What is a Portable Air Compressor?

A portable air compressor is an air compressor with the ability to be transported easily. There is no true definition of a portable air compressor simply because the term portability means different things to different people. Some may feel that only a compressor that is easily carried is portable. Others may feel that any air compressor that can be easily lifted into a car is portable.

In most cases, a portable air compressor is considered one that can be moved by hand. In those situations, the small air compressor is used often for emergency roadside situations, such as when a tire needs inflated. This is done by connecting the portable air compressor hose to the tire via a valve stem. Once accomplished, inflating the tire is relatively easy.

Q Industries HV35 SuperFlow 12-Volt 140 PSI Air Compressor

In some cases, the unit may be a cordless air compressor. If that is the case, the portable air compressor simply receives its power from batteries. Those may be permanent batteries capable of being recharged with a cord, or may be more standard batteries that can be taken out and recharged or discarded of.

Some portable air compressor units may run off the DC current generated from the car. This is a very convenient way to power the device in the event that there is no other way to do it. Due to the fact the compressors are mainly going to be used in situations where cars are already present, it seems only natural that they run on energy the car produces. The only way a portable air compressor would not work in this situation is if the battery in the car was dead, or the cord connecting the two were damaged.

One thing that should be kept in mind about portable air compressors is that they do not often pack the energy many other types of air compressors do. With a larger air compressor, inflating a tire may be done easily in less than a minute. With a small air compressor, it may be much longer than a minute. Many come with a tire pressure gauge built in, which can help users keep track of when the tire is reaching its desired pressure.

Q Industries MV50 SuperFlow Hi-Volume Air Compressor

Most portable air compressors run between $15 US Dollars (USD) and $100 USD. The difference in the price mainly accounts for the power it is capable of reaching and whether the device is cordless. Some may have other features as well, such as a flashlight and even flashing emergency lights to warn other motorists to keep away.

source : http://www.wisegeek.com/what-is-a-portable-air-compressor.htm

What Is an Air Compressor?

An air compressor increases the amount of air in a particular space. By packing in the air, the air pressure is increased which creates a force that is useful for a variety of purposes, from industrial and manufacturing to commercial and personal purposes.

The original air compressor is the lung. When you take a deep breath to blow out your birthday candles, for example, you're increasing the pressure of the air in your lungs, which effectively is an air compressor containing pressurized air. You then use the force of the air in your lungs to blow out the flames of your birthday candles.

3-Gallon Air Compressor

Eventually, man-made air compressors were created. These fall generally fall into one of two types, positive displacement or dynamic, defined by its mode of operation. A positive displacement air compressor works by filling and then emptying an air chamber. Three common types of positive displacement air compressors are: reciprocating, rotary screw and rotary sliding vane. A dynamic air compressor, on the other hand, uses a a rotating device to accelerate and then decelerate air. This process uses the speed or velocity of the air to increase the air's pressure. Centrifugal air compressors are dynamic air compressors.

Compressed air can be used in a variety of ways. It can be used to alter the chemical composition as in the case of making fertilizer or it can be used for industrial purposes like production line manufacturing processes or it can be used to maintain industrial plants. Perhaps the most well known use of the air compressor is in the case of pneumatic tools like air powered nail guns, staplers, sanders, spray guns, or ratchet wrenches. Air compressors can also be used to move debris. These tools are commonly available at hardware stores for purchase or rental.

Makita MAC700 Big Bore 2.0 HP Air Compressor

Another way to group air compressor types is by the number of stages it has. A two-stage air compressor is usually used for heavy duty use. This type of unit offers a higher level of compression than smaller, single stage air compressors. A two-stage air compressor can store air for future use, and is more energy efficient since it produces more air per unit of horsepower than a single stage compressor. Also, less heat is generated in a two-stage compressor, which means that wear on the unit is reduced. Portable electric air compressors are also available for light-duty applications.

Depending on the type of air compressor, operation costs can be high, as in the case of plant maintenance. While air compressors can run on manual labor, like a hand powered air compressors, most run on either electricity or natural gas. It's the natural gas air compressor that is usually more cost-effective. If the air compressor is used in a small, enclosed area, an electric model may be more desirable in order to avoid gas fumes.

The American Society of Mechanical Engineers (ASME) attests to the quality and protective features of air compressors. Their rating can be considered in evaluating air compressors for purchase or rental. In some states, only ASME-certified air compressors may be sold. Some safety features include a safety relief valve, which lets air escape if the tank's pressure exceeds the maximum. The air compressor should also have a belt guard for protection, and an enclosed air intake filtration system.

