Phase-Change Thermal Storage Patents: Leaders & Filing Trends 2026
- 5,381 families tracked, with filings peaking in 2022 at 247 and flattening since — this is a maturing claim space, not a growing one.
- Heat-exchange apparatus (F28D) and materials (C09K) together account for the large majority of records, meaning encapsulation and heat-exchanger integration are the two most contested fronts.
- Japan leads receiving offices by a wide margin (2,642), with the US, EPO, PCT and Germany trailing well behind — filing strategy here is Japan-centric first.
Filing growth compares 2021 (154 records) with 2024 (72) — 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 5,381 records in scope (CR5), not by the ranked leaders only.
What the phase-change thermal storage patent landscape looks like
Phase-change thermal storage covers the materials and hardware that store and release heat through a material’s latent heat of fusion — PCM formulation, PCM encapsulation, and the heat exchangers and building elements that put those materials to work. The dataset spans 5,381 patent families filed between 2015 and mid-2026, drawn from a search string that requires both a phase-change or latent-heat-storage term and a formulation, encapsulation or material claim to co-occur. That combination biases the corpus toward substantive materials and packaging claims rather than passing mentions of PCM in unrelated heating patents.
Filing activity rose through the late 2010s, peaked in 2022 at 247 records, and has since declined — a pattern consistent with a technology area where the core claim space is now occupied rather than one still being opened up. Because publication typically lags filing by around 18 months, the last one to two years of the trend understate true filing activity and should be read as provisional.
Let an AI agent run this analysis on your own technology
Pick a task. Every answer cites the patents behind it.
Filing trend and technology composition
Two views of the same 5,381-family dataset: how filing volume has moved year over year, and how those filings split across IPC subclasses.
A 2022 peak followed by decline
Annual filings ran from 173 in 2017 to a peak of 247 in 2022, then eased off toward the present. Read the final one to two years as undercounted given publication lag, but the multi-year plateau before that is real and points to a technology whose core claims are largely staked out.
Heat-exchange hardware and materials dominate
F28D (heat-exchange apparatus) and C09K (materials for miscellaneous applications) are the two largest subclasses by a wide margin, followed by F24D domestic heating, F24H fluid heaters, F28F heat-exchanger details, F24F air conditioning, F25B refrigeration and heat pumps, and E04B building structures. The concentration in F28D and C09K shows that most inventive effort has gone into the material itself and how it is packaged into a heat exchanger, rather than into the downstream appliance categories.
Shares are the percentage of the 5,381 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Phase-Change Thermal Storage Thermal Storage with Eureka
This page is one run against one query. Ask Eureka your own question about phase-change thermal storage thermal storage and every answer comes back with the patent numbers behind it.
Try EurekaA representative filing and the most-cited prior art
Latent Heat Storage Material and Process for Manufacture of the Latent Heat Storage Material
The invention relates to a latent heat storage material comprising a first phase change material, at least one second phase change material different from the first, and an expanded graphite material, wherein the two phase change materials are intermixed and the resulting composite exhibits a phase transition over a range of temperatures rather than a single point. The invention also covers a process for preparing the material by combining expanded graphite and a first phase change material with a second, different phase change material.Filed by SGL CARBON SE, published 2008-09-25 as US20080230203A1.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US8921473B1 | Image making medium | 272 |
| 2 | US20100108694A1 | Heat-insulating container | 214 |
| 3 | US6482332B1 | Phase change formulation | 190 |
| 4 | US8587945B1 | Systems structures and materials for electronic device cooling | 165 |
| 5 | US5269145A | Heat storage system with combined heat storage device | 147 |
| 6 | JP1991031666A | Heat pump type air conditioner | 142 |
| 7 | US20150267612A1 | Compressed air energy storage and recovery | 138 |
| 8 | US20120067047A1 | System and method for storing energy and purifying fluid | 122 |
| 9 | US5449571A | Encapsulations for thermal management system for battery | 101 |
| 10 | US20030118822A1 | Microcapsules | 99 |
Citation counts inside a searched corpus favour older filings that have had more years to accumulate citations — treat them as a signal of influence on the field, not of current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
Put your own technology through the same analysis
Eureka on the web
When you want the answer in the next five minutes.
The agent works the prompt against patents and technical literature, citing every source.
Run your analysis now →MCP server & REST API
When it has to run inside your own pipeline.
Patent search, landscape analysis and assignee resolution as MCP tools. Drop them into any agent framework, or call REST directly.
Browse MCP servers →What the numbers say about where this field is heading
Four patterns stand out once filing volume, IPC composition and receiving-office data are put side by side.
The claim space has stopped expanding
Annual filings climbed from 173 in 2017 to a 2022 peak of 247 and have declined in the years since. Combined with publication lag, this points to a field consolidating around established formulations and encapsulation methods rather than opening new ground.
Hardware and material claims dominate over appliance claims
F28D heat-exchange apparatus and C09K materials together outweigh the domestic heating, water heating, air conditioning and refrigeration subclasses combined, showing the fight is over the material and its containment, not the end appliance.
Filing strategy is concentrated in Japan first
Japan accounts for far more receiving-office filings than the US, EPO, WIPO/PCT, Germany or India combined, indicating that domestic Japanese filing remains the primary route to protection in this field, with international filing a secondary step.
