How To Improve Efficiency Using Compressed Air Storage
With today’s ever-increasing focus on improving manufacturing efficiency and reliability, all aspects of the manufacturing process should be examined. Energy audits of manufacturing plants have shown that compressed air systems are often not the most efficient systems. However, increasing efficiency in one area of a compressed air system can improve your energy bill: compressed air storage.
When applied correctly, compressed air storage has been a tool used to increase the efficiency and reliability of compressed air systems. Compressed air storage when held at a higher pressure than the plant requires with a regulator it has the potential to supply large amounts of mass flow at an increased rate. As a result, this reduces the reaction time required of the compressors to high demand events. This then causes stability in pressure and a reduction of online power. As a result, this lowers operational and maintenance costs.
Despite these facts, compressed air storage is one of the most misunderstood and misused aspects of a compressed air system. Here, we look at some of the more common misconceptions of compressed air storage, and how you should instead approach using compressed air storage to improve system efficiency.
The Myths Surrounding Compressed Air Storage
Myth #1: Effective storage can be created by just adding storage tanks.
Installing air receivers in a compressed air system without outlining the purpose and results is a prescription for failure. Poorly designed compressed air storage is very common. While it may not negatively impact your compressed air system, it will result in little if any improved efficiency.
The Real Solution
To maximize the effectiveness of compressed air storage, it is necessary to measure the performance characteristics of the compressed air system. Measuring should take place in both the supply side and the demand side. Just adding additional storage volume, such as an air receiver without the creation of a useful differential, would create little storage and serve no real purpose. For example, a 10,000-gallon air receiver with only a 2 psi differential would only create 180 cfm of useful storage. Rather a 10 psi differential would create 900 cfm of useful storage for the same size receiver.
Myth #2: The more compressed air storage, the better.
There is some truth to this statement. Excessive compressed air storage is very seldom bad for the operation of a compressed air system. In fact, excessive storage applied to a system has the potential to reduce pressure fluctuations. This is a result of improving reaction time available to the supply side of the system in relation to demand-side requirements. However, the downside to oversizing storage in a compressed air system is the increased costs. This extends the pay-back period and may result in an unfeasible project.
The Real Solution
As stated earlier, it is better to measure and verify the performance characteristics of your compressed air system. As a result, you maximize the benefits and improve your return on investment. This can best be accomplished by having a quality compressed air system audit performed.
Myth #3: System piping replaces the need for air receivers.
System piping (headers, sub-headers, and drop legs) provides very little useful storage and is not as cost-effective as air receivers. For example, 1,000 ft of 4-inch piping has the volume equivalent of a 400-gallon air receiver. Obviously, it is far more cost-effective to install a 400-gallon air receiver rather than 1,000 feet of 4-inch piping. It is also difficult to create a meaningful pressure differential across system piping when you rely only on the natural pressure drop to create this differential.
The Real Solution
As mentioned previously, the small pressure differential that can be created results in very little if any meaningful storage. By contrast, air receivers coupled with Demand Regulation provide an opportunity to maximize storage by allowing the creation of greater pressure differential.
Myth #4: Certain types of air compressors do not require storage.
First, it is necessary to differentiate between the storage requirements of compressor controls verses that of the compressed air system. When addressing the needs of a compressor control, it is true that some controls require less storage than others. For example, when operating at high load levels, some compressor controls such as modulation, variable displacement, and variable speed benefit very little from what is considered a control or wet storage. Control or wet storage is considered storage between the compressor discharge and any clean up equipment. However, when these same types of controls operate at lower load levels (certainly below their turndown), control (wet) storage becomes critical to preventing short cycling.
The Real Solution
Compressor controls such as load/no load do require control (wet) storage, at virtually all load levels to reduce the possibility of short cycling, excessive oil carryover, and to increase the efficiency of operation.
The fact is that the system will always operate more efficiently with properly sized and applied storage. In fact, the type of the compressor control and the compressed air system requirements are different and should be considered separately.
Identifying the best compressed air storage for your compressor requires an audit of your system. If your company doesn’t have the resources for a full, in-depth audit, we can help! Give us a call or email, and we can schedule a time for an audit of your system.
Adapted From 2011 Satellite Newsletter Written By Ron Nordby