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.     

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.     

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.     

Hydrometallurgical separation of rare earth elements, cobalt and nickel from spent nickel-metal-hydride batteries

The separation of rare earth elements, cobalt and nickel from NiMH battery residues is evaluated in this paper. Analysis of the internal content of the NiMH batteries shows that nickel is the main metal present in the residue (around 50% in weight), as well as potassium (2.2-10.9%), cobalt (5.1-5.5%), rare earth elements (15.3-29.0%) and cadmium (2.8%). The presence of cadmium reveals that some Ni-Cd batteries are possibly labeled as NiMH ones. The leaching of nickel and cobalt from the NiMH battery powder with sulfuric acid is efficient; operating variables temperature and concentration of H₂O₂ has no significant effect for the conditions studied. A mixture of rare earth elements is separated by precipitation with NaOH. Finally, solvent extraction with D2EHPA (di-2-ethylhexyl phosphoric acid) followed by Cyanex 272 (bis-2,4,4-trimethylpentyl phosphinic acid) can separate cadmium, cobalt and nickel from the leach liquor. The effect of the main operating variables of both leaching and solvent extraction steps are discussed aiming to maximize metal separation for recycling purposes.     

Simulation of thermal stresses in anode-supported solid oxide fuel cell stacks. Part II: Loss of gas-tightness, electrical contact and thermal buckling

Structural stability issues in planar solid oxide fuel cells arise from the mismatch between the coefficients of thermal expansion of the components. The stress state at operating temperature is the superposition of several contributions, which differ depending on the component. First, the cells accumulate residual stresses due to the sintering phase during the manufacturing process. Further, the load applied during assembly of the stack to ensure electric contact and flatten the cells prevents a completely stress-free expansion of each component during the heat-up. Finally, thermal gradients cause additional stresses in operation.The temperature profile generated by a thermo-electrochemical model implemented in an equation-oriented process modelling tool (gPROMS) was imported into finite-element software (ABAQUS) to calculate the distribution of stress and contact pressure on all components of a standard solid oxide fuel cell repeat unit.The different layers of the cell in exception of the cathode, i.e. anode, electrolyte and compensating layer were considered in the analysis to account for the cell curvature. Both steady-state and dynamic simulations were performed, with an emphasis on the cycling of the electrical load. The study includes two different types of cell, operation under both thermal partial oxidation and internal steam-methane reforming and two different initial thicknesses of the air and fuel compressive sealing gaskets.The results generated by the models are presented in two papers: Part I focuses on cell cracking. In the present paper, Part II, the occurrences of loss of gas-tightness in the compressive gaskets and/or electrical contact in the gas diffusion layer were identified. In addition, the dependence on temperature of both coefficients of thermal expansion and Young's modulus of the metallic interconnect (MIC) were implemented in the finite-element model to compute the plastic deformation, while the possibilities of thermal buckling were analysed in a dedicated and separate model.The value of the minimum stable thickness of the MIC is large, even though significantly affected by the operating conditions. This phenomenon prevents any unconsidered decrease of the thickness to reduce the thermal inertia of the stack. Thermal gradients and the shape of the temperature profile during operation induce significant decreases of the contact pressure on the gaskets near the fuel manifold, at the inlet or outlet, depending on the flow configuration. On the contrary, the electrical contact was ensured independently of the operating point and history, even though plastic strain developed in the gas diffusion layer.     

The role of foreign cations in enhancing the oxygen solubility properties of alkali molten carbonate systems: Brief survey of existing data and new research results

This work presents a summary of experimental data on the oxygen solubility-speciation properties of alkali molten carbonates that have been obtained by the authors through the development of a highly sensitive analysis method. The purpose of this summary is to show in particular the effect of foreign cation additions on both oxygen solubility and dissolution mechanisms at 650 °C. Our findings may be used to clearly indicate that rare earth and magnesium cations are the most effective in enabling oxygen solubility and basicity/oxidizing melt properties. The second part of this work reports new experimental results concerning the effect of simultaneous additions of La and Mg cations to an eutectic Li/Na carbonate system. A dramatic increase in oxygen solubility and active peroxide oxygen species has been found, thus revealing a strong synergistic effect of rare earth and alkaline earth cations on the molten carbonate oxygen chemistry. The results of this investigation suggest therefore that foreign cation addition is a potentially attractive option to design alkali molten carbonate salts with a high oxidizing power.     

Vapour/liquid fractionation of rare earths,Y, Na,K, NH4, Cl,HCO3, SO4 and borate in fluids from the Piancastagnaio geothermal field,Italy

Vapour/liquid fractionation of rare earth elements and yttrium (REY), Na⁺, K⁺, NH₄⁺, HCO₃⁻, SO₄²⁻, Cl⁻ and borate in geothermal fluids from the Piancastagnaio geothermal field (Mt. Amiata geothermal area, Tuscany, central Italy) were evaluated based on the chemistry of collected liquids and condensed vapours. Apparent vapour–liquid partitioning factors (^appD^V/L) of REY vary from 0.3 to 0.01. These factors are much higher than those of Na (<0.001) and K (∼0.001). Volatile components are ion pairings such as NH₄HCO₃^o, NH₄Cl^o, NaHCO₃^o, CaSO₄^o and REYO(HCO)₃^o ⇔ REY(OH)CO₃^o. In vapour, REY and NH₄⁺ are negatively correlated. High and low ^appD^V/L(REY) indicate variations of NH₄⁺ concentrations in liquids. The results of this study are relevant to the understanding of element migration and deposition under hydrothermal boiling conditions.     

