Architectural brief for a biggish tank

[Diablo]

Friends,

I am in the process of putting together an architectural brief for a house I will be building over the next couple of years. I was hoping people of experience will take a look and determine if there is anything fundamentally stupid with this design. Let me state up front that there will be no real pictures for 12-18 months.

The tank will be 4m (l) x 3m (d) x 1.2m (h) [13' x 10' x 4'] or 14,400 litres [3800 US Gal.]

A partition will be placed at 1m [3'] making the effective display tank area 3m x 3m [10' x 10']. The partitioned off area will contain equipment, overflows, etc.

The tank will be visible on 3 sides, using 2.8m x 1.1m [110" x 43"] windows.

The top of the tank will open to a glass house / maintenence room / sky light above.

Here's what it looks like on sketch-up:

Room to the left is the study. The area to the right is where the kitchen may be.

The above is looking into the study window. This faces north (bear in mind that in southern hemmishere, North is the sunny aspect)

This area will be the formal dining and lounge area. Study to the right, corridor to the left.

This is looking at the top from the north, to give a better impression of the maintenence area.

And from the top. The maintenence area will contain 2 x 250litre (66 US Gal) surge tanks, lighting & ventilation. All remaining equipment will be in an equipment room located rext to the garage.

Any thoughts?

 

[spazz]

i think this design is very sound so far. time will tell in how you plumb the tank to the equiptment room. you might want to consider a couple of large surge tanks to give you better flow in the tank. those can be placed up high out of the way in the fish room.

 

[FishTruck]

Awesome. How to you plan to keep the top floor cool? Greenhouse fans will work nicely. Can't wait to see your PAR readings in your display!

 

[FishTruck]

Awesome. How to you plan to keep the top floor cool? You are going to have sky lights... right? Greenhouse fans will work nicely. Can't wait to see your PAR readings in your display!

 

[Diablo]

time will tell in how you plumb the tank to the equiptment room

I intend to run > 4" sewerage / drain pipe through the concrete slab as a conduit for plumbing. 4 x 2" pressure pipe (2 in each direction) will carry the flow. I will be using 5 x Finish Thompson DB15 pumps, 3 of which will be for main circulation and 2 for surge. I chose these pumps because they are industrial duty (mining), magnetically coupled (no seal) and very energy efficient for centrifugal pumps (180W, 60 gpm @ 10'). The actual pump looks like this:

The pump curves look like this (sorry for the 50Hz metric curves):

Main circulation will use 2 x DIY propellor pumps a bit like these (IMO, for tanks > 1000 Gallon, the use of centrifugal pumps for circulation is both environmentally and financialy impractical).

Awesome. How to you plan to keep the top floor cool? Greenhouse fans will work nicely. Can't wait to see your PAR readings in your display!

Hope to use an air/water heat exchanger. Air will be drawn out and passed through the heat exchanger such that excess heat is stored in a large water "heat bank" (>250G). This heat will be used for heating both the house in winter and a conservatory / solarium overnight to grow tropical plants and fruits.

In the summer when thins get too hot (day temperatures > 95F) I will use a ground loop for cooling.

 

[Elliott]

very nice, how do those propeller pumps work and what makes them more efficient? also, have you figured out how deep and what length your ground loop needs to be?

 

[spazz]

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where did you find these at? i have been looking for something like this for a long time.

 

[Diablo]

where did you find these at? i have been looking for something like this for a long time.

HDPE Propellor Pumps

These are genuine, non corossive in warm sea-water units. I should warn you though... very expensive. I got a quote on a 40,000 GPH unit and it turned out to be Euro 14K. If my budget was 4 or 5 times the modest $60k - $70k I intend to spend, buying the genuine artical would be a no-brainer... in power savings they have a 3 yr payback compared with centifugal pumps for the same voulume. But alas, I will have to knock together something myself. (These would be great for Bill W. though, no?)

very nice, how do those propeller pumps work and what makes them more efficient?

Propeller spins, draws water through the suction bell at the bottom, moves up the vertical and is discharged via an elbow at the top.

In terms of efficiency, all centrifugal pumps have an optimum efficiency at non-zero head. If you look at the curves above for the DB15, you can see that the point at 4m head and 9m3/hr is within the 68% efficient zone. As the curves move toward zero head, the efficiency drops. Bottom-line, centifugal pumps are not optimised for closed loop, zero head circulation. We tend to use them because they are cheap, convenient and for small tanks, the energy wastage is immaterial.

Propeller pumps on the other hand are optimised for zero head, to the extent that they're not very good at all at pumping up hill at all. This has been exploited recently by "propeller power heads" such as the turbelle stream and vortech pumps. These things move more water at 20W, than many centifugal pumps move at 180W. Same principle applies to the larger propeller pumps.

In theory, using an 8" marine propeller at 400 RPM, I should be able to move 40,000 GPH for < 100W. What I can achieve in practice will remain to be seen, but is a pivotal component of the tank design. I need to move at least 70,000 GPH. To do this using Sequence Darts, I would need 20 of them. While I can afford the up-front cost, at 180W each, 24/7, they would collectively cost > $500 per month to run, never mind giving me significant enviro-guilt.

 

[Elliott]

thanks for the nice explanation, why are they sooooo expensive?

 

[Diablo]

why are they sooooo expensive?

The economics of operating in an ultra-niche market.

The market for propeller pumps is modest. The market for those that can operate in sea water for extended periods, smaller. And for seawater recirculating systems that can't afford to have the pump disolve into the water... tiny.

Amortise 7 years R&D over a small demand where each individual pump is tailored to the end application and you get an expensive pump. Its a shame that they don't recognise the growing market in stupidly large home aquaria and create a set of off-the-shelf models that are semi-mass produced. I figure that there's maybe $1000 - $2000 of components in these things. I would happily pay $5k, but $20k is too much!