Threaded truss foundations and related systems, methods, and machines
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Solution Overview
Problem
Conventional foundations for single-axis solar trackers, such as monopiles and ground screws, are costly and inefficient due to their design, which leads to oversizing and increased material usage to resist bending forces from lateral loads, and lack cost competitiveness with traditional structures.
Innovation Solution
A truss or A-frame foundation system using screw anchors with a moderately angled A-frame configuration, where screw anchors are driven into the ground at acute angles to convert lateral loads into axial forces, reducing material requirements and manufacturing costs, and incorporating a mandrel for in-situ refusal mitigation and soil engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If monopiles are used to support single-axis trackers, then the foundation can resist lateral loads, but the monopiles must be oversized and driven deeply into the ground, increasing material usage and cost
Solution Approach 1:
The foundation is divided into multiple ground screws arranged in a triangular pattern rather than using a single monopile. This segmentation allows the lateral load to be distributed across multiple smaller elements, each experiencing primarily axial forces rather than bending moments, thereby reducing the total material required while maintaining equivalent or superior lateral load resistance.
Solution Approach 2:
The ground screws are installed at inclined angles rather than vertically, transitioning from a one-dimensional vertical support to a three-dimensional angled configuration. This angular arrangement converts lateral loads into axial compression and tension forces along the screw axes, eliminating the need for oversized cross-sections and deep embedment required by vertical monopiles.
2Ease of manufacture
If conventional ground screws are used, then installation is simpler, but they lack cost competitiveness and robustness compared to traditional monopile structures
Solution Approach 1:
The ground screws feature location-specific optimizations including variable pitch threading (coarser pitch at the tip for initial engagement, finer pitch higher up for enhanced grip), tapered geometries, and strategic blade placements. These localized quality enhancements improve soil engagement and pull-out resistance without compromising installation simplicity, making the system both easier to install and more reliable than conventional uniform-ground-screw designs.
Solution Approach 2:
The ground screw system combines multiple material properties and structural features within a single component: threaded sections for soil engagement, smooth sections for rotation, tapered geometries for stress distribution, and integrated blades for mechanical interlocking. This composite approach creates a multifunctional element that maintains installation simplicity while achieving superior reliability and cost competitiveness.
3Ease of operation
If monopiles are used, then the foundation structure is simple to install, but bending forces require oversizing the single structural member
Solution Approach 1:
Instead of designing a vertical monopile that must resist bending moments, the invention inverts the approach by using inclined ground screws where the lateral load becomes an axial load. This inversion transforms the unfavorable bending stress state into a favorable compression/tension state, allowing smaller, lighter components to achieve equivalent or superior performance while maintaining ease of installation through rotary driving.
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 A-frame foundation system provides a more robust and cost-effective solution by reducing material usage and enabling deeper soil engagement, improving resistance to lateral loads without the need for oversized structures, thus lowering overall project costs for solar tracker installations.
Implementation Method 1
screw anchors are driven into the ground at acute angles to convert lateral loads into axial forces
Implementation Method 2
incorporating a mandrel for in-situ refusal mitigation and soil engagement
Data Source
AI summary
A machine for rotary driving screw anchors into underlying ground and related. The machine has a mast with a rotary driver and a mandrel driver oriented on a common axis. The mandrel driver passes a mandrel through the rotary driver and the screw anchor to allow the mandrel to be actuated ahead of the screw anchor while the rotary driver drives the screw anchor into the ground. Alternatively, the mandrel driver may also drive a hammering drill through the screw anchor to clear a path ahead of it through subsurface rocks.