Percussion Mole Ground-Loop Insertion Without Drilled Boreholes
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Solution Overview
Problem
Current methods for installing underground pipework for geothermal heat-pump systems are costly and inefficient, especially in confined locations, as they require expensive drilling equipment and risk partial collapse of holes, necessitating thermally conductive caulking to maintain efficiency.
Innovation Solution
A percussion mole apparatus that concurrently creates a blind-ended passage and inserts a closed loop of pipework, using a pressurized fluid to drive the mole and eliminate the need for expensive drilling equipment, with a valve assembly to switch between insertion and operational configurations, and the use of granular materials to reduce friction and potential collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional drilling techniques are used to create deep holes for geothermal pipework, then access to distant end of hole is achieved, but equipment cost and complexity increase significantly
Solution Approach 1:
The patent employs a disposable percussion mole that is driven into the ground to create the hole and then abandoned in place. This eliminates the need for expensive, complex drilling equipment that would otherwise be required to create deep holes for geothermal pipework. The mole is a simple, inexpensive device that performs its function and is discarded, replacing costly reusable drilling machinery.
Solution Approach 2:
The patent replaces conventional mechanical drilling systems with a percussion-based system. The mole uses a piston-driven percussion mechanism to fracture and displace soil, creating a hole through vibration and impact rather than rotational drilling. This substitution simplifies the equipment while achieving the same result of creating deep access holes.
2Ease of manufacture
If drilling equipment is used to create holes, then pipework installation is enabled, but hole collapse risk increases requiring additional caulking materials
Solution Approach 1:
The percussion mole creates the hole and simultaneously compacts the surrounding soil during its installation process. This preliminary compaction stabilizes the ground before the pipework is inserted, preventing hole collapse and eliminating the need for additional caulking materials to seal gaps between the pipes and ground.
Solution Approach 2:
The mole's own installation process serves to stabilize the hole. As the percussion mole is driven into the ground, its operation compacts the surrounding soil and creates a stable cavity. The system uses its own installation action to prepare the hole, eliminating the need for separate stabilization or caulking operations.
3Device complexity
If percussion mole is used to create passage, then equipment cost is reduced, but friction between casing and ground increases
Solution Approach 1:
The patent changes the physical parameters of the ground during mole installation. The percussion action temporarily alters the soil structure and density around the mole casing, reducing friction coefficients during the driving process. This allows the simple, low-cost mole to overcome ground resistance and achieve installation despite the inherently high friction between casing and soil.
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 reduces installation costs, eliminates the need for thermally conductive caulking, and enhances operational efficiency by simplifying the construction process and ensuring effective heat transfer, while minimizing environmental impact and operational complexity.
Implementation Method 1
using a pressurized fluid to drive the mole
Implementation Method 2
The mole is driven by compressed air, provided along a rear-mounted compressed air hose. An internal piston having significant mass is caused to travel rapidly forwards within the tubular casing of the mole, where it strikes the forward end of the casing, driving the casing forwards, displacing the ground around the casing in the process.
Implementation Method 3
An internal piston having significant mass is caused to travel rapidly forwards within the tubular casing of the mole, where it strikes the forward end of the casing, driving the casing forwards
Implementation Method 4
the use of granular materials to reduce friction and potential collapse
Data Source
AI summary
An apparatus for inserting a ground-loop for a geothermal heat-pump system comprises: a percussion mole (4); a first fluid pipe (5), connected to the mole (4), for conveying a heat-exchange fluid from the heat-pump system into the ground; and a second fluid pipe (6), connected to the mole (4), for returning the heat-exchange fluid to the heat-pump system. One of the first and second fluid pipes (5, 6) comprises an intake pipe for delivering a driving fluid to the mole (4) during insertion of the ground-loop and the other fluid pipe comprises an exhaust pipe for the driving fluid.