Since 2000 Atrex Energy has spent over $100 million on the research and development of a commercially viable Remote Power Generator utilizing Solid Oxide Fuel Cells (SOFC). Atrex Energy has made substantial progress in improving the technology over this timeframe.

Atrex Energy has:

  • Increased the output per fuel cell tube 120-fold
  • Developed SOFC designs with peak output over 10 kW; the first working SOFC generated a mere 20 watts of power
  • Tripled power density
  • Developed 18 patented innovations

Why Atrex Energy uses SOFC technology:

  • Low cost, stable ceramics used as its electrolyte layer
  • Use of ceramics and high temperatures eliminate need for expensive metal catalysts like platinum which are used in PEM fuel cells
  • It doesn't require the use high-purity hydrogen like other fuel cells require
  • High temperatures (600°C to 800°C) used in the Atrex Energy design allows conventional hydrocarbon fuels such as Natural Gas, Propane and LPG to be used directly without requiring an external reforming process which is costly, consumes space and is ultimately inefficient
  • No need to transport or store hydrogen, avoiding another layer of complexity

The fuel flexibility and the ability to use conventional fuels is a huge advantage for the Atrex Energy design. And the trillions of dollars expected to be needed to convert to a “Hydrogen Economy” with special pipes, tanks and pumps would be completely unnecessary. 

Two Types of Solid Oxide Fuel Cells

Planar SOFCs – very thin sheets of material form the layers
Tubular SOFCs – the layers are added to a cylindrical base

Atrex Energy utilizes a tubular SOFC design for its electrochemical process that produces DC electricity (see image below). 

How Atrex Energy's tubular SOFCs are made:

  • Formed by hydraulically pressing ceramic anode material into tubes and coating the tubes with an electrolyte layer and then a cathode layer. 
  • The Atrex Energy tubular SOFC is designed with the anode on the inside of each tube and the cathode on the outside. The fuel is injected inside the tube while air is on the outside resulting in an inherently safe configuration.  
  • Separating the anode from the cathode is an electrolyte comprised of zirconium oxide that allows only oxygen ions to pass through, carrying electrons from the cathode to the anode. This design provides a very strong structure and makes it relatively easy to seal, preventing the air and fuel from mixing. Having good seals is a big problem for the planar type type of SOFC. The plates in a planar design are thin, fragile and break if held too tightly by the seals as the fuel cell starts and stops.   

Just like corrugated cardboard is much stronger than the sheets of paper from which it is made, ceramic tubes are much stronger than ceramic plates. And the stronger ceramics used in Atrex Energy's tubular SOFC provide more resistance to thermal gradients caused by load changes, making them easier to cycle up and down as power requirements vary.

How does the Atrex Energy SOFC generate electricity?

  • In essence, the system works as long as oxygen from the air is attracted to some kind of fuel inside the tube. As the oxygen passes through the layers of the tube it is ionized and picks up two electrons per oxygen atom. 
  • Only these oxygen ions can pass through the inside of the tube.
  • When the oxygen ions react with the fuel, they release their electrons to the inside layer.
  • The outside of the tube becomes depleted of electrons and develops a positive charge.
  • The inside layer has a surplus of electrons and becomes negatively charged.
  • The result is just like a battery, with a positive terminal and negative terminal.
  • Simultaneously, on the inside of the tube raw fuel is broken down into hydrogen ions and carbon monoxide ions which attract the oxygen.
  • Simple fuels are broken down this way but more complicated fuels like gasoline and diesel require an added pre-processor to break down these fuels into smaller fragments the fuel cell can handle.

This Atrex Energy SOFC power generation process is analogous to a battery. The difference being that a battery's reactants have a finite life. The battery has to be replaced or recharged. A solid oxide fuel cell will run indefinitely as long as fuel and air are supplied to the tubes.

Atrex Energy assembles the tubes into a bundle or stack. This creates a fuel cell system that can currently handle loads from 100 watts up to 4.5kW. The net result is a highly efficient power generator that produces clean electricity more efficiently than other power generation technologies. Depending on the model, Atrex Energy's Remote Power Generator can achieve as much as 35% fuel efficiency. Future models are being designed with fuel efficiencies over 55%.

Emissions

The only by-products of the Atrex Energy SOFC design are water vapor, heat and low levels of carbon dioxide. Because operation is below the high temperature of internal combustion engines or turbines, fuel cells have nearly undetectable levels of nitrogen oxide (NOx). The desulfurizing fuel filters along with the high efficiency of Atrex Energy's fuel cell reduces the sulfur oxide (SOx) emissions to negligible levels. Efficiency is further enhanced when the heat is recovered for heating, hot water and processing purposes. 

