Here’s an issue with DESS that I have for tomorrow. The whole 24 hours sell price is at or below 0, so what DESS decided to do is to curtail the solar and not charge the batteries, and the day ends with empty batteries. This is probably because battery charging costs money (I have set kWh price of battery to 0.03Eur). But in reality batteries will degrade faster with age than because of cycling so it does not really cost anything to charge from solar. In other words, it decided to turn off MPPTs rather than charge the batteries which does not make much sense.
So now I must switch to regular ESS mode during that day or add a huge consumption forecast at the end of the day. Otherwise it will charge a bit during mid day so that there is just enough for self consumption after sunset until midnight. I will then end up with 21% charge when minimum SoC is set to 20%
(The Idea is, that you could now charge your battery from grid and earn money for charging - but if you combine that with a grid2battery restriction (?) , it doesn’t seem to make sense)
I know this setting exists, and no, I have not turned it on. It can not be used in my case as grid fee per kwh is fixed and is always larger than the negative electricity price. At least I haven’t seen electricity price go lower than a couple of cents, but the fee is more than 5 cents.
And in Energy graph it is clearly visible that it will be charging a little and the rest is Solar to Consumption not Grid to Consumption, so solar is not switched off. It will be producing only for self consumption and not charge the batteries.
Here’s how dummy forecasted load solves the problem.
hmm, in your price graph i can’t see that, so I assumed it’s exactly eqal to sell, and therefore not visible.
So yeah, the scheduler seems to only schedule to charge what’s needed for the “expected consumption” upto 00:00. That is really strange.
It will correct that schedule, tomorrow, when it can see the next days prices and figure out it could need more battery charge during the night. But still strange.
No, that is because I cropped the picture as buy price was not relevant.
Oh, and besides grid fee, VAT is added on top of the final price. Price for individuals can’t be negative, so at the lowest price tomorrow I get 0 when selling to grid (if price could be negative, I would have to pay myself), and must pay 0,064 when buying from grid.
I think it is by design. I am in Trade mode and DESS tries to minimize costs and maximize earnings. It looks like it estimates half of set battery cost per kWh during charging and the other half during discharging. So that is why it does not schedule charging as it thinks I will be losing money.
This is an estimated costs graph with my “edit estimate” hack. Pure loss tomorrow although very small. In reality that is just battery costs and I don’t lose actual money.
Yeah, the technical reason is that it targets “minsoc +1” at the end of the visible price period.
So, with apparently negative prices, it can’t feedin, that little consumption visible is not much - so the only way to achieve that “minsoc +1” goal is… what it schedules for.
It can’t see any slot to “sell”.
But I agree in this case it should just charge available solar and then let the battery sit around at high soc, until there is a sell opportunity coming.
What are your sell / buy prices usually? Cause eventually you may be better off to use green mode with “sell2grid” enabled. It will then defer solar-selling into the most expensive hours, but always focus on self-consumption, first.
Yes, that could happen. But at that point it is already 2 or 3 hours past midday and there is not much solar left for charging. Actually, it leaves just enough battery to survive until next morning and will not need more battery during the night. But if received night price is higher than about 8 cents, it will charge from the grid to be able to sell at night with profit.
So in the end what happens with current DESS implementation is that solar energy is lost due to DESS not charging the batteries as it sees no need for that, and then charging from grid in the evening when it receives high next day (nigh/morning) prices and there is not enough sun to charge to 100% until sunset.
