COMPANY PROFILE / NEXT-GEN ENERGY STORAGE
Sumitomo Electric Industries
After some 40 years on the redox flow battery, a company launching a "30-year" model and widening its storage-site orders
Sumitomo Electric appears in next-generation energy storage because it handles the redox flow battery (RFB), which holds vanadium electrolyte in tanks and circulates it by pump, from the battery itself through to installing and operating the storage site. In April 2022, a grid-side battery of 17,000 kW and 51,000 kWh began operation at Hokkaido Electric Power Network's Minami-Hayakita Substation. In September 2025 it unveiled the new V40 series, which it says can run for up to 30 years and offers about 30% more output; in 2026 three projects were selected for a METI subsidy for grid-scale batteries, and Hokkaido Electric Power Network chose it for a third time. Yet the company's own magazine records that, after development began in the 1980s, management decided in 2005 to withdraw, and revived the business in 2009, and the company itself says its greatest challenge is price. This profile covers the redox flow battery only, not Sumitomo Electric as a whole, and sets out from primary sources what the company has committed, with whom it works and how much it discloses.
- Sumitomo Electric in 30 seconds, and where it stands in next-generation energy storage
- The logo and how the name is written
- Where the company sits in the field
- Scale (kept brief, limited to the redox flow battery)
- Resources committed to next-generation energy storage
- What it has done so far
- What comes next
- What the company is aiming for in energy storage
- Map of partnerships in next-generation energy storage
- Technologies, products and services
- The risks this company carries
- Glossary, references and claim-to-source audit
1. Sumitomo Electric in 30 seconds, and where it stands in next-generation energy storage
securities code 5802From the Integrated Report 2026. Tokyo Prime Market
Storage systems (secondary)From the battery to installing and operating the storage site
new "V40 series"2 MW systems with 4, 6 and 8 hours of capacity
51,000 kWhHokkaido Electric Power Network. Operation began in April 2022
a third in HokkaidoAnnounced February to April 2026. All to be built
Because the tank size sets how long it can discharge, the redox flow battery suits long-duration storage, from several hours to more than ten. The company lists as its features that the electrolyte is non-flammable and is not a hazardous material under Japan's Fire Service Act, that charge and discharge cycles do not accelerate degradation, and that the electrolyte can be reused Sourced. But the development history has not been smooth. Sumitomo Electric began development in 1982 and started delivering to universities and factories in 2001, but breakdowns followed, and in 2005 management decided to withdraw. It revived the business in 2009, and after large demonstrations with Hokkaido Electric Power and in the United States, began operating in 2022 what the company describes as the world's largest-scale facility. The company itself says that its biggest challenge is "achieving a price customers are satisfied with". So this is the story of a company that has polished the technology for a long time, while the profitability of the business depends on lowering price and cost.
2. The logo and how the name is written
A note on names: the legal entity is Sumitomo Electric Industries, Ltd. (called Sumitomo Denko in Japan). Group companies such as Nissin Electric, Sumitomo Densetsu (all of whose shares the company sold in March 2026), Sumitomo Wiring Systems and Sumitomo Riko are separate legal entities. V40 series is the model name of the new redox flow battery, not a legal entity. Vecco Group is an Australian electrolyte maker and John Cockerill a Belgian customer; neither is a Sumitomo Electric subsidiary. This profile covers the redox flow battery only; it does not cover power cables, automotive wiring harnesses, optical fibre or other businesses, nor the home storage battery "POWER DEPO". The logo image was taken from Sumitomo Electric's official website.
Official site: https://sumitomoelectric.com/3. Where the company sits in the field
This series sorts companies in next-generation energy storage into four types: cells & materials, long-duration & new chemistries, storage systems & operators, and recycling. Sumitomo Electric's redox flow battery uses a chemistry different from lithium-ion (vanadium electrolyte), and its feature is long-duration storage of several hours to more than ten, so it falls under long-duration & new chemistries. Because it also delivers the containers, installs and maintains the storage site and offers operating software (sEMSA), it has a secondary side as storage systems.
