Underground Cable Concrete Encasing Low Thermal Resistivity
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Solution Overview
Problem
Current methods for encasing underground electrical cables in concrete to reduce thermal resistivity often require carbon-rich materials, increasing costs and sourcing issues, while existing solutions do not adequately address heat dissipation for high voltage cables.
Innovation Solution
A method involving a fresh concrete composition with a hydraulic binder, mineral additions, and water, where the paste volume is minimized and the solid volume fraction maximized, eliminating the need for carbon-containing additives and achieving low thermal resistivity without using carbon-rich components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If carbon-rich materials are used to reduce thermal resistivity of concrete encasing, then heat dissipation improves, but material cost and sourcing complexity increase
Solution Approach 1:
The invention extracts and eliminates the requirement for carbon-rich materials (graphite, carbon black) from the concrete composition while maintaining the desired thermal resistivity through optimized conventional concrete formulation with controlled water-cement ratio and aggregate composition
Solution Approach 2:
The patent replaces expensive carbon-rich additives with standard, readily available concrete materials that are cheaper and easier to source, accepting that the thermal performance is achieved through material composition rather than expensive additives
2Temperature
If larger diameter cables are used to reduce heat generation, then cable heat dissipation improves, but cable cost increases significantly
Solution Approach 1:
The concrete encasing acts as an intermediary thermal management system between the cable and the surrounding ground, actively conducting heat away from the cable through its optimized composition, thereby allowing smaller cables to achieve the same thermal performance as larger cables would provide in air
3Temperature
If paste volume in concrete is reduced and solid volume fraction is increased, then thermal resistivity decreases, but concrete workability may be affected
Solution Approach 1:
The invention changes the physical and chemical parameters of the concrete composition, specifically optimizing the water-cement ratio, paste volume fraction, and solid volume fraction to achieve a balance where reduced paste volume (below 320 L/m³) and increased solid content (>50 vol.-%) lower thermal resistivity while maintaining adequate workability through careful parameter selection
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 approach results in a concrete with thermal resistivity below 0.7 m·K/W, allowing for the use of lower-cost, smaller cross-section cables and avoiding the need for expensive carbon-containing materials, while maintaining adequate heat dissipation for medium to high voltage cables.
Implementation Method 1
a hydraulic binder such as Portland cement, which produces strength-forming phases by solidifying and curing in contact with water
Implementation Method 2
the thermal resistivity, expressed in m·K/W, or the thermal conductivity, expressed in W/m·K, of the surrounding material are of high importance
Data Source
AI summary
A method for encasing underground electrical cables, includes (a) providing a fresh concrete composition including a paste that includes a hydraulic binder, a mineral addition and water, the paste being present in a mixture with sand and aggregates, whereby the paste is present in the concrete composition in a volume of <320 L/m3 and/or the solid volume fraction of said paste is >50 vol.-% and (b) placing the fresh concrete composition so as to encase the underground cables therewith.