Thermal Energy Storage Patents: Who Leads, Where Gaps Sit 2026
- Filings have cooled since the 2022 peak. 183 families published that year against 88 in 2017 and 30 so far in 2026, a pattern of decline once the trailing years are read with publication lag in mind.
- Heat-exchange apparatus dominates the IPC mix. F28D accounts for 1,757 of 2,128 records, more than twice the next largest subclass, C09K materials at 737 — most invention effort sits in exchanger hardware, not storage media.
- No assignee is filing at pace right now. Every tracked assignee in the momentum data shows 0 filings in the latest year, several down -100% YoY, which points to a field between waves rather than one with an active leader pulling away.
Filing growth compares 2021 (132 records) with 2024 (123) — 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 2,128 records in scope (CR5), not by the ranked leaders only.
What this dataset covers
This landscape draws on 2,128 patent families published between 2017 and 2026, pulled from a search combining thermal energy storage, latent heat storage and sensible heat storage terms with claim-level references to phase change materials, molten salt storage, thermochemical storage and heat storage systems. The IPC filter narrows the set to F28D20 (heat storage), C09K5/06 (heat transfer materials) and F24H7 (fluid heaters), so the corpus is centred on hardware and materials claims rather than adjacent grid-scale or battery chemistry filings.
Filings peaked in 2022 and have declined since; because publication typically lags filing by around 18 months, the final one or two years in any trend understate real activity and should be read as provisional rather than as a confirmed drop-off.
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Filing trend and technology composition
Two views of the same corpus: how filing volume has moved year over year, and how the 2,128 records split across IPC subclasses.
Filing trend, 2017-2026
Volume rose from 88 families in 2017 to a peak of 183 in 2022, then eased back toward 30 in 2026 — a partial year still subject to publication lag. Read the last two years as a floor, not a final count.
IPC subclass composition
F28D (heat-exchange apparatus) covers the largest share at 1,757 records, followed by C09K (materials, 737), F28F (exchanger details, 216), F01K (thermal power plants, 197), F24H (fluid heaters, 148), F24S (solar collectors, 144), F24D (domestic heating, 139) and F24F (air conditioning, 119). The gap between F28D and every other subclass shows most claim activity concentrates on exchanger hardware rather than storage chemistry or system-level integration.
Shares are the percentage of the 2,128 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Thermal Energy Storage Landscape with Eureka
This page is one run against one query. Ask Eureka your own question about thermal energy storage landscape and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited records and a representative filing
Latent heat storage system having a latent heat storage device and method for operating a latent heat storage system
A latent heat storage system includes at least one latent heat storage device containing a storage medium with latent heat, at least one heat pump coupled to the storage device, an extraction circuit with a first heat carrier medium for extracting heat from the storage medium and supplying it to the heat pump, and an extraction heat exchanger in contact with the storage medium and connected to the extraction circuit. A coupling device sits between the extraction heat exchanger and the heat pump.Filed by Viessmann Werke, published 2020-05-28 — see the chat panel for what its claims block and where the workable alternatives sit.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US4964402A | Orthopedic device having gel pad with phase change material | 384 |
| 2 | US6059016A | Thermal energy storage and delivery system | 280 |
| 3 | US4572864A | Composite materials for thermal energy storage | 255 |
| 4 | US20120227926A1 | Energy storage systems | 245 |
| 5 | US5565132A | Thermoplastic, moldable, non-exuding phase change materials | 194 |
| 6 | US5053446A | Polyolefin composites containing a phase change material | 171 |
| 7 | US4504402A | Encapsulated phase change thermal energy storage materials | 169 |
| 8 | US4807696A | Thermal energy storage apparatus using encapsulated phase change material | 163 |
| 9 | US4124061A | Thermal energy storage unit | 163 |
| 10 | US20110226440A1 | Energy storage systems | 155 |
Citation counts favour older filings simply because they have had longer to accumulate references inside this searched corpus — treat them as a signal of historical influence, not of current relevance to new filings.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers mean for a filing decision
Three read-outs from the trend, the IPC split and the citation table, each aimed at a specific question a filing team would ask.
The wave has already crested
Filing volume rose steadily from 88 in 2017 to a peak of 183 in 2022, then declined in every subsequent year. Even allowing for publication lag understating 2025-2026, the shape is one of a maturing filing cycle rather than an accelerating one.
Hardware claims crowd the field
F28D heat-exchange apparatus appears in more than 80% of records, over twice the count of C09K materials claims. New filers competing on exchanger geometry or heat-transfer surface design are entering the densest part of the corpus.
