Pump efficiency vital to Sydney power savings

Sydney-Town-Hall-Sydney-Sq

The City of Sydney has substantially reduced electricity use in their buildings, in some cases by up to 50 per cent, via a series of power and water efficiency retrofits. Large savings have been made across 45 buildings, including libraries, recreational centres and a recycling depot, many via upgrading the sites pumping systems to optimise efficiency.

The retrofit works were completed under a $6.9 million contract with Origin Energy with the aim of cutting electricity use in the City’s buildings by 6.4 million kilowatt hours per year – enough power to supply 870 households for one year. This will save the City an estimated $880,000 in annual power bills and $160,000 in annual water bills, save power and water, and reduce emissions.

These upgrades were undertaken as part of the City of Sydney’s program to cut its own energy and water consumption overall by 20 per cent compared to 2006 levels. The City, which is already Australia’s first officially carbon neutral government, also intends to reduce its carbon emissions by 70 per cent, compared to 2006 levels, by the year 2030 – the most ambitious target set of any Australian government.

“As cities are the greatest emitters of greenhouse gas, we need to make our buildings more energy efficient,” Sydney Lord Mayor Clover Moore said.

“New buildings are designed with energy efficiency in mind. We need to retrofit older buildings if we are going to make a real difference.”

So far, power reductions at City facilities include:

  • 68 per cent at the recycling depot
  • 52 per cent at Alexandria Childcare Centre
  • 39 per cent at Glebe Library
  • 32 per cent at Goulburn Street Car Park
  • 28 per cent at Customs House
  • 22 per cent at Paddington Town Hall
  • 21 per cent at Ian Thorpe Aquatic Centre
  • 17 per cent at King George V Recreation Centre
  • 5 per cent at Newtown Library

The efficiency measures employed during the retrofits ranged from those as simple as installing movement sensors on vending machines to switch off the lights when they are not in use, to overhauling various aspects of building’s engineering, upgrading whole systems and adjusting the voltage of the entire site.

As one of the primary energy users at many of the retrofitted sites, upgrades to pumping systems played a vital role in the retrofits.

For instance, HVAC systems of the City’s swimming pools and large buildings were improved by installing variable speed drives to pumps and by using refrigerant additives to optimise their efficiency.

Some of the major HVAC upgrades took place at the following sites:

The Ian Thorpe Aquatic Centre

Retrofitting the Ian Thorpe Aquatic Centre involved the installation of eight variable speed drives to reduce the energy consumed by the supply air fan and return air fan of the air handling unit, the recirculation pumps of the leisure pool and program pool pumps, and the hot water pumps of the boilers.

Frequency converters, such as variable speed drives, are electronic motor controllers that convert the AC mains input into a variable AC waveform output. The frequency and voltage of the output are regulated to control the motor speed or torque. The VSD can vary the speed of the motor in response to system feedback, such as changing temperature or pressure for controlling fan, compressor, or pump motors. This makes the system much more efficient. The frequency converter can also regulate the motor by responding to remote commands from external controllers.

In addition, the frequency converter monitors the system and motor status, issues warnings or alarms for fault conditions, starts and stops the motor, optimizes energy efficiency, and offers many more control, monitoring, and efficiency functions. Operation and monitoring functions are available as status indications to an outside control system or serial communication network.

The VSD’s used at the aquatic centre were Danfoss and ABB ACH550 models.

Energy consumption at the site has been reduced by 21{87a03eb4327cd2ba79570dbcca4066c6d479b8f7279bafdb318e7183d82771cf} since the works were completed.

The Cook and Phillip Aquatic and Fitness Centre

The retrofit undertaken at the Cook and Phillip Aquatic and Fitness Centre involved the installation of three 7.5 kW ABB variable speed drives to reduce the energy consumed by the chilled water pump and river jet pumps. Differential pressure sensors were also installed across the header (supply and return) to control the chilled water pump.

In addition, the VSDs that were already installed on the pool pumps were commissioned and tuned to run based on the flow rate from flow meters.

