CEC Solar Awards WINNER

1 Bligh Street, Sydney CBD, NSW

CATEGORY: 30-240kW

Matthew Linney and Jarrod Shepherd, Autonomous Energy

This 77.76kW solar solution on a 139-metre office building facing Sydney’s Circular Quay was designed to maintain the client’s requirement for a 6-star Green Star rating. The limited roof space  had initially been used for solar hot water collectors, but they were removed to make way for solar as a more efficient use of the area.

Tall buildings have additional challenges due to extreme wind loading, says Autonomous Energy CEO and founder Matthew Linney, and at 1 Bligh Street the wind uplift rating was higher than standard mounting systems or any solar panel are rated for. Autonomous worked with manufacturer SunPower to certify the Maxeon3 panels for use at the site and installed the modules back-to-back in an east-west configuration to reduce uplift. The whole installation was certified by a third-party structural engineer.

The roof that holds the PV system is a platform of metal grates built over a plant deck on the top level. The main support structure was suitable, Linney says, but there was some local reinforcement required as well as a custom fixing Autonomous designed and had fabricated to attach the solar mounting structure to the grates.

“Attaching custom fixings to fit the metal grate was challenging and they had to be installed as close as 400mm apart in some areas,” says Linney. “Due to the complex wind forces at the site, we had to contact the engineer who did the wind calculations at the design stage for the building to get data and then coordinate that with our engineers and the client’s structural engineer to agree on a solution.”

It’s a long way down

The roof that holds the PV system is a platform of metal grates built over a plant deck on the top level.

All the gear was brought up to level 26 via the service lift. From there, the install crew carried the 216 panels and three SolarEdge SE27.6K inverters another five flights to reach the roof. The first design had all the panels tilted north, with a standard gap between each row, but the layout was amended slightly so that exhaust fans from the chillers underneath the deck were not obstructed.

Solar is a good match for offices, Linney says, but PV is still something of a rarity in central business districts. The two biggest issues are the relatively small roof areas (often filled with a lot of mechanical plant and equipment) and shading from neighbouring towers.

“Wind loading, access constraints and space constraints for inverters and switchboards can also be challenges,” he says. “We have done a number of projects in the Sydney and Melbourne CBDs, though, on a range of buildings including very tall ones, heritage-listed and museums – so it can be done.”

There is little shading from neighbours at 1 Bligh Street but the system uses DC optimisers to reduce the impact of shading from objects on the rooftop.