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Compressed Air Energy Storage (CAES)

Compressed Air Energy Storage (CAES) is a way to store energy generated at one time for use at another time. At utility scale, energy generated during periods of low energy demand (off-peak) can be released to meet higher demand (peak load) periods. Compression of air generates a lot of heat. The air is warmer after compression. Decompression requires heat. If no extra heat is added, the air will be much colder after decompression. If the heat generated during compression can be stored and used again during decompression, the efficiency of the storage improves considerably. There are three ways in which a CAES system can deal with the heat. Air storage can be adiabatic , diabatic , or isothermic : Adiabatic storage retains the heat produced by compression and returns it to the air when the air is expanded to generate power. This is a subject of ongoing study, with no utility scale plants as of 2010. Its theoretical efficiency approaches 100% for large and/or rapidly cycled devic

Theory of air compression 2

An air compression is a means by which one type of energy is converted to another. During this conversion certain losses occur because of the rise in temperature of the air as it compressed. In general practice, the air is stored in a receiver and heat is lost both in the receiver and pipe lines running to equipment. Since the rise in temperature of the air is a direct loss of energy. We want to keep it down to a minimum. The ideal method is to compress air isothermally but this is impossible in practice owing to lack of time necessary to affect transfer. Water jackets and inter-cooling can be used to keep the temperature down. These have the effect of reducing the compression index (n) to something less than 1.4. When air is compressed to a pressure to exceeding about 4 bar it is usual to compress it in stages, with intercooling between each stage. This considerably reduces the total amount of work required on the air. For two stages compressing, the air is compressed in the first

Theory of air compression

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Air is not a perfect gas but for practical purpose the laws relative to perfect gases may be applied to it. Boyle’s law states that: The absolute pressure of a gas varies inversely as the volume, provided the temperature remains constant. p V = a constant where: p = pressure in bar, V = volume in m 3 . Charles’ law states that the volume of a gas under constant pressure, or the pressure of a gas under constant volume, varies as the absolute temperature. Therefore V varies as T, and p varies as T where T is the absolute temperature. If the two laws are combined, we get: p V / T = constant The constant is usually denoted by R and therefore: p V = R T It can be shown that the value of the constant R applicable to air is 287.0 J/(kg K). The relation between the pressure and volume of air during its expansion and compression may be represented by: p V n = R T where ‘n’ has value which depends on the addition or subtraction of heat during the process . When the te

Opportunity of Compressed Air Savings

Approximately 10 % of all electrical power used in industry comes from compressed air. This is proof of its widespread usage but it is also evidence of the potentially large saving in costs which could be achieved if the energy management opportunities are put into practice. Normally, the purpose of compressed air systems in the industrial sectors is to deliver the necessary volume of air at the required pressure and temperature to the correct places. Compressed air is used for operating pneumatic equipments, cleaning purposes, and other general services. This is accomplished by a distribution system consisting of pipes, valves and fittings. The Compressed Air pipe work is arranged in the form of ring mains with interconnections to points of end-users. Careful evaluation of existing compressed air systems can ensure against improper operation, and poor energy utilization. Alert design, operations, and maintenance personnel, with an awareness of energy management, can achieve signif

Compressed Air System Energy-Reduction Case Study (Part 2)

Let's continue from [ Compressed Air System Energy-Reduction Case Study (Part 1) ] Compressed Air Energy-Reduction Strategy Project Goals and Implementation Following the IAC assessment, FUJIFILM’s maintenance team formulated project goals and an implementation plan that centered on the utilization of existing facility infrastructure and equipment. The team’s implementation strategy was divided into three phases and focused on increasing the system’s storage capacity to handle production peaks and valleys; lowering air compressor operating pressure; repairing system leaks; and ultimately, operating the facility with one compressor. The team’s strategy was also aided by the company’s closure of its Orange Park, Florida, operations. This facility housed a 75 horsepower (HP) air compressor, a dryer, and a receiver, which the Dayton facility incorporated into its efforts. Project success, then, depended on the accomplishment of four specific goals: To increase system redundanc

Compressed Air System Energy-Reduction Case Study (Part 1)

