Phase Change Material Patents: Filing Trends & Top Companies 2026
- Filings peaked in 2017 at 158 and have since flattened the 2022 midpoint of 148 sits close to the peak rather than trending upward, suggesting the field is holding its filing rate rather than accelerating.
- Materials science, not hardware, dominates the claim space C09K (materials for misc. applications) covers 1,600 records against F28D's 1,340, meaning composition and additive claims are more contested than exchanger geometry.
- The United States leads filing venues by a wide margin 614 records at the USPTO versus 378 in China and 346 at the EPO, with recent-year momentum flat across every major named assignee in the dataset.
Filing growth compares 2021 (152 records) with 2024 (133) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 2,443 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
Phase change material (PCM) thermal storage patents span two distinct problems: formulating a material that melts and solidifies at a useful temperature without degrading, and engineering the hardware that gets heat into and out of that material fast enough to be useful. This dataset pulls 2,443 patent families filed between 2015 and mid-2026 that combine PCM or latent-heat-storage language with claim terms around encapsulation, supercooling, thermal conductivity enhancement, cycling stability or melting temperature, under IPC classes covering thermal storage media, heat-exchange apparatus and domestic heating systems.
Publication lags filing by roughly 18 months, so the 2026 count of 31 understates actual filing activity for that year. The trend should be read through 2024 or earlier for a reliable signal.
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Filing trend and technology composition
Two views of the same 2,443-family dataset: how filing volume has moved year over year, and which IPC subclasses carry the claim density.
A peak in 2017, then a plateau
Filings hit 158 in 2017, the high point of the dataset, and by the midpoint year of 2022 volume had only reached 148 — essentially flat rather than growing. That pattern points to a technology area where the core claim territory was staked out early and subsequent filing has been incremental rather than expansionary.
Materials claims outnumber apparatus claims
C09K (materials for miscellaneous applications) accounts for 1,600 records, ahead of F28D heat-exchange apparatus at 1,340. Smaller but active clusters sit in F28F heat-exchanger details (189), B01J chemical/physical processes (142), C08K polymer additives (142) and C08L polymer compositions (138) — together indicating that composite and polymer-based PCM formulations are a meaningfully separate claim front from bulk heat-exchanger design.
Shares are the percentage of the 2,443 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Phase Change Material Thermal Storage with Eureka
This page is one run against one query. Ask Eureka your own question about phase change material thermal storage and every answer comes back with the patent numbers behind it.
Try EurekaThe most-cited prior art in this space
Salt hydrate-based thermal energy storage material with near-ambient phase change temperature
UT-BATTELLE's application claims a eutectic mixture of two or more salt hydrates — specifically calcium chloride hexahydrate and magnesium chloride hexahydrate — combined with a bromide salt and bromide salt hydrate additive. The additive both lowers the melting temperature of the base mixture toward near-ambient conditions and suppresses supercooling, addressing the two failure modes that have historically limited salt-hydrate PCMs against paraffin and fatty-acid alternatives.Filed 2025-02-27. Number and assignee rendered from the underlying record.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US4964402A | Orthopedic device having gel pad with phase change material | 384 |
| 2 | US6855410B2 | Phase change material thermal capacitor clothing | 292 |
| 3 | US5901572A | Auxiliary heating and air conditioning system for a motor vehicle | 272 |
| 4 | US20120227926A1 | Energy storage systems | 245 |
| 5 | US4708812A | Encapsulation of phase change materials | 222 |
| 6 | US4982722A | Heat retentive server with phase change core | 211 |
| 7 | US4259401A | Methods, apparatus, and compositions for storing heat for the heating and cooling of buildings | 208 |
| 8 | US5884006A | Rechargeable phase change material unit and food warming device | 202 |
| 9 | US5565132A | Thermoplastic, moldable, non-exuding phase change materials | 194 |
| 10 | US6482332B1 | Phase change formulation | 190 |
Citation counts inside a searched corpus skew toward older filings simply because they have had more time to accumulate citations; treat this table as a map of influential prior art, not a ranking of current importance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers say about where this field stands
Four signals from the dataset that matter more for filing strategy than the headline family count.
Growth has stalled, not accelerated
The 2017 peak of 158 filings has never been re-approached; the 2022 midpoint of 148 is the closest the field has come since. A dataset like this, flat rather than climbing, usually means the foundational composition and encapsulation claims were filed early and later entrants are filing around narrower improvements.
The US remains the primary filing venue
With 614 records at the USPTO against 378 in China, 346 at the EPO, 255 via WIPO/PCT, 178 in India and 168 in Japan, enforcement and freedom-to-operate diligence for this technology should start with US prior art regardless of where a product will ultimately ship.
Materials claims outweigh apparatus claims
C09K materials-for-applications records outnumber F28D heat-exchange apparatus records by roughly 260, with polymer additive classes C08K and C08L each contributing 142 and 138 more. Composition and stabiliser chemistry is the more heavily claimed layer of this stack.
