How can I use thermal storage in my home?
Thermal storage has gained interest in Alaska as a way to save energy from burning conventional fuels and make it easier to use other sources like renewables. While it’s best suited for renewable systems like solar thermal, geothermal and biomass, it can actually be adapted to a wide variety of heat sources.
The concept is simple. Just like households store water for domestic hot water needs, in tanks ranging from a couple gallons to hundreds of gallons in size, you can store heat for a space heating system for a certain amount of time. Here’s a few examples of the ways it’s used in Fairbanks. You could use a buffer tank to store heat gathered from your solar collectors during the day to use at night, when there’s no sun. You could use a wood boiler to heat a big tank of water, so the boiler can run hotter and faster than it otherwise would if it were only heating your house. In both cases, thermal storage can be thought of as a “heat battery” because it holds energy to be used later. In this way, it can enable a heat source with intermittent delivery (like the sun or wind) to still meet demand.
Every thermal storage system needs three basic components: a heat source, a storage medium to store the heat (such as a tank of water, rocks or soil), and a discharge method (heat exchanger) to distribute the heat. Technically, any heat source can be used for this purpose, but you should select the fuel and storage material based on availability, cost, and compatibility with your home’s needs.
Also, many factors will drive the design of a thermal storage system for your home—such as your heating appliance, distribution system, heating demand, lifestyle, and many others. The design of the system will also depend on whether or not the system is being installed in a new home or retrofitted into an existing one, as retrofits must accommodate the existing distribution system and available space in the home.
There are various applications of thermal storage throughout Interior Alaska. A net-zero heating home built in 2010 uses solar thermal collectors and a masonry heater to charge a 5,000-gallon insulated water tank that provides heat to a radiant floor system, allowing the home to be heated with no fossil fuels.
At CCHRC, we use solar thermal collectors to charge a 25,000-gallon tank of water buried underground. Once the water is hot, it provides weeks of heat to the building when we would otherwise be burning some type of fuel.
If you’re considering a thermal storage system, the first step is to define your goal. Do you want to use renewable energy instead of fossil fuels? Are you looking for short-term (a few hours or overnight) or seasonal storage? Systems that are recharged daily are smaller and less expensive than seasonal systems. However you decide to incorporate thermal storage, it will probably be a very specific application tied to your needs and mechanical systems.