Fuel Cell
Content
Fuel Cell for Telecom Applications: A Low Cost Green Back-up Power System Alternative to Diesel Generators
Ram Krishna Dy. Director General (FLA) TEC New Delhi, DoT, Govt. of India. E-mail: [email protected] Naveen Kumar Asstt. Director General (FLA) TEC New Delhi, DoT, Govt. of India. E-mail: [email protected] Mrs. Laxmi Director (FLA) TEC New Delhi, DoT, Govt. of India E-mail: [email protected]
Abstract
With the rapid expansion of wireless communication systems worldwide, and the increasing socio-economic benefits of mobile phone technology, the need for dependable and economical backup power is critical. Electric grid loss throughout the year, whether from severe weather, natural disasters, or limited grid capacity, is an ongoing challenge for network operators. Fortunately, clean fuel cell technology has been developed to solve the limitations of traditional backup power solutions. Telecommunications companies are installing fuel cells at cell phone, radio towers etc. The possibilities are endless and there are many other uses for fuel cells nowadays. Fuel cells are powering buses, boats, trains, planes, scooters, bicycles etc. There are fuel cell-powered vending machines, vacuum cleaners and highway road signs. Miniature fuel cells for cellular phones, laptop computers and portable electronics are on their way to market. Hospitals, credit card centers, police stations, and banks are all using fuel cells to provide power to their facilities. Wastewater treatment plants and landfills are using fuel cells to convert the methane gas they produce into electricity. The paper explains in depth how the use of Fuel cell is beneficial for Telecom applications.
Key Words
Fuel Cell, Telecommunications, Temperature, Oxygen, Hydrogen, Electrolyte, Electricity, Green Power, Electric grid, clean fuel.
1.
Introduction
Traditional telecom backup power solutions include VRLA batteries for short duration backup and diesel generators for longer duration backup. Batteries are relatively inexpensive for 1 to 2 hours of backup power. However, batteries are not ideal for longer
Page 1 of 10
duration backup power applications because they can be expensive to maintain, unreliable after aging, temperature sensitive and hazardous to the environment after disposal. Diesel generators are capable of longer duration backup power. However, generators can be unreliable, maintenance intensive, and emit high levels of pollution and greenhouse gases into the atmosphere. Last but not the least is the high level of Diesel pilferage that occurs from the storage area that is used for running the DG sets. Fuel cells are reliable and quiet, with fewer moving parts than a generator, and a wider operating temperature range, -40°C to +50°C, than a battery. In addition, a fuel cell system has a lower lifetime cost than a generator. The lower costs for the fuel cell are the result of only one maintenance visit per year and significantly higher system efficiency. Finally, the fuel cell is the clean technology solution with minimal environmental impact. Fuel cell systems provide backup power to critical communication network infrastructures in wireless, fixed and broadband telecom applications ranging from 250 W to 15 KW, and they offer many outstanding features.
The fuel cell will compete with many other energy conversion devices, including the gas turbine power plant, the gasoline engine in car and the battery in laptop. Combustion engines like the turbine and the gasoline engine burn fuels and use the pressure created by the expansion of the gases to do mechanical work. Batteries convert chemical energy back into electrical energy when needed. Fuel cell does both tasks more efficiently. A fuel cell provides a DC (direct current) voltage that can be used to power motors, lights or any number of electrical appliances.
1.1
What is a Fuel Cell?
A fuel cell is a device that generates electricity by a chemical reaction. In principle, a fuel cell operates like a battery. Unlike a battery, a fuel cell does not run down or require recharging. It will produce energy in the form of electricity and heat as long as fuel is supplied. 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. The chemical reactions that produce this current are the key to how a fuel cell works.
1.2
How does Fuel Cell work?
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.
Page 2 of 10
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. A fuel cell consists of two electrodes sandwiched around an electrolyte. Oxygen passes over one electrode and hydrogen over the other, generating electricity, water and heat.
Hydrogen fuel is fed into the "anode" of the fuel cell. Oxygen (or air) enters the fuel cell through the cathode. Encouraged by a catalyst, the hydrogen atom splits into a proton and an electron, which take different paths to the cathode. The proton passes through the electrolyte. The electrons create a separate current that can be utilized before they return to the cathode, to be reunited with the hydrogen and oxygen in a molecule of water. 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.
