Certified WoodMaster dealer, Kim Quirk with Energy Emporium, shares the following article relating to a recent Flex Fuel install.
Here in New England many home owners have their own source of wood they can use to heat their home. Or, they may decide that local wood or pellets can replace fossil fuels helping them achieve a level independence from foreign oil.
Working with a few of these customers, I have had the opportunity to put together combination wood and solar heating systems for both home heating and domestic hot water.
Burning wood or pellets in a highly efficient gasification boiler will provide more heat then a typical home can use each hour…especially in the spring and fall. So many of the new wood or pellet boilers recommend (or even require) a large water storage tank.
Solar hot water systems also require a water storage tank because the sun can only provide heat during the day. That heat needs to be saved until it is required.
Since both systems can benefit from a water storage tank, then it makes sense and can save money to design one storage system that can be heated by either energy source. The wood does most of the heating in the winter; and the sun for the summer. The heated water can provide house heating, which we only need in the winter, and domestic hot water, which we need year round.
The Energy Emporium recently installed a large, very well insulated, 2000 gallon water tank from American Solar Technics that is heated with both solar (Sunda evacuated tubes) and a gasification wood boiler (WoodMaster’s FlexFuel30).
In the pictures above, the storage tank is in the process of being completed. Once the liner is sealed, 3-4″ insulation is added on top and then a final layer of 2″ foam board will be added on all sides.
The Woodmaster Flexfuel is used with cord wood or pellets. It can decide to start or stop the burn (for pellets) based on temperatures it reads in the water storage tank. It can also block out some times (daytime, for instance) when it will not burn so the sun has the chance to do as much heating as possible.
The solar thermal collectors were built in two rows with northern row 3′ higher than the southern row to avoid shading. The angle is optimized for winter heat production. Each solar collector array has its own coil in the storage tank.
We added datalogging equipment on the solar loops and temperature sensors at 3 places in the tank as well as the boiler in and out. Over time we can report on the efficiencies of cord wood versus pellets and how much energy the sun is adding to this tank. The expectation is that in the spring, summer, and fall the solar collectors will provide most of the heating.
In the image below, the green line indicates the temperature of the storage tank. The red and blue are temperatures of the heat exchanger and the shaded red area indicates that heat is being transferred to the storage tank. Notice that, even in February, when we have a nice sunny day, the solar heating between about 9:30am and 3:30pm was able to boost the 2000 gallon tank temperature. At about 5pm the pellets kicked back in to boost the water temperature for the evening.