A comparison of the silica and Na-K-Ca geothermometers for thermal springs in Utah

The silica and Na-K-Ca chemical geothermometers do not always agree (within 25°C) when applied to hot springs in Utah. Some of the differences can be explained by mixing of hot and cold ground waters. However, the geology of the areas in which the springs arise must also be taken into account.     

Observations on the application of chemical geothermometers to some hydrothermal systems in Sardinia

There are many empirical geothermometers that utilize the composition of the elements dissolved in water, yet it is difficult to judge just how reliable they are when applied to low enthalpy thermal systems.The main objective of this paper is to show how a reasonable estimate of the temperature of some typical thermal systems in Sardinia can be obtained from the calculation of the saturation indices of water with some silicates in the local rock matrix. Despite some uncertainties, mainly regarding possible mixing phenomena, the applied methodology appears to give more reliable reservoir temperature values than those given by the empirical geothermometers.The method has been applied to thermal waters circulating in the crystalline basement rocks (granites) and in the sedimentary cover rocks (mainly volcanic effusive products, andesitic lava, ignimbrites, etc.). The temperatures calculated for the hydrothermal systems range between 50 and 110°C.     

Hydrogeochemistry of Damt thermal springs,Yemen Republic

The Damt thermal springs (40–45°C) flowing through travertine deposits belong to the Na–HCO₃ type of water and have higher pCO₂ ( from −118 to −058=PCO₂ from 007 to 026 atm) relative to cold Ca–SO₄− (Cl) groundwaters The cold waters have pCO₂ ranging from −186 to −250 (=PCO₂ from 0014 to 00035 atm) The chemical composition of the cold springs is controlled by evaporite deposits present in the Tawilah sandstone and Amran limestone formations while simple crustal dissolution coupled with CO₂-rich fluid–rock interaction control the chemical signature of the hot spring waters. The temperature of the feeding system based on the K ²/Mg geothermometer varies between 80 and 120°C Damt thermal springs appear to be related to a 10 000 year-old volcanic activity that led to the appearance of several craters in the area.     

Geochemistry of thermal springs around Lake Abhe,Western Djibouti

The Republic of Djibouti, occupying an area of 23,180 km², falls within the arid zone of East Africa and is located above the ‘Horn of Africa’, adjacent to the Red Sea. This country has several thermal springs and fumaroles distributed over three regions – Lake Assal, Lake Hanle and Lake Abhe. The most characteristic feature of Lake Abhe is the presence of several linear chains of travertine chimneys. The thermal waters are typical of the Na-Cl type near neutral waters rich in CO₂. These waters show an oxygen shift, indicating reservoir temperatures>200°C. The chemical signature of the thermal springs and the geology of the Lake Abhe region are very similar to the Tendaho geothermal area of Ethiopia. The geology, temperature gradient and its proximity to Damah Ale volcano make the Lake Abhe region a potential site for geothermal power development.     

Assessment of reservoir temperatures of thermal springs of the northern areas of Pakistan by chemical and isotope geothermometry

Chemical and isotope geothermometers, i.e. the Na–K, K–Mg, quartz and δ¹⁸O(SO₄–H₂O), have been applied to estimate the reservoir temperature of the thermal springs in the northern areas of Pakistan. The chemical types of the thermal waters and the effects of mixing of shallow cold water with the thermal end-members are discussed. These waters are neutral to slightly alkaline and have low dissolved contents. Sodium is the dominant cation in almost all the cases. In terms of anions, the hot waters of Budelas are of the SO₄ type, those of Tatta Pani are of mixed character (SO₄ and HCO₃), and the waters from the remaining areas show HCO₃ domination. An absence of tritium in Tatta Pani and Tato thermal springs indicates that they do not have any contribution of shallow young water. In the case of the Murtazabad springs, the wide range of tritium concentrations, negative correlations with surface temperature and Cl, and positive correlation between Na and Cl show that the shallow cold groundwater is mixing with thermal water in different proportions. For the mixed water of Murtazabad thermal springs, ‘isochemical modelling’ using the Na–K, K–Mg and quartz geothermometers indicates an equilibrium temperature in the range 185–200 °C. The δ¹⁸O(SO₄–H₂O) geothermometer gives relatively low temperatures for three springs, whereas two samples are close to the 185–200 °C temperature interval. The reservoir temperatures of Tatta Pani springs (100–120 °C), determined by Na–K and quartz geothermometers, are in good agreement. The δ¹⁸O(SO₄–H₂O) geothermometer gives a relatively higher range (140–150 °C) for most of the Tatta Pani springs. For Tato spring, the isotope and chemical geothermometers (except for the K–Mg) agree on an equilibrium temperature of about 170 °C. Reservoir temperatures of the remaining minor fields are not conclusive due to the lack of sufficient data.     