As with all tools, proper safety should exercised when using an air compressor. When not being used, air compressors should be properly powered off and unplugged.

source: http://www.wisegeek.com/what-is-an-air-compressor.htm

Top 7 Compressed Air Energy Saving Tips

Would you like to reduce electrical costs related to your compressed air system? More than likely - you can. Start by determining your annual compressed air electrical costs by using this formula:

Brake Horse Power X 0.746 X Annual Hours of Operation X KWH (Kilowatt-Hour) Cost (divided by) Motor Efficiency

NOTE: 1 CFM (Cubit Feet per Minute) @ 100 PSIG (pound-force per square inch gauge) FOR 8760 HOURS COST $110.00 PER YEAR IN ELECTRICAL COST

Next...follow these Top 7 Compressed Air Energy Saving Tips:

1. Fix your Air Leaks

If you do nothing else - follow this one tip: Find and fix your compressed air leaks. Air leaks are industrys' "biggest looser"!

The average plant loses 20% to 30% it its compressed air through multiple small air leaks. The money spent on man power and parts to find and fix these leaks is well worth it. Note (a 1/4 inch hole will flow 103 cfm @ 100 psig)

2. Change to Synthetic Lubricants

If you are using petroleum based lubricants, you could experience up to an 8% energy savings by switching to Compressor Synthetic Lubricants. Plus extend equipment life and save on oil changes and disposal cost.

3. Reduce Plant Operating Pressure

If possible - reduce overall plant pressure. Less pressure > Less CFM used > less energy consumed.

TIP: Reduce plant pressure 2 pounds at a time, then test run for minimum 24 hours. If any equipment has issues...then increase pressure 2 pounds until running smoothly again. For every 2 pound pressure reduction -you save 1% of the electrical cost to run the air compressor.

4. Check Differential Pressure on Air Compressor Filters.

Start at the compressor cabinet filter then check the compressor inlet filter.

Note: A dirty inlet filter can cost you 1% to 3 % in additional electrical costs. Why? Because decreased air flow to the compressor inlet valve increases the compression ratios resulting in more run time.

Next check the air/oil separator differential pressure under a full load. A new separator causes a differential pressure drop of approximately 2-3 psig. When your pressure drop reaches 8-10 psig, then it is time to change your separator elements. A dirty separator element can cost you up to 5% in additional electrical cost.

Next change the control air filter element. This often over looked, but still important filter where the controls receive their air signal. A pressure drop here causes the controls to receive the lower pressure signal loading the compressor more and using more electricity.

5. Reduce the Compressor Inlet Temperature

By reducing inlet air temperature 10°F below 70°F, you save 2% on electrical usage. Your benefit increases up to 8% on a 30°F degree day. But increasing the inlet temperature 10°F above 70°F will cost you 2% in additional electrical usage for every 10°F up to 10% at 120°F. (Inlet temperature has very little affect on Lubricated screw compressors)

6. Check Differential Pressure on Compressed Air Line Filters.

Size Compressed Air Filters to be twice (2x) your compressor CFM flow rate. This will lower your pressure drop approximately 2-3 psig and save 1% on energy costs. Elements will last twice (2x) as long and you will save on maintenance costs.

7. Know what quality of compressed air your plant needs.

The cleaner & dryer the compressed air the more energy used.
Check with the manufacturer of your equipment to determine the quality of air needed.

Article Source: http://EzineArticles.com/3940109

Reciprocating Compressor Efficiency

A compressor's efficiency is determined by the design of the compressor. The efficiency of a compressor starts with the filling of the cylinder. The following sequence of events take place inside a reciprocating compressor during the pumping action.

A medium-temperature application will be used as an example for the pumping sequence. The refrigerant is R-12 the suction pressure is 20 psig, and the dicharege pressure is 180 psig.

1. Piston At The Top of The Stroke and Starting Down.
When the poston has moved down far enough to create less pressure in the cylinder than is in the suction line, the intake flapper valve will open and the cylinder will start to fill with gas.

A flexible coupling. An extensive procedure is used to obtain the correct shaft aligment. This must be done, or bearing and seal will fail prematurely. Courtesy Lovejoy, Inc.

2. Piston Continues to The Bottom of The Stroke.
At this point the cylinder is nearly as full as it is going to get. There is a very slight time lag at the bottom of the stroke as the crankshaft carries the rod around the bottom of stroke.

