Continuously sell energy to the grid

1

Hello.
I’m new to openems but I think this is a great and very interesting project.

I would like to use openems to continuously sell energy to the grid (maybe with a dynamically adjusted feed in rate). But let me begin with what I already have installed and why I want to do this.
I have a PV plant with a maximum of 35kWp DC power, a 29.9kW Goodwe hybrid battery inverter and a 66kWh BYD battery pack. Since the Goodwe inverter is very powerful, the whole house is wired to the backup output. So, if the grid power would be gone and the battery has enough energy stored, the house is still powered.
The default configuration of the Goodwe inverter is to maximize the self-consumption.

Now, the situation is that I’m almost always powered by the Goodwe inverter and I don’t need any power from the grid. That’s good. But the used energy from the battery is not very much (just 15% over night). And every day when the PV is starting to produce power, the battery is immediately fully charged (e.g. today the battery was fully charged at 9:00 am).
Usually, I would now sell the additional produced energy to the grid. But I’m very limited how much power I’m allowed to feed in. Right now, it is only allowed to feed about 1kW to the grid. The limit will be increased to probably 4kW. However, this limit sucks!

Therefore, I had the idea to continuously feed in with 1kW. But this setting is not possible with the Goodwe inverter itself. So, this is where openems comes into play.
I tested openems with simulated components and the easiest way to achieve this configuration would be to have the “Ess Balancing Controller” configured with a target grid setpoint of -1000W.

I think this will work for the beginning. But later, when I’m allowed to feed in more than 1kW, it would be nice if I could change this setpoint dynamically. E.g. with the SOC of the battery. For example I would feed in with 4kW when the battery has more than 50% SOC and if the battery is bellow 50% I would like the setpoint to be 0W (no feed in to the grid any more).

Would such a configuration be possible with openems. Eventually with already existing components? Or how would you suggest to implement such an algorithm? Is it possible to dynamically change the setpoint of the balancing controller?

Thanks,
Andreas

2

Maybe have a look at the GridOptimized Controller :slight_smile:

3

Hi Andreas and welcome to the OpenEMS Community,

What you are planning to do is not (yet) legal here in Germany, but you could possibly adapt my prototype developments for upcoming German legislation:

See also my latest Video with Felix Goldbach on EES Europe Exhibition this May in Munich.

In principle if you adapt (and improve) the existing code, you could achieve an optimized energy schedule that predicts your local production and consumption and evaluates when and with how much energy to discharge the battery to the grid.

Regards,
Stefan

4

Thank you very much for pointing me in that direction. I will have a look.

My installation is located in Austria. I’m not sure but I don’t think we have that much regulations like in Germany at the moment. Only thing we have is that we are very limited to how much power we are allowed to feed back into the grid. And for every kW we want to do more, we need to pay.

To be honest, I don’t really like it to pay some extra fee for climate-friendly behavior. Therefore, I would like to solve it that way ;-).

Thank you again.

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5

There was a lawsuit in Austria where some fees had to be paid back:

But I’m not sure if it is legal to sell power from the battery.

I have with OEMAG IMS Market communication, meaning only energy consumption/production values per day are communicated.

With entering an EEG, erneuerbaren Energien Gemeinschaft https://energiegemeinschaften.gv.at/ market communication will probably change to IME, energy values for ever 15 minutes.
Then it will be visible that energy is should in the night.

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6

I just found the forum and are happy that someone else asked the question before.

Could we configure a system to simply send an amount of Watt per hour to grid if battery is >50% and possible if sun is expected for tomorrow.

The reason is that power going to grid passes by our heat pump first before going to the grid. So I’d like to continuously send some power to the grid to cover the heat-pumps base consumption.

Any ideas?