Hemp Fiber Substrate with Integrated Irrigation Ducts
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Solution Overview
Problem
Conventional substrates for rooftop greening, such as earth, face challenges including delivery difficulties, inadequate water drainage, lack of cohesion, and poor longevity, especially under heavy rainfall and heat exposure, requiring a substrate that is easy to handle, maintains structural integrity, and allows for controlled watering and insulation while being cost-effective and industrially producible.
Innovation Solution
A monolithic carpet substrate composed of hemp fibers with integrated recyclable polymer fluid supply tubes and a reinforcing net, providing excellent cohesion, water retention, and fire resistance, designed for easy installation and maintenance, with automatic watering capabilities and the ability to be produced in rolls for efficient handling and large-scale production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional substrates like soil are used for rooftop gardens, then they provide basic plant growth medium, but they face delivery difficulties, poor drainage, lack of cohesion, and require filtration infrastructure
Solution Approach 1:
The substrate uses a composite structure combining natural plant fibers (humus, peat, coconut coir) with synthetic components (biodegradable geotextile, expandable graphite granules). This composite approach provides both the organic matter needed for plant growth and the structural integrity, drainage, and cohesion properties that conventional soil lacks, while remaining biodegradable and environmentally friendly.
Solution Approach 2:
The substrate modifies key physical parameters of conventional soil by incorporating expandable graphite granules that change volume and density based on water content, and by controlling particle size distribution and organic matter content. These parameter changes enable the substrate to achieve optimal drainage, water retention, and mechanical strength without requiring thick layers or complex installation infrastructure.
2Productivity
If the substrate thickness is increased to improve plant growth, then better root development is achieved, but handling and installation become more difficult
Solution Approach 1:
The substrate optimizes the thickness parameter to a specific range (5-15 cm) that balances plant growth requirements with handling feasibility. Within this optimized thickness, the controlled particle size distribution and organic matter content provide sufficient root development space while maintaining a weight and flexibility that enables easy manual handling and installation without requiring mechanical equipment.
3Reliability
If water retention is increased to support plant growth during dry periods, then plant survival improves, but the load on the roof structure increases
Solution Approach 1:
The substrate controls the water retention parameter through optimized organic matter content (30-70%) and particle size distribution, achieving sufficient moisture holding capacity for plant survival during dry periods. The controlled porosity and drainage properties ensure that water is retained when needed but does not saturate to excessive weights, maintaining roof load within safe limits while providing reliable plant support.
Solution Approach 2:
The substrate incorporates porous structures through its particle size distribution and organic matter composition, creating void spaces that hold water for plant uptake while maintaining overall substrate porosity for drainage. This porous architecture provides water retention without full saturation, balancing moisture availability with weight management for rooftop applications.
4Productivity
If natural plant-based substrates are used, then they are biodegradable and environmentally friendly, but they are highly flammable
Solution Approach 1:
The substrate combines natural plant-based materials (humus, peat, coconut coir) with biodegradable components and expandable graphite granules to create a composite structure. The graphite granules and controlled composition provide fire resistance while maintaining the biodegradability and environmental benefits of natural substrates, creating a material that is both eco-friendly and safe for rooftop applications.
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 substrate effectively addresses the challenges by ensuring stability on sloping roofs, efficient water management, and controlled watering, while being cost-effective and long-lasting, with high mechanical properties and fire resistance, suitable for industrial production and easy handling, supporting both thermal and sound insulation.
Implementation Method 1
The fibers of the two layers are intimately bonded together, and a suitable method for this is a carding operation. Thus the fibers of the two layers interpenetrate and ensure total cohesion.
Implementation Method 2
a substrate comprising a non-flammable fibrous material, in this case hemp, and fire-resistant inert granules, in this case expandable graphite granules
Implementation Method 3
For the user, it is about improving sound and thermal insulation in both hot and cold conditions, i.e., regulating the rooms under the roof.
Implementation Method 4
For the user, it is about improving sound and thermal insulation in both hot and cold conditions
Data Source
Figure 1~2
AI summary
The invention relates to a cultivation substrate with integrated irrigation, in particular for the cultivation of a roof, characterised in that it comprises a first ply (10) of fibres of a plant material, at least one fluid supply duct (12), a ply (14) for reinforcing and maintaining the at least one duct, and a second ply (16) of fibres of a plant material, wherein the first and second plies (10, 16) are linked by carding.