Hydrogeochemistry and geothermometry of Changal thermal springs,Zagros region,Iran

This study addresses the hydrogeochemistry of thermal springs that emerge from the Asmari limestone in a gorge at Changal Anticline in the vicinity of the Salman-Farsi dam. The Changal thermal springs vary in temperature between 28 and 40 °C. Chemical and isotopic compositions of the thermal waters suggest two distinct hydrogeological systems: a deep, moderate-temperature (∼40 °C) geothermal system recharged by deeply circulating meteoric waters, and a shallow cold aquifer system related to local groundwater. The source geothermal fluid temperature was calculated using different geothermometers and mineral saturation indexes. Based on chemical and isotopic data, it is hypothesized that: (1) mixing occurs between the ascending geothermal water and shallow cold water; (2) the resulting thermal waters reaching surface are a mixture of 80% local, shallow meteoric water and 20% geothermal water; and (3) the circulation depth of the meteoric water is about 1500 m. The thermal reservoir temperature is estimated to be between 70 and 80 °C according to calculations using different geothermometers and computation of saturation indices for different solid phases.     

The thermal springs of bockfjord, svalbard: occurrence and major ion hydrochemistry

The Troll and Jotun thermal springs of northern Svalbard, with temperatures of up to 25.6°C, are derived from a major fault forming the junction between Devonian sandstones and Proterozoic marbles, mica schists and gneisses. The Troll waters are dominated by Na–HCO₃ compositions and the Jotun waters by Na–Cl compositions. The pristine thermal water source has a sub-neutral pH and is highly reducing. Taken at face value, common geothermometers suggest temperatures at depth of 130–180°C for the Troll springs (corresponding to a depth of 1.6–2.3 km), with 10–30% thermal water diluted by 70–90% cold water. Such geothermometers may, however, be inappropriate to the cool, high CO₂ waters of Bockfjord, and real temperatures at depth and dilution factors are probably considerably lower. The salinity of the thermal water appears to be only partially derived from water–rock interaction; Br\Cl ratios suggest that seawater or possibly evaporites may be a source of chloride salinity.     

Effect of thermal, chemical and thermo-chemical pre-treatments to enhance methane production

The rise in oil price triggered the exploration and enhancement of various renewable energy sources. Producing biogas from organic waste is not only providing a clean sustainable indigenous fuel to the number of on-farm digesters in Europe, but also reducing the ecological and environmental deterioration. The lignocellulosic substrates are not completely biodegraded in anaerobic digesters operating at commercial scale due to their complex physical and chemical structure, which result in meager energy recovery in terms of methane yield. The focus of this study is to investigate the effect of pre-treatments: thermal, thermo-chemical and chemical pre-treatments on the biogas and methane potential of dewatered pig manure. A laboratory scale batch digester is used for these pre-treatments at different temperature range (25 °C-150 °C). Results showed that thermo-chemical pretreatment has high effect on biogas and methane potential in the temperature range (25–100 °C). Maximum enhancement is observed at 70 °C with increase of 78% biogas and 60% methane production. Thermal pretreatment also showed enhancement in the temperature range (50–10 °C), with maximum enhancement at 100 °C having 28% biogas and 25% methane increase.     