Fig. 1
A single fuel cell generates a tiny amount of direct current (DC) electricity. In practice, many fuel cells are usually assembled into a stack. The system continuously senses the direct current (dc) bus voltage and seamlessly takes over critical loads if the dc bus falls below a customer determined set point. The system is fueled by hydrogen, which is
Page 3 of 10
delivered to the fuel cell stack in one of two ways – either from a commercial-grade hydrogen supply or Hydroplus, methanol and water liquid fuel, using an integrated reformer system. Electricity is generated by the fuel cell stack as direct current. The dc energy is passed to a dc/dc converter, which converts the unregulated dc electricity from the fuel cell stack into high-quality regulated dc electricity to serve the required loads.
Fig. 2
If alternating current (AC) is needed, the DC output of the fuel cell must be routed through a conversion device called an inverter. 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. 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.
2.
Types of Fuel Cells
There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified by their operating temperature and the type of electrolyte they use. Some types of fuel cells work well for use in stationary power generation plants. Others may be useful for small portable applications or for powering cars. The main types of fuel cells include: -
Page 4 of 10
2.1
Polymer Exchange Membrane Fuel Cell (PEMFC)
The PEMFC has a high power density and a relatively low operating temperature (ranging from 60 to 80 degrees Celsius, or 140 to 176 degrees Fahrenheit). The low operating temperature means that it doesn't take very long for the fuel cell to warm up and begin generating electricity.
2.2
Solid Oxide Fuel Cell (SOFC)
These fuel cells are best suited for large-scale stationary power generators that could provide electricity for factories or towns. This type of fuel cell operates at very high temperatures (between 700 and 1,000 degrees Celsius). This high temperature makes reliability a problem, because parts of the fuel cell can break down after cycling on and off repeatedly. However, solid oxide fuel cells are very stable when in continuous use. In fact, the SOFC has demonstrated the longest operating life of any fuel cell under certain operating conditions. The high temperature also has an advantage, the steam produced by the fuel cell can be channeled into turbines to generate more electricity. This process is called co-generation of heat and power (CHP) and it improves the overall efficiency of the system.
2.3
Alkaline Fuel Cell (AFC)
This is one of the oldest designs for fuel cells, the United States space program has used them since the 1960s. The AFC is very susceptible to contamination, so it requires pure hydrogen and oxygen. It is also very expensive, so this type of fuel cell is unlikely to be commercialized.
2.4
Molten-Carbonate Fuel Cell (MCFC)
Like the SOFC, these fuel cells are also best suited for large stationary power generators. They operate at 600 degrees Celsius, so they can generate steam that can be used to generate more power. They have a lower operating temperature than solid oxide fuel cells, which means they don't need such exotic materials. This makes the design a little less expensive.
2.5
Phosphoric-Acid Fuel Cell (PAFC)
The phosphoric-acid fuel cell has potential for use in small stationary power-generation systems. It operates at a higher temperature than polymer exchange membrane fuel cells, so it has a longer warm-up time. This makes it unsuitable for use in cars.
Page 5 of 10
2.6
Direct-Methanol Fuel Cell (DMFC)
Methanol fuel cells are comparable to a PEMFC in regards to operating temperature, but are not as efficient. Also, the DMFC requires a relatively large amount of platinum to act as a catalyst, which makes these fuel cells expensive.
2.7
Polymer Exchange Membrane Fuel Cells (PEMFC)
The polymer exchange membrane fuel cell (PEMFC) is one of the most promising fuel cell technologies. This type of fuel cell will probably end up powering cars, buses and maybe even houses. The PEMFC uses one of the simplest reactions of any fuel cell.
Fig. 3: Parts of a PEM fuel cell
3.
Benefits of Fuel Cells for Telecommunication
(i) Autonomy – Fuel cells are able to operate as long as there is available fuel, so whether an 8 hour, 1 day or 3 day extended runtime is required, enough fuel can be stored onsite. (ii) Remote monitoring – Fuel cells can be fully monitored from one central location
alerting the operator as to when the system is in use and how long before refuelling is required to ensure no downtime. (iii) Space requirement –The space required for the same period of runtime is
considerably less for fuel cells than for battery banks. Fuel cells do not require cooling like batteries which eliminates the need for spacious cooling systems. (iv) Fuels - The majority of these systems operate on hydrogen (in this instance the only
emission is water), which can be generated from renewable sources (electrolysis) or from reformed hydrocarbons (methanol, propane, ammonia and natural gas).
