Has anyone used domestic water main as a heat sink for a water source

[Jabba007]

heat pump system?

I want to attempt it, but the principal (Owner) is not willing to guinea pig, and wants me to find other successfull installations first.

Essentially I want to "borrow" water from a domestic main, run it thru a plate and frame HX and re-inject it back into the main at a point downstream from where I took it. This will essentially utilize a very abundant heat sink for a large(ish)(400 ton) water source heat pump system.

Any ideas of where I can find examples of where this has been done before?

Jabba

 

[trashcanman]

I would strongly advise against doing that. Do you want to be responsible for someone getting sick from contaminants in the heat exchanger? Remember, you are dealing with POTABLE water, which must be protected at all costs against contaminants.

Look for another method.

 

[Jabba007]

In today's energy hungry world, we need to, in my opinion, lead the way to save energy. I think this has already been done. If it has not been successfully installed, the ol'man will NOT allow it. I expect to get denied by the water utility as well, but that does not relieve the political benefits of suggesting a progressive approach and making someone else make the difficult decision to use more energy.

I agree with you in principle though. At this point it is merely an exercise in conceptualization.

Jabba

 

[IRstuff]

Not to mention that I would be pissed if my cold water is sitting at 85ºF because of your heat dumping.

TTFN

 

[Jabba007]

Do utility companies guarantee water delivery at certain temperatures?

On the plus side... that would save money on the domestic water heating side of things too. Good point.



Jabba

 

[IRstuff]

Not if I wanted COLD water first.

You've still got the liability of protecting the water from contaminants of all sorts. ANYONE with intestinal ailments will immediately suspect your installation as being the cause

TTFN

 

[Jabba007]

Again, I stress that I do not expect that this will fly. Someone, somewhere will shoot it down, but I think it's been done before. I just can't lay my hands on when or where. I remember reading an article once in the far back parts of my brain about it.

I am just hoping that someone here can point me to an article or case study or something.

Jabba.

 

[IRstuff]

You need to understand where the box is and why the box is before you think outside of it.

One issue with the water supply, particularly residential, since the water flow is sporadic during the day, which means that you will not be able to get stable flow and heat removal.

Another issue is that if you are the only person doing it, then you get cold water. If there are 10 people doing it, then you're going to get lukewarm or warm water and there is less heat transfer to be had. That's in addition to the contamination probability increasing and the increased disruption to the supply as more people attempt to tap into the main.

Given the limited utility of the concept; dollars to donuts, any water authority would nix the idea and possibly lock you up as a danger to their customers. ;-)

TTFN

 

[cammax]

On a largescale project it would be possible if you had enough hotwater demand, it is not very different the the way we make potable HW now, problem is when your dhw use drops you lose your heatsink, might be best as an add on to a tower rejection system. plate+frame is out of the question for this application, as the potable water needs a double protection

 

[Jabba007]

Well, water volume is part of the reason it has to tie into a large main. Doing it off a branch is not an option here.

As far as what happens when everyone is doing it... just because it's not feasible for everyone does not mean it's not feasible for us.

I am considering using ground water from the site for this as well. The hang up here is how much IS there? It is a 10 acre site, with an underground parking garage over the WHOLE 10 acres. Ground water drainage estimates have been from 500 GPM to 30,000 GPM. Since it's being constructed in phases, we're going to build phase 1 and see how much there is. If we can use it then... we will if not we won't.

I still think someone has actually done the domestic utility tie in thing. They do make food grade anti-freeze as well, so even if there was a leak... it wouldn't hurt anyone. And we could always double, redundant isolate the domestic water from the source loop as well, IF the numbers supported the idea.

And I still think we owe it to each other to push the edge of energy effecient design. Someone HAS to be first to try something new, or else we'd still be living in the stone age right?

Jabba

 

[GMcD]

If energy saving is the goal, how much energy saving has gone into the building envelope in terms of reducing the cooling loads and heating loads in the first place? Exterior shading? High performance windows? Thermally improved exterior wall details with minimal thermal bridging? The plan should be to minimize the energy loads through passive means before tackling the active systems. I know of geo-exchange systems where a closed loop geo-exchange pipe system is installed along side/under water and sewer pipe trenches to take advantage of the "free excavation", but I am skeptical that using direct "water main water" through a heat exchanger is a wise thing, given the legal and health issues associated with the protection of the potable water supply.

