separate generator and grid tied solar on same house

 I'm thinking about installing a 2KW grid tied PV system on my house.   I
also have a generator that I power the house with when the power goes out.
Let's assume the power goes out and I disconnect from the grid and start the
generator.  If the generator is good enough won't it trick the grid tied PV
system into turning on?   Assuming it does what happens when the PV system
starts making more power than I'm using?  Does it need a place to go?  What
happens if there is no place for it to go?

mike

  Mike Payne wrote:

My understanding is that no home generator is that good. They simply do
not generate a solid enough voltage and frequency. Even if one did at
first, as soon as the PV started to kick in enough power the frequency
or voltage would go out of spec and the inverter would shut itself off.

I think you can get grid-tied inverter/chargers that work the way you
would want. You'll need some batteries but not a lot and it'll work
the way you want.

Anthony

 

Mike Payne wrote:


Just because a generator says it's say 3 kW, doesn't mean it always makes 3kW
worth of electricity. It makes what you actually use. There is no 'unused
electricity' that needs to go anywhere.

Graham

 

  Wouldn't this depend on how and where the
generator connects into the system?

  If I understand "Grid Tied Solar" correctly, the
panels feed a special inverter that supplies power
for the house and also feeds any "extra" power
provided by the panels, but not needed by the
house, to the grid through a special reversible
meter.

  So wouldn't the options be: to have the generator
replace the inverter or have it replace both the
inverter and the grid?  If it were just replacing the
inverter and feeding power to both the house and
the reversible meter, could it be that it can be set
to a certain output level and when the house used
less, the meter would get more?

  This is probably totally wrong, but an explanation
of how and why it is wrong might help both the OP
and myself.

Luck;
    Ken

 

Actually, you've got it just about right.  But paralleling a generator with
the grid isn't so easy.  A grid-tie inverter is designed for exactly that
and has sophisticated electronics to make it produce up to the maximum it
can draw from the DC supply (PC panels).  A typical generator does not.  A
typical generator is designed for isolated service where it just maintains a
near constant voltage and frequency as the user changes the load by
starting/stopping appliances/lights.

Since the 'grid' is also designed to maintain a constant voltage and
frequency as the user changes load, the problem of tieing a generator to the
grid becomes one of, "What if the exact voltage and freq they are both
trying to maintain aren't exactly the same?"  If they are both 'very
insistent' on their own setting, then they fight and the grid almost always
wins.  Running an independent generator in parallel with the grid is
certainly doable, but it's been discussed a lot in other threads so I won't
go into it again here.  Suffice to say, it isn't for the faint of heart.

daestrom