|
|||
 |
|||
|
We provide "Cooler, Cleaner, Greener" power and energy solutions that also include "Pollution Free Power" and "Carbon Free Energy" systems, and all provide "Renewable Energy Credits." We also offer energy-saving technologies that may include; Absorption Chillers, Adsorption Chillers, Automated Demand Response, Cogeneration, Demand Response Programs, Demand Side Management, Energy Master Planning, Engine Driven Chillers, Trigeneration and Energy Conservation Measures. Cooler, Cleaner, Greener Power & Energy Solutions project development services are one of our many specialties. These projects are Kyoto Protocol compliant and generate clean energy and significantly fewer greenhouse gas emissions. Unlike most companies, we are equipment supplier/vendor neutral. This means we help our clients select the best equipment for their specific application. This approach provides our customers with superior performance, decreased operating expenses and increased return on investment. Renewable
Energy Technologies provides
project development services that generate clean energy and
significantly reduce greenhouse
gas emissions and carbon
dioxide emissions. Included in this are our
turnkey "ecogeneration"
products and services which includes renewable
energy technologies, waste to
energy, waste to watts and waste
heat recovery solutions. Other project development
technologies include; Anaerobic
Digester, Anaerobic Lagoon, Biogas
Recovery, BioMethane, Biomass
Gasification, and Landfill Gas
To Energy, project development services.
For more information: call us at: 832-758-0027 We are Renewable Energy Technologies specialists and develop clean power and energy projects that will generate a "Renewable Energy Credit," Carbon Dioxide Credits and Emission Reduction Credits. Some of our products and services solutions and technologies include; Absorption Chillers, Adsorption Chillers, Automated Demand Response, Biodiesel Refineries, Biofuel Refineries, Biomass Gasification, BioMethane, Canola Biodiesel, Coconut Biodiesel, Cogeneration, Concentrating Solar Power, Demand Response Programs, Demand Side Management, Energy Conservation Measures, Energy Master Planning, Engine Driven Chillers, Geothermal Heatpumps, Groundsource Heatpumps, Solar CHP, Solar Cogeneration, Rapeseed Biodiesel, Solar Electric Heat Pumps, Solar Electric Power Systems, Solar Heating and Cooling, Solar Trigeneration, Soy Biodiesel, Trigeneration, and Watersource Heat Pumps. 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 types of fuel cells currently under development, each with its own advantages, limitations, and potential applications. What are Molten Carbonate Fuel Cells? Molten Carbonate Fuel Cells (MCFC) evolved from work in the 1960's aimed
at producing a fuel cell which would operate directly on coal. While
direct operation on coal seems less likely today, operation on
coal-derived fuel gases or natural gas is viable. Molten
Carbonate Fuel Cell Design
and Operation
Molten Carbonate Fuel Cells use a molten carbonate salt mixture as its
electrolyte. The composition of the electrolyte varies, but usually
consists of lithium carbonate and potassium carbonate. At the operating
temperature of about 1200°F (650°C), the salt mixture is liquid and a
good ionic conductor. The electrolyte is suspended in a porous,
insulating and chemically inert ceramic (LiA102) matrix. The
Molten Carbonate Fuel Cell reactions that occur are:
The
anode process involves a reaction between hydrogen and carbonate ions
(CO3=) from the electrolyte which produces water and carbon dioxide
(CO2) while releasing electrons to the anode. The cathode process
combines oxygen and CO2 from the oxidant stream with electrons from the
cathode to produce carbonate ions which enter the electrolyte. The need
for CO2 in the oxidant stream requires a system for collecting CO2 from
the anode exhaust and mixing it with the cathode feed stream.
