A car wash in Germany

A car wash is an unusually good place for surplus mining. Above the wash bays, 150 kWp sit on a canopy – translucent modules that give shade in summer and let enough light through in winter. Underneath runs a business that needs two things at once: electricity and hot water. That is exactly what the system delivers.

Eleven miners are connected to a single MINEOMATBOX PRO: six S19 XP+ Hydro, two S21e Hydro, two Whatsminer M53 Hydro – and one Avalon Q, the only air-cooled unit. Four device types from three manufacturers, industrial hydro technology next to a small home device, all on one controller. Plus a 50 kWh battery.

The interesting part is not the size but the daily routine. In the morning, not a single miner is running. As soon as the sun delivers more than the business needs at that moment, the box starts the first one. If the surplus is enough for the next, the next one joins – device by device, spread across the morning. In the afternoon it runs in reverse: miner by miner goes back to standby until, in the evening, they have all stopped again. Nobody sits next to it flipping switches. The box decides afresh every 30 seconds, based on solar production, the business’s consumption, battery level and spot price.

Because ten of the eleven devices are water-cooled, their waste heat is not lost as hot air but goes into the water: around 40 °C flows into the miners, around 49 °C comes back out. The car wash needs this heat anyway – for the wash water in summer, for the heated wash bays in winter. Electricity that would otherwise have gone into the grid for a few cents thus becomes two things at once: Bitcoin and process heat.

How well this works is shown by the figures since commissioning on 10 August: the eleven miners take in almost twice as much electricity as the business the system was built for in the first place – the numbers are just below.