By Craig Roussac

10 March 2011 – Electricity use in Sydney office buildings can more than double in extreme heat, but responsive management can keep a lid on greenhouse emission, research by conducted by the Green Buildings Alive project has found

Growing peak period demand is one of the major causes of rising electricity prices and any reduction in energy use at these times can bring substantial financial savings, reducing pressure on the network. The largest buildings can pay around $150,000 per year in peak capacity charges and $350,000 in network energy charges for the largest of CBD buildings.

Capturing data during extreme events like heatwaves shows that what you can’t see matters. The environmental impact of buildings changes from hour to hour and day to day.

For example, research of 11 Sydney buildings by GBA on the effect of a heatwave between 31 January and 6 February 2011 found 11 out of 20 experienced their highest electricity consumption during this week than on any other day during the preceding 12 months.  Electricity consumption was 2.1 times higher than in a “typical”week. One building’s peak electricity use on Thursday 3 Feb was over 1000 kW, when it would normally be around 570 kW for the base building.

Most office buildings are kept around 21.5°C in winter and 22.5°C in summer consistent with the lease conditions. In a city like Sydney a hot February week might see temperatures outside at 36 °C and inside at 23°C, so the airconditioning is working twice as hard.

There is a strong implication for peak demand on the network. If all other buildings were experiencing similar stress during the heat wave as the case study building then 19 per cent of the network capacity has to be reserved for peaks that only happen 1 per cent of the time.

Importantly, in many cases the rising peak demand is a consequence of buildings working extremely hard to make the inside air cooler than people might actually prefer.

A 2010 study by the Investa Sustainability Institute and The University of Sydney showed that raising internal air temperature “set points” by one degree celsius produced airconditioning savings of six per cent. It may be the case that we can make people more comfortable while saving power.

Professor Richard de Dear of Sydney University, an international expert on human thermal comfort, says, “It makes so much more sense to operate commercial buildings to more closely reflect the behaviour and expectations of their occupants during extreme weather events. People adapt to indoor and outdoor climates naturally, in their behaviour, with clothing, opening windows, their physiology (acclimatising), and psychologically (expectations). Buildings should be operated to take advantage of these factors.”

The institute launched Green Buildings Alive to encourage a holistic approach to energy supply and energy management in buildings so we can better respond to extreme weather events like this.

An example of this activity is a shirt to jacket ratio study being conducted by the Institute in the first
quarter of 2011 which looks at office attire against daily temperatures and complaints records.

The findings will help determine how much building managers could potentially allow insidetemperatu res to follow outside temperatures, when people are dressing for the weather.

Craig Roussac is director of Investa Sustainability Institute

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