The source and heating mechanism for the Ahram, Mirahmad and Garu thermal springs, Zagros Mountains, Iran

The Ahram, Mirahmad and Garu low-temperature geothermal springs in the Zagros Mountains, Boshehr Province, Iran, emerge along the Ghatar-Kazeroon fault. The average temperature of the springs is about 40 °C and the waters have appreciable amounts of dissolved solids and hydrogen sulfide. Based on chemical analyses, including stable isotopes of the thermal waters and data interpretations, and on a comparison with fresh water springs and wells in the study area, we conclude that the hot waters are of meteoric origin. Because of the prevailing geothermal gradient, the waters are heated as they circulate deep in the system through joints, fractures and the Ghatar-Kazeroon fault. During their deep circulation, the waters come into contact with Hormoz Series evaporites and the oilfield brines, resulting in an increase in dissolved ion concentrations.     

The thermal springs of Bockfjorden, Svalbard: II: selected aspects of trace element hydrochemistry

Waters from the Trollkjeldene (Troll springs) and Jotunkjeldene (Jotun springs) thermal springs on northern Svalbard have been analysed by ICP-AES, ICP-MS and IC techniques for a wide range of major and trace elements. Although it is plausible that the thermal waters originate from a deep reservoir in siliceous rocks, it appears that a significant component of their hydrochemical signature is derived from dissolution of higher-level Hecla Hoek marbles. Rare earth elements (REEs) show some degree of enrichment of heavy REEs in the water phase, relative to the marbles and to the travertines that precipitate from the waters. A strong positive Eu anomaly is also observed in the waters, suggesting preferential mobilisation of Eu under reducing conditions. The ratio Nb/Ta is rather well-preserved between the marbles, the waters and the travertines.     

Application of the thermal network method to the transient thermal analysis of multichip modules

In recent years there has been a growing demand for smaller and lighter electronic circuits which have greater complexity, multifunctionality, and reliability. High-density multichip packaging technology has been used in order to meet these requirements. The higher the density scale is, the larger the power dissipation per unit area becomes. Therefore, in the design process it has become very important to carry out a thermal analysis. However, the heat transport model in multichip modules is very complex and its treatment is tedious and time consuming. This paper describes an application of the thermal network method to the transient thermal analysis of multichip modules and proposes a simple model for multichip modules as a preliminary thermal design tool. Based on the results of a transient thermal analysis, the validity of the thermal network method and the simple thermal analysis model are confirmed. © 1998 Scripta Technica, Heat Trans Jpn Res, 26(8): 541–553, 1997     

Isotopic composition of dissolved sulphate and hydrogen sulphide from some thermal springs of Sicily

Samples of some thermal springs from Sicily have been analysed for the isotopic composition of sulphur-bearing species. The values of δ³⁴S(SO₄²⁻ (range: +7.3, +31.7‰), δ³⁴S(H₂S) (range: −12.2, +27.8), δ³⁴S(S°) (range: +1.9, +24.5) and δ¹⁸O(SO₄²⁻) (range: −2.5, +23.9) obtained show such a remarkable variability in data as to hypothesize different genetic processes concerning these species.Furthermore, from the available experimental data, the relationship between the isotopic composition of the sulphur in the dissolved sulphate and in the associated hydrogen sulphide (ΔSO₄²⁻ - H₂S = 25 – 30‰) seems to indicate the bacterial reduction of sulphate ion as one of the processes most significantly influencing the isotopic geochemistry of sulphur.     