Page 6 of 10
(v)
Temperature tolerance – Unlike batteries, fuel cells do not degrade a high
temperatures and their range can be between - 40°C and +50°C without any cooling required. (vi) Integration – Fuel cell systems provided as either a standalone unit similar in size to
a small refrigerator (for applications like base stations) or can be inserted in existing 19” racks. So Fuel Cells are fit for outdoor as well as indoor applications. (vii) Cost – Over the lifetime of the unit can offer cost savings over existing technologies. This include: maintenance, repairs, transport and disposal (viii) Reliability - In many cases, fuel cells are able to offer higher reliability and MTBF (Mean Time between Failures) and there is no degradation of voltage over time. Failures tend to be less critical and easily dealt with. (ix) Environmental – Unlike generators, fuel cells do not use combustion and therefore
there are no NOx, SOx or particulate emissions from the unit. So the Fuel Cells provide Clean Energy and hence the Green Energy. (x) Maintenance – Fuel cells have very few moving parts which reduces the need for
regular maintenance.
4.
Other Telecom Applications of Fuel Cell
Fuel Cells have other applications in Telecom field. Some of the Telecom applications of Fuel cell are as under:
(i)
Portable Power
Fuel cells can provide power where no electric grid is available, plus they are quiet, so using one instead of a loud, polluting generator at a site would not only save emissions, but it won't disturb nature, or your site neighbours. Portable fuel cells are also being used in emergency backup power situations and military applications. They are much lighter than batteries and last a lot longer, especially imporant to soldiers carrying heavy equipment in the field.
(ii)
Consumer Electronics
Fuel cells will change the telecommuting world, powering cellular phones, laptops and palm pilots hours longer than batteries. Companies have already demonstrated fuel cells that can power cell phones for 30 days without recharging and laptops for 20 hours. Other applications for micro fuel cells include video recorders, portable power tools, and low power remote devices such as hearing aids, smoke detectors, burglar alarms, hotel locks
Page 7 of 10
and meter readers. These miniature fuel cells generally run on methanol, an inexpensive wood alcohol also used in windshield wiper fluid.
5.
Environmental impact of Fuel Cell based System
Three key factors of the Fuel cell based system on the environment must be considered. • • • First, distilled water is the only byproduct of the electrochemical process taking place in the fuel cell, whereas diesel engines produce polluting exhaust fumes. Second there are no toxic wastes to be disposed, such as acids and lead present in all batteries. Lastly the elimination of logistics related activities allow for an intrinsic benefit on the environment not needing to transport any fuel to the site.
6.
Constraints
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 and 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 require 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.
7.
Extended Run Solutions
The fuel cell can support backup power requirements of days versus hours by using a liquid fuel. Bottled hydrogen is appropriate and cost effective for many backup power applications, but when critical backup power systems need to operate for more than 8
Page 8 of 10
hours, or hydrogen storage is not practical or in remote locations where hydrogen delivery is not feasible, a compact liquid fuel system is a more practical solution. The fuel used to operate the extended run fuel reformer is a fuel mixture of methanol and water. Methanol is a readily available, commercially produced fuel that is currently used in common applications such as windshield washer fluid, plastic bottles, engine additives, and latex paints, among others. Methanol is easily transported, water miscible, easily biodegradable and sulphur-free. It has a low freezing point (-71°C) and does not degrade when stored for a long time.
8.
Conclusion
With the use of computers, the Internet, and communication networks steadily increasing, there is a need for more reliable power than is available on the current electrical grid, and fuel cells have proven to be up to 99.999% (five nines) reliable. Fuel cells can replace batteries to provide power for 1kW to 5kW telecom sites without noise or emissions, and are durable, providing power in sites that are either hard to access or are subject to inclement weather. Such systems can be used to provide primary or backup power for telecom switch nodes, cell towers, and other electronic systems that would benefit from onsite, direct DC power supply. Network operators are increasingly choosing fuel cells as their backup power solution because they are lower cost, reliable, low maintenance, and because they are a clean energy contributing to global reduction in carbon footprint. Fuel Cell systems are used today to back up critical communication network infrastructures in wireless, fixed and broadband telecom applications.
