Ground Loop Thermal Resistance Calculation from Heat Pump Data
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Solution Overview
Problem
Current methods for determining ground thermal conductivity in ground source heat pump systems are costly and inaccurate, relying on either expensive in-situ testing or low-resolution public data, which fail to account for varying soil and rock properties, density, and moisture content, leading to errors in ground loop thermal resistance calculations.
Innovation Solution
A method using real-time monitoring of heat pump performance and ground loop fluid temperature to empirically calculate ground loop thermal resistance values without requiring knowledge of soil properties or bore geometry, allowing for accurate prediction of thermal resistance at future sites through data aggregation and mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If in-situ thermal conductivity testing is performed, then measurement precision of ground thermal conductivity is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent uses heat pump system operational data as a substitute for direct thermal conductivity measurement. By analyzing temperature and power data from the heat pump system during normal operation, the method derives ground thermal properties without requiring specialized testing equipment or procedures, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The heat pump system itself serves as the measurement tool by utilizing its own operational data (power consumption, fluid temperatures) to determine ground thermal conductivity. This eliminates the need for separate testing equipment and allows the system to provide its own performance characterization data
2Reliability
If in-situ testing is conducted, then reliability of thermal conductivity data is improved, but loss of time and cost increase due to specialized equipment and 48-hour testing period
Solution Approach 1:
The patent performs thermal resistance calculations using heat pump operational data that is collected during normal system operation before any design finalization is needed. This preliminary data collection occurs continuously during system operation, eliminating the need for separate 48-hour testing periods and providing reliable data when needed for design decisions
Solution Approach 2:
The method continuously collects and utilizes heat pump operational data during normal system operation to determine ground thermal properties. This continuous data collection replaces discrete, time-consuming test periods and provides ongoing verification of system performance and ground conditions
3Device complexity
If drill logs or public data sources are used to estimate ground thermal conductivity, then device complexity is reduced, but measurement precision and reliability deteriorate due to low resolution and incomplete information
Solution Approach 1:
The patent uses actual heat pump system performance data (power consumption, fluid temperatures, flow rates) to calculate and continuously refine the ground thermal resistance value. This feedback from real system operation provides precise, site-specific thermal conductivity information that overcomes the limitations of generic drill logs and public data sources
Solution Approach 2:
The method transforms readily available heat pump operational parameters (power, temperatures, flow rates) into accurate ground thermal conductivity values through thermal resistance calculations. This parameter transformation converts simple, easily measured quantities into precise geological characterization data without requiring complex measurement equipment
4Ease of operation
If traditional thermal resistance calculation methods are used, then ease of operation is improved, but measurement precision deteriorates due to dependence on accurate ground thermal conductivity and bore geometry knowledge
Solution Approach 1:
The patent inverts the traditional calculation approach by not calculating thermal resistance from known thermal conductivity and geometry, but rather determining thermal resistance directly from heat pump operational data. This inversion eliminates the need to know exact bore geometry and soil properties, providing accurate thermal resistance values through direct measurement of system performance
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 enables quick, accurate, and cost-effective determination of ground loop thermal resistance, reducing design uncertainties and providing high-fidelity predictions for ground loop design lengths and installation costs, improving the overall efficiency and cost-effectiveness of geothermal heat pump systems.
Implementation Method 1
a ground source heat pump that operates to cool or heat a space or building by extracting or rejecting heat to or from a ground loop
Data Source
AI summary
In some embodiments, a method operates a heat pump that uses a ground loop to perform heating or cooling in a site. During the operating of the heat pump over a time period: the method measures a first series of measurements of a ground loop water flow rate by the heat pump; a second series of measurements of a ground loop fluid temperature for the heat pump; and measures a third series of measurements of a local soil or deep earth temperature. The first measurement, the second measurement, and the third measurement are outputted where a ground loop thermal resistance value is calculated for the heat pump based on the first measurement, the second measurement, and the third measurement.