Geothermal energy for sustainable and green energy supply in the future

Deep Underground Science and Engineering (DUSE) publishes this special issue on geothermal energy. The guest editors of this special issue are Prof. Ranjith Pathegama Gamage (Monash University, Australia), Prof. Zhongwei Huang (China University of Petroleum, Beijing, China), and Prof. Bing Bai (Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, China). Geothermal energy is one sustainable and renewable energy and currently a hot research topic in research and development. Geothermal energy supply is one of the long-term efforts for carbon footprint reductions to tackle climate change issues. The development of geothermal energy includes exploration and extraction processes. This special issue is to highlight the challenges on the exploration and extraction of geothermal energy such as initial high cost and difficulties in heat extraction from deep underground. This special issue focuses on new geothermal extraction system, new theory, new technology, new application of latest techniques such as artificial intelligence, and potential environmental effects. This special issue publishes 10 articles with authors from different countries. An article is contributed by Chinese researchers on the site investigation for geothermal potential evaluation. They propose an integrated geophysics technique by combining multiple geophysics techniques with a new data processing method and apply it to the site investigation of the geothermal potential in a county. A Finnish researcher publishes an article to highlight the challenges and precautionary measures to overcome the difficulties in deep borehole heat exchanges. An article by US researchers explores possible geothermal-mechanical alternations due to heat exchange and extraction in geothermal systems. This article certainly provides new insights into the geothermal energy research and practice. Researchers from Morocco present a status and prospects article on the development of geothermal energy in their country. Several interesting articles on geothermal reservoirs appear in this issue. A joint multinational research effort by researchers from the United Kingdom, Belgium, China, and Indonesia reports the results of experiments on fluid-rock interaction for potential carbon storage in geothermal reservoirs. Their experimental results have provided some insightful findings on the subject matter. In addition, a group of researchers from China investigates the impact of well placement and flow rate on production efficiency in fractured geothermal reservoirs. Another group of Chinese researchers provides a state-of-the-art review on research and development for the thermal energy extraction from deep hot dry rock reservoirs. These three articles are certainly useful to researchers and engineers in geothermal energy fields. An article by Chinese researchers reports the development of a thermal stress loading technique for mechanical tests on hot dry rock. Last but not least, artificial intelligence also plays a role in geothermal energy research. Researchers from the United Kingdom and Saudi Arabia publish a state-of-the-art review on the applications of artificial intelligence in geothermal energy exploration. Another paper written by researchers from Saudi Arabia highlights the use of deep machine learning to tackle geothermal energy research and production. The above articles are the evidence that geothermal energy research in deep underground has attracted more and more attentions in the world. With the publication of this special issue, DUSE welcomes continuous contributions of high quality and innovative research works on geothermal energy in its future issues.