4. Scale (kept brief, limited to the redox flow battery)
Sumitomo Electric is a diversified manufacturer with five business segments, starting from wire and cable. The redox flow battery belongs to the "Environment & Energy" business. Only the group totals and the figures for that business are shown here Sourced.
| Indicator (¥ million) | Year to March 2025 | Year to March 2026 |
|---|---|---|
| Net sales (consolidated) | 4,679,789 | 5,110,171 |
| Ordinary profit (consolidated) | 309,496 | 431,274 |
| R&D expenses (whole group) | n/a | 162,858 |
| Capital expenditure (whole group) | n/a | 243,183 |
| Consolidated employees | 288,145 | 302,972 |
The "Environment & Energy" business
| ¥ million | Year to March 2025 | Year to March 2026 |
|---|---|---|
| Net sales | 1,081,344 | 1,178,780 |
| Operating profit | 78,718 Our calculation | 90,615 |
| R&D expenses | n/a | 19,292 |
| Capital expenditure | n/a | 51,639 |
| Employees (consolidated, excluding temporary) | n/a | 12,336 |
The operating profit for the year to March 2025 is our calculation: the ¥90,615 million for the year to March 2026 less the ¥11,897 million increase stated in the Securities Report. The company attributes the sales rise of this business to power cables, rectangular winding wire for electric-vehicle motors, Nissin Electric's switchgear and Sumitomo Densetsu's electrical work, and does not cite a contribution from redox flow batteries. Orders for construction and plants were ¥494,621 million (backlog ¥447,060 million).
Environment & Energy is mostly power cables, transmission and distribution equipment and winding wire, and sales, profit, orders and headcount for redox flow batteries alone are not disclosed in the materials we reviewed. The Integrated Report's sales by main product also has no entry for redox flow batteries Not yet confirmed. The Securities Report's R&D section says only, in one sentence, that it is "carrying out demonstration operation of a large-scale system" of redox flow batteries.
5. Resources committed to next-generation energy storage
Most headcount and money figures are not disclosed for the redox flow battery alone. What we could confirm, and what we could not, is set out below.
| Type of resource | What primary sources confirm | Category |
|---|---|---|
| People | The redox flow battery is handled by units including the Energy Systems Business Development Division (RFB development and RFB engineering departments) and the electrolyte development group of the Power Systems R&D Center (as named in the company magazine). RFB headcount is not disclosed. The Environment & Energy business has 12,336 employees (consolidated) | Sourced / not disclosed |
| Money (R&D) | Group R&D expenses were ¥162,858 million and those of the Environment & Energy business ¥19,292 million (superconductors, power cables, storage batteries and others combined). The RFB share is not disclosed | Sourced / not disclosed |
| Money (capital expenditure) | Capital expenditure of the Environment & Energy business was ¥51,639 million (mainly capacity increases and rationalization of transmission and distribution wire, cable and switchgear). Capital expenditure dedicated to RFB could not be found. The third Hokkaido Electric Power Network project, decided in April 2026, is a comprehensive contract covering 20 years of maintenance, operation and removal to 2049 | Sourced / not found |
| Investment, M&A, joint ventures, divestment | For the Boggabri mine, electrolyte made by Vecco Group (Australia), 51% held by an affiliate of Idemitsu's Australian subsidiary, is to be used. Joint R&D with Kansai Electric Power since the 1980s. In August 2025 it delivered to a university facility in tie-up with Kansai Electric's control system. No RFB-related investment, acquisition or sale of the business was found | Sourced / not found |
| Public funding and research institutions | NEDO's demonstration in California (fiscal 2015 to 2021, about ¥3.0 billion according to the person in charge). METI's emergency large-scale storage demonstration (fiscal 2013 to 2018, Hokkaido Electric Power; 15,000 kW, 60,000 kWh). On the customer side, METI grid-battery subsidies selected one project in 2025 (Shin-Idemitsu) and three in February 2026. Ministry of the Environment subsidy projects (Ama town in the Oki Islands, Minamikyushu city) | Sourced |
Status of main projects
| Project | Location | Scale (company's stated values) | Stage | Dates and notes |
|---|---|---|---|---|
| Hokkaido Electric Power Network, Minami-Hayakita Substation (grid-side battery) | Abira, Hokkaido | 17,000 kW, 51,000 kWh | Operating | Completed 31 March 2022, operation from April. Operating period 21 years. Used for compensating wind power fluctuation and more. The company calls it the world's largest-scale RFB facility |
| Same site, emergency large-scale storage demonstration | Same | 15,000 kW, 60,000 kWh | Operating | Began December 2015. The demonstration ended in fiscal 2018 and operation has continued since |
| Same, third project | Same | 11,000 kW x 3 hours (33,000 kWh) | Selected (April 2026). Not yet confirmed | Aims for completion at the end of May 2029. Selected in the tender for grid-side storage needed to connect 97,000 kW of wind generation |
| San Diego Gas & Electric (US) | California | 2 MW, 8 MWh (March 2017); 500 kW, 4 MWh (September 2024) | Operating | A NEDO project. Entered the wholesale electricity market (December 2018) and ran a microgrid on a live distribution network, a first for Japan and the US (December 2021) |
| Kashiwazaki city (Niigata) | Kashiwazaki, Niigata | 1,000 kW x 8 hours (8,000 kWh), four phases | Two completed; phases 3 and 4 in construction | Phase 1 September 2024, phase 2 March 2025, phase 3 planned for spring 2026, phase 4 started construction in July 2026 and is planned for spring 2027, bringing total capacity to 32,000 kWh. Completion of phase 3 could not be confirmed |
| Shin-Idemitsu, Nagasu storage station | Tamana, Kumamoto | 2,000 kW x 4 hours (8,000 kWh) | Under construction | Started March 2025; completion planned for October 2026. The first RFB selected for METI's grid-battery subsidy |
