No Export / Export switch on a small solar system

[croftrobin]

If you had a small solar system which was Grid tied and saved say 25% of the monthly Pea cost.  So your monthly bill dropped from 4000 to 3000

 

You had a constant base load of  1 domestic Fridge, 1  freezer, 1 shop fridge and 1  modern 26 btu air con on every day during daylight hours.

 

When using this switch mode in "No Export" mode does that mean you are not even supplying power to supplement the local load?

 

 

[Crossy]

Grid-tie inverters will produce the maximum power available from the solar input. Physics ensures that your system will always supply the local load first with any excess going to the grid (disc-type meter goes backwards).

 

"No-export" means that the inverter will reduce its output to only cover the local load so you don't send any excess energy to the grid (meter doesn't go backwards).

 

 

[croftrobin]

Thanks for ther clarification

 

Is the the "No Export" option always  available on grid tied inverters, say for example your meter is changed from analogue (which go backward) to the new

digital meters which can be may be set to charge for inputs also.

 

or is this something you yourself have come up with?

 

[Crossy]

Just now, croftrobin said:

Is the the "No Export" option always  available on grid tied inverters

 

Sadly, it's not, although an increasing number of inverters are being supplied with the necessary CT (Current Transformer) and internal gubbins so that they can do it.

 

It's certainly a wise investment to pay a little extra for an inverter with the facility.

 

The ESP8266 based system we use to automatically enable/disable export on meter-reading days is discussed in the Solar Car Port thread.

 

 

[007 RED]

@croftrobin  Just to illustrate the point that @Crossy has made above regarding the CT, I have attached below a graph taken from my inverter monitoring facility on the day that the meter reader came on the 16/12/22. 

 

The CT was switched into the NO EXPORT mode in order to stop any excess power being fed back into the grid and making the meter disc spin backwards.  Something that must be avoided at all cost when the meter reader comes.

 

As you will see from the graph below with the system in NO EXPORT mode, the blue production line never exceeds the red consumption line.  In fact the production line endeavors to mirrors the consumption line.

 

The large consumption spikes (e.g. 2.5kW) during the early afternoon were as a result of my better half baking bread.  Because my small scale system normally produces around 1.2kW maximum with good sunshine, the inverter could not match the consumption, hence the consumption spikes become very noticeable.

 

FYI.... When I say that the CT is switched into the NO EXPORT mode, I mean literally that.  Between the CT and the inverter I have a simple 'light switch' as shown below.  With the switch in the 'open' position the inverter can feed excess power into the grid.  With the switch 'closed' the CT can then communicate with the inverter (e.g. power consumption) and prevent the export of any excess power.  Simple, even my better half can operate it when necessary.