Difference Between kVA and kW

kVA vs kW

Have you ever noticed that with every appliance or piece of electrical machinery that you avail, they will always indicate their respective power ratings?

You will notice that some electrical equipment express their power ratings in kW, or kilowatts; and some are expressed in kVA, or kilo Volt Amperes. Both values express power, but they are actually different.

kVA is known as the ‘apparent power’ of a particular circuit or electrical system. In direct current circuits, kVA is equal to kW, because voltage and current do not get out of phase. However, ‘apparent power’ and ‘real power’ (which is expressed as kW) may differ in alternating current circuits. kW is simply the amount of actual power that does valid work. It should be noted that only fraction of kVA is accessible to do work, and the rest is an excess in the current.

Solving for the kW (real power) requires another variable called the Power Factor (PF). That so-called Power Factor is a nebulous value that can vary for every appliance or electrical device. In essence, the value of the Power Factor is either given in a percentage, or 0 to 1, wherein 100 percent (or 1) is considered as unity. The closer the Power Factor is to unity, the more efficient a particular device is with its use of electricity.

Unity is practically present in DC circuits, which creates no difference between the kVA and kW. A device uses less kW when the voltage is out of phase with the current. At the same time, the Power Factor naturally lowers in the process. Power Factor will either be leading or lagging, depending on which way the load shifts the phase of the current with respect to the phase of the voltage.

The relationship between the three (kVA, kW, and Power Factor) is mathematically described as:

kW = kVA x Power Factor; kVA = kW / Power Factor; Power Factor = kW / kVA

In DC circuits, the power factor is mathematically inconsequential, because it is in unity. Therefore:

kW = kVA = Volts x Current x 1 = Volts x Current

Summary:

1. kVA is known as the ‘apparent power’, while kW refers to the actual, or real power.

2. kW is the amount of power capable of doing work, while only a portion of kVA is available to do work.

3. kW is kilowatts, while kVA is kilo Volts Amperes.

4. kVA is equal to kW in DC circuits because the voltage and current are not out of phase (unity).

5. However, in AC circuits, voltage and current may get out of phase. Therefore, kW and kVA will differ depending on the Power Factor, or how much leading or lagging occurs.

Read more: Difference Between kVA and kW | Difference Between | kVA vs kW http://www.differencebetween.net/science/difference-between-kva-and-kw/#ixzz3dxOF3nTj

 How a Turbocharger Works

Critical to the Operation of Diesel EnginesAn engine is designed to burn a fuel-air mixture to produce mechanical energy. The mechanical energy then moves pistons up and down to create the rotary motion that turns the wheels of a vehicle. The more mechanical energy, the more power the engine can produce.
A significant difference between a turbocharged diesel engine and a traditional naturally aspirated gasoline engine is that the air entering a diesel engine is compressed before the fuel is injected. This is where the turbocharger is critical to the power output and efficiency of the diesel engine. It is the job of the turbocharger to compress more air flowing into the engine’s cylinder. When air is compressed the oxygen molecules are packed closer together. This increase in air means that more fuel can be added for the same size naturally aspirated engine. This generates increased mechanical power and overall efficiency improvement of the combustion process. Therefore, the engine size can be reduced for a turbocharged engine leading to better packaging, weight saving benefits and overall improved fuel economy.
Although turbocharging is a relatively simple concept, the turbocharger is critical to the operation of the diesel engine and therefore requires a highly engineered component. Our extensive experience in turbocharging technology and knowledge of engines combines for world-class design and manufacture of Holset Turbochargers, renowned for their durability, high standard of safety, and reliable performance that engines demand.
How does a turbocharger work?
A turbocharger is made up of two main sections: the turbine and the compressor. The turbine consists of the (1) turbine wheel and the (2) turbine housing. It is the job of the turbine housing to guide the (3) exhaust gas into the turbine wheel. The energy from the exhaust gas turns the turbine wheel, and the gas then exits the turbine housing through an (4) exhaust outlet area.
(1)  The turbine wheel (2)  The turbine housing
(3)  Exhaust gas
(4)  Exhaust outlet area(5)  The compressor wheel (6)  The compressor housing(7)  Forged steel shaft (8)  Compressed air


















The compressor also consists of two parts: the (5) compressor wheel and the (6) compressor housing. The compressor’s mode of action is opposite that of the turbine. The compressor wheel is attached to the turbine by a (7) forged steel shaft, and as the turbine turns the compressor wheel, the high-velocity spinning draws in air and compresses it. The compressor housing then converts the high-velocity, low-pressure air stream into a high-pressure, low-velocity air stream through a process called diffusion. The (8) compressed air is pushed into the engine, allowing the engine to burn more fuel to produce more power.

Understanding variable frequency drives

VFD use is increasing because users say VFDs improve manufacturing processes and reduce cost. Understanding how they do their job can help as you consider deployments.

If you’re involved with trying to save energy in your plant, at some point you have probably looked into variable frequency drives (VFDs) for ac motors. Reports from all directions say they can help save energy, reduce maintenance, and cut utility costs. The questions are: are they as good as they sound, and how do they work?

