Periodic Reporting for period 1 - REACHER (Reactive fluids for intensified thermal energy conversion)
Reporting period: 2022-04-01 to 2024-09-30
Thermodynamic cycles constitute the backbone structure of fossil-fuelled and renewable thermal power systems, refrigerators and heat pumps. In thermodynamic cycles, input energies are converted into output useful energy forms (work or heat) by means of an energy carrier, an inert working fluid, which undertakes cycles of thermodynamic transformations. Power cycles have been dominating global electricity production, and it is expected that refrigerators and heat pumps will represent one of the future major electricity consumers. Improvements of their backbone-thermodynamic structure thus play a crucial role in achieving energy-policy objectives addressing climate change and reducing air pollution, such as the increase of the efficiency of energy use and the deployment of renewable technologies.
To increase the performance of thermodynamic cycles, researches mainly focus on improving their unit operations, optimizing the networking of these components, and optimal selection of a working fluid crossing the whole cycle. Among these possible measures, the choice of the optimal working fluid represents the core of the process of adaptation of conventional fossil-fueled thermal engine configurations to exploit lower-grade renewable and waste heat sources and the primary action to reduce the environmental impact of heat pumps.
Nowadays, only inert working fluids (pure fluids or mixtures) are currently employed. However, despite their optimal selection, the thermal efficiency of these energy conversion systems remains far from the maximum achievable ones, dictated by the Carnot limit.
REACHER proposes to revive an idea which was introduced by Lighthill in the 1950s', which consists in using -instead of INERT working fluids- working fluids being the site of a REVERSIBLE CHEMICAL REACTION. Practically, this means that along each thermodynamic transformation occurring in each unit operation forming the cycle, a chemical reaction evolves, driven by the modification of temperature and/or pressure, and according to chemical equilibrium.
REACHER aims to deepen this unexplored concept and, specifically: to search/design suitable reactive working fluids for different applications (power cycles and heat pumps) and to characterize the thermochemical and thermophysical properties of these fluids; to propose an optimized architecture for the considered thermodynamic cycles; and to validate the impact of using reactive working fluids in a micro power plant.
The expected impact is a groundbreaking increase of the efficiency of these energy systems and/or reduction of their size.
To increase the performance of thermodynamic cycles, researches mainly focus on improving their unit operations, optimizing the networking of these components, and optimal selection of a working fluid crossing the whole cycle. Among these possible measures, the choice of the optimal working fluid represents the core of the process of adaptation of conventional fossil-fueled thermal engine configurations to exploit lower-grade renewable and waste heat sources and the primary action to reduce the environmental impact of heat pumps.
Nowadays, only inert working fluids (pure fluids or mixtures) are currently employed. However, despite their optimal selection, the thermal efficiency of these energy conversion systems remains far from the maximum achievable ones, dictated by the Carnot limit.
REACHER proposes to revive an idea which was introduced by Lighthill in the 1950s', which consists in using -instead of INERT working fluids- working fluids being the site of a REVERSIBLE CHEMICAL REACTION. Practically, this means that along each thermodynamic transformation occurring in each unit operation forming the cycle, a chemical reaction evolves, driven by the modification of temperature and/or pressure, and according to chemical equilibrium.
REACHER aims to deepen this unexplored concept and, specifically: to search/design suitable reactive working fluids for different applications (power cycles and heat pumps) and to characterize the thermochemical and thermophysical properties of these fluids; to propose an optimized architecture for the considered thermodynamic cycles; and to validate the impact of using reactive working fluids in a micro power plant.
The expected impact is a groundbreaking increase of the efficiency of these energy systems and/or reduction of their size.
The project is organized in three main parts:
Part 1. Development of a software enabling the determination of the thermodynamic properties (phase equilibrium and energetic properties) of reactive mixtures in their equilibrium state.
In this part, the first research achievement is the understanding of the thermodynamic behaviour of reactive binary mixtures presenting one reversible chemical reaction, and thus the defined algorithms and models to calculate their thermodynamic properties. The software which has been developped is coded in Fortran language and its development represents the second research achievement of the project. In its current development status, the software allows the calculation of the properties of reactive working fluids being the site of one reversible dissociation chemical reaction, with stoichiometry A2⇄2A (for example, N2O4=2NO2 and carboxylic acids), including or not an inert molecule.
Part 2. Establishment of a list of “suitable” reactive fluids, consisting in: (i) designing new, or searching existing, suitable chemical reactions; (ii) characterizing their thermodynamics and their kinetics; (iii) determining their environmental and safety properties. The current development status of parts (i)-(ii) is summarised below:
(i) The molecular design of new chemical reactions characterised by the general stoichiometry A2=2A is completed: about 150 reactions, involving the breakage/formation of a covalent bond, have been designed and their reactants and products assessed as stable. A software has been developped to enable the reaction design. Also, the research of existing suitable reactions has led to the discovery of suitable classes of dimerization reactions involving the breakage/formation of a hydrogen bond. These two classes of reactive fluids are a priori suitable for power, heating and cooling applications and have been patented.
(ii) We have developed a multi-scale approach, in order to predict the inputs required by REACHprop software. This achievement has been validated on the well-known system N2O4=2NO2 and published. The kinetics of all the reactions has been preliminary assessed for all the designed molecules.
Part 3. Validation on a micro-power plant of the expected impact of using reactive fluids.
