Power
Atrex Energy Inc.
T EC HNIC AL WHI T E PAPER: S OL ID OXIDE FUEL CEL L
P OW ER G EN ER AT O R S O P ER AT I O N & M A I N T EN A N C E
OVERVIEW
This Technical White Paper discusses annual O&M that is required for a Solid Oxide Fuel Cell. It is not intended to replace
Atrex Energy O&M Manuals that detail out the exact procedures, but rather to simply provide the reader with a good
sense of what is required for proper Fuel Cell O&M and how much it will cost.
Also discussed in the TWP is possible corrective maintenance actions and Atrex Energy’s philosophy for such.
This write-up applies equally to each of the 4 models SOFCs (250, 500, 1000 and 1500-watt) that Atrex Energy offers. The
O&M is exactly the same. The only difference is the cost of the fuel cell bundles (discussed below).
Atrex Energy normally recommends Preventive Maintenance (“PM”) take place in the 12-15 month window.
There are 4 basic PM steps as follows:
1. Replace Fuel Cell Bundle (picture right)
2. Inspect and Replace, if necessary,
• Desulfurizer Filters
• Air Filters
• Igniter Element
• Moving parts (fans)
3. Verify Electrical and Mechanical Connections, inspect
for corrosion
4. Data log all O&M Actions Photo shows bundle for the
RP-500 SOFC (20 tubes)
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Power
Atrex Energy Inc.
T EC HNIC AL WHI T E PAPER: S OL ID OXIDE FUEL CEL L
P OW ER G EN ER AT O R S O P ER AT I O N & M A I N T EN A N C E
OVERVIEW
The Fuel Cell Stack Bundle is what actually produces the electricity.
Each SOFC contains a different # of fuel cell tubes:
Model 250-Watt 500-Watt 1000-Watt 1500-Watt # of Fuel Cell Tubes
10 tubes
20 tubes
40 tubes
48 tubes
The fuel cell stack delivers steady power output for most of its life but starts to degrade at some point and subsequently
will no longer be able to generate the unit’s rated power. The normal expected life of a SOFC bundle is approximately
12,000 hours of operation or basically every 1 ½ years.
Atrex Energy recommends this bundle (referred to as a “RB” Replacement Bundle) be changed out in a Preventive
Maintenance action sometime in the 12-15 month time period.
The RB is a ‘line replaceable unit’. Replacement
procedures, outlined in the unit’s O&M Manual are
relatively straightforward and should take 1 trained
technician approximately 2-3 hours start to finish.
Preventive Maintenance (“PM”)
Corrective Maintenance (“CM”)?
or
While Atrex Energy recommends the FC Bundle be
replaced as a preventive maintenance action, some
customers are willing to wait until the fuel cell actually
fails (stops entirely or stops producing a sufficient
amount of power) and then perform RB replacement
as a ‘corrective maintenance’ action.
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Power
Atrex Energy Inc.
T EC HNIC AL WHI T E PAPER: S OL ID OXIDE FUEL CEL L
P OW ER G EN ER AT O R S O P ER AT I O N & M A I N T EN A N C E
OVERVIEW
Handling bundle replacement as a CM action does typically result in getting longer life out of the RB and, consequently,
over a period of years could end up with fewer RB replacements.
A good example for this type of approach is when SOFCs are employed to power ‘noncritical loads’ such as many industry
folks consider cathodic protection loads to be.
What is Atrex Energy’s opinion on this? We defer to each individual customer’s O&M philosophy but stand by our
recommendation that RBs be handled as a PM action in the 12-15 month range.
Could RB fail before 12-15 months?
Possibly. As SOFCs are designed to be continuous-run pieces of power generation equipment, they are not designed for
applications with a large number of thermal cycles (“TCs”). If the SOFC experiences an excessive number of TCs (loss of fuel
causing the SOFC to cool down and then ‘heat back up’ when fuel is restored), it could have an adverse effect on its life.
While SOFCs have been designed to handle a limited # of TCs, the more there are, the more stress on the RB and, hence,
the more rapid degradation.
How much do RBs cost?
A good budgetary number for RB replacement is 15% of initial capital cost.
What is Atrex Energy doing to lower the RB costs?
Atrex Energy fully understands that its customers would like to see RB prices reduced. We agree and have implemented a
simple and straightforward strategy to do exactly that.
1. Atrex
Energy’s
engineers
are working to extend the
life of the fuel cell bundle
(i.e.
recommended
bundle
replacement interval extends
from 12-18 months to 2 years,
and then to 3 years etc.)
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Power
Atrex Energy Inc.
T EC HNIC AL WHI T E PAPER: S OL ID OXIDE FUEL CEL L
P OW ER G EN ER AT O R S O P ER AT I O N & M A I N T EN A N C E
OVERVIEW
2. The actual cost of the bundle is reduced and Atrex Energy is able to charge a lower price to its customers.
As the above graph points out, Atrex Energy has made tremendous strides with both over the past few years and expects
that trend to continue.
The typical life of a bundle is about 18 months to 24 months and the cost has reached a point where RB pricing is about 15%
of initial capital cost. Worthy of mention is that Atrex Energy was able to reduce its 2014 price for RBs by approximately 7%
below its FY2013 price. This price reduction is a direct result of the efforts noted above.
