Most conversations about energy storage focus on a single question: How long can you discharge energy once the system is operating?

That question matters — but it’s only half the story.

The other half is quieter, less discussed, and increasingly important as we try to decarbonize industry and build reliable, renewables-heavy energy systems:

How long can you store energy between cycles without losing it — and still deliver it at high quality when it’s needed?

A quick tour of the storage landscape

We’re fortunate to have more energy storage options today than ever before.

• Batteries excel at fast response and short-duration applications, but are constrained by electrochemistry, degradation, and self-discharge.
• Pumped hydro remains one of the most effective large-scale storage solutions — where geography allows.
• Thermal energy storage plays an important role for heat, but energy leaks away continuously while the system waits to be used.

Each of these technologies shines in the right context.

But most are implicitly designed for frequent cycling — daily, or even multiple times per day.

For many industrial, remote, and firming applications, that assumption doesn’t hold.

The two time axes of energy storage

There are really two independent dimensions that define any storage system:

1. Duration of discharge How long energy can be delivered once the system is running.
2. Interval between cycles How long energy can sit in storage before it’s needed.

Most discussions fixate on the first. Many real-world applications are constrained by the second.

In industrial and remote settings, energy demand is often irregular. Storage may sit idle for days or weeks before being called upon — and during that waiting period, losses matter just as much as efficiency during discharge.

Why thermochemical energy storage is different

Thermochemical energy storage (TCES) approaches the problem from a different angle.

Instead of storing energy purely as temperature or electrical charge, TCES stores energy in chemical bonds. When those bonds are formed, energy is stored. When they are reversed, energy is released.

The implication is simple but powerful:

Energy can be stored for long periods with essentially no standby losses.

Time becomes decoupled from energy.

This opens up a design space that purely thermal or electrochemical systems don’t have access to — especially when high temperatures, long intervals between cycles, and durability matter.

Thermochemical storage shifts energy storage from temperature alone to chemistry — where energy can wait patiently and be released as heat when needed.

Why iron matters: density, temperature, and practicality

In thermochemical systems, the choice of energy carrier matters enormously.

Iron stands out for several reasons:

• Energy density High energy per unit mass and volume, directly impacting system size, cost, and capital efficiency.
• High-temperature capability Enables applications that require sustained, high-quality heat and efficient power generation.
• Ease of procurement Iron is abundant, widely produced, and deeply embedded in global supply chains — supporting scale, cost predictability, and freedom to operate.
• Safety and simplicity At its core, the chemistry is familiar: iron rusts, and iron oxide is reduced back again. No exotic materials, no unfamiliar failure modes.

These attributes shape not just performance, but how systems get built, permitted, financed, and deployed.

Beyond heat: reliability and optionality in future grids

As grids move toward higher penetrations of renewables, reliability becomes less about fast response and more about firm, controllable energy over longer timescales.

Thermochemical systems are naturally suited to:

• long intervals between cycles,
• peak shifting rather than rapid cycling,
• and integration with power generation or combined heat and power (CHP).

That creates optionality.

The same stored energy can support industrial heat, electricity generation, or both — depending on system needs.

Where my work fits into this picture

This is the problem space I now get to work on at FeX Energy.

Our focus is a thermochemical energy storage approach built around:

• the energy density of iron,
• solid-state operation,
• high-temperature output,
• long intervals between cycles with no standby losses, and
• a design philosophy centered on simplicity, safety, ease of procurement, and de-risking.

I won’t get into implementation details here. What drew me to this work is that it sits at the intersection of chemistry, thermodynamics, and real-world deployment constraints — not just what works in theory, but what can scale responsibly.

Closing thought

Energy storage isn’t just about how long you can discharge.

It’s about how patiently energy can wait — and still show up, intact and useful, when it’s finally needed, whether that’s as heat, power, or both.

That’s the lens through which I now look at the storage landscape — and why thermochemical energy storage, particularly iron-based systems, is such an exciting space to be working in.

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More to come.