An illustration of what happens insisde the reciprocating compressor while it is pumping. When the piston starts down, a low pressure is formed under the suction read valve. When this pressure becomes less than the suction pressure and the valve spring tension, the cylinder will begin to fill. Gas will rush into the cylinder through the suction reed valve.

3. Piston is Starting Up.
The rod throw is past bottom dead-center, and the piston starts up. When the cylinder is a full as it is going to get, the suction flapper valve closes.

When the piston gets near the bottom of stroke, the cylinder is nearly as full as it is going to get. There is a short time lag as the crankshaft circles through bottom dead-center, during which a small amount of gas can still flow into the cylinder.

4. The piston Proceeds to The Top of The Stroke. 
When the piston reaches a point that is nearly at the top, the pressure in the cylinder becomes greater than the pressure in the dicharge line. If the discharge pressure is 180 psig, the pressure inside the cylinder may have to reach 190 psig to overcome the discharge valve's weight and spring tension.

When the piston starts back up and gets just off the botttom of the cylinder, the suction valve will have closed, and pressure will begin to build in the cylinder. When the piston gets colose of the top of the cylinder, the pressure will start to approach the pressure in the discharge line. When the pressure inside the cylinder is greater than the perssure on the top side of the discharge reed valve, the valve will open, and the sischarge gas will empty out into the high side of the system.

5. The Piston is At Exactly Top Dead-Center.
This is as close to the top of the head as it can go. There has to be come a certain amount of clearance in the valve assemblies and between the piston and the head, or the would touch. This clearance is known as clearance volume. The piston is going to push as much gas out of the cylinder as time and clearance volume will allow. There will be a small amount of gas left in the clearance volume.

A reciprocating compressor cylinder cannot completely empty because of the clerance volume at the top of the cylinder. Manufactures try to keep this clearance volume to a minimum but cannot completely do away with it.

{source : Refrigeration & air conditioning technology by William C. Whitman,William M. Johnson,John Tomczyk}

The Importance of Energy Storage

Energy Storage not only plays an important role in conserving the energy but also improves the performance and reliability of a wide range of energy systems. Energy storage leads to saving of premium fuels and makes the system more cost effective by reducing the wastage of energy. In most system there is a mismatch between the energy supply and energy demand. The energy storage can even out ehis imblance and thereby help in saving of capital cost.

Energy storage is all the more important where the energy source is intermittent energy sources is likely to grow. If more and more solar energy is to be used for domestic and industrial applications then energy storage is very crucial. If no storage is used in solar energy systems then the major part of the energy demand will be met by the back-up or auxiliary energy and therefore the so called annual solar load fraction will be very low. In case of solar energy, both short term and long term energy storage systems can be used which can adjust the phase difference between solar energy supply and energy demand and can match seasonal demands to the solar availability respectively.

Thermal energy storage can lead to capital cost saving, fuel saving, and fuel subtitution in many application areas. Developing an optimum thermal storage system is as important an area of research as developing an alternative source of energy. The thermal energy can be stored at times when abundantly available and used as and when required.

{source : Solar thermal energy storage by H. P. Garg,S. C. Mullick,A. K. Bhargava}

Designing the Compressed Air System

Most facilities have a number of air compressors that can be operated in combinations to satisfy the demand for compressed air at any time. Large units are needed for periods of high demand, and smaller units are needed to supply reduced amounts of compressed air during weekends or periods of slack production. A centralized air compressor facility together with a common-header and a computer control system for managing the load should provide efficient, cost-effective operation for most plants. In some cases there are large distances between parts of a facility that need compressed air. In those cases it might be more efficient to provide a small compressor at each location to minimize the energy lost in transmitting the compressed air through long pipelines.

Air compressors operate most efficiently when the use cool oar for the intake. One of the factores that should be considered in designing the compressed air system is the access to cool intake air. Air compressor are often located in parts of a facility which are quite warm, and the air intakes use this warm air. In these cases, an outside air intake vent should be installed to allow the compressors to use cooler air.

Types of Air Compressors

There are two major classifications of air compressors: positive displacement compressors and dynamic comprssors. A reciprocating compressor is an example of a positive displacement compressor. In this type of compressor, successive volume of air are trapped in a closed space, and the prssure is increased as the piston moves toward the top of cylinder and reduces the size of the closed space. Reciprocating air compressor have good energy efficiency characteristics at both part-load and full-load. It is more difficult to capture the waste heat from a reciprocating compressor than from a rotary screw of centrifugal air compressor sience the pistons in the reciprociating unit are exposed to the open air around the machine.

