How Fuel Cells Reuse Exhaust Hydrogen for High Efficiency
This patent describes a fuel cell system that captures and recycles over 95% of the unused hydrogen from its exhaust stream using a special pump, significantly boosting efficiency.
Original patent title: “Fuel cell system with greater than 95% fuel utilization”
This patent describes a fuel cell system that captures and recycles over 95% of the unused hydrogen from its exhaust stream using a special pump, significantly boosting efficiency. Granted to Bloom Energy in 2010 with 23 claims and 29 forward citations, and it is expected to expire in 2027.
Coverage
What does this patent actually cover?
This invention outlines a method for operating a fuel cell system with very high fuel utilization. First, a fuel inlet stream enters a fuel cell stack, which generates electricity and produces a hydrogen-containing fuel exhaust stream (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1). Instead of letting this hydrogen go to waste, a "cascaded electrochemical hydrogen pump" then separates at least 95% of the hydrogen from this exhaust (Claim 1). This recovered hydrogen is then fed back into the original fuel inlet stream (Claim 1), effectively reusing it. For example, a solid oxide fuel cell (SOFC) system that normally loses some hydrogen in its exhaust can now capture and re-inject nearly all of it, making the system much more efficient.
The gap
What does this patent NOT cover?
- Fuel cell systems that do not recirculate hydrogen from their exhaust stream back into the fuel inlet.
- Systems that separate less than 95% of the hydrogen contained in the fuel exhaust stream.
- Hydrogen separation methods that do not use a "cascaded electrochemical hydrogen pump."
- Fuel cell systems that do not include a fuel cell stack (e.g., just a hydrogen pump).
- Hydrogen pumps that are not specifically a "high temperature, low hydration ion exchange membrane cell stack" if those features are claimed (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 4).
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The noveltynoveltyThe requirement that an invention be different from anything publicly known before its priority date.Read more → lies in using a "cascaded electrochemical hydrogen pump" to achieve extremely high (over 95%) recovery of hydrogen from the fuel cell exhaust and then feeding it back into the system. This maximizes fuel efficiency in a way that was not commonly achieved before.
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
Industrial-scale solid oxide fuel cell (SOFC) systems
Fuel cell power plants for data centers
Distributed power generation units
Why it matters
The bigger picture
Fuel cells are an efficient way to generate electricity, but some fuel often goes unused. This patent addresses a key challenge by significantly improving "fuel utilization," meaning more of the input fuel is converted into electricity. This makes fuel cell systems more economical and environmentally friendly by reducing waste and potentially enabling carbon capture, as mentioned in ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 7, which describes sequestering carbon dioxide from the remaining exhaust.
Filed
March 30, 2007
Granted
November 16, 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 →, is a prominent player in solid oxide fuel cell technology, deploying systems for distributed power generation. Other companies developing advanced fuel cell systems, such as Ceres Power and Mitsubishi Power, are also focused on improving efficiency and fuel utilization in their products.
Market impact
This patent contributed to the development of highly efficient fuel cell systems, particularly solid oxide fuel cells, by enabling significantly higher fuel utilization. This increased efficiency makes fuel cells more competitive with traditional power generation methods, especially for industrial and commercial applications where operational costs are critical. It supports the broader trend towards cleaner energy solutions and reduced carbon emissions.
Claim 1 — Plain English
What this patent covers
This invention outlines a method for operating a fuel cell system with very high fuel utilization. First, a fuel inlet stream enters a fuel cell stack, which generates electricity and produces a hydrogen-containing fuel exhaust stream (Claim 1). Instead of letting this hydrogen go to waste, a "cascaded electrochemical hydrogen pump" then separates at least 95% of the hydrogen from this exhaust (Claim 1). This recovered hydrogen is then fed back into the original fuel inlet stream (Claim 1), effectively reusing it. For example, a solid oxide fuel cell (SOFC) system that normally loses some hydrogen in its exhaust can now capture and re-inject nearly all of it, making the system much more efficient.
The clever bit
The novelty lies in using a "cascaded electrochemical hydrogen pump" to achieve extremely high (over 95%) recovery of hydrogen from the fuel cell exhaust and then feeding it back into the system. This maximizes fuel efficiency in a way that was not commonly achieved before.
What it does not cover
- Fuel cell systems that do not recirculate hydrogen from their exhaust stream back into the fuel inlet.
- Systems that separate less than 95% of the hydrogen contained in the fuel exhaust stream.
- Hydrogen separation methods that do not use a "cascaded electrochemical hydrogen pump."
- Fuel cell systems that do not include a fuel cell stack (e.g., just a hydrogen pump).
- Hydrogen pumps that are not specifically a "high temperature, low hydration ion exchange membrane cell stack" if those features are claimed (Claim 4).
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
15/20
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
$31K – $98K
Midpoint $61K · expired or expiring · 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
23 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
McElroy, J. F., & Ballantine, A. W. (2010). How Fuel Cells Reuse Exhaust Hydrogen for High Efficiency (U.S. Patent No. 7,833,668). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/7833668/fuel-cell-system-with-greater-than-95-fuel-utilization
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 Fuel Cells Reuse Exhaust Hydrogen for High Efficiency cover?
This patent describes a fuel cell system that captures and recycles over 95% of the unused hydrogen from its exhaust stream using a special pump, significantly boosting efficiency.
Who owns patent US 7833668?
Bloom Energy owns this patent, granted in 2010.
When does this patent expire?
This patent is expected to expire on March 30, 2027, when the invention enters the public domain.
What is patent US 7833668 cited by?
This patent has been cited by 29 later patents that build on its ideas.
What problem does this patent solve?
Fuel cells are an efficient way to generate electricity, but some fuel often goes unused. This patent addresses a key challenge by significantly improving "fuel utilization," meaning more of the input fuel is converted into electricity. This makes fuel cell systems more economical and environmentally friendly by reducing waste and potentially enabling carbon capture, as mentioned in Claim 7, which describes sequestering carbon dioxide from the remaining exhaust.
What does this patent NOT cover?
Fuel cell systems that do not recirculate hydrogen from their exhaust stream back into the fuel inlet.
Patent monitoring