Missing mode: "Charge from PV"

[user74656]

First of all: Thank you so much for the great work. I really think that, with this project, we are at the cutting edge of a revolution in the way we use energy.
I just installed EOS_connect and it's working so far :-)

As I understand it the main output of the optimisation is:

• Charge from Grid: All the power from the PV plus an extra charger goes to the battery; the household is powered by the grid.
• Avoid Discharge: The power from the PV goes to the household and surplus goes to the battery. If the PV produces less than the household needs, the rest is consumed from the grid.
• Discharge Allowed: The power from the PV and the battery goes to the household. If that is not enough, the rest is consumed from the grid.

I think there should be another mode, or am I missing something?

• Charge from PV: All the power from the PV directly goes to the battery, the household is powered by the grid
  Charging directly from the PV has the advantage of missing the conversion from AC to DC and is therefore more efficient

[a8291]

This option in the end is handled by your inverter and the logic you build. I don't see there any point integrating that. And as far as i know there is no such option - at least with my sungrow inverter.

[ohAnd]

hi @user74656 ,

and thanks and nice to hear that the installation runs fine.

(btw. with this trigger it will be nice if you could share your experiences for the first start at 🛠️Installation & Configuration to show others it is no rocket science and so there more people feel encouraged to be part of "the cutting edge of a revolution in the way we use energy" )

Now to your understanding and my comments (in addtion to @a8291):

Charge from Grid: All the power from the PV plus an extra charger goes to the battery; the household is powered by the grid.

yes and no - no for household is powered by grid - you mix up sources and "sinks": grid and pv are in this case sources and household and battery "sinks" so correct way is battery AND household will be supplied by grid AND PV
imagine the use case house needs 0,5kW from the sources and battery needs be loaded with 5kW and PV delivers in this scenario 3 kW - so 2,5 kW are needed from grid - what is here the source for the household - espicially when it drifting e.g. PV increses to 5kW ...

Avoid Discharge: The power from the PV goes to the household and surplus goes to the battery. If the PV produces less than the household needs, the rest is consumed from the grid.

that's right ;-)

Discharge Allowed: The power from the PV and the battery goes to the household. If that is not enough, the rest is consumed from the grid.

Yes and No ... no = 'the rest is consumed from the grid' either you have the ability to supply via battery or not (due to SOC at minimal) - means in this mode the battery is the supplier - if PV is given in height of needed houshold power then the battery will not be drained ... if it's higher same as surplus, if it is lower then the battery will be drained until empty AND then the household will be supplied by the gird - in this mode

so ...

Charge from PV: All the power from the PV directly goes to the battery, the household is powered by the grid
Charging directly from the PV has the advantage of missing the conversion from AC to DC and is therefore more efficient

the conversion efficiency is ok ... but why it makes sense to load to the battery when you have a direct consumer (household) running for which event later you want store the energy (lates at this point you have the conversion thing + the efficiency factor of storing and retrieving energy from battery) and want to pay for the current consumption of the household via grid

and as @a8291 already mentioned I also don't know a possibility with my fronius to only charge the battery with pv and don't supply the household ... as described above at this point I see no advantage -

But I really want to understand, what is you target here with this option! (let's assume there are some tricks to do that)

[user74656]

I have a DIY solution with a sepparate AC Charger, Inverter and Battery Charger controlled by homeassistant

Scenario:

The ac charger has an efficiency of 90%.
The efficiency of the battery (ratio of energy_out to energy_in) is 80%.

At midday, electricity costs 0,30€/kWh and in the evening 0,40€/kWh.
The PV produces 1 kWh at midday.
I need 1 kWh at midday and 2 kWh in the evening.

Option A, avoid discharge:

Supply the house with PV at noon, draw 2 kWh from the grid in the evening for 0,40€/kWh. Total cost: 0,80€

Option B, charge from grid:

Supply the house with 1 kWh * 0,30€/kWh = 0,30 € of grid electricity at noon, charge the battery with PV and grid electricity and draw 2kWh from the battery in the evening.
Energy needed from the battery in the evening: 2kWh = 1kWh * 0,8 + 1,66kWh * 0,9 * 0,8. So we need to charge 1,66kWh * 0,30€/kWh = 0,50 € from the grid.
Total cost: 0,30€ + 0,50€ = 0,80 €

Option C, charge from PV:

Supply the house with 1 kWh * 0,30€/kWh = 0,30 € of grid electricity at noon, charge the battery with PV electricity.
Draw electricity from the battery in the evening. Available Energy from the battery: 1 kWh * 0,8 = 0,8 kWh
Draw remaining electricity from the grid: (2 kWh - 0,8 kWh) * 0,40€/kWh = 0,48€ Total cost: 0,30€ + 0.48€ = 0,78€