The rotary screw compressor is another example of a positive displacement air compressor. In this unit, air enters the inlet and is trapped between mating male and female rotors and compressed to the required dischange pressure. Rotary screw compressors have excellent efficiencies at full-load conditions, and average efficiencies at part-load conditions. Heat recovery is easiest from the rotary screw compressors sience the entrie compressor selection is enclosed.

The centrifugal air compressor is an example of a dynamic compressor, where air is compressed by the dynamic action of rotating impellers or vanes imparting velocity and pressure to the air. Almost all large air compressor (greater than 300 CFM and 50-psig) are centrifugal compressors. The efficiency of these centrifugal air compressors is lower than either the reciprocating or rotary screw models, so smaller air compressors are almost never the centrifugal type. Heat recovery is also somewhat difficult from these compressors.

Compressed Air System Optimization

Compressed air is often referred to as the fourth utility, along with electricity, oil/gas, and water. The cost of commpresed air like all utilities is not free and must be managed. Industry sources have estimated that the total connected horsepower of factory compressed air system in the U.S. exeeds 17 million. This represents a worthy target for the application of energy efficient technologies because many energy conscious engineers exposed to factor environments belive that from 10% to 35% of this could be saved. Using a national energy cost per kilowatt-hour of 8 cents, this translates to billions of dollars in operating cost reductions for the manufacturers. Hence, understanding of the trategies of optimizing the compressed air system is very important for energy engineers.

Components of a compressed air system

Compressed air systems consist of a supply side, which includes compressors and air treatment, and a demand side, wich includes distribution and storage system and enduse equipment. A properly managed supply side will result in clean, dry, stable air being delivered at te appropriate pressure in a dependable, cost-effective manner. A properly managed demand side minimizes wasted air and uses compressed air for appropriate applications. Improving and maintaining peak compressed air system performance requires addressing both the supply and demand sidesof the system and how the two interact.

A typical modern industrial compressed air system is composed of several major subsystems and many sub-components. Major subsystem include the compressor, prime mover, controls, treatment equipment and accessories, and the distribution system. The compressor is the mechanical device that takes in ambient air and invreases its pressure. The prime mover powers the compressor controls serve to regulate the amount of compressed air being produced. The treatment equipment removes contaminants from the compressed air and accessories keep the system operating properly. Distribution system are analogous to wiring in the electrical world-they transport compressed air to where it is needed. Compressed air storage can also serve to improve system performance and efficiency.

{source : Handbook of energy engineering by Albert Thumann,D. Paul Mehta}

Renewable Energy - Wind Energy

The kinetic energy of wind and flowing water are indirect forms of solar energy and are considered renewable. Wind energy technology relies on gradients in physical properties such as atmospheric pressure to generate electrical power. Wind turbines harness wind energy and convert the mechanical energy of a rotating blade into electrical energy in a generator.

Wind Turbine

Moving air rotates blades attached to generator shaft in the machine cabin. The machine cabin is known as the nacelle. It contains the electrical generator wich converts the rotational energy of the rotating blades to electrical energy. Electricity is transmitted through a lini in the post that connects each wind turbine to the electric grid. Therefore, the generator produces electricity that is routed directly to the electric grid.

A typical horizontal axis turbine consists of a rotor with three blades attached to a machine cabin set a top a post that is mounted on a foundation block. The machine cabin contains a generator attached to the wind turbine. The rotor blades can rotate in the vertical plane and the machine cabin can rotate in the horizontal plane.

Most modern horizontal axis turbines have three rotor blades instead of two. Rotor blades attached to a generator shaft, or rotor, make up a rigid body with a particular moment of inertia. Rotational properties of a rigid body, such as angular momentum and torque, depend on moment of inertia. THe moment of inertia of the wind turbine depends on the number of rotor blades and their orientation. Turbines with two rotor blades have a higher moment of inertia when the blades are vertical than when they are horizontal.

The difference in moment of inertia between the horizontal and vertical configuration of two blades introduces a mechanical imbalance that can increase wear on the system. By contrast, the use of three equally spaced blades adds the cost of another blade but allow a symmetric palacement of blades that makes it easier to balance the blaes as they rotate. The improved stability of tubines with three rotor blades increases wind turbine realibility and reduce maintenance cost.

