[QCWA] Alternative energy requirements.

[Jeffrey D Angus]

I have an Empire 15 KW generator set. It is powered by a
Wisconsin VF-4D 25 HP gasoline engine.

Roughly it will consume $400 of regular gasoline running
8 hours a day for a month, compared to $120 from TXU
for the utility power.

That's also roughly 23 five gallon cans of gasoline.

The Honda EX4500S will consume about 1/3 of that over the
same time period.

$130 worth of fuel and about eight cans of gasoline.

There are two things to consider in sizing alternate energy:
1. Peak Demand
I.e., the HVAC, one or both at the same time along with any
other "have to have" loads.
2. Long Term Totals
i.e. Refrigerator, Freezer, security system and communications.

Generator sizing is based mostly on peak demand. So you
minimize that by running high power loads sequentially. For
example, AFTER the air conditioning has cooled off the house,
The you plug the refrigerator and freezer back in to cool off.
Then switch to the kitchen stuff, microwave, dishwasher etc.
Then finally lighting and entertainment for the night. ;-)

Solar, and wind, power on the other hand is limited by the
size of both the collection and storage capability.

As a conservative example, the HVAC. That's going to be
about 15 amps at 240 volts. 3600 watts and probably
closer to 4500 to handle the starting surge currents.
But the total is 7.2 KWH for running one then the other
for an hour apiece to cool down the house. If you only
have 10 KWH of storage, well, you've just used that up.
And if you've only got 5 KWH of collection, you get to
pick which end of the house gets cooled off.

The other thing to consider if "full time loads" that will
add up. Such as the phone switch, network routers, and
the security cameras and alarm system. While they may
only total up to 500 watts, the "over time" requirement
is 12 KWH for a 24 hour period.

If you figure 8 hours of collection time, that translates to
almost  (12 + 7.2)/8 or 2.5 KW collection capability and
20 KW storage capability.

This doesn't include anything else like the refrigerator,
freezer, lighting, computers, printers and all the chargers
to keep all the portable stuff running.

Additionally, you'll have to consider things like the washer
and drier, garage door opener and any other things like
the microwave and toaster ovens.

Also, you have to consider the inverter power capability.
Even if you have 20 KWH of storage, you will need at least
a 10-15 KW inverter to run the HVAC stuff for two hours.

Lastly, a final consideration is what happens on cloudy or
overcast days when the collection ability is reduced?

The good news is that if the utility company has given you
a "smart" meter, you should be able to get a "usage" chart
from them showing not only your total usage but your
peak usage per day as well. That will make the calculations
a lot easier to figure out.

The other question is "Do I want enough power to run the
house completely?" or "Do I want to just reduce my cost
at the end of the month?"

In my case, due to extremely limited funding, I would have
to go with "Do it yourself" system cobbled together on an
"as I can acquire the pieces" basis and rely on the generator
for peak loads, such as the HVAC system. And just hope
for a reduction in my monthly bills.

Hope this bit of insight helps with deciding what you want
or need for alternative energy.

Jeff
wa6fwi-1.0