| Three projects selected for METI's subsidy | Namie (Fukushima), Taishi (Hyogo), Kurayoshi (Tottori) | 2 MW x 6 h, 2 MW x 4 h, 2 MW x 3 h (26 MWh in total) | Selected (February 2026). Not yet confirmed | The company says the V40's long life, safety and wide-area certification were valued |
| Boggabri coal mine (Australia) | Queensland | 2 MW x 6.3 hours (12.6 MWh) | Agreement to supply (November 2025) | To be combined with solar power installed by Idemitsu Australia |
| Ama town (Oki Islands) | Ama, Shimane | Final scale 4,000 kW, 12,500 kWh | Construction begun (January 2025) | Ministry of the Environment subsidy for remote islands; a joint effort by Chugoku Electric Power Transmission & Distribution, Ama town and Koko (a local company; name transliterated) |
| Other deliveries | Taiwan (ITRI), Australia (Energy Queensland), Belgium (John Cockerill), Minamikyushu (Kagoshima), Tsuruga (Fukui) | 1 MW, 3 MWh (Taiwan, Nov 2024); 250 kW, 750 kWh (Australia, Sep 2024); 500 kW, 1,700 kWh (Belgium, Oct 2018); 250 kW, 1,125 kWh (Minamikyushu, Apr 2025); 250 kW, 750 kWh (Tsuruga, Jan 2023) | Operating | Minamikyushu was the first RFB under a Ministry of the Environment subsidy. The official case page writes its capacity in "MWh"; we used 1,125 kWh (250 kW x 4.5 hours) from the press release |
The company explains the design freedom of this battery as power set by the number of cell stacks, and discharge time (capacity) set by the volume of electrolyte Sourced. In a lithium-ion battery the electrode materials decide both power and capacity; in a redox flow battery "where electricity is made" (the cell stack) and "where energy is stored" (the electrolyte tanks) are separate. So to double discharge time at the same power, it is enough to enlarge the electrolyte tanks, as the company explains it. On the other hand, the materials of electrode, membrane and electrolyte each affect power and energy density (energy storable per cubic metre of electrolyte). For the new V40 the company says energy density is up 15% (through a newly developed membrane and separate state-of-charge management of the positive and negative sides) and cost is down 30% (through higher cell-stack output and others), both against the third generation (test conditions are not published).
6. What it has done so far
| When | What happened | Why it matters |
|---|---|---|
| 1982 | The redox flow battery is adopted as a development theme for power storage; a new recruit is picked to lead it (company magazine). Joint R&D with Kansai Electric Power also begins | A new theme to move away from dependence on power cables. The company says it had no battery experience |
| 1989 | A 60 kW-class cell with iron-chromium electrolyte is built, but capacity fell because of hydrogen generation and performance could not be kept over time | Judged hard to commercialize then. The company says it later switched to vanadium electrolyte, improving electromotive force, power and energy density |
| 2001 | Begins delivering redox flow batteries to universities and factories | The company says durability was low and failures such as electrolyte leaks followed |
| 2005 | Management decides to withdraw from the redox flow battery | The company says troubleshooting became the main work after withdrawal |
| 2009 | The business is revived and full R&D resumes | The company says the background was demand for large-capacity batteries to store renewable energy, such as under the US Green New Deal |
| 2012 to 2018 | A 1,000 kW-class test system at the Yokohama Works (2012). Large-scale demonstration with Hokkaido Electric Power (from fiscal 2015). NEDO's California demonstration begins in fiscal 2015 | Operating technology and reliability were confirmed. The person in charge says the California project cost about ¥3.0 billion over more than seven years |
| 2020 to 2022 | Wins the tender for Hokkaido Electric Power Network's grid-side battery, starts construction in July 2020 and completes on 31 March 2022. In December 2021, runs a microgrid on a live distribution network in California, a first for Japan and the US | The person in charge says cost was the biggest issue in the tender |
| 2024 to 2025 | Deliveries to the US, Taiwan, Australia and more. January 2025: Oki Islands. March 2025: Shin-Idemitsu (the first RFB selected for a subsidy). April 2025: Minamikyushu completed. July 2025: third consecutive year of orders from Kashiwazaki | The number of sites at home and abroad grew |
| September 2025 | Unveils the new V40 series: up to 30 years of operation, about 30% more output than before. Announces orders to start from January 2026 | Extends the operating period from the earlier 20 years |
| February to September 2026 | Three projects selected for METI's subsidy (February). Orders for V40 begin, with 26 MWh selected under the subsidy (March). Third adoption by Hokkaido Electric Power Network (April). Kashiwazaki phase 4 construction starts (July). A 2 MW system is added (September) | Larger projects are increasing around the V40 |
7. What comes next
aims for completion end of May 2029A comprehensive contract covering 20 years of maintenance, operation and removal to 2049
completion planned October 2026Started March 2025. Selected for a subsidy
spring 2026 and spring 2027Phase 4 brings total capacity to 32,000 kWh
These items are the company's plans and schedules, not completed results Not yet confirmed. In its Integrated Report the company lists "winning large redox flow battery projects" among its policies for the Environment & Energy business Sourced. In September 2026 it also began selling the energy management system "sEMSA-ESS", which can manage up to 100 grid-storage sites centrally (we did not check its link to RFB). Further, the company magazine says it is working on a cheaper electrolyte to replace vanadium for the next generation (the stage and timing of that development could not be confirmed).