Continuous flow solar thermal pasteurization of drinking water: Methods,devices, microbiology,and analysis

The ability to simply and robustly pasteurize drinking water would present tremendous worldwide human health benefits. Ingestion of unsafe drinking water is a leading cause of sickness and death in the developing world. A simple method to use concentrated solar power is presented here with two complimentary numerical models. The first model allows a prediction of water temperatures within the concentrator and enables a user to vary operating parameters to assess the impact on the temperatures. The second model relates the temperatures to pathogen inactivation kinetics so that predictions of pathogen populations can be made. It is found that with a modest size system that includes a parabolic trough concentrator, a thermally activated valve, and a fluid-to-fluid heat exchanger, near complete pathogen inactivation can be achieved. Comparisons are made between simulated and experimentally determined temperatures. The comparison demonstrates the veracity of the model.     

A practical perspective on plant preservation and plant life extension in thermal power stations. Considering aspects of reliability, maintainability, cost and safety

Currently I am employed as the Assistant Power Station Manager, with responsibility for all maintenance aspects, in a thermal power station which has been on standby since 1986! Previously I have been employed as a maintenance engineer and engineering manager in base loading thermal power stations where plant life extension programmes have not only been conceived and planned, but, on most occasions, even completed.

This paper reflects on aspects of plant preservation and plant life extension programmes with which I have been, and am currently, associated; weighing the obvious desirability for such programmes against the need to achieve reliability and maintainability, at a reasonable cost. (Who knows, it may even answer the question continually asked by my wife, “If you are not generating electricity, what do you do all day?”).

The paper also looks at the retention of safety standards, and the need to improve safety standards on ageing plant, in line with ever more stringent legislation.     

Feasibility study for the installation of HVAC for a spa by means of energy recovery from thermal water—Part II: Energy analysis

The use of a low temperature geothermal spring together with the heat energy still contained in waste water from the different therapy systems installed in a spa (shower, jets, bathrooms, jacuzzis, pools, ventilation processes) can significantly reduce the operating and maintenance costs of the installation. This covers part of the air conditioning needs of the building and of the heating of thermal water to the appropriate temperature for therapeutic use.In the first part of the study, an analysis of the spring's situation was made, calculating the thermal water needs and presenting the consumption according to the operation schedule on different types of day. In this way, the contribution the spring was capable of giving was compared and the evolution of the thermal water in the tanks was studied. In the second part, the climatic conditions that the spa should meet are studied, along with the loads that it should support, the energy reclaimed from the different heat focuses and the repercussions on the final solution.     

The benefit of dividing an indirect thermal storage into two compartments: Discharge experiments

Experiments are presented to demonstrate the benefits of dividing an indirect thermal storage into two compartments. The transient discharge experiments were conducted in an undivided and equally divided 126 l rectangular storage vessel, which has a height to depth aspect ratio of 9.3:1 and is inclined at 30° to the horizontal. A 240-tube copper heat exchanger with a total surface area of 2.38 m² was immersed in the storage fluid. For the divided storage, the heat exchanger flow path was in series through the two compartments. Water flow rate through the heat exchanger was varied from 0.05 to 0.15 kg/s to demonstrate the effect of varying the number of transfer units (NTU) from 2.2 to 7 on the relative performance of undivided and divided storage vessels. Reported measurements include transient storage temperature distribution, heat exchanger outlet temperature, delivered energy, and exergy of the divided and undivided storage. The divided storage provides higher energy delivery rates and higher heat exchanger outlet temperatures during most of the discharge. The magnitude of these benefits depends on NTU and the extent of discharge. For a flow rate of 0.05 kg/s, corresponding to a nominal NTU of 7, the divided storage delivers a maximum of 11% more energy than the undivided storage when 100 l of hot water or 55% of the stored energy has been delivered. For a flow rate of 0.15 kg/s, corresponding to a nominal NTU of 2.5, the divided storage delivers a maximum of 5% more energy at the same level of discharge. Data agree with first and second law analyses of a storage system comprised of two tanks in series.     

Fuel poverty, thermal comfort and occupancy: results of a national household-survey in Ireland

Fuel poverty is perhaps the strongest adverse social impact resulting from the inefficient consumption of energy in the domestic sector. Despite considerable research examining the plight of those affected, there has been very little empirical work examining the relationship between fuel poverty and thermal comfort and the extent of indoor cold strain resulting from inadequately heated housing. Furthermore, the effects of fuel poverty on household occupancy have not been addressed formerly. This paper employs a new national household survey of Ireland—a country with a level of fuel poverty similar to Britain—to examine these key issues. Both self-reported and objective measures of thermal comfort are utilised, and the study pays particular attention to the age profile of those affected by thermal discomfort. The results show, inter alia, that two-thirds of fuel-poor householders demonstrate cold strain, and over half of elderly households endure inadequate ambient household temperatures during winter.     