A VFD controls the speed of an ac motor, which provides flexibility to the process since speed can be changed easily for process optimization. It takes the fixed power supplied to it and converts it into a variable frequency and variable voltage source which then feeds a motor. This allows the drive to control the speed and torque the motor produces.  
A VFD may enhance the user’s profitability by improving the process, which in turn produces a fast return on investment (ROI). Process improvements may come from better:

• Speed control;
• Flow control;
• Pressure control;
• Temperature control;
• Tension control;
• Torque control;
• Monitoring quality; and
• Acceleration/deceleration control.

Many applications that use ac motors would benefit from the use of such drives because they can also reduce operating costs while improving the process. Reduced costs come from:

• Increased system reliability;
• Reduced downtime;
• Reduced equipment setup time;
• Energy savings;
• Lower maintenance;
• Smoother operation—less wear and tear; and
• Power factor control.

The net result of these improvements is increased profitability.
Evaluating applications
Different drive applications have different criteria that should be evaluated individually. For example, when used in a centrifugal pump or fan application, an ac drive saves energy by allowing the user to adjust the speed of the motor to the most efficient level. This can often be as much as a 60% energy saving over fixed-speed motors with valve controls. This is usually enough to pay for the drive within a short period of time.
When discussing VFDs and energy savings, the attention often focuses on this type of centrifugal fan or pump application. However, there are other applications that also have large potential energy savings and/or recovery based on easily applicable concepts that should not be overlooked. These applications are power factor correction, regeneration, common bus applications, or a combination of all three. Let’s examine all these and see how using the right drive generates its benefit.
Centrifugal applications: laws of affinity
The cost savings in a centrifugal fan or pump application are primarily derived from two components:

• The laws of affinity, which shows an operating range that produces the most flow or pressure per horsepower. (See Figure 1.)
• Removal of any mechanical flow device that limits the flow of a fan or pump while the motor turns the application at a fixed speed. (See Figures 2 and 3.)

The ac drive installation continues to save energy for many years after the initial payback period, as well as lowers the maintenance costs and provides a more consistent flow of product. When a centrifugal fan or pump is used with mechanical flow control, converting the application to an adjustable-speed ac drive will save from 10% to 60% of energy cost if the fan or pump system is designed to operate between 40% to 80% percent of full speed. This application typically produces a return on investment in the 6- to 24-month time frame.
The laws of affinity state:

• Flow is proportional to shaft speed;
• Head (pressure) is proportional to the square of shaft speed; and
• Power is proportional to the cube of shaft speed.

When comparing the different methods of mechanical flow control, the graphs clearly show that the only one that gets close to the maximum efficiency of the theoretical fan curve or pump flow is a VFD.

Power factor
What is power factor (PF)? AC power has two basic components: voltage and current. When these two components are not in sync, power is wasted due to inefficiency. This is called power factor displacement. To make matters worse, when the ac power has a high level of harmonic content called power factor distortion, the displacement and distortion are multiplied by each other, which further decreases efficiency.

If you have ever received a bill from your electric utility company penalizing your plant there is a good chance that a power factor displacement issue exists. Even if the power company does not charge an extra penalty, you are still paying for the excess energy that is used. Therefore, getting the power factor displacement close to unity is very important.
Here is a graphic example of total power factor, power factor displacement and power factor distortion (harmonics):




