Lumber Mill

An energy assessment for a Queensland lumber mill identified six energy reduction opportunities that could reduce the site’s energy consumption by 41% and reduce its energy costs by almost a third.

In 2019, the site consumed 3,566 megawatt hours (MWh) of energy. The assessment identified potential energy savings of 1,104.8 MWh and emissions reduction of more than 894 t CO₂-e. More than $100,000 a year could also be saved in energy costs.

Summary of Opportunities

LED Lighting

It is recommended that the manufacturer replace approximately 500 energy-intensive luminaires with LEDs. At present, high-intensity discharge mercury vapour, high-pressure sodium luminaries and T8 fluorescent lights are used. By replacing these with LEDs, the site could reduce its annual energy costs by $62,515 and achieve energy savings of 687 MWh each year. It would also significantly cut the site’s emissions by 556.4 t CO₂-e.

Quality LEDs offer distinct advantages over the older technology lighting, including:

• Much lower energy consumption for the same light output
• Better power factor
• Much longer lifetimes
• Less heat generation, which reduces consumption in air-conditioned spaces
• Option to purchase luminaires with integrated occupancy sensors to further reduce consumption

Dust Collector Optimisation

A large dust collection system is used on site to remove sawdust from the machines in the factory as they work. It was found that the system does not have enough capacity and the machines sometimes become clogged with sawdust. The site should consider correcting the issue, which may involve any or all of the following: reconfiguring the ducts to reduce pressure drop, replacing fans with worn blades to improve fan performance, adding capacity the system, etc.

Once the system problems have been corrected, fan speed controls could be installed to reduce the speed during periods of low demand. More than $27,000 in annual cost savings have been identified through this optimisation project. At a capital cost of $87,000, this results in a payback period of 3.2 years. This option would deliver a substantial reduction in emissions of 242 t CO₂-e.

Sawdust Blower

Currently, sawdust is transported to containers for shipment using a 15 kilowatt (kW) fan. This system takes 10-12 hours to fill a container.

A blower is a more energy efficient way to transport the sawdust, while also reducing the time needed to fill a container. A blower would save 44.2 MWh per annum of energy and $4,022 each year. The project offers a payback period of 7.5 years. Other options should be explored to reduce energy consumption, costs and loading time, and achieve a more favourable payback period.

To reduce power consumption and loading times, the manufacturer should also consider alternative methods of transferring sawdust, such as a sawdust conveyor or screw conveyor.

Hydraulic Motors Variable Speed Drives (VSDs)

Hydraulic systems are used on site used for moving and manipulating logs on conveyors or moving circular saws. The largest of these uses two 56 kW motors to power the hydraulic pumps. Hydraulic pressure is only needed for a few seconds every few minutes, so these systems typically operate on very low load for the majority of the time.

By installing VSDs, these motors could be turned down to a minimum speed and then ramped up when hydraulic pressure is needed. This has the potential to significantly reduce motor power consumption. An accumulator may then be required to provide pressure while the motors ramp up.

This project has the potential to capture $6,792 in annual energy savings and reduce consumption by 74.6 MWh each year. It offers a 4.9-year payback period. It would also reduce emissions by more than 60 t CO₂-e.

Power Factor Correction

Last year, the site installed a power factor correction system to improve the quality to power to the site, increasing the power factor from 0.8 to 0.9. It may be possible to further increase the power factor to 0.95, requiring an additional 150 kilovolt ampere (kVA) of correction. This is option is recommended as it offers the site a $10,130 annual cost saving and 2.9-year payback period.