A Demi & Jimmy explainer
Where does the
cold come from?
A trick question — answered by a drop of water and a speck of heat. Spoiler: nobody makes cold.
Let's find out ↓
A trick question — answered by a drop of water and a speck of heat. Spoiler: nobody makes cold.
Let's find out ↓
Hi! I'm heat — a real little guy. "Cold" isn't a thing you can hold. It's just… me, somewhere else. The fewer of us hanging around, the cooler it feels. That's the whole secret.
"Cooling" never means creating cold — there's no such substance. It always means moving heat energy from where you don't want it to somewhere else. A fridge pumps heat out its back; an air conditioner dumps it outdoors. Temperature is just how much heat is present.
I'm a drop of water in a sealed loop — a pipe that goes in a big circle, round and round, all day. I don't get used up. I just carry heat from one place to another and come back for the next load. Heat needs a ride; I'm the ride.
She's the bus. I'm the passenger. Couldn't get anywhere without her!
Water is the heat-transfer fluid. It circulates through a closed pipe loop, picking up heat at one end and releasing it at the other, indefinitely. The same water is reused — nothing is consumed but the warmth it carries.
The water that cooled the computers stays on its side. Demi's clean greenhouse water stays on hers. The only thing that ever crosses between them is Jimmy — the heat.
The two loops meet at a plate heat exchanger — a stack of thin steel plates with hot water in every other gap and the greenhouse's water in the gaps between. Heat conducts straight through the steel; the two waters share a huge surface but never touch. It's mature, off-the-shelf equipment — breweries, ships, and hospitals all use it. The novel part is the system around it, which a thermal engineer sizes and tunes.
I carry Jimmy next door to the greenhouse and trickle along the garden beds — like a radiator in a cozy old house. Bit by bit, Jimmy's warmth soaks into the air and the roots.
And that's where I go! Right into the plants. I become a winter strawberry. 🍓 Best ending a joule could ask for — way better than floating off into the sky.
Warm water runs hydronic pipes along the beds, tuned to roughly 28 °C / 82 °F — exactly the warmth a winter greenhouse wants. The heat ends up in the growing environment; the crops drink their own separate, clean irrigation water. The energy "goes" into food and a livable climate, then the cooled water loops back for more.
Here's the answer to the trick question. The data center makes way more Jimmys than the farm could ever use. So every Jimmy reaches a fork:
The farm grabs the heat it can use and turns it into strawberries, turmeric & ginger, mushrooms, oranges — all winter.
Up through the data center's chillers and into the sky — exactly where all of it went before we showed up.
Nobody made cold. The water turns "cool" simply because I left. The chillers are still the boss of the building's temperature — we just gave a few of us a job before the rest clock out.
The worst day for the data center is a totally normal day. We can only ever make its job easier.
The greenhouse is a supplemental heat sink, never a dependency. It captures a slice of the rejected heat; the chiller plant still rejects the remainder to the atmosphere exactly as it does today, and always sets final temperatures. If the farm is full or offline, a bypass sends the heat straight to the chillers — the building cools unchanged. Returning slightly cooler water can even lighten the chillers' load a touch. How much heat is captured and at what temperatures are engineering figures set by the heat-load model — illustrative until then.
The real one is where does the heat go? — and now some of it grows the town's food all winter, using only the warmth the building was already throwing away.