A model of steam reforming of iso-octane: The effect of thermal boundary conditions on hydrogen production and reactor temperature

Steam reforming of iso-octane in a monolithic type reactor was simulated by a three-dimensional computational fluid dynamics model. The variations of hydrogen production and reactor temperature along the length of the reactor were calculated at isothermal, adiabatic and constant heat flux conditions. The reaction rate expressions based on steam reforming of methane in the Langmuir-Hinshelwood format were used to model steam reforming of iso-octane. The difference between the simulated results and experimental data on hydrogen produced was less than 18%. The results indicated that a large drop in temperature was in the first one-tenth of the reactor under adiabatic conditions with inlet temperatures of 600–900 °C. To achieve the same mole fraction of hydrogen (0.27, dry basis) at the exit of the reactor, the maximum temperature difference across the reactor was much smaller at certain heat flux conditions than that at adiabatic conditions. Further, rate of hydrogen production may be evenly distributed in the reactor under certain conditions of constant heat flux.     

The summer thermal behaviour of “skin” materials for vertical surfaces in Athens, Greece as a decisive parameter for their selection

This paper analyses the thermal behaviour of the materials, which are widely used on the vertical surfaces of Greek cities. This analysis is based on surface temperatures measurements, which were carried out both in situ in various buildings of Athens, Greece and experimentally on samples of building materials exposed to solar radiation on a building’s flat roof. The study includes surfacing materials, which are usually applied on building facades around Greece.The study leads to a number of conclusions concerning the effect of colour and orientation on the summer surface temperatures of materials, used on vertical city surfaces. These conclusions indicate how surfacing materials should be chosen in order to help mitigate the urban heat island and improve thermal comfort conditions in the outdoor spaces of Greek cities during the overheated summer period.     

Mixed layered Ni–Mn–Co hydroxides: Crystal structure,electronic state of ions,and thermal decomposition

It has been shown that varying conditions of co-precipitation processes, two types of mixed Ni–Mn–Co hydroxides: either brucite, or hydrotalcite-like (LDHs)—with different Ni/Mn/Co ratio can be prepared. According to XPS study, these hydroxides are mixed-valence materials: Ni ions present in 2+ oxidation state, whereas Mn and Co ions are in 3+/4+ and 2+/3+ state, respectively; their oxidation state increases with an increase of their content in hydroxides. For Ni-rich hydroxides, a strong effect of nickel segregation is observed indicating that chemistry of the surface and of the bulk is different. Mixed Ni–Mn–Co hydroxides decompose in two steps resulting in formation of NiO bunsenite and (Ni,Co,Mn)₃O₄ spinel.     

Modeling, design and thermal performance of a BIPV/T system thermally coupled with a ventilated concrete slab in a low energy solar house: Part 1, BIPV/T system and house energy concept

This paper is the first of two papers that describe the modeling, design, and performance assessment based on monitored data of a building-integrated photovoltaic-thermal (BIPV/T) system thermally coupled with a ventilated concrete slab (VCS) in a prefabricated, two-storey detached, low energy solar house. This house, with a design goal of near net-zero annual energy consumption, was constructed in 2007 in Eastman, Québec, Canada - a cold climate area. Several novel solar technologies are integrated into the house and with passive solar design to reach this goal. An air-based open-loop BIPV/T system produces electricity and collects heat simultaneously. Building-integrated thermal mass is utilized both in passive and active forms. Distributed thermal mass in the direct gain area and relatively large south facing triple-glazed windows (about 9% of floor area) are employed to collect and store passive solar gains. An active thermal energy storage system (TES) stores part of the collected thermal energy from the BIPV/T system, thus reducing the energy consumption of the house ground source heat pump heating system. This paper focuses on the BIPV/T system and the integrated energy concept of the house. Monitored data indicate that the BIPV/T system has a typical efficiency of about 20% for thermal energy collection, and the annual space heating energy consumption of the house is about 5% of the national average. A thermal model of the BIPV/T system suitable for preliminary design and control of the airflow is developed and verified with monitored data.     

The ignition,combustion and flame structure of carbon monoxide/hydrogen mixtures. Note 2: Fluid dynamics and kinetic aspects of syngas combustion

The kinetic characterization of the H₂/CO system in presence of nitrogen components was systematically revised in the first note of this work [Frassoldati A, Faravelli T, Ranzi E. The ignition, combustion and flame structure of carbon monoxide/hydrogen mixtures. Note 1: detailed kinetic modeling of syngas combustion also in presence of nitrogen compounds. Int J Hydrogen Energy; 2007, in press]. This second note analyses three different turbulent non-premixed syngas flames by using different approaches such as the Eddy dissipation (ED) the Eddy dissipation concept (EDC) and steady laminar flamelets (SLF) model.