Geothermal energy recovery process with selective recirculation
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Solution Overview
Problem
Supercritical CO2 geothermal energy recovery systems face inefficiencies under high ambient temperature conditions, requiring energy-intensive compression and suboptimal working fluid composition, especially when ambient temperature exceeds the CO2 critical point.
Innovation Solution
A geothermal energy recovery system and method that control the composition of the working fluid by separating and mixing carbon dioxide with hydrocarbons such as ethane and propane based on detected ambient and process conditions, using a programmable electronic control unit to optimize energy recovery efficiency and reduce compression energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If supercritical CO2 is used as working fluid under high ambient temperature conditions, then geothermal energy capture is enabled, but compression becomes energy intensive and efficiency decreases
Solution Approach 1:
The system dynamically adjusts the working fluid composition parameters (CO2 to hydrocarbon ratio) based on ambient temperature and pressure conditions. The separator unit modifies the chemical composition of the working fluid to optimize it for current environmental conditions, transitioning from pure supercritical CO2 to a mixed composition that reduces compression energy requirements while maintaining energy capture effectiveness.
Solution Approach 2:
The working fluid composition is made dynamic rather than static. The separator unit continuously adjusts the mixture ratio of CO2 and hydrocarbons in response to changing ambient conditions, allowing the system to adapt its working fluid properties in real-time to minimize compression energy consumption across varying temperature and pressure environments.
2Power
If supercritical CO2 compression is used above critical point temperature, then geothermal energy recovery is achieved, but the process becomes less efficient compared to liquid CO2 compression below triple point
Solution Approach 1:
The system uses a composite working fluid consisting of CO2 mixed with hydrocarbons (such as ethane, propane, or butane) instead of pure CO2. This composite composition leverages the favorable compression characteristics of hydrocarbons to improve overall compression efficiency while maintaining the supercritical state necessary for geothermal energy recovery above the CO2 critical point.
Solution Approach 2:
The system changes the physical and chemical parameters of the working fluid by adjusting the hydrocarbon content in the mixture. By varying the composition parameters based on operating conditions, the system optimizes the balance between maintaining supercritical state for energy recovery and achieving efficient compression, thereby improving overall productivity.
3Ease of operation
If working fluid composition is fixed as pure CO2, then system operation is simple, but energy recovery efficiency decreases under varying ambient conditions
Solution Approach 1:
The system incorporates feedback control through the separator unit that monitors ambient temperature and pressure conditions and adjusts the working fluid composition accordingly. Sensors detect environmental parameters, and the separator unit responds by modifying the CO2-to-hydrocarbon ratio in real-time, creating a closed-loop control system that optimizes energy recovery efficiency while adapting to varying ambient conditions.
Solution Approach 2:
The separator unit serves multiple functions: it separates CO2 from hydrocarbons, adjusts working fluid composition, and optimizes the mixture for different ambient conditions. This multi-functional component enables the system to maintain high energy recovery efficiency across a wide range of operating conditions while managing the complexity of variable composition control.
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 system achieves improved energy recovery efficiency by adjusting the working fluid composition to match ambient conditions, minimizing compression energy and enhancing CO2 sequestration, particularly at temperatures above the CO2 critical point, thereby optimizing the geothermal energy capture process.
Implementation Method 1
a phase separator having an input port coupled to the extraction well and receiving an extracted working fluid including carbon dioxide and hydrocarbons therefrom, the phase separator operative to separate liquid and vapor portions the extracted working fluid
Implementation Method 2
the separator unit being controllably operated to separate components of the received working fluid based on chemical composition
Implementation Method 3
an expander coupled downstream from the controllable separator unit and operable to generate mechanical or electrical energy from expansion of the modified working fluid
Implementation Method 4
a condenser coupled downstream from the expander operable to cool the expanded working fluid
Implementation Method 5
a compression device coupled downstream from the condenser operable to increase the pressure of the working fluid received from the condenser to a pressure level suited for re-injection into the reservoir
Data Source
AI summary
A system method of geothermal energy recovery includes injecting carbon dioxide into a geothermal reservoir through an injection well, extracting a working fluid including previously injected carbon dioxide and hydrocarbons entrained in a flow of the carbon dioxide within the reservoir from an extraction well, separating components of the heated working fluid based on chemical composition, selectively mixing the separated components according to the current conditions of the extracted working fluid to produce an output modified working fluid that having a chemical composition that is optimized for energy recovery efficiency, and expanding the modified working fluid to generate mechanical or electrical energy.