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Abstract. This study presents the development of tools for the sustainable thermal management of a shallow unconsolidated urban groundwater body in the city of Basel (Switzerland). The concept of the investigations is based on (1) a characterization of the present thermal state of the urban groundwater body, and (2) the evaluation of potential mitigation measures for the future thermal management of specific regions within the groundwater body. The investigations focus on thermal processes down-gradient of thermal groundwater use, effects of heated buildings in the subsurface as well as the thermal influence of river–groundwater interaction. Investigation methods include (1) short- and long-term data analysis, (2) high-resolution multilevel groundwater temperature monitoring, as well as (3) 3-D numerical groundwater flow and heat transport modeling and scenario development. The combination of these methods allows for the quantifying of the thermal influences on the investigated urban groundwater body, including the influences of thermal groundwater use and heated subsurface constructions. Subsequently, first implications for management strategies are discussed, including minimizing further groundwater temperature increase, targeting "potential natural" groundwater temperatures for specific aquifer regions and exploiting the thermal potential.

Abstract The optimization of a multi-generation system which represents the integrated dual-purpose desalination plant and a low-scale absorption refrigeration system is addressed. A nonlinear mathematical programming optimization model that integrates a natural gas combined-cycle, a multi-effect distillation desalination plant, a series flow double-effect water-lithium bromide absorption refrigeration system, and a water heater, is developed based on first-principle models. The model is implemented in General Algebraic Modelling System and a generalized gradient-based optimization algorithm is used. Given design specifications for electricity generation (around 37 MW), freshwater production (100 kg/s), refrigeration capacity (2 MW), and thermal load for heating (around 0.7 MW of hot water), the integrated system is optimized by minimizing two objective functions by single-objective optimization: total heat transfer area and total annual cost. As a result, minimum total heat transfer area values of 39148 m2, 36002 m2, and 35161 m2 are obtained when 4, 5, and 6 distillation effects were considered in the multi-effect distillation system, respectively. Also, a minimum annual cost of around 24 MM$/yr. is obtained for 5 distillation effects. The influence of the number of effects in the multi-effect distillation subsystem on the optimal solutions is analyzed. Cost-effective optimal solutions are developed for the studied multi-generation system.

Underground Pumped Storage Hydropower (UPSH) is an alternative to manage the electricity production in flat regions. UPSH plants consist of two reservoirs of which at least one is underground. For this last reservoir, abandoned mines could be considered. UPSH related activities may induce hydrochemical variations, such as the increase of the oxygen (O2) partial pressure (pO2), which may entail negative consequences in terms of environment and efficiency, especially in coal mined areas where the presence of sulfide minerals is common. This work assesses the main expected environmental impacts that UPSH using abandoned coal mines may induce. © 2017 The Authors. Published by Elsevier Ltd. E. Pujades and A. Jurado gratefully acknowledge the financial support from the University of Liège and the EU through the Marie Curie BeIPD-COFUND postdoctoral fellowship programme (2014/16 and 2015/17 fellows from “FP7-MSCA-COFUND, 600405”). This research has been supported by the Public Service of Wallonia – Department of Energy and Sustainable Building. Peer reviewed

AbstractThis paper assesses how parameter uncertainties in the model for rise velocity of CO2 droplets in the ocean cause uncertainties in their rise and dissolution in marine waters. The parameter uncertainties in the rise velocity for both hydrate coated and hydrate free droplets are estimated from experiment data. Thereafter the rise velocity is coupled with a mass transfer model to simulate the fate of dissolution of a single droplet.The assessment shows that parameter uncertainties are highest for large droplets. However, it is also shown that in some circumstances varying the temperature gives significant change in rise distance of droplets.

Energy-Efficient Ammonia Production from Air and Water Using Electrocatalysts with Limited Faradaic Efficiency

Abstract Water management is critical for PEMFCs, especially at system level. To study its impact on the performance and obtain useful indicators for fault detection, two commercial stacks were characterized by impedance spectroscopy under various humidities and current densities. One was fresh while the other was operated on-field during 10 000 h. Four capacitive and one inductive loops are identified. The capacitive loops are attributed to charge transfer kinetics at both anode and cathode and to cathodic and anodic mass transfer limitations. The inductive loop is attributed to oscillations in the ionomer water content induced by oscillations in the amount of produced water during the measurement. The size of the cathodic charge transfer loop and its departure angle at high frequencies increase as humidity decreases because the ionomer conductivity decreases. These parameters are potential indicators of the cathode drying. The angles are below 45° at low humidities but close to 90° in sur-saturated conditions.

In bioleaching processes using autotrophic bacteria, CO2 is the carbon source for the growth of the microorganisms and its availability is dependent on gas mass transfer. The objective of this study was to investigate the demand in CO2 in complex copper concentrate bioleaching operations and to optimize CO2 supply. Batch tests in 2L-stirred reactors at 10%w/v solid load were performed to study the need for CO2-supplementation and to determine the adequate CO2 partial pressure in the gas inlet. The results show that Fe oxidation (and thus microbial activity) is delayed when air is injected without CO2-supplementation. CO2-supplementation improves leaching kinetics since Cu dissolution rate increases from 84 mg/L/h with air solely to 120 mg/L/h when CO2 is added to air. The study proposes also a methodology to determine G/L transfer components and to asses CO2 limitations in the system. It shows that the microorganisms are not only sensitive to the transfer rate of CO2 from the gas to the liquid phase, but also to the availability of CO2 in solution.