No named assignee is currently accelerating
Every major assignee tracked in recent-year momentum — including large industrial names — shows zero filings in the latest year, with at least one showing a full -100% year-on-year drop. That flat pattern across the leaderboard, not just one firm slowing, is consistent with the plateau visible in the overall trend line.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to phase change material thermal storage, with the prior art for and against each one.
Who holds the claim space
Assignee activity in this dataset is concentrated among a handful of named organisations, several of which co-file with individual inventors, alongside a long tail of single-filing entrants typical of a materials-chemistry field.
Collaboration is narrow and repeat-based
The strongest co-assignee relationship in the dataset appears 6 times, and the next strongest pairs, involving individual named inventors alongside a corporate assignee, appear 4 times each. This is a field of largely independent filers rather than joint-venture-heavy development.
US filings set the enforcement baseline
With more than 1.6 times the filing volume of the next-largest office (China at 378), any freedom-to-operate review for products entering the US market needs to treat the US filing corpus as the primary clearance set, not a secondary check.
The leaderboard has gone quiet
Assignees that were active enough to be tracked for momentum, spanning industrial materials firms and specialty PCM suppliers, all report zero filings in the most recent year. That is consistent with the field-wide plateau rather than a single company's retreat.
| Assignee | Recent year | YoY |
|---|---|---|
| University of Dayton | 0 | — |
| Outlast Technologies LLC | 0 | — |
| Sunamp Limited | 0 | -100% |
| Panasonic Corporation (Japan) | 0 | — |
| Honeywell International Inc. | 0 | — |
| Octopus Energy Heating Limited | 0 | — |
| Climate Change Technologies LLC | 0 | — |
| Dow Global Technologies LLC | 0 | — |
Where to take this analysis
The dataset points to a plateaued but still-active field with clear venue and claim-type concentration. The next steps depend on whether the goal is freedom-to-operate, white-space filing or competitive tracking.
Run a freedom-to-operate check against the US corpus
With 614 of 2,443 families filed at the USPTO, any product entering the US market should be checked against this subset first, particularly around the high-citation encapsulation and phase-change-composition patents identified in this landscape.
Explore prior art in EurekaMap claim language in the salt-hydrate and additive space
The bromide-additive approach to supercooling suppression shown in the representative filing is one of several active formulation routes; comparing claim scope across recent salt-hydrate filings can surface where narrower claims still leave room to file.
Compare claims in EurekaTrack assignee activity for renewed filing signals
Every leading assignee shows zero filings in the latest tracked year; a renewed uptick from any one of them would be an early signal worth monitoring rather than assuming the field has permanently plateaued.
Set up assignee tracking in EurekaCommon questions about PCM thermal storage patents
The dataset shows filings peaking at 158 in 2017 and never clearly exceeding that again, with the 2022 midpoint at 148. This pattern typically appears when the foundational composition and encapsulation claims for a technology are staked out early, after which later filers work around narrower improvements rather than opening new claim territory. It does not mean research activity has stopped; it means the core claim space is comparatively settled. Readers should also account for publication lag, since the most recent one to two years in any such dataset are always undercounted relative to actual filing activity.
Start with the United States, which accounts for 614 of the 2,443 families in this dataset, well ahead of China (378) and the European Patent Office (346). India, Japan and WIPO/PCT filings make up the remainder. If a product will be sold or manufactured in multiple regions, a full clearance review should still cover China and Europe, but the US corpus is the largest single body of relevant prior art to search first.
Materials claims currently outweigh apparatus claims in this dataset: C09K (materials for miscellaneous applications) covers 1,600 records versus F28D (heat-exchange apparatus) at 1,340. Additional materials-adjacent activity appears in B01J, C08K and C08L, covering catalysis, polymer additives and polymer compositions respectively. This suggests that formulation, additive chemistry and stabilisation techniques are a more heavily contested claim layer than the physical heat-exchanger hardware itself.
Supercooling is the tendency of a phase change material to remain liquid below its nominal freezing point, which reduces the reliability of latent heat release; suppressing it is a recurring claim element across this dataset's search terms. The representative recent filing, UT-BATTELLE's near-ambient salt hydrate composition, claims a bromide salt and bromide salt hydrate additive specifically to reduce supercooling alongside lowering melting temperature. Because this is an active and comparatively recent formulation route, new entrants should expect to encounter existing additive-combination claims and should check specific salt-pair and additive-ratio language closely before filing similar compositions.
Yes, though it is narrower than in a fast-growing field. Sub-areas with comparatively thinner claim density relative to the core materials and apparatus clusters include salt-hydrate eutectic formulations tuned for near-ambient melting points, polymer-matrix PCM composites that sit at the overlap of C08K and C08L, and building- or domestic-heating-integrated PCM elements that overlap E04B and F24D but are not the primary focus of either. These overlap zones tend to be under-claimed precisely because they sit between established IPC classes rather than squarely within one.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.