How to Apply Solar Power for Your Greenhouse Heat Sink

What You'll Need
A shovel or spade
Polystyrene or foil
Stones, cut glass, or shingles
Standard PVC piping
A small cooling fan (the type used in personal computers)
A 12-V battery
A solar panel of at least 10 W.

A greenhouse is an effective way of harnessing solar power to extend the growing season for different kinds of fruits and vegetables in cold climates. Greenhouses absorb and trap the heat from the sun and provide your precious saplings with the warmth they need to grow on those cold winter days; but what about night time?

At night, all this stored heat dissipates and temperatures in your greenhouse can drop drastically. This can prove fatal to many plants. A heat sink is an excellent way of harnessing solar power to ensure that your greenhouse stays warm at night. Conventionally, any object that is cold to the touch is considered to be a good heat sink. You can find people digging pits in their greenhouses and filling them with stones, broken glass, rocks, or metal drums filled with water.

While these traditional methods are pretty effective, you can drastically increase the effectiveness of a greenhouse heat sink by actively using solar power to heat it. Let us find out how.

Step 1 – Dig a Hole

The first step is to make your heat sink. In order to do this you first need to dig a hole in the ground. Your hole should be at least 35 cubic feet in volume. Remember, the larger the hole, the more effective it will be at trapping heat. Remember to leave a gap at the bottom of the pit to run the PVC piping into the heat sink.

Step 2 – Fill It

Once you have dug the pit, you need to line it with some insulating material such as foil or polystyrene. Then fill the hole with stone, cut glass, or shingles. You can use any such material that feels cold to the touch. Avoid using finer pieces because the more air pockets that you have in your heat sink, the greater is the quantity of solar power that you can trap in it.

Step 3 – Affix the PVC Piping

Run the PVC piping so that it leads from the top of your greenhouse to the bottom of the heat sink. You will also need to fit the fan inside the pipe so that it can draw in air from the top of the green house.

Step 4 – Connect the Solar Panel and Battery

Affix the solar panel at the top of your greenhouse where it will receive maximum solar power. Connect the solar panel to the battery. The cooling fan will in turn be connected to the battery too.

How it Works

In this setup, you use solar power to charge the battery. The battery is then used to power the fan. During daytime, this fan sucks in warm air from the top of the greenhouse and directs it to the bottom of the heat sink. The heat sink stores this solar power. At night, when the air temperature drops, the air continues to be sucked into the heat sink, where it is warmed by this stored solar power. This helps in maintaining the temperature of your greenhouse even on cold winter nights.