Power factor penalties
While each utility may charge differently, two common ways that utilities charge are by KVA (Lower PF = higher Amps) or by kW with a PF penalty.
If the power factor is less than 90%, the measured kW demand will be multiplied by the ratio of 90% divided by the actual power factor:
                  100 kW motor with 0.85 power factor: (100 kW*0.9) / (0.85 PF) = 105 kW
In this case the increase in cost is 5% of your bill in addition to the wasted kvar as in the previous example.
The second method is an adjustment of demand for power, where demands will be adjusted to correct for average power factors lower than 95%. Such adjustments will be made by increasing the measured demand 1% for each 1% or major fraction thereof by which the average power factor is less than 95% lagging.
In this case the penalty increase is 1% for every 1% that the power factor is below 0.95 in addition to the wasted kvar.
While there are power factor correction devices available, such as capacitors and filters, an ac drive is often overlooked as a method for correcting power factor displacement while at the same time having a low distortion level. A VFD with an active front end (AFE) has the ability to adjust its power factor operating point as well as limit harmonics to less than 4%. As a comparison, when using a standard six-pulse ac drive with a diode rectifier that converts input ac voltage to dc bus voltage, the typical harmonics level is 30% to 40%. There is at least one AFE ac drive available today that has the ability to adjust its power factor from 0.8 leading to 0.8 lagging and that meets IEEE 519 harmonic standards for low power factor distortion. This means the drive can improve the present power factor displacement in a facility.
Distortion power factor describes the decrease in average power transferred due to harmonics and to phase shift between current and voltage.
How much this costs and how much can be saved depends on the amount of displacement and distortion that currently exists. 
Regeneration
An ac motor may act either as a motor that turns electrical power into mechanical power or as a generator that converts mechanical power into electricity. It depends on whether the motor is turning a machine that requires power to turn the machine or whether the load of the machine will at times overhaul the motor. (Overhauling is a condition where the mechanics or physics of the load mechanically cause the motor to attempt to turn faster than the motor speed the drive is commanding and the drive is used to slow down the motor speed.) This overhauling condition may exist in several types of applications.
1. Constant deceleration: When a load such as a decline conveyor operating under the influence of gravity will overhaul the motor’s speed and the drive is used to control the conveyor speed to a slower level than what the natural physics of the application would produce.
 2. Periodic deceleration: When a load is stopped quickly and the inertia of the load wants to keep turning, such as a large drum. In this case the cycle time, or how many times the load is stopped over time, as well as the magnitude of the stopping power required, determines how much energy can be saved.
3. System tension/holding torque: When two sections of a machine are used to create tension on the material between them, such as on the metal strip in a strip mill. The two sections may be running at the same speed, but the process requires a certain amount of tension on the strip to run properly. This means the lead section will run in the forward direction and pull the strip, and the following section will also run in the forward direction and at the same time provide the needed torque in the reverse direction of the strip, thus creating the proper tension.
In each of these examples the motor and drive combination has the ability to recover the electrical power produced by the motor when it is acting as a generator, and sends that power to the utility company. How much energy is saved is dependent on the application, but it can be significant. One such application where significant savings can be recovered is a gearbox test stand. When the gearbox is tested, one drive and motor are used to turn the gearbox while another drive and motor are used on the other end of the gearbox to simulate the load. Done correctly, this application will operate with a very low amount of total energy, as the amount of energy used to turn the gearbox is the same amount of energy that is recovered from the simulated load on the gearbox, less the losses in the system. The one question you should ask when trying to determine if the application is regenerative is, “Does the load, at any time, try to turn the motor (regenerative recovery), or is the motor being used to turn the load?”
Common bus
When there are multiple ac drives in one location, a common bus system is usually the most efficient way to operate. It can incorporate the energy savings and recovery concepts that have just been discussed. If there is a regenerative ac drive and motor section in the system, it is ideally suited for maximizing energy recovery and cost savings. The reason for this is that losses are generated when power is converted from the ac supply to the dc bus or from the dc bus to the ac supply. When you have multiple stand-alone drives, the power must go through two or more ac-to-dc conversions, and two dc-to-ac conversions. (See Figures 8 and 9.) In a common bus configuration, power goes through only one ac-to-dc conversion in the motoring direction, and when an inverter section of the drive regenerates power to the dc bus, the power goes straight to another inverter via the common dc bus link, which is motoring and does not have to travel through a converter at all. This method eliminates two conversion points where energy would be lost. This increases efficiency by 2% to 4% for each regenerative section. If you have more sections that are regenerative, you will accumulate more energy savings. In addition to the savings of a common bus solution, if you have an AFE, the system will have the ability to do power factor correction, which increases the savings of a common bus system. The gearbox test stand is a great example of a common bus solution. Here there is one forward motoring drive motor section and one regenerative drive motor section. In this specific case the two drive and motor sections were rated at 1,000 A at 690 Vac each. Yet the incoming ac line and input modules were able to be sized at less than 1,000 A at 690 Vac. This was possible because one of the two sections required 1,000 A in the motoring or torque producing direction, while the other section that provided the load was able to recover through regeneration close to 1,000 A, less the losses in the system. Therefore, the amps generated from the recovery section almost canceled out the 1,000 A from the section providing torque to turn the gearbox, and the input ac could be sized at slightly larger than the losses of the system, which in this case was roughly 200 A at 690 Vac. This resulted in a lower installation cost due to the smaller ac-to-dc section. The application recovered $75,000 per year in energy costs, which translated to a four-year payback.

This application combined the efficiency of a regenerative system in a common bus configuration. If the plant would have had a power factor correction issue, the common bus solution would have been able to accumulate those savings into this total as well.

In conclusion, when using an ac drive and motor combination, there are many different applications and methods for which the energy savings and energy recovery can be significant. While there is typically much focus on the drive’s initial cost, each application should be reviewed to determine the maximum amount of increased productivity and decreased operating cost due to energy savings and energy recovery. In many cases energy savings and operating cost are much higher than the cost of installing the drive.

Pressure Transducers Allow Variable Frequency Drive Control in Machinery and Factory Automation

What is VFD?

VFD, or variable frequency drive, is a common tool in electric motor control. VFDs, simply put, control electric motors by modifying the power input frequency to the electric motor. VFDs used in conjunction with electrically driven pumps can be made to control both the flow rate and the output pressure of the pump with continuous pressure.
Common uses for VFD-controlled electric motor pumps include the following:

• Water lift systems: Transfers water supply from lower to higher elevation levels since conventional gravity-fed systems with water tower cannot apply necessary pressure.
• Clean water systems: Transfers water supply to, through, and from water treatment facilities.
• Sewage pumping systems: Transfers sewage to processing plants where fluids can be filtered, cleaned, and released to the environment.
• Reservoir management systems: Includes water towers, where sudden draws of water decrease the outlet water pressure of the tower, requiring immediate refilling.
• Compressed air systems: Includes shop air supply, where constant, reliable air pressure is required.

