Fertiliser Manufacturer

A Queensland-based fertiliser and industrial chemicals manufacturer has a North Queensland transport and warehousing facility that connects rail delivery to sea and road freight. The facility has two sites that together consume more than 3161 gigajoules (GJ) of energy, although one of the sites uses significantly more energy than the other.

An energy assessment found that through three energy efficiency measures, the facility could reduce its energy consumption by 722 GJ per annum and realise $68,521 each year in energy and other cost savings, with a simple payback period of 2.8 years. The three measures would realise greenhouse gas (GHG) savings of 162 tonnes of carbon dioxide equivalent (t-CO₂-e).

Two solar options were also explored, with a 160 kilowatt (kW) system recommended due to its significant greenhouse gas savings of 202 t-CO₂-e.

Summary of Opportunities

Variable Speed Drives for Conveyors

Conveyor motors at one of the manufacturer’s sites contributes almost all of the site’s peak demand and almost 69% of the site’s total energy use. Currently, these motors are controlled using Direct On-Line controls with a delay relay to prevent all motors from starting at the same time and limiting the start-up surge current so that the main switch can tolerate the load.

Variable speed drives (VSDs) are recommended to replace the existing control system to send variable frequency signals to the conveyor motors. Some advantages of VSDs for the motors are:

• To limit the start-up current without the use of resistors, allowing start times to be automated if required
• To provide smoother motor start-up profiles with less electromotive force, resulting in less wear and tear
• To allow the site to vary the speed of the motor (and therefore the speed of the conveyor)
• To significantly reduce the inductive effects of the motors on the site’s power factors, providing substantial demand savings without requiring major power factor correction equipment.

This option has the highest capital cost of the energy efficiency measures at $179,700, however, with energy cost and demand savings of $53,353 per year, this option has a simple payback period of 3.4 years. Significantly, this option would reduce energy consumption by 569 GJ per year and result in GHG savings of 128 t-co₂-e.

Accelerate Lighting Upgrade

Large sections of one of the warehousing sites uses inefficient metal halide and sodium vapour floor lights and high bays. While gradually being replaced with new LED luminaires, an accelerated transition is recommended to improve the site’s energy performance and indoor light quality. LED luminaires have several advantages over older technology, including:

• High luminous efficacy (light output per unit of power input).
• Higher colour rendering index, allowing for colours to be more easily distinguished. This has the potential to increase site safety as yellow and orange high visibility will have a sharper contrast.
• Longer lifetimes of >50,000 hours (compared to 20,000 to 30,000 hours for the older technology). This will produce significant maintenance cost savings given the difficulty in accessing these luminaires.
• Ability for occupancy sensors to be built in to maximise energy savings when the area has zero occupancy.

 At a capital cost of $14,500, this option has a simple payback period of 1.3 years and will save 40,329 kilowatt hours per annum (kW/h p.a.) of electricity and $4,978 in energy costs. It would achieve GHG savings of 33 t-CO₂-e.

Compressed Air Optimisation

One of the sites has two air compressors, each nearing the end of its rated life. While still operational, the compressors are expected to significantly degrade over the next five years, leading to increased energy and maintenance costs.

The compressors are likely operated on a lead/lag configuration, and each at a fixed speed. This configuration was commonly used before VSDs became feasible. Due to a lack of operating data, the cycling of each of the compressors could not be determined, and therefore energy savings could not be quantified.

It’s recommended that the manufacturer monitor maintenance costs and replace the compressors with a single VSD air compressor when repair costs become significant. A VSD controlled air compressor would vary the speed to meet the varied compressor requirements, thereby reducing energy demand. It would also have lower maintenance costs and operating temperatures.

In the short-term, it is recommended that bends in the compressed air delivery line are reduced through simple modifications. This would reduce pressure loss in the system. This cost-effective improvement would cost $500 and achieve electricity savings of 2,176 kWh per year.

Battery Storage

Energy storage has a range of potential incentives for businesses, including:

• Sizing equipment to meet the load and using storage to ride out peaks and troughs
• Time shift energy use from peak to off-peak times
• Take advantage of opportunities to participate in Demand Response schemes
• Reduce the likelihood of brown-outs and black-outs

Battery storage was considered for both sites.

At one site, based on its current load, a 420 kW/840 kWh battery would save $42,111 a year based on 2021 tariffs. These low savings are due to the need for the battery to be limited to discharging at 280 kW to ensure it has sufficient energy stored to support the overlap between ship loading and train unloading at the site.   

Given the nearly $400,000 cost of the solution, this battery option is not financially viable at this point in time.

At the second site, the demand duration curve is flat, with the site operating at peak level most days for extended periods of time. This means peak lopping is not possible. To reduce the peak load, battery storage capacity would need to be disproportionately large compared to power output, making it unfeasible.

It is recommended that batteries be reconsidered for demand management when battery prices have fallen further in future years.