An oxygen isotope study of silicates in the larderello geothermal field, Italy

Stable-isotope analyses were carried out on hydrothermal minerals sampled from the deep metamorphic units at Larderello, Italy. The ∂¹⁸O values obtained for the most retentive minerals, quartz and tourmaline, are from + 12.0‰ to + 14.7‰ and 9.9‰, respectively, and indicate deposition from an ¹⁸O-rich fluid. Calculated ∂¹⁸O values for these fluids range from + 5.3‰ to + 13.4‰. These values, combined with available fluid inclusion and petrographic data, are consistent with the proposed existence of an early thermal fluid of probable magmatic origin and a late meteoric water. Mixing between these two fluids occurred locally.     

Features of low-temperature oxidation of hydrogen in the medium of nitrogen,carbon dioxide,and water vapor at elevated pressures

The article discusses novel research results on combustion features of high-density Н₂/О₂ mixtures (ρ_H2 = 0.70–1.89 mol/dm³, ρ_O2 = 0.32–0.81 mol/dm³) diluted with nitrogen, carbon dioxide, or water vapor (from 46 to 76% mol.) at the uniform heating (1 K/min) of tubular reactor. Based on time dependencies of temperature increment in the reaction mixtures caused by the heat release during oxidation of H₂, it is found that the self-ignition temperature of Н₂/О₂/N₂ and Н₂/О₂/H₂O mixtures is by ≈ 30 K lower than that of the Н₂/О₂/СО₂ mixture. Unlike combustion of H₂ in the N₂ medium, in the CO₂ and H₂O media a chain-thermal explosion is observed at a certain concentration of reagents. The influencing mechanisms of diluents on the H₂ oxidation dynamics, as well as the contribution of homogeneous and heterogeneous reactions in the heat release are revealed. It is established that high heat capacity of H₂/O₂/CO₂ mixture, chemical interaction between its components, and presence of CO₂ molecules adsorbed on the reactor inner surface, are the factors determining the H₂ oxidation dynamics in CO₂ medium. At oxidation of H₂ in the H₂O medium, the process takes place against the background of water evaporation and, as a consequence, is characterized by increased heat capacity and thermal conductivity of the H₂/O₂/H₂O reaction mixture.     

The Tianjin geothermal field (north-eastern China): Water chemistry and possible reservoir permeability reduction phenomena

Injection of spent (cooled) thermal fluids began in the Tianjin geothermal district, north-eastern China, at the end of the 1990s. Well injectivities declined after 3–4 years because of self-sealing processes that reduced reservoir permeability. The study focuses on the factors that may have caused the observed decrease in permeability, using chemical and isotopic data on fluids (water and gas) and mineral phases collected from production and injection wells. The results of data processing and interpretation indicate that (1) it is very unlikely that calcite and silica precipitation is taking place in the reservoir; (2) the Fe- and Zn-rich mineral phases (e.g. sulfides, hydroxides and silicates) show positive saturation indexes; (3) SEM and XRD analyses of filtered material reveal that the latter mineral phases are common; (4) visual observation of casings and surface installations, and of corrosion products, suggests that a poor quality steel was used in their manufacture; (5) significant quantities of solids (e.g. quartz and feldspar crystals) are carried by the geothermal fluid; (6) seasonal changes in fluid composition lead to a reduction in casing corrosion during the summer.     

Assessing innovation in emerging energy technologies: Socio-technical dynamics of carbon capture and storage (CCS) and enhanced geothermal systems (EGS) in the USA

This study applies a socio-technical systems perspective to explore innovation dynamics of two emerging energy technologies with potential to reduce greenhouse gas emissions from electrical power generation in the United States: carbon capture and storage (CCS) and enhanced geothermal systems (EGS). The goal of the study is to inform sustainability science theory and energy policy deliberations by examining how social and political dynamics are shaping the struggle for resources by these two emerging, not-yet-widely commercializable socio-technical systems. This characterization of socio-technical dynamics of CCS and EGS innovation includes examining the perceived technical, environmental, and financial risks and benefits of each system, as well as the discourses and actor networks through which the competition for resources – particularly public resources – is being waged. CCS and EGS were selected for the study because they vary considerably with respect to their social, technical, and environmental implications and risks, are unproven at scale and uncertain with respect to cost, feasibility, and life-cycle environmental impacts. By assessing the two technologies in parallel, the study highlights important social and political dimensions of energy technology innovation in order to inform theory and suggest new approaches to policy analysis.     

