2012 John Jaeger Lecture: Introducing Geotechnical Design to Shallow Geothermal Systems
Professor Ian Johnston
Contrary to the popular view of geothermal energy, shallow geothermal systems make use of the ground at normal temperatures within a few tens of metres of the surface as a heat source in winter and a heat sink in summer to heat and cool buildings. A ground source heat pump or GSHP, in combination with a series of ground loops carrying water, is used to move the heat from the ground to a building and vice-versa. These systems go by a variety of names including shallow or direct geothermal systems, ground energy systems, ground source heat pump systems and geoexchange systems. Their two main advantages are that they can reduce electricity consumption and therefore running costs by factors of about 4 or 5 and can reduce greenhouse gas emissions by a similar amount. These systems are extensively used in other countries but are not common in Australia. It is likely that this will soon change.
This presentation will explain the principles of the technology and give examples of different installations. Current methods of design will be discussed and it will be argued that while there is considerable guidance about the above-ground components of these systems, the understanding of the performance of the below-ground components is still comparatively crude and conservative. This situation has led to capital costs which can be considerably greater than they need to be. Geotechnical engineers are now becoming involved and it is likely that their contributions will significantly benefit system efficiency, economy and effectiveness. Some recent developments on system design will be presented.
Ian Johnston was born in New Zealand but received the majority of his education in England. He graduated with a Bachelor degree in civil engineering with first class honours in 1968 and a PhD in geotechnical engineering in 1972. Both degrees were from the University of Southampton. After 3 years working in Europe, the USA and the Persian Gulf, he moved to Australia to join the Department of Civil Engineering at Monash University where he was a lecturer, senior lecturer and associate professor. In 1993, he was appointed Professor and Dean of Engineering at Victoria University of Technology. In February 1998, he returned to full time consulting with Coffey Geotechnics as a Senior Principal. In May 2009, he moved back to academia with his appointment to the Golder Associates Chair of Geotechnical Engineering at the University of Melbourne.
Although his interests have covered a wide range of topics, Ian is probably best known for his work on soft rock in civil and mining engineering. He has published over 100 technical papers and has undertaken substantial work in Australia and overseas both as an academic and as a consultant. Since taking up the University of Melbourne chair, he has developed a strong interest in shallow geothermal energy. His research group is now growing rapidly and has established several monitored field test facilities.
Ian has received several teaching and research awards and has had considerable input into the activities of many professional societies, committees, boards and other technical groups, locally, nationally and internationally.
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