Power Play

In Heidelberg, the city-owned Stadtwerke Heidelberg Energie GmbH had the opportunity to reuse the site of a former 1950s gas tower that had already been removed in the industrial Pfaffengrund district with a renewable energy district heating network facility. Instead of merely updating the technology, a competition was launched to transform the site into a proud, accessible, and dynamic landmark representing the city’s ambitious green energy transition. Heidelberg is a progressive environmental role model in Germany, aiming to provide all households with CO₂-neutral energy from renewable sources by 2050 while also cutting emissions by 95%. This facility was a milestone accomplishment that needed to be celebrated.

LAVA’s winning design imagined the new 56m tall industrial cylinder as a lively social destination. A helix staircase loops around its 26m diameter, spiraling up to a rooftop viewing platform above the scenic Rhine plain, a panoramic restaurant, and an educational hub, exploring the story of renewable energy. “By inviting people to engage with and physically climb the structure, we transform a static energy tank into a lively social knowledge tank that feels alive,” says Tobias Wallisser, LAVA Partner.

Smoothly integrating the clashing demands of hybrid functions into one structure was a challenge that LAVA welcomed. “A hybrid building has the potential to confront and juxtapose diametrical functions. Here, we needed to mitigate the requirements of an inaccessible piece of public energy infrastructure while designing a vibrant social experience and a dynamic urban beacon for the future, visible from afar,” he explains.

The insulated tank, which stores energy in water heated to 115 degrees by solar and wind, continuously expands and contracts as heat is supplied to local households. This movement had to be considered when designing social facilities. A two-level floating steel grill with a diameter of 25m was inserted above the cylinder, supported by an independent cantilevered metal structure to accommodate the restaurant and event space. The whole structure had to be extremely lightweight, efficient, and flexible to address these somewhat contradicting requirements,” says Wallisser. “There’s no typology in the building code for a tower without a core. Its walls are thinner than an eggshell, yet it hosts 200 people dining at its top.”

The guiding principle for the design is the energy cycle. The kinetic aspect of the industrial infrastructure is captured by the dynamic hula hoop rings or ‘energy loops,’ spiraling staircases that wind helically upwards, self-supported in the gap between the insulated blue façade and the diagrid cable net of 11,000 stainless steel rhomboid shingles, which rotate in the wind and shimmer in the sunlight in gentle waves, creating an interplay of movement, light, and shadow. This robust exterior is a visual signifier of the impact decentralized renewable energy can produce, similar to a design device that LAVA implemented in Masdar Plaza, where sunflower-shaped structures absorb solar energy. “Resources such as energy and water need to be integrated better into architecture and urban life to make their cycles of movement and use more visible on a micro level through adaptive elements.” The architecture, therefore, becomes a symbol of a more sustainable, circular future.