Topic: Does your greenhouse use any heat sink?

[GrannieAnnie]

I'm trying to plan out a used-window solar greenhouse and thinking of adding a wall-full of jugs of dark water (3 gal/sq ft of floor is needed for our area I've read). Have any of you added heat sink materials to yours and do you have any advice for a newbie?

I'm thinking of only having glass on the South facing wall, having a knee wall on the base about  a foot high then sloping the glass wall to the peak about 10 ft and insulating the other3 walls (except the used door has glass) plus running insulation into the ground, setting all on a brick perimeter. Approx. 10 ft? long by 6? deep.  (I read the depth should only be half the length and the height should be equal to the length)

The Negatives:
 A mish-mash of windows (most of them double and heavy as all get out). Quite a design puzzle.
 Used lumber (complete with bent nails of course::))
 I've never built any structure myself before

The Positives:
 Most of the wood= redwood  :D
 I'm retired and have the time
 My husband thinks I'm crazy to try this so he won't interfere ;D. This could also be a negative    since he has the muscle.

[davyw1]

You have me lost at what you want to to do as far as solar heating.

I would not only glass the south facing part of your green house as you are going to loose heat and light. Remember the sun rises in the east and sets in the west so the green house would only be in full sun from about 10am to 2pm.

You can split double glazing pains with a stanley knife. If you are thinking of using them as they are i would not reccomend it, as if the seal is damaged then the inside of the double glazing mists up so you loose light.

I have just finnished the frame work for my new hot house can post some pictures of how its done if you like

[thifasmom]

I have just finnished the frame work for my new hot house can post some pictures of how its done if you like

yes please  :)

[Rhubarb Thrasher]

here's a simple article for making a greenhouse heat sink. It uses a small solar panel to power a fan to circulate warm air through the heat sink material

i'd thought of doing one, but got confused about what to make it out of. I thought of something with a high specific heat capacity in something with a low thermal conductivity, and then my brain hurt and i stopped. I mean lumps of metal in a plastic drum filled with water

[caroline7758]

Think we need a link, Rt! ;)

[Rhubarb Thrasher]

http://www.reuk.co.uk/Solar-Greenhouse-Heat-Sink.htm  :D

i've worked it out. You need something that absorbs a lot of heat like metal particles. But these cool down quickly too, so you need an insulator to keep the heat in. But insulators stop things from warming up as well as cooling down. So you need a bit hole with polystyrene at the bottom to stop heat escaping downwards, a load of metal or high S.H.C material, then another insulating layer on top, and you need to pump air from the top of the greenhouse down into the bottom of the heat sink. So th greenhouse is probably cooler in the day when you have more heat than you need, and warmer than it would otherwise be at night QED  8) Promise  ;D

[Rhubarb Thrasher]

just had a look on ebay 5 solar panels for £4.99 (for 5!) - just the right voltage to run those PC cooling fans. A total bargain, unless i'm missing something

[davee52uk]

I tried last Winter using arrays of plastic ex-milk containers. These were filled with water and painted black. The idea was that they would absorb heat during the day and radiate it out during the night.

I put them in cold frames and on the north wall of a greenhouse.

I don't think they made a great deal of difference but will try again this Winter.

[coznbob]

RT,
        there was an episode on this on 'It's not easy being green' on a repeat a couple of weeks back, they used crushed glass for the heat sink, if that helps.... ;D

[GrannieAnnie]

I tried last Winter using arrays of plastic ex-milk containers. These were filled with water and painted black. The idea was that they would absorb heat during the day and radiate it out during the night.

I put them in cold frames and on the north wall of a greenhouse.

I don't think they made a great deal of difference but will try again this Winter.

the article I read also used that system but there is a formula for the # of gals /sq ft floor space. Also they insulated the perimeter down to the frost line. This kept the soil temp about 20 degrees warmer than outside. My goal isn't a tropical temp in dead of winter but just to grow lettuce and be able to start tomatoes early and grow some in the greenhouse all summer (removing part of the roof so they don't bake) to help them keep producing as long as possible into the Fall.  My little bubblewrapped cold frame was very successful so this should be at least as good I'm guessing. 
You are right about using glass in the sides. I'm using what I have.

[Rhubarb Thrasher]

I was allergic to It's not easy being green since the bloke seemed to start from the position of having a million pound house in the country and a full army pension. If I had a larger greenhouse though, i'd certainly try the solar panel and fan thing
The important thing is I suppose to try to make sure that there is still heat being given out at the coldest part of the night, which I guess world be about 4 am, which is a long time since it was being heated up.
The plastic bottle way won't be as efficient, because the plastic is an insulator

[davee52uk]

"........... My goal isn't a tropical temp in dead of winter but just to grow lettuce and be able to start tomatoes early ..."

I managed to grow a supply Lettuces for most of the year only missing out in late April this year by using cold frames and greenhouses. Lettuces like "Winter Density" will grow and survive with quite a lot of cold - my neighbour grew them outside during the Winter!

[saddad]

Some of the heritage varieties like Stoke and Bronze arrow grow well in a cold greenhouse here in Derby...  :-X

[jimbo51]

 :) THORGHT THIS SITE MAY BE OF INTEREST ON THIS SUBJECT opps sorry for caps

http://www.reuk.co.uk/Solar-Greenhouse-Heat-Sink.htm

[hippydave]

my workmate is making 1 of these his wife is a chemist and can get him the salts.
 Eutectic Salt Chamber
    Potentially the most efficient heating system of the six is the eutectic salt chamber. The salt being used is sodium sulfate deca-hydrate (NaSO4 • H2O -- Glauber's salt). Figure: Energy vs. Temperature relationship for Glauber's Salt At the right is a curve representing the energy stored as a function of temperature of a substance as it transitions from solid to liquid (phase-change). For example, it takes 80 calories to melt one gram of ice. In reverse, one gram (1 cc) of water gives off 80 calories as it turns to ice; this is called the heat of fusion. This heat of fusion principle is often used to save orchard blossoms from freezing if the temperature drops below freezing in the Spring by sprinkling them with water. As the water freezes, it gives off this heat of fusion and saves the blossoms. Thermal storage using water is not nearly so efficient, as water only stores one calory per gram per degree centigrade. Glauber's salt has the nice property that it melts at 90o F and has about 83 calories per gram. It does not take a lot of salt to heat several rooms. The salt in the chamber is stored in black tubes to pull in the day-time sun so that the salt melts. At night as the salt freezes at 90o F, the air is heated around the tubes like a radiator, which then rises,