Morgans wrote:

"Dylan Smith" wrote

Technology to make AC from DC, DC from AC, high voltage DC from low
voltage DC and all the combinations has existed for decades. It's very
basic stuff. I've made 1000 volts DC from 12 volts DC. It's not even
hard to do.

Right, not hard; just expensive and inefficient as hell, and in some cases,
almost unusable.

Most of the home level inverters are what they call "modified sine wave"
inverters. All that says is that the innards of the inverter cut the power
on and off rapidly, so if you read the voltage, it rises and falls in a
choppy square notched "sort-a-looks-like-a-sine-wave" if you squint real
hard.

The more sophisticated ones are more than three times the cost, which makes
them very expensive.

The modified sine wave converters will power most stuff without permanent
damage, but don't try to use your DeWalt cordless drill battery charger.
Anything that reads like a high voltage until you put the load on it will
fry, and it says so in the inverter's instructions, if you take the time to
read the fine print. Don't ask me how I know that.

They also put out a good bit of heat, and guess what. That heat is power
going out the window, in a big efficiency loss. Oh, and don't try to power
a refrigerator, or AC, unless you really want to see a big time efficiency
hit. They don't work very well, at all.

So, the long and short is that if you are using battery or Solar DC, you had
better be using as many DC units as at all possible, or your batteries will
not last very darn long.

I'm not against Solar, but everyone needs to know the limitations of doing
so. You need a specially designed system using mostly straight DC, or lots
of money, if you expect to get much useful power out of the system.
--

You do realize that most computer rooms and some entire buildings
have battery backup and huge inverters for power failure protection?

These are true sine wave inverters, are quite efficient, regulated, and
phase synchronized to the grid so switchover is transparent.

However, you are correct about the cheap Chinese junk you get at places
like Pep Boys; they put out crap wave forms, are inefficient, and
seldom have regulated outputs.

And you are correct about the cost; decent inverters cost a lot more
than the junk.

There is no potential technology to lower the cost of such inverters
other than economies of scale, and the installation and maintenance
cost of such inverters is usually ignored by solar energy proponents.


--
Jim Pennino

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