Victoria’s State Library reaps the benefits of energy efficient technology

Over the last ten years the push for energy efficiency has been rapidly gathering momentum, particularly in relation to productivity improvement and reduction of carbon emissions.

During a recent visit to Australia from Low Voltage Drives headquarters in Finland, ABB group vice president, Pekka Tiitinen, pointed out that 65 percent of all energy consumption at industrial sites goes through motors, and that the biggest challenge is ignorance of the scope for savings.

ABB is considered a world leader in the development of energy efficient motors, drives and control systems.

"Some 50 percent of carbon reduction comes from energy efficiency improvement from renewable energy and other non-fossil, plus carbon capture storage," he said.

"Australia is a front runner in legislating for energy efficiency and recognising the benefits of energy appraisals for industry and large buildings.

In industry, cost/benefit analysis demonstrates that big savings of up to 50 percent can be achieved, with payback typically in one to two years and sometimes even five to eight months.

"The easiest way to add more electricity capacity, is to improve the energy efficiency that would release existing capture in new consumption. Nowadays, more and more systems are playing a key vital role in that."

Energy saving technology

According to ABB‘s senior vice president in Australia, Jussi Rautee, significant productivity improvement and environmental benefits are being achieved in Australia through conduct of energy appraisals and the installation of energy saving technology.

The State Library of Victoria was founded in 1854 and is a reference and research library for over one million visitors a year.

It holds more than two million books and occupies an entire city block of two hectares, comprising reading rooms, galleries, exhibition spaces, conference centre and cafe.

Jussi says that an energy appraisal carried out at the library concluded that significant energy savings could be made by replacing the existing HVAC flow control, which used throttling valves, with variable speed drives.

"The library has four water-cooled chillers with eight motors ranging from 15 to 55 kW; five cooling tower fans with one 11 kW motor each; and two gas-fired heating boilers with one 22 kW and one 30 kW motor on the hot water circulation pumps," he said.

"The chillers were running with 50 to 60 percent throttling at the discharge end, as well as across the evaporator and condenser vessels. Now, the same flow is produced without throttling but with motor speed reduced to between 75 percent and 90 percent of full speed.

"In addition, the five cooling tower fans were controlled by continuous starting and stopping of the single speed motors, running approximately five minutes each. These motors now run continuously at approximately 50 percent speed."

Significant benefits

Jussi advises that by using 15 ABB standard drives for HVAC, from 5.5 kW to 55 kW, energy savings of between 30 to 60 percent were achieved across the various applications.

"With combined motor ratings of 400 kW and 24/7 plant operation, the total energy consumption was reduced by 1,800 MWh annually, saving the library nearly $60,000 per year. Payback, including maintenance savings, was achieved in just 14 months," he said.

"It should be pointed out that oversizing is the norm in most HVAC installations. The expected load is usually known when the system is designed. However, there are many other factors that are not known, such as the resistance of the new pipe work.

"Also, users often want to allow for possible future expansion. For these reasons, specifiers tend to design systems slightly larger than needed. However, an oversized HVAC system uses more energy than is needed to control the indoor climate.

"The variable speed drive can give the over-capacity back to you in the form of energy savings, instead of wasting the excess energy through the use of throttling valves. The installation of drives optimises the energy performance."

The main source of potential emissions reductions.

The image above illustrates the main source of potential emissions reductions. (Graphic courtesy: ABB)

Mike Brown, maintenance engineer at the State Library of Victoria, says he was surprised by the large savings that could be achieved by reducing the speed of fan and pump motors by just a little.

"In the past we only used AC drives to control speed when we wanted a specific flow rate. Through the energy appraisal, I became aware that great energy savings could be achieved as well," he said.

Improved efficiencies

"Working with energy efficiency can be a challenge in an old building. No matter how hard we try to raise efficiency, it will never match a modern building. The library is 150 years old and heritage listed," said Brown.

"Its large halls with high ceilings make it difficult to air-condition. Some of the walls are a metre thick which makes it hard to achieve the desired temperature.

"Under these conditions, using AC drives is a useful way to save energy where we can. It also helps us control conditions accurately – the temperature needs to be controlled to 22 degrees and the humidity to 50 percent to protect manuscripts, paintings, and the two million books in the library.

"The system has exceeded expectations. It has been very reliable and produced massive savings in energy and maintenance that will be reaped in the coming years."

In summary, the introduction of AC drives has eliminated energy waste caused by oversizing of the existing HVAC system and subsequent throttling, and has delivered substantial improved efficiencies.
For example, the accurate pump speed control offered by the AC drives has improved the chiller compressor’s efficiency.

For each degree the return water temperature deviates from the design temperature, the compressor becomes 1.5 percent less efficient.

Circulating cooling water at the optimum speed means less energy is needed to run the compressor.
Also, precise AC drive control provides more accurate fan control in the cooling towers and has significantly cut noise pollution from the fans, thereby eliminating disturbance for library visitors and improving living conditions in nearby residential blocks.

In addition, maintenance is reduced compared to stop-start control, as the drives’ soft-starting reduces wear of motor bearings and fan belts.

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