Heat Storage Systems

Optimize Efficiency - Reduce Service - Simplify Operation - Extend Boiler Life

Heat storage system example

How A Heat Storage System Works:
A heat storage system is an important component of modern wood boiler systems. By absorbing extra heat generated during the burn cycle, heat storage allows wood boilers to operate with less tending, lower emissions, and higher efficiency. Heavy tank insulation holds stored heat, allowing for 24 hours or more between burn cycles. Wood boilers used properly with heat storage will form no harmful firebox condensate and will outlast boilers used without thermal storage. Heat storage is a condition of some wood boiler warranties and EPA approvals.
Using a properly sized heat storage system with wood pellet and wood chip boilers can reduce on/off cycling by half or more. Reducing cycling dramatically decreases emissions and the need for boiler service, while improving heating response time. This means less ash creation and a higher degree of building occupant comfort.
While not all boilers sold by Tarm Biomass require thermal storage, we almost always recommend it.

Pressurized Thermal Storage Tanks

Simple - Maintenance Free - USA Made - ASME Certified Tanks

Tarm Biomass Storage Tanks

Tarm Biomass Pressurized Thermal Storage Tanks are USA made from thick carbon steel and are ASME certified. They are insurable, safe, and designed to be maintenance-free and long-lasting. A heat storage system under system pressure is oxygen-free, which means the steel will not corrode when properly installed. The vertically designed tanks save valuable floor space while encouraging desirable thermal stratification. The tanks are insulated after placement for ease of movement and installation. Tarm Biomass has a wealth of expertise in the application of thermal storage and we provide conceptually designed piping diagrams. Standard diameters are 30 inches for 220-gallon tanks and 36 inches for 300 and 400-gallon tanks. 220 and 300-gallon tanks require eight foot high ceilings and 400-gallon tanks need nine foot high ceilings. Tarm Biomass stocks most valves and controls for easy integration of thermal storage with your wood or wood pellet boiler. Have a look at our Planning Guides to learn more about system integration.

  • 220, 300, and 400 gallon tanks standard; custom sizes available.
  • Maximum design pressure 125 psi.
  • Maximum operating temperature 450 0F far surpasses plastic and rubber alternatives.
  • Low head loss design.
  • Closed system does not require annual water level and Ph testing.
  • Heavy-duty commercial quality tanks.
  • Use with Fröling Energy Tank for excellent domestic hot water production.
  • One-year warranty.

Fröling Energy Tank

All-In-One Thermal Buffer and Indirect Domestic Hot Water Heater

Fröling Energy Tanks

The Fröling Energy Tank is a unique stratification tank ideal for use as a heat storage/buffer tank for small pellet boilers and/or as a high-performance hot water heater in other applications. The Energy Tank is now available with or without a domestic hot water coil. The 104’ long (64 square feet of heat exchange surface) stainless steel coil enhances a modestly sized, super insulated heat storage tank with exceptional water heating capability. The coil consistently produces domestic hot water even with low input temperatures. Large tappings further increase potential applications for the Energy Tank.
The Fröling Energy Tank is perfect for pellet boilers with 25 kW or less output. Pellet boilers modulate to match heating demand, but when thermostats are satisfied, it will take only a few minutes before a fully modulated pellet boiler will have to shut off. The Energy Tank solves that problem by absorbing surplus heat and releasing it again to the heat distribution system as required, which often eliminates on/off cycling. Wear and emissions are significantly decreased.

  • One size; 119-gallon carbon steel tank.
  • Stratification baffle enhances
    effectiveness of stored heat.
  • Zip on/off insulation results in losses of less than 1/3 degree Fahrenheit/hr.
  • Corrugated stainless steel coil creates 64 square feet of heating surface.
  • Strategically sized and located tappings for use as a thermal buffer or domestic hot water tank.
  • Sensor bar holds many sensors at various positions.
  • Perfect for Fröling pellet boilers up to 25Kw.
  • 5-year warranty.

Fröling Energy Tank With and Without Stratification Baffle

Thermal Storage Tank Piping

There are a wide variety of piping options when using one or more thermal storage tanks. If a larger buffer tank is required, one to four tanks can be connected together either in parallel reverse return (preferred method) or in series. The parallel reverse return system (A) (also called Tichelmann System) guarantees equal charging and utilization of energy in the thermal storage tanks. Having the same pipe lengths for both supply and return will prevent any balancing issues. When the tanks are physically different in size or are not in the same location, series connection is an option (B). The first tank will charge before charging the next tank. Reverse flow removes energy from the tanks. Tarm Biomass has many plumbing drawings available - please see our planning guides (wood or pellet).

Recommended Tank Sizing

Boiler ModelBoiler OutputVolume (Minimum - Ideal)
Fröling S3 Turbo 30 Wood Boiler 95,539 Btu/hr400-800 Gallons
Fröling S3 Turbo 50 Wood Boiler163,783 Btu/hr600-1200 Gallons
Effecta Smart 40 Wood Boiler136,500 Btu/hr400-900 Gallons
Effecta Smart 55 Wood Boiler188,000 Btu/hr800-1200 Gallons
Fröling PE1 20 Pellet Boiler68,243 Btu/hr119-185 Gallons
Fröling PE1 35 Pellet Boiler119,425 Btu/hr200-325 Gallons
Fröling P4 48 Pellet Boiler163,780 Btu/hr300-450 Gallons
Fröling P4 60 Pellet Boiler200,000 Btu/hr400-560 Gallons
Fröling P4 80 Pellet Boiler273,000 Btu/hr600-740 Gallons
Fröling P4 100 Pellet Boiler341,000 Btu/hr600-925 Gallons