Wheeler on HVACR: Residential Thermal Storage?
One of the hazards of writing a monthly column is that some manufacturers get the idea that they can talk you into writing an article about their product. In the industry we call them puff pieces. I have no reason to write that type of article. However, if you've been a long-time reader of this column, you know I will write about products that represent new technology, but even then I will tell you the bad along with the good. That's what this month's article is all about.
I had been getting calls from a hydronic HVAC manufacturer out of Woodinville, Wash., asking me to write an article about its residential thermal storage system. Admittedly I was intrigued, simply because most hydronic systems come from the Northeast portion of the country, not the Northwest. But residential thermal storage? I have some problems with that, and with some of the claims the company is making about its system.
First, there is the problem of how much savings thermal storage will realize in residential applications. Contrary to what the company's literature says, in most parts of the country there is no discount for nighttime electrical use. Second is the size of the thermal storage tank. It couldn't hold more than a couple-hundred pounds of water from looking at its size in the picture they sent me. That wouldn't serve too large a house.
My third objection is the company's claim that the system costs less to install than ducted air conditioning. Let's see: Condensing unit, piping, recirulating pumps, ice-storage tank, controls, ethylene glycol, electrical wiring, multiple wall-mounted fan coils? If so, it must not charge very much for its products. So I called up and asked the company to price a 3-ton 5-zone system for me. Nobody ever called back.
Well, that's the bad side. I actually think the concept is a great idea! For a fact, you can achieve major energy savings if you zone out a house with individually-controlled fan coils and shut off the zones that you aren't using. What's more, there are many jobs all over the country where such an idea would be a real problem solver. I can think of some applications right now.
The real gem in this offering is the fan coil which is shown fitting between 2X4 studs and flush mounting into a wall. It connects into a circulating hydronic system that is conditioned by a small chiller and a domestic water heater to create a very nice and energy-efficient heating/cooling design. Yes, heating and cooling (or just cooling only) come from each room-size zone. Perhaps someone else has something similar, but I haven't seen it yet.
What about the ice storage concept? While there may be little actual savings from this highly-touted concept in most parts of the country, it makes sense from a total design standpoint. The condensing unit just keeps the ice block cold while the circulating portion of the system determines how much cooling is actually needed to each area. So the ice ensures a ready supply of chilled water.
I like the idea because it makes a lot of sense where residential hydronic or steam heat is used, since it looks like it can be retrofitted fairly easily. It even makes sense in new construction where the lack of need for ductwork would allow for new architectural designs for homes. But commercial applications shouldn't be overlooked either, especially where cooling must be provided but long refrigerant line lengths would be prohibitive.
If you go to Las Vegas, you'll find that many of the local (smaller) hotels use zoned refrigerant systems in their rooms. They use a central condensing unit to serve Japanese-style individual wall-hung air handlers via refrigerant lines. Wouldn't this hydronic concept work even better? And the recessed mounting is more attractive than the externally-mounted fan coils.
So, I think there is a great concept here with lots of potential, but just a little too much hype. You don't need bells, whistles, and extravagant energy-saving claims to promote a good idea to our industry, just good, sound engineering ... and a whole lot of advertising.