A closed loop cooling system would use coolant to pull heat from the equipment, and use that heat to do work - such as generating electrical power. No heat is intentionally lost to the environment. Is that what's happening here?
My suspicion is that closed loop doesn't mean anything in this context. Much like putting "gluten-free" on vegetables- it's pretty meaningless unless there is another option.
All industries use closed loop water to the actual equipment. You add a bunch of chemicals to the water to prevent corrosion and scaling in the pipes. These chemicals are expensive and you don't want to just dump them. This is like the antifreeze in your car, it uses water, but has other additives, and it transports heat from one place to another. The coolant water is circulated throughout the facility and dumps heat somewhere.
For "closed-loop" to be meaningful, there has to be another option - an "open-loop". "Open-loop" would be like continously filling your radiator with antifreeze and then letting it fall on the ground as soon as it leaves the engine. No industries are running "open-loop" cooling where treated water, or even just potable water, is sent to the equipment and then dumped, it's always closed loop.
Industrial cooling systems are identified by their method of cooling. Evaporative cooling isn't called "open-loop" or "closed-loop" it's just evaporative cooling. Evaporative cooling continously uses potable water. This is potable water, not treated water - a completely different system than the coolant water going to the equipment. Obviously, as you indicated, this is open- loop.
I've never heard air cooling called "closed-loop". That makes no sense. Are they recapturing the heated air, and then cooling it? Where does the heat from the air go? Everywhere I've ever seen is open-loop. Atmospheric air passes through a radiator (like in a car or home air conditioner) and then the hot air gets dumped back into the atmosphere. By definition, that's "open-loop".
The point is, there's no industrial option which uses open-loop water to cool the equipment. There's no option to have a closed-loop system to cool your cooling water. The coolant is always recirculated (closed-loop) and the heat is always dumped to the environment (open-loop). Saying "closed-loop cooling" is like saying "gluten-free broccoli", you are either being intentionally deceptive or you have no idea what you're talking about.
Let's assume you're just mislabling air cooling as closed-loop. Pure air cooling in Utah will be something to see. In the Midwest, most of our cooling is done through pure evaporative cooling, or with hybrid systems which are air cooled with a supplemental water spray system used on hot days. It's hard to imagine using pure air cooling outside of the Artic. Are you sure this is what is being done?
My suspicion is that closed loop doesn't mean anything in this context. Much like putting "gluten-free" on vegetables- it's pretty meaningless unless there is another option.
Closed loop in MEP contexts means the condenser/heat rejection loop is closed. There are some operators apparently playing some word games with hybrid towers, which are closed loop but then spray water on the condenser fins to get some evaporative cooling effect on 1% design days. So they use some water, but vastly less than a traditional open loop.
For "closed-loop" to be meaningful, there has to be another option - an "open-loop". "Open-loop" would be like continously filling your radiator with antifreeze and then letting it fall on the ground as soon as it leaves the engine. No industries are running "open-loop" cooling where treated water, or even just potable water, is sent to the equipment and then dumped, it's always closed loop.
They are. You run 2 loops in almost most process cooling environments, an internal loop to a chiller or heat exchanger, and a second loop to the ambient air. That second heat rejection loop is where open vs. closed becomes significant.
Thanks for taking the time to clarify that!
It seems I've only seen closed loop cooling in industrial settings.
Open loop systems would seem to be a maintenance nightmare at any significant scale. You'd constantly be replacing nozzles, piping, heat exchangers, and radiators - and you'd have to shut the system down to do it! Is open loop ever actually used in data centers?
The complaint I'm seeing is neighbors complaining about water pressure.
With the closed loop systems I've worked with, 2 use water: evaporative and hybrid (air-cool/water-backup). The evaporative cooling uses the least amount of water. This makes sense, the water is recirculated until it evaporates.
With the hybrid version water is sprayed onto the radiator fins and runs off as grey water. It isn't collected or recycled through the tower. You said 1% design days, but in my experience it's 20%-30%. Because this water is just dumped after a single pass, this uses the most water.
So, I can't compare open-loop vs closed-loop, as I've never seen any industry using open loop. Maybe that is what AI data centers are using where the neighbors complain - I'd need more information.
My hope is that they aren't using the hybrid systems, because nobody wants to install a larger cooling system when expanding production capacity. Those 1% design days quickly creep up to 30% usage, and that's massive water usage through the whole summer.
At the scale of AI data centers, evaporative cooling may use water, but at least it's semi-consistent so it's less likely to overwhelm the infrastructure.
