Best Of

Excellent article Larry.

Thank you for your research and ongoing promotion of THE most efficient system in the World, that being solar thermal.

As you know, I've been involved in solar thermal since before it was even on the DOE's radar. I have a 2 panels system on my mountain home that heats the home when we aren't there, and preheats the DHW when we are there. I keep the house at 40 degrees F when we are away, so all the radiant (walls, floors ceiling) surfaces are at at around 40 degrees F when the system fires, keeping the fluids below 70 degrees F, thereby maintaining solar efficiencies that are WAY high.

I wanted to pop in here, and (once again) talk about the potential that most hydronic snow/ice melt (SIM) contractors are overlooking that is staring them right in the face. That being the possibility of turning their SIM system into a large surface area high and ultra high efficiency solar collector.

During non SIM operations, there is a LOT of free energy falling onto this surface that could be put to use, either as a simple DHW preheat, heating pools/spas, and even space heating.

My concept is one of a two stage design. 1st stage would be a semi direct exchange that transfers the solar heated glycol into a storage tank with a heat exchanger for DHW preheat. When the delta T drops to the conventional "off' point, the 2nd stage kicks in.

2nd stage slows the circulation on the source (SIM) side, and directs this low grade heat into a water to water heat pump. These heat pumps would be running at around 200 to 300% efficient (COP of 2 or 3, depending). During the warmer summer months, the system would actually harvest what I refer to as "Ambient Energy", that being sensible energy that is not directly related to the solar gain. Remember, thermal energy flows from hot to cold. These systems make a lot of sense wherever there is a constant (annual) demand for DHW, which includes residential, commercial etc.

In commercial applications, like restaurants, laundries and other high hot water demand situations, I strongly believe that we could collect more energy for water heating, than they system would use in its SIM role. I've monitored some SIM systems during the summer months, and have seen slab temperatures approaching 140 degrees F. Granted, this is a stagnated condition, but the physics for extraction are there. Typical SIM systems have 5/8" PEX installed at 9" O.C., thereby making it very conducive to extracting all this free energy. When I was the Director of the RPA, I was at a code hearing conference, sitting next to a young lady. I asked her what her interest were in code development. She told me she worked for The Sierra Club, and that she was there to recommend that all SIM systems be outlawed due to the egregious waste of a precious natural resource. I told her of my reverse solar concept, and she said that she didn't realize that it was even a potential, got up and left the meeting without making her pitch. I guess what I am trying to say here, is that the environmental lobby has SIM in their gun sights, and that we as hydronic contractors had better be proactive in our applications, and start thinking outside the box, or the government and the enviro lobby will take that box (SIM) away.

These same slabs can also work as a very efficient heat rejection system due to night sky re-radiation. I've seen my solar thermal panels sub cool below ambient as much as 20 degrees under clear night sky conditions. I could use that in my mountain home for cooling from the radiant ceilings, if needed, without even firing a compressor.

Again, thank you for your continuing efforts to promote what the good Lord gives us for free, that we need to utilize to a greater degree, that being solar thermal. Stay well my friend.

ME