The global transition to renewable energy is at a critical juncture. Given the intermittent nature of energy produced by solar and wind, it is essential to incorporate energy storage solutions to unlock their full potential. The need for robust, long-duration energy storage (LDES) has never been more urgent. 

Markets such as the US, EU, and Australia have driven renewable energy penetration to exceed 30–40%, leading to a pressing concern about grid instability. Once renewables exceed 60–70% of the grid mix, LDES isn’t just helpful—it’s mandatory for efficient and stable power delivery. 

Yet today, 50–70 TWh of wind and solar energy is wasted annually due to curtailment, representing a multi-billion-dollar opportunity for storage solutions that can capture and shift this surplus.

Regions with high wind (e.g., Northern Europe, Canada) see surpluses in winter but shortages in summer. Solar-rich areas (Southern Europe, US Southwest) overproduce in summer. This seasonal mismatch can only be addressed by storage solutions capable of holding energy for weeks or months, not just hours.

Governments worldwide are now mandating grid storage deployments, with LDES market projections exceeding $50 billion by 2030. At the same time, the cost of battery storage has plummeted by 89% since 2010, making it increasingly competitive with traditional gas peaker plants, which are themselves under pressure from high costs, emissions, and policy-driven phaseouts.

Why Existing Technologies Fall Short

Today, most grid-scale storage systems are short-term, typically lasting four to six hours. Lithium-ion batteries dominate this segment, serving well for daily balancing or frequency regulation. But they fall short on multiple fronts when it comes to long-duration applications:

• High cost per kilowatt-hour when scaled to multi-day or seasonal use
• Safety risks associated with thermal runaway necessitate the use of fire suppression systems
• Heavy dependence on critical minerals like lithium, cobalt, and graphite, mostly refined or controlled by China

Flow batteries offer some promise by separating power and energy components, but they face low round-trip efficiency, expensive membranes, and technical complexity that limits scalability. They are also still expensive at scale and best suited for durations under 24 hours.

So what about non-electrochemical options? 

Pumped hydro is the most mature form of seasonal storage, but it’s geographically constrained and involves huge infrastructure. Thermal storage is promising for industrial heat but less so for grid electricity. Gravity-based storage systems are still in early stages and require specialized sites. None of these are modular, easy to site, or suitable for distributed deployment.

In short, while these legacy options can help, they don’t meet the growing demand for distributed, scalable, and dispatchable energy storage that works across seasons and geographies. Electrochemical solutions are necessary for true flexibility and scalability, but even these options have drawbacks.

Sthyr Energy: A Unique Indian Solution

Our search for a true LDES breakthrough led us to three remarkable founders at IIT Madras. Gunjan, Akhil, and Hamdan—all PhDs in electrochemistry—had been working for years on a problem that most startups don’t dare touch: how to build a battery that can store clean energy for weeks or even months, safely and affordably. They were not just experimenting in the lab. They had built an operational prototype, secured patents, published in top journals, and begun conversations with industrial partners. Their goal wasn’t just to publish—it was to commercialize.

At the heart of Sthyr’s system is a mechanically rechargeable zinc-air battery architecture. Unlike conventional batteries, which charge and discharge in the same unit, Sthyr separates the two processes. This decoupling does three important things:

1. Enables continuous cycling – while one stack discharges, another can charge in parallel.
2. Prevents dendrite formation – a major cause of failure in zinc-based systems.
3. Allows independent scaling of energy and power – helps drive down cost per kWh.

Their system is modular, meaning it can be deployed at both microgrid and utility scales. It’s based on air, water, and zinc—all of which are abundantly available in India. Their electrolyte is aqueous and non-flammable, making it far safer than lithium-ion. Unlike other zinc-air approaches that suffer from clogging and passivation, they’ve built a flowing electrolyte system that avoids these common degradation pathways.

With deep expertise in electrochemistry and materials science, they are building something unique: a rechargeable zinc-air battery system designed for storing energy for many months, unlocking the true potential of long-duration and seasonal storage.

What impressed us beyond the technology was their thoughtfulness on commercialization. The team had secured over $650,000 in non-equity grants from India’s Ministry of Mines and Department of Science & Technology. They had letters of intent from prominent industry players. They have clear pilot milestones: a 300 kWh / 10 kW system is to be deployed soon, and plans are in place to scale to 10 MWh per annum thereafter.

Gunjan, who leads the commercial effort, is a serial entrepreneur and has previously set up complex renewable projects. Akhil and Hamdan bring deep R&D execution strength. As a team, they are grounded, self-aware, and resilient. They are not chasing trends. They are building for the long haul.

Sthyr is not just building a better battery. They are building a missing link in the energy transition. A system that:

• Stores excess solar in summer and releases it in winter.
  
• Helps wind-heavy grids, such as those in Germany or Tamil Nadu, avoid curtailment.
  
• Replaces gas peaker plants with a zero-emissions alternative.
  
• Reduces dependence on geopolitically sensitive materials.

The Road Ahead

Our investment in Sthyr Energy is rooted in a clear vision: enabling a future where clean energy is not only abundant but also reliably available, day and night, throughout the seasons.

The clean energy transition cannot succeed without reliable, scalable, and cost-effective long-duration storage. Sthyr Energy’s zinc-air solution addresses the core challenges of seasonal storage, supply chain security, and economic viability. We are excited to back this pioneering team as they build the backbone for tomorrow’s resilient, renewable-powered grids. 

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Founded in 2017 by visionary leaders Vishesh Rajaram and Arjun Rao, Speciale Invest is a seed-stage venture capital firm dedicated to empowering deep tech founders who tackle complex global challenges. With a commitment to investing at the pre-seed and seed stages, the firm focuses on five transformative themes such as 

1. Energy transition and planetary health – innovations in batteries, hydrogen, and materials
2. Advanced manufacturing and industrial modernization – advancements in robotics and semiconductors
3. Beyond Earth and space technology – frontiers of satellites and launch systems
4. Advanced software and computing – unlocking the potential of AI/ML infrastructure and quantum tech
5. Biosciences, life sciences, and health tech – breakthroughs in synthetic biology, bioengineering, biomedical, and life sciences

By merging capital with profound technical and strategic support, Speciale Invest is on a mission to nurture and elevate globally relevant companies that emerge from India.

If you are building something exciting in deeptech/ deepscience, please do write to us at info@specialeinvest.com 

To know more about Speciale’s investments in disruptive technologies, please check our portfolio. 

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