US and Europe anchor filing strategy
The United States and the EPO together account for more receiving-office activity than India, China and Australia combined in this dataset, with WIPO PCT filings a distant third. Freedom-to-operate work should prioritise US and EP prosecution history before regional offices.
No single assignee is currently pushing volume
Every assignee named in the momentum data shows zero filings in the most recent year, several down -100% year over year. That does not mean the field is closed — it means no incumbent is currently building a fresh filing position, which is itself useful for a team deciding when to file.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to thermal energy storage landscape, with the prior art for and against each one.
Assignee landscape and collaboration signals
Filing activity in this corpus sits across a mix of chemicals groups, university labs and HVAC manufacturers, with a small number of recorded co-assignee pairs pointing to internal R&D collaboration rather than cross-company joint filing.
Collaboration is internal, not cross-company
The strongest co-assignee pairs link a single corporate assignee to named individual inventors rather than to other companies, suggesting the collaboration signal here reflects internal inventor teams rather than joint ventures or licensing partnerships.
Materials assignees sit behind the hardware leaders
Chemicals and materials-focused assignees appear consistently in the C09K subclass, filing on phase-change and heat-transfer compositions rather than the exchanger hardware that dominates F28D.
Recent leaders have gone quiet
Assignees with historically strong filing records show no activity in the latest tracked year. That combination of past volume and current silence is worth checking against each assignee's broader portfolio before assuming they have exited the space.
| Assignee | Recent year | YoY |
|---|---|---|
| Sunamp Limited | 0 | -100% |
| Rondo Energy | 0 | -100% |
| Phase Change Energy Solutions | 0 | -100% |
| University of Dayton | 0 | — |
| EnergyNest | 0 | — |
| Dow Global Technologies | 0 | — |
| Azelio AB | 0 | — |
| Climate Change Technologies LLC | 0 | — |
Where to take this analysis
The dataset points to specific next steps depending on whether you are scoping freedom-to-operate, deciding where to file, or tracking a competitor.
Run a claim-level search on the exchanger cluster
F28D concentration means a generic heat-exchange claim is unlikely to clear prior art on novelty alone. Narrow to the specific coupling mechanism or medium before filing.
Explore in EurekaCheck assignee portfolios beyond the momentum snapshot
Zero filings in the latest year does not confirm exit from the field; several assignees may be consolidating filings into fewer, broader applications.
Explore in EurekaTrack the under-claimed branches directly
Thermochemical reactor integration and molten salt containment show thinner claim density than the core exchanger cluster — worth a dedicated watch as filing volume shifts.
Explore in EurekaCommon questions on thermal energy storage patents
This dataset tracks assignee filing volume across 2,128 patent families, but the momentum data shows every tracked top assignee filed zero patents in the most recent year, several down -100% year over year from prior activity. That means historical leadership in this space does not currently translate into active filing pressure from any single company. Anyone evaluating a leader should look at cumulative portfolio size alongside recent momentum rather than relying on either figure alone.
No — filings rose from 88 in 2017 to a peak of 183 in 2022, then declined through 2026. Because patent publication typically lags filing by around 18 months, the most recent one to two years understate true filing activity, so the decline may be partly an artifact of the data cut-off. Even accounting for that lag, the overall shape is a completed growth cycle rather than an accelerating one.
Heat-exchange apparatus, classified under IPC subclass F28D, accounts for 1,757 of the 2,128 records in this corpus — more than 80% of filings. Materials for phase-change and heat-transfer applications (C09K) form the second-largest cluster at 737 records. Smaller clusters cover exchanger details, thermal power plants, fluid heaters, solar collectors, domestic heating and air conditioning, each under 220 records, indicating that most invention effort targets exchanger hardware rather than system integration or novel storage chemistry.
The United States (541 records), the European Patent Office (359) and WIPO's PCT route (233) are the leading receiving offices in this dataset, well ahead of India, China and Australia. That distribution reflects where applicants have historically sought protection and prosecution history, not necessarily where the largest future market lies, so a filing strategy should still weigh manufacturing and deployment geography separately.
The corpus shows dense claim coverage in exchanger hardware and general phase-change materials, but comparatively thinner coverage in thermochemical storage reactor integration, molten salt corrosion-resistant containment, and heat pump coupling mechanisms to latent storage circuits. These adjacent branches sit close to the dense clusters without matching their filing density, which makes them worth a focused prior-art search before assuming the space is occupied.
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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.