Sci-Fi Thermal Batteries: A Cheaper Alternative to Natural Gas?

A Novel Approach to Long-Duration Energy Storage

Fourth Power is developing a unique long-duration energy storage system, reminiscent of advanced technology seen in fictional espionage. Their innovative thermal batteries utilize superheated liquid tin and are contained within hermetically sealed chambers filled with argon gas.

However, the company’s objective is decidedly practical: to provide electricity storage at a price point that makes solar and wind power consistently viable options for round-the-clock energy needs.

How the Technology Functions

The process begins with electricity from the power grid being used to heat carbon blocks situated inside insulated chambers containing argon gas, effectively storing energy.

When energy is required, molten tin, heated to an extreme 2,400°C (4,352°F), is circulated through graphite pipes – the only material proven cost-effective for withstanding such intense temperatures.

This heat is then converted back into electricity using specialized devices known as “thermophotovoltaic cells.” These cells function similarly to solar panels, capturing the infrared light emitted by the intensely hot tin.

Development and Future Plans

For the past two years, the Cambridge, Massachusetts-based startup, founded four years ago, has been focused on refining this technology.

Currently, they are preparing to construct their first full-scale battery, incorporating the molten tin and all associated components.

Fourth Power anticipates delivering commercial-scale batteries to customers by 2028, with a projected cost that could be lower than both lithium-ion batteries and power generated by peaking natural-gas plants.

“We project that our initial offerings will be cost competitive,” stated Arvin Ganesan, co-founder and CEO of Fourth Power, in an interview with TechCrunch. “The potential within these markets is substantial.”

Operational Characteristics and Efficiency

The envisioned operation involves daily charging and discharging cycles, providing a consistent electricity supply for approximately eight hours or longer.

This duration is double that of most existing grid-scale lithium-ion battery systems.

The insulation, composed of petroleum coke (a byproduct of oil refining), maintains remarkably stable temperatures, resulting in a minimal energy loss of only 1% per day.

Extensive testing is currently underway on smaller-scale versions of the system. “We are conducting cycles to validate power output and confirm the system’s long-term durability,” Ganesan explained.

Funding and Expansion

Alongside these tests, the company is designing a 1-megawatt-hour demonstration battery.

To finance this project, Fourth Power has secured $20 million in a Series A Plus funding round, as exclusively reported to TechCrunch.

Munich Re Ventures led the round, with participation from Breakthrough Energy Ventures and DCVC. Previously, the startup raised $19 million in a Series A round in 2023.

Cost Projections and Supply Chain Advantages

Fourth Power’s ultimate goal is to reduce the cost of electricity storage using their thermal batteries to $25 per kilowatt-hour, representing one-tenth the cost of lithium-ion technology.

“The system’s simplicity, with few components and a limited number of suppliers, allows for a direct path to achieving our cost targets,” Ganesan noted. “We believe the $25 target is realistically attainable.”