Thursday, September 5, 2013

A Funky Way to Make Fresh Water

It's gots to be funky!
Part 0. This idea applies to coastal locations where you've got a lot of AC load and scarce fresh water supplies. Places like the United Arab Emirates, Saudi Arabia and Southern California come to mind...

Part 1. Build a District Cooling Network. This is just like a District Heating Network only its purpose is to deliver cool water rather than hot water. The cool water isn't intended to provide cooling directly but to be used by Air Conditioning units as a heat sink. The idea here is that you save a lot of electricity because you do a lot less work when you use cool water as a heat sink rather than hot air.

Part 2. Once the water has passed through the AC units it will be at a temperature of around 60 degrees Celsius. You do two things with this water. 1. You sell what you can. I figure the target audience is people with hot tubs. 60 ºC water is hot in the hot tub hot. Jump back. 2. Send all the remaining hot water back to a desalination plant where it would be the heat source for a multi-stage flash-type distillation unit. Funky thing here is I used to run a 7 stage flash type distillation unit but we used steam as our heat source so I wasn't sure if 60 ºC was hot enough. Several papers on the internet machine say 60 ºC is hot enough - good enough for me. Anyways, after running through the distillation plant you'd again have cool water to send back to all the AC units connected to your District Cooling Network - by cool I mean it would be close to the temperature of the ocean. Neckbone.

Alternate versions of the idea could skip the desalination plant and instead just have some sort of heat exchanger to dump waste heat. Double dog alternately you could also skip the District Heating Network altogether and do a stand-alone setup where you use the existing domestic water connection to supply cool water to your AC and then feed the resulting hot water to your hot water heater. The problem here is that your cooling demand isn't tied to your hot water demand so you'd be wasting water. Wasting water is Super Bad. Gud gawd.

How much water are we talking about? I don't know. It depends on your flow rates. If I'm reading this ancient paper correctly for every 100 gallons of flow through your cooling network you should get a ballpark value of 10 gallons of fresh water depending on your ocean temperature.

Using the ocean, a lake or an aquifer as a heat sink for an AC unit isn't a new idea but I couldn't find anything on Google that mentioned the use of waste heat from air conditioning to distill water. Closest thing I could find was the use of waste heat from a conventional power plant as a heat source for distillation.

So is that a funky idea or what? Sommee love... wanna kiss myself... hey hey HEY...

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