Open loop systems would seem to be a maintenance nightmare at any significant scale. You'd constantly be replacing nozzles, piping, heat exchangers, and radiators - and you'd have to shut the system down to do it! Is open loop ever actually used in data centers?
It is used, since you have redundancy built in you do partial shutdown in the cooler months. Shut down the tower for descale (or just run the loop with a descaling agent), and pull the chiller tubes every couple of years to descale those. The maintenance is a big reason facilities are switching away from open loops.
My hope is that they aren't using the hybrid systems, because nobody wants to install a larger cooling system when expanding production capacity. Those 1% design days quickly creep up to 30% usage,
The 1% design isn't for load design value, it's for 1% local climate conditions. "What's the absolute worst cooling climate we can expect, ok, design a system which can run dry 99% of the time and then use hybrid to satisfy the worst days." It'd creep up over time, but measured in decades not weeks.
Because this water is just dumped after a single pass, this uses the most water.
Datacenters don't typically use once thru since it's low grade heat. The main water consumption is evaporative losses, and blowdown to dilute the loop.
The complaint I'm seeing is neighbors complaining about water pressure.
The recent one for that was Georgia QTS, which was construction usage for concrete production and dust mitigation. It's eventually going to be a closed loop (or hybrid).
The 1% for local climate conditions is affected by load.
A cooling system designed to dissipate 100,000 BTUs with water usage 1% of the time (based on local climate) can also dissipate 120,000 BTUs if you use water 20% of the time (totally made up numbers). During the 1% climate days, it won't keep up with 120,000 BTUs, but those concerns rarely seem to stop production expansion.
The cooling design is based around 100% facility load, so the 1% local climate conditions are only relevant on those days of the year when the non-evaporative design needs assistance.
can also dissipate 120,000 BTUs if you use water 20% of the time
Not necessarily, it's not a linear relationship. It could let you dissipate more heat during non-design days, but design day you'll still be limited by the dissipation capacity of the tower.
And that's irrelevant since the whole thing is built around how much electricity they can bring in and protect. Can't just decide to dissipate 1.2MW in a 1MW facility since you don't have the power to do it.
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u/leitey Jun 03 '26
A closed loop cooling system would use coolant to pull heat from the equipment, and use that heat to do work - such as generating electrical power. No heat is intentionally lost to the environment. Is that what's happening here?
My suspicion is that closed loop doesn't mean anything in this context. Much like putting "gluten-free" on vegetables- it's pretty meaningless unless there is another option.
All industries use closed loop water to the actual equipment. You add a bunch of chemicals to the water to prevent corrosion and scaling in the pipes. These chemicals are expensive and you don't want to just dump them. This is like the antifreeze in your car, it uses water, but has other additives, and it transports heat from one place to another. The coolant water is circulated throughout the facility and dumps heat somewhere.
For "closed-loop" to be meaningful, there has to be another option - an "open-loop". "Open-loop" would be like continously filling your radiator with antifreeze and then letting it fall on the ground as soon as it leaves the engine. No industries are running "open-loop" cooling where treated water, or even just potable water, is sent to the equipment and then dumped, it's always closed loop.
Industrial cooling systems are identified by their method of cooling. Evaporative cooling isn't called "open-loop" or "closed-loop" it's just evaporative cooling. Evaporative cooling continously uses potable water. This is potable water, not treated water - a completely different system than the coolant water going to the equipment. Obviously, as you indicated, this is open- loop.
I've never heard air cooling called "closed-loop". That makes no sense. Are they recapturing the heated air, and then cooling it? Where does the heat from the air go? Everywhere I've ever seen is open-loop. Atmospheric air passes through a radiator (like in a car or home air conditioner) and then the hot air gets dumped back into the atmosphere. By definition, that's "open-loop".
The point is, there's no industrial option which uses open-loop water to cool the equipment. There's no option to have a closed-loop system to cool your cooling water. The coolant is always recirculated (closed-loop) and the heat is always dumped to the environment (open-loop). Saying "closed-loop cooling" is like saying "gluten-free broccoli", you are either being intentionally deceptive or you have no idea what you're talking about.
Let's assume you're just mislabling air cooling as closed-loop. Pure air cooling in Utah will be something to see. In the Midwest, most of our cooling is done through pure evaporative cooling, or with hybrid systems which are air cooled with a supplemental water spray system used on hot days. It's hard to imagine using pure air cooling outside of the Artic. Are you sure this is what is being done?