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Energies, Volume 3, Issue 8 (August 2010) – 5 articles , Pages 1423-1528

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424 KiB  
Review
Principles and Materials Aspects of Direct Alkaline Alcohol Fuel Cells
by Eileen Hao Yu, Ulrike Krewer and Keith Scott
Energies 2010, 3(8), 1499-1528; https://doi.org/10.3390/en3081499 - 24 Aug 2010
Cited by 302 | Viewed by 22464
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 DAAFCs [...] 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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168 KiB  
Communication
Securing Fluid Resources for Geothermal Projects in a World of Water Scarcity
by Kathleen Callison
Energies 2010, 3(8), 1485-1498; https://doi.org/10.3390/en3081485 - 23 Aug 2010
Cited by 3 | Viewed by 7852
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 to [...] 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)
638 KiB  
Article
Biomass Steam Gasification with In-Situ CO2 Capture for Enriched Hydrogen Gas Production: A Reaction Kinetics Modelling Approach
by Abrar Inayat, Murni M. Ahmad, Suzana Yusup and Mohamed Ibrahim Abdul Mutalib
Energies 2010, 3(8), 1472-1484; https://doi.org/10.3390/en3081472 - 18 Aug 2010
Cited by 84 | Viewed by 15674
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 work. [...] 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)
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207 KiB  
Article
Direct Utilization of Geothermal Energy
by John W. Lund
Energies 2010, 3(8), 1443-1471; https://doi.org/10.3390/en3081443 - 17 Aug 2010
Cited by 84 | Viewed by 23375
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 geothermal [...] 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)
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442 KiB  
Review
Water Desalination Using Geothermal Energy
by Mattheus Goosen, Hacene Mahmoudi and Noreddine Ghaffour
Energies 2010, 3(8), 1423-1442; https://doi.org/10.3390/en3081423 - 03 Aug 2010
Cited by 107 | Viewed by 16862
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 energy [...] 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)
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