I know of a firm (

http://www.cobaltengineering.com)

that is designing a direct water main heat pump system for a project in the Vancouver, BC area, but I don't know the details, and am watching it to see what transpires there. I believe the project is called the "Montenay" project.

 

[IRstuff]

They're listed a different description for a different? project in Vancouver:

http://cobaltengineering.com/projects/vancouver-aquarium-discovery-education-center

TTFN

 

[Yorkman]

Maybe I'm missing someting but with a double wall heat exchanger how is this different that using a glycol hot water heating system to heat your domestic.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[Warpspeed]

I believe your water utility will simply say no and roll around on the carpet laughing.

The ground water idea may be possible, especially if you pump the heated water back where it came from. It all depends on how much reliable flow is available.

What is wrong with just purchasing a commercial packaged cooling tower like everyone else does?

 

[chicopee]

Instead of using water from a water main to warm the evaporator side of the heat pump, have you checked other sources such lake water, well water, river water or even ambiant air(if the region is not too cold in winters)?? These other sources are used in heat pumps.

 

[Jabba007]

Some of you guys are killing me. No disrespect intended.

The building WILL have a water source heat pump system. It's a 400 ton system in a high rise building with retail, office apartment condo and very high end penthouses. There are reasons why a cooling tower, evap cooler ground loop, air coupled or well systems are not viable. The plan now is to use dry coolers on the roof of the 4th story level of the building, but there will be 6th and 7th floor penthouses that can look down on them. The Architects HATE that.

I am trying to push for something that breaks out of the standard 400 sqft per ton, 400 cfm per ton rule of thumb, "this is how we ALWAYS do it" frame of mind. Yeah I know using a city water main as a heat sink is not a common concept. I know there are hurdles. But, it is a fantastic concept to utilize a little used concept. Think about it, there are MILES of already buried, underground piping there to use. Like a giant geothermal loop field, NOT being utilized. It would also make the building MUCH more energy efficient to NOT have to run a cooling tower, or evap cooler or even dry coolers for that matter.

That's what I am trying to do here... push the envelope a little to make our business a little more energy aware. Yes it would be EASIER for me to do what everyone else does everyday.

Again... I mention that this thread was just to ask is anyone knew about an existing system like this. I am almost SURE there is. I just can't find it, and to be honest I have not looked THAT hard either.

If I was too harsh in this post, I apologize. I fight a battle at the office every day with a designer that is 65 years old, tired, ready to retire that does not want to LEARN about anything. He applies rules of thumb to everything and screws up a lot of stuff that I have to clean up. I am a little overly sensitive to the industry inertia to just do what we have been doing.

Just because something is new does NOT make it bad. If engineers didn't think up new stuff... we'd all still be sitting around a camp fire chewing on bones and wearing hides. C'mon people... help me save the world!

Jabba

 

[cammax]

I suppose you could become a utility and sell potable domestic hot water to your neighbors.

use your waste heat and sell the heated water for what it cost you, hardly cost effective when you figure in the man power to over see, operate and test to meet federal specs.

but the public util will not let you re-inject anything back into there system.

 

[GMcD]

With the area of parkade excavation, etc., have you examined all of the "free excavation" area to see how much horizontal geo-exchange potential there is? Your "rules of thumb" are only applicable to the standard crappy envelope buildings- currently we are designing buildings where we mechanical guys spend a lot of effort helping the architect design a proper envelope with better glass and we aim for over 1200 sf per ton for cooling, or better. Energy efficient buildings aren't about energy efficient systems, you have to minimize the heating and cooling loads first. What do your building load calculations show as the high heat gain/high heat loss areas of the building? Get to work on those before trying to figure out energy efficient equipment and systems.

 

[chicopee]

Trashcanman, check this site out "geoheat.oit.edu/bulletin/bull18-2/art40.htm " which is an analysis on heat pumps using underground stream as a warming medium for the evaporator side.

 

[KiwiMace]

The International Plumbing Code is pretty clear in preventing you from re-injecting back into the potable system.

What about splitting the supply into potable and non-potable for irrigation, toilet flushing etc. The non-potable water can be your heat source, and this may be seperately supplemented with filtered rainwater off the roof.