References
(i) (ii) (iii) Appleby, A. John. Fuel Cell Handbook. New York: Van Reinhold Co., 1989. Blomen, Leo, and Michael Mugerwa. Fuel Cell Systems. New York: Plenum Press, 1993. Breeze, Paul. Power Generation Technologies: Evaluating the Cost of Electricity. London: Financial Times Energy, 1998. (iv) Hacker, Barton C. and James M. Grimwood. On the Shoulders of Titans: a history of Project Gemini. NASA: Washington, DC, 1977. (v) Kordesch, Karl, and Günter Simader. Fuel Cells and Their Applications. New York: VCH, 1996. (vi) (vii) Linden, David. Handbook of Batteries and Fuel Cells. New York: McGraw-Hill, about 1984. Lischka, J. R. Ludwig Mond and the British alkali industry. New York: Garland, 1985.
Page 9 of 10
(viii)
Norbeck, Joseph. Hydrogen Fuel for Surface Transportation. Warrendale, PA: Society of Automotive Engineers, about 1996.
(ix)
Ostwald, Wilhelm. Electrochemistry: History and Theory. Translated by N. P. Date. New Delhi: Amerind for the Smithsonian Institution and the National Science Foundation, 1980.
(x)
Young, George J., ed. Fuel Cells, 2 volumes. New York: Reinhold Publishing Corp., V1 1959, V2 - 1961). Both volumes reprint papers given at symposia in 1959 and 1961, respectively.
(xi)
U.S. Department of Energy. Fuel Cells for the 21st Century: Collaboration for a Leap in Efficiency and Cost Reduction. Morgantown, WV: US DoE, 1999.
(xii)
Wendel, Charles H. The Allis-Chalmers Story. Sarasota, Florida: Crestline Publishing Co., 1988.
(xiii)
Nice, Karim, and Jonathan Strickland. "How Fuel Cells Work", 18 September 2000. HowStuffWorks.com <http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-
cell.htm> 13 January 2012.
Page 10 of 10
Ram Krishna Dy. Director General (FLA) TEC New Delhi, DoT, Govt. of India. E-mail: [email protected] Naveen Kumar Asstt. Director General (FLA) TEC New Delhi, DoT, Govt. of India. E-mail: [email protected] Mrs. Laxmi Director (FLA) TEC New Delhi, DoT, Govt. of India E-mail: [email protected]
Abstract
With the rapid expansion of wireless communication systems worldwide, and the increasing socio-economic benefits of mobile phone technology, the need for dependable and economical backup power is critical. Electric grid loss throughout the year, whether from severe weather, natural disasters, or limited grid capacity, is an ongoing challenge for network operators. Fortunately, clean fuel cell technology has been developed to solve the limitations of traditional backup power solutions. Telecommunications companies are installing fuel cells at cell phone, radio towers etc. The possibilities are endless and there are many other uses for fuel cells nowadays. Fuel cells are powering buses, boats, trains, planes, scooters, bicycles etc. There are fuel cell-powered vending machines, vacuum cleaners and highway road signs. Miniature fuel cells for cellular phones, laptop computers and portable electronics are on their way to market. Hospitals, credit card centers, police stations, and banks are all using fuel cells to provide power to their facilities. Wastewater treatment plants and landfills are using fuel cells to convert the methane gas they produce into electricity. The paper explains in depth how the use of Fuel cell is beneficial for Telecom applications.
Key Words
Fuel Cell, Telecommunications, Temperature, Oxygen, Hydrogen, Electrolyte, Electricity, Green Power, Electric grid, clean fuel.
1.