FUJIFILM Hunt Chemicals U.S.A. Achieves Compressed Air System Energy-Reduction Goals with a Three-Phased Strategy. In an attempt to eliminate equipment failures and downtime issues associated with the plant’s compressed air system, FUJIFILM Hunt Chemicals U.S.A.’s in-house maintenance team worked with a team of faculty and students from the Tennessee Technology University Industrial Assessment Center (IAC) to conduct an assessment at its Dayton, Tennessee, facility to identify opportunities for improvement. Following the assessment, the team formulated an implementation plan that would increase the system’s reliability, reduce system maintenance costs, reduce the facility’s overall energy use, and eliminate the use of nitrogen when compressed air systems are down. The Energy Situation The Dayton facility was experiencing excessive downtime due to chronic air compressor failures and significant inefficiencies throughout its compressed air system. In 2007 alone, system operating costs

Stabilizing System Pressure

Stabilizing system pressure is an important way to lower energy costs and maintain reliable production and product quality. The need to stabilize system pressure should be guided by the compressed air demand patterns and the minimum acceptable pressure level required for reliable production. High-volume intermittent air demand events can cause air pressure to fluctuate, which is often misinterpreted as insufficient pressure. In some cases, improperly set compressor controls will cause another compressor to start, but because of the time required for the new compressor to ramp up, there will be a shortfall of air supply to the system. Such a delay can cause the system pressure to decay, resulting in lost production. Three methods can be used to stabilize system pressure: adequate primary and secondary storage, Pressure/Flow Controllers (P/FCs), and dedicated compressors. Primary and Secondary Storage One or more compressed air applications having large, intermittent air demands can

Remove Condensate with Minimal Air Loss

Removing condensate is important for maintaining the appropriate air quality level required by end uses. However, significant compressed air (and energy) losses can occur if condensate removal is done improperly. Excess compressed air loss during condensate removal can occur due to several factors. Following shows several condensate removal methods and the characteristics of each method. Manual operation: Operators manually open valves to discharge condensate. Depends on people opening valves at the appropriate time for the necessary amount of time. Often leads to excess loss because air escapes when the valves are left open to drain the condensate. Level-operated mechanical float traps: Use a float connected by linkage to a drain valve that opens when an upper setting is reached and closes when the drain is emptied. Require considerable maintenance. Are prone to blockage from sediment in condensate. Are prone to getting stuck in open position (leak excess air) and in the

Preventive Maintenance Strategies for Compressed Air Systems

A brewery neglected to perform routine maintenance on its compressed air system for years. As a result, two of its centrifugal compressors, whose impellers had been rubbing against their shrouds, were unable to deliver the volume of air they were rated for and one of those units had burned up several motors during its lifetime. In addition, plant personnel did not inspect the system’s condensate traps regularly. These traps were of a type that clogged easily, which prevented the removal of moisture and affected product quality. Also, the condensate drains were set to operate under the highest humidity conditions, so they would actuate frequently, which increased the system’s air demand. As a result, energy use was excessively high, equipment repair and replacement costs were incurred unnecessarily, and product quality suffered. All of this could have been avoided through regular maintenance. Like all electro-mechanical equipment, industrial compressed air systems require periodic mai

Maintaining System Air Quality

"Maintaining the proper air quality level is essential for keeping compressed air energy costs down and to ensure reliable production." Poor air quality can have a negative effect on production equipment and can increase energy consumption and maintenance needs. The quality of air produced should be guided by the quality required by the end-use equipment. The air quality level is a function of the levels of particulate, moisture, and lubricant contaminants that the end uses can tolerate. Such air quality levels should be determined before deciding whether the air needs additional treatment. Compressed air should be treated appropriately but not more than is required for the end-use application. The higher the quality, the more the air usually costs to produce (in terms of initial capital investment in equipment, energy consumption and maintenance). Once the true end-use air quality requirements have been determined, the proper air treatment equipment can be configured. Se

Engineer End Uses for Maximum Efficiency

Compressed air is one of the most important utility requirements of many industrial manufacturing plants because it directly serves processes and applications such as pneumatic tools, pneumatic controls, compressed air operated cylinders for machine actuation, product cleansing and blow-off applications. Ensuring an appropriate, stable pressure level at the end-use applications is critical to the performance of any industrial compressed air system. End uses that are engineered for maximum efficiency can help provide the consistent supply of compressed air that ensures reliable production. To ensure the efficiency of compressed air end-use applications, a number of steps should be taken: Review the pressure level requirements of the end-use applications. Those pressure level requirements should determine the system pressure level. Because there is often a substantial difference in air consumption and pressure levels required by similar tools available from different manufacturers,