None of the following appears in the primary sources we reviewed Not yet confirmed.
Sales, order backlog and profit for RFB alone / cumulative installed base (output, capacity, number of projects) / manufacturing sites and capacity (battery, cell stack, electrolyte) / the price of the V40 and its measured performance (energy efficiency, degradation) / the state of development of the new electrolyte / the start and completion dates of the three subsidy projects / new plans abroad. Press-reported figures are not used here.
8. What the company is aiming for in energy storage
This section includes points the company has not stated directly. They are inferences from what the primary sources say, and each is given with its basis.
| What can be read from it | Primary-source basis | Category |
|---|---|---|
| Its main field is long-duration grid storage (3 to 8 hours or more) | The V40 comes as 2 MW x 4, 6 and 8 hours; the three selected projects are 3 to 6 hours, Kashiwazaki is 8 hours and Boggabri 6.3 hours. The company says that the longer the capacity, the better the cost advantage | Sourced |
| It puts safety and long life forward, not price, as reasons for selection | In the Shin-Idemitsu, Minamikyushu, Boggabri and Hokkaido projects, the company cites low fire risk, long life and operating record as the reasons customers chose it | Sourced (company statement) |
| It extends the operating period from 20 to 30 years to lower the cost per kW-year and compete in tenders | The company says 30-year operation helps hold down bid prices (yen per kW per year) in the long-term decarbonization power source auction | Sourced |
| The way of selling is widening from "selling a battery" to contracts that include long-term maintenance and operation | The third Hokkaido Electric Power Network project is a comprehensive contract including maintenance, operation and removal to 2049; the operating software sEMSA-ESS has also gone on sale | Inference |
| It is relying strongly on subsidy programmes to grow projects | Of the main recent domestic projects, the Nagasu project and the three of February 2026 were selected for METI subsidies. We could not confirm orders without subsidy | Inference |
According to the company magazine, the redox flow batteries delivered from 2001 had low durability and kept failing, for example by leaking electrolyte, so management decided to withdraw in 2005. The development team kept investigating causes afterwards, and the business was revived in 2009. The company explains the revival as the result of a changed environment, with demand for large batteries to store renewable energy, and of the work it had done on the causes of past troubles Sourced. From this we read that today's emphasis on "30-year operation" and on "eliminating leaks entirely" reflects the experience of that failure. Indeed, the magazine names "maintaining the long-term reliability of the cell stack" and "eliminating electrolyte leaks completely" as the main themes after the revival. But 30 years is stated as "the longest, with appropriate maintenance and inspection", not as a record of operation for 30 years Not yet confirmed (the new V40 has only just begun operating, so measured life cannot be confirmed).
9. Map of partnerships in next-generation energy storage
10. Technologies, products and services
As the company describes it, the redox flow battery works as follows Sourced. It charges and discharges using the oxidation and reduction of ions such as vanadium, holding the positive and negative electrolytes in tanks and circulating them to the cells by pump. The reaction involves only changes in the valence of vanadium ions in the electrolyte, with no dissolution or deposition of electrodes, so the company says electrodes and electrolyte hardly degrade.
