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Energies, Volume 3, Issue 8 (August 2010), Pages 1423-1528

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Research

Jump to: Review

Open AccessArticle Direct Utilization of Geothermal Energy
Energies 2010, 3(8), 1443-1471; doi:10.3390/en3081443
Received: 2 July 2010 / Revised: 13 August 2010 / Accepted: 16 August 2010 / Published: 17 August 2010
Cited by 26 | PDF Full-text (207 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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). Full article
(This article belongs to the Special Issue Geothermal Power)
Open AccessArticle Biomass Steam Gasification with In-Situ CO2 Capture for Enriched Hydrogen Gas Production: A Reaction Kinetics Modelling Approach
Energies 2010, 3(8), 1472-1484; doi:10.3390/en3081472
Received: 9 July 2010 / Revised: 21 July 2010 / Accepted: 26 July 2010 / Published: 18 August 2010
Cited by 21 | PDF Full-text (638 KB) | HTML Full-text | XML Full-text
Abstract
Due to energy and environmental issues, hydrogen has become a more attractive clean fuel. Furthermore, there is high interest in producing hydrogen from biomass with a view to sustainability. The thermochemical process for hydrogen production, i.e. gasification, is the focus of this [...] Read more.
Due to energy and environmental issues, hydrogen has become a more attractive clean fuel. Furthermore, there is high interest in producing hydrogen from biomass with a view to sustainability. The thermochemical process for hydrogen production, i.e. gasification, is the focus of this work. This paper discusses the mathematical modeling of hydrogen production process via biomass steam gasification with calcium oxide as sorbent in a gasifier. A modelling framework consisting of kinetics models for char gasification, methanation, Boudouard, methane reforming, water gas shift and carbonation reactions to represent the gasification and CO2 adsorption in the gasifier, is developed and implemented in MATLAB. The scope of the work includes an investigation of the influence of the temperature, steam/biomass ratio and sorbent/biomass ratio on the amount of hydrogen produced, product gas compositions and carbon conversion. The importance of different reactions involved in the process is also discussed. It is observed that hydrogen production and carbon conversion increase with increasing temperature and steam/biomass ratio. The model predicts a maximum hydrogen mole fraction in the product gas of 0.81 occurring at 950 K, steam/biomass ratio of 3.0 and sorbent/biomass ratio of 1.0. In addition, at sorbent/biomass ratio of 1.52, purity of H2 can be increased to 0.98 mole fraction with all CO2 present in the system adsorbed. Full article
(This article belongs to the Special Issue Energy-sustainable Development)
Open AccessCommunication Securing Fluid Resources for Geothermal Projects in a World of Water Scarcity
Energies 2010, 3(8), 1485-1498; doi:10.3390/en3081485
Received: 22 July 2010 / Revised: 28 July 2010 / Accepted: 18 August 2010 / Published: 23 August 2010
Cited by 2 | PDF Full-text (168 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Geothermal Power)

Review

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Open AccessReview Water Desalination Using Geothermal Energy
Energies 2010, 3(8), 1423-1442; doi:10.3390/en3081423
Received: 22 June 2010 / Accepted: 2 August 2010 / Published: 3 August 2010
Cited by 27 | PDF Full-text (442 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Geothermal Power)
Open AccessReview Principles and Materials Aspects of Direct Alkaline Alcohol Fuel Cells
Energies 2010, 3(8), 1499-1528; doi:10.3390/en3081499
Received: 21 July 2010 / Revised: 6 August 2010 / Accepted: 16 August 2010 / Published: 24 August 2010
Cited by 116 | PDF Full-text (424 KB) | HTML Full-text | XML Full-text
Abstract
Direct alkaline alcohol fuel cells (DAAFCs) have attracted increasing interest over the past decade because of their favourable reaction kinetics in alkaline media, higher energy densities achievable and the easy handling of the liquid fuels. In this review, principles and mechanisms of [...] Read more.
Direct alkaline alcohol fuel cells (DAAFCs) have attracted increasing interest over the past decade because of their favourable reaction kinetics in alkaline media, higher energy densities achievable and the easy handling of the liquid fuels. In this review, principles and mechanisms of DAAFCs in alcohol oxidation and oxygen reduction are discussed. Despite the high energy densities available during the oxidation of polycarbon alcohols they are difficult to oxidise. Apart from methanol, the complete oxidation of other polycarbon alcohols to CO2 has not been achieved with current catalysts. Different types of catalysts, from conventional precious metal catalyst of Pt and Pt alloys to other lower cost Pd, Au and Ag metal catalysts are compared. Non precious metal catalysts, and lanthanum, strontium oxides and perovskite-type oxides are also discussed. Membranes like the ones used as polymer electrolytes and developed for DAAFCs are reviewed. Unlike conventional proton exchange membrane fuel cells, anion exchange membranes are used in present DAAFCs. Fuel cell performance with DAAFCs using different alcohols, catalysts and membranes, as well as operating parameters are summarised. In order to improve the power output of the DAAFCs, further developments in catalysts, membrane materials and fuel cell systems are essential. Full article
(This article belongs to the Special Issue Fuel Cells)

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