It’s the perfect marriage between nature and technology. The skyline in Sydney, Australia just introduced a new way of sharing the sun waves. Its newest building features a horizontal platform which houses a heliostat – a collection of mirrors. When the sunlight hits the building, the waves are redirected to an area in the city that is blocked from the sun. Robert Bird Group’s Jason Langer is the lead structural engineer on this project.
Jason Langer says, “Generally speaking on projects, you use the sun, you use the sun to actually deliver you your light. This project essentially was the architect saying the sun is not in the right spot for us, so we’re going to create a new sun in the sky where we want it.”
The heliostat includes an array of mirrors sitting across two apartment buildings (of One Central Park). First the sunlight strikes the mirrors on the lower building and is reflected upward to the heliostat on the higher building. Next, the light is deflected downward over a plaza and a new public park. The light also fills an indoor shopping center with natural light as it shines through the glass roof of its building.
Jason Langer says, “When we did research on heliostats that had been used on buildings in the past, we found a few that relied on light being reflected once, but nobody had ever tried to reflect light off two buildings into a final space. So this was beyond anything anyone had tried before.”
The upper mirrors are stationary, but the lower mirrors are computer controlled. The computer tracks the position of the sun and adjusts accordingly so that the rays are redirected properly. Tim Phillip’s Kennovations designed the mirror arrays.
Tim Phillips says, “This is the largest architectural installation of heliostats anywhere in the world, and it’s unique in that we’re dispersing sunlight instead of concentrating it.”
Jean Nouvel, French architect, designed the One Central Park building. But, Australian firm PTW Architects, along with its architect Matt Dobbs, prepared the detailed plans.
Matt Dobbs says, “So the concept for the light, the heliostat, wasn’t for a beam of light to hit the ground. The idea is that it is a dapple light, so if you can imagine walking under a canopy of trees.”
After sundown, the heliostat’s 2800 LED lights perform a light show in the night sky – thanks to the reflections on the water. The heliostat is supported by a cantilever platform. Many residents take a stroll on it as it features a garden area and spa pool. The platform presented many engineering challenges, however.
Jason Langer says, “With normal towers that are built straight up, because you can build one floor above the other. This tower gets to 35 stories up, and then goes the equivalent of 12 stories sideways.”
Engineers applied the same technique for the platform that they used to build steel bridges. They used trusses – steel frames put into triangular patterns to create strength – which can be seen all the way to the back of the building. But the garden creates a delicate contrast to these symbols of strength. Eventually, most of the building walls will be covered in plants.
What was once an industrial dark place is now turning green – illuminating with sunlight.