Waupaca Foundry, Inc.: Plant 1 Compressed Air System Optimization


Waupaca Foundry is a supplier of cast and machine iron components for automotive, off-highway, commercial vehicle, and other industrial markets. Waupaca operates five iron foundries with 1.4 million tons of capacity, as well as machining and casting finishing operations in the United States. 


Compressed air is a significant energy use for the iron casting supplier. At its gray iron foundry, Plant 1 located in Waupaca, WI, compressed air represents 10% of the facility’s annual electricity usage. Plant 1 faced the challenge of maintaining reliable and consistent air pressure and avoiding over-utilizing compressed air-driven equipment in the plant. To improve system efficiency and performance, Plant 1 conducted an extensive compressed air audit and system optimization project, identifying measures to maximize the system’s efficiency and reliability. As a result of the projects implemented, Plant 1 improved the overall operation and maintenance of its compressed air system and improved system-level energy efficiency by 13.5%.



Through a comprehensive audit, Plant 1 identified a portfolio of measures to improve the overall efficiency of the plant’s compressed air system. The Compressed Air Optimization Project included the following measures:

  1. Supply Side (performed by the Waupaca Foundry Energy Team and Compressor Vendor)
  • Replaced twp legacy trim water-cooled compressors with one new air-cooled unit witha a variable frequency drive (VFD).
  • Installed a Master Control System and flow regulation control. 
  • Optimized the piping configuration in the compressor rooms. 
  • Implemented Waste Heat Recovery to offset the facility’s natural gas usage during the winter.
  1. Demand side (performed by the Waupaca Foundry Energy Team & Maintenance)
  • Reduced overall compressed air system pressure. 
  • Implemented end-use reduction projects; e.g., leak repair. 
  • Tuned up large end-users through demand-side management strategies. 
  1. Best Practices (performed by Waupaca Foundry Energy Team & a third-party auditor)
  • Performed a system assessment to identify energy reduction opportunities.
  • Improved the plant’s air-leak management program. 

The compressed air optimization project at Plant 1 improved system reliability to meet foundry operational needs, and significantly improved the system’s energy efficiency. The project cost was $325,000 with associated reductions of approximately 1,100,000 kWh of electricity, 6,750 MMBTU of Natural Gas, 13 Million Gallons of water, and total cost savings of $185,000 per year. The simple payback for this project was 1.24 years, factoring in energy rebates received from the state energy efficiency program, which paid the equivalent of 28% of the project cost.



Waupaca is using Plant 1’s success as a reference project to provide guidelines for compressed air system project optimization across all its facilities. The project continues to deliver financial and operational benefits for the plant. Key performance benefits include the ability to match compressed air generation with production schedules; reduced compressed air plant pressure from 95 psi to 87 psi; using waste heat from the compressors to offset natural gas usage; and reducing water usage by upgrading from pass-through water-cooled systems to an air-cooled compressor. The project also enables real-time monitoring of one of the largest energy consumers in the facility, which includes alarms and notifications to the maintenance department for early fault detection. 


Waupaca’s Energy Team is following an ongoing air leak management program to control air leaks, yielding an annual cost avoidance of $225,000 annually. One example activity is that employees are able to take a picture when they come across a compressed air leak and report it to the Energy Team. Additionally, Waupaca plants continuously implement end-usage reduction projects to eliminate or reduce compressed air usage, as compressed air is the most expensive utility, representing approximately 10% of total energy usage at each location. Multiple plants across Waupaca’s portfolio are now budgeting compressed air system upgrades into their capital project planning. Plant 4 is developing an engineering study to design a new compressor system for their plant. Plant 7E recently commissioned a new compressed air system and Plant 23 is currently installing a master control system to optimize compressed air production in their 17-compressor unit system. Finally, Plants 5 and 6 are prioritizing compressed air project implementation, with system upgrades included in their FY2022 and FY2023 budgets.


Annual Energy Use

Baseline (2015)
100 kWh
Actual (2020)
87 kWh

Energy Savings:

1,100,000 kWh

Sector Type



Waupaca, Wisconsin

Financial Overview