scholarly journals Performance Analysis of a RED-MED Salinity Gradient Heat Engine

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3385 ◽  
Author(s):  
Patricia Palenzuela ◽  
Marina Micari ◽  
Bartolomé Ortega-Delgado ◽  
Francesco Giacalone ◽  
Guillermo Zaragoza ◽  
...  
Keyword(s):  
Performance Analysis ◽  
Power Density ◽  
Waste Heat ◽  
Salinity Gradient ◽  
Heat Engine ◽  
Exergy Efficiency ◽  
Integrated System ◽  
Operating Conditions ◽  
Membrane Properties ◽  
Recovery Ratio

A performance analysis of a salinity gradient heat engine (SGP-HE) is presented for the conversion of low temperature heat into power via a closed-loop Reverse Electrodialysis (RED) coupled with Multi-Effect Distillation (MED). Mathematical models for the RED and MED systems have been purposely developed in order to investigate the performance of both processes and have been then coupled to analyze the efficiency of the overall integrated system. The influence of the main operating conditions (i.e., solutions concentration and velocity) has been quantified, looking at the power density and conversion efficiency of the RED unit, MED Specific Thermal Consumption (STC) and at the overall system exergy efficiency. Results show how the membrane properties (i.e., electrical resistance, permselectivity, water and salt permeability) dramatically affect the performance of the RED process. In particular, the power density achievable using membranes with optimized features (ideal membranes) can be more than three times higher than that obtained with current reference ion exchange membranes. On the other hand, MED STC is strongly influenced by the available waste heat temperature, feed salinity and recovery ratio to be achieved. Lowest values of STC below 25 kWh/m3 can be reached at 100 °C and 27 effects. Increasing the feed salinity also increases the STC, while an increase in the recovery ratio is beneficial for the thermal efficiency of the system. For the integrated system, a more complex influence of operating parameters has been found, leading to the identification of some favorable operating conditions in which exergy efficiency close to 7% (1.4% thermal) can be achieved for the case of current membranes, and up to almost 31% (6.6% thermal) assuming ideal membrane properties.

Optimum Design and Performance Simulation of a Multi-device Integrated System Based on a Proton Exchange Membrane Fuel Cell

2022 ◽  
pp. 1-33
Author(s):  
Xiuqin Zhang ◽  
Wentao Cheng ◽  
Qiubao Lin ◽  
Longquan Wu ◽  
Junyi Wang ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Power Density ◽  
Power Output ◽  
Proton Exchange Membrane ◽  
Waste Heat ◽  
Proton Exchange ◽  
Integrated System ◽  
Interior Space ◽  
And Performance ◽  
Exchange Membrane

Abstract Proton exchange membrane fuel cells (PEMFCs) based on syngas are a promising technology for electric vehicle applications. To increase the fuel conversion efficiency, the low-temperature waste heat from the PEMFC is absorbed by a refrigerator. The absorption refrigerator provides cool air for the interior space of the vehicle. Between finishing the steam reforming reaction and flowing into the fuel cell, the gases release heat continuously. A Brayton engine is introduced to absorb heat and provide a useful power output. A novel thermodynamic model of the integrated system of the PEMFC, refrigerator, and Brayton engine is established. Expressions for the power output and efficiency of the integrated system are derived. The effects of some key parameters are discussed in detail to attain optimum performance of the integrated system. The simulation results show that when the syngas consumption rate is 4.0 × 10−5 mol s−1cm−2, the integrated system operates in an optimum state, and the product of the efficiency and power density reaches a maximum. In this case, the efficiency and power density of the integrated system are 0.28 and 0.96 J s−1 cm−2, respectively, which are 46% higher than those of a PEMFC.

scholarly journals Performance Analysis of a Combined Cycle Power Plant with Simultaneous Cooling of Inlet Air Streams to the Compressor and Condenser

2018 ◽  
Vol 4 (1) ◽  
pp. 2-25
Author(s):  
Ifeanyi Henry Njoku ◽  
Chika Oko ◽  
Joseph Ofodu
Keyword(s):  
Power Plant ◽  
Performance Analysis ◽  
Waste Heat ◽  
Combined Cycle ◽  
Integrated System ◽  
Refrigeration Cycle ◽  
Exergy Destruction ◽  
Combined Cycle Power Plant ◽  
Absorption Refrigerator ◽  
Air Streams

Abstract: This paper presents the thermodynamic performance analysis of an existing combined cycle power plant to be retrofitted with a waste heat driven aqua lithium bromide absorption refrigerator for cooling the inlet air streams to the compressor and air-cooled steam condenser. The power plant is located in the hot and humid tropical region of Nigeria, latitude 4°45′N and longitude 7°00′E. This was achieved by performing energy and exergy analysis of the integrated system. Using the operating data of the existing combined cycle power plant, the results of the analysis showed that by cooling the inlet air streams to 15oC at the compressors, and to 29oC at the air-cooled steam condenser, the net power output, thermal and exergy efficiencies of the combined cycle plant increased by 7.7%, 8.1% and 7.5% respectively while the plant total exergy destruction rate and specific fuel consumption dropped by 10.8% and 7.0% respectively. The stack flue gas exit temperature reduced from 126oC to 84oC in the absorption refrigerator, thus reducing the environmental thermal pollution. The COP and exergy efficiency of the refrigeration cycle was 0.60 and 27.0%, respectively. Results also show that the highest rate of exergy destruction in the combined cycle power plant occurred in the combustion chamber while the highest rate of exergy destruction in the absorption refrigeration cycle occurred in the evaporator followed by the absorber.