The design of the power plant is completed and the acquisition of all the main components is also completed. At the moment, we are also using the Raman spectrometer acquired in the project in order to assess the variation of the composition of some reactive fluids with different temperatures, in a second experimental apparatus. The next steps consist in assembling the pilot, setting up its control system, and testing it.
Part 1. Development of a software enabling the determination of the thermodynamic properties (phase equilibrium and energetic properties) of reactive mixtures in their equilibrium state.
In this part, the first research achievement is the understanding of the thermodynamic behaviour of reactive binary mixtures presenting one reversible chemical reaction, and thus the defined algorithms and models to calculate their thermodynamic properties. The software which has been developped is coded in Fortran language and its development represents the second research achievement of the project. In its current development status, the software allows the calculation of the properties of reactive working fluids being the site of one reversible dissociation chemical reaction, with stoichiometry A2⇄2A (for example, N2O4=2NO2 and carboxylic acids), including or not an inert molecule.
Part 2. Establishment of a list of “suitable” reactive fluids, consisting in: (i) designing new, or searching existing, suitable chemical reactions; (ii) characterizing their thermodynamics and their kinetics; (iii) determining their environmental and safety properties. The current development status of parts (i)-(ii) is summarised below:
(i) The molecular design of new chemical reactions characterised by the general stoichiometry A2=2A is completed: about 150 reactions, involving the breakage/formation of a covalent bond, have been designed and their reactants and products assessed as stable. A software has been developped to enable the reaction design. Also, the research of existing suitable reactions has led to the discovery of suitable classes of dimerization reactions involving the breakage/formation of a hydrogen bond. These two classes of reactive fluids are a priori suitable for power, heating and cooling applications and have been patented.
(ii) We have developed a multi-scale approach, in order to predict the inputs required by REACHprop software. This achievement has been validated on the well-known system N2O4=2NO2 and published. The kinetics of all the reactions has been preliminary assessed for all the designed molecules.
Part 3. Validation on a micro-power plant of the expected impact of using reactive fluids.
The design of the power plant is completed and the acquisition of all the main components is also completed. At the moment, we are also using the Raman spectrometer acquired in the project in order to assess the variation of the composition of some reactive fluids with different temperatures, in a second experimental apparatus. The next steps consist in assembling the pilot, setting up its control system, and testing it.
Among the mentioned achievements, the following ones are the scientific and technological breakthroughs, which allow the advancement beyond the state of the art.
1) Residential and industrial heat pump applications. According to preliminary results, the coefficient of performance of vapour compression heat pumps operating with reactive working fluids can potentially achieve extremely high values: about the 70% of the maximum achievable one (Carnot efficiency) versus the 40% of the maximum achievable one with inert fluids (the state of the art).
2) Industrial heat pump applications. We have theoretically proven that the compression in the vapour phase of a reactive fluid leads the reaction to evolve towards the endothermic direction, thus limiting the heating of the fluid during compression. The breakthrough lies in this reactive cooling effect within the compressor, which enables to increase by more than 100°C the heat sink temperature of the heat pump always guaranteeing a sufficient margin from the thermal stability limit of the working fluid. Such a positive outcome (and application to high temperature heat pumps) was not expected.
3) Desing of reactive working fluids. Almost 150 reactions have been designed, preliminary characterised and patented for their further exploitation. The assessment of the suitability of each of these fluids is part of the work which is under development.
4) Predictive determination of force field parameters. Monte Carlo simulations require, as an input, force field parameters. According to the state of the art, those are optimised over experimental data and it is thus not possible to determine these parameters for new (designed) fluids, because no data is available. A procedure has been designed, coupling Quantum Mechanics, Monte Carlo and Machine Learning, to predict force field parameters.
5) A new approach to the thermodynamic analysis of reactive fluids. The approach we propose has proven the excellent accuracy in modelling the thermodynamic properties of reactive fluids in which the reaction involves either a covalent or hydrogen bond formation/breakage.
1) Residential and industrial heat pump applications. According to preliminary results, the coefficient of performance of vapour compression heat pumps operating with reactive working fluids can potentially achieve extremely high values: about the 70% of the maximum achievable one (Carnot efficiency) versus the 40% of the maximum achievable one with inert fluids (the state of the art).
2) Industrial heat pump applications. We have theoretically proven that the compression in the vapour phase of a reactive fluid leads the reaction to evolve towards the endothermic direction, thus limiting the heating of the fluid during compression. The breakthrough lies in this reactive cooling effect within the compressor, which enables to increase by more than 100°C the heat sink temperature of the heat pump always guaranteeing a sufficient margin from the thermal stability limit of the working fluid. Such a positive outcome (and application to high temperature heat pumps) was not expected.
3) Desing of reactive working fluids. Almost 150 reactions have been designed, preliminary characterised and patented for their further exploitation. The assessment of the suitability of each of these fluids is part of the work which is under development.
4) Predictive determination of force field parameters. Monte Carlo simulations require, as an input, force field parameters. According to the state of the art, those are optimised over experimental data and it is thus not possible to determine these parameters for new (designed) fluids, because no data is available. A procedure has been designed, coupling Quantum Mechanics, Monte Carlo and Machine Learning, to predict force field parameters.
5) A new approach to the thermodynamic analysis of reactive fluids. The approach we propose has proven the excellent accuracy in modelling the thermodynamic properties of reactive fluids in which the reaction involves either a covalent or hydrogen bond formation/breakage.