Eliminate Inappropriate Uses of Compressed Air

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Compressed air generation is one of the most expensive utilities in an industrial facility. When used wisely, compressed air can provide a safe and reliable source of power to key industrial processes. Users should always consider other cost-effective forms of power to accomplish the required tasks and eliminate unproductive demands. Inappropriate uses of compressed air include any application that can be done more effectively or more efficiently by a method other than compressed air. The table below provides some uses of compressed air that may be inappropriate and suggests alternative ways to perform these tasks. Potentially Inappropriate Uses could be replaced by following suggested alternatives: Clean-up, Drying, Process cooling: Low-pressure blowers, electric fans, brooms, nozzles Sparging: Low-pressure blowers and mixers Aspirating, Atomizing: Low-pressure blowers Padding: Low to medium-pressure blowers Vacuum generator: Dedicated vacuum pump or central vacuum system Pers

Effect of Intake Air on Compressor Performance

The effect of intake air on compressor performance should not be underestimated. Intake air that is contaminated or hot can impair compressor performance and result in excess energy and maintenance costs. If moisture , dust , or other contaminants are present in the intake air, such contaminants can build up on the internal components of the compressor, such as valves, impellers, rotors, and vanes. Such build-up can cause premature wear and reduce compressor capacity. "When inlet air is cooler, it is also denser. As a result, mass flow and pressure capability increase with decreasing intake air temperatures, particularly in centrifugal compressors." This mass flow increase effect is less pronounced for lubricant-injected, rotary-screw compressors because the incoming air mixes with the higher temperature lubricant. Conversely, as the temperature of intake air increases, the air density decreases and mass flow and pressure capability decrease. The resulting reduction in

Determining the Right Air Quality for Your Compressed Air System

Knowing the proper air quality level required for successful production is an important factor in containing compressed air energy and other operating costs, because higher quality air is more expensive to produce. Higher quality air requires additional air treatment equipment, which increases capital costs as well as energy consumption and maintenance needs. The quality of air produced should be guided by the degree of dryness and filtration needed and by the minimum acceptable contaminant level to the end uses. Level of Air Quality: Plant Air Applications: Air tools, general plant air Level of Air Quality: Instrument Air Applications: Laboratories, paint spraying, powder coating, climate control Level of Air Quality: Process Air Applications: Food and pharmaceutical process air, electronics Level of Air Quality: Breathing Air   Applications: Hospital air systems, diving tank refill stations, respirators for cleaning and/or grit blasting Compressed Air Contamina

Determine the Cost of Compressed Air for Your Plant

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Most industrial facilities need some form of compressed air, whether for running a simple air tool or for more complicated tasks such as the operation of pneumatic controls. A recent survey by the U.S. Department of Energy showed that for a typical industrial facility, approximately 10% of the electricity consumed is for generating compressed air. For some facilities, compressed air generation may account for 30% or more of the electricity consumed. Compressed air is an on-site generated utility. Very often, the cost of generation is not known; however, some companies use a value of 18-30 cents per 1,000 cubic feet of air. Compressed air is one of the most expensive sources of energy in a plant. The over-all efficiency of a typical compressed air system can be as low as 10%-15%. For example, to operate a 1-horsepower (hp) air motor at 100 pounds per square inchgauge (psig), approximately 7-8 hp of electrical power is supplied to the air compressor. To calculate the cost of compresse

Compressed Air System Control Strategies

Improving and maintaining compressed air system performance requires not only addressing individual components, but also analyzing both the supply and demand sides of the system and how they interact, especially during periods of peak demand. This practice is often referred to as taking a systems approach because the focus is shifted away from components to total system performance . Matching Supply with Demand With compressed air systems, system dynamics (changes in demand over time) are especially important. Using controls, storage, and demand management to effectively design a system that meets peak requirements but also operates efficiently at part-load is key to a high performance compressed air system. In many systems, compressor controls are not coordinated to meet the demand requirements, which can result in compressors operating in conflict with each other, short-cycling, or blowing off—all signs of inefficient system operation. Individual Compressor Controls Over the y

