The first residence to go completely off-grid was a home in Latham, New York. On June 17, 1998, this single-family dwelling became the first dwelling to be powered by a RFC (Residential Fuel Cell). Latham’s Plug Power, a limited liability corporation, developed this prototype RFC. At the same time another company, APC (American Power Corporation) was readying an RFC for market. The question is, then, is there an RFC in your future?
What is a fuel cell and how does it work
Many of you will probably recall seeing electrolysis demonstrated during one of your high school or college chemistry lab demonstrations. Using a Hoffman Apparatus water breaks down into its component elements, Oxygen and Hydrogen, when an electric current is passed through it. A fuel cell works by reversing this process. Hydrogen and oxygen are combined chemically to produce electricity, heat, and water.
There are several different types of fuel cells and each operates slightly differently but the principle of operation is the same. The “fuel” enters the cell at the cell’s Anode (The Anode is the cell’s positive electrode) where its Hydrogen atoms are stripped of its electrons. This is done through a chemical reaction that is expedited by a Catalyst. As you probably recall from your chemistry classes, a catalyst is anything that speeds up a chemical reaction without becoming part of the actual reaction. The freed electrons then pass through the external electrical circuit to power the load while the positive Hydrogen ions pass through a Proton Exchange Membrane to the cell’s Cathode, the cell’s Negative electrode. The electricity produced by a fuel cell is DC (Direct Current) so an inverter has to be used to convert it to AC (Alternating Current) which is the type of current required by most household electrical loads. At the Cathode, the positive ions combine with the returning electrons and with Oxygen taken from the atmosphere to produce water vapor, which is exhausted back into the environment. Heat is also produced as a fuel cell waste product. Since heat and water are the only waste products produced by a fuel cell fuel cells are a very Green energy source. Actually, the heat produced really isn’t a waste product because it can be harnessed to heat the home and the home’s water supply. So why aren’t we all using fuel cells to power our homes today? Fuel cell technology is still far too expensive for the average homeowner to buy.
Explaining how the fuel cell works is relatively simple and straight forward but building efficient fuel cells is anything but simple or inexpensive. The technology involved is complicated and very expensive to produce. The scientist and engineers working on fuel cells are faced with many decisions.
The first challenge faced by the designers is what type of electrolyte to use. As you may recall from you chemistry classes, an electrolyte is any solution or nonmetallic solid that will conduct an electric current. The most common electrolytes being used today in fuel cells are alkali solutions, molten carbonate solutions, phosphoric acid solutions, solid Proton Exchange Membranes, and solid oxides. The type of fuel required by the cell is determined by the cells electrolyte. In the beginning, all fuel cells were fueled by Hydrogen gas but today’s fuel cells can use a wide range of gases even natural gas. Each type of fuel cell has its own unique advantages and disadvantages.
The alkali fuel cell
The alkali fuel cell employs compressed hydrogen and oxygen. The electrolyte is a solution of KOH (Potassium Hydroxide) in water. This cell has an efficiency of 70-percent and was the cell used on the Apollo spacecraft to produce its electrical power and the drinking water that the crewmembers drank during the mission. These cells operate at a temperature of approximately 300 to 400 degrees Fahrenheit and have an output of from 300 Watts to 5 Kw (Kilowatts).
The MCFC (Molten Carbonate Fuel Cell)
The MCFC (Molten Carbonate Fuel Cell) is a very high temperature fuel cell operating at approximately 1,200 degrees Fahrenheit. They also have a very high output of around 2 Mw (2 Million Watts) operating within an efficiency range of
The PAFC (Phosphoric Acid Fuel Cell)
The PAFC (Phosphoric Acid Fuel Cell) operates at a temperature of 300 to 400 degrees Fahrenheit, as the Alkali cells but produces a much higher electrical output. The PAFC can produce from 200 Kw to 11 Mws operating at an efficiency of 40 to 80 percent.
The PEM (Proton Exchange Membrane) fuel cell
The PEM (Proton Exchange Membrane) fuel cell operates at a very low temperature of around 175 degrees Fahrenheit, which makes this the ideal cell to be used in homes and motor vehicles. Their use of a solid, flexible electrolyte eliminates the worry about leakage, which also makes them the ideal fuel cells to be used in cars, buses, trucks, airplanes, etc. Their efficiency, at 40 to 50 percent is low but their power output is relatively good with a range of 50 to 250 Kw. Their use of Platinum as a catalyst makes them one of the most expensive fuel cells to produce.
The SOFC (Solid Oxide Fuel Cell)
The SOFC (Solid Oxide Fuel Cell) like the PEM uses a solid electrolyte like the PEM but they operate at a very high temperature of around 1,800 degrees Fahrenheit. Their high operating temperature and large size limit their application although they have a high electrical output in the range of 100 Kw at a relatively good efficiency of 60 percent.
There may be a fuel cell, at least a small one, in your future yet. The cost of this technology is falling steadily just as the cost of computer technology and other solid-state technology. Back in the days when I built my first transistor radio a CK722 transistor cost $3.50, today you can by a CK722 transistor for less than a dollar. A small PEM cell would be the ideal power source for an electric car, truck, boat, etc. The PEM cell would also make an ideal backup power source for a home instead of the gasoline, diesel, or natural gas standby generators that we now use.
