The Experts below are selected from a list of 62733 Experts worldwide ranked by ideXlab platform
George Papadakis - One of the best experts on this subject based on the ideXlab platform.
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a novel autonomous pv powered desalination system based on a dc microgrid concept incorporating short term Energy storage
Solar Energy, 2018Co-Authors: Christosspyridon Karavas, K G Arvanitis, George Kyriakarakos, Dimitrios D Piromalis, George PapadakisAbstract:Abstract Seawater reverse osmosis (SWRO) desalination units coupled with renewable Energy technologies such as photovoltaics are a very appealing suggestion, especially in remote areas, such as islands and coastal regions, which often face lack or low quality fresh water coupled with electrical Energy shortages. This paper regards an experimental investigation of a PV powered small-scale SWRO desalination system which employs Hydraulic Energy recovery, based on a DC microgrid concept and incorporates a short term electric Energy storage in the form of hybrid capacitors and a short term Hydraulic Energy storage in the form of pressure vessels. Α multi-agent decentralized Energy management system which relies on intelligent agents and employs Fuzzy Cognitive Maps for its implementation, allowing for efficient operation of the desalination system under variable conditions (variable feed pressure), was developed and implemented. The experimental results show that it is feasible to operate efficiently such PV powered SWRO system. Furthermore, the desalination unit produces potable water during daytime even at periods when the produced Energy from the PV array is not sufficient to operate the desalination unit. Moreover, the SWRO system shows a continuous and smooth operation, meaning small feed water pressure variations at sharp rapid solar irradiation intensity variations due to the incorporated short-term storage. In addition, the intelligently managed PV powered SWRO system with short term storage produces considerably more fresh water, especially at days with variable solar irradiation, as compared to the same SWRO system directly PV driven without storage and any control.
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an experimental comparative study of the technical and economic performance of a small reverse osmosis desalination system equipped with an Hydraulic Energy recovery unit
Desalination, 2006Co-Authors: Essam Sh Mohamed, Emmanouil Mathioulakis, George Papadakis, V BelessiotisAbstract:Abstract An experimental study is presented of a small-scale conventional seawater reverse osmosis (SWRO) system with potable water production of 1.7 m3/d, and the modifications made to this system by installing an Hydraulic Energy recovery unit and completely changing the pumps. The measured specific Energy consumption of the proposed system was experimentally found to be 3.3 kWh/m3, which is a very promising value compared to the value of 20 kWh/m3 of the conventional system. Lowering the specific Energy consumption results in the reduction of the total system's installed power, which achieves lower permeate production costs. The aim of the modifications was to test, investigate and construct a SWRO system equipped with an Hydraulic Energy recovery unit operating under variable conditions of pressure and flow to meet the variable power supply systems for future connection with renewable Energy technologies such as photovoltaics and wind turbines. The only electrical load of the system is a brushless DC motor of 510 W maximum power, coupled directly to a positive displacement rotary vane pump with a flow rate of 900 L/h. The expected permeate production cost (excluding the Energy production system cost) was calculated to be 3.68 €/m3, while the reported cost of transported water to some of the Greek Islands is 7 €/m3.
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the effect of Hydraulic Energy recovery in a small sea water reverse osmosis desalination system experimental and economical evaluation
Desalination, 2005Co-Authors: Essam Sh Mohamed, Emmanouil Mathioulakis, George Papadakis, V ElessiotisAbstract:This paper presents the experimental results of a small Sea Water Reverse Osmosis desalination system equipped with a Hydraulic Energy recovery unit of the Eco systems Clark pump type. The system is installed at the Agricultural University of Athens, and has been in continuous operation since January 2004. The system has a maximum fresh water production of 2.6 m3/day, with an average quality of 250 μS/cm, using two spiral wound SWRO membranes connected in series. The feed water is a NaCl solution with an Electrical Conductivity of 35 mS/cm, typically isoosmotic with the sea water. The only electrical consumption of this system is a brushless DC motor directly coupled to a feed water rotary vane pump. This motor is powered from a small battery bank of 310 Ah. The measured specific Energy consumption reached up to 3 kWh/m3, while other small sea water reverse osmosis systems without Energy recovery reported specific Energy consumption as high as 10–20 kWh/m3. The measured low Energy consumption of the present system makes it suitable for future coupling with renewable Energy systems such as photovoltaics and wind generators.