Introduction
Traditional telecom backup power solutions include VRLA batteries for short duration backup and diesel generators for longer duration backup. Batteries are relatively inexpensive for 1 to 2 hours of backup power. However, batteries are not ideal for longer
Page 1 of 10
duration backup power applications because they can be expensive to maintain, unreliable after aging, temperature sensitive and hazardous to the environment after disposal. Diesel generators are capable of longer duration backup power. However, generators can be unreliable, maintenance intensive, and emit high levels of pollution and greenhouse gases into the atmosphere. Last but not the least is the high level of Diesel pilferage that occurs from the storage area that is used for running the DG sets. Fuel cells are reliable and quiet, with fewer moving parts than a generator, and a wider operating temperature range, -40°C to +50°C, than a battery. In addition, a fuel cell system has a lower lifetime cost than a generator. The lower costs for the fuel cell are the result of only one maintenance visit per year and significantly higher system efficiency. Finally, the fuel cell is the clean technology solution with minimal environmental impact. Fuel cell systems provide backup power to critical communication network infrastructures in wireless, fixed and broadband telecom applications ranging from 250 W to 15 KW, and they offer many outstanding features.
The fuel cell will compete with many other energy conversion devices, including the gas turbine power plant, the gasoline engine in car and the battery in laptop. Combustion engines like the turbine and the gasoline engine burn fuels and use the pressure created by the expansion of the gases to do mechanical work. Batteries convert chemical energy back into electrical energy when needed. Fuel cell does both tasks more efficiently. A fuel cell provides a DC (direct current) voltage that can be used to power motors, lights or any number of electrical appliances.
1.1
What is a Fuel Cell?
A fuel cell is a device that generates electricity by a chemical reaction. In principle, a fuel cell operates like a battery. Unlike a battery, a fuel cell does not run down or require recharging. It will produce energy in the form of electricity and heat as long as fuel is supplied. 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. The chemical reactions that produce this current are the key to how a fuel cell works.
1.2
How does Fuel Cell work?
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.
Page 2 of 10
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. A fuel cell consists of two electrodes sandwiched around an electrolyte. Oxygen passes over one electrode and hydrogen over the other, generating electricity, water and heat.
Hydrogen fuel is fed into the "anode" of the fuel cell. Oxygen (or air) enters the fuel cell through the cathode. Encouraged by a catalyst, the hydrogen atom splits into a proton and an electron, which take different paths to the cathode. The proton passes through the electrolyte. The electrons create a separate current that can be utilized before they return to the cathode, to be reunited with the hydrogen and oxygen in a molecule of water. 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.
Fig. 1
A single fuel cell generates a tiny amount of direct current (DC) electricity. In practice, many fuel cells are usually assembled into a stack. The system continuously senses the direct current (dc) bus voltage and seamlessly takes over critical loads if the dc bus falls below a customer determined set point. The system is fueled by hydrogen, which is
Page 3 of 10
delivered to the fuel cell stack in one of two ways – either from a commercial-grade hydrogen supply or Hydroplus, methanol and water liquid fuel, using an integrated reformer system. Electricity is generated by the fuel cell stack as direct current. The dc energy is passed to a dc/dc converter, which converts the unregulated dc electricity from the fuel cell stack into high-quality regulated dc electricity to serve the required loads.
Fig. 2
If alternating current (AC) is needed, the DC output of the fuel cell must be routed through a conversion device called an inverter. 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. 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.
2.
Types of Fuel Cells
There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified by their operating temperature and the type of electrolyte they use. Some types of fuel cells work well for use in stationary power generation plants. Others may be useful for small portable applications or for powering cars. The main types of fuel cells include: -
Page 4 of 10
2.1
Polymer Exchange Membrane Fuel Cell (PEMFC)
The PEMFC has a high power density and a relatively low operating temperature (ranging from 60 to 80 degrees Celsius, or 140 to 176 degrees Fahrenheit). The low operating temperature means that it doesn't take very long for the fuel cell to warm up and begin generating electricity.
2.2
Solid Oxide Fuel Cell (SOFC)
These fuel cells are best suited for large-scale stationary power generators that could provide electricity for factories or towns. This type of fuel cell operates at very high temperatures (between 700 and 1,000 degrees Celsius). This high temperature makes reliability a problem, because parts of the fuel cell can break down after cycling on and off repeatedly. However, solid oxide fuel cells are very stable when in continuous use. In fact, the SOFC has demonstrated the longest operating life of any fuel cell under certain operating conditions. The high temperature also has an advantage, the steam produced by the fuel cell can be channeled into turbines to generate more electricity. This process is called co-generation of heat and power (CHP) and it improves the overall efficiency of the system.
