I’ve covered pellet-fueled boiler applications in several past issues of PME. All of them have involved hydronic distribution systems. While such applications are certainly the prevailing way pellet boilers are used, they are not the only option. It’s possible to couple a pellet boiler to a forced air distribution system.

All hydronic systems designed around renewable energy heat sources — as well as those designed around conventional boilers — have at least one controller that measures and responds to temperature. Common examples are temperature setpoint controllers, outdoor reset controllers, mixing controllers and differential temperature controllers. Complex systems that operate in multiple modes, or use multiple heat sources, often have several temperature-based controllers.

As global energy planning moves away from fossil fuels and toward electricity, an increasing number of hydronic heating systems are being supplied by heat pumps. Some use water-to-water heat pumps supplied by geothermal earth loops. Others use air-to-water heat pumps.

Heated floor slabs, without floor coverings, have one of the lowest supply water temperature requirements of any radiant panel system. This makes them well-suited for use with renewable energy heat sources such as air-to-water heat pumps, water-to-water geothermal heat pumps, biomass boilers and solar thermal collectors.

This month I want to deviate a bit from a purely renewable energy topic to one that’s important across the entire spectrum of hydronics technology. It’s a topic that likely gets exercised on a daily basis in any engineering office where water-based HVAC systems are conceived.

Ever notice how new words or phrases continually slide into our social vocabulary? Here are a few examples that pertain to energy and buildings: Sustainability, energy justice, climate justice, beneficial electrification and decarbonization.

As interest and incentives build to transition space heating and domestic water heating systems away from fossil fuels and toward electricity, a somewhat predictable but only marginally quantified problem is developing. Two words describe it: Peak demand.

Heat pumps move heat from low-temperature sources to higher temperature loads. There are many types of heat pumps, but they all perform this basic thermodynamic mission.

Modern panel radiators are one of my favorite hydronic heat emitters. They’re easy to install, emit radiant and convective heat, and have high-quality powder coat finishes.