Aquaculture application - heating saltwater

Discussion in 'Geothermal Heat Pump Applications' started by Jeremy Esposito, Dec 23, 2017.

  1. Jeremy Esposito

    Jeremy Esposito New Member

    Hi all,

    New to the forum here and did some digging on the subject before posting -- I wasn't able to find anything relevant, so here it goes.

    I'm part of a build team on a new waterfront space in the NY metro area, where we'll be pulling up saltwater for a wet lab.

    Looking ahead, we'll want to be able to pull 5-10,000 gallons of water per day. At the height of winter, we'll need a delta temp of 20' Celsius, or more (water temps in Feb/March ~ 5' C, and colder). It's a ton of energy, and without a doubt will be our largest cost in the winter.

    I had been considering running plumbing underground for the initial leg of intake, before hitting a boiler/heat exchange unit, to give us a "free boost" of heat.

    Looking for input from you pros on the following questions;
    1) Looking into HDPE, but can't find anything larger than 2" - are there 3" products?
    2) How deep will this run need to penetrate, for substantial heat gain?
    3) Is there a flow rate/surface area/length of pipe calculation for estimating heat exchange?
    4) Also considering the pros/cons of a tank, rather than running pipe. Would a continually-recirculating underground tank be a better bet?

    Thanks for reading
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Hi and welcome!
    Hdpe pipe is available in whatever size you can afford. It can also be fabricated into tanks. It is going to tale a immense volume of pipe to reach that delta T with that much volume with a 24 hour turn around. Can you recycle your salt water or is it consumed in your process? A better concept to explore would be to see if a shallow well would yield enough salt water for your needs, at a higher delta T to start the process. I was involved doing this years ago to harvest salt water that was free of biologic fouling.
    Hope this helps
  3. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    I have done these numbers for fish hatcheries (awesome payback) and the key is to setup a heat exchange prior to adding btu's to the system. In your case, I'm guessing a titanium heat exchanger for the salt water. Do this so your discharge water can exchange some of its heat with the new makeup water.

    Then revisit your loads and size your system appropriately.

    edit- sorry missed one crucial statement of yours. Sounds like you already have that part figured. As to the header runs you are looking at running underground. You will have very limited heat exchange taking place at those pipe sizes/flowrates.
  4. Jeremy Esposito

    Jeremy Esposito New Member

    Thanks for the input,

    All saltwater will be dumped at these high temps, so you bet we're looking to transfer that heat to the water. Sorry for not being clear about that earlier. We'll integrate a titanium heat exchanger(s) to regain heat being dumped. Additionally I am considering sleeved conduit, or some form of side-by-side piping to continue that heat transfer to the incoming water after it passes through exchanger- if it's worthwhile... but I'd imagine if we size it appropriately the heat exchanger would do all of the work.

    And as for SW wells -- Sterile (or decreased variable), raised-temp, SW sounds better to me than a hot date at this point in my life. I'd imagine it's the same concept as FW wells, just close to shoreline. I'm interested in learning more about it.

    Minimum intake size is 2"
  5. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Your assumption is correct. Salt water has a interface with the fresh water gradient along the coast. If the salt water can be extracted from depth via a well, it will give you a constant EWT for your usage. At what depth that occurs and what the temp is would require a small diameter test well. There is a ship load of drilling in the NYC area right now for geothermal given the incentive climate. It should not be that hard to find a engineering group that has a driller in the NYC area now to at least " spitball " about the concept and possible outcomes for the project.

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