Roughly $64 billion in US data center projects have been blocked or delayed by the people next door, most often over water draw and grid load. Hockema Group Inc., a Seattle naval architecture firm, has drawn the workaround as a hull. The concept is a 340 by 105 foot barge with an 18 foot draft, carrying 20,000 square feet of data floor forward and 25MW of onboard generation aft, according to WorkBoat's coverage. Eric Blumhagen, senior principal naval architect at Hockema, said: "Data centers are expanding on land, and in many cases, they're burning their bridges." Estimated cost runs $80 million to $100 million before processing units. The stern holds diesel generators or gas turbines and 340,000 gallons of fuel, wrapped in hospital-grade exhaust silencers and extra insulation. The bow holds server cabinets roughly three feet wide by four feet long, standing six to ten feet.
Hockema specifies evaporative cooling towers plus waste heat reclamation off the chip cooling loop. A tower concentrates whatever is dissolved in its makeup water, because the water leaves as vapor and the solids stay behind. Run harbor water through it and the fill scales, the basin fouls, and the approach degrades within a handful of cycles. Makeup therefore comes from shore or from onboard treatment, which puts back the shore dependency the concept was drawn to escape, and adds biocide dosing and a blowdown stream that has to go somewhere in a working harbor. Nautilus Data Technologies avoided all of it in Stockton by using river water as the outside loop and claiming zero consumptive use, meaning no evaporative loss. That system still withdraws river water and discharges it warmer. Direct harbor or river rejection carries its own bill: salinity, biofouling, and suspended solids force titanium plate heat exchangers, filtration, and a cleaning regime a closed tower loop never needs. Seawater can cool data centers, and most operators still have not worked out how to use it.
Nautilus commissioned Stockton in 2021 at 6.5MW of critical IT load across four data halls in 20,000 square feet, Tier III classification, rack densities around 55kW. It listed the asset at $45 million in November 2024 at 86 percent leased with 5.58MW occupied, offering to keep a 15 percent stake and operate it for the buyer. That works out to about 325 watts per square foot of data floor. Hockema's 25MW is gross onboard generation, so at a plausible PUE of 1.2 to 1.4 the IT load lands somewhere between 18MW and 21MW on the same 20,000 square feet, call it 950 watts per square foot. Three times the density of the only floating data center the US has operated, and the cooling architecture doing that work is a tower loop rather than the once-through river loop Nautilus used. Hailanyun put 2,000 servers on the seabed behind an offshore wind farm and posted a PUE below 1.15, rejecting straight to seawater with no tower anywhere in the design.
At 25MW, large diesel gensets burn on the order of 1,300 to 1,700 gallons an hour. Against 340,000 gallons of bunkerage, that is roughly eight to eleven days at full load before a bunker barge has to come alongside. The concept trades a utility interconnect queue for a fuel logistics chain and an air permit, and air permits for a moored generating asset come from state and regional air quality agencies and the EPA rather than from the port. Thermal discharge and ballast water sit under separate rules again. Community opposition to a 25MW diesel plant in a harbor is not obviously smaller than opposition to a 25MW data center in a county.
The version of this that gets built rejects heat to the water it floats on. Towers on a hull ask an operator to accept a shore water contract, a blowdown permit, and a scaling risk, in exchange for avoiding titanium heat exchangers. That trade only works in a port with cheap fresh water and no discharge scrutiny, which is a short list. Anyone taking this to a shipyard should price the once-through variant first and ask for tower approach and capacity at the ASHRAE 0.4 percent design wet bulb for the specific port, around 26.5C for Houston or New Orleans, not at an annual average. Wet bulb does not care that the box floats.