On 10/11/2015 11:00 PM, Bob F wrote:
Muggles wrote:
On 10/10/2015 11:30 PM, mike wrote:
On 10/10/2015 8:55 PM, Muggles wrote:
On 10/10/2015 7:07 PM, mike wrote:
On 10/10/2015 9:48 AM, Don Y wrote:
On 10/10/2015 5:40 AM, Stormin Mormon wrote:
On 10/9/2015 4:44 PM, Muggles wrote:
Roof de-icing cables? hmmm I've never worked with those or
heard of them
before. How efficient are they? I'm looking for any idea that
might work.

Eventually, we're installing some solar panels to run anything
we might
need in the green house, but right now it's all on the grid to
the more
efficient the heat source the better.

Pretty much all electric heaters are the same
efficiency. 5,200 BTU per hour with 1500 watt
consumption.

From what I can see here, the big problem is
heat loss over night. Consider focuss your
efforts there. Vapor barrier to slow evaporation?

I don't know anything about farming fish, but don't you need
some water/air exchange to keep the oxygen level tolerable to the
fish. If you just block the surface, what keeps the fish alive?

It takes 1 BTU to heat a pound of water 1 degree. Let that
pound of water *evaporate* and you've LOST ~1000BTU's!



We have air bubblers in the tanks. They work even if the tanks are
covered.

So, where do the bubbles go?
Wherever that is is where the evaporation goes.
The bubbles assist evaporation. The air flow also carries away
the heat you're trying to contain.
Best way is to use thick insulation and seal the area between
the water and the insulation. But you can't have bubbles if you
do that.
You have to do the thermodynamics math for the whole system.
It's very easy to spend a lot of money optimizing one thing, then
ruin that optimization by some other optimization decision.

The bottom line is that you have losses from the system to the
environment. You keep the temperature stable by adding
heat equal to those losses. If you do that, what goes on inside
the system is largely irrelevant when it comes to operating costs.

Anything solar only works during the day. But your greatest need
is at night. Managing that requires the same amount of heat, but
you need to store it at a higher temperature during the day
and release it at night. That means you can't use the huge amount
of water in the fish tank as the thermal mass...unless you like
your fish well done.

Do you think the water would hold temps better if the pumps were
turned off at night? The bubblers have to stay on to oxygenate the
water, though.

Yes, turning off the pumps will eliminate heat loss from the pipes after they
cool off. But in freezing weather, pipe damage risk increases.



Well, all the pipes for the green house will be physically in the green
house and it's going to be insulated better than our house!

--
Maggie