Is it just a matter of not being worth it? I see cooling towers releasing what appears to be a ton of steam, pretty high up. If that steam were captured at the top and allowed to condense, wouldn’t that result in a ton of water with a lot of gravitational potential energy? That water could then be released and used to power water turbines. Maybe I’m overestimating the amount of water being released as steam, or underestimating how much is needed to spin a water turbine to get a meaningful result, but it seems like wasted energy to me.
It’s not worth it. The energy you would generate is proportional to the vertical drop and the mass of water. If it were a river’s worth of water then you could generate a significant amount of power, but there just isn’t that much water mass in the steam.
You can use the leftover low-pressure steam for other purposes. For example, some places have combined heat and power (CHP) plants that use the steam to heat buildings, or run industrial operations that need a lot of heat energy. Though that requires you to live or work next to a power plant, which many people don’t like.
You can get a hell of a vertical drop for free though. A typical nuclear cooling tower, for instance, is about 500ft and thats not the limit to how high the water vapor will travel. Even a couple thousand gallons at that height is a lot of potential energy that could be recaptured, and it appears that large nuclear plants release several million gallons of water per day.
They don’t release that much as steam, though.
The majority of water discharged from nuclear plants is cooling water, which stays in liquid form the whole way. It’s just rather warmer on the way out than in.
I went looking for some number for fun. (Every work day needs a good distraction, right?)
The nuclear plant that provides some of my electricity supposedly intakes 24 million gallons of water per day. As far as I can tell, that is entirely to make up for cooling water that is released as steam. There is a lot more cooling water present in the system which is recaptured and reused.
24M gallons/day = 16,667 gallons/minute. That’s a significant amount of water. However, it’s several orders of magnitude less than the flow through the smaller hydro power dams in my area. A few that I looked at have average turbine discharges in the ballpark of 6,000,000 gallons/min.
So for the cost (and vast regulatory headaches) of adding a secondary generation unit onto a nuclear cooling tower, you can just dam a nearby river and get 360x the energy.
Edit: I was way off on that 24M gallon/day number. After more reading, it looks like only around 2% of that water becomes steam leaving the cooling towers. So condensing the steam would give us a flow rate of 333 gallons/min of liquid water. That’s barely enough flow to operate a water slide at a theme park, let alone generate significant electricity through a turbine.
Short answer you are correct it’s not worth it. The massive cost of a bigger tower and gravity turbine aren’t worth the tiny energy you get.
This video covers the basics of how cooling towers work to reuse as much of the energy as is reasonable.
I’d guess because it does not produce enough power to justify the cost of creating the condenser/turbine, otherwise, they probably would have.
How would you cool the water to condense it?
Getting it to cool efficiently is actually a very interesting challenge. Certainly more challenging that I thought before watching this https://youtu.be/tmbZVmXyOXM
Because efficiency. The amount of power generated from the water fall would be minuscule compared to the power generated from the stream.
Any engineering effort going into making this process more efficient would be better off making the steam generation more effective.
Short answer is because it isn’t worth the effort.
