A PA solar stock tank

[nick pine]

Gary improved his first solar stock tank

http://www.builditsolar.com/Experimental/StockTank/SolarStockTankProto.htm

in http://www.motherearthnews.com/do-it-yourself/solar-stock-tank-z10m0gri.aspx?page=3#ixzz1Xl5V3nYP

This might work better with a 10" Jolly ball
http://www.valleyvet.biz/ct_detail.html?pgguid=30e0742c-7b6a-11d5-a192-00b0d0204ae5&ccd=IGO043&gclid=CMX97c7QnKsCFYpM4AodCDiCgA
or a 10" Styrofoam ball http://www.plasteelcorp.com/foamshapes/smoothfoam_styrofoam/10071.html
under a round hole in the floating foamboard.

Where I live in PA, 1000 Btu/ft^2 of sun falls on a south wall on an
average 30 F January day, so a 2'x2'x4' galvanized metal 70 F tank
with 2'x4' of R2 twinwall polycarbonate glazing with 80% solar
transmission over the south side would gain would gain 0.8x1000x8ft^2
= 6.4K Btu and lose about 6h(70-30)8ft^2/R2 = 960 Btu during a 6 hour
solar collection day, for a net gain of 5440 Btu.

A tank that's 4' vs 2' above the ground could gather more sun and be
easier to drain and clean. If the lower 2' of 4'x4' of glazing
transmits I = 6.4K/6h = 1067 Btu/h to the airspace below a 70 F tank
with 32 ft^2 of surface completely surrounded by air (not packed with
insulation), with a glazing resistance Rg = R2/16ft^2 and an Ra =
R2/3/32ft^2 tank surface airfilm resistance and a Thevenin equivalent
sunspace temp Vt = 30+IRg = 163 F, the tank will gain 6.4K Btu
directly plus 6h(Vt-70)/(Rg+Ra) = 3826 Btu from 70+3652/6hRa = 83 F
air, for a 6-hour net gain of 10,226 Btu.

With a T (F) tank temp, the air temp surrounding the tank Td = 0.857T
+ 23.9 F during the day. With Rv insulation (eg 2" Styrofoam walls and
cover), 12.8K Btu = 6h(Td-34)(16ft^2/R2+32ft^2/Rv)+18h(T-30)(8ft^2/
R2+24ft^2/Rv)+24h(T-30)8ft^2/Rv, so T = (2574Rv-3443)/(12.9Rv+131), if
I did that right. Rv = 10 makes T = 86 F.

On a cloudy day, with a tank thermal conductance G = 8ft^2/R2+32ft^2/
R10 = 7.2 Btu/h F and capacitance C = 100galx8.33Btu/F/gal = 833 Btu/
F, time constant RC = C/G = 116 hours, so the tank would cool to 35 F
in -116ln((35-30)/(86-30)) = 280 hours, after about 12 cloudy 30 F
days.

Nick

[Gary BIs]

Hi Nick
That's interesting -- had not thought about raising the tank to get more
collector area.

I think that 4 ft might be a bit high for horses to drink out of? And, (I
think) it would have to be well anchored as horses (at least some of them) like
to push stuff around? Will have to ask my horse neighbors about this.
But, even getting the collector to 3 ft tall would be helpful.

I'm probably going to have a chance to build another as my new neighbor is going
to get a horse and after talking to the other neighbor would like one of the
tanks. So, there is an opportunity to make some improvements.

This was suggested to reduce heat loss at the watering hole:
http://www.builditsolar.com/Projects/WaterHeating/CanvasOpening/CanvasOpening.htm
Nice and simple, and says its effective.

Several more designs people have sent in:
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm#Animals

Gary

[nick pine]

Gary BIs <g...@builditsolar.com> wrote:

> I think that 4 ft might be a bit high for horses to drink out of?

My horse neighbor seems to think not, altho she agrees they might tip
it over.

I've tried building about 5 solar stock tanks. Horse and horse owner
behavior matter a lot. My neighbor says "How would you clean that
tank?" She dumps her tanks and scrubs them out every 3 days or so,
when they collect dirt, leaves, wolf spiders, and so on. Some of her
11 horses stand in the tanks. That would be harder to do if they were
taller. A tank with a drain might have a valve and a hose to help it
drain faster with additional head.

> This was suggested to reduce heat loss at the watering hole:http://www.builditsolar.com/Projects/WaterHeating/CanvasOpening/Canva...

> Nice and simple, and says its effective.

Nice...

> Several more designs people have sent in:http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm#A...

When I tried bubbling air through an above-ground tank, it froze
solid. I guess that only works with a pond or a buried tank.

Nick

[barbara deane-gillett]

just as a data point.  i had been heating my above ground 24 foot x 4 foot swimming pool ( would be similar to a large stock tank)  in nh  with some 8 4x10 roof mounted pool colectors.   the roof faced west and had a 20 degree slope.   needless to say early mornings and spring output weren't great.

one day i decided to paint the vertical south exteriror  wall of the pool black.   boy did that help.   first the wall was exposed to the april sun much more directly and thruout the day.  second the heat transfer to the pool was great because the sun struck the  blackmetal pool wall directly and the only thing between the heated wall and the water was the very thin 20 mill pool liner.    in spring the object is to get the water up from freezing so the pool wall barely runs above ambient air during the day resulting in near zero loss back to the air. 

in my case i doubt the addition of a glazing would help much although it might be worth it as the pool temp rises to swimming level.

of courses the losses were the same.  in summary the cheap black paint   extended the season 3 weeks on either end. 

imagine the effect if all above ground pools came with black exterior walls.   even better if they were selective.

further in summer the south wall of the pool got less sunlight so didn't overheat. 

> Date: Thu, 15 Sep 2011 05:17:08 -0700
> Subject: Re: A PA solar stock tank
> From: pine...@gmail.com
> To: suns...@googlegroups.com
> CC: marcuscr...@aol.com; magich...@aol.com; foxw...@verizon.net

[John Canivan]

I was thinking that a bulk head fitting perhaps 2" diameter with a spigot
could solve the drainage problems than the tank could be secured to a high
platform.
John

----- Original Message -----
From: "nick pine" <pine...@gmail.com>
To: "sunspace" <suns...@googlegroups.com>
Cc: <marcuscr...@aol.com>; <magich...@aol.com>;
<foxw...@verizon.net>
Sent: Thursday, September 15, 2011 8:17 AM
Subject: Re: A PA solar stock tank

[CJE]

Bubbling only works if you have warmer water to constantly bring up to the surface. Like from a buried tank or the unfrozen water at the bottom of a river. If you don't have something heating the water, like the Earth below a frost line, it won't work. It's not the motion of the water - it's the heat content of the unfrozen water that you are after.

stephen
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On Sep 15, 2011, at 8:17 AM, nick pine wrote:

When I tried bubbling air through an above-ground tank, it froze solid. I guess that only works with a pond or a buried tank.

Nick
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