http://www.mdpi.com/journal/energies/special_issues/geothermal_power/ Dear Colleagues, Geothermal resources are used in the generation of electricity and for numerous direct thermal applications including space heating and cooling, industrial processing and agricultural applications. Increasingly, combined heat and power projects involving both power generation and direct thermal applications are helping to maximize not only resource utilization, but also economic return as well. Low temperature geothermal resources, coupled with heat pumps, provide both space heating and cooling. Recent trends in the geothermal industry include greater emphasis on low temperature power generation, combined heat and power, the development of enhanced geothermal systems, the conversion of abandoned oil and gas wells to geothermal producers and the extraction of minerals from geothermal brine, thus allowing for greater thermal recovery while at the same time providing an important additional source of revenue. As the demand for electricity and thermal energy steadily increases and fossil fuel prices spiral continually upwards, greater and greater emphasis is being directed toward the development of environmentally responsible and increasingly cost competitive renewable energy resources such as geothermal. This special issue covers current development trends as well as research and development directed toward enhanced geothermal system development and the extraction of minerals from geothermal brines. Dr. Gordon Bloomquist Guest Editor Submission All manuscripts should be submitted to energies@mdpi.com with a copy to the Guest Editor. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website. Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed Open Access monthly journal published by MDPI. Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this Open Access journal is 800 CHF per accepted paper. http://www.mdpi.com/1996-1073/3/8/1485/ Water in some form plays a critical role in geothermal projects, given current technology. This paper explores inconsistencies in treatment of water and geothermal resources at the federal and state levels, and discusses legal and practical issues the developer should consider, relating to use of water, geothermal resources, and alternative sources of water supply. The developer is urged to incorporate water resource planning into project planning beginning at the project feasibility stage, and to seek creative solutions, possibly in cooperation with key stakeholders in the project area, to secure needed fluid resources. http://www.mdpi.com/1996-1073/3/8/1485/ Mon, 23 Aug 2010 00:00:00 CEST Energies 2010-08-23 3 8 Communication 1485 1498 1996-1073 Securing Fluid Resources for Geothermal Projects in a World of Water Scarcity 2010-08-23 doi: 10.3390/en3081485 Kathleen Callison http://www.mdpi.com/1996-1073/3/8/1443/ The worldwide application of geothermal energy for direct utilization is reviewed. This paper is based on the world update for direct-use presented at the World Geothermal Congress 2010 in Bali, Indonesia (WGC2010) [1] which also includes material presented at three world geothermal congresses in Italy, Japan and Turkey (WGC95, WGC2000 and WGC2005). This report is based on country update papers prepared for WGC2010 and data from other sources. Final update papers were received from 70 countries of which 66 reported some direct utilization of geothermal energy for WGC2010. Twelve additional countries were added to the list based on other sources of information. The 78 countries having direct utilization of geothermal energy, is a significant increase from the 72 reported in 2005, the 58 reported in 2000, and the 28 reported in 1995. An estimate of the installed thermal power for direct utilization at the end of 2009, reported from WGC2010 is 48,493 MWt, almost a 72 % increased over the 2005 data, growing at a compound rate of 11.4% annually with a capacity factor of 0.28. The thermal energy used is 423,830 TJ/year (117,740 GWh/yr), about a 55% increase over 2005, growing at a compound rate of 9.2% annually. The distribution of thermal energy used by category is approximately 47.2% for ground-source heat pumps, 25.8% for bathing and swimming (including balneology), 14.9% for space heating (of which 85% is for district heating), 5.5% for greenhouses and open ground heating, 2.8% for industrial process heating, 2.7% for aquaculture pond and raceway heating, 0.4% for agricultural drying, 0.5% for snow melting and cooling, and 0.2% for other uses. Energy savings amounted to 250 million barrels (38 million tonnes) of equivalent oil annually, preventing 33 million tonnes of carbon and 107 million tonnes of CO2 being release to the atmosphere which includes savings in geothermal heat pump cooling (compared to using fuel oil to generate electricity). http://www.mdpi.com/1996-1073/3/8/1443/ Tue, 17 Aug 2010 00:00:00 CEST Energies 2010-08-17 3 8 Article 1443 1471 1996-1073 Direct Utilization of Geothermal Energy 2010-08-17 doi: 10.3390/en3081443 John W. Lund http://www.mdpi.com/1996-1073/3/8/1423/ The paper provides a critical overview of water desalination using geothermal resources. Specific case studies are presented, as well as an assessment of environmental risks and market potential and barriers to growth. The availability and suitability of low and high temperature geothermal energy in comparison to other renewable energy resources for desalination is also discussed. Analysis will show, for example, that the use of geothermal energy for thermal desalination can be justified only in the presence of cheap geothermal reservoirs or in decentralized applications focusing on small-scale water supplies in coastal regions, provided that society is able and willing to pay for desalting. http://www.mdpi.com/1996-1073/3/8/1423/ Tue, 03 Aug 2010 00:00:00 CEST Energies 2010-08-03 3 8 Review 1423 1442 1996-1073 Water Desalination Using Geothermal Energy 2010-08-03 doi: 10.3390/en3081423 Mattheus Goosen Hacene Mahmoudi Noreddine Ghaffour http://www.mdpi.com/1996-1073/3/6/1320/ Being a heat source or sink, aquifers have been used to store large quantities of thermal energy to match cooling and heating supply and demand on both a short-term and long-term basis. The current technical, economic, and environmental status of aquifer thermal energy storage (ATES) is promising. General information on the basic operation principles, design, and construction of ATES systems is discussed in this paper. Numerous projects in operation around the world are summarized to illustrate the present status of ATES. Hydrogeological-thermal simulation has become an integral part of predicting ATES system performance. Numerical models which are available to simulate an ATES system by modeling mass and heat transport in the aquifer have been summarized. This paper also presents an example of numerical simulation and thermohydraulic evaluation of a two-well, ATES system operating under a continuous flow regime. http://www.mdpi.com/1996-1073/3/6/1320/ Tue, 22 Jun 2010 00:00:00 CEST Energies 2010-06-22 3 6 Review 1320 1334 1996-1073 A Review on Concepts, Applications, and Models of Aquifer Thermal Energy Storage Systems 2010-06-22 doi: 10.3390/en3061320 Lee