VFD pumping systems excel where continuous monitoring of pressure to minimize overshoot and undershoot of desired pressures is necessary.

Pressure Transducers Provide Variable Frequency Drive Control in Electric Motor Applications

Pressure transducers are used for VFD control in machinery and factory automation in the following electric motor applications:

• Pump intake pressure monitoring
• Pump output pressure monitoring and control
• End location (reservoir, water system, etc.) pressure monitoring and control

What is a Variable Frequency Drive?

What is a VFD?

A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor. Other names for a VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly related to the motor’s speed (RPMs). In other words, the faster the frequency, the faster the RPMs go. If an application does not require an electric motor to run at full speed, the VFD can be used to ramp down the frequency and voltage to meet the requirements of the electric motor’s load. As the application’s motor speed requirements change, the VFD can simply turn up or down the motor speed to meet the speed requirement.

How does a Variable Frequency Drive work?

The first stage of a Variable Frequency AC Drive, or VFD, is the Converter. The converter is comprised of six diodes, which are similar to check valves used in plumbing systems. They allow current to flow in only one direction; the direction shown by the arrow in the diode symbol. For example, whenever A-phase voltage (voltage is similar to pressure in plumbing systems) is more positive than B or C phase voltages, then that diode will open and allow current to flow. When B-phase becomes more positive than A-phase, then the B-phase diode will open and the A-phase diode will close. The same is true for the 3 diodes on the negative side of the bus. Thus, we get six current “pulses” as each diode opens and closes. This is called a “six-pulse VFD”, which is the standard configuration for current Variable Frequency Drives.

Let us assume that the drive is operating on a 480V power system. The 480V rating is “rms” or root-mean-squared. The peaks on a 480V system are 679V. As you can see, the VFD dc bus has a dc voltage with an AC ripple. The voltage runs between approximately 580V and 680V.

We can get rid of the AC ripple on the DC bus by adding a capacitor. A capacitor operates in a similar fashion to a reservoir or accumulator in a plumbing system. This capacitor absorbs the ac ripple and delivers a smooth dc voltage. The AC ripple on the DC bus is typically less than 3 Volts. Thus, the voltage on the DC bus becomes “approximately” 650VDC. The actual voltage will depend on the voltage level of the AC line feeding the drive, the level of voltage unbalance on the power system, the motor load, the impedance of the power system, and any reactors or harmonic filters on the drive.
The diode bridge converter that converts AC-to-DC, is sometimes just referred to as a converter. The converter that converts the dc back to ac is also a converter, but to distinguish it from the diode converter, it is usually referred to as an “inverter”. It has become common in the industry to refer to any DC-to-AC converter as an inverter.

Note that in a real VFD, the switches shown would actually be transistors.
When we close one of the top switches in the inverter, that phase of the motor is connected to the positive dc bus and the voltage on that phase becomes positive. When we close one of the bottom switches in the converter, that phase is connected to the negative dc bus and becomes negative. Thus, we can make any phase on the motor become positive or negative at will and can thus generate any frequency that we want. So, we can make any phase be positive, negative, or zero.

The blue sine-wave is shown for comparison purposes only. The drive does not generate this sine wave.
Notice that the output from the VFD is a “rectangular” wave form. VFD’s do not produce a sinusoidal output. This rectangular waveform would not be a good choice for a general purpose distribution system, but is perfectly adequate for a motor.
If we want to reduce the motor frequency to 30 Hz, then we simply switch the inverter output transistors more slowly. But, if we reduce the frequency to 30Hz, then we must also reduce the voltage to 240V in order to maintain the V/Hz ratio (see the VFD Motor Theory presentation for more on this). How are we going to reduce the voltage if the only voltage we have is 650VDC?
This is called Pulse Width Modulation or PWM. Imagine that we could control the pressure in a water line by turning the valve on and off at a high rate of speed. While this would not be practical for plumbing systems, it works very well for VFD’s. Notice that during the first half cycle, the voltage is ON half the time and OFF half the time. Thus, the average voltage is half of 480V or 240V. By pulsing the output, we can achieve any average voltage on the output of the VFD.

See the Pictures below to understand what the different parts of a drive look like.

Why should I use a VFD?

Reduce Energy Consumption and Energy Costs

If you have an application that does not need to be run at full speed, then you can cut down energy costs by controlling the motor with a variable frequency drive, which is one of the benefits of Variable Frequency Drives. VFDs allow you to match the speed of the motor-driven equipment to the load requirement. There is no other method of AC electric motor control that allows you to accomplish this.
Electric motor systems are responsible for more than 65% of the power consumption in industry today. Optimizing motor control systems by installing or upgrading to VFDs can reduce energy consumption in your facility by as much as 70%. Additionally, the utilization of VFDs improves product quality, and reduces production costs. Combining energy efficiency tax incentives, and utility rebates, returns on investment for VFD installations can be as little as 6 months.

Increase Production Through Tighter Process Control

By operating your motors at the most efficient speed for your application, fewer mistakes will occur, and thus, production levels will increase, which earns your company higher revenues. On conveyors and belts you eliminate jerks on start-up allowing high through put.