It is also noteworthy to mention that while a typical bundle life is about 18-24 months, Atrex Energy has several operationally
deployed SOFCs whose bundles have exceeded 36 months.
Desulfurizer Filter Replacement
The other large PM action is replacement of the desulfurizer filters which come
inside the two large metallic canisters shown in the photo at right.
Notice there are two filters as dual redundancy was designed into the SOFC.
These filters have been designed to scrub out 60 ppmv of sulfuric materials at full
fuel flow rates for one year.
How often to replace these filters is truly a function of how sulfur-laden the gas is.
As of early 2014, with over 1,000,000 hours of actual in-field operations, many SOFCs
still have their original desulfurizers; others have had their desulfurizers changed out.
More often than not, gas from pipelines has had some level of conditioning and therefore, typically have lower levels of
sulfur (although that same gas has had some Mercaptan Sulfur injected to provide odor). Hence, desulfurizers for pipeline
applications typically will require less frequent replacement.
On the other hand, the amount of sulfur in wellhead gas can vary quite widely so it is difficult to make any general
statements.
How much do replacement desulfurizers cost?
Filter replacement, with the canisters being returned to Atrex Energy for factory reconditioning, cost a few hundred
dollars each.
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Power
Atrex Energy Inc.
T EC HNIC AL WHI T E PAPER: S OL ID OXIDE FUEL CEL L
P OW ER G EN ER AT O R S O P ER AT I O N & M A I N T EN A N C E
OVERVIEW
Air Filters and Igniter PM Actions
Besides the two big items discussed above, the SOFC has a few other minor items that require annual action:
• Air Filters
SOFCs each have two air filters, the main flat intake filter in the enclosure cover and a secondary round filter dedicated to
the anode process air.
Atrex Energy recommends each filter be replaced annually (caveat: bad quality air such as a windy, sandy location as might
be found in the desert, could require more frequent air filter replacement).
Each of these filters can be replaced while the SOFC continues to run. Replacement time is less than 10 minutes per filter.
No special tools are required.
• Igniter Element
For system start-up, each SOFC has an igniter. During annual O&M when the bundle is being replaced, it is good practice
to also replace this element. It takes about 15 minutes to accomplish.
Other PM Actions
Finally, as is good practice when performing any maintenance, Atrex Energy recommends two additional actions:
1. Do a good visual inspection of the entire fuel cell looking specifically for any loose electrical connections, fuel fitting
connections etc. Also look for any corrosion.
2. Record all O&M Actions.
Corrective Maintenance
Corrective Maintenance, of course, is like getting a flat tire. Something breaks and it needs to be replaced.
In a SOFC, besides the components discussed above, there are really only a handful of other components or sub-assemblies
that could require replacement at some point during the SOFC’s lifetime.
The photo on the next page pretty much shows all such items.
The System Battery Bank is a sealed, valve regulated lead acid (VRLA) battery that under normal operating conditions can
reasonably be expected to last for 5-6 years. Replacement is about as complicated as replacing the battery in one’s car;
15-20 minutes, no special tools required.
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Power
Atrex Energy Inc.
T EC HNIC AL WHI T E PAPER: S OL ID OXIDE FUEL CEL L
P OW ER G EN ER AT O R S O P ER AT I O N & M A I N T EN A N C E
OVERVIEW
Unlike the system battery which will degrade over time, the three other items shown would normally not be expected to
fail. That said, in the real world ‘stuff happens’ and parts break.
Both the Power and Control Electronics (“PACE”) Panel and the Gas Utility Module (“GUM”) are designed as ‘subassemblies’. In the event of a failure, rather than attempting to repair the sub-assembly in the field, the entire assembly
has been designed to be replaced on a Line Replaceable Module (“LRM”) basis. In other words, with disconnecting a
few electrical and mechanical connections, both the PACE and GUM assemblies can be easily removed and replaced.
Thereafter, the faulty assembly can be either repaired in the operator’s maintenance shop or, if need be, returned to Atrex
Energy for repair or replacement.
Same LRM philosophy applies to the Data Recorder. Note: As a ‘pre-planned product improvement’ the DR is due to be
replaced at some point this coming year. It will be replaced with a dedicated motherboard for data acquisition operating on
an industrial Linux system. This change, when implemented, will maintain (or actually improve) the same functionality while
making the design more robust and lowering cost.
One exception:
The only moving parts in a SOFC are 2 blowers and 1 fan. The two silver discs shown in the photo above as part of the GUM
are cover plates for the cathode and anode air blowers. These blowers are very robust and have exhibited problem-free
operations. In the unlikely event one fails, it can be replaced in situ.
Same is true for the fan on the inside of the SOFC’s enclosure housing. If that fan were to malfunction, it could be replaced
in situ.
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Power
Atrex Energy Inc.
T EC HNIC AL WHI T E PAPER: S OL ID OXIDE FUEL CEL L
P OW ER G EN ER AT O R S O P ER AT I O N & M A I N T EN A N C E
OVERVIEW
Atrex Energy Technical White Papers
Atrex Energy is a big believer in ‘speaking with data’ and has written a series of Technical White Papers (“TWPs”) that
present objective and quantifiable attributes of the various technologies at the heart of today’s commercially available off
grid power systems. By carefully examining the pros and cons of the different approaches the end user can make informed
decisions and select the most appropriate power system for their specific project application.
Please feel free to contact Atrex Energy and ask for what topics it has TWPs on.
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