Search results for "exergy efficiency"
showing 10 items of 13 documents
Exergetic and exergoeconomic analysis of a novel hybrid solar-geothermal polygeneration system producing energy and water
2016
Abstract A dynamic simulation model of a novel solar–geothermal polygeneration system and the related exergetic and exergoeconomic analyses are presented in this paper. The plant is designed in order to supply electrical, thermal and cooling energy and fresh water for a small community, connected to a district heating and cooling network. The hybrid system is equipped with an Organic Rankine Cycle fueled by medium-enthalpy geothermal energy and by a Parabolic Trough Collector solar field. Geothermal brine is also used for space heating and cooling purposes. Finally, geothermal fluid supplies heat to a Multi-Effect Distillation unit, producing also desalinized water from seawater. Dynamic si…
Towards the first proof of the concept of a Reverse ElectroDialysis - Membrane Distillation Heat Engine
2019
Abstract The coupling of Reverse Electrodialysis with Membrane Distillation is a promising option for the conversion of waste heat into electricity. This study evaluates the performances of the integrated system under different operating conditions, employing validated model and correlations. This work provides a detailed description of the behaviour of a real RED-MD heat engine and indicates the set of inlet concentrations, velocities and equipment size which returns the highest cycle exergy efficiency. These operating conditions were selected for the pilot plant developed within the EU-funded project RED Heat to Power. For the first time, a perspective analysis was also included, consider…
Thermoeconomic optimization of a renewable polygeneration system serving a small isolated community
2015
During the last years, special attention has been paid to renewable polygeneration technologies, able of simultaneously producing thermal, cooling, electrical energy and desalinated water from seawater. This paper focuses on an innovative polygeneration system driven by renewable energy sources, including the following technologies: hybrid photovoltaic/thermal collectors, concentrating parabolic trough (CPVT), a biomass heater, a single-stage absorption chiller and a multiple-effect distillation desalination system. The system is designed to cover the base load of an isolated small community. In previous papers, the dynamic simulation model about plant operation is discussed. In this paper,…
Assessing the Robustness of Thermoeconomic Diagnosis of Fouled Evaporators: Sensitivity Analysis of the Exergetic Performance of Direct Expansion Coi…
2016
Thermoeconomic diagnosis of refrigeration systems is a pioneering approach to the diagnosis of malfunctions, which has been recently proven to achieve good performances for the detection of specific faults. Being an exergy-based diagnostic technique, its performance is influenced by the trends of exergy functions in the “design” and “abnormal” conditions. In this paper the sensitivity of performance of thermoeconomic diagnosis in detecting a fouled direct expansion coil and quantifying the additional consumption it induces is investigated; this fault is critical due to the simultaneous air cooling and dehumidification occurring in the coil, that induce variations in both the chemical and th…
Exergy analysis of reverse electrodialysis
2018
Abstract Reverse electrodialysis in closed loop configurations is a promising membrane technology in the energy conversion and storage fields. One of the main advantages of closed-loop reverse electrodialysis is the possibility of using a wide range of operating concentrations, flow rates and different salts for generating the salinity gradient. In this work, an original exergy analysis of the reverse electrodialysis process was carried out in order to investigate reverse electrodialysis performance in terms of energetic and exergetic efficiency parameters in a wide range of operating conditions. A mono-dimensional model of the reverse electrodialysis process was developed, in which all sou…
Exergy analysis and thermoeconomic cost accounting of a Combined Heat and Power steam cycle integrated with a Multi Effect Distillation-Thermal Vapou…
2017
Abstract In this paper an exergy analysis and thermoeconomic cost accounting of a Combined Heat and Power steam cycle integrated with Multi Effect Distillation-Thermal Vapour Compression plant is performed; the goal of the study is to show how these methodologies provide a rational criterion to allocate production costs on electricity and freshwater in such a dual purpose system. After a brief overview on the methodology and a description of reference plant, exergy analysis is carried out to calculate exergy flows and exergy efficiencies at component level. A detailed description of the adopted thermoeconomic model is given. In a first scenario, cost accounting is performed assuming that th…
Thermolytic reverse electrodialysis heat engine: model development, integration and performance analysis
2019
Abstract Salinity gradient heat engines represent an innovative and promising way to convert low-grade heat into electricity by employing salinity gradient technology in a closed-loop configuration. Among the aqueous solutions which can be used as working fluid, ammonium bicarbonate-water solutions appear very promising due to their capability to decompose at low temperature. In this work, an experimentally validated model for a reverse electrodialysis heat engine fed with ammonium bicarbonate-water solutions was developed. The model consists of two validated sub-models purposely integrated, one for the reverse electrodialysis unit and the other for the stripping/absorption regeneration uni…
Boosting the performance of a Reverse Electrodialysis – Multi-Effect Distillation Heat Engine by novel solutions and operating conditions
2019
Abstract This work presents a performance analysis of a waste-heat-to-power Reverse Electrodialysis Heat Engine (RED-HE) with a Multi-Effect Distillation (MED) unit as the regeneration stage. The performance of the system is comparatively evaluated using two different salts, sodium chloride and potassium acetate, and investigating the impact of different working solutions concentration and temperature in the RED unit. For both salt solutions, the impact of membrane properties on the system efficiency is analysed by considering reference ionic exchange membranes and high-performing membranes. Detailed mathematical models for the RED and MED units have been used to predict the thermal efficie…
Reverse electrodialysis heat engine with multi-effect distillation: Exergy analysis and perspectives
2019
Abstract 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 is a promising technology with the potential to convert low-grade heat into electric power. The reverse electrodialysis technology has been under investigation in the last years to explore the real potentials for energy generation from natural and artificial solutions, and recent works have been addressing also the potential of its coupling with regeneration strategies, looking at medium and large energy supply purposes. In this work, for the first time, a c…
Regeneration units for thermolytic salts applications in water & power production: State of the art, experimental and modelling assessment
2021
Abstract Thermolytic solutions are often proposed as high salinity or “draw” stream to generate a chemical potential driving force in Salinity Gradient Power (SGP) and Forward Osmosis (FO) technologies. Depleted “draw” solutions exiting the process can be regenerated by a thermal process powered at very-low grade heat, which is able to decompose the salt into gaseous ammonia and carbon dioxide, which can be stripped and then reabsorbed in the draw solution, restoring its initial concentration. In this work, two different experimental prototypes for the regeneration of ammonium bicarbonate aqueous solution were designed, built and tested. The effect of several operating parameters on the reg…