Key Highlights:
- Urban Canopee overcame challenges in finding a suitable material for their canopy systems by partnering with Exel Composites to utilise pull-wound composite tubes.
- Urban Canopee uses curved structures constructed from straight tubes to enhance structural rigidity and minimise deflection, the bending or deformation of the canopy itself. This deflection is a limitation of traditional flat sheet designs.
- Looking ahead, the collaboration is exploring the potential of translucent composite tubes. These would allow for the integration of lighting within the structure, enhancing functionality and aesthetic appeal.
The urban heat island effect — when a city experiences much warmer temperatures than nearby rural areas — poses a significant challenge in modern cities, where soaring temperatures exacerbate energy consumption, air pollution, and public health concerns. Urbanisation leads to the replacement of natural land cover with buildings and infrastructure that absorb and retain heat, raising local temperatures by up to three degrees Celsius, compared to surrounding rural areas. The issue: managing this without excessive financial, material, and time resources. The solution? Manufactured canopies using pull-wound composites.
One innovative approach to combating the urban heat island effect is the introduction of green infrastructure solutions like parks and living roofs. Central Park in New York City is a prime example. Originally constructed to offer new Yorkers a place to escape the stresses of urban life in an increasingly populous city, the greenspace also has many environmental positives for the city, like capturing pollution, absorbing heat and oxygenating the air. However, large scale projects like this, while beneficial, require substantial investment and time, making them less feasible for rapid implementation.
An emerging solution in combating the urban heat island effect involves distinct technological advancements. New approaches include cool roofs, cool pavements, and permeable pavements. Cool roofs reflect sunlight and absorb less heat, while cool and permeable pavements reduce surface temperatures and runoff through additives that reflect solar radiation.
These measures, alongside vertical gardens, tree planting programs, and shade structures, aim to enhance urban environments by increasing greenery and reducing heat absorption, albeit often requiring impressive investment. A more cost-effective solution combines the benefits of shade structures, vertical gardens, and tree planting programs into manufactured canopy systems. These movable and scalable structures support climbing plants, naturalising urban spaces through retrofitting existing infrastructure.
Urban Canopee, a specialist in green infrastructure solutions, emerged with a mission to address the adverse effects of urbanisation by integrating these manufactured canopy systems into urban environments. These canopies form a flaring net that supports climbing plants, allowing for the naturalisation of urban areas with movable structures. However, the company faced significant challenges early on due to limitations in material production from its initial manufacturing partner.
"Initially, we faced sourcing challenges with our plastic supplier, limiting our production capacity,” explained Elodie Grimoin, chief technical officer and co-founder at Urban Canopee. “However, this challenge also provided an opportunity to reassess our materials. We needed something stronger and more durable than plastic for the frame of our canopies.”
As Urban Canopee grappled with sourcing challenges, it sought a material that could meet the stringent requirements for canopy system construction. While plastic fitted the required combination, the company was seeking a material that could offer even greater strength, enhanced durability, and reduced weight.
This led Urban Canopee to explore alternatives, ultimately discovering Exel Composites, a Finnish composites manufacturer specialising in pull-wound composites.
Exel Composites
Exel Composites' carbon fibre tube
Composites meet the demand
"The brief from Urban Canopee necessitated a material that could provide the perfect balance of strength, flexibility, and lightweight properties for the company’s canopy systems,” explained Lauri Turunen, product business owner for tubes and telescoping poles at Exel Composites. “Our pull-wound fibreglass composites fit these requirements by employing cross-aligned fibres, ensuring resilience against hoop stress. This is the force exerted around the circumference of the tube when it is under stress. This feature makes our tubes ideal for various applications, including canopy systems.”
During development of the tubes, a specific challenge emerged; straight tubes needed to conform to curved structures within the canopy systems. Urban Canopee uses curved structures constructed from straight tubes to enhance structural rigidity and minimise deflection, the bending or deformation of the canopy itself. This deflection is a limitation of traditional flat sheet designs.
Exel Composites focused on refining the composition of its composite tubes and customising the resin system to meet these needs. The goal was to ensure the tubes met these requirements while still maintaining a balance between strength, flexibility, and weight. Specifically, the tubes needed to be lightweight so the structure can be moved easily, strong enough to withstand high wind loads and other environmental stresses, and flexible enough to conform to the curved structures of the canopy systems without compromising their structural integrity.
The special characteristics of these pull-wound composite tubes allow them to maintain their strength and flexibility while remaining lightweight. For example, glass fibre composites have a tensile strength reaching up to 3033 MPa, surpassing that of aluminium’s 1600 MPa or an acrylic/polycarbonate plastic at 61 MPa. Furthermore, glass fibre composites have a density of 2.49 g cm-3 compared to aluminium’s 3.63 g cm-3, making them almost half the weight of aluminium while maintaining similar mechanical strength.
Beyond the mechanical properties, the composite significantly improved production efficiency. Compared to plastic extrusion, pull-winding produces higher strength tubes that can be made in much longer lengths with more uniformity. Extrusion is often limited in its capacity to produce uniform plastic products. Leveraging continuous manufacturing techniques, these new composites tubes enabled Urban Canopee to streamline its manufacturing process, reducing production lead times. The ability to produce tubes more quickly and consistently has allowed Urban Canopee to develop and deploy its canopy systems in urban areas such as Châlons-en-Champagne and Toulouse.
Looking ahead, the collaboration promises further advancements in technology. Urban Canopee and Exel Composites are exploring the potential of translucent composite tubes. These would allow for the integration of lighting within the structure, enhancing functionality and aesthetic appeal.
As cities worldwide grapple with the challenges of urbanisation and climate change, solutions rooted in green infrastructure and advanced materials offer promising pathways forward. Just as Central Park provides a cooling oasis in the heart of New York, projects like Urban Canopee’s demonstrate how thoughtful design and innovative technology can transform urban landscapes. By harnessing the power of alternative materials, innovators can continue to build cities that are not only sustainable but also more comfortable and resilient in the face of rising temperatures.