In January the outside average temperatures are still declining (from about 24 degrees to about 20 in late January, early February) and we have used most or all of our long-term stored heat in the Solar Battery. Now our heating strategy shifts to a shorter cycle. Here is one of the major advantages of water heat collection, distribution and storage – it is flexible. It makes little sense to store heat in a fixed mass calibrated for longer-term storage when you would much prefer the heat be useable in greater quantities (BTU/hr) and in a sooner timeframe (tonight and tomorrow, not next week). This we can do with a couple of minor adjustments.

First, when our 300 gallon tank reaches 130 degrees we start heating the kitchen, master bath and master bedroom floors. Each of these contains significant mass that can store heat for later use. We do not heat the dining and family room floors because we still want to collect solar heat there directly. We heat in each of those areas until the mass reaches a set point, about 76 degrees or the air temperature reaches 75. Then we start heating the basement floor. This floor is directly on top of the Solar Batter, so it can accept much more heat and on a daily basis we do not expect to reach 76 degrees. These masses, combined with the very energy conservative shell delay the depletion of this stored heat. The main point of this strategy is to minimize the frequency wood heat will be needed that night or the next day.

Note: We still direct the collector fluid through the Solar Battery to lower its return temperature and maximize the solar energy we can collect. This is most important in this the coldest period of the year.

The second adjustment we can make is to reduce the 300 gallons storage tank to 250 gallons. We still keep the tank set point at 130 degrees. This adjustment reduces our solar domestic hot water capacity (slightly quicker showers are called for, but nothing too severe), and shifts more heat into the house in general.

The net result of the two above adjustments is that we will burn less wood and still be comfortable, but on the downside, we now have less long-term stored thermal energy, so if/when we have several cloudy/cold days in a row we will need to provide more heat with wood. However, on an annual basis, we still expect to burn about 1/3 of a full cord to meet our comfort objectives.

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