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How Hydrogen Fuel cells work.
HYDROGEN FUEL CELLS
A fuel cell is an electrochemical device that combines hydrogen fuel and oxygen from the air to produce electricity, heat and water. Fuel
cells operate without combustion (exothermic reaction), so they are virtually pollution free. Since the fuel is converted directly to electricity,
a fuel cell can operate at much higher efficiencies than internal combustion engines, extracting more electricity from the same
amount of fuel. The fuel cell itself has no moving parts - making it a quiet and reliable source of power.
The fuel cell is composed of an anode (a negative electrode that repels electrons), an electrolyte membrane in the center, and a cathode
(a positive electrode that attracts electrons).
As hydrogen flows into the fuel cell anode, platinum coating on the anode helps to separate the gas into protons (hydrogen ions) and
electrons. The electrolyte membrane in the center allows only the protons to pass through the membrane to the cathode side of the fuel
cell. The electrons cannot pass through this membrane and flow through an external circuit in the form of electric current. This current
can power an electric load, such as the light bulb shown here.
As oxygen flows into the fuel cell cathode, another platinum coating helps the oxygen, protons, and electrons combine to produce pure
water and heat.
Individual fuel cells can be then combined into a fuel cell "stack". The number of fuel cells in the stack determines the total voltage,
and the surface area of each cell determines the total current. Multiplying the voltage by the current yields the total electrical
power generated.
HOW FUEL CELLS WORK
A fuel cell produces electricity by means of an electrochemical reaction much like a battery. But there is an important difference. Rather
than extracting the chemical reactants from the plates inside the cells, a fuel cell uses hydrogen fuel and oxygen extracted from the air to
produce electricity. As long as these substances are fed into the fuel cell, it will continue to generate electric power.
1. Hydrogen gas is extracted from natural gas or other
hydrocarbon fuels and permeates the anode (-). Oxygen
from the air permeates the cathode (+).
2. Aided by a catalyst (platinum) in the anode, electrons
are stripped from the hydrogen. Hydrogen ions
pass into the electrolyte (Phosphoric acid).
3. Electrons cannot enter the electrolyte. They travel
through an external circuit, producing electricity.
4. Electrons travel back to the cathode where they
combine with hydrogen ions and oxygen from water.
A fuel cell provides DC (direct current) voltage that
can be used to power motors, lights or other electrical
appliances. To supply electricity for homes, businesses,
and buildings, however, the direct current must
be changed into AC (alternating current). A device
called an "inverter" makes this conversion.
Hydrogen needed by a fuel cell can be extracted from a
variety of fuels. Natural gas - a chemical combination
of carbon and hydrogen atoms - is perhaps the most
common fuel, but other hydrocarbon fuels can also be
used. For example, some fuel cells operate on gases
released from wasterwater digesters or from landfills.
In the future, gas made from coal or biomass might be
candidate fuels. Some types of fuel cells extract the
hydrogen in a separate fuel processor called a
"reformer;" other fuel cells incorporate reforming in-side
the cell stack itself.
*** The PC25 TM system is the world's only commercially available fuel cell power system. This type of Fuel Cell that is located at NAIT
will produce 200 kW of electricity at 480V where it will be stepped up to the system voltage of 600V ( **this is enough electricity for
approx. 100 houses), and will also produce approx. 900,000 BTU of low temperature (140 deg F) heat. It will also be used to assist heat-ing
through heat exchangers of the NAIT swimming pool, the Student Activities DHW and the power plant boiler cold water boiler feed-water
make-up. High temperature heat from the Fuel Cell at 500,00 BTU and approx. 250 deg F, will be used to assist in heating return
boiler condensate of 140 deg. through a heat exchanger to approx. 170 deg. F, where the deaerator will heat the condensate to 220 deg. F
for the return boiler feedwater to the steam boilers.
Note: This is the first hydrogen Fuel Cell in Canada of this magnitude. NAIT is currently in the process of obtaining the next generation
‘solid oxide’ fuel cell (a 5 kW unit) that will be used to train Power Engineering students. The unit is expected to be on site and in operation
by July 2004., as part of the Power Engineering training program.
