[PLUG-TALK] Smart power meters

Denis Heidtmann denis.heidtmann at gmail.com
Sun Oct 13 09:30:40 PDT 2013


On Sun, Oct 13, 2013 at 12:49 AM, Keith Lofstrom <keithl at gate.kl-ic.com>wrote:

> On Fri, Oct 11, 2013 at 10:09:11AM -0700, Denis Heidtmann wrote:
> > Yikes, this is getting complicated!  There are reports (
> > http://sagereports.com/smart-meter-rf/,
> >
> http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001021126
> )
> > which are at opposite ends of the controversy.  Issues such as
> > unpredictable duty cycles of the transmissions, effects of unpredictable
> > reflections on exposure, and finally debates about non-thermal biological
> > effects of non-ionizing radiation make coming to any reasonable
> conclusion
> > difficult if not impossible.
> >
> > One of the reports mentions the future use of rf transmitters in
> electrical
> > appliances to send power use information to the smart meters.  This is
> news
> > to me.  Do modern appliances have such things?  I guess I am a Luddite.
> >
> > Normally I would want to err on the side of caution.  I rarely use a cell
> > phone, I removed our wireless home phone, but still use a wireless router
> > (convenience v.s. caution conflict).  There is a smart meter on my house.
> >  What to do?  And what to tell my relative?
> >
> > -Denis
>
> Cell phones blast up to a watt of power right next to your head.
> The average (assuming a close tower) might be 100 milliwatts (WAG).
>
> Zigbee packets (one of the protocols used for smart power appliances)
> uses less than 500 microjoules.  If a hypothetical smart appliance
> is sending status to a base station with every state change, say a
> water heater turning on or off, it might make a few dozen such
> signals a day, at many meters distance.  Inverse square law applies.
>
> So ... exposure from 10 minutes daily of cell phone / smart phone
> exposure?  100mW * 600s / (0.1m)² -> 6000 J/m² per day.  We can
> assume that the effects, if not zero, are small enough that cell
> users live long enough to pay their bills.  I imagine we would
> all notice if these devices killed every user in less than fifty
> years, so the minimum lethal long term exposure is greater than
> 100 MJ/m² lifetime dose.  Probably far, far larger.
>
> Exposure from 24 state change packets per hour, 576 packets per
> day, from all your smart appliances, an average of 5 meters away?
> 576 * 500μJ / (5m)² -> 12 mJ/m² per day, 2ppm of the cell phone
> dose.  A 50 year dose of that is 200 J/m² (not MJ) lifetime dose.
> 2ppm of the lifetime cell phone dose, 1/500K, which kills far
> less than 100% of cell phone users.
>
> Meanwhile, the death rate from an additional hour of television
> watching is about 1/200K, extrapolating from a 104/100K annual
> death rate from watching 2 additional hours of television per week.
> (see http://tinyurl.com/DeathbyTV ).  So, your concerned relative
> can watch half an hour less of television, one time, to more than
> compensate for a lifetime radio energy dose from a house full of
> smart appliances.
>
> If you want more accurate numbers for all these things ...
> measure them!  Assuming you can find a home with smart appliances
> in it (Intel may have a demo in the area), ask a well-equipped
> ham radio operator to help you measure the actual packet energies.
> Keep in mind, though, that many of these are 80 year olds who've
> been around kilowatt transmitters all their lives.  They will
> probably say all the concern about consumer RF exposure is
> neurotic nonsense.
>
> Nonsense or not, those of us with the ability to read, think,
> measure, and calculate have a responsibility to do so, not
> parrot third-hand claims that may have been pulled out of
> somebody's ass.
>
> Keith

I appreciate that cell phones expose users to much larger doses than the
smart meters and appliances could ever reasonably do.  However, death is
not the only possible negative outcome due to exposure.  And the
possibility of non-thermal biologic effects perhaps makes the 80 year-old
ham not a good measure of safety.

Making a measurement around a smart meter does not cover the worst case.
 It seems that the systems use some (2-5%) meters as collection points for
data from neighbors.  Getting the power company to say what is the
worst-case duty cycle and power level has been nearly impossible.  Why is
that?

But my original reaction to the hub-bub about smart meters was to classify
it as "neurotic nonsense".

-Denis
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