Remarkable development in Queenstown

The mountains surrounding Queenstown on New Zealand’s south island overlooking Lake Wakatipu are aptly known as The Remarkables. If you’re familiar with this part of the world you’ll appreciate the effort that went into establishing a 6.4-hectare master plan for the Kawarau Falls Station (KFS) development.

The KFS development consists of four primary buildings: Reserve North, Kingston West, Reserve South and Central, and Lakeside West. Norman Disney & Young (NDY) has been an integral part of the design team for the KFS development commencing with the initial site-wide services investigations and concept designs. With the exception of Lakeside West, NDY also completed the building services for the entire development.

The Reserve North project is the largest of the four buildings and it is here that one of the most innovative examples of sustainability is incorporated. Lake Wakatipu plays its part in the lake water heat rejection system which is heating and cooling system. Hidden from view, the system circulates around 100 L of water per second in the lake.

“What’s unique about this heat rejection system is its ability to remove the need for cooling towers and to allow for water-cooled variable refrigerant volume (VRV) condensers to be located in decentralised plant rooms around the hotel,” says NDY Auckland Director Michael Sullivan.

“The method of heat rejection for the air-conditioning system is via the use of geothermal energy from the lake water, on a once-through, open-circuit basis,” he says.

In fact, the main benefit of the system is its use of clean, renewable and sustainable energy from a natural source. The lakeside interface to the development is via a plate heat exchanger and therefore the only effect on the lake water is a small change in temperature.

Because of its unusual shape, Lake Wakatipu has a ‘tide’ - referred to as an unusually large seiche or ‘standing wave’ - which causes the water level to rise and fall about 10 cm approximately every 25 minutes. Despite this, the water flow to the lake from the heat rejection system can be varied to limit temperature increases.

The summer to winter variation in lake Wakatipu water temperature from approximately 16.5 to 8.5°C respectively is ideal for summer cooling while remaining sufficiently high during winter to allow the water to be used as a heat source without risk of freezing in the condenser heat exchanger coil.

Sullivan says that a major selling point for the VRV system is the superior efficiency resulting from the heat reclaim system, which reduces operating costs.

NDY New Zealand Regional Director Ross Legh was instrumental in designing the lake water heat rejection system and says that, apart from the obvious advantage of abundant renewable energy, there are other benefits associated with the system.

“The heat rejection system is characterised by very low noise levels and an absence of ‘cooling tower plumes’, which are important considerations in this ecotourism part of NZ,” he says. “We’ve also eliminated the unsightly external infrastructure associated with conventional air-cooled condenser systems, again being sympathetic to the serenity of the surrounding area.”