Extend Equipment Life and Reduce Maintenance

Your equipment will last longer and will have less downtime due to maintenance when it’s controlled by VFDs ensuring optimal motor application speed. Because of the VFDs optimal control of the motor’s frequency and voltage, the VFD will offer better protection for your motor from issues such as electro thermal overloads, phase protection, under voltage, overvoltage, etc.. When you start a load with a VFD you will not subject the motor or driven load to the “instant shock” of across the line starting, but can start smoothly, thereby eliminating belt, gear and bearing wear. It also is an excellent way to reduce and/or eliminate water hammer since we can have smooth acceleration and deceleration cycles.

What is a Variable Freqency Drive (VFD / Inverter)?

AMOLED vs LCD: Which screen is best for your phone?

Buying a phone is becoming harder and harder these days. There are so many different options on smartphones that it is hard to keep up with all the latest technology. With phones and tablets almost completely relying on touchscreen interfaces, the screens on these devices are easily the most important part of modern day devices. There are several different technologies behind these screens, and we aim to explain what some of these terms mean. If you’ve ever wondered what AMOLED, LCD, IPS, or TFT mean, you’re reading the right article.

These days you really only have two choices of screens when you are buying a smartphone or tablet: LCD or AMOLED. Many of you probably can’t tell the difference between the two screen types, but both technologies have inherent strengths and weaknesses. LCD has been around for a while, but AMOLED phones are gaining popularity thanks to Samsung and other manufacturers. There isn’t a clear winner at this point in time, so here’s a look at both.
Update: This article was originally published on June 18, 2012, and updated on Aug. 25, 2014, to reflect recent devices. DT writer Aaron Liu contributed to this article.

LCD

LCD, Liquid Crystal Display, has been a part of our lives for years now. Besides mobile devices, we see LCD screens being used with almost every computer monitor, and in the majority of TVs. While these screens are made of wondrous liquid crystals, they also require a couple panes of glass, and a light source. LCD screens produce some of the most realistic colors you can find on a screen, but might not offer as wide of a contrast ratio (darker darks and brighter brights) as an AMOLED screen.
Some common terms you will find associated with LCD displays are TFT and IPS. TFT stands for Thin Film Transistor, which makes the wiring of LCD screens more efficient by reducing the number of electrodes per pixel. One benefit of TFT displays is an improved image quality over standard LCD screens. Another popular LCD technology is In-Plane Switching, or IPS, which improves upon TFT by offering much wider viewing angles and color reproduction on LCD screens. IPS screens are able to achieve this by keeping all the liquid crystals parallel to the screen. IPS is generally preferable to standard TFT.

Notable Devices with LCD Screens: iPhone 5 and 5s, LG G3, Sony Xperia 2, Google Nexus 5.

AMOLED

AMOLED, Active Matrix Organic Light Emitting Diode, technology has grown in popularity in recent years, particularly among Samsung products. AMOLED screens consist of a thin layer of organic polymers that light up when zapped with an electric current. Due to this simple construction, AMOLED screens can be extremely thin and do not require a backlight. The benefit of losing a backlight is readily apparent: these screens are able to produce blacks so deep that the screen pixels can shut right off. Shutting off pixels can also save electricity and battery life in phones and tablets. Just keep your backgrounds close to black and you’ll save energy.

Sometimes when you read about AMOLED screens, you might hear people complaining about something called a “pentile” display. This is a feature of most color AMOLED screens. Instead of having just a single red, blue, and green sub pixel per actual pixel, pentile displays have a RGBG sub pixel layout which has two green sub pixels for each red and blue. The positive of this technology is that you are able to create a screen that is just as bright as normal screens with one third the amount of sub pixels. The negative of pentile screens is that they can appear grainy, or appear to be lower resolution due to the larger, more visible sub pixels. For a while, Samsung begun using a display type called Super AMOLED Plus, which does not use a pentile sub pixel layout and also improves viewability in direct sunlight — traditionally a weakness for AMOLED. Samsung equipped the Galaxy S II with a Super AMOLED plus screen, but then reverted back to Super AMOLED screens for the Galaxy S III, citing screen life as the reason for the switch.
Notable Devices with AMOLED screens: Samsung Galaxy S series, Nokia Lumia 900, HTC One S.

You be the judge

Can you tell which is AMOLED or LCD?

There are pros and cons for each type of screen, and both screen technologies can produce vivid, beautiful displays. The only way to know for sure if the screen on your future device will satisfy you is to try it out for yourself. You will be able to easily see if the screen viewing angles, contrast ratio, and color reproduction will fit your needs after using the phone for just a few minutes.
Related: LCD vs. Plasma TVs, LED vs. LCD TVs, and 1080p vs. 1080i.

Read more: http://www.digitaltrends.com/mobile/amoled-vs-lcd-which-screen-is-best-for-your-phone/#ixzz3awZnQAw6
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Fuel Cell Basics

Through this website we are seeking historical materials relating to fuel cells. We have constructed the site to gather information from people already familiar with the technology–people such as inventors, researchers, manufacturers, electricians, and marketers. This Basics section presents a general overview of fuel cells for casual visitors.

