Brisbane Plastics Manufacturer

A Brisbane plastic tank manufacturer is a large energy consumer, using both natural gas and electricity. Through five identified energy and emissions conservation measures, the site can improve some of its existing processes, which will in turn provide greater productivity. These measures would also reduce energy consumption by 947 gigajoules (GJ) and cut greenhouse gas emissions by 65 tonnes of carbon dioxide equivalent (t CO₂-e). The simple payback period for these projects is 3.6 years.

With a 99 kilowatt (kW) solar PV system, the manufacturer could further decarbonise its operation and save another 437 GJ of energy. This size solar system is eligible for Small-scale Technology Certificates (STCs), reducing the upfront cost of the solar investment.

Summary of Opportunities

Lighting Upgrade

While the replacement of old lights with LEDs has progressively occurred at the site, about 20 metal halide high bay lights and some flood lights remain. With a lighting layout redesign, these could be replaced with a similar number of 100-75 watt (W) LEDs, starting with the lights that run for 20 hours each day. Occupancy sensors should also be used in areas with low occupancy. This project would cost $10,971 and have annual energy savings of $1,453. It would also reduce emissions by 12 tonnes of CO₂-e.

Compressed Air Leak Survey

An ultrasonic leak survey and effort to reduce waste compressed air usage would result in energy savings for the manufacturer. It is likely that by repairing compressed air leaks, the site would be able to reduce the system’s pressure set point to the minimum operating pressure. This option would offer energy savings of 33 GJ a year and, at a cost of $6,000, would achieve a payback period of 6.3 years.

Rotomoulding Temperature Controls

The current temperature setting for one of the internal moulds is 303° C, which is higher than the optimal temperature setting. A temperature control system could be utilised for the clamshell oven to control the oven’s temperature based on the temperature within the mould. This require a resistance temperature detector (RTD) which connects to the control panel. This intervention would ensure a higher quality product, less wastage and potential energy savings as it will prevent over heating of the oven.

The assessment found that emissions would reduce by 24.9 t CO₂-e, and annual energy savings of $17,359 and 484 GJ would be achieved. The capital cost of the project is $60,000, delivering a 3.5-year payback period.

Rotomoulding Air Pre-Heating

The site’s one polymer rotomoulding machine, used for polymer heating into pre-defined moulds, operates at 300° C. It uses natural gas as its main energy source and vents most of its heat out of its flue - which goes into the environment as wasted heat. A new economiser would be able to use the flue gases from the unit to pre-heat the combustion air prior to it being used in the oven.

It is estimated that this option would deliver a 6.5% energy saving if the combustion air can be pre-heated to 168°C. In addition to fuel savings, this reduction in combustion air would save on the electricity used for fans.

This opportunity presents a significant energy saving of 372 GJ a year and annual energy cost savings of $13,137. It would also reduce greenhouse gas emissions by 19 t CO₂-e.