Solid desiccant patents typically center on desiccant wheel or fixed-bed designs classified under F24F, where a rotating or static solid sorbent material adsorbs moisture from an air stream and is regenerated with heated air. Liquid desiccant patents instead claim a circulating liquid sorbent solution, an air contactor, and a regenerator that concentrates the solution for reuse, often paired with heat pump or waste-heat regeneration. Both branches appear heavily in this dataset, but liquid desiccant claims more frequently intersect with B01D separation-process classifications, while solid desiccant claims sit almost entirely within F24F. Recent filings such as electrochemically regenerated liquid desiccant systems show the liquid branch is where more novel regeneration chemistry is currently being filed.

The assignee base spans national research organizations, HVAC equipment manufacturers, and a smaller group of specialized entrants; no single assignee dominates the 156-family corpus outright. Recent-year momentum data shows that even the most historically active filers, including newer entrants like Mojave Energy Systems, show zero filings in the most recent tracked year, though this likely reflects publication lag rather than an actual stop in activity. Co-filing is uncommon, with only nine co-assignee pairs across the entire dataset, indicating that most organizations file independently rather than through joint ventures. A practitioner assessing competitive position should treat the most-cited older patents, several from 1989-1991, as the foundational prior art still shaping claim scope today.

The filing trend is flat to declining, not growing. Activity built up from zero in 2017 to a peak of 13 families in 2022, and has not exceeded that level in any year since, with the midpoint year of the coverage window matching the peak year itself. The final one to two years of the dataset are understated because patent publication typically lags the actual filing date by around 18 months, so a modest uptick could still be revealed as more 2025-2026 filings publish. As it stands, this reads as a mature technology space where filers are working within established claim territory rather than a fast-expanding one.

The clearest gap is in sorbent chemistry itself: B01J, the subclass covering sorption and catalytic material claims, appears in only 16 of 156 records compared to 146 for the overarching F24F air-conditioning system classification. That imbalance suggests most patenting effort has gone into system architecture and air-handling integration rather than into novel desiccant materials, regeneration heat recovery methods, or solar-assisted regeneration, all of which show single-digit representation in the IPC breakdown. A first claim in one of these under-claimed branches would likely center on a specific sorbent formulation or regeneration heat-source combination rather than another variant of wheel or liquid-loop system architecture, which is already densely claimed.

US11944934B2, assigned to Mojave Energy Systems and published in 2024, claims a liquid desiccant regenerator that produces a concentrated output stream and a diluted output stream while using a secondary heat pump to manage the temperature drop caused by regeneration. Anyone designing an electrochemically or heat-pump-assisted regeneration loop for liquid desiccant should review its claim scope closely, since it sits in a part of the corpus, electrochemical regeneration, that is thinly populated relative to thermal regeneration approaches. Design-around routes likely involve alternative regeneration heat sources, such as solar-thermal or waste-heat recovery, that avoid the specific secondary heat pump configuration this patent describes. This is not a blanket block on liquid desiccant systems generally, only on the particular regeneration-and-heat-pump combination it claims.