help meet these challenges.  

First projects by Australian companies

The reality is that Australian hot rock is very deep and power prices are not high enough to make an easy profit.

Most Australian geothermal companies are building their first projects overseas where the depths are less and the electricity price is higher.

Tasmania’s Kuth Energy is building a $100 million  8MW geothermal plant in Vanuatu with World Bank support. ref

Petratherm is working on projects in Spain and the Canary Islands. 

Hot Rocks Limited was pursuing projects in Chile and Peru,

Panax Geothermal and Origin Energy are working on large geothermal projects in Indonesia.

Geodynamics is working in Solomon Islands.


News on Solar Thermal:

Patent for drilling wells with projectiles.

2015 - Hypersciences have patented a method of drilling holes by repeatedly firing a projectile with an abrasive core. The "Earth gun" has a barrel powered by compressed explosive gases. When ignited they send the projectile into the ground at almost 2 km/s. At that speed, the projectile buries itself deeply in the rock until the desired depth is achieved. No one can predict what affect repeated concussive blasts could have on the sub-terrainian environment, groundwater, and geology.