Hi there everyone,
Let me start this by saying that this is an honest question. I figure nobody would be better suited to answer my question than a group laser-focused on the negatives of the technology.
I see these types of memes a lot and see statistics of gallons consumed in a lot of articles I read. What I don’t understand though is where the water goes that it can’t be reclaimed or naturally return from a gas to a liquid.
As a kid(long ago), I was taught of the cycle of rain and the conversion between gases and liquid. It’s my understanding that when a liquid is used to cool something, it also follows the same conversion process as it cools.
Could someone explain to me what’s going on in this process where the 264 billion gallons of water used in the meme do not return to a liquid state?
I would appreciate any insight into the process that seems to defy this cycle that I am missing. Like I said prior, my knowledge of this process ended in middle school science class so I’m confident that I’m missing something.
Thanks for your time!
Water is drawn from a source and then evaporated. This is to cool down any large heat source rapidly. This is used both by combined-cycle natural gas power plants and by data centers. Computers turn 99.9% of the power they consume into heat, and data centers usually have about a 15% to 20% energy overhead. So powering 1MW of computers consumes about 1.2MW of power and produces 3.4M BTU per hour.
The water absorbs that heat and evaporates. Many data centers are built to consume water from massive underground aquifers. They drain the aquifer faster than it refills. So the water is being displaced, which means whereever you place a DC you are depleting the local water supply.
In addition, though, evaporation causes concentration of any solute. The evaporation tanks develop highly concentrated sludge of whatever was dissolved in the water when it was drawn from the aquifer. This concentration is usually high enough to be harmful to most life (very salty) or create harmful runaway biological processes (from phosphorus and nitrogen).
What’s the problem with capturing the steam, recondensing and reusing it again and again?
It costs money.
Sounds like something the legislature could address.
That is actually what they do for combined cycle gas turbines, they boil water using the heat from combustion of gas, then they condense the steam and turn a second turbine (hence combined cycle). They reuse that water again and again.
But to cool the steam down, the heat has to go somewhere. In CCG plants, that “somewhere” is a cooling tower full of water that evaporates.
The problem is that the steam needs to lose heat for it to condense. Where will the heat be dumped to? Your options are air, water, and earth. Air is a very inefficient heat dump. Earth is efficient at absorbing it, but it has a fixed carrying capacity per cubic meter. Water is efficient, transportable via pipelines, and can be expanded to meet increased demand without reengineering.
Instead of an evaporative cooling tower, a heat exchanger with a ground loop could work.
The ground can only absorb so much heat per unit of time before it becomes saturated. The geothermal field required for even 150MW is massive and insanely expensive. It requires something like hundreds of bore holes spread over 50 - 100 acres of land. It’s wild. The earth is the easy heat sink you think it is.