What Does an Inverter Do?
An inverter
changes one kind of power [usually DC (direct current) from
batteries, solar panels or windmill] to AC (alternating current) power
that matches your utility grid.
Choose an Inverter to Meet Your
Peak Power Needs
You may have already calculated what power
output is necessary to live your
life style. If you choose an inverter that won't support your life
style then you must at the very least choose a size that will sustain
your food safety and emergency lighting during a power outage.
Otherwise, when the electric utility fails, you're dead in the water as
far as a renewable energy system is concerned.
If you choose an inverter to just
transfer power as it is being generated by solar panels, and/or
windmill max power output, there's no backup for a utility power
outage. In southwestern Virginia when hurricane Hugo hit, we were out
of power for 5 days and couldn't even pump gasoline to run a generator.
Talk to the people from New Orleans (Katrina) or from the floods of
Fargo, ND. Not to mention the north
east electric grid power failure. Hey, "Never design a
dwarf!" Here's some more info on power grid
failures.
Max Emergency Output Power Needs
I live in the country. Here's the game I play when the utility
power goes out. First thing I do is turn off all the 220 circuits
in my two circuit breaker boxes. These include base board heat,
bathroom heaters, water
heaters, water pump, clothes dryer, and electric stove. My 110 circuits
include refrigerator, freezer, coffee maker, micro wave oven, hot
plate, floor fans, computers with UPS, TV, toaster, wash machine, space
heaters, bath room exhaust fans, Monitor Heaters (computer controlled
fuel oil
heater with fan) and lights. All the 110 circuits are switched except
the
refrigerator and freezer.
I need inverter capacity to run the
refrigerator, freezer and water pump. Because I never know when they
will kick in and they're not synchronized. I need additional power for
lights and what ever else to sustain an emergency life style like hot
water
for bathing, heat for cooking etc. Most can be rationed and rotated to
minimize peak power.
Refer to Current Power Usage to review
how to make these
calculations.
Your whole family needs to be intimately
involved with the conservation of power usage in order to prevent
overtaxing your system. Should you overtax your inverter too frequently
or to much, your inverter will fail and you'd be "out of luck"
for
any usable renewable energy.
"Never design a dwarf!" Remember Murphy's Law,
"Your inverter won't fail at a convenient time".
If your inverter is wired into the grid system through a circuit
breaker, it can be protected from damage when the electric utility
fails. It will require a manual reset in the dark unless you have
a separate emergency light that comes directly from the inverter and
located at the circuit breaker box.
Match Battery Bank Input
Your battery bank may be a 12 volt system or 24 or something else. Make
sure you select an inverter that accepts the output of your battery
bank voltage. Remember the higher the voltage the lower the current for
the same power transfer. And the lower the current the lower the power
loss in the wiring. Conserving power loss in your system raises the efficiency of your system
and gives you more power for your life style. First you design the
system that works for you. Then you tweak the design to make it more
cost efficient.
Trade
- Offs
1. If you want less weight, run
higher voltages in your system. After all:
power = voltage x current
(V*I)
Lower
current can use lighter weight wires for the same power loss during
power transmission.
2. If your inverter is used only to
deliver power for net metering, you may be power neutral but you may
not have enough capacity to sustain yourself during a power outage
without a supplementary source like a gasoline powered electric
generator to make up the difference. Even then, you will need a switch
to isolating yourself from the electric power grid.
3. In most cases, the greater the
capacity of an inverter the higher the cost. Consider the differences
between a 2.5 kw and a 5 kw inverter. They're $249 for the
2.5 kw and $449 for the 5kw inverter. You'll need to shop around to get
one to match your system and also meet you need. Up front money may be
your biggest trade off against probability of grid failure
consequences. Just remember, "Murphy was an optimist."
Load
Balancing
All-in-one
[Charge Controller
- Inverter]
|
