On 12/15/2016 10:40 AM, jim bell wrote:

   From: Mirimir [1]<mirimir@riseup.net>
   >See
   > [2]http://www.lowtechmagazine.com/2016/04/slow-electricity-the-return
   -of-low-voltage-dc-power.html
   What is said there is logical, but it is impractical.  Society has far
   too much invested in AC transmission systems (including those wires
   already installed in buildings) and consuming devices to expect even a
   small switchover to DC for the vast majority of applications.  In
   Tesla's (and Edison's) day DC was impractical, because there was no
   efficient, reliable way to convert low-voltage DC to high-voltage, and
   back.  (motor-generator sets were the closest to that.)

   The REA (Rural Electrification Administration/Act) attempted DC power
   on farms around the the US in the 1930s, but my understanding of one of
   the big problems with DC power is voltage drop, which isn't critical
   with AC powered devices but cause the need for 'stations' set up every
   so many miles to boost the DC voltage again.

     In the 1930s, the provision of power to remote areas was not thought
     to be economically feasible. A 2300 volt distribution system was
     then used in cities. This relatively low voltage could only be
     carried about 4 miles before the voltage drop became unacceptable.
     REA cooperatives used a 6900 volt distribution network, which could
     support much longer runs (up to about 40 miles). Despite requiring
     more expensive transformers at each home, the overall system cost
     was manageable. [Citation needed]" (<< Not gonna find verification,
     therefore "Fail" -Rr)

   Ps.

     Wiring was performed using type NM (nonmetallic) sheathed cable,
     insulated with asbestos-reinforced rubber covered with jute and tar.

   I lived next to a house in the Pajaro Valley (Ca) post-Loma Prieta
   earthquake when I was still a Ham radio operator, that had remnants of
   that wiring, and could see it from my radio room. One evening, while
   SWL listening, the roof of that lovely old 2-story farmhouse caught
   fire and the place burned to the ground while the Aromas Volunteer FD
   watched helplessly. The earthquake had knocked the insulation off the
   wires mounted on ceramic knobs tens of decades later and presto
   flamo... The owner's peacocks took days to round up as they scampered
   around the strawberry fields like little feathered streaks. That
   beautiful 2 story farmhouse complete with windmill was replaced by an
   (ugh...) Mobile home.
   [3]https://en.wikipedia.org/wiki/Rural_Electrification_Act

   In contrast, the AC transformer was very simple, reliable (no moving
   parts), and eventually could be built to step up to 760 KV (and perhaps
   higher), enabling transmission of many hundreds of miles, and then down
   to 240 VAC, split to 120 VAC.  That's why Tesla was right, and Edison
   was wrong.  Edison could never have wired the country with any
   realistic DC system.
   Today, converting DC to  DC is far easier, at least for low voltages,
   see the large set of chips made by Maxim.
   [4]https://www.maximintegrated.com/en/products/power/switching-regulato
   rs.html
   But it is virtually as easy to convert rectified AC to low-voltage DC,
   with these same kinds of chips.  So there is very little reason to
   abandon the modern AC distribution system.  Even a local solar array
   generates a varying voltage that will have to be switched to a specific
   DC voltage to charge batteries, which is easy to do.  And if you hope
   to sell your excess of power to the grid, it will have to be converted
   to AC anyway.
           Jim

References

   Visible links
   1. mailto:mirimir@riseup.net
   2. http://www.lowtechmagazine.com/2016/04/slow-electricity-the-return-of-low-voltage-dc-power.html
   3. https://en.wikipedia.org/wiki/Rural_Electrification_Act
   4. https://www.maximintegrated.com/en/products/power/switching-regulators.html

   Hidden links:
   6. http://www.lowtechmagazine.com/2016/04/slow-electricity-the-return-of-low-voltage-dc-power.html
   7. https://www.maximintegrated.com/en/products/power/switching-regulators.html