On 23 Jun 2016 at 0:32, David C Brown wrote:

> I am looking into installing solar PV panels on the estate but I am
> struggling to understand how they integrate with the existing power syste=
m./
>=20
> I have a utility supply rated at about 25 kW and would install a solar
> system rated at about 5 kW.  If I now impose a 6kW load how will it be
> supplied?   Simple engineering suggests that 5kw willbe supplied by the
> utility and 1kW by the solar panels.
>=20
> But the instillation company assure me that all load up to the capacity o=
f
> the  panels will be met by them and that I only need to use utility power
> as a top up.   And that excess solar power will be fed back to the utilit=
y
>=20
> How is this implemented?

Hi David,

I've recently installed a 5kW system on my own house, will see if I can hel=
p explain.=20
My system consists of 20 x 250W panels, 10 x dual input grid-connect micro=
=20
inverters. The inverters connect directly to the (in my case 230V 50Hz) AC =
mains at=20
the main switchboard... this is the switchboard where every electrical load=
 in my=20
house is conencted. It's is important to note this is downstream, on the co=
nsumers=20
side, of the utility power meter.

Let's say the inverters are generating 5kW of power (FYI, you should only e=
xpect to=20
see such a peak this at midday on a very sunny summers day with your panels=
 set=20
to the best possible angle). First let's say there is zero load presented b=
y your=20
house, then all 5kW will be "exported" back to the grid (ideally you have a=
n=20
import/export meter fitted and you get credit for this. Now let's say the h=
ouse load is=20
5kW... supply and demand are balanced, zero power is imported or exported..=
.. your=20
power meter indicates zero. Now say the house load is 6kW, 5kW will be supp=
lied=20
by the inverters, the grid supplies the remaining 1kW and your meter should=
=20
indicate 1kW of power is being imported.

Hope this helps. It does take a while to get a handle on power flows etc. E=
xtra for=20
experts: think about what the voltage/current waveforms look like during ex=
port vs=20
import.


--=20
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