As
the operating temperature increases, the theoretical operating voltage
for a fuel cell decreases and with it the maximum theoretical fuel
efficiency. On the other hand, increasing the operating temperature
increases the rate of the electrochemical reaction and thus the current
which can be obtained at a given voltage. The net effect for the
Molten Carbonate Fuel Cell is that the real operating voltage is higher than
the operating voltage for the Phosphoric
Acid Fuel Cell at the same current density. The
higher operating voltage of the Molten
Carbonate Fuel Cell means that
more power is available at a higher fuel efficiency from a Molten
Carbonate Fuel Cell than from a Phosphoric
Acid Fuel Cell of the same electrode area. As size
and cost scale roughly with electrode area, this suggests that a Molten
Carbonate Fuel Cell should be smaller and less expensive than a
"comparable" Phosphoric
Acid Fuel Cell. The
Molten
Carbonate Fuel Cell also produces excess heat at a temperature
which is high enough to yield high pressure steam which may be fed to a
turbine to generate additional electricity. In combined cycle operation,
electrical efficiencies in excess of 60% (HHV) have been suggested for
mature Molten
Carbonate Fuel Cell systems. The
Molten
Carbonate Fuel Cell operates at between 1110°F (600°C) and 1200°F
(650°C) which is necessary to achieve sufficient conductivity of the
electrolyte. To maintain this operating temperature, a higher volume of
air is passed through the cathode for cooling purposes. As
mentioned above, the high operating temperature of the Molten
Carbonate Fuel Cell offers the possibility that it could operate directly on
gaseous hydrocarbon fuels such as natural gas. The natural gas would be
reformed to produce hydrogen within the fuel cell itself. The
need for CO2 in the oxidant stream requires that CO2 from the spent
anode gas be collected and mixed with the incoming air stream. Before
this can be done, any residual hydrogen in the spent fuel stream must be
burned. Future systems may incorporate membrane separators to remove the
hydrogen for recirculation back to the fuel stream. At
cell operating temperatures of 1200°F (650°C) noble metal catalysts
are not required. The anode is a highly porous sintered nickel powder,
alloyed with chromium to prevent agglomeration and creep at operating
temperatures. The cathode is a porous nickel oxide material doped with
lithium. Significant technology has been developed to provide electrode
structures which position the electrolyte with respect to the electrodes
and maintain that position while allowing for some electrolyte boil-off
during operation. The electrolyte boil-off has an insignificant impact
on cell stack life. A more significant factor of life expectancy has to
do with corrosion of the cathode. The
Molten
Carbonate Fuel Cell
operating temperature is about 1200°F (650°C). At this temperature the
salt mixture is liquid and is a good conductor. The cell performance is
sensitive to operating temperature. A change in cell temperature from
1200°F (650°C) to 1110°F (600°C) results in a drop in cell voltage
of almost 15%. The reduction in cell voltage is due to increased ionic
and electrical resistance and a reduction in electrode kinetics. Improved efficiency is another reason Molten Carbonate Fuel Cells offer significant cost reductions over Phosphoric Acid Fuel Cells (PAFCs). Molten Carbonate Fuel Cells can reach efficiencies approaching 60 percent, considerably higher than the 37-42 percent efficiencies of a phosphoric acid fuel cell plant. When the waste heat is captured and used, overall fuel efficiencies can be as high as 85 percent. Unlike alkaline, phosphoric acid, and polymer electrolyte membrane fuel cells, Molten Carbonate Fuel Cells don't require an external reformer to convert more energy-dense fuels to hydrogen. Due to the high temperatures at which Molten Carbonate Fuel Cells operate, these fuels are converted to hydrogen within the fuel cell itself by a process called internal reforming, which also reduces cost. Molten Carbonate Fuel Cells are not prone to carbon monoxide or carbon dioxide "poisoning" —they can even use carbon oxides as fuel—making them more attractive for fueling with gases made from coal. Because they are more resistant to impurities than other fuel cell types, scientists believe that they could even be capable of internal reforming of coal, assuming they can be made resistant to impurities such as sulfur and particulates that result from converting coal, a dirtier fossil fuel source than many others, into hydrogen. The primary disadvantage of current Molten Carbonate Fuel Cell technology is durability. The high temperatures at which these cells operate and the corrosive electrolyte used accelerate component breakdown and corrosion, decreasing cell life. Scientists are currently exploring corrosion-resistant materials for components as well as fuel cell designs that increase cell life without decreasing performance.
The Phosphoric Acid Fuel Cell (PAFC) is considered the "first generation" of modern fuel cells. It is one of the most mature cell types and the first to be used commercially, with over 200 units currently in use. This type of fuel cell is typically used for stationary power generation, but some phosphoric acid fuel cells have been used to power large vehicles such as city buses.