Compressed Air Storage Strategies

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Compressed air storage can allow a compressed air system to meet its peak demand needs and help control system pressure without starting additional compressors. The appropriate type and quantity of air storage depends on air demand patterns, air quantity and quality required, and the compressor and type of controls being used. An optimal air storage strategy will enable a compressed air system to provide enough air to satisfy temporary air demand events while minimizing compressor use and pressure. The use of air receivers is especially effective for systems with shifting air demand patterns. When air demand patterns are variable, a large air receiver can provide enough stored air so that a system can be served by a small compressor and can allow the capacity control system to operate more effectively. For systems having a compressor operating in modulation to support intermittent demand events, storage may allow such a compressor to be turned off. By preventing pressure decay due

Alternative Strategies for Low-Pressure End Uses

Compressed air is expensive to produce. Because compressed air is also clean, readily available, and simple to use, it is often chosen for applications in which other methods or sources of air are more economical. To reduce compressed air energy costs, alternative methods of supplying low-pressure end uses should be considered before using compressed air in such applications. Many alternative methods of supplying low-pressure end uses can allow a plant to achieve its production requirements effectively. Before deciding to replace a low-pressure end use with an alternative source , it is important to determine the minimum practical pressure level required for the application. Alternative Applications to Low-Pressure End Uses Existing Low-Pressure End Use: Open blowing, mixing Potential Alternatives: Fans, blower, mixers, nozzles Reasoning: Open-blowing applications waste compressed air. For existing open-blowing applications, high efficiency nozzles could be applied, or if

How An Air Compressor Works

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There are many things that you might want to know about how an air compressor works . You will be able to find many interesting pieces of information out about the air compressors, and you should be able to know how they work. This is a very important factor in the overall impression of the air compressors. First of all, the air compressors are going to harness the wind at an amazing rate. This is something that many people have wanted to do because air is something that is very useful. The wind can show us that. There is nothing like being able to sit down on a windy day and know that you are going to be able to get the most out of your air compressors. However, you have to understand how they work, first of all. There are many different types of air compressors. Some are used in building and creating, and some are used in order to convert air to things that we can use, like breathable gas. Most of the time they work in the same way. They work through using a chamber. The cham

Compressed Air Leaking? Is It The Valve Or Is It The Cylinder?

"Reducing air leaks in your plant can save thousands of dollars annually. " Compressed air is one of the most costly forms of energy you can use in your plant, of course, it's one of the most versatile, fast and strong too. When it's "quiet time" in the plant, wander around the machinery and listen. You will often hear the gentle (or perhaps not so gentle) hissing of air escaping from the exhaust port of your air valves. The sound of compressed air "chewing up your dollars" as it wafts to atmosphere can be muted if your air valves have mufflers in the exhaust ports, but nevertheless, it can be heard. Also, there are commercially available ultra-sonic compressed air leak detectors on the market. If your plant doesn't have a "quiet time", which would enable you to actually hear the leaks yourself, investing in an ultrasonic leak detector can bring substantial payback in energy savings. Usually you'll have one air valve conn

Minimize Compressed Air Leaks

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Leaks are a significant source of wasted energy in a compressed air system, often wasting as much as 20%-30% of the compressor’s output. Compressed air leaks can also contribute to problems with system operations, including: Fluctuating system pressure, which can cause air tools and other air-operated equipment to function less efficiently, possibly affecting production Excess compressor capacity, resulting in higher than necessary costs Decreased service life and increased maintenance of supply equipment (includ-ing the compressor package) due to unnecessary cycling and increased run time. Although leaks can occur in any part of the system, the most common problem areas are couplings, hoses, tubes, fittings, pipe joints, quick disconnects, FRLs (filter, regulator, and lubricator), condensate traps, valves, flanges, packings, thread seal-ants, and point-of-use devices. Leakage rates are a function of the supply pressure in an uncontrolled system and increase with higher system pre

11 Tips for Air Compressor Maintenance

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Now that you've invested in an air compressor to run all of your air tools you're going to have to learn how to keep it up and running. Because the standard handyman's air compressors don't typically require daily upkeep, it's easy to forget about them and neglect their upkeep. This can be a costly oversight so it's vital for you to keep an eye on the following maintenance tips. Maintenance Tip 1: Read and Follow Your Air Compressor's Manual Nothing stops an air compressor faster than an owner who doesn't read the owner's manual.  There's going to be some simple tips in there for you that will help you to get a nice long life out of your air compressor - simple stuff for you to do that you would never have thought to do unless you read it. Plus, if you don't follow the rules in your air compressor manual there's a chance that you'll void your warranty. That in itself should be enough of an incentive to read the "flipping&quo