2.3
Alkaline Fuel Cell (AFC)
This is one of the oldest designs for fuel cells, the United States space program has used them since the 1960s. The AFC is very susceptible to contamination, so it requires pure hydrogen and oxygen. It is also very expensive, so this type of fuel cell is unlikely to be commercialized.
2.4
Molten-Carbonate Fuel Cell (MCFC)
Like the SOFC, these fuel cells are also best suited for large stationary power generators. They operate at 600 degrees Celsius, so they can generate steam that can be used to generate more power. They have a lower operating temperature than solid oxide fuel cells, which means they don't need such exotic materials. This makes the design a little less expensive.
2.5
Phosphoric-Acid Fuel Cell (PAFC)
The phosphoric-acid fuel cell has potential for use in small stationary power-generation systems. It operates at a higher temperature than polymer exchange membrane fuel cells, so it has a longer warm-up time. This makes it unsuitable for use in cars.
Page 5 of 10
2.6
Direct-Methanol Fuel Cell (DMFC)
Methanol fuel cells are comparable to a PEMFC in regards to operating temperature, but are not as efficient. Also, the DMFC requires a relatively large amount of platinum to act as a catalyst, which makes these fuel cells expensive.
2.7
Polymer Exchange Membrane Fuel Cells (PEMFC)
The polymer exchange membrane fuel cell (PEMFC) is one of the most promising fuel cell technologies. This type of fuel cell will probably end up powering cars, buses and maybe even houses. The PEMFC uses one of the simplest reactions of any fuel cell.
Fig. 3: Parts of a PEM fuel cell
3.
Benefits of Fuel Cells for Telecommunication
(i) Autonomy – Fuel cells are able to operate as long as there is available fuel, so whether an 8 hour, 1 day or 3 day extended runtime is required, enough fuel can be stored onsite. (ii) Remote monitoring – Fuel cells can be fully monitored from one central location
alerting the operator as to when the system is in use and how long before refuelling is required to ensure no downtime. (iii) Space requirement –The space required for the same period of runtime is
considerably less for fuel cells than for battery banks. Fuel cells do not require cooling like batteries which eliminates the need for spacious cooling systems. (iv) Fuels - The majority of these systems operate on hydrogen (in this instance the only
emission is water), which can be generated from renewable sources (electrolysis) or from reformed hydrocarbons (methanol, propane, ammonia and natural gas).
Page 6 of 10
(v)
Temperature tolerance – Unlike batteries, fuel cells do not degrade a high
temperatures and their range can be between - 40°C and +50°C without any cooling required. (vi) Integration – Fuel cell systems provided as either a standalone unit similar in size to
a small refrigerator (for applications like base stations) or can be inserted in existing 19” racks. So Fuel Cells are fit for outdoor as well as indoor applications. (vii) Cost – Over the lifetime of the unit can offer cost savings over existing technologies. This include: maintenance, repairs, transport and disposal (viii) Reliability - In many cases, fuel cells are able to offer higher reliability and MTBF (Mean Time between Failures) and there is no degradation of voltage over time. Failures tend to be less critical and easily dealt with. (ix) Environmental – Unlike generators, fuel cells do not use combustion and therefore
there are no NOx, SOx or particulate emissions from the unit. So the Fuel Cells provide Clean Energy and hence the Green Energy. (x) Maintenance – Fuel cells have very few moving parts which reduces the need for
regular maintenance.
4.
Other Telecom Applications of Fuel Cell
Fuel Cells have other applications in Telecom field. Some of the Telecom applications of Fuel cell are as under:
(i)
Portable Power
Fuel cells can provide power where no electric grid is available, plus they are quiet, so using one instead of a loud, polluting generator at a site would not only save emissions, but it won't disturb nature, or your site neighbours. Portable fuel cells are also being used in emergency backup power situations and military applications. They are much lighter than batteries and last a lot longer, especially imporant to soldiers carrying heavy equipment in the field.
(ii)
Consumer Electronics
Fuel cells will change the telecommuting world, powering cellular phones, laptops and palm pilots hours longer than batteries. Companies have already demonstrated fuel cells that can power cell phones for 30 days without recharging and laptops for 20 hours. Other applications for micro fuel cells include video recorders, portable power tools, and low power remote devices such as hearing aids, smoke detectors, burglar alarms, hotel locks
Page 7 of 10
and meter readers. These miniature fuel cells generally run on methanol, an inexpensive wood alcohol also used in windshield wiper fluid.
