8 September 2010 – Brisbane’s Green Square North Tower, a 6 Star Green Star, $94million mixed-use office complex, has become the first commercial building in Australia with an operational co-generation plant to be awarded a 5 Star NABERS Energy whole building rating.
The building, designed by Cox Rayner and constructed by Leighton Contractors, is also the first commercial building in Queensland to earn a 6 Star Green Star – Office Design v2 rating by the Green Building Council of Australia.
Floth Sustainable Building Consultants provided environmentally sustainable designs in mechanical and electrical services and energy modeling for the development.
Completed in September 2009 and located in the Brisbane suburb of Fortitude Valley, immediately adjacent to the CBD, Green Square North Tower is one of the city’s largest mixed use corporate office parks, consisting of 23,500 square metres of A-grade office space spanning over 12 levels, 600 sq m of retail space and basement parking for up to 154 cars.
Floth managing partner R. Glenn Ralph said by implementing co-generation technology, which works by recycling waste heat from power generation to chill water for the building’s air-conditioning system, Floth eliminated the use of solar panels and the need for purchasing green power, resulting in a cost effective alternative.
“Currently the North Tower generates 770 kilowatts of electricity as a result of the co-generation plant. To generate the same amount of peak electricity using solar panels we would need an area three to four times the size of the building’s available roof.
“Floth has achieved a whole building emission rating of 12 9kilograms of carbon dioxide per square metre per annum, which is the lowest emission figure for a building of its size in Australia,” Mr Ralph said.
Some of the sustainable features of Green Square North Tower include:
Electrical Services Solutions
- PVC free mains and sub-mains cables to avoid the use of known toxins and carcinogens which are harmful to human health.
- High efficiency single tube T5 luminaries complete with low brightness louvres that provide less than 5 watts per square metre power density, equating to 157 Toyota Prius’s being removed from the roads per year
- Glare free lighting for computer applications
- Low frequency flicker was eliminated to reduce occupant eye strain and the potential for headaches
- 20 switching zones per floor make it easier to light only occupied areas and provide greater flexibility for fit-out purposes.
- Motion sensors for after hours operation to avoid unnecessary energy use
- External lighting has been designed to reduce urban sky glow and its effects on nocturnal wild life
- Gas engine generator as a part of the co-generation plant simultaneously produces electricity and useful thermal energy from a low carbon emission fuel source – natural gas
- Localised generation of electricity reduces the demand on the public electrical infrastructure network (the grid) and eliminates energy losses in the transmission of power to the site
- Thermal energy utilised within an absorption chiller for the production of chilled water
- In the event of a grid power failure, the same generator also provides standby power in excess of the Property Council of Australia A Grade requirements
- Exhaust gas emission are controlled using Selective Catalytic Reduction technology to significantly reduce nitrous oxides emissions
- Intelligent energy meters installed on all major electrical uses monitor and record the performance of the building and enable continual optimisation.
Mechanical Services Solutions
High Efficiency Low Temperature Variable Air Volume Air Distribution (Cold Air Distribution):
The building utilises a central air handling plant that provides the following:
- Higher energy efficiency due to the use of large scale equipment dedicated to each facade and internal area
- Higher acoustic performance due to the removal of plant from the occupied floors
- Elimination of the need to undertaken maintenance on the occupied floor
- Lower capital cost compared to traditional on-floor plant (approximately 5 per cent)
Cold air distribution employing high induction swirl air diffusers provides the following benefits:
- Lower energy consumption and improved acoustic performance due to reduced air volumes
- Improved occupant comfort due to lower space humidity
- Lower capital cost compared to standard temperature air distribution
- Air handling units employing low cooling coil velocities resulting in reduced fan energy consumption with improved de-humidification capabilities
- Variable speed drives provided on all air handling unit supply and return air fans realise energy savings available during periods of low air-conditioning demand
- Outside air volume is constantly maintained irrespective of reductions in air conditioning demand, for improved indoor air quality
- Carbon dioxide monitoring and control systems increase the outside air volume above the maintained minimum, in response to increases in building population
- Computational fluid dynamics is employed as a design tool to enhance the air distribution performance, in order to improve occupant comfort and indoor air quality
- An outside air economy cycle is employed during the cooler months to provide natural cooling to the occupied space
- Condensated water is captured and reuses for irrigation and toilet flushing
Chilled Water Generating Plant and Distribution:
- Free cooling from a base load co-generation plant utilises waste heat from exhaust gases and engine jacket water to generate chilled water for use in the air conditioning system
- High efficiency electric screw chillers are employed when building cooling load exceeds the co-generation plant capacity
- Chilled water distribution employing a variable volume variable pressure pumping control strategy is used to minimise chilled water pump energy consumption
- Auto adaptive condenser water optimisation temperature control strategy is used to minimise energy consumption of the chilled water generating plant
- High efficiency cooling towers with low fan power are used for reduced energy consumption
- Car park ventilation employs carbon monoxide monitoring and control for reduced fan energy consumption
- Variable speed drives on all base building miscellaneous ventilation fans ensure tenant flexibility and reduced energy consumption
Building Management Control System
A fully distributed open protocol direct digital control system monitors and controlls all building systems. The system also control and monitors the mixed mode winter garden environmental conditions.
- Computer based numerical modeling shows that the base building will use 53.3 per cent less energy than an equivalent 4 Star NABERS Energy rated building.
- Base building modeled at 26 kg of carbon dioxide per sq m per annum. This equates to a reduction in the annual carbon emissions of 1,645,000 kg (or 721 Toyota Prius’s removed from the road) when compared to an equivalent 4 Star NABERS Energy rated building.