The 3 kEys
- Right-size your system, and utilize optimal loading strategies
- Use energy-efficient air nozzles and jets, and repair air leaks promptly.
- Implement automatic shutoff systems to prevent unnecessary usage. It doesn’t matter how efficient or inefficient your system is if it’s off.
Compressed air systems are the lifeblood of many industrial operations, powering tools, driving machinery, and performing essential functions across various types of production facilities. They’re also notorious for their high energy consumption and operating costs, as they can account for up to 30% of a facility’s energy expenses. With such a significant impact on operating budgets, optimizing these systems is not just a good idea—it’s a necessity.
We’ll explore the essential aspects of compressed air systems here, focusing on energy efficiency, operational strategies, and cost saving opportunities.
The Energy and Cost Impact of Compressed Air
Compressed air is a vital utility, but it’s also one of the most expensive forms of energy in industrial operations. The operating costs for compressed air can range from 20 to 40 cents per 1,000 cubic feet, representing a considerable expense for facilities that rely on it heavily. This highlights the critical need for efficient management of these systems to reduce costs and improve overall productivity. See Energy Efficiency Reference Guide published by the government of Canada for a breakdown on costs and savings comparisons.
Key strategies for reducing energy consumption include optimizing system pressure, implementing leak detection and repair programs, ensuring proper system sizing, as well as implementing efficient loading strategies. As leaks in particular can account for substantial energy losses, addressing these issues through dedicated maintenance efforts can reclaim lost resources and enhance overall system performance.
Here’s a quick outline of strategies that can be deployed:
On-Off Control
For intermittent demand, on-off control is a straightforward yet effective strategy. Compressors can start and stop based on pressure switches or manual operation, saving energy in processes where continuous usage is less than 50% of capacity.
Again, it doesn’t matter how efficient or inefficient your system is if it’s off.
Optimizing System Pressure
Lowering the operating pressure of a compressed air system by just 2 psi can yield a 1% reduction in energy usage, translating into significant cost savings over time. Consider, for example, how much less pressure a plant would require if it converted all power tools from pneumatic to electric, a more efficient
approach to getting the work done, and for a reasonable expense. The U.S. Department of Energy has a number of tip sheets available, including on the optimization of system pressure.
Leak Management: A Quick Win for Energy Efficiency
One of the simplest and most effective ways to improve the efficiency of compressed air systems is by addressing air leaks. Leaks can waste 20-30% of a system’s total output, forcing compressors to work harder and increasing energy consumption. There are at least three benefits to putting this problem at the top of the Facilities Manager’s priorities:
Energy Waste. The high cost of generating compressed air means that even small leaks can lead to substantial energy losses.
Operational Efficiency. Excessive strain on compressors due to leaks accelerates wear and tear, reducing equipment lifespan and reliability.
Environmental Impact. Repairing leaks not only saves energy but also reduces the carbon footprint associated with electricity generation, particularly when fossil fuels are involved.
If you want to get a little geeky with potential leak savings formulas and calculations, take a look at this: Maintenance and Engineering’s Article. I’d dive into that, big time.
Right-Sizing and Loading Strategies
By adopting variable-speed compressor designs, facilities can cut the energy costs of a single compressor operating at 60% load in half. And in multi-compressor systems environments, optimized load-following and supply-demand matching can further enhance savings.
Base Load Compressor. Running multiple compressors at full capacity ensures stable performance while reducing inefficiencies associated with varying loads. The base load compressor handles the lowest level of pressure necessary.
Trim Compressor. A trim compressor is used to handle fluctuations in demand, ensuring the system remains efficient even as air needs vary.
In two-compressor systems, pairing different types of compressors can optimize performance:
Rotary-Screw or Centrifugal Compressors. Ideal for steady, high-volume demands, these compressors are efficient for base-loading operations.
Reciprocating Compressors. These are more suited for part-load conditions, thanks to their ability to adjust output flexibly to meet demand changes.
Compressor Location
Optimum compressor placement is essential for maintaining efficiency and longevity. High temperatures can increase energy consumption and the risk of equipment failure, leading to costly repairs. To optimize performance, position compressors in a dry, clean, and cool environment with adequate airflow. Ensure there is sufficient space around the unit for proper ventilation and easy access for maintenance.
If necessary, install additional cooling or ventilation systems to regulate temperature and prevent overheating.
Throttling and Guide Vane Positioning
Throttling adjusts the discharge or suction valves of compressors to modulate output. Here’s a breakdown of methods:
Discharge Throttling. The least efficient method, as it wastes transportation energy.
Suction Throttling. Slightly more efficient than discharge throttling, but still results in energy loss.
Speed Control. The most energy-efficient method, where small reductions in speed result in large power savings due to the cubic relationship between speed and power.
Guide Vane Positioning. Though less efficient than speed control, guide vanes allow for significant turndown and are useful in certain scenarios.
Variable Frequency Drives
Adding Variable Frequency Drives (VFDs) to your compressor system can significantly enhance efficiency. As they adjust the motor speed based on real-time demand, eliminating unnecessary energy usage during low-load periods. This results in lower power consumption, reduced peak demand charges, and improved overall system efficiency. Unlike traditional compressors that run at full capacity regardless of need, a VFD-equipped system dynamically adapts, minimizing energy waste and optimizing performance. According to a study by the Compressed Air and Gas Institute (CAGI), upgrading to a VFD compressor can yield energy savings of up to 35% compared to a fixed-speed compressor.
Beyond energy savings, VFDs also reduce mechanical stress on the compressor by providing a soft start, which lowers inrush currents and decreases wear on motor components. Additionally, by maintaining more stable pressure levels, VFDs improve system reliability and air quality, ensuring consistent performance in industrial applications.
Waste Heat Recovery
Industrial air compressor heat recovery systems have become more prevalent and easier to integrate, significantly improving energy efficiency and sustainability across various industrial processes and plant heating applications that utilize the heat-of-compression generated by air compressors.
Traditionally, waste heat from compressors is released into the atmosphere, leading to energy losses. Advancements in heat recovery technology now enable the effective capture and reuse of this heat for applications such as space heating, water heating, and preheating air for other industrial processes. By incorporating heat exchangers and efficient heat transfer mechanisms, these systems can reclaim up to 90% of wasted heat, transforming an energy loss into a valuable resource.
The above is just a start. As you know, once you commit to the energy consumption exploration with a particular goal in mind, the more opportunities you’ll find, and the more savings you’ll ultimately realize.
Start with a percentage reduction goal, and go and get it!