Application of fluid inclusions to the study of Bagnore geothermal field (Tuscany, Italy)

A fluid inclusion study of the hydrothermal minerals in two breccias from two wells in the Bagnore geothermal field (Italy) has provided information on the evolution of the fluids, and has also demonstrated that fluid inclusions can be utilized as geothermometers in this geothermal field. Both breccias come from reservoir zones: one (Bagnore 3bis (Bg 3bis)) was cored at a depth of 3111 m below ground level (b.g.l.), whereas the other (Bagnore 22 (Bg 22)) was ejected during a blow-out, probably from a fractured zone present between 2200 and 2300 m b.g.l. The hydrothermal cement of the breccias is mostly made up of quartz, K-feldspar, Na-rich plagioclase, calcite, chlorite and illite. Fluid inclusion studies were carried out on quartz (Bg 3bis and Bg 22 breccias) and adularia (Bg 22 breccia). Three types of fluid inclusions were recognized in the Bg 3bis breccia. Type I (liquid-rich) inclusions trapped an aqueous fluid with a CO₂ concentration (1.7–2.7 mol/kg) that is significantly higher than present-day fluids (0.5 mol/kg). Type II (liquid-rich) inclusions formed after type I, and trapped a fluid with less CO₂ (0.6–1.0 mol/kg). Type III (vapor-rich) coexist with type I inclusions, and record an early fluid circulation under boiling conditions. The decrease of the CO₂ (and total gas) concentrations from type I inclusions to type II inclusions, and on to present-day conditions can be related to boiling with gas loss and/or mixing. Only one type of fluid inclusion (type II), with moderate CO₂ concentration (0.7–0.3 mol/kg), was found in the Bg 22 breccia. Boiling and/or mixing explain the variation of the CO₂ content in the Bg 22 reservoir fluid from inclusion formation to modern CO₂ concentration (0.3 mol/kg). The absence of any type I inclusions in Bg 22 breccia may be related to non-uniform CO₂ concentrations in different parts of the field. Present-day temperatures (295±10 °C for Bg 3bis and 320±10 °C for Bg 22) are close or equal to fluid inclusion average total homogenization temperatures (around 290 °C for Bg 3bis and 320 °C for Bg 22), suggesting that fluid inclusions can be useful for estimating local temperatures when direct measurements are not available or dubious.     

The effect of trade between China and the UK on national and global carbon dioxide emissions

We estimate the amount of carbon dioxide embodied in bi-lateral trade between the UK and China in 2004. Developing and applying the method of Shui and Harriss [2006. The role of CO₂ embodiment in US–China trade. Energy Policy 34, 4063–4068], the most recently available data on trade and CO₂ emissions have been updated and adjusted to calculate the CO₂ emissions embodied in the commodities traded between China and the UK. It was found that through trade with China, the UK reduced its CO₂ emissions by approximately 11% in 2004, compared with a non-trade scenario in which the same type and volume of goods are produced in the UK. In addition, due to the greater carbon-intensity and relatively less efficient production processes of Chinese industry, China–UK trade resulted in an additional 117 Mt of CO₂ to global CO₂ emissions in the same one year period, compared with a non-trade scenario in which the same type and volume of goods are produced in the UK. This represents an additional 19% to the reported national CO₂ emissions of the UK (555 Mt/y in 2004) and 0.4% of global emissions. These findings suggest that, through international trade, very significant environmental impacts can be shifted from one country to another, and that international trade can (but does not necessarily) result in globally increased greenhouse gas emissions. These results are additional to the environmental consequences of transporting goods, which are not robustly quantified here.     

