Sunday, January 6, 2013

a black bucket update

We are getting better at managing our heat sink.  BSH (before supplemental heat) the morning would find our barrels and buckets with a layer of ice formed across the surface and sometimes down the insides of the containers.  I had a single stock tank de-icer--an electric heater that would float in the tank and keep the water from freezing.  It is a farm product meant to keep the water for livestock from freezing.  It would not heat the water, the water would still be cold but it would keep it above freezing.  The barrel with the de-icer would be thawed but the others would have a layer of ice on them.  Sometimes the ice layer would be very thin, other times it could be up to 1/2 inch thick.  The sunlight coming into the greenhouse would spend much of it's energy trying to melt the ice before it could warm the water.  I would help the process along but breaking up the ice and moving the de-icer from barrel to barrel.  Unfortunately the stacked buckets received little attention.

When we verified that the south side of the greenhouse near the glazing was significantly colder than the rest of the greenhouse and that the buckets there received no direct sunlight hitting them, the buckets were all moved to the north wall.  As we began moving the buckets to apply the black tape to them we discovered varying amounts of ice in the buckets.  Bucket near the floor had heavier ice production than the top row of buckets.  Buckets with tables in front of them blocking some direct sunlight had thicker ice than buckets hit fully by the sunlight.  Buckets in the corners of the greenhouse had thicker ice than those in the middle of the room.

As the sun hits the greenhouse first thing in the morning the west side is in sunlight and the east is in shadows.  As the sun moves across the sky the sunlight moves across the greenhouse from west to east.  I have been trying to notice on sunny days and yesterday at 9:15 the west 2/3 was sunny and the east 1/3 was still in shadows.  Today at 10:00 the west 3/4 was sunny and the east 1/3 was still in shadows.  By 11:00 the sun had hit the far east corner of the growing room.

In the winter the sun crosses the sky at a low angle.  The growing room is 11 feet from the south glazed side to the north wall.  Today the south six or seven feet were in shadows at the level of the floor and sun was directly hitting the wall and only the north 3-4 feet.  at the height of the tables there was sunlight over most of the area.  This should change as we move into spring and the angle of the sun becomes more over head.

northeast corner in shadows at 10:15 a.m.
Yesterday when taping the buckets there were still buckets with ice in them.  Most of these were near the floor and the corners.  When applying the tape I rearranged the buckets so that the thawed ones were on the floor and the ones that still contained some ice were on the top.  I taped a few more buckets but they started to have some condensation and I worried about the tape not sticking well.  I restacked the buckets so that the top bucket on each stack had ice.  I did not stack another bucket on top as I wanted to make sure that all of the buckets were thawed.  In the picture below the each of the top buckets still have some ice in them and if it does not thaw I will remove the ice so that all the buckets are thawed.  Common sense says that a thawed bucket will absorb the sun's energy more efficiently than a bucket with a mix of ice and water.  Common sense also says that if I can get all the buckets thawed and keep it above freezing overnight I should not have new ice forming. 

After discovering that some of the buckets still had ice in them after a couple sunny days and several days since it was below freezing in the green house, I decided to check the white buckets as well for the presence of ice.  Those buckets had been taped on December 29 and restacked in no particular order and not checked for the presence of ice.  There are two stacks of white buckets, one group to the east of the door and one group to the west of the door.  In checking the buckets for ice every bucket to the east of the door was thawed.  In the stack to the west of the door the top row was thawed but many of the the middle and bottom row buckets had ice.  Now the east group is more centrally located and probably receives more hours of sunlight than the west group but the other possible reasons for the difference could be that the area of wall behind the buckets east of the door is insulated and the insulation to the wall behind the west group has yet to be installed.

My goal for today was to make sure all of the buckets were thawed and to finish taping the last few buckets.  Some of the buckets had thawed and those that had not I fished the ice out of the bucket, replaced the water.  I stuck what ice would fit in a barrel with the de-icer so that it could melt.  The rest of the ice is pictured here:

 And here are the finished buckets all lined up:

 It is a sunny day and warm in the greenhouse.

The ventilation fan has kicked in and I am running the box fan to circulate the air.

I have a little concern about the sensitivity of the thermometers as the electronic thermometer is quite a bit warmer than the inexpensive plastic thermometer right next to it.  Both were in the sun.

Yesterday it was not quite as warm in the greenhouse and I had the box fan circulating the air and it did bring down the temperatures in the upper areas and evened out some the temperatures in the lower areas.  I think on sunny days the box fan will help to moderate the climate inside.  Right now it is at one end of the room sitting on a table.  It may benefit from some tweaking.

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