Panasonic’s Thermoelectric Hot Water Pipes Generate 7.5 Watts Of Power Per Foot.

Panasonic is designing an improved system to generate thermoelectric power by making it more efficient. Thermoelectric power is created via temperature differences – in this case, between the hot and cold water running through your house. Attempts to generate thermoelectric power in the past have been unsuccessful due to the amount of heat lost in the process.

The video pretty much explains how Panasonic’s thermoelectric tubes work. [DigInfo]

Somewhat related article: 100-Megawatt Power Plant via Variations in Ocean Temperature



  1. GreenEngineer says

    in this case, between the hot and cold water running through your house

    This is silly. The hot water in your house was heated by a (usually gas-fired) water heater. Taking heat out of the water with this device (at a loss) just means that you have to put more heat back in (at another loss).

    Violations of the second law of thermodynamics are not Jubbling.

    In a residential setting, you could in theory use warm wastewater as a heat source, and the makeup water going to the water heater as a heat sink. (This would have the advantage of pre-warming the incoming water). But this can be done much more simply with a drain-line heat exchanger. (
    You don’t get any electricity out of a drainline Hx, but I suspect you would not get very much out of a thermoelectric system on the drain line, either. The drain water will be warm but not hot (due to mixing with cold water) which means the electrical generation efficiency will be crap.

    The stated purpose of this device is to do energy recovery from waste heat streams, e.g. at a factory. This is a much more sensible application, both because you’re capturing true waste and because industrial waste heat can be quite hot, which improves your electrical output.

  2. I like your comment more than I like our post.

  3. GreenEngineer says

    Well, thanks.

    In general, when being presented with a new energy technology, you should always ask yourself “where is the energy coming from”. Energy cannot be created or destroyed, so it always has to come from some other source of energy.

    If the answer is “the sun” either directly or at a remove (e.g. wind, which is ultimately solar power) then you’re (probably) good. If the answer is “a waste stream” and there is no higher and better use for that waste, again, you’re good. But if the energy is coming from some other energy/heat source which itself is driven by fossil fuels, then you’re looking at a boondoggle.

    Of course, it’s never quite that simple either. Consider corn ethanol: the energy in the ethanol comes from the sun, so that’s good. But the energy to turn corn into ethanol (especially the distillation step) comes from natural gas. That’s why ethanol has such a lousy EROEI. (Corn ethanol energy return on energy invested is 0.8 – 1.5 depending on who you ask; but anything less than about 4 is pretty pointless IMO so the difference doesn’t really matter.)

  4. Thanks Brent. I knew it had to be “normally wasted” heat to make sense. I should’ve gone with my first choice and just posted the video. (BTW: Your second comment is also post-worthy!)

  5. GreenEngineer says

    Glad you liked it. The issue(s) of EROEI and net energy (really the same issue, looked at via different numbers) is central to the challenges we face now. While net energy does not reflect the entire energy picture (there are also issues of energy quality, and fuel transportability, among others) it does provide a very powerful lens to understand why traditional economic growth has become so hard to achieve on a sustained basis, and why ultimately the growth-based economy needs to seriously readjust its expectations.

    Here are two good articles on the topic.

    With regards to the second article, the author notes that one option is to hope for a technological breakthrough that allows higher energy return from renewables. While we will continue to see incremental improvements in renewable net energy, I argue that a dramatic improvement in these figures is unlikely, if only because the ultimate energy source – the sun – is relatively diffuse. It’s much easier to achieve high EROEI with concentrated energy sources – fossil fuels are basically distilled sunlight. It’s much easier to get drunk on whisky than on lite beer.