It was minus 9 Fahrenheit with a minus 37 wind chill Wednesday morning. I also paid the electric bill for January today and these two things have focused my attention on just what will I do about the costs to stay warm. Yesterday we looked into how the clothes dryer could be lots less expensive to run. Today we’ll have look into one of the leading ways to crush the hot water segment of the expenses.

Craig Neilson at WorldChanging interviewed Rod Innes, technical director of Vaportec, Ltd. of Napier New Zealand. Vaportec is a patent holder for improvements to the heat pump conductor tubes and are talking up the idea of the heat pump to drive a hot water heater. Now after the furnace and air conditioning the hot water heater is the largest user of energy in the home’s mechanical systems. Depending on the variation of outdoor ambient temperatures and the demands your family makes for heated water, you might be located where the hot water costs meet or exceed the heating and air conditioning portion. But no matter where, the hot water bill is a major issue for everyone.

The heat pump does one thing – moves the heat energy. For heating, a home heat pump just takes some warmth outdoors and brings it inside or to air condition, moves the heat inside back outdoors. While a resistance element is thought to be 100% efficient at the terminals and can put nearly 100% of the used joules into the air or water flowing by, that isn’t the smartest use because a heat pump can be up to 4 times as effective at moving heat as a resistance element is at simply transferring it.

Mr. Innes points out some New Zealand based numbers on the savings a heat pump could bring to a water heater. In domestic uses, i.e. households water heating equals about 45% of domestic demand. The local heat pumps offered for sale there now save about 70% compared to resistance heating water. Mr. Innes points out that the numbers are roughly the same in Australia, and one could expect that the effect would apply essentially everywhere. Both countries enjoy comparatively mild climates over their whole area.

But what focus me is that I have a heat pump in my home that is much less expensive to run than a natural gas or electric resistance furnace. I’m vividly aware of the difference it can make. The puzzle for me and almost everyone else is just what share of the gas or electric bill is for the hot water? To get a good answer I’d need a second meter. But in my location the water share can be nearly 50% over a year so I’m tuned into the chance to change.

Vaportec Spirex Tube

Mr. Innes isn’t finished. The company has another innovation, a conductive tube that carries the transfer fluid, which has had special treatment to introduce a “twist” that effectively increases the surface area that transfers the heat energy in and out of the tube. Shocking to read is the patented “twist” adds another 300% of conductivity to the tube.

Now I’m really paying attention. Then I get this: by introducing a twisted rod in the annulus of the tube that is turned the other way, another 20% gain is observed. Here is the patent link, the U.S. issue date was January of 2004. Plus a cool video of their technology.

With six years of development effort to arrive at the efficiency gain done in association with The University of Auckland School of Engineering this seemingly simple tube is more appropriately called a helically corrugated heat transfer tube. Its been known for a long time that enhancements to the conductor tube would have increased effects in efficiency. What stands out from the New Zealander’s work is the patent on how to make such a tube economically.

To really grasp what goes on inside I suggest a look at the “History of Spirex” link and go to the segment titled Fundamental Temperature Transfer Considerations.

How available are these? Not many yet. To quote, in the U.S. there are these basic types, integrated with, or separate to the holding tank with the heated air either exhausted outdoors or optionally kept inside. This allows the cooling of the air to be added to the air conditioning or dumped when heating. Then there are the “add on” units to modify an existing water heater. Some of these are 110 volt so a handy homeowner could install one easily. However, these shed the “heat” indoors so they are especially practical where air conditioning is the main air handling concern.

I’m going to look for a Spirex tubed unit. But awakened and wishing to be warmed cheaply might preclude waiting as there looks to be over $500 a year saved here at my home even if I use the lower numbers. As much as I would like to have one that’s more efficient, it’s a lot of savings right now and I’d be even in less than two years, plus it would cut down on the summer A/C expense because I’d get the cool from the incoming water put into the home’s air.

I’m glad I looked into this. Might save enough to pay for a lot of the cost to charge up a car someday.

Easily found U.S. manufacturers:

Beyond Pollution, Inc., Applied Energy Recovery Systems, Nyle International, Trevor Martin, and Aqua Products.


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