scholarly journals Evaluation of the Economic and Environmental Performance of Low-Temperature Heat to Power Conversion using a Reverse Electrodialysis – Multi-Effect Distillation System

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3206 ◽  
Author(s):  
◽  
George Kosmadakis ◽  
Francesco Giacalone ◽  
Bartolomé Ortega-Delgado ◽  
Andrea Cipollina ◽  
...  
Keyword(s):  
Low Temperature ◽  
Large Scale ◽  
Waste Heat ◽  
Salinity Gradient ◽  
Heat Engine ◽  
Potassium Acetate ◽  
Cost Effective ◽  
Levelized Cost Of Electricity ◽  
Reverse Electrodialysis ◽  
Distillation System

In the examined heat engine, reverse electrodialysis (RED) is used to generate electricity from the salinity difference between two artificial solutions. The salinity gradient is restored through a multi-effect distillation system (MED) powered by low-temperature waste heat at 100 °C. The current work presents the first comprehensive economic and environmental analysis of this advanced concept, when varying the number of MED effects, the system sizing, the salt of the solutions, and other key parameters. The levelized cost of electricity (LCOE) has been calculated, showing that competitive solutions can be reached only when the system is at least medium to large scale. The lowest LCOE, at about 0.03 €/kWh, is achieved using potassium acetate salt and six MED effects while reheating the solutions. A similar analysis has been conducted when using the system in energy storage mode, where the two regenerated solutions are stored in reservoir tanks and the RED is operating for a few hours per day, supplying valuable peak power, resulting in a LCOE just below 0.10 €/kWh. A life-cycle assessment has been also carried out, showing that the case with the lowest environmental impact is the same as the one with the most attractive economic performance. Results indicate that the material manufacturing has the main impact; primarily the metallic parts of the MED. Overall, this study highlights the development efforts required in terms of both membrane performance and cost reduction, in order to make this technology cost effective in the future.

scholarly journals Feasibility of Pressure-Retarded Osmosis for Electricity Generation at Low Temperatures

Membranes ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 556
Author(s):  
Elham Abbasi-Garravand ◽  
Catherine N. Mulligan
Keyword(s):  
Power Density ◽  
Membrane Fouling ◽  
Low Temperatures ◽  
Sea Water ◽  
Salinity Gradient ◽  
Operating Conditions ◽  
Pressure Retarded Osmosis ◽  
Water Transportation ◽  
Gradient Energy ◽  
Temperature Impact

A membrane-based technique for production of pressure-retarded osmosis (PRO) is salinity gradient energy. This sustainable energy is formed by combining salt and fresh waters. The membrane of the PRO process has a significant effect on controlling the salinity gradient energy or osmotic energy generation. Membrane fouling and operating conditions such as temperature have an extreme influence on the efficiency of the PRO processes because of their roles in salt and water transportation through the PRO membranes. In this study, the temperature impact on the power density and the fouling of two industrial semi-permeable membranes in the PRO system was investigated using river and synthetic sea water. Based on the findings, the power densities were 17.1 and 14.2 W/m2 at 5 °C for flat sheet and hollow fiber membranes, respectively. This is the first time that research indicates that power density at low temperature is feasible for generating electricity using PRO processes. These results can be promising for regions with high PRO potential that experience low temperatures most of the year.

Analysis and Assessment of Tower Solar Collector Driven Trigeneration System

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Abdul Khaliq ◽  
Mathkar A. Alharthi ◽  
Saeed Alqaed ◽  
Esmail M. A. Mokheimer ◽  
Rajesh Kumar
Keyword(s):  
Energy Efficiency ◽  
Solar Collector ◽  
Lithium Bromide ◽  
Rankine Cycle ◽  
Significant Rise ◽  
Exergy Efficiency ◽  
Integrated System ◽  
Operating Conditions ◽  
Heating And Cooling ◽  
And Performance

Abstract This paper describes the development and performance assessment of a tower solar collector driven integrated system operating in trigeneration mode to generate electricity, heating, and cooling, in a carbon-free manner. The proposed system applies a heliostat-based central receiver unit as a base of solar energy input to drive the steam Rankine cycle which is combined with the process heater and the lithium bromide-water operated absorption chiller. An analysis is performed to monitor the behavior of energy and exergy efficiency at various operating conditions of the proposed trigeneration system. The computed results are authenticated with the reported literature. A comparison is made between the present findings and reported results in the form of exergy efficiency, total exergy destroyed, and energy efficiency. Consideration of process heat and cold along with electricity provides a promising increase in energy efficiency from 15.8% to 64.1% while the exergy efficiency is enhanced from 16.9% to 24.4%. Variation in direct normal irradiations from 600 W/m2 to 1000 W/m2 results in the significant rise of energetic and exergetic outcomes of the proposed trigeneration system. Out of 100% solar exergy supplied to the proposed trigeneration, 24% is generated as the exergetic output, 1.6% is lost to ambient, and the remaining 74.4% is the exergy destroyed in the system components.

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