Lagoon Heat Rejection System

[HVACHawaii]

I have a project that I am working on that the owner wants to utilize a lagoon adjacent to the site for a heat rejection system for residential heat pumps. We have been tasked in reviewing the proposed design/build. The project is in Hawaii so there are no real seasons. Also the lagoon is very shallow, only about 10 feet at the most.

Does anyone have any experiences with these types of systems? My concern is that since the lagoon is so shallow it will not stratify. The inlet and oulet are fairly close to each other maybe about 40 feet. The inlet will be at the bottom of the lagoon, and the outlet will be through a fairly large water feature with several levels of waterfalls and then discharge back to the lagoon. I feel this allow for a certain amount of evaporation but not enough to reject all the heat required. My concern is that the lagoon temperature will increase in pockets, and that short circuiting might occur.

In the summer ocean temperatures can rise to as much as high 70's. I feel that the lagoon because so shallow has potential to be much higher than that without much stratification.

If anyone has any experences or literature they would like to share, I would greatly appreciate it.

Thanks

 

[Wareagl487]

At first blush, if the water is constantly in flux with the tides from the ocean, I can't see there would be a problem - you would be using WSHP's and the ocean as the heat sink. You didn't state the size of the lagoon - but I can Guarantee one thing - 99% of the heating of the water is from the sun - heat from an HVAC system is no more than a spit in the ocean.

Andy W.

 

[HVACHawaii]

Sorry, I should have mentioned this is a man-made lagoon with no direct connection to the ocean, and is not affected by tides. I do not believe that there are significant currents that allow for mixing, therfore feel that our system may create a hot spot, allowing for short circuiting.

 

[Wareagl487]

Sorry, I should have mentioned this is a man-made lagoon with no direct connection to the ocean, and is not affected by tides. I do not believe that there are significant currents that allow for mixing, therfore feel that our system may create a hot spot, allowing for short circuiting.

AAhhh - with that - more information would be needed on the volume of the lagoon. If it is a 5 acre lagoon - no problems (assuming we ain't talking serious tons). But if it is a 40 foot by 40 foot one - there would be concerns.

Andy W.

 

[HVACHawaii]

The lagoon is about 2 acres, and it is about 250 tons. However, becuase there is not much mixing in the lake the boundary of our heat rejection may be much less. Maybe only about 10,000-20,000 sqft.

 

[AbbyNormal]

better check and see what the environmental people say about that

I am in the Caribbean, they would be all over me on a scheme like that

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

you have black sand there must be basalt or obsidian. be fairly abrasive stuff perhaps.

titanium HX

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[willard3]

The pond will cool from evaporation and wind velocity and you can check whether they match.

 

[tankanghan]

Here in our site, we have man made pond system where we reject heat into...but the pond circulate to another pond using spray and pump system to have better heat transfer...and i think its roughyl the same depth.....there is actually a pond design manual generated by one of our engineers here based on that scheme..i dont know the exact url but i think you can basically google this ..maybe DOE pond manual or something....