Essam Sh Mohamed - One of the best experts on this subject based on the ideXlab platform.
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an experimental comparative study of the technical and economic performance of a small reverse osmosis desalination system equipped with an Hydraulic Energy recovery unit
Desalination, 2006Co-Authors: Essam Sh Mohamed, Emmanouil Mathioulakis, George Papadakis, V BelessiotisAbstract:Abstract An experimental study is presented of a small-scale conventional seawater reverse osmosis (SWRO) system with potable water production of 1.7 m3/d, and the modifications made to this system by installing an Hydraulic Energy recovery unit and completely changing the pumps. The measured specific Energy consumption of the proposed system was experimentally found to be 3.3 kWh/m3, which is a very promising value compared to the value of 20 kWh/m3 of the conventional system. Lowering the specific Energy consumption results in the reduction of the total system's installed power, which achieves lower permeate production costs. The aim of the modifications was to test, investigate and construct a SWRO system equipped with an Hydraulic Energy recovery unit operating under variable conditions of pressure and flow to meet the variable power supply systems for future connection with renewable Energy technologies such as photovoltaics and wind turbines. The only electrical load of the system is a brushless DC motor of 510 W maximum power, coupled directly to a positive displacement rotary vane pump with a flow rate of 900 L/h. The expected permeate production cost (excluding the Energy production system cost) was calculated to be 3.68 €/m3, while the reported cost of transported water to some of the Greek Islands is 7 €/m3.
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the effect of Hydraulic Energy recovery in a small sea water reverse osmosis desalination system experimental and economical evaluation
Desalination, 2005Co-Authors: Essam Sh Mohamed, Emmanouil Mathioulakis, George Papadakis, V ElessiotisAbstract:This paper presents the experimental results of a small Sea Water Reverse Osmosis desalination system equipped with a Hydraulic Energy recovery unit of the Eco systems Clark pump type. The system is installed at the Agricultural University of Athens, and has been in continuous operation since January 2004. The system has a maximum fresh water production of 2.6 m3/day, with an average quality of 250 μS/cm, using two spiral wound SWRO membranes connected in series. The feed water is a NaCl solution with an Electrical Conductivity of 35 mS/cm, typically isoosmotic with the sea water. The only electrical consumption of this system is a brushless DC motor directly coupled to a feed water rotary vane pump. This motor is powered from a small battery bank of 310 Ah. The measured specific Energy consumption reached up to 3 kWh/m3, while other small sea water reverse osmosis systems without Energy recovery reported specific Energy consumption as high as 10–20 kWh/m3. The measured low Energy consumption of the present system makes it suitable for future coupling with renewable Energy systems such as photovoltaics and wind generators.
James D. Van De Ven - One of the best experts on this subject based on the ideXlab platform.
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constant pressure Hydraulic Energy storage through a variable area piston Hydraulic accumulator
Applied Energy, 2013Co-Authors: James D. Van De VenAbstract:Hydraulic accumulators are used in a variety of applications to minimize the pressure variation in Hydraulic circuits and to store Energy. Conventional Hydraulic accumulators suffer from two major limitations, the Hydraulic system pressure varies with the quantity of Energy stored and the Energy density is significantly lower than other Energy domains. In this paper, a novel Hydraulic accumulator is presented that uses a piston with an area that varies with stroke to maintain a constant Hydraulic system pressure while the gas pressure changes. The variable area piston is sealed with a fabric reinforced rolling diaphragm. In this work, the piston radius profile is developed as a function of the piston displacement and then transformed into a function of the axial contact location between the piston and the diaphragm. The piston profile was solved numerically for a variety of conditions using both transformation methods to illustrate the geometric design trade-offs. Using a variable area gas piston with a fixed cylinder area, the maximum gas volume ratio was 1.8:1. An analysis of the Energy density revealed that the constant pressure accumulator provides a 16% improvement in Energy density over a conventional accumulator at a volume ratio of 2.71:1 and also exceeds the maximum Energy density of a conventional accumulator at the lower volume ratio of 1.8:1. This new promising technology maintains a constant Hydraulic system pressure independent of the quantity of Energy stored, easing system control and allowing other circuit components to be downsized to meet the same power requirements, while also increases the Energy storage density.
