[ additive manufacturing ] lives and greater efficiency . One example is the anode offgas recycle blower ( AORB ), an essential component of the ‘ balance of plant ’ – the machinery that supports the SOFC ’ s fuel stack .
During operation , each fuel cell only uses about 70 % of the gas it ’ s fed ; some 30 % passes right through the system along with water ( a product of the electrochemical reaction ). “ You don ’ t want to throw away the leftover gas or water , you want to send them back to the beginning of the process ,” says Cordova . “ And that ’ s where the AORB comes in ; it ’ s essentially a low-pressure compressor or fan that recycles the exhaust and returns it to the front of the fuel cell .”
“ SOFC balance-of-plant designers were thinking that this blower would be an off-theshelf unit ,” says Cordova ( a typical 250 kW SOFC plant would employ two of them ). “ But due to the process gases in the system , traditional blowers tend to corrode and degrade ; the hydrogen in the mixture attacks the alloys the blowers are made of and also damages the magnets and electrical components of the motors that power the blowers . Most blowers also contain lubricants , like oil , that degrade as well . So you end up with very low-reliability blowers – representing a significant portion of the balance-of-plant cost – and your SOFC plant needs an overhaul every two to four thousand hours .”
coatings , and decades of turbomachinery expertise were a good fit for this challenge ,” says Cordova .
Additive manufacturing offers answers
DOE funding provided the means for Mohawk to design and test AORB prototypes in a demonstrator SOFC power plant run by FuelCell Energy . Rigorous testing under realistic operating conditions measured durability and performance , with the latest versions demonstrating no significant degradation in parts or output and complete elimination of any performance or reliability issues .
Yet the cost of an AORB remained prohibitively high – in large part due to its high-speed centrifugal impeller , which operates continuously under extreme mechanical and thermal stress . For longest life , this part must be made from expensive , high-strength , nickel-based , corrosion-resistant superalloy materials like Inconel 718 or Haynes 282 that are difficult to machine or cast . In addition , achieving optimal aerodynamic efficiency in an impeller requires complex three-dimensional geometries that are
This statistic falls far short of the DOE ’ s goal of an operating lifetime of 40,000 hours for a typical SOFC – as well as an installation-cost reduction from an average of USD 12,000 / kWe ( kilowatt of electrical energy ) to USD 900 / kWe .
Time to rethink those blowers ! “ So we realized that Mohawk ’ s proprietary , oil-free , compliant foil bearing ( CFB ) technology , specialized
View of an oil-free anode offgas recycle blower ( AORB ) made by Mohawk Innovative Technology Inc .
Hydrogen Tech World | Issue 8 | February 2023 31