What is a fuel cell?	How do fuel cells work?
Why can't I go out and buy a fuel cell?
Different types of fuel cells.

What is a fuel cell?

A fuel cell is a device that generates electricity by a chemical reaction. Every fuel cell has two electrodes, one positive and one negative, called, respectively, the anode and cathode. The reactions that produce electricity take place at the electrodes.
Every fuel cell also has an electrolyte, which carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes.
Hydrogen is the basic fuel, but fuel cells also require oxygen. One great appeal of fuel cells is that they generate electricity with very little pollution–much of the hydrogen and oxygen used in generating electricity ultimately combine to form a harmless byproduct, namely water.
One detail of terminology: a single fuel cell generates a tiny amount of direct current (DC) electricity. In practice, many fuel cells are usually assembled into a stack. Cell or stack, the principles are the same.
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How do fuel cells work?

The purpose of a fuel cell is to produce an electrical current that can be directed outside the cell to do work, such as powering an electric motor or illuminating a light bulb or a city. Because of the way electricity behaves, this current returns to the fuel cell, completing an electrical circuit. (To learn more about electricity and electric power, visit "Throw The Switch" on the Smithsonian website Powering a Generation of Change.) The chemical reactions that produce this current are the key to how a fuel cell works.
There are several kinds of fuel cells, and each operates a bit differently. But in general terms, hydrogen atoms enter a fuel cell at the anode where a chemical reaction strips them of their electrons. The hydrogen atoms are now "ionized," and carry a positive electrical charge. The negatively charged electrons provide the current through wires to do work. If alternating current (AC) is needed, the DC output of the fuel cell must be routed through a conversion device called an inverter.

Graphic by Marc Marshall, Schatz Energy Research Center

Oxygen enters the fuel cell at the cathode and, in some cell types (like the one illustrated above), it there combines with electrons returning from the electrical circuit and hydrogen ions that have traveled through the electrolyte from the anode. In other cell types the oxygen picks up electrons and then travels through the electrolyte to the anode, where it combines with hydrogen ions.
The electrolyte plays a key role. It must permit only the appropriate ions to pass between the anode and cathode. If free electrons or other substances could travel through the electrolyte, they would disrupt the chemical reaction.
Whether they combine at anode or cathode, together hydrogen and oxygen form water, which drains from the cell. As long as a fuel cell is supplied with hydrogen and oxygen, it will generate electricity.
Even better, since fuel cells create electricity chemically, rather than by combustion, they are not subject to the thermodynamic laws that limit a conventional power plant (see "Carnot Limit" in the glossary). Therefore, fuel cells are more efficient in extracting energy from a fuel. Waste heat from some cells can also be harnessed, boosting system efficiency still further.
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So why can't I go out and buy a fuel cell?

The basic workings of a fuel cell may not be difficult to illustrate. But building inexpensive, efficient, reliable fuel cells is a far more complicated business.
Scientists and inventors have designed many different types and sizes of fuel cells in the search for greater efficiency, and the technical details of each kind vary. Many of the choices facing fuel cell developers are constrained by the choice of electrolyte. The design of electrodes, for example, and the materials used to make them depend on the electrolyte. Today, the main electrolyte types are alkali, molten carbonate, phosphoric acid, proton exchange membrane (PEM) and solid oxide. The first three are liquid electrolytes; the last two are solids.
The type of fuel also depends on the electrolyte. Some cells need pure hydrogen, and therefore demand extra equipment such as a "reformer" to purify the fuel. Other cells can tolerate some impurities, but might need higher temperatures to run efficiently. Liquid electrolytes circulate in some cells, which requires pumps. The type of electrolyte also dictates a cell's operating temperature–"molten" carbonate cells run hot, just as the name implies.
Each type of fuel cell has advantages and drawbacks compared to the others, and none is yet cheap and efficient enough to widely replace traditional ways of generating power, such coal-fired, hydroelectric, or even nuclear power plants.
The following list describes the five main types of fuel cells. More detailed information can be found in those specific areas of this site.
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Different types of fuel cells.

Drawing of an alkali cell.

Alkali fuel cells operate on compressed hydrogen and oxygen. They generally use a solution of potassium hydroxide (chemically, KOH) in water as their electrolyte. Efficiency is about 70 percent, and operating temperature is 150 to 200 degrees C, (about 300 to 400 degrees F). Cell output ranges from 300 watts (W) to 5 kilowatts (kW). Alkali cells were used in Apollo spacecraft to provide both electricity and drinking water. They require pure hydrogen fuel, however, and their platinum electrode catalysts are expensive. And like any container filled with liquid, they can leak.

