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Veerman J.,Center of Excellence for Sustainable Water Technology | Veerman J.,Agora Inc | Saakes M.,Center of Excellence for Sustainable Water Technology | Metz S.J.,Center of Excellence for Sustainable Water Technology | Harmsen G.J.,University of Groningen
Chemical Engineering Journal | Year: 2011

Reverse electrodialysis (RED) is a technology to generate electricity using the entropy of the mixing of sea and river water. A model is made of the RED process and validated experimentally. The model is used to design and optimize the RED process. It predicts very small differences between counter- and co-current operation. It was decided to focus on co-current design because co-current operation causes smaller local pressure differences between the river and seawater compartments-hence smaller risk of leakages and the possibility to use very thin membranes with high fluxes and very open spacer structures with low hydrodynamic resistance. Segmentation of the electrodes proved to increase the power density by about 15% under realistic operational conditions. The model shows that with smaller systems - in terms of length of the flow path - higher power densities are possible. This effect is rather dramatical and poses a challenge for designing improved RED stacks on large commercial scale. It is suggested to reduce the flow path length by applying a fractal structure design of the spacers. Such structures can be made by profiling the membrane. © 2010 Elsevier B.V. Source


Frank S.,Colorado School of Mines | Steponavice I.,Agora Inc | Rebennack S.,Colorado School of Mines
Energy Systems | Year: 2012

Over the past half-century, Optimal Power Flow (OPF) has become one of the most important and widely studied nonlinear optimization problems. In general, OPF seeks to optimize the operation of electric power generation, transmission, and distribution networks subject to system constraints and control limits. Within this framework, however, there is an extremely wide variety of OPF formulations and solution methods. Moreover, the nature of OPF continues to evolve due to modern electricity markets and renewable resource integration. In this two-part survey, we survey both the classical and recent OPF literature in order to provide a sound context for the state of the art in OPF formulation and solution methods. The survey contributes a comprehensive discussion of specific optimization techniques that have been applied to OPF, with an emphasis on the advantages, disadvantages, and computational characteristics of each. Part I of the survey provides an introduction and surveys the deterministic optimization methods that have been applied to OPF. Part II of the survey (this article) examines the recent trend towards stochastic, or non-deterministic, search techniques and hybrid methods for OPF. © Springer-Verlag 2012. Source


Veerman J.,Center of Excellence for Sustainable Water Technology | Veerman J.,Agora Inc | Saakes M.,Center of Excellence for Sustainable Water Technology | Metz S.J.,Center of Excellence for Sustainable Water Technology | Harmsen G.J.,University of Groningen
Environmental Science and Technology | Year: 2010

Electricity can be produced directly with reverse electrodialysis (RED) from the reversible mixing of two solutions of different salinity, for example, sea and river water. The literature published so far on RED was based on experiments with relatively small stacks with cell dimensions less than 10 × 10 cm 2. For the implementation of the RED technique, it is necessary to know the challenges associated with a larger system. In the present study we show the performance of a scaled-up RED stack, equipped with 50 cells, each measuring 25 × 75 cm 2. A single cell consists of an AEM (anion exchange membrane) and a CEM (cation exchange membrane) and therefore, the total active membrane area in the stack is 18.75 m 2. This is the largest dimension of a reverse electrodialysis stack published so far. By comparing the performance of this stack with a small stack (10 × 10 cm 2, 50 cells) it was found that the key performance parameter to maximal power density is the hydrodynamic design of the stack. The power densities of the different stacks depend on the residence time of the fluids in the stack. For the large stack this was negatively affected by the increased hydrodynamic losses due to the longer flow path. It was also found that the large stack generated more power when the sea and river water were flowing in co-current operation. Co-current flow has other advantages, the local pressure differences between sea and river water compartments are low, hence preventing leakage around the internal manifolds and through pinholes in the membranes. Low pressure differences also enable the use of very thin membranes (with low electrical resistance) as well as very open spacers (with low hydrodynamic losses) in the future. Moreover, we showed that the use of segmented electrodes increase the power output by 11%. © 2010 American Chemical Society. Source


Trademark
Agora Inc | Date: 2016-05-02

COSMETIC PREPARATIONS FOR SKIN RENEWAL; NON-MEDICATED SKIN CARE PREPARATIONS; NON-MEDICATED SKIN CARE CREAMS AND LOTIONS.


Trademark
Agora Inc | Date: 2016-05-02

COSMETIC PREPARATIONS FOR SKIN RENEWAL; NON-MEDICATED SKIN CARE PREPARATIONS; NON-MEDICATED SKIN CARE CREAMS AND LOTIONS; BODY SCRUBS.

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