Re: Power Supplies, Saving Money, and switching vs. Linear?

[nobody@xxxxxxxxxxxx (Dave Houston)]

"Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:

>"Bill Kearney" <wkearney99@xxxxxxxxxxx> wrote in message
>news:T5qdnVPt76dAc4TZRVn-tg@xxxxxxxxxxxxxxxx
>> > It is almost free once you spend the huge $ for the panel, charge
>> controller
>> > and battery.  However, others in the alt.energy.homepower newsgroup have
>> > calculated that if you have commercial power, the payback on your
>> investment
>> > is something like 18 years.  Not worth it.  No business case.
>>
>> Well, to some the piece of mind that they're not wasting that much more in
>> the way of fossil fuels is worth the investment.  It's not purely a matter
>> of costs.  18 years (and more) of not being yet another fuel consumer.
>
>The solar payback equations are often predicated on unrealistically stable
>electrical rates.   In my neck of the woods, the rates have gone up and are
>going up like never before.  I think the payback will come much sooner than
>in 18 years in the pure business case mode.  As you point out, there's a
>psychological payback, too, from not being so big a part of the overall
>fossil fuel dependency problem.
>
>I'm researching now, but the next house will mostly likely have a
>southern-facing roof comprised of "solar shingles" or a similar roofing
>material.  The high oil prices seem to be stimulating the flow of venture
>capital into solar-based technologies once again.   It may also turn out
>that a spectacular technological advance could radically alter the 18 year
>"pay back" equation.  Who could have predicted the transistor 10 years
>before it appeared and how it would alter the electronic landscape?  I hope
>they make that advance in solar power before I sink $$$ into old technology!

In 99% of the cases I bet the wall transformer is an _unregulated_ power
supply with the linear regulator being internal to the electronic device it
powers. Almost anything that uses a wall transformer with a voltage higher
than +5V is likely to have an internal regulator. In these cases, changing
the wall transformer to a switch mode supply will do next to nothing to save
energy as the linear regulator will still waste the excess voltage as heat.
The "psychological payback" is a delusion. You can get the same "feel good"
effect by spending the cost of the switchmode supply on a cheap bottle of
whiskey.