Drawing of a molten carbonate cell

Molten Carbonate fuel cells (MCFC) use high-temperature compounds of salt (like sodium or magnesium) carbonates (chemically, CO₃) as the electrolyte. Efficiency ranges from 60 to 80 percent, and operating temperature is about 650 degrees C (1,200 degrees F). Units with output up to 2 megawatts (MW) have been constructed, and designs exist for units up to 100 MW. The high temperature limits damage from carbon monoxide "poisoning" of the cell and waste heat can be recycled to make additional electricity. Their nickel electrode-catalysts are inexpensive compared to the platinum used in other cells. But the high temperature also limits the materials and safe uses of MCFCs–they would probably be too hot for home use. Also, carbonate ions from the electrolyte are used up in the reactions, making it necessary to inject carbon dioxide to compensate. Phosphoric Acid fuel cells (PAFC) use phosphoric acid as the electrolyte. Efficiency ranges from 40 to 80 percent, and operating temperature is between 150 to 200 degrees C (about 300 to 400 degrees F). Existing phosphoric acid cells have outputs up to 200 kW, and 11 MW units have been tested. PAFCs tolerate a carbon monoxide concentration of about 1.5 percent, which broadens the choice of fuels they can use. If gasoline is used, the sulfur must be removed. Platinum electrode-catalysts are needed, and internal parts must be able to withstand the corrosive acid.

Drawing of how both phosphoric acid and PEM fuel cells operate.

Proton Exchange Membrane (PEM) fuel cells work with a polymer electrolyte in the form of a thin, permeable sheet. Efficiency is about 40 to 50 percent, and operating temperature is about 80 degrees C (about 175 degrees F). Cell outputs generally range from 50 to 250 kW. The solid, flexible electrolyte will not leak or crack, and these cells operate at a low enough temperature to make them suitable for homes and cars. But their fuels must be purified, and a platinum catalyst is used on both sides of the membrane, raising costs.

Drawing of a solid oxide cell

Solid Oxide fuel cells (SOFC) use a hard, ceramic compound of metal (like calcium or zirconium) oxides (chemically, O₂) as electrolyte. Efficiency is about 60 percent, and operating temperatures are about 1,000 degrees C (about 1,800 degrees F). Cells output is up to 100 kW. At such high temperatures a reformer is not required to extract hydrogen from the fuel, and waste heat can be recycled to make additional electricity. However, the high temperature limits applications of SOFC units and they tend to be rather large. While solid electrolytes cannot leak, they can crack. More detailed information about each fuel cell type, including histories and current applications, can be found on their specific parts of this site. We have also provided a glossary of technical terms–a link is provided at the top of each technology page.

First Eight CA Dealers Announced For 2016 Toyota Mirai Hydrogen Fuel-Cell Car

2016 Toyota Mirai: 'A car that breathes in air,' posted by Toyota, Feb 2015

With the 2016 Toyota Mirai set to go on sale this October, Toyota has now announced the first eight dealers that will be selling its first production hydrogen fuel-cell vehicle.
Four are in Northern California, four in the southern part of the state.
Production of the Mirai will be limited to about 3,000 vehicles for the U.S. through 2017.

ALSO SEE: 2016 Toyota Mirai: First Drive Of Hydrogen Fuel-Cell Sedan

The Northern California dealerships selling the Mirai are San Francisco Toyota, Roseville Toyota, Stevens Creek Toyota, and Toyota of Sunnyvale.
In the Los Angeles Basin and environs, the dealers are Longo Toyota, Toyota Santa Monica, Toyota of Orange and Tustin Toyota.

2016 Toyota Mirai construction at Motomachi plant

Toyota says it chose the initial dealerships based on both their proximity to hydrogen refueling infrastructure and their previous sales of advanced-technology vehicles, presumably hybrids and plug-in electric vehicles.
Starting this summer, potential Mirai buyers will have to apply to purchase or lease the car online.

DON'T MISS: 10 Questions On Hydrogen Fuel-Cell Cars To Ask Toyota, Honda & Hyundai

Only "select, eligible customers" will be allocated Mirais, largely based on how close they live and work to hydrogen fueling stations.
Accordingly, as Toyota says in its release, "Drivers are encouraged to make their requests early to save a potential parking spot in transportation history."

2016 Toyota Mirai hydrogen fuel-cell car, Newport Beach, CA, Nov 2014

While the reservation and ordering process will be online, sales and delivery of every Mirai must take place through the authorized Mirai dealer of the customer’s choice.
Toyota appears to be marketing the Mirai as the most advanced and technically sophisticated vehicle it sells.

MORE: Lesson Learned In Last Round Of Hydrogen Fueling: Fund Operations Too

Its release calls those potential customers "California trailblazers," echoing an ad last year in which it suggested that drivers who chose not to drive fuel-cell cars would be "roadblocks" to a future world of zero-emission vehicles.
Toyota is one of three carmakers who will sell hydrogen-fueled vehicles in California over the next two years.

2016 Toyota Mirai hydrogen fuel-cell car, Newport Beach, CA, Nov 2014

The Hyundai Tucson Fuel Cell, a compact crossover utility vehicle converted by its Korean maker to hydrogen power, began leasing last summer.
As of December, Hyundai had delivered 54 hydrogen Tucsons.

