Search results for " Gradient"
showing 10 items of 575 documents
Modelling Reverse Electrodialysis process via Exergy Analysis
2017
Salinity Gradient Power Heat Engines (SGP-HEs) represent a novel technology to convert low grade waste heat into electricity. Reverse Electrodialysis Heat Engine (REDHE) is one of the possible application of this concept, where a common RED unit is coupled with a thermal regeneration unit supplied with waste heat to restore the salinity gradient of the streams to be fed back to the RED unit. In a RED unit, anion and cation exchange membranes (AEMs and CEMs) are alternatively stacked and interposed between salt solutions at different concentration generating an electric potential difference over each membrane along with a selective transport of cations and anions from the concentrated soluti…
Exergy Analysis of Reverse Electrodialysis Heat Engine with Multi-Effect Distillation Regeneration Stage
2018
The increasing worldwide energy demand is rising the interest on alternative power production technologies based on renewable and emission-free energy sources. In this regard, the closed-loop reverse electrodialysis heat engine (RED-HE) is one of the most promising technologies currently under investigation. This technology produces electric power by harvesting the salinity gradient energy released from the controlled mixing of two artificial salt solutions with different concentrations. Low-grade heat (T < 100 °C), derived from any industrial process is used in a multi-effect distillation (MED) unit to restore the initial salinity gradient of the solutions. In this work, a comprehensive…
Lab-scale experiments on a novel acid/base electrodialytic flow battery with bipolar membranes
2021
Electrical energy storage has a key role in the development and diffusion of renewable energy technologies. The Acid/Base Flow Battery is an innovative process to store electrical energy in the form of pH and salinity gradients via electrodialytic reversible techniques based on the use of bipolar membranes. During the charge phase, the unit produces acid and alkaline solutions by applying an electric field, during the discharge phase, converts the pH gradient into electrical energy. In this work, several experimental tests were performed in a 10×10 cm2 laboratory-scale unit fed with HCl, NaOH and NaCl solutions, in order to characterize the battery and assess its performance. The effect of …
Performance of a RED system with ammonium hydrogen carbonate solutions
2016
The use of closed-loop salinity gradient power (SGP) technologies has been recently presented as a viable option to generate power using low-grade heat, by coupling a SGP unit with a thermally-driven regeneration process in a closed loop where artificial solutions can be adopted for the conversion of heat into power. Among these, the closed-loop reverse electrodialysis (RED) process presents a number of advantages such as the direct production of electricity, the extreme flexibility in operating conditions and the recently demonstrated large potentials for industrial scale-up. Ammonium hydrogen carbonate (NH4HCO3) is a salt suitable for such closed-loop RED process thanks to its particular …
REAPOWER – USE OF DESALINATION BRINE FOR POWER PRODUCTION THROUGH REVERSE ELECTRODIALYSIS
2015
Salinity gradient power (SGP) represents a viable renewable energy source associated with the mixing of two solutions of different salinities. Reverse electrodialysis (SGP-RE or RED) is a promising technology to exploit this energy source and directly generate electricity. However, although the principle of this technology is well known since several years, further R&D efforts are still necessary in order to explore the real potential of the SGP-RE process. With this regard, the aim of the REAPower project ( [GRAPHICS] ) is the development of an innovative system for power production by SGP-RE process, using sea (or brackish) water as a diluted solution and brine as a concentrate. The use o…
Reverse Electrodialysis Process: Analysis of Optimal Conditions for Process Scale-up
2014
Reverse Electrodialysis (SGP-RE or RED) process has been widely accepted as a viable and promising technology to produce electric energy from salinity difference (i.e salinity gradient power - e.g. using river water/seawater, or seawater and concentrated brines). Recent R&D efforts demonstrated how an appropriate design of the SGP-RE unit and a suitable selection of process conditions may crucially enhance the process performance. With this regard, a process simulator was developed and validated with experimental data collected on a lab-scale unit, providing a new modelling tool for process optimisation. In this work, performed within the REAPower project (www.reapower.eu), the process simu…
Reverse electrodialysis with NH4HCO3-water systems for heat-to-power conversion
2017
Abstract A Reverse ElectroDialysis Heat Engine (REDHE) system operating with “thermolytic” ammonium hydrogen-carbonate (NH4HCO3) aqueous solutions as working fluids is studied. The engine is constituted by (i) a RED unit to produce electric power by mixing the solutions at different salinity and (ii) a thermally-driven regeneration unit including a stripping and an absorption column to restore the initial salinity gradient thus closing the cycle. In the present work only the RED unit and the stripping column are taken into account. In particular, a simplified integrated process model for the whole cycle was developed: it consists of (i) a lumped parameter model for the RED unit validated wi…
Bipolar membrane reverse electrodialysis for the sustainable recovery of energy from pH gradients of industrial wastewater: Performance prediction by…
2021
Abstract The theoretical energy density extractable from acidic and alkaline solutions is higher than 20 kWh m−3 of single solution when mixing 1 M concentrated streams. Therefore, acidic and alkaline industrial wastewater have a huge potential for the recovery of energy. To this purpose, bipolar membrane reverse electrodialysis (BMRED) is an interesting, yet poorly studied technology for the conversion of the mixing entropy of solutions at different pH into electricity. Although it shows promising performance, only few works have been presented in the literature so far, and no comprehensive models have been developed yet. This work presents a mathematical multi-scale model based on a semi-…
CFD prediction of scalar transport in thin channels for reverse electrodialysis
2014
Reverse ElectroDialysis (RED) is a very promising technology allowing the electrochemical potential difference of a salinity gradient to be directly converted into electric energy. The fluid dynamics optimization of the thin channels used in RED is still an open problem. The present preliminary work focuses on the Computational Fluid Dynamics (CFD) simulation of the flow and concentration fields in these channels. In particular three different configurations were investigated: a channel unprovided with a spacer (empty channel) and two channels filled with spacers, one made of overlapped filaments the other of woven filaments. The transport of two passive scalars, representative of the ions …
Reverse Electrodialysis: Applications to Different Case Studies
2018
Salinity gradient is a non-conventional renewable energy form which is widely available worldwide. Reverse Electrodialysis is a promising and innovative technology able to convert directly this chemical renewable energy into electricity. This paper presents a number of different scenarios where salinity gradients are naturally available or they result from industrial/urban activities. A sophisticated model accounting for all the main phenomena (including all the detrimental ones) occurring within a Reverse Electrodialysis unit has been purposely developed. The model is used to calculate how much electric energy can be harvested from the above-mentioned salinity gradients.