VPT Cycle Working Fluid Selection for Low-Temperature Heat
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Solution Overview
Problem
Existing methods for generating electrical energy using low-temperature heat sources, such as geothermal energy, achieve efficiencies of less than 11.5% due to limitations in the Variable Phase Turbine (VPT) cycle, particularly with known working fluids like R134a and R245fa.
Innovation Solution
The use of specific substances like cycloalkanes, alkenes, dienes, alkynes, or ethers with two to six carbon atoms, or halogen-free compounds like 1-chloro-1,2,2,2-tetrafluoroethane, which have a fugacity greater than 17 bar in the liquid phase at 115°C, as working media in the VPT cycle, enhancing efficiency by increasing the pressure and phase flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If known working fluids like R134a and R245fa are used in the VPT cycle, then the system can operate with low-temperature heat sources, but the electrical energy generation efficiency is limited to less than 11.5%
Solution Approach 1:
The patent changes the physical-chemical parameters of the working fluid by selecting substances with specific fugacity values (>17 bar at 115°C) and molecular structures (cycloalkanes, alkenes, dienes, alkynes, ethers). This parameter optimization enables the working fluid to better utilize the low-temperature heat source, increasing the efficiency of thermal energy conversion into electrical energy above 12% and potentially reaching 14% or higher with optimal substances like propadiene and dimethyl ether.
2Productivity
If the working fluid is fed back to the turbine to cool the generator and lubricate seals, then the system achieves efficient heat utilization, but the system complexity increases
Solution Approach 1:
The patent applies multi-functionality by using the working fluid for multiple purposes within the cycle: it serves as the working medium for energy conversion, the cooling medium for the generator, and the lubricating medium for turbine seals. This eliminates the need for separate cooling and lubrication systems, thereby reducing overall system complexity while maintaining high heat utilization efficiency.
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
This approach increases electrical energy generation efficiency to values above 12%, with certain substances like propadiene and dimethyl ether achieving efficiencies of 14% and above, effectively converting more thermal energy into electrical energy.
Implementation Method 1
heat from a low-temperature heat source is transferred to a working medium
Implementation Method 2
The working fluid is fed to the turbine and expanded using a nozzle. The generated jet of work equipment has kinetic energy
Implementation Method 3
The working fluid (gaseous or gaseous/liquid) is cooled, condensed
Implementation Method 4
The working fluid is cooled, condensed and passed through a pump, which increases the pressure in the working fluid
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a method for generating electrical energy by means of at least one low-temperature heat source (2), according to which a VPT cyclic process (1, 10, 100) is carried out. Certain working substances are used to increase the efficiency of the VPT cyclic process.