| Product or item | What official materials say | Note |
|---|---|---|
| V40 series (new model) | 2 MW systems with capacity of 8 MWh (4 hours), 12 MWh (6 hours) and 16 MWh (8 hours). Modules are 334 kW (30-foot or 40-foot tank) or 250 kW (40-foot). A container design that the company says cuts transport and installation costs and footprint. JC-STAR 1-star cybersecurity certification obtained. A 1 MW system is also offered | Values are manufacturer's stated. Duration can be extended beyond 10 hours, the company says |
| V40 improvements (against the third generation) | Energy density up 15% (new membrane, separate state-of-charge management of the two sides). Cost down 30% (higher cell-stack output, less electrolyte, better manufacturing). Battery output up about 30% on the earlier model. Operating period up to 30 years (20 years for the earlier model) | Conditions and test methods of comparison are not published. The company's explanation, not measured values |
| Safety | The vanadium sulfate electrolyte is non-flammable and other materials are flame-retardant. UL1973 certification (North American safety standard) obtained. Not a hazardous material under the Fire Service Act, so no hazardous-materials installation permit or resident handler is needed. For the Boggabri mine, the company says the absence of ignitable materials and of thermal-runaway concern was valued | This article does not rank it against other batteries |
| Environment and recycling | Electrolyte is reusable (with a record). Equipment materials can be recycled at 99% with proper sorting (wide-area certification from the Ministry of the Environment). Industrial waste at removal below 1% (Oki Islands release, January 2025) | The number of reuse cases and their conditions could not be confirmed |
| Approach to cost | The longer the capacity, the lower the cost per capacity. No cell or electrolyte replacement and no special fire-fighting equipment needed. The company names its greatest challenge as "achieving a price customers are satisfied with" | Price is not published |
| Operation and management | The energy management system "sEMSA". In September 2026 it began selling "sEMSA-ESS", which manages up to 100 grid-storage sites centrally | Use together with RFB was confirmed in the Minamikyushu project. The third Hokkaido project is a comprehensive contract including maintenance, operation and removal |
The company says the key to cost reduction is higher cell-stack output, pursued through improved electrode and membrane materials and a cell structure that lowers pressure loss when circulating the electrolyte Sourced. It also says that the design of cell-stack materials and structure goes hand in hand with the properties of the electrolyte. And it says that the vanadium in today's electrolyte is expensive, with price-swing risk and uneven distribution of the resource, and that it is working toward a cheaper, more stably available raw material that could match vanadium in performance.
As a general point, in a redox flow battery the vanadium in the electrolyte is thought to account for a large part of the cost, so the price of the electrolyte and the output of the cell stack (how much power can be drawn from the same electrolyte) greatly affect system price (this is our own general explanation and not a breakdown the company has published). In fact the company does not disclose the cost or price breakdown of the electrolyte Not yet confirmed. Nor could we confirm the specific membrane and electrode materials from official materials. This article makes no comparison with other makers' batteries.
11. The risks this company carries
| Risk | What it involves | Category |
|---|---|---|
| Price and cost | The company itself says its biggest challenge is "achieving a price customers are satisfied with", and the person in charge says cost was the biggest issue in the Hokkaido Electric Power Network tender. It also says the vanadium in the electrolyte is expensive, with price swings and an uneven distribution of the resource | Sourced |
| Past withdrawal and reliability | After delivery from 2001, electrolyte leaks and other failures followed, and management decided to withdraw in 2005. Long-term reliability is now a focus, but the new V40's 30 years is a "longest" figure "with appropriate maintenance", not a record of operation | Sourced |
| Dependence on subsidy programmes | Some of the main recent domestic projects were selected for METI or Ministry of the Environment subsidies. This article has not checked the content or continuation of those programmes against government sources. We could not confirm orders if the subsidies shrank | Inference |
| Responsibility for long-term maintenance and operation | A comprehensive contract covering 20 years of maintenance, operation and removal, as in the third Hokkaido Electric Power Network project, needs cost estimates based on long operating experience. We did not find provisions or losses relating to RFB in the materials we reviewed | Not yet confirmed |
| Ramp-up of the new model | The V40 only began taking orders in 2026, and completion and operation of the selected projects are still to come. Measured energy efficiency and degradation could not be confirmed | Sourced / not found |
| Parts that cannot be checked from outside | RFB-only sales, profit, order backlog, production capacity, cumulative installed base and price are not disclosed, so the profitability of the business cannot be checked from outside | Not yet confirmed |
| Competition from other methods | In long-duration storage there is competition from other methods. This article has not been able to confirm, from primary sources, comparisons with other makers' products or market share | Not yet confirmed |
12. Glossary
- Redox flow battery (RFB)
- A storage battery that holds electrolyte containing active material (such as vanadium) in tanks and circulates it through cells by pump to charge and discharge.
- Cell stack
- Single cells with electrodes and membranes stacked together, where charging and discharging actually take place. Power is set by the number of cell stacks.
- Electrolyte
- The liquid containing active material. Here it is an aqueous solution of vanadium sulfate, and the tank volume sets the discharge time.
