27 December, 2010

Happy Holidays!

The days at the farm have been less busy now that winter is here. The crops are growing, but more slowly than during warmer months (they take almost three times longer to reach the same size). We are still harvesting for our restaurant-customers and we are also working on improving the technical functioning of the farm.

The Urban Farmer training classes are continuing. Last Saturday Vinnie Bevivino taught the farmer trainees how to insulate hoophouses most efficiently. Hoophouse #2 now has two layers of plastic on it, and a geothermal heating system (as do the other hoophouses). The shallow geothermal heating system, as well as a solar hot water panel were installed last week by board member Dr. Amir Abtahi and Adam Schwartz. (More on this below!)

We have installed mini hoophouses (officially termed, “low tunnels”) over the beds to keep the row covers from lying on and weighing down the produce. A row cover is a fabric that both lets in sunlight and traps some of the heat that escapes from the soil.

Under the row covers the plants don’t freeze!

And here is Dr. Amir Abtahi, teaching some volunteers about the 40,000 BTU solar hot water panel (a 40,000 BTU solar panel has enough energy to heat approximately 40,000 pounds of water 1 degree Fahrenheit). The solar panel collects heat by absorbing sunlight, which is then channeled by food-safe antifreeze through copper pipes to the heat exchanger in hoophouse #4:

The fluid brings collected solar heat to the heat exchanger (a series of U-Tubes in our case) tank, and then the heated water (which does not mix with the antifreeze) travels to an 80-gallon water reservoir set in the ground of hoophouse #2:

The heated water in the tank is currently being used to deliver heat to the greenhouse through a radiator, though in the future it would likely be used to heat a trough to grow fish. The radiator can be a compact unit similar to a car radiator with a fan to force air through, or it can be a long copper tube that makes a loop around the greenhouse. Some greenhouses have these warm heating tubes embedded below or within the growing medium.

In hoophouses 2 and 3, a shallow geothermal system (independent of the solar hot water panel) has been installed 4 feet below ground. These “earth-tubes” store greenhouse heat collected from sunny days, which is then pumped out when the temperature inside the greenhouse falls below a certain preset value – usually in the early morning hours – through an air conditioning fan. This low-tech energy storage system is more sustainable than conventional heating systems, using 1/3 of the electricity, because it makes use of the natural heat retained in the earth.

Here is the air conditioning fan being used as a geothermal heating fan.

We had a unique volunteer join us! Daisy is Roy’s (an Urban Farmer trainee) pet chicken. Lazy Daisy has grown fat from a comfortable life, though she still provides Roy and his family with eggs.