Archive for October, 2010
Fuel cells are being used to power buses, boats, trains, planes, and forklifts to name a few applications, and most (if not all) automakers are working to commercialize cars. Additionally, there are fuel cell-powered vending machines and vacuum cleaners, and cell phones and laptops are poised to hit the market.As far as stationary fuel cell systems are concerned, the three most popular applications are to power generation systems in hospitals, office buildings, hotels, schools, and utility districts; use with computers and telecommunications to identify more reliable power than currently on the grid; and landfills/wastewater treatment plants to reduce emissions and generate power from the methane gas they produce.A recent highlight for stationary fuel cell use includes Adobe’s installation to power their San Jose, California headquarters and New Haven Connecticut’s installation in City Hall.
October 21st, 2010
There are five primary types of fuel cells based on their unique electrolyte use, and each has specific characteristics that make it better in certain applications over others.
- Polymer Electrolyte Fuel Cell (PEFC) or Proton Exchange Membrane Fuel Cell (PEMFC) The electrolyte in this type of fuel cell is an ion exchange membrane made of some type of polymer that is a good conductor of protons. This type of fuel cell runs at low temperatures with electrical efficiencies of about 45, and is the primary candidate for automotive, small stationary, and portable power applications. PEMFCs require very pure hydrogen as the fuel.
- Phosphoric Acid Fuel Cell (PAFC) The electrolyte in this type of fuel cell is phosphoric acid, concentrated to 100. PAFCs have a high operating temperature and achieve an electrical efficiency of about 37-42. Buses and stationary applications currently use PAFCs.
- Molten Carbonate Fuel Cell (MCFC) The electrolyte in this type of fuel cell is usually a combination of alkali carbonates, retained in a ceramic matrix. The MCFC operates at very high temperatures which enables the end user to utilize both the electricity and the thermal energy generated by the fuel cell, resulting in electrical efficiencies of more than 70 percent. MCFCs are well-suited to large-scale stationary applications, and are currently being demonstrated for powering buildings.
- Solid Oxide Fuel Cell (SOFC) The electrolyte in the SOFC is a solid, nonporous metal oxide. At temperatures over 650 degrees Celsius, the SOFC can utilize a hydrocarbon fuel directly, without reforming, similar to the MCFC. Also similar to the MCFC, the SOFC generates both electricity and usable thermal energy. High-temperature SOFCs are being demonstrated for stationary power applications, while low-temperature SOFCs are also being looked at for automotive applications.
- Alkaline Fuel Cell (AFC) This was one of the first modern fuel cells to be developed and was used to provide on-board electric power for the Apollo space vehicle. The electrolyte in this fuel cell is Alkaline (KOH). AFCs require pure hydrogen and pure oxygen as the reactants. The operating temperature for this type of fuel cell is around 200 degrees Celsius.
October 19th, 2010
The benefits of fuel cells are far-reaching. Following is an overview of some of the most noteworthy.
- Fuel cells are 2-3 times as efficient as internal combustion engines for vehicle propulsions; and when used in co-generation applications fuel cell power plants can achieve energy efficiencies over 80 percent.
- Fuel cell power plants are so clean that some cities have exempted the technology from the requirements to obtain air permits.
- A program to install eight fuel cells at wastewater treatment plants around New York City expects to eliminate almost 170 tons of regulated emissions, more than 9,000 tons of carbon dioxide, and reduce fuel oil consumption by 3,000 barrels a year.
- Fuel cells utilize domestically produced fuels no more reliance on imports.
- Since fuel cells have fewer moving parts they are more quiet and require less maintenance.
- Worrying about losing power during electrical storms is becoming a thing of the past and this means costs associated with power outages will virtually be eliminated.
October 17th, 2010
In principle, a fuel cell operates like a battery. But 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.Structurally, a fuel cell consists of two electrodes sandwiched around an electrolyte. Oxygen passes over one electrode and hydrogen passes over the other resulting in electricity, water and heat.Hydrogen fuel is fed into the anode of the fuel cell. Air (oxygen) enters the fuel cell through a 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 and the electron creates 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.A fuel cell system which includes a fuel reformer can utilize the hydrogen from any hydrocarbon fuel — from natural gas to methanol, and even gasoline. Since the fuel cell relies on chemistry and notcombustion, emissions from this type of a system are still much smaller than emissions from the cleanest fuel combustion processes.
October 13th, 2010