Industrial Parts and Products

An assessment of a South East Queensland Industrial parts and products manufacturer’s 8,500m² facility identified improvements to gas furnace and compressed air systems that would reduce annual energy consumption and deliver valuable energy cost savings. The site also has a large roof suitable for a 300 kilowatt (kW) solar photovoltaic (PV) system that could provide over 70% of the site’s electricity load during peak solar energy production. A financial analysis of the opportunities is presented in the following table.

Summary of Opportunities

Gas Furnace Efficiencies

Through an energy assessment, key improvements to the gas furnace were identified which would improve energy efficiency and reduce the manufacturer’s energy-related operating costs. The recommended options are:

• Introduce a variable speed control to the furnace’s gas burner to remove the need for mechanical control. Mechanical control of fuel and air flow from the burners sees its moving parts wear out, affecting the control of air-to-fuel ratios.
• Improve efficiencies by installing an oxygen trim system, which measures the excess oxygen in the flue gas, detecting the loss due to unburnt fuel. The system controls fuel and air to decrease this loss and shift the boiler to the maximum efficiency zone. This option would see a reduction in annual energy consumption of 247,300 kilowatt hours (kWh) and cost savings of $28,954, with a payback period of 3.1 years.
• Install an air-to-air economizer (850 kW unit) on the gas furnace flue that will act as a heat exchanger to recover the lost heat from the furnace flue and use it to pre-heat the combustion air – reducing the required gas energy input to the furnace by an estimated 169.8 megawatt hours (MWh) and annual cost savings of $20,070. This presents a payback period of just 2.1 years.

Air Compressors

Air compressors consume the most energy at the site, accounting for 150 kW of the site’s 400 kW weekday peak load. A range of solutions have been identified to drive down consumption and costs, each with a payback period of between 0.2 to 4 years.

The recommended options are:

• Install a variable speed drive (VSD) compressor system to replace an older 75 kW Kaeser CSD air compressor system. A VSD has the following advantages: output exactly matches the demand; high efficiency motors; a constant supply pressure; and much improved efficiency at part load conditions. While this has the highest CAPEX of the air compressor recommendations at $54,000, with annual cost savings of $13,594 it offers a reasonable payback period of 4 years.
• Install improved reticulation and optimised pipe diameters to reduce pressure drop, replacing the current 110-150 mm PVC pipework. This is a low-cost solution at $500 (capital expenditure) that could deliver savings of $2,582 in annual energy costs.
• As the site assessment found many compressed air leaks, regular compressed air leak surveys using an ultrasonic detection device are recommended, to promptly repair any leaks. These leaks are commonly identified across many manufacturers’ facilities.

Solar

The manufacturer uses both electricity and gas, however electricity constitutes a significant proportion of the overall energy consumption. Engineers explored options to install solar to improve energy independence and reduce carbon emissions.

The assessment found that a 300 kW solar PV system is feasible for the manufacturer, with the site having a suitable size roof for the installation. There is sufficient load to justify a larger system, however, as the business operates Monday to Friday, the system would export to the grid over the weekend, which may be unacceptable to the network provider. Therefore, this system has been sized to achieve the optimum avoidance of grid electricity use while maximising the return on the investment.

The simple Levelised Cost of Energy calculated for this renewable energy project is 6.2 cents/kWh. When compared with the current average blended energy usage rate of $ 0.127 / kWh, the option of 300 kW is considered feasible.