Experience and Proven Performance In Fuel Cell Power
(www.internationalfuelcells.com/commercial/pc25summary.shtml)
UTC Fuel Cells, a unit of United Technologies Corp. (NYSE: UTX), is the world leader in fuel cell production and development for stationary,
transportation, residential and space applications.
UTC Fuel Cells is the sole supplier of fuel cells for U.S. space missions and has been producing a commercial fuel cell power plant since
1991.
UTC Fuel Cells and its licensees have delivered more than 250 of our 200-kilowatt fuel cell systems to customers in 19 countries and
five continents. PC25 systems provide clean, reliable power at a range of locations from a New York City police station to a major postal
facility in Alaska to a credit card processing system facility in Nebraska to a science center in Japan.
The systems also power schools, high-rise office buildings, and manufacturing sites and generate electricity from the emissions of sewage
treatment facilities and breweries. The PC25 fleet of fuel cells has accumulated more than 4.0 million hours of operational experience.
UTC Fuel Cells has the proven experience to meet your power needs.
BENEFITS OF THE PC25 TM FUEL CELL POWER PLANT
Highly Efficient -- 37 percent electrical efficiency; 90 percent with heat recovery.
Low Operating Cost -- The efficiency of the PC25 will reduce the operating costs (energy bill) of the building.
High Quality Power -- The electrical output is computer grade power. Meet critical power requirements without interruption.
Minimize lost productivity, lost revenue, product loss or opportunity cost.
Reduced Peripherals -- No need for UPS systems, rooms of lead-acid batteries, diesel generators, storage tanks, secondary
containment vessels, or additional HVAC requirements.
Green Power -- Fuel cell power installations are exempt from air emission permitting requirements in many U.S. states and provide
flexibility under many federal, state and local air pollution standards.
Operates in Diverse Climates -- PC25 units have operated in a range of climate condition and in temperatures ranging from -20°
F to 110°F.
Flexible Sitting Options -- Fuel cells can be sited indoors or outdoors. Valuable indoor space normally occupied by batteries
and UPS systems can be eliminated, translating into more available high rent space.
Low Emissions -- Fuel cells are the cleanest fossil-fueled generating technology available today. Well below air emission standards
in every state, including California. Each PC25 unit, when operating at its rated power, eliminates more than 40,000
pounds of air pollutants including NOx and SOx and two million pounds of CO2 emissions per year compared with typical US
combustion-based generators.
Quiet Operation -- (60 dB at 30 ft.) comparable to an outside air-conditioner.
Modular and Scalable -- As building needs change additional fuel cells can be added, optimizing up-front expense.
PC25C Performance Data
Features Characteristics
Rated Electrical Cap. 200 kW/235 kVA
Voltage and Frequency 480/277 V, 60 Hz, 3 Phase; 400/230 V, 50 Hz, 3 Phase
Fuel Consumption Natural Gas: 2,050 cu ft/hr @ 4-14” H20; Anaerobic Digester Gas: 3,200 cu ft/hr at 60% CH4
Efficiency (LHV Basis) 87% Total: 40% Electrical, 50% Thermal
Emissions <2 ppm CO, <1 ppm NOx and negligible SOx
Dimensions & Weight 900,000 Btu/hr @ 140 deg F; 450,000 Btu/hr @ 250 deg F
Sound Profile Conventional level (60 dBA @ 30 ft), acceptable inside
Dimensions & Weight Power Module - (10’ x 10’ x 18’, 40,000 lbs.)
Dimensions & Weight Cooling Module - (4’ x 14’ x4’, 1,700 lbs)
Grid Connected Mode Constant power output operation in parallel with grid. Automatic synchronization. Auto disconnect on grid
failure and provides independent operation.
Types of Fuel Cells :
Fuel cells are classified primarily by the kind of electrolyte they employ.
This determines the kind of chemical reactions that take place
in the cell, the kind of catalysts required, the temperature range in
which the cell operates, the fuel required, and other factors. These
characteristics, in turn, affect the applications for which these cells
are most suitable. There are several different types of fuel cells currently
under development, each with its own advantages, limitations,
and potential applications. A few of the most promising types include:
Polymer Electrolyte Membrane (PEM)
Phosphoric Acid (NAIT 2003)
Direct Methanol
Alkaline
Molten Carbonate
Solid Oxide (NAIT 2004)
Regenerative (Reversible)
First published in November/December 2003 Steamlines.
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