CO2 Absorption Power Cycle for Low-Temperature Heat Recovery
Solution Overview
Problem
Current methods for converting low temperature heat to electricity and cooling are inefficient due to high energy losses and inability to concurrently produce electricity, heat, and cold using low value heat sources like solar, geothermal, and industrial waste heat.
Innovation Solution
The Carbon Carrier Cycle (C3) optimizes energy conversion by using a carbon dioxide chemical absorption process for pressure reduction downstream of the turbine, achieving efficient entropy reduction and maximizing delta temperature, allowing for the production of electricity, heat, and cold from low temperature heat sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current methods (Rankine cycle, Organic Rankine cycle, Kalina cycle, Trilateral flash cycle) are used to convert low temperature heat to electricity, then electricity generation is possible even at temperatures as low as 60°C, but the conversion efficiency is very low and economically unattractive
Solution Approach 1:
The patent changes the working fluid from conventional organic fluids to CO2, and modifies the cycle parameters by introducing a gas absorption section where CO2 is absorbed by solvents at low pressure and temperature, then desorbed at higher pressure and temperature. This parameter change enables efficient operation at low temperature heat sources while achieving much higher conversion efficiency compared to conventional cycles.
Solution Approach 2:
The patent introduces a gas absorption intermediary system using solvents (such as amines) that temporarily store CO2 at low pressure and release it at high pressure. This intermediary mechanism allows the system to bridge the low temperature heat source with the high pressure requirements for efficient electricity generation, overcoming the efficiency limitations of direct expansion cycles.
2Loss of energy
If the entropy reduction on the cold side is minimized and delta T in gas expansion is increased, then practical conversion efficiency can be largely increased, but this requires more efficient entropy reduction mechanisms and larger temperature differences
Solution Approach 1:
The patent utilizes phase transitions of CO2 (gas absorption and desorption) as the core mechanism for entropy reduction. The CO2 is absorbed by the solvent in liquid phase at low pressure, then desorbed as gas at high pressure through heating. This phase transition approach provides efficient entropy reduction while maintaining relatively simple device structure compared to conventional multi-component systems.
3Loss of energy
If chemicals are used to enhance the liquefaction of gases downstream of the turbine for pressure reduction, then the cycle efficiency can be improved, but an amount of energy corresponding to the formation enthalpy of the chemical complex is released and must be removed and provided again upstream
Solution Approach 1:
The patent creates a continuous cycle where the energy released during CO2 absorption by the solvent is captured and reused to drive the desorption process upstream. The solvent is continuously circulated between the absorption section (downstream of turbine) and the desorption section (upstream of turbine), maintaining continuous useful action and minimizing net energy input required for chemical complex formation and decomposition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The C3 system achieves up to 300% more electricity generation compared to current low temperature conversion technologies, with low energy losses and cost-effective operation, enabling efficient conversion of heat sources between -78°C and 150°C.
Implementation Method 1
a carbon dioxide chemical absorption process for pressure reduction downstream of the turbine
Implementation Method 2
The expanded and cooled working gas is then fed to an expansion machine that produces electricity and cooling
Implementation Method 3
The reactor system is energetically coupled to the thermal energy source for receipt of energy for heating the mixture
Data Source
AI summary
A method for producing electrical energy is disclosed which uses a heat source, such as solar heat, geothermal heat, industrial waste heat or heat from power production processes, providing heat of 150° C. or below, further comprising an absorber system in which a working gas, primarily carbon dioxide CO2, is absorbed into an absorbent, typically an amine, further comprising a reactor which receives heat from said heat source and in which the absorbent-CO2 mixture is split into CO2 and absorbent, further comprising an expansion machine, an electricity generator and auxiliary equipment such as pumps, pipes and heat exchangers. The system according to the method allows the cost-efficient production of electrical energy and cooling using low value heat source.