FUEL CELL TECHNOLOGY OVERVIEW
The great benefits of local (meaning located at the place of consumption) fuel cell design and installation are: the reduction of energy delivery cost (as there is significant loss to heat and electromagnetic radiation in long range electricity delivery,) availability, firm power (as power generation is local so hopefully not subjected to outages or overloads,) multi-fuel, bio-fuel compatibility (high temperature fuel cell designs can tolerate lower hydrogen densities such as those found in bio-fuels.)
Basic fuel cells design is comprised of two electrodes (dissimilar materials with opposite electrical charges) separated by an electrolyte (the transport medium for the electrically charged particles from one electrode to another.) Electricity is produced by introducing hydrogen containing gas and separating the electrons from the protons, thereby creating an electrical potential difference (voltage) between the electrodes within the cell.
Currently, the different types of fuel cells in development are:
Alkali, Phosphoric Acid (PAFC), Molten Carbonate (MCFC), Proton Exchange Membrane (PEM), and Solid Oxide Fuel Cells (SOFC). Alkali fuel cells operate at relatively low temperatures (150 to 200 degrees C,) require expensive platinum electrode catalysts and pure hydrogen fuel.
PAFC fuel cells operate at low temperatures (150 to 200 degrees C) can tolerate a broader range of fuels and require expensive platinum catalysts.
MCFCs operate at higher temperatures (650 degrees C) and require carbon dioxide injection.
PEMs have the lowest operating temperatures (80 degrees C) and require pure hydrogen.
SOFCs operate at high temperatures (approx. 1000 C,) can tolerate a broader range of fuels, and have a solid electrolyte as their name implies.
An excellent illustrated overview of basic fuel cell technology is available from the Smithsonian Institute’s website.
Bloom Energy
Bloom Energy of Silicon Valley California, a provider of large commercial electricity generation systems based upon SOFC technology has become a recent media sensation.
Because Bloom is using SOFC technology with high operating temperatures, their systems are less reliant on fuel purity and are advertised as capable of using either biogas or natural gas to generate electricity. Byproducts are heat, some H2O, and pure CO2.
Bloom also claims their system is reversible – capable of both energy generation and storage. Coupled with intermittent renewable resources like solar or wind, Bloom’s future systems will produce and store hydrogen to enable a 24 hour renewable solution and provide a distributed hydrogen fueling infrastructure for hydrogen powered vehicles.
Each Bloom Energy fuel cell is capable of producing about 25W, enough to power a light bulb. For more power, the cells are sandwiched, along with metal interconnect plates into a fuel cell “stack”. Bloom then bundles these “stacks” with a common fuel input into a system with the required power output. Several “stacks” about the size of a loaf of bread connected to a constant source of hydrogen laden gas should provide enough power for an average home. Blooms “Energy Server” provides 100kW of power, enough to meet the baseload needs of 100 average homes or a small office building.
Bloom claims their systems typically provide a 3-5 year payback on their initial capital investment.
A data sheet is available from their website.
Bloom Energy Company History:
Dr. KR Sridhar and his team at Arizona University were charged with creating a technology that could sustain life on Mars as part of the NASA Mars space program. They built a device capable of producing air and fuel from electricity, and/or electricity from air and fuel. In 2001, when their project ended, the team continued their research and started a private company named Ion America.
In 2002, John Doerr, and Kleiner Perkins became the first investors in the company. With financing in place, they moved near NASA Ames Research Center in Silicon Valley to further develop their technology. Bloom’s first field trial unit was a 5kW unit installed at the University of Tennessee, Chattanooga. Following two years of successful field trials in Tennessee, California, and Alaska, the first commercial (100kW) products were shipped to Google in July 2008.