oil supply sigint

[Razer]

On 12/15/2016 10:40 AM, jim bell wrote:
>
>
> *From:* Mirimir <mirimir at riseup.net>
> >See
> > 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.

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.
>  https://www.maximintegrated.com/en/products/power/switching-regulators.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

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