Alkaline Fuel Cells' high performance is due to the rate at which chemical reactions take place in the cell. They have also demonstrated efficiencies near 60 percent in space applications. The
disadvantage of this fuel cell type is that it is easily poisoned by
carbon dioxide. Cost is less of a factor for remote locations such as space or under the sea. However, to effectively compete in most mainstream commercial markets, these fuel cells will have to become more cost-effective. Alkaline Fuel Cells have been shown to maintain sufficiently stable operation for more than 8,000 operating hours. To be economically viable in large-scale utility applications, these fuel cells need to reach operating times exceeding 40,000 hours, something that has not yet been achieved due to material durability issues. This is possibly the most significant obstacle in commercializing this fuel cell technology. Most fuel cells are powered by hydrogen, which can be fed to the fuel cell system directly or can be generated within the fuel cell system by reforming hydrogen-rich fuels such as methanol, ethanol, and hydrocarbon fuels. Direct Methanol Fuel Cells (DMFCs), however, are powered by pure methanol, which is mixed with steam and fed directly to the fuel cell anode. Direct Methanol Fuel Cells do not have many of the fuel storage problems typical of some fuel cells since methanol has a higher energy density than hydrogen—though less than gasoline or diesel fuel. Methanol is also easier to transport and supply to the public using our current infrastructure since it is a liquid, like gasoline. Direct Methanol Fuel Cell technology is relatively new compared to that of fuel cells powered by pure hydrogen, and Direct Methanol Fuel Cell research and development are roughly 3-4 years behind that for other fuel cell types. Proton Exchange Membrane (PEM) Fuel CellsProton
Exchange Membrane Fuel Cells - sometime called a Proton Exchange Membrane Fuel Cells operate at relatively low temperatures, around 80°C (176°F). Low temperature operation allows them to start quickly (less warm-up time) and results in less wear on system components, resulting in better durability. However, it requires that a noble-metal catalyst (typically platinum) be used to separate the hydrogen's electrons and protons, adding to system cost. The platinum catalyst is also extremely sensitive to CO poisoning, making it necessary to employ an additional reactor to reduce CO in the fuel gas if the hydrogen is derived from an alcohol or hydrocarbon fuel. This also adds cost. Developers are currently exploring platinum/ruthenium catalysts that are more resistant to CO. Proton Exchange Membrane Fuel Cells are used primarily for transportation applications and some stationary applications. Due to their fast startup time, low sensitivity to orientation, and favorable power-to-weight ratio, Proton Exchange Membrane Fuel Cells are particularly suitable for use in passenger vehicles, such as cars and buses. A significant barrier to using these fuel cells in vehicles is hydrogen storage. Most fuel cell vehicles (FCVs) powered by pure hydrogen must store the hydrogen onboard as a compressed gas in pressurized tanks. Due to the low energy density of hydrogen, it is difficult to store enough hydrogen onboard to allow vehicles to travel the same distance as gasoline-powered vehicles before refueling, typically 300-400 miles. Higher-density liquid fuels such as methanol, ethanol, natural gas, liquefied petroleum gas, and gasoline can be used for fuel, but the vehicles must have an onboard fuel processor to reform the methanol to hydrogen. This increases costs and maintenance requirements. The reformer also releases carbon dioxide (a greenhouse gas), though less than that emitted from current gasoline-powered engines.
Solid Oxide Fuel Cells operate at very high temperatures—around 1,000°C (1,830°F). High temperature operation removes the need for precious-metal catalyst, thereby reducing cost. It also allows Solid Oxide Fuel Cells to reform fuels internally, which enables the use of a variety of fuels and reduces the cost associated with adding a reformer to the system. Solid Oxide Fuel Cells are also the most sulfur-resistant fuel cell type; they can tolerate several orders of magnitude more sulfur than other cell types. In addition, they are not poisoned by carbon monoxide (CO), which can even be used as fuel. This allows Solid Oxide Fuel Cells to use gases made from coal. High-temperature operation has disadvantages. It results in a slow startup and requires significant thermal shielding to retain heat and protect personnel, which may be acceptable for utility applications but not for transportation and small portable applications. The high operating temperatures also place stringent durability requirements on materials. The development of low-cost materials with high durability at cell operating temperatures is the key technical challenge facing this technology. Scientists are currently exploring the potential for developing lower-temperature Solid Oxide Fuel Cells operating at or below 800°C that have fewer durability problems and cost less. Lower-temperature Solid Oxide Fuel Cells produce less electrical power, however, and stack materials that will function in this lower temperature range have not been identified. What
are Regenerative Fuel Cells? Regenerative Fuel Cells produce electricity from hydrogen and oxygen and generate heat and water as byproducts, just like other fuel cells. However, Regenerative Fuel Cells can also use electricity from solar power or some other source to divide the excess water into oxygen and hydrogen fuel—this process is called "electrolysis." This is a comparatively young fuel cell technology being developed by NASA and others. For more information: call Monty Goodell at: (832) 758 - 0027 * Some of the above information from the Department
of Energy website with permission. |
||||
|
|
||||
|
||||
|
Cogeneration Technologies |
||||
|
|
||||
Polymer
Electrolyte Membrane Fuel Cell — deliver high power density and offer the
advantages of low weight and volume, compared to other fuel cells. 