RELATED: How To Test Hydrogen Vs Electric Cars: A Challenge To Automakers (In Our Dreams)

Then there's the Toyota Mirai, with first deliveries now announced for October.
Finally, Honda will release a production version of its hydrogen-powered FCV Concept sedan sometime this year, with first sales now expected in 2016.
That car will follow the very low-volume Honda FCX Clarity, of which about 60 were delivered in the U.S. from 2008 through 2014.

Powering the future

Hydrogen fuel cell vehicles could change mobility forever

Around the world, efforts are being made to harness the power of hydrogen,
the most abundant element in the universe.
Recognizing hydrogen’s vast potential as a clean energy source,
Toyota is actively developing and producing fuel cell vehicles (FCV).
We believe hydrogen can help us contribute to
the next 100 years of the automobile.

Fuel cell vehicles are leading innovation
in two key areas.

Depending on how we embrace fuel cell vehicles and hydrogen as an energy source,
the potential results could change the world and bring about innovations that far exceed even those of the Prius.

Toyota sees great potential in hydrogen
and fuel cell vehicles.

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What is a fuel cell vehicle?

Through the chemical reaction between hydrogen and oxygen, fuel cell vehicles generate electricity to power a motor. Instead of gasoline they are fuelled by hydrogen, an environment-friendly energy source that can be produced from a variety of raw materials.
Toyota’s efforts to make sustainable mobility a reality with hydrogen started in 1992, even before the release of the Prius. In 2002, Toyota began the world’s first limited sales of a fuel cell vehicle, the “Toyota FCHV”, in Japan and the U.S. Toyota has also made use of its hybrid vehicle technology in the development of fuel cell vehicles.

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Hydrogen and oxygen from the air are pulled into the fuel cells in the FC Stack, and electricity is created through a chemical reaction. The result: a responsive—and emission-free—drive.

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Fuel cell vehicles: not just eco-cars

In addition to excellent environmental credentials, fuel cell vehicles are fun to drive, and also offer convenience and performance.

Pioneering development, starting with the fuel cell manufacturing process.

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The Mirai, the world’s first fuel cell vehicle
for the mass market

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The Toyota Fuel Cell System (TFCS) moves the Mirai

The Mirai features the Toyota Fuel Cell System, which combines fuel cell technology with hybrid technology.
The system is more energy efficient than internal combustion engines, and offers excellent environmental performance without emitting CO₂ or other harmful substances during driving. At the same time, the system gives vehicles convenience on a par with conventional gasoline engine vehicles, thanks to a cruising range^*1 of roughly 650 km and a refueling time of about three minutes^*2.
In addition, the Mirai can serve as a high capacity power supply during emergencies. It is capable of supplying roughly 60 kWh^*3 of electricity, with a maximum DC power output of 9 kW^*4. When a separately-sold power supply unit is connected, the Mirai converts the DC power from the CHAdeMO power socket located inside the trunk to AC power and can power a vehicle-to-home^*5 system or a vehicle-to-load system. Consumer electronics can also be connected directly and used from the interior accessory socket (AC 100 V, 1,500 W).

*1 According to Toyota measurements based on the Japanese Ministry of Land, Infrastructure, Transport and Tourism's JC08 test cycle; measured by Toyota when refueling at a hydrogen station supplying hydrogen at a pressure of 70 MPa under the SAEe J2601 standard conditions (ambient temperature: 20° C, hydrogen tank pressure when fueled: 10 MPa). Differing amounts of hydrogen will be supplied to the tank if refueling is carried out at hydrogen stations with differing specifications, and the cruising range will therefore also differ accordingly. It is estimated that a cruising range of approximately 700 km can be achieved when fueled under the conditions above at new hydrogen stations scheduled to begin operation from FY2016. Possible cruising range may vary considerably due to usage conditions (weather, traffic congestion, etc.) and driving methods (quick starts, air conditioning, etc.).
*2 As measured by Toyota when refueling at a hydrogen station supplying hydrogen at a pressure of 70 MPa under the SAEe J2601 Standard conditions (ambient temperature: 20°C, hydrogen tank pressure when fueled: 10 MPa). Time will vary depending on hydrogen fueling pressure and ambient temperature.
*3 After DC/AC conversion by power supply unit. Power supply capacity varies according to power supply unit conversion efficiency, amount of remaining hydrogen and power consumption.
*4 Power supply capability varies according to power supply unit specifications (amount of power supplied cannot exceed power supply unit specifications).
*5 Specific residential wiring is required.

A new driving sensation

Fuel cell vehicles offer excellent drivability. This is the result of the fusion of a painstaking design process. The Mirai offers a low center of gravity, aerodynamic performance, optimal weight layout, and a highly rigid body. These features, combined with the car’s engineless, motor-driven performance, create a driving experience that is smooth, safe, quiet and fun.

Design based on experience and knowledge

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The unique and impressive design of the Mirai is perfect for a fuel cell vehicle:
it reflects the revolutionary nature of the technology.

Toyota’s in-house fuel cell technology development

Whereas many manufacturers procure high-pressure hydrogen tanks, etc., from outside sources, Toyota is developing its FC system (including the FC stack) in-house.
Our dedication to manufacturing always drives us to do as much as we can ourselves.

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FCV video gallery

• Driving Performance
• FC Stack and Technical Information