Water Temperature Control

[Robert Rowe]

Discussion posted by Robert Rowe on October 15, 2012 at 11:57 am at Arizona Aquaponics and moved to theaquaponicssource.com/forum/ water topics 2012-10-19.

This topic is an important issue to everyone choosing to work their systems year around and the Home Group has a bigger population.

I am going to try to bring references from other groups in hopes the topic will aquire a better focus.

If anyone objects to this attempt, please let me know, particularly Silvia Bernstein.

References:

Aquaponic Gardening by Silvia Bernstein

http://en.wikipedia.org/wiki/Heat_transfer

http://www.michigan.gov/documents/CIS_EO_Inside_indoor_pools_39511_...

Water Temperature Control

How do we best fight this problem?

Least we wander to far from the root cause of the Aquaponic effert - The objective to do the most with the least.

1. Know the temperature requirements for your fish type. See Silvia

2. Active or Passive approaches.

Passive - Controlling heat transfer around and under most tanks is inexpensive.

Total enclosure; perhaps, with a geodesic enclosure.

Raft Bed enthusiasts use an insulating board(Blue Board) to support their plants. I bet their grow bed temperatures do not fluctuate as much as their tanks.

The material used for pool covering is inexpensive and readily available.

This insulation lies on top of the water and inhibits evaporation(a source of cooling) as

well as providing a low R-factor of insulation. Provision must be made to oxygenate

the water; perhaps, more/larger bubblers.

Jim Troyer suggested Ping Pong Balls which he says can be purchased from the Mfg. as seconds, cheap. Sounds over the edge, but I like working out of the box. I believe Jim is going to give it a try.

Active - Electric

Gas

Solar

Compost heater (manure or clippings)

In all cases your investment in insulation pays off double.

3. Where in the system should the heat be applied?

1. At a point where temperature variation is minimized for flora and fauna.

2. At a point where heat loss is minimized.

4. Do we want/need to use brute force or get major effect with small effort?

5. Probably the singular key point in this discussion: is that, we are dealing on one hand with air which has nearly no mass and high temperature variation, and on the other hand with water and rock which have high mass and low temperature variation (if insulated) so insulating the Fish tank, Sump and possibly the the media beds needs to be the focal points.

6. I am thinking of a 700 Gal. Circular tank 26 in deep insulated around and below, with a removable insulated cover which would drop into place when the temperature is above or below critical values.

I live in Phoenix, and have since 1944 which kind of directs my focus, but the high night time temperatures are few as well as the low night time temperatures. leading me to conclude we are looking at few heating or cooling hours.

I hope this little effort generates a joint effort by all with help to share!

Links

Water Heaters

Randy Moss https://www.youtube.com/watch?v=N0fmQYs0y64

Larry in Casa Grande http://community.theaquaponicsource.com/profile/Larry285

http://www.theaquaponicstore.com/Fish-Sweaters-Aquaponic-Heater-p/a...

Research

Water Temperature Control by Passive means by Robert Rowe starting 2012-10-20

My 220 Gallon fish pond is surrounded around and under by 300 gallons of sand and the total enclosed on the perimeter by 6000 Lbs of concrete block. This in itself provides extreme mass to stabilize the temperature of the pond water.

The balance of the system loop consists of a 60 gallon raft bed which has a 2" sheet of blue board for a cover which contains 25 plants at present. The loop also has a 200 Gallon sump which is uncovered and has a exposed surface area of 22 square ft.

This system demonstrates the benifits of increased mass with limited exposed surface area.

I am currently maintaining a 11 degree differential between Outside air temperature and system temperture measured at the fish pool in the early morning.

As a secondary project, I have built 2 test beds constructed with 2" x 16" sides and 3/4 inch chipboard base with HDPM liners and configured as raft beds. Both beds contain 59.2 gallons of water.

These test beds are not in the system loop and the water is undisturbed.

The surface of bed 1 is covered completely by a sheet of bubble pack type pool cover.

This bed demonstrates the effect of minimizing evaporation. The R value is probably close to 0.

I am currently maintaining a 13 degree differential between Outside air temperature and

temperture measured at the contents of Bed 1 in the early morning.

The surface of bed 2 is covered completely by a sheet of 2" blue board.

This bed demonstrates the effect of minimizing evaporation plus the R-value effect of the insulation.

I am currently maintaining a 13 degree differential between Outside air temperature and temperture measured at the contents of Bed 2 in the early morning.

These results are based on the 2012-10-25 readings for the 6 days of partial data as the project evolved.

                  OAT/Tank/Tst Bd-1/Tst Bd-2

2012-10-20 60/72/xx/xx

2012-10-21 65/72/65/xx

2012-10-22 60/73/72/xx

2012-10-23 60/72/73/xx

2012-10-24 57/72/72/xx

2012-10-25 53/66/65/67

2012-10-27 57/66/63/70 added 3/4 coverage of tank with pool bubble cover over night

2012-10-28 55/66/68/70 added 3/4 coverage of tank with pool bubble cover over night

2012-10-30 52/68/xx/70

2012-11-01 54/66/68/70

2012-11-02 58/68/70/70

2012-11-04 55/68/70/70

2012-11-05 60/68/68/70

2012-11-09 66/70/xx/70

2012-11-11 40/57/xx/62

2012-11-12 45/56/xx/60

I plan to continue logging these readings for the short term.