As the darkness of December descends on Imani, a group of volunteers completed work on the climate battery in the greenhouse at Imani II. Just to recapitulate, the climate battery concept was introduced by Jerome Osentowsky at the Central Rocky Mountain Permaculture Institute to extend the growing season in their greenhouses. Located in Basalt Colorado, CRMRI has been able to achieve remarkably warm temperatures in their greenhouses during cold winter weather using what Jerome calls a "climate battery". At 7,200 feet above sea level, the greenhouses suffer very low winter temperatures, but also enjoy lots of sunlight. CRMPI was able to capture the heat generated by the sun and keep it in the greenhouses using a climate battery. The climate battery consists of ducts located at the top of the greenhouse which connect to similar ducts in the ground under the greenhouse. Using small fans, the heat available during the hot sunny days is blown into the ground where it warms the soil. Jerome grows a number subtropical and tropical plants in the greenhouses. When the cold is too intense for even the climate battery to overcome, the staff fires up the adjacent hot tub and lets the heat warm the greenhouse. Now that's not just sustainable, that's a great permaculture lifestyle!
At Imani II. we've run 4" aluminium duct commonly used to exhaust household dryers along the top of the greenhouse. We've connected this to 4" drainage pipe buried a few inches below the ground on each side of the greenhouse floor. At the front of the upper duct is a 12 volt fan repurposed from a discarded computer. The fan is controlled by a thermostat commonly used for attic fans. When the temperature at the top of the greenhouse reaches 60 degrees, the fan comes on and blows hot air into the buried drainage pipes.
To enhance the solar gain, we've placed six donated 55 gallon plastic drums filled with water along the sides of the greenhouse. The water will capture the heat during the days and use it to warm the greenhouse at night. We're also using the tops of the drums as platforms for our planting beds.
The fan is powered by two 6 volt deep-cycle batteries connected in series to create 12 volts. The batteries are charged by a single 100 watt PV panel mounted on the south side of the greenhouse.
We installed an inexpensive ($12) electronic indoor/outdoor thermometer to measure the indoor and outdoor. Because it has been raining here in Brooklyn for the past week, the differential has only been averaging a couple of degrees between indoor and outdoor. I'm waiting on some sunny weather to see how much the sun raises the indoor temperature.
Today, Roman Yavich, Corey Hopp, Tommy and myself spread about 700 pounds of sand and gravel on the floor of the greenhouse on top of a layer of heavy plastic. The plastic will prevent moisture from coming up into the greenhouse house and the sand and gravel will help retain heat.
Finally we painted the drums black to increase their heat absorption.
Total cost: $172. The solar panel and batteries are not included as they were borrowed from our aquaponics system which doesn't work in the winter.
Below is the story in pictures.
A solar panel affixed to the south side of the greenhouse charges two deep-cycle storage batteries
An aluminum duct that runs along the top of the greenhouse ceilig is tied into buried drainage pipe.
Plastic drainage pipe is buried in the floor to transfer the heat at the top into the soil.
Sand is placed top of plastic on the floor of the greenhouse.
Tommy and Cory spreading gravel on top of the sand
Roman painting the water-filled drums with black paint
Some trays of micro greens on top of the black drums.
We will be monitoring the climate battery's performance over the winter months and will fine tune and adjust the system based on its performance. As an old boss once told me, "all good big systems are based on good small ones". As we learn about climate batteries in our little 10' x 12' greenhouse, we hope to apply our experience to larger greenhouses. The goal: help feed ourselves year round, not just in the warm summer months. After all, I do eat 12 months a year, and I suppose you do the same. Let's learn how grow locally 12 months a year as well.