Issue #16 — Exowatt

Every time you ask ChatGPT, Claude, Gemini, or Manus (for all you big-time AI nerds, myself included) to make a meme of your friend, a data center sucks electricity to power your entire neighborhood. AI isn't just hungry. Not even "Joey Chestnut on the 4th of July" hungry. Hungry like it’s about to eat the entire US power grid for breakfast and come back for more.

Enter Exowatt. A Miami startup that's raised $140 million to power AI data centers with clean, dirt-cheap, around-the-clock energy. Their technology of choice? Not nuclear. Not fusion. Not some exotic battery breakthrough.

Rocks. Hot ones in a box.

I’m not kidding either. The industry's actual nickname for this technology is "rocks in a box." Hundreds of thousands of years ago, humans figured out that rocks near a fire stay warm all night. Hell, Luke from Outdoor Boys taught me the same thing — heat some rocks and bury them where you’re sleeping and you’ll stay warm til morning (if you've never watched Outdoor Boys, pop it on a late Friday night. You'll never solo camp in interior Alaska in January, but my god, you’ll watch this former lawyer do it for hours. Grant & Ben — should we take our Wednesday meeting from interior Alaska? Think about it.)

BUT I DIGRESS.

We humans invented agriculture, the airplane, the internet, NASCAR, Waffle House, and AI — and it turns out the whole thing can run on caveman technology.

If you've ever sat in the sauna at the gym, you already understand Exowatt. Rocks get hot. Rocks stay hot. And you sweat out the zillion Guinnesses you had last night.

Picture a standard 40-foot shipping container — the kind you'd see stacked on a cargo ship. Now put a giant magnifying glass on top. That's the Exowatt P3.

A lens sits on the roof, tilts to track the sun all day, and concentrates sunlight down into the container. All that concentrated sunlight cooks an engineered brick inside to as hot as 1,000°C. That brick is the battery. When you need electricity, air flows over the hot brick and the heat drives a piston engine that generates power.

Exowatt says one charged-up box can dispatch energy around the clock, and the bricks hold their heat for days. Cloudy week? Backup electric coils inside can heat the bricks — basically toaster technology.

No lithium. No cobalt. No rare earth minerals from a supply chain held together by hope and geopolitics.

And none of it is new technology. The engine was invented in the 1800s. The lens is from a lighthouse. The brick is engineered from silicon. A magnifying glass, a rock, and a basic engine — that's the machine Silicon Valley is throwing money at. Exowatt's only invention is making it small and stackable. Need more power? Add more boxes. Practically a big Lego set for the power grid.

The problem with how we power things today

Two reasons nobody's solved this yet. Exowatt is built around both.

One: There's a big line to plug into the grid. Building a data center can take ~18 months. That's the easy part. Plugging it in, however, is a nightmare. The wait to connect to the US grid has gone from under two years in 2008 to roughly five today, and on the East Coast, closer to eight. Some companies have quit waiting. xAI's Memphis supercomputer just rolled in 35 gas turbines and built its own power plant in the parking lot. Like the world's most expensive tailgate.

Two: Solar and wind are cheap, but the sun isn’t around 24 hrs a day. Panels have gotten dirt cheap — that part worked. Problem is they only make power when the weather cooperates, which isn’t really at night when everyone's home and cranking the AC. So you bolt on massive lithium batteries to save the daytime juice. Those are expensive, use minerals mostly from foreign nations, and degrade over time — like your iPhone battery. The generation is cheap. But the storage is killer.

Exowatt's trick? The box does both. Generator and battery in one shipping container. Sun charges the brick by day, and you pull out power whenever — no lithium farm, no grid connection, no eight-year line. You don't wait to plug in because you never plug in. Drop the boxes in the sun and go.

Hannan Happi’s resume reads like someone speed-running every hard-tech name worth having. Combustion engine research, then a year at GE, a year at Siemens, a stint consulting at Accenture, then a year at Tesla. By his early 30s, he'd touched engines, power, cars, and consulting — like he was collecting infinity stones.

Then he actually built something. In 2015 he co-founded Volansi, a long-range delivery drone startup — took it through Y Combinator, raised tens of millions from investors like Lightspeed, and grew it to 150 people before moving on.

Engines, power, cars, drones, and now rocks. The man has spent his whole career circling hard physical problems.

In late 2022 he landed at Atomic, the Miami venture studio, to take on the AI power crisis. He and his team went through more than 50 designs before settling on the P3. Fifty versions of a hot box. That’s a man and a team on a mission.

Concentrated solar power is a graveyard. Giant mirror-field projects have been flaming out for decades — over budget, underperforming, one famously incinerating birds mid-flight (not in the "we're saving the world" brochure).

Exowatt's counter is that everyone before them built massive one-off projects, while their answer is mass production. Only about 100 concentrated solar projects have ever been built on Earth. We make 1.5 billion solar panels a year. Panels got cheap because of that learning curve, and Exowatt wants to put bricks on the same one. To hit one cent per kilowatt-hour, they need to manufacture a million units a year. So far they've built a handful. That's a factory problem, not a science problem — but factory problems have killed plenty of companies too.

Also, this thing needs sun. A lot of it. A Southwest desert product, not an Ohio-in-February product (no offense, Ohio).

One cent per kilowatt-hour is about 90% cheaper than grid power today. At that price, energy stops being a bill you pay and starts being a thing you assume — like Wi-Fi at a coffee shop or a hot dog on the 4th of July. The cost of water, food, and just about everything made in a factory falls with it.

We (humans) started this whole thing ~350,000 years ago, huddled around hot rocks to not freeze at night. Now the most advanced civilization in history is huddling around hot rocks again — except this time they fit in a shipping container and they're trying to power the machines that might think for us.

Exowatt is hiring in Miami — engineers, manufacturing folks, and anyone who's ever stared into a campfire and thought "there's a business in here somewhere." The sauna is the office. The office is the sauna.

Open roles → exowatt.com/careers

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