- Grid-side battery
- A large battery that a transmission and distribution operator places on the grid side, not at a power plant, to absorb renewable output swings collectively.
- Long-term decarbonization power source auction
- A tender run by OCCTO, Japan's grid coordination body, to encourage new investment in decarbonized power sources.
- UL1973
- One safety standard for stationary batteries. Sumitomo Electric says it has obtained certification.
- JC-STAR
- A scheme published by METI for assessing the security conformity of IoT products. One star is level 1.
- Wide-area certification
- A scheme in which a manufacturer, certified by the Minister of the Environment, collects its own products' waste over a wide area for recycling or proper treatment.
- NEDO
- New Energy and Industrial Technology Development Organization, a Japanese public agency that supports R&D and demonstration projects.
- Securities Report
- The annual report that listed companies in Japan file under the Financial Instruments and Exchange Act.
13. References
- Sumitomo Electric Industries 156th Securities Report (1 April 2025 to 31 March 2026, filed 26 June 2026), in Japanese. History, segment results and employees, R&D, capital expenditure. https://sumitomoelectric.com/jp/sites/japan/files/2026-06/download_documents/yuuka156.pdf
- Sumitomo Electric Industries Integrated Report 2026, in Japanese. Company overview, Environment & Energy strategy, timeline (start of commercial operation of a world-largest-class RFB facility), sales by main product. https://sumitomoelectric.com/jp/sites/japan/files/2026-10/download_documents/integratedreport2026.pdf
- Sumitomo Electric Industries Redox flow battery (product information), in Japanese. How it works, topics. https://sumitomoelectric.com/jp/products/redox
- Sumitomo Electric Industries Redox flow battery features (product information), in Japanese. Safety, environment, life, design freedom. https://sumitomoelectric.com/jp/products/redox/features
- Sumitomo Electric Industries Redox flow battery case studies (product information), in Japanese. Installations in Japan, the US, Europe, Australia and Asia. https://sumitomoelectric.com/jp/products/redox/cases
- Sumitomo Electric Industries Redox flow battery lineup (product information), in Japanese. V40 series specifications. https://sumitomoelectric.com/jp/products/redox/ranges
- Sumitomo Electric Industries Redox flow battery catalogue (September 2026 edition), in Japanese and English. Principle, features and specifications of the V40, comparison with the third generation. https://sumitomoelectric.com/jp/sites/japan/files/2026-09/download_documents/RFB_Catalog202609_JP.pdf
- Sumitomo Electric Industries New redox flow battery V40 series enabling up to 30 years of operation (11 September 2025), in Japanese. https://sumitomoelectric.com/jp/press/2025/09/prs118
- Sumitomo Electric Industries Three redox flow battery projects selected for METI's grid-battery subsidy (10 February 2026), in Japanese. https://sumitomoelectric.com/jp/press/2026/02/prs015
- Sumitomo Electric Industries New domestically made redox flow battery for 30 years of operation, three METI subsidy selections (16 March 2026), in Japanese. https://sumitomoelectric.com/jp/press/2026/03/prs025
- Sumitomo Electric Industries Third redox flow battery adopted at Hokkaido Electric Power Network's Minami-Hayakita Substation (21 April 2026), in Japanese. https://sumitomoelectric.com/jp/press/2026/04/prs040
- Sumitomo Electric Industries Construction of the fourth phase of the redox flow battery starts in Kashiwazaki, Niigata (8 July 2026), in Japanese. https://sumitomoelectric.com/jp/press/2026/07/prs078
- Sumitomo Electric Industries A 2 MW redox flow system added (7 September 2026), in Japanese. https://sumitomoelectric.com/jp/press/2026/09/prs100
- Sumitomo Electric Industries Redox flow battery to contribute to GX at an Australian coal mine (11 November 2025), in Japanese. https://sumitomoelectric.com/jp/press/2025/11/prs153
- Sumitomo Electric Industries Third consecutive year of orders for long-duration redox flow batteries from Kashiwazaki, Niigata (July 2025), in Japanese. https://sumitomoelectric.com/jp/press/2025/07/prs094
- Sumitomo Electric Industries Redox flow battery adopted for Shin-Idemitsu's grid battery (March 2025), in Japanese. https://sumitomoelectric.com/jp/press/2025/03/prs030
- Sumitomo Electric Industries First completion of a redox flow battery in a Kyushu regional microgrid (April 2025), in Japanese. https://sumitomoelectric.com/jp/press/2025/04/prs055
- Sumitomo Electric Industries Start of building a redox flow battery system in the Oki Islands (January 2025), in Japanese. https://sumitomoelectric.com/jp/press/2025/01/prs005
