Too_Many_Tools wrote:

I would agree but an VFD that is unnecessary is a current draw that is
not needed.

Like any system, one needs to plan a workshop as a whole.

At this point, I could go single phase, 3 phase or DC motors on on all
my machines. One of the reasons why I started this discussion was to
make that decision based partially on the experiences of others who
have hopefully gone before me.

TMT

I've been following this thread with some interest and now have some
thoughts and comments to add to it.

I may have missed something along the way, but I don't recall you
specifying what type(s) of alternative energy sources you have
available. This makes quite a difference in determining the best
options.

As an example, if your alternate source(s) provide mechanical power such
as found with water power, wind power, or a solar boiler driving a
turbine or steam engine, then air power could be quite advantageous.

A source of mechanical energy can directly drive a compressor head,
saving the extremely inefficient conversions to electricity and back.
Compressed air is easy and economical to store in large volumes and is
free from the chemical hazards of batteries. Useable service life of
compressed air tanks is much higher than batteries as well.

In addition to the obvious air tools, compressed air can also be used to
power things such as refrigeration if you use the belt driven type
refrigeration compressors.

Those mechanical energy sources can also simultaneously drive electrical
generators to charge conventional batteries for loads such as lighting.
Battery charging for cordless tools is no less efficient that the
charging of your "regular" battery string, as long as the charging is
limited to peak energy generation times.

The efficiency of converting DC from your battery string to AC so you
can use conventional appliances is fairly good with modern inverters.
The conversion efficiency also improves when you use a higher voltage
battery string since inverters switching higher voltages at lower
currents will have lower resistive / heat losses.

Solar PV conversion efficiency is incredibly low to begin with and PV
cost is high so if that is your only energy source you really do need to
watch every miliamp. Of course, even with that inefficiency a solar PV
panel charging batteries for your cordless tools is just fine as long as
it has the capacity to keep up with your usage.

For items like welders that require huge gulps of power it's really
difficult to get away from an IC engine / generator for practicality. A
decent welder / generator can serve two needs and may be the most
practical solution.

If you've got really good water power available you could probably use
it to drive the head from an engine driven welder. A DC inverter type
welder could probably be modified to accept DC from a large battery
bank, but that would require you to have a fairly high voltage battery
string to be practical.

Someone else posted about the differences in energy needs of a shop vs.
home. They had more or less the correct idea, but got their terminology
a bit out of whack. A shop has mostly high peak energy loads at low duty
cycles and a home has mostly low peak loads with high duty cycles. The
total energy consumption over the course of a day could be similar
depending on how busy the shop is.

Pete C.