Friday 4 February 2010

Using water as a way of containing heat for better use is not an original idea.

The first place I had seen of a place using water to collect heat was in Eugene, Oregon, sometime in the early 1980s at a nursery and garden center. They were selling a product called Wall o' Water, which was a circular plastic apron about 18 inches in diameter with water-filled bladders running lengthwise. The plant - I remember seeing a tomato - was placed inside. It was advertised to improve productivity in the cool Willamette Valley soils.

When I arrived back in Alaska in 1994 I hadn't forgotten seeing it. With my Palmer garden up on the hill, I thought about improving the model by burying two-liter bottles filled with water, leaving only the top four inches exposed to the sun. My thinking was that the heated water would circulate down into the soil, warming the roots, and the heat would rise around the plant. I planted some peppers, getting so-so production, along with a few tomatoes. My little Subarctic grew about one foot high, and then filled itself with dozens of cherry tomatoes.

Several more years passed and we found ourselves in Galena. After ripping apart the abandoned shed and turning it into a greenhouse, I started filling it with bottles. The first year we took temperatures of the water, finding that the liquid heated to more than 100 degrees in the daytime, and remaining in the high 70s the next morning. The students at school were kind enough to gather bottles for me, and I've been saving the cranberry juice cocktail bottles faithfully, so we now have quite a little heater garden going. I figure that I have 300 bottles of various sizes in the greenhouse.

The best bottles are made by Gatorade and the Cranberry Juice Cocktail folks. The lids are sturdy, and the bottles are made of a thick plastic which remains impervious to the winter cold. The bottles are literally out there in the greenhouse right now, filled with frozen water, stacked like logs. They'll thaw just fine. It's a lot easier than dumping out the water every year and refilling the bottles.

My big mistake early on was the use of glass bottles. Of course, the water had been dumped out, since I assumed that the expanding ice would crack the glass. However, I found out at the end of the winter that the glass around the base of the bottle cracked on practically every bottle, leaving me with a field of tiny glass fragments in the dirt and on the shelves.

Bottles lined up along the wall supplying heat for the watermelons.

Gallon bottles in the middle of the room; smaller bottles along the north wall.

Bottles along the north wall.