火电机组负荷响应优化软件的应用

近年来,各大电网对火电机组的要求越来越严格,变负荷调节速度越快,机组性能就越好,电网评估出的性能综合指标Kp就越高。介绍了负荷响应优化软件（URO）的基本原理和实施方式,URO通过过程建模和运用模型预测控制明显的改善了机组负荷跟踪特性,在提升火电机组调节速度的同时,也兼顾了机组的稳定运行,使得锅炉和汽轮机有良好的协调,电网AGC性能综合指标Kp的改善,最终为发电机组带来了的经济收益。     

Economic analysis of solar energy development in North Africa

The economic analysis of solar energy development is the basis of promoting the solar energy planning in north Africa and realizing the clean energy power transmission among continents. In this paper, the cost development trend of photovoltaic(PV) power and concentrating solar power(CSP) generation is analyzed, and the levelized cost of energy (LCOE) of solar power generation is forecasted. Then, taking the development of Tunisian solar energy as an example in the context of transcontinental transmission, PV power with energy storage and PV-CSP power generation are given as two kinds of development plan respectively. The installed capacity configurations of the two schemes are given with production simulation method, and comprehensive LCOE are calculated. The studies show that based on the LCOE forecast value, the LCOE of PV-CSP combined power generation will decrease when the annual utilization hours of transmission channel is increased. It can be chosen as one of important mode of the North Africa solar energy development.     

化学补水方式对火电厂热经济性的影响

在火力发电厂实际运行中,必须经常向热力系统补充化学水。常见的补水方式有2种:化学水通过凝汽器进入系统;化学水从除氧器进入系统。文中以国产某N25-35的热力系统为例,通过等效焓降法分析2种不同的补水方式对电厂热经济性的影响。理论计算结果表明:补水从凝汽器进入热力系统比从除氧器进入系统具有更好的节能效益,其热效率提高了0.16223%,煤耗下降了0.796g/kWh,1年可节省标准煤149.25t。     

On the outlook for solar thermal hydrogen production in South Africa

Global warming and tightening environmental legislation is putting pressure on divesting from fossil fuel in the energy sector, with the transport sector likely to see the biggest changes. Current alternative energy sources are electric vehicles and hydrogen. Conventional hydrogen production technologies are fossil fuel based, emitting significant amounts of CO₂ into the atmosphere. This paper explores various ways to integrate solar thermal technologies into hydrogen production to generate carbon free hydrogen in South Africa. South Africa's abundant solar resource indicates that the country may become a significant player in the hydrogen market. However, the high capital cost associated with solar thermal energy put solar thermal hydrogen at a price disadvantage against conventional production technologies. Significant market penetration for solar thermal hydrogen is not expected within the next decade, but cost reduction due to improved manufacturing techniques and larger manufacturing volumes might close the gap in the long term.     

Multidimensional flow,thermal, and chemical behavior in solid-oxide fuel cell button cells

The quantitative analysis and interpretation of button-cell experiments usually depends upon assuming isothermal conditions together with uniform and known gas composition within the gas compartments. An objective of the present effort is to develop computational tools to study the validity of such assumptions. A three-dimensional computational fluid dynamics (CFD) model is developed and applied to a particular SOFC button cell, characterizing the fluid flow, chemistry, and thermal transport. Results show that when inlet flow rates are sufficiently high, button-cell data can be interpreted using the commonly used assumptions. However, when flow rates are not sufficient, the assumptions of uniform composition can be significantly violated. Additionally, depending on operating conditions there can be significant temperature variations within the gas compartments and the membrane–electrode assembly.     

Development modes analysis of renewable energy power generation in North Africa

North African countries generally have strategic demands for energy transformation and sustainable development. Renewable energy development is important to achieve this goal. Considering three typical types of renewable energies— wind, photovoltaic (PV), and concentrating solar power (CSP)—an optimal planning model is established to minimize construction costs and power curtailment losses. The levelized cost of electricity is used as an index for assessing economic feasibility. In this study, wind and PV, wind / PV / CSP, and transnational interconnection modes are designed for Morocco, Egypt, and Tunisia. The installed capacities of renewable energy power generation are planned through the time sequence production simulation method for each country. The results show that renewable energy combined with power generation, including the CSP mode, can improve reliability of the power supply and reduce the power curtailment rate. The transnational interconnection mode can help realize mutual benefits of renewable energy power, while the apportionment of electricity prices and trading mechanisms are very important and are related to economic feasibility; thus, this mode is important for the future development of renewable energy in North Africa.