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Open accumulator concept for compact fluid power Energy storage
ASME International Mechanical Engineering Congress and Exposition Proceedings (IMECE), 2007Co-Authors: Perry Y. Li, James D. Van De Ven, Caleb SanckenAbstract:Copyright © 2007 by ASME. Energy storage devices for fluid power applications that are significantly more compact than existing ones will enable Energy regeneration for many applications, including fluid power hybrid vehicles and construction equipment. The current approach to Hydraulic Energy storage makes use of a compressed gas enclosed in a closed chamber. As the system must contain the expanded gas and the Hydraulic oil displaced, the optimal Energy density occurs at a modest expansion ratio resulting in a small Energy density. By allowing intake and exhaust of compressed and expanded air from and to the atmosphere, a potential order of magnitude increase in Energy density is available in the new open accumulator approach. Potential methods for realizing the new configuration are described. Analysis and simulation case studies illustrate both the advantages and challenges of the new approach.
Hans-peter Harjes - One of the best experts on this subject based on the ideXlab platform.
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a model for fluid injection induced seismicity at the ktb germany
Geophysical Journal International, 2003Co-Authors: Stefan Baisch, Hans-peter HarjesAbstract:SUMMARY The 9.1 km deep KTB (Kontinentale Tiefbohrung, Germany) drilling hole is one of the best investigated deep-drilling sites in the world. Among other parameters, in situ measurements revealed continuous profiles of principal stresses, pore fluid pressure and fracture geometry in the vicinity of the borehole. The present study combines these parameters with Hydraulic and seismicity data obtained during fluid-injection experiments conducted at the KTB to derive a conceptual model for fluid-injection-induced seismicity at the KTB. This model rests on the well constrained assumptions that (1) the crust is highly fractured with a permeable fracture network between 9 km depth and the Earth's surface and (2) the crust is in near-failure equilibrium, whereby a large number of fracture planes are under near-critical condition. During the injection experiment, the elevated pore fluid pressure remained well below the least principal stress and thus was too small to cause Hydraulic opening of existing fractures. Consequently, the geometry of the fracture network was assumed to have not changed during fluid injection with induced seismicity occurring solely as a result of lowering of the effective normal stress, consistent with observed source mechanisms. The key parameter in the present model is the fracture permeability, which exhibits large spatial and directional variations. These variations are proposed to primarily control fluid migration paths and associated propagation of elevated fluid pressure during fluid injection. In contrast with common models based on isotropic fluid diffusion or spatially averaged permeability, highly permeable branches of the fracture network strongly affect the propagation of fluid pressure and prohibit the concept of a smooth ‘pressure front’. We find evidence that major fluid flow exists at comparatively low fluid pressure (below the critical pressure required to cause seismic failure) without being detected seismically. This might also explain the difference between 1011 J of Hydraulic Energy inserted into the system during fluid injection and ∼108 J of seismic Energy: a major part of the Hydraulic Energy might be converted to potential Energy of the ground water level caused by upward migrating fluid. From the fluid level response to changes of injection rate observed in a second borehole we estimate fluid signal velocities to be as large as 300 m d−1. Importantly, the suggested model also accounts for the occurrence of repeating earthquakes (multiplets), a large number of which were observed during the injection experiment. The present model also suggests that coseismic changes of the stress field caused by tectonic shear stress release are very local and of small magnitude. This is consistent with the observation that none of the larger induced events is followed by aftershock series that would be expected if coseismic processes had noticeably perturbed the local stress field.
Feng Guo - One of the best experts on this subject based on the ideXlab platform.
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an experimental study of the Hydraulic free piston engine
Applied Energy, 2012Co-Authors: Zhenfeng Zhao, Fujun Zhang, Ying Huang, Changlu Zhao, Feng GuoAbstract:A prototype of Hydraulic free piston engine has been developed to achieve efficient Energy conversion directly from chemical Energy of fuel to Hydraulic Energy. In stable running condition, in order to verify the features of this kind of engine, the piston dynamics, combustion process and Hydraulic characteristics are investigated through series of tests of the prototype. The experimental results show that the majority of fuel burns in the rapid combustion phase which is due to the high piston velocity in the final part of the compression stroke. The combustion is characterized by a constant volume process. Furthermore, the indicated thermal efficiency and the indicated mean effective pressure of the prototype presented in this study are 41% and 5.2bar respectively.