- Sumitomo Electric Industries Redox flow battery contributes to AI-based optimization of renewables at Osaka Metropolitan University (August 2025), in Japanese. https://sumitomoelectric.com/jp/press/2025/08/prs101
- Sumitomo Electric Group magazine "id" Vol. 19, chapter 3: "The long-held wish for a storage battery over 40 years", in Japanese. https://sumitomoelectric.com/jp/id/project/v19/03
- Sumitomo Electric Group magazine "id" Vol. 19, chapter 4: "Grid-side battery for stable power supply: Hokkaido Electric Power Network, Minami-Hayakita Substation", in Japanese. https://sumitomoelectric.com/jp/id/project/v19/04
- Sumitomo Electric Group magazine "id" Vol. 19, chapter 5: "Entering the wholesale electricity market and microgrid demonstration: NEDO project in California", in Japanese. https://sumitomoelectric.com/jp/id/project/v19/05
- Sumitomo Electric Industries Official website (source of the logo), in Japanese. https://sumitomoelectric.com/jp/
14. Claim-to-source audit
| Claim in the article | Category | Source |
|---|---|---|
| Legal name, head office, founding in 1897 and incorporation in 1920, consolidated net sales (¥4,679,789 million to ¥5,110,171 million), ordinary profit, 302,972 employees, R&D of ¥162,858 million and capex of ¥243,183 million | Sourced | Reference 1 https://sumitomoelectric.com/jp/sites/japan/files/2026-06/download_documents/yuuka156.pdf |
| Environment & Energy sales of ¥1,178,780 million, operating profit of ¥90,615 million (increase of ¥11,897 million), orders of ¥494,621 million and backlog of ¥447,060 million, R&D of ¥19,292 million, capex of ¥51,639 million, 12,336 employees, and the one-sentence mention of RFB demonstration operation | Sourced | Reference 1 https://sumitomoelectric.com/jp/sites/japan/files/2026-06/download_documents/yuuka156.pdf |
| Securities code 5802, listing venues, the start of commercial operation of a world-largest-class RFB facility (2022), RFB as a product of Environment & Energy, "winning large projects" as a policy, and no RFB entry in sales by main product | Sourced | Reference 2 https://sumitomoelectric.com/jp/sites/japan/files/2026-10/download_documents/integratedreport2026.pdf |
| How the RFB works, topics (September 2026) | Sourced | Reference 3 https://sumitomoelectric.com/jp/products/redox |
| RFB features (non-flammable, UL1973, 20-year system durability, design freedom) | Sourced | Reference 4 https://sumitomoelectric.com/jp/products/redox/features |
| Case studies (Hokkaido Electric Power Network, SDG&E, ITRI, Energy Queensland, John Cockerill, Minamikyushu, Kashiwazaki, Nippon PS) with scale and dates | Sourced | Reference 5 https://sumitomoelectric.com/jp/products/redox/cases |
| V40 series specifications (8, 12 and 16 MWh; module configuration; JC-STAR 1 star; duration extendable) | Sourced | Reference 6 and 7 https://sumitomoelectric.com/jp/products/redox/ranges https://sumitomoelectric.com/jp/sites/japan/files/2026-09/download_documents/RFB_Catalog202609_JP.pdf |
| V40 energy density +15% and cost -30% (against the third generation), 30-year operation, recycling of electrolyte and parts, wide-area certification | Sourced | Reference 7 https://sumitomoelectric.com/jp/sites/japan/files/2026-09/download_documents/RFB_Catalog202609_JP.pdf |
| V40 unveiled (September 2025), up to 30 years against 20 years before, about 30% more output, orders planned from January 2026 | Sourced | Reference 8 https://sumitomoelectric.com/jp/press/2025/09/prs118 |
| Three projects selected for METI's subsidy (February 2026: RS Technologies; Sumitomo Mitsui Finance & Leasing with Miki Kogyo; RYODEN with Japan Energy Total System) | Sourced | Reference 9 https://sumitomoelectric.com/jp/press/2026/02/prs015 |
| Orders for the V40 begin, 26 MWh across three projects selected under the subsidy (March 2026) | Sourced | Reference 10 https://sumitomoelectric.com/jp/press/2026/03/prs025 |
| Third Hokkaido Electric Power Network project (33,000 kWh, completion target end of May 2029, contract to 2049) and past deliveries (15,000 kW/60,000 kWh; 17,000 kW/51,000 kWh) | Sourced | Reference 11 https://sumitomoelectric.com/jp/press/2026/04/prs040 |
| Kashiwazaki phase 4 construction start (July 2026), total capacity of 32,000 kWh, spring 2027 target | Sourced | Reference 12 https://sumitomoelectric.com/jp/press/2026/07/prs078 |
| The 2 MW system added (September 2026), adoption in the long-term decarbonization power source auction and subsidy projects | Sourced | Reference 13 https://sumitomoelectric.com/jp/press/2026/09/prs100 |
