This month will be the end of this series of articles about controlling and powering these ultra-efficient, extremely comfortable systems.
The options of energy sources for the fantastic comfort systems has doubled over the past 10 years or so. We used to be confined to 80 percent efficient gaseous fuel- or oil-based boilers. While these options are still available, with the price of energy going up on a regular basis, consumers have the option of more efficient equipment in their crosshairs. It’s no longer a world of limited choices.
Gaseous fuel boilers: We now have access to gas-fired appliances (natural and liquified propane) with seasonal efficiencies that vary from 84 percent to 96 percent. Most of these newer appliances have some extremely intelligent controls on them, with the ability to discern the difference between three different temperature regime calls. After having been a guest at the 2015 AHR Expo in Chicago, I can tell you that some boiler manufacturers are also brining a new communications protocol to the game, with the ability for the boiler to communicate using wireless systems. Imagine getting a text message on your cell phone from a customer’s boiler telling you that it has experienced a lockout condition for whatever reason. You will know your customer has an issue before your customer knows. It’s a grand new world we are entering now.
Water source heat pumps: The days of single-speed, single-capacity heat pumps are quickly leaving. Not only are manufacturers capable of providing a two-stage scroll compressor, but they are now able to provide variable speed compressors that have significantly increased the efficiency factors beyond anything that has been known prior to the introduction of variable speed. It can eliminate the need for larger buffer tanks, and makes these systems much more compatible with solar PV systems due to the elimination of the hard start. This will only enhance the operation of these seriously efficient systems, making them even “greener” then they were before, with radiant comfort being the final product. With the introduction of radiant cooling, these reversible appliances make us an “all-season” comfort system with the ability to deliver radiant cooling with the same system that delivers radiant comfort on the heating side.
Air source heat pumps: These systems have also experienced significant increases in seasonal efficiencies, and even more increases are expected with the addition of outdoor reset controls and variable speed compressor motors. They still have their limitations as when it comes to cold air temperature operations, but significant strides are being made pertaining to operational efficiency. And with the ability to reject heat, these, too, open the doors for alternative surface-based radiant cooling system applications on a residential basis. It is hoped that the cost of these units will decrease, but they are still significantly less expensive than a vertical bore hole ground source heat pump system due to the elimination of the need for vertical bore holes.
Solar thermal: While not new by any means, solar thermal has always been extremely efficient when applied to the operation of low-temperature distribution systems that are a part of delivering good radiant comfort. There are a lot of new suppliers of evacuated tube collectors, which can literally suck energy out of a cloudy sky. An interesting — and often overlooked — fact about solar thermal is that it is typically three times more efficient at converting solar energy into a usable form of thermal energy than its electric-producing kin. However, when coupling solar PV with some of the newer soft start compressor technology, the efficiency can approach that of solar thermal, and it’s a lot less expensive to run wires than it is pipes, so expect to see more solar PV systems connected to air source DHW heating systems.
One of the biggest problems with solar thermal is that when you need it the most, you get it the least. And when you need it the least, you get it the most, and if you are not prepared to deal with the excess energy production, it can lead to problems with the system. With the introduction of low temperature, water-source heat pump-based seasonal energy storage systems, these problems are becoming less of an issue, and increasing the efficiency of these systems.
Woody biomass: Woody biomass, while not new by any stretch of the imagination, has become extremely efficient over the years. With the introduction of gasification boilers and the application of solid state controls, the new boilers are significantly more efficient. This has also created additional technologies to make them even more efficient, and less labor intensive than their smoky predecessors.
There are many more suppliers of pelletized wood burners, which has reduced the need for bulk wood storage because pellets take up much less space than cord wood. They also provide a much higher degree of reliability and convenience. Weekly ash removal is the norm now due to the increases in efficiency. There are even retrofit pellet burners for existing multiple pass cast iron boilers.
Seasonal energy storage systems: These newer storage methods vary in their applications and temperature of operation. One that really caught my attention uses a non-insulated storage tank that is buried directly in the ground, and during a call for heat then draws the tank temperature down to below freezing using water source heat pumps. It takes advantage of the phase change of water. With the thermal battery being at such a low temperature, pretty much anything with a temperature 20 degrees Fahrenheit hotter than the storage tank becomes a heat source. When coupled with a typical flat plate solar thermal collector, the collector efficiency is always kept at its peak due to the extremely cold storage tank. Typical coefficients of performance of the water source heat pumps are still maintained above three, even with the battery at 32°F.
Heat sources can include warm attics cooled by a fan coil unit, waste heat recovery, idle snowmelt systems basking in the sun, solar thermal solar collectors, air source heat pumps, ground source heat pumps with limited earth loop heat exchangers, woody biomass, or pretty much anything with the ability to generate heat in temperatures greater than the thermal battery storage tank. Google “battery storage tank” for more information on these fantastic new systems.
Phase change thermal energy storage: Phase change thermal energy storage is also not new. I was working with eutectic salt storage systems 35 years ago. Encapsulation and long-term storage were always a major downfall of the salt-based system, with activation levels being significantly higher than most solar systems were capable of delivering during normal winter operation. Advances in technology have changed all of this. We now have non-salt-based mediums that can be fine tuned to the customers’ needs, with melt/thaw ranges varying between 32°F and 200°F. While not actually a self-generating energy source, when properly applied, this material represents a significant contribution to the thermal mass flywheel effect, which enhances human comfort and thermal efficiencies.
Good contractors don’t limit their offerings to basic conventional appliances. Many of these newer technologies, when properly sized and applied, can take many projects to a net-zero energy configuration in short order. Look into these new technologies, diversify your offerings, and stay in front of the competition.
Tune in next month as I begin explaining the benefits of the upcoming Uniform Solar Energy Hydronics Code and the benefits of the ASSE-developed, ANSI-recognized RPA Designer/Installer certification program for hydronic heating and cooling systems. Do something good to start the year, and join our organization. www.radiantprofessinalsalliance.org/join
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