How a High-Temperature Fuel Cell System Starts, Stops, and Recycles Fuel
This patent describes a fuel cell system that uses a smaller, secondary fuel cell to power itself during startup and shutdown, and to recycle hydrogen from its exhaust during normal operation.
Original patent title: “Method for high temperature fuel cell system start up and shutdown”
This patent describes a fuel cell system that uses a smaller, secondary fuel cell to power itself during startup and shutdown, and to recycle hydrogen from its exhaust during normal operation. Granted to Bloom Energy in 2010 with 16 claims and 26 forward citations, and it is expected to expire in 2028.
Coverage
What does this patent actually cover?
The patent outlines a method for operating a fuel cell system, specifically focusing on its start-up and shut-down phases, and how it handles fuel during normal operation. During normal, "steady state" operation, a main "fuel cell stack" (like a Solid Oxide Fuel Cell or Molten Carbonate Fuel Cell, per claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more → 7 and 13) converts fuel into electricity. The exhaust from this main stack then goes to a "PEM stack" (a Proton Exchange Membrane fuel cell/electrolyzer). This PEM stack operates in "electrolysis mode" (claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 4) to separate hydrogen from the exhaust and feeds that hydrogen back into the main fuel cell stack's fuel supply, making the system more efficient. When starting up or shutting down, the PEM stack switches roles. It receives its own fuel and air (claims 1 and 9) and generates power to run "auxiliary components" (claim 1) of the system, such as pumps or heaters, ensuring a smooth and controlled transition.
The gap
What does this patent NOT cover?
- Fuel cell systems that do not include a separate PEM stack for both power generation and hydrogen recycling.
- Systems where the PEM stack does not provide power to auxiliary components during start-up or shut-down.
- Systems where the PEM stack does not operate in electrolysis mode to separate hydrogen from the main fuel cell stack's exhaust.
- Methods that do not involve recycling separated hydrogen from the PEM stack back into the main fuel cell stack's fuel inlet stream.
- Fuel cell systems that do not involve a 'fuel cell stack' (specifically SOFC or MCFC in some claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →) and a 'PEM stack' working together in these defined roles.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The cleverness lies in using a single PEM stack for two distinct, critical functions: acting as a small fuel cell to provide power for the system's own start-up and shut-down needs, and then switching to an electrolyzer during normal operation to recycle hydrogen from the exhaust, boosting overall efficiency.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Bloom Energy Servers
Stationary fuel cell power plants
Combined heat and power (CHP) systems using SOFCs
Why it matters
The bigger picture
High-temperature fuel cells, such as Solid Oxide Fuel Cells (SOFCs) and Molten Carbonate Fuel Cells (MCFCs), are very efficient but require careful control during start-up and shut-down to prevent damage. This patent provides a way to manage these critical phases reliably and efficiently. By using a PEM stack to power auxiliary systems and recycle hydrogen, it makes these complex fuel cell systems more robust and self-sufficient, reducing operational costs and improving their lifespan.
Filed
June 3, 2008
Granted
December 7, 2010
Market context
Who's building on this
Companies in this space
Bloom Energy, the assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, continues to develop and deploy solid oxide fuel cell systems for distributed power generation. Other companies in the high-temperature fuel cell space, such as Ceres Power and Doosan Fuel Cell, also work on efficient operational strategies for their systems, though their specific implementations may differ.
Market impact
This patent contributed to the development of more reliable and efficient high-temperature fuel cell systems. By providing a method for controlled start-up and shut-down, and for internal hydrogen recycling, it helped make these systems more commercially viable for continuous operation, particularly in stationary power generation. This improved operational flexibility and reduced the need for external hydrogen supply, making fuel cells a more attractive option for distributed energy.
Claim 1 — Plain English
What this patent covers
The patent outlines a method for operating a fuel cell system, specifically focusing on its start-up and shut-down phases, and how it handles fuel during normal operation. During normal, "steady state" operation, a main "fuel cell stack" (like a Solid Oxide Fuel Cell or Molten Carbonate Fuel Cell, per claims 7 and 13) converts fuel into electricity. The exhaust from this main stack then goes to a "PEM stack" (a Proton Exchange Membrane fuel cell/electrolyzer). This PEM stack operates in "electrolysis mode" (claim 4) to separate hydrogen from the exhaust and feeds that hydrogen back into the main fuel cell stack's fuel supply, making the system more efficient. When starting up or shutting down, the PEM stack switches roles. It receives its own fuel and air (claims 1 and 9) and generates power to run "auxiliary components" (claim 1) of the system, such as pumps or heaters, ensuring a smooth and controlled transition.
The clever bit
The cleverness lies in using a single PEM stack for two distinct, critical functions: acting as a small fuel cell to provide power for the system's own start-up and shut-down needs, and then switching to an electrolyzer during normal operation to recycle hydrogen from the exhaust, boosting overall efficiency.
What it does not cover
- Fuel cell systems that do not include a separate PEM stack for both power generation and hydrogen recycling.
- Systems where the PEM stack does not provide power to auxiliary components during start-up or shut-down.
- Systems where the PEM stack does not operate in electrolysis mode to separate hydrogen from the main fuel cell stack's exhaust.
- Methods that do not involve recycling separated hydrogen from the PEM stack back into the main fuel cell stack's fuel inlet stream.
- Fuel cell systems that do not involve a 'fuel cell stack' (specifically SOFC or MCFC in some claims) and a 'PEM stack' working together in these defined roles.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
PatentBrief Score
Impact Score
Moderate
Citation count
29/40
Moderately cited
Claim breadth
11/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
5/20
Granted 10–20 years ago
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$82K – $262K
Midpoint $164K · 1.7 yr remaining · industry ×1.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Patent Claims
0 independent claims · 1 dependent
Claims are the legal boundaries of the patent. An independent claim stands alone. A dependent claim adds limitations to its parent, narrowing — but not broadening — the scope.
The original legal language
Original claims
16 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Ballantine, A., & McElroy, J. (2010). How a High-Temperature Fuel Cell System Starts, Stops, and Recycles Fuel (U.S. Patent No. 7,846,599). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/7846599/method-for-high-temperature-fuel-cell-system-start-up-and-shutdown
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How a High-Temperature Fuel Cell System Starts, Stops, and Recycles Fuel cover?
This patent describes a fuel cell system that uses a smaller, secondary fuel cell to power itself during startup and shutdown, and to recycle hydrogen from its exhaust during normal operation.
Who owns patent US 7846599?
Bloom Energy owns this patent, granted in 2010.
When does this patent expire?
This patent is expected to expire on June 3, 2028, when the invention enters the public domain.
What is patent US 7846599 cited by?
This patent has been cited by 26 later patents that build on its ideas.
What problem does this patent solve?
High-temperature fuel cells, such as Solid Oxide Fuel Cells (SOFCs) and Molten Carbonate Fuel Cells (MCFCs), are very efficient but require careful control during start-up and shut-down to prevent damage. This patent provides a way to manage these critical phases reliably and efficiently. By using a PEM stack to power auxiliary systems and recycle hydrogen, it makes these complex fuel cell systems more robust and self-sufficient, reducing operational costs and improving their lifespan.
What does this patent NOT cover?
Fuel cell systems that do not include a separate PEM stack for both power generation and hydrogen recycling.
Same assignee
More from Bloom Energy
Patent monitoring