{source : Energy in the 21st century by John R. Fanchi,Christopher J. Fanchi}

Putting Solar Energy to Work

With the exeption of geothermal and nuclear energy, the sun accounts for all forms of energy on earth. Wind, waves, hydroelectric power, biofuels, and biomass all are example of indirect form of solar energy. Even most nonrenewable forms of energy, such as coal peroleum, and natural gas, are really indirect forms of solar energy because they are derived from organic matter made possible by the sun.

Direct forms of solar energy on the other hand, can be used as the energy is reveived. Using daylight to illuminate interior spaces (called daylighting) is a good example.

Passive and Active Solar Thermal Systems

There are two types of solar thermal system for capturing the sun's energy: passive and active. A passive solar system captures the sun's energy as it enters a building without relying on a motor-driven circulator or fan. Once inside the house, the heat can be stored in the mass of the buiding and distibuted by natural means, such as conduction, convection, or radiation, or by forced means, such as with a fan.

In active solar thermal system, collectors capture the sun's energy as heat as it enters the collector and transfer that heat to a fluid. THe heated fluid is moved through the collectors by a motor-driven circulator or fan and taken to whre it can be used immediately or stored for later use.

{source: Convert Your Home to Solar Energy by Joseph R. Provey,Everett M. Barber}

Wind Energy and Air Emission Reduction Benefits

In recent years, increasing attentions has been focused on understanding and qantifiying the impact of wind energy development on various air pollutants. The focus on this issue has intensified as public concern about global climate change has hightened and the contribution to greenhouse gas emissions from fosil fuels to this critical problem has been recognized.

For example, wind energy's air emission reduction benefits have been a source of some confusion in state proceedings to site wind turbines. As utility commissions, evironmental agencies, and other stake holders assess the environmental impacts of wind energy, air emission reduction have become an important part of the evaluation.

This document provides a description of the impact of wind energy development on air emissions. The core document is intended for use by a variety of parties with an interest in this issue, such as state energy and enviromental agencies, county and municipal officials, environmental organizations, and the renewable energy comunity. The appendices provide full references, as well as detailed information for those seeking a more in-depth discussion of selected topics.

One of the obvious benefits of wind energy is that producing electricity from wind produces zero direct emissions of air pollutant. In contast, fossil fuel-fired electric generation from coal, oil, or natural gas results in subtantial direct emissions of numerous air pollutatnts that have adverse feneration from individual fossil fuel-fired power plants or units -thereby reducing fuel consumption and the resulting air emissions that would have otherwise occured.

It should be noted that all from of energy development - from coal and nuclear generation to wind generation- have positive and negative environmental impacts. However, the focus of this document is limited to air emissions, and it is not designed to provide a comprehensive lifecycle analysis of the full range of environmental effects of the various from of electric generation.

{source : Wind Energy and Air Emission Reduction Benefits: A Primer by A. Jacobson,D. Jacobson}

Energy and Demand Saving With Engine-driven Air Compressors

Energy and demand cost saving using an engine-driven air compressor are determined based on average utility rates for four different regions of the country. Net heat recovery cost saving from an engine-driven air compressor is also investigated in this article.

An engine-driven air compressor can be used to realize cost saving with an acceptable playback in the Northeast US and in some instances the Shoutheast an Midwest. Based on average utility prices in the West, an engine-driven air compressor will not present an acceptable payback period.

Producing compressed air can be a significant precentage of the electrical energy cost for industrial facilities as compressed air plays a key role in many production processes. Since most industrial facilities are driven by the economics of production, there is a constant search for methods to reduce porating and production cost.

The installation of a natural gas engine-driven air compressor can significantly reduce the energy cost associated with production by decreasing electrical peak demand and by utilizing a cheaper energy source. Facilities that are slaved to the use of compressed air for operating production equipment and are located in regions with elevated demand const or high electrical energy rates are exellent candidates for engine-driven air compressors.

Maintenance Cost of an Electric Air Compressor

Maintenance of an electric air compressor usually includes the changing of air filters and compressor oil. Air filters are usually changed monthly, while oil changes depend upon the type of oilt htat is used and the operating hours. Labor costassociated with the filter and oil changes are considered to be negligible in comparison to the oprating costs. Maintenance of electric air compressors is generally considered as part of the regular maintanance of a facility and does not present an addintional financial burden.

{source : User's guide to natural gas technologies by F. William Payne}