Wood Heat and Solar Heat
Wood heat and solar heat systems can work in harmony. Although they both gather heat from different sources they can share the same heat storage system.
In most cold climate areas the quantity of solar heat available during the winter months is minimal but that's OK because there are other sources of heat energy available like wood. Burning wood during the summer to make hot water is not a cool idea since there would be an excess heat to deal with. Likewise it's foolish to rely on the sun to directly supply hot water throughout the winter months unless you live in a sunbelt area. I live in the snow belt area of central NY so like many people I need more than sunshine to get through the winter. Both wood and sun systems have their place and the nice thing is that they can share the same heat storage place.
HEATING a well-insulated house with wood is not difficult.The stove should be centrally located on the first floor of a living room with an open staircaseplenty of open space. Bedrooms on the second floor can be heated with natural convection currents. A heated first floor supplies heat to the second floor naturally. An interior chimney lined with stones also helps distribute heat evenly. This moderates temperature swings and minimizes heat losses while a stone wall in back of the wood stove not only provides additional thermal mass to store heat but also provides a safe fire wall.
HOT WATER could be extracted from a water jacket inside the stove or a coil of copper tubing wrapped around a stove pipe. These are the common methods used to make domestic hot water with a wood stove, but there is a better way that I will soon discuss, As you know clean combustion takes place at high temperatures. If the stove box is cooled prematurely to heat water soot and carbon monoxide are produced so itís better to remove wood heat after combustion takes place. An interior chimney provides an ideal surface for heat extraction. Soot clogged stove pipes can be avoided by using a chimney to extract heat for domestic hot water.
CHIMNEY HEAT keeps a column of hot air rising, but that column of hot air should be smoke free. After complete combustion takes place within the wood stove itís all right to remove heat from the chimney with copper tubes. Chimney blocks provide a barrier between the high temperature exhaust gasses of the stove and the low temperature water circulated through a network of copper tubes plastered to the outside of a chimney. Although water circulated through heat transfer tubes does cool down a chimney somewhat this cooling effect is minimal. As a matter of fact extracting heat from an interior chimney with water cools the chimney down less than an exterior chimney exposed to the elements. In other words chimneys built outside collect more soot than chimneys built inside used to make hot water so as long as high-temperature, complete-combustion takes place within the wood stove soot buildup will not be a problem.
Chimney Heat Transfer is a little different. Instead of using metallic absorber plates the flow tubes are plastered directly onto the outer surface of the chimney blocks, but before doing this the copper tubes are painted with polyurethane. This protective coating prevents copper from reacting with the cement.
In this illustration
four heat transfer tubes carry water up one side of a chimney and four other
tubes carry the water down. Cold water flowing through the left branch picks up
some heat and additional heat is picked up on the way down the right branch. Hot
water exiting the flow tubes returns to heat storage tanks in the basement.
Multiple drums may then be used to increase heat collection efficiency. This is
accomplished by circulating the coldest possible water from storage.
Domestic hot water is gathered with PEX tubes stuffed inside storage tanks. Potable water flows through the PEX tubes to preheat water supplied to conventional hot water heaters. You may not get all your hot water from a wood stove, but youíll get what you need. If you need more adjust the controller differential down and lower the thermostat on the hot water heater. If you feel brave you could even turn off your fossil fuel system. At any rate your heat and hot water bill be lowered and your chimney will remain clean. Potable household water flows through 600 linear feet of PEX tubes inside the storage tanks. The cold drum preheats water for the hot drum and the hot drum preheats water for the gas hot water heater. I donít expect to get all my heat and hot water from wood but I do expect my heat energy bill to be minimal this year. And I also expect the inside of my chimney to remain clean.