29.04.2024
Grimshaw’s Dubai Energy Trees were launched to an enthusiastic response during Expo2020 and have since become a permanent installation at the heart of a new district on the outskirts of Dubai. Despite the excitement, little has been presented on their design evolution that resulted from a consolidation of data-driven factors, especially in achieving the solar energy demands to meet the growing aspirations for the Sustainability Pavilion precinct.
As with any industrial design process, a successful product requires more than conceiving an elegant form or a good idea; the designer must embark on extensive phases that include data gathering, ideation, content generation, testing, and evaluation to achieve a buildable concept. These phases reflect the aesthetic resolution of the Energy Tree from competition to end-product, which fundamentally changed due to the emerging realities of the project program.
During conceptualization, the basis of the design was to optimize the solar harnessing capability of a large circular disc that could track the sun while elevated 15-20 metres above ground on a vertical column. The final number of Energy Trees would supplement the performance requirements for the Sustainability Pavilion and its operations. The design was eventually repeated across the site 18 times with various height stems and two different disc diameters up to 17.5 metres. The economies-of-scale attitude to customization emerged because there was adequate repetition of parts.
Through our energy model research, we found that standard solar panels, which are typically less than 20kg per square metre, would offer significant cost reductions. However, the standard rectangle or square panel would force nuanced framing details and lack an integrated feel from the underside, while also lacking the energy requirements. On the contrary, custom panels specific for the challenge would allow concept freedom and additional benefits, such as bi-facial capability, where select underside panels could absorb light that is reflected off the ground or another material.
This data-gathering process influenced the design of a trapezoidal panel that could boost the solar harnessing capacity by four times per square metre compared to standard, generic panels. The quality, high-performance selection was necessary to achieve product longevity, in a challenging environment, vulnerable to factors such as solar heat gain. In a milder climate, a standard solar panel can last decades before gradually losing efficiency, but the hot, desert environment dictated the need for energy capability and resilience beyond what was available in the market.
Prior to the energy and structural investigation process, we utilised parametric scripts developed by Grimshaw’s Design Technology team to study the ecliptic movement of the sun according to the Energy Tree’s geo-location. Through these parametric studies, we discovered the single largest influencer on the eventual product. The desire for maneuverability of the solar disc was closely linked to the development of the form, impacting every stage from concept to the lifespan of the constructed product.
When an X-Y-Z rotation hub is applied at the top of the steel trunk, we could validate the year-round energy harnessing because the upper disc could track the sun all day, in every season, before returning overnight to begin the cycle again. The Grasshopper script also calculated the disc’s side angle in a static position for optimal annualized harnessing, and together with only a Z-axis rotation, the result was 8% less utilization compared to the full X-Y-Z capability. This small percentage was negligible given so many other aspects of the design would now be liberated, and the quality of solar panel technology would more than compensate for such a small difference. A range of dynamic loads and cantilevers were reduced, which meant less steel tonnage and leaner composite support arms. The enhanced, bi-facial solar panel design came with a 300% increase in glass weight compared to a standard panel, further validating the benefits of a Z-axis rotation.
The combination of all these research phases was paramount in establishing the final design toward a tangible product for fabrication. Built from steel primarily for its strength properties, the trunk was designed as a fixed component to support the upper composite disc and rotating sprocket. The idea was to see through the stem so that structural bulkiness could be mitigated, and visitors could walk through the base of the Tree trunk. The lateral stiffeners every 2.5 metres inside the steel column enabled a strong support structure that could be adapted to meet various heights and integrated into the undulating landscape around the Pavilion without overshadowing an adjacent Energy Tree. To access the solar panels and various systems, including the security cameras and lighting, a retractable ladder was integrated into the trunk and the structural laterals acted as landings for the maintenance personnel. These trunks were prefabricated and anchored into the above-ground concrete footing to mitigate corrosion and allow access to the baseplate and the various mechanical and electrical systems. Circular seating amenities were integrated into the base of the trunk to conceal and protect the condition.
Enabled by materials for their stiffness and strength-to-weight ratio, carbon fibre and composites were applied to form the iconic upper disc structure. These were designed to limit the amount of moulds, benefit our transportation and site installation requirements, and allow cost efficiencies across the family of energy trees.
Through the mindset of this design for manufacturing and assembly (DfMA), and enabled by a quality local contractor, we delivered an outcome that could only be possible through a synergy of design-to-construction disciplines. An innovative use of materials allowed for the resolution of the structural design and by applying our digital applications with the supplier’s testing processes, we were able to meet the demanding energy requirements of the project.
The Energy Tree embraces the future through an iconic form that provides decades of solar energy with life-cycle resilience and maintenance benefits in a hot and challenging environment. We continue to grow new concepts through industrial design with support from design technology and our sustainability group, bringing together a workflow that embodies the right expertise, rationale and sustainability aspirations.
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