5.
Environmental impact of Fuel Cell based System
Three key factors of the Fuel cell based system on the environment must be considered. • • • First, distilled water is the only byproduct of the electrochemical process taking place in the fuel cell, whereas diesel engines produce polluting exhaust fumes. Second there are no toxic wastes to be disposed, such as acids and lead present in all batteries. Lastly the elimination of logistics related activities allow for an intrinsic benefit on the environment not needing to transport any fuel to the site.
6.
Constraints
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 and 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 require 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.
7.
Extended Run Solutions
The fuel cell can support backup power requirements of days versus hours by using a liquid fuel. Bottled hydrogen is appropriate and cost effective for many backup power applications, but when critical backup power systems need to operate for more than 8
Page 8 of 10
hours, or hydrogen storage is not practical or in remote locations where hydrogen delivery is not feasible, a compact liquid fuel system is a more practical solution. The fuel used to operate the extended run fuel reformer is a fuel mixture of methanol and water. Methanol is a readily available, commercially produced fuel that is currently used in common applications such as windshield washer fluid, plastic bottles, engine additives, and latex paints, among others. Methanol is easily transported, water miscible, easily biodegradable and sulphur-free. It has a low freezing point (-71°C) and does not degrade when stored for a long time.
8.
Conclusion
With the use of computers, the Internet, and communication networks steadily increasing, there is a need for more reliable power than is available on the current electrical grid, and fuel cells have proven to be up to 99.999% (five nines) reliable. Fuel cells can replace batteries to provide power for 1kW to 5kW telecom sites without noise or emissions, and are durable, providing power in sites that are either hard to access or are subject to inclement weather. Such systems can be used to provide primary or backup power for telecom switch nodes, cell towers, and other electronic systems that would benefit from onsite, direct DC power supply. Network operators are increasingly choosing fuel cells as their backup power solution because they are lower cost, reliable, low maintenance, and because they are a clean energy contributing to global reduction in carbon footprint. Fuel Cell systems are used today to back up critical communication network infrastructures in wireless, fixed and broadband telecom applications.
References
(i) (ii) (iii) Appleby, A. John. Fuel Cell Handbook. New York: Van Reinhold Co., 1989. Blomen, Leo, and Michael Mugerwa. Fuel Cell Systems. New York: Plenum Press, 1993. Breeze, Paul. Power Generation Technologies: Evaluating the Cost of Electricity. London: Financial Times Energy, 1998. (iv) Hacker, Barton C. and James M. Grimwood. On the Shoulders of Titans: a history of Project Gemini. NASA: Washington, DC, 1977. (v) Kordesch, Karl, and Günter Simader. Fuel Cells and Their Applications. New York: VCH, 1996. (vi) (vii) Linden, David. Handbook of Batteries and Fuel Cells. New York: McGraw-Hill, about 1984. Lischka, J. R. Ludwig Mond and the British alkali industry. New York: Garland, 1985.
Page 9 of 10
(viii)
Norbeck, Joseph. Hydrogen Fuel for Surface Transportation. Warrendale, PA: Society of Automotive Engineers, about 1996.
(ix)
Ostwald, Wilhelm. Electrochemistry: History and Theory. Translated by N. P. Date. New Delhi: Amerind for the Smithsonian Institution and the National Science Foundation, 1980.
(x)
Young, George J., ed. Fuel Cells, 2 volumes. New York: Reinhold Publishing Corp., V1 1959, V2 - 1961). Both volumes reprint papers given at symposia in 1959 and 1961, respectively.
(xi)
U.S. Department of Energy. Fuel Cells for the 21st Century: Collaboration for a Leap in Efficiency and Cost Reduction. Morgantown, WV: US DoE, 1999.
(xii)
Wendel, Charles H. The Allis-Chalmers Story. Sarasota, Florida: Crestline Publishing Co., 1988.
(xiii)
Nice, Karim, and Jonathan Strickland. "How Fuel Cells Work", 18 September 2000. HowStuffWorks.com <http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-
cell.htm> 13 January 2012.
Page 10 of 10