| Supply to the Boggabri mine (2 MW x 6.3 hours), Vecco Group electrolyte, absence of ignitable materials valued | Sourced | Reference 14 https://sumitomoelectric.com/jp/press/2025/11/prs153 |
| Kashiwazaki phases 1 and 2 completed, phase 3 planned for spring 2026 | Sourced | Reference 15 https://sumitomoelectric.com/jp/press/2025/07/prs094 |
| Shin-Idemitsu Nagasu storage station (2,000 kW x 4 hours, completion planned October 2026, the first RFB selected for the subsidy) | Sourced | Reference 16 https://sumitomoelectric.com/jp/press/2025/03/prs030 |
| Minamikyushu project (250 kW x 4.5 hours, 1,125 kWh, the first RFB under a Ministry of the Environment subsidy) | Sourced | Reference 17 https://sumitomoelectric.com/jp/press/2025/04/prs055 |
| Ama town in the Oki Islands (final scale 4,000 kW and 12,500 kWh, Ministry of the Environment subsidy, industrial waste at removal below 1%) | Sourced | Reference 18 https://sumitomoelectric.com/jp/press/2025/01/prs005 |
| Delivery to Osaka Metropolitan University and the demonstration in tie-up with Kansai Electric's control system | Sourced | Reference 19 https://sumitomoelectric.com/jp/press/2025/08/prs101 |
| Development began in 1982, joint R&D with Kansai Electric Power, the 1989 prototype, switch to vanadium, delivery from 2001, the 2005 withdrawal decision, the 2009 revival, the 2012 1,000 kW-class test system, price as the challenge, and the electrolyte development policy | Sourced | Reference 20 https://sumitomoelectric.com/jp/id/project/v19/03 |
| The Hokkaido Electric Power Network tender (2019 call, July 2020 start of construction, 31 March 2022 completion) and 17,000 kW x 3 hours | Sourced | Reference 21 https://sumitomoelectric.com/jp/id/project/v19/04 |
| NEDO's California demonstration (about ¥3.0 billion, over 7 years), entry into the wholesale market, and microgrid operation (2021) | Sourced | Reference 22 https://sumitomoelectric.com/jp/id/project/v19/05 |
| RFB-only sales, profit, order backlog, production capacity, cumulative installed base and price, measured performance of the V40, state of the new electrolyte, and subsidy amounts | Not yet confirmed | References 1, 2, 3, 7 https://sumitomoelectric.com/jp/sites/japan/files/2026-06/download_documents/yuuka156.pdf https://sumitomoelectric.com/jp/sites/japan/files/2026-10/download_documents/integratedreport2026.pdf https://sumitomoelectric.com/jp/products/redox https://sumitomoelectric.com/jp/sites/japan/files/2026-09/download_documents/RFB_Catalog202609_JP.pdf |
| The four-type classification and Sumitomo Electric's position (primary: long-duration & new chemistries, secondary: storage systems) | Our calculation | Our own classification; company names are examples from those covered in this series |
| Environment & Energy operating profit of ¥78,718 million for the year to March 2025 | Our calculation | Our own calculation: ¥90,615 million less the ¥11,897 million increase |
| Longer operating period (30 years) aimed at lowering bid prices | Sourced | References 8 and 10 https://sumitomoelectric.com/jp/press/2025/09/prs118 https://sumitomoelectric.com/jp/press/2026/03/prs025 |
| The reading that selling is widening to contracts including long-term maintenance and operation | Inference | Our own reading of the third Hokkaido contract and the sale of operating software |
| The reading that it is relying strongly on subsidy programmes | Inference | Our own reading of the number of selected projects; the programmes themselves have not been checked against government sources |
| The reading that the present "30 years" emphasis reflects the experience of past failure | Inference | Our own reading of the magazine's account of the main theme after the revival |
| That vanadium is thought to be a large part of the cost, and that electrolyte price and cell-stack output affect system price (general points) | Our calculation | This is our own general commentary and not a breakdown published by Sumitomo Electric |
| Content and stage of subsidies and regulations | Not yet confirmed | This article has not checked these against government or regulatory sources and keeps to the company's own statements |
Last updated 10 October 2026 / Troy Technical
Figures in this article come from Sumitomo Electric's Securities Report, Integrated Report, official product pages and catalogue, official releases and company magazine. No research-firm estimates or press-reported figures have been used. Performance values are the company's statements, and values without stated conditions are not measurements. Items marked "Inference" are our reading of the primary sources and are not statements by the company. The company's plans and targets are not yet confirmed and are not results achieved.