Reforming

Many fuel cell designs require a separate reforming process to reform the fuel in order to extract the hydrogen required by the fuel cell generation process. This requires an external reformer which adds bulk, increases costs and requires regular maintenance. With the Atrex Energy SOFC design, reforming of the fuel takes place inside the tubes using commercially available fuels with hydrogen-rich content, such as natural gas and propane. By combining a small amount of air with the fuel inside the tubes, along with the inherent temperature of the Atrex Energy SOFC process, the fuel is automatically reformed to produce the needed hydrogen as well as carbon. This eliminates the need for extra reforming equipment, saving users CAPEX, OPEX and floor space.  More complex fuels require a pre-processor to create smaller fragments that can be handled inside the tubes.      

Atrex Energy's fuel flexibility and cost

A PEM fuel cell requires high-purity hydrogen. To get high purity hydrogen requires the extraction and purification of hydrogen from other hydrocarbon fuels such as Natural Gas. This requires extra equipment and special distribution methods adding significant cost and inefficiency. With Atrex Energy's SOFC design, commercial grade Natural Gas or Propane is used and the fuel cell will do the reforming internally. The fuel costs less, is readily available and is easily transportable. That adds up to big savings.

Atrex Energy SOFC's tubular shape versus planar

Another key design feature of the Atrex Energy SOFC design is the actual tubular shape of our fuel cell. The patented tubular design eliminates one of the biggest issues facing fuel cell technology – catastrophic damage due to temperature gradients. Temperature gradients occur during the normal thermal cycling that takes place during start-up, shut down and load changes. This cycling, over the lifetime of the unit, introduces stresses that could eventually manifest into cracks and ultimately failure.  

The small radius geometry of Atrex Energy's tubes, their inherent strength, the strong seal at one end and the operation under low pressure combine to minimize temperature gradients. This allows the tubes to easily tolerate thermal cycling. In addition, Atrex Energy's tubular design is much more tolerant to the stresses from internal reforming. So the need for costly external reformers common with planar fuel cell systems is eliminated. 

In fuel cells using planar ceramic plates there is an inherent weakness in the plates. They are fragile and hard to seal. Once assembled in stacks they require air and fuel to be supplied under high pressure. As a result, the plates can be prone to breaking under thermal stress.  Internal reforming of fuel is also destructive to planar or membrane fuel cells due to the temperature gradients resulting from the reforming process. This makes external reforming a necessity even for simple fuels, adding cost and complexity to the operation. It is also less efficient at reforming the fuel than the internal method used in Atrex Energy's SOFC design.

Tubular Fuel Cell design

Planar Fuel cell design

Start-up and cycling

Atrex Energy's tubular fuel cell can be started very quickly – 30 to 60 minutes. Other fuel cells, such as molten carbonate types can require 8 to 24 hours to be fully operational. Also, Atrex Energy's SOFC design can sustain multiple starts and stops over the years.

Electrolyte

The operating principle of solid oxide fuel cell technology is based on the use of electro-ceramics. These are advanced materials that exhibit unique electrical properties. The ceramic material zirconia allows ions to be conducted quickly but is a poor conductor of electrons. The electrolyte layer separates the anode and cathode and promotes ion and charge transfer. At the same time it insulates the anode and the cathode. This zirconia material is also used to improve performance and reliability. Zirconia is more rugged than traditional molten salts or polymer membranes which can be severely impacted by temperature fluctuations caused by cycling or load changes. Atrex Energy's electrolyte has a similar construction to oxygen sensors in automobiles that have performed reliably for decades. It's also relatively inexpensive.

Solid state design

The Atrex Energy design is a solid state design with only three moving parts. There is one fan to move the ambient air within the enclosure and two blowers to move air into the anode and around the cathode.  

Scalable Design

The heart of the Atrex Energy SOFC is the Fuel Cell Bundle. This component is a consumable item similar to the ink cartridge in an ink jet printer. Atrex Energy's design allows Bundle replacement to be a simple operation with minimal time required. An innovative part of this design is the scalability feature. The 1000 watt power generator can be converted to a 1500 watt power generator simply by changing out the Bundle. This gives users the flexibility to have their Atrex Energy Remote Power Generator output increased as their power needs grow.  In addition, larger units can be made using more tubes or longer tubes, providing an easy path to scale-up.    

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