This involved Innotech MAXIM 1010 controllers being installed with the existing flow meters to control the required flow rate during daytime and night-time. The MAXIM 1010 Controller was installed to operate as a standalone device, using its own universal inputs, and analogue and digital outputs to receive information from the flow meter (4-20mA) and control the existing variable speed drives. The device was installed for a 50 metre pool and tuned to deliver 450m3/hr during day time (5.30 AM to 9.30 PM) and 350 m3/hr during night time (9.30 PM to 5.30 AM).

343 George Street

The retrofit of this government owned building on George Street involved installing variable speed drivers for two primary chilled water pumps, two condenser water pumps, two hot water pumps, two cooling towers, and seven air handling units, all with high level interface control from the building’s monitoring and controlling system. A differential pressure sensor was used to control the chilled water pumps and hot water pumps. The condenser water supply temperature to the chiller controls the cooling tower fan speed. In addition, all the air handling units are controlled by the high select of the temperatures with PID control between 40 to 50 Hz. Physical measurements were conducted to fix the minimum speeds of all the drives for different configuration of the pumps and fan operations to maximise efficiency without sacrificing performance.

Customs House

The variable speed drives in the building were configured to compare the return air temperature reading to its internal set-point in order to determine the speed of the fans. The VSD was set to provide the operating speeds between 40 and 50 Hertz.

The VSD PID (Proportional-Integral-Derivative) Control Logic continuously compares the return air temperature to the Internal Set point (24°C) and speeds up the fan towards 50Hz when the temperature is above the set-point. The PID then slow the fan towards 40Hz when the temperature is below the set-point. The sensitivity of the speed reaction is set by the PID1 Gain and Integral Parameter setting.

Total energy savings on the site since the retrofit have been around 28 per cent.

Victoria Park Pool

VSDs were installed on each of the two primary hot water pumps that serve the boiler and heat pump units at the Victoria Park Pool. The pumps are now controlled by the Carrier BMS system and run on a Duty/Standby basis which is rotated weekly. The operating pump speed is controlled to maintain a constant flow rate through the boiler and heat pump system whenever the pumps are called to run.

The existing VSDs on the three main pool circulation pumps were re-programmed to run at 45Hz. The pool staff have also modified operations to manually shutdown 1 pump each night from 19:45 – 05:45 to allow the filter to re-generate.

The VSDs used were Zener MSC-3 models.

307 Pitt Street 

Variable speed drivers were installed for the car park supply air fan and return air fan with a master and slave control arrangement respectively. Two CO2 sensors were directly connected to the VSD of the supply air fan and control the VSD speed from 20 Hz to 50 Hz based on the high select value of the CO2. Return air fan will be running at same Hz as supply air fan. The set point of the CO2 value is 10 ppm. This means that the fans will be triggered to run at higher speeds and circulate more air when the CO2 value is higher, while saving energy by running at lower speeds when CO2 is low. Differential pressure sensors were also installed across the supply and return pipe of the secondary chilled water header to control the VSDs of the secondary chilled water pumps.

540 George Street

At this site 7.5kW Vacon variable speed drives were installed on each of the two chilled water pumps of the air conditioning system. The pumps are controlled by the carrier BMS system and each pump serves a dedicated chiller, and is set to run when the chiller is required to provide cooling.

A differential pressure was also installed at the end of the chilled water pipe loop. This allows the VSDs to control the pump speed to maintain the chilled water system differential pressure set point (90kPa) and the chiller vessel’s design pressure drop set point of 30kPa + 20{87a03eb4327cd2ba79570dbcca4066c6d479b8f7279bafdb318e7183d82771cf} (Adjustable).

If both pumps are called to run they will operate at the same speed.

Additional efficiency measures:

A variety of other efficiency measures were employed throughout the retrofits. This included induction lighting being installed at the City’s recycling depot, to produce instantaneous and concentrated floodlight that triggers on and off with a movement sensor.

Across the whole portfolio, the City has introduced voltage power optimisation and is upgrading the power management system on personal computers. Other retrofit changes include efficient lighting retrofits, waterless urinals, water flow controls, and water recycling and recovery systems.

Combined with their HVAC and other pumping efficiency upgrades, these changes have added up to make a big difference.

 

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