DESS - Understanding Strategy

Q&A and troubleshooting DESS
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1

Hi, I’m using ESS since one year and last week started to run DESS.
A question for understanding the strategy with todays data as example:

  • prognose shows a maximum battery SOC of 68% using the solar power
  • my hourly grid tarif shows an extrem low price of 16 Cent (that around minus 2 cent below the fix price part) … and it is 3cent lower the price I would get selling to grid (fix 19cent)
    I would expect a battery load up to 100% SOC in this cheap phase: the system expects a SOC up to 68%, now it should take 32% from the grid to participate from the low pricing.
    … but no grid loading is shown in prognose … WHY ???

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Michael

2

I am not an expert to this and yes, sometimes DESS does some strange things.
My general remarks on your setup:

  1. Your DESS is configured in green mode, so I would not expect it to do the commercially optimal thing.
  2. the cheapest price here is also when there is much solar available. It is not easy to charge from grid, while solar is plenty. In green mode, solar should be preferred in any case AND your system must be able to take the load. What I depict from your setup, your charge limit to the battery is 7.5kW. So with solar already charging ,either the batteries or your Multi(s) may already be working at maximum.
3

No, solar charging is moderat with around 2kW … enough room for multies fedding add. from Grid …

4

…well, this wasn’t visible from your input, as far as I am concerned…As said, I am not an expert. Suspect is “green mode” as the root cause in your case.

5

At least in Green Mode, DESS tries to charge only enough from the grid to cover the day’s consumption without the need for buying expensive grid power. This is the case here, as there is no grid consumption in the expensive hours until the end of the day. So DESS has done everything right here.

DESS would only have charged the battery from the grid if expensive grid power had been required. However, this was not necessary here to get through the day without drawing from the grid.

In addition, charging from the grid only takes place if there is a sufficiently high difference in purchase price between the time of charging and the time of consumption, as the battery also has losses and costs per kWh.

As soon as the prices for the next day are available later, the planning is adjusted accordingly, which was not the case for you at that time.