Partitioning of rare earths and some major elements in the Kizildere geothermal field, Turkey

Rare earth elements and yttrium (REY), Na⁺, K⁺, Cl⁻, and Ca²⁺ were determined in water, steam, mineral scale and rock samples from the Kizildere geothermal field, Turkey. The CO₂-rich parent fluid originates from a sequence of mica schists with marble intercalations. The chemistry of the parent fluid varies with location and time. The average REY composition of the fluids is derived by extrapolation to the lowest Ca concentrations. The apparent vapor–liquid partitioning factors for REY at 145 °C and 5 bar total absolute pressure are about 0.2, whereas for Ca²⁺, Na⁺, K⁺ and Cl⁻ they are <0.05, about 0.0005, 0.0005 and about 0.02, respectively. Apparent scale-liquid distribution coefficients for REY at 145 and 190 °C are about 0.15 and 0.55, whereas at 100 °C they increase from 0.3 (La) to 1.5 (Lu).     

Temperature and chemical changes in the fluids of the Obama geothermal field (SW Japan) in response to field utilization

Thermal waters from Quaternary volcanic rocks (predominantly andesites) discharge along faults in the Obama geothermal field of southwestern Japan. The chemistry of more than 100 thermal and ground water samples collected between 1936 and 2005 indicate that the Na–Cl hot spring waters are a mixture of “andesitic” magmatic, sea and meteoric waters. Mixing models and silica and cation geothermometry were used to estimate the SiO₂ and Cl composition and the temperature (∼200 °C) of the reservoir fluids deep in the geothermal system. The isotopic data (¹⁸O and D) are consistent with a mixed origin interpretation of the waters feeding the Obama hot springs, i.e. a large proportion of meteoric and sea waters, and a small magmatic component. Temperatures and chemical concentrations of the thermal waters were affected by the 1944–1959 salt production operations, but have recovered after closure of the salt factories; now they are similar to their pre-1940 values. In the future, the Obama geothermal field may be suitable for electric power generation, although heat and fluid extraction will require careful management to prevent or minimize reservoir cooling.     

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.     

The potential for electricity conservation and carbon dioxide emission reductions in the household sector of Brazil

Pressure is mounting in large Non-Annex 1 countries like Brazil, China, and India to accept binding commitments to reduce their greenhouse gas emissions in the second, post-2012, commitment period. In the case of Brazil, pressure is higher for the country to commit itself to reduce its emissions from land use changes but, because of the country’s recent high economic growth rates, very soon, this pressure will also turn to reducing its greenhouse gas emissions from electricity production and use in the various sectors of the economy. This paper summarizes the methodological approach, and the results, of a study aimed at assessing the potential for electricity conservation and carbon dioxide emissions reductions in the Brazilian household sector. The study splits the household sector into 20 subsectors, considering five different geographical regions and four household electricity consumption levels (a proxy for different household income levels). Technical, economic, and market potentials are determined for electricity conservation in these 20 subsectors for the period 2005–2030, and results are also translated into carbon dioxide emission reductions using the Clean Development Mechanism (CDM) combined margin (build margin plus operating margin) approach for determining the emission’s factor for the power grids. Results show significant electricity and carbon dioxide reduction potentials at negative costs for both household final consumers (market potential) and the economy as a whole (economic potential) in the residential sector of Brazil.

Simultaneous direct visualisation of liquid water in the cathode and anode serpentine flow channels of proton exchange membrane (PEM) fuel cells

Water flooding is detrimental to the performance of the proton exchange membrane fuel cell (PEMFC) and therefore it has to be addressed. To better understand how liquid water affects the fuel cell performance, direct visualisation of liquid water in the flow channels of a transparent PEMFC is performed under different operating conditions. Two high-resolution digital cameras were simultaneously used for recording and capturing the images at the anode and cathode flow channels. A new parameter extracted from the captured images, namely the wetted bend ratio, has been introduced as an indicator of the amount of liquid water present at the flow channel. This parameter, along with another previously used parameter (wetted area ratio), has been used to explain the variation in the fuel cell performance as the operating conditions of flow rates, operating pressure and relative humidity change. The results have shown that, except for hydrogen flow rate, the wetted bend ratio strongly linked to the operating condition of the fuel cell; namely: the wetted bend ratio was found to increase with decreasing air flow rate, increasing operating pressure and increasing relative humidity. Also, the status of liquid water at the anode was found to be similar to that at the cathode for most of the cases and therefore the water dynamics at the anode side can also be used to explain the relationships between the fuel cell performance and the investigated operating conditions.