Established filers have gone quiet in the most recent year
Several of the historically active assignees show zero filings in the latest tracked year. Given publication lag this may partly reflect filings still working through the pipeline, but it is also consistent with those portfolios having reached a mature, defensive state.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to phase-change thermal storage thermal storage, with the prior art for and against each one.
Who holds the deepest positions, and where the field is still open
Portfolio depth in this dataset sits with a small set of Japanese electronics and energy conglomerates plus specialty materials firms, alongside co-filing pairs that suggest supplier relationships around encapsulation materials.
Co-filing points to materials-supplier relationships
The strongest co-assignee pairs link a large industrial conglomerate with a specialty chemical or materials supplier, and a heavy-industry parent with its energy-systems subsidiary. This pattern is typical of arrangements where one party supplies the PCM or encapsulation chemistry and the other integrates it into hardware.
Japanese conglomerates set the filing pace
The receiving-office data and the assignee list both point toward Japan as the centre of gravity for this technology, with large electronics and heavy-industry groups filing domestically well ahead of international counterparts.
Top historical assignees show no recent activity
None of the most prominent long-running assignees in this dataset recorded a filing in the latest tracked year. That is consistent with either a pipeline lag in publication or a shift of active filing to smaller or newer entrants not yet visible at the top of the ranking.
| Assignee | Recent year | YoY |
|---|---|---|
| Matsushita Electric Industrial Co., Ltd. (Japan) | 0 | — |
| Matsushita Electric Works, Ltd. | 0 | — |
| Hitachi, Ltd. | 0 | — |
| Octopus Energy Heating Ltd. | 0 | — |
| Mitsubishi Electric Corporation | 0 | — |
| Toshiba Corporation | 0 | — |
| Yazaki Energy System Corporation | 0 | — |
| BASF SE | 0 | — |
Using this landscape to make a filing or freedom-to-operate decision
The data points to where claim density is high and where it thins out — the next step is testing a specific formulation or encapsulation approach against that map.
Check freedom-to-operate before drafting claims
With F28D and C09K carrying the bulk of prior art, any new filing on PCM encapsulation or heat-exchanger integration should be checked against the densest part of this corpus first, not the periphery.
Run a freedom-to-operate check in EurekaTrack the assignees that have gone quiet
Several major historical filers show zero activity in the latest year. Understanding whether that is a publication-lag artefact or a genuine pull-back matters for competitive positioning.
Monitor assignee activity in EurekaExplore the under-claimed branches directly
Building-envelope integration, refrigeration coupling and air-handling buffering all show thinner filing density than the core material and heat-exchanger subclasses.
Explore white space in EurekaCommon questions about phase-change thermal storage patents
In this dataset, a record has to combine a phase-change or latent-heat-storage term with a formulation, encapsulation or material-specific claim, which filters out patents that merely mention PCM in passing. This produces a corpus weighted toward substantive materials science and packaging engineering rather than general HVAC hardware. Most records fall into heat-exchange apparatus (F28D) or materials for miscellaneous applications (C09K), with domestic heating, water heating, air conditioning, refrigeration and building-structure subclasses making up smaller shares.
Portfolio depth in this corpus concentrates among large Japanese electronics and heavy-industry groups alongside specialty materials suppliers, with several co-filing pairs suggesting supplier-integrator relationships around encapsulation chemistry. However, a number of the most prominent historical filers show no recorded activity in the latest tracked year, so current leadership by volume and current leadership by recent momentum are not the same question. Checking the full assignee ranking alongside the recent-year momentum data is the more reliable way to answer this for a specific company.
Filing volume rose from 173 in 2017 to a peak of 247 in 2022, then declined in subsequent years, which is a flat-to-declining pattern rather than sustained growth. Publication lag of roughly 18 months means the most recent one to two years understate true filing activity, so the decline should not be read as sudden. Taken together with the multi-year plateau before the peak, the pattern is more consistent with a maturing claim space than an emerging one.
The core material and heat-exchanger subclasses, F28D and C09K, carry the bulk of filings, while building-envelope integration (E04B), refrigeration-cycle coupling (F25B) and air-handling buffering (F24F) show comparatively thinner density. Multi-transition composite PCM blends and graded-temperature encapsulation shells are two specific formulation approaches that appear less densely claimed than single-transition, single-shell designs. These are reasonable starting points for a novelty search, not guarantees of open claim space, since density in a corpus does not map perfectly onto legal freedom to operate.
Japan accounts for 2,642 of the receiving-office filings in this dataset, well ahead of the United States at 764 and the European Patent Office at 560. This reflects both a concentration of active assignees headquartered in Japan and a domestic-first filing strategy common among large Japanese conglomerates, who often file at the Japan Patent Office before deciding which markets warrant PCT or direct international filing. It does not necessarily mean the underlying technology is used more in Japan, only that protection is sought there first.
Research Phase-Change Thermal Storage Thermal Storage in depth with Eureka
Go past this page: query the whole phase-change thermal storage thermal storage corpus yourself, in your own scope.
Every answer comes back with patent numbers you can open.
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.