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khostri avatar image
khostri asked

Dynamic ESS - configuration

Hello.

I am new here and haven't found answer searching through this community.

I have just deployed Dynamic ESS flow (GitHub - victronenergy/dynamic-ess)

But I am not sure if I understand correctly some configuration values and settings:

Battery cost - not sure what does it mean. If this value should reflect charging efficiency. I.e. how many more kWh I need to provide to charge 1kWh of battery and thus price for that percentage. Or if this value should reflect battely life - like purchased battery cost per battery life cycle calculated to €/kWh

Buy price: Not sure if in case of fix / month I need to recalculate it to hours. For example: (p+0.002722+0.012)*1.21+(p*(0.004541+0.06444)+0.000191+0.009111)*1.21

Price consist of market price + regulated price for distribution here:

Distribution

0.004541 is cost per kWh

0.06444 cost per kWh

0.000191 monthly fee converted to hour price

0.009111 montly fee for 3x25A to hour price


Market

0.002722 monthly fee converted to hour price

0.012 €/kWh


1.21 is tax. Do I have it correctly setup? Or I have made some errors is my estimations?


Thank you

Node-RED
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4 Answers
victech-power avatar image
victech-power answered ·

I would advise to read the manual first : victron-dynamic-ess (node) - Node-RED (nodered.org)
You can find all your questions there.

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khostri avatar image khostri commented ·

Thank you for link. I have read manual already before post. For example can you please point me out what this exactly means as I have asked this in question:

Cost of charging or discharging battery (in €/kWh)

I can see not 2 (as posted) but 3 possible answers and not sure which si correct. And each option has totally different value there:

  1. fix prices for getting power from grid pet kWh. So for example when I transfer 1kWh into battery, it will cost me 0.068981 / kWh for distribution
  2. price for additional energy I need to provide to battery to charge it +1kWh. so if MPPT has something like 96% efficiency, invertor has something like 92% or so rounded its around 88% effficiency. So for every kWh battery charge I need to buy 0.137 kWh more which I can provide average € /kWh price - ie something like 0.1 € / kWh
  3. cost of battery life (not sure what is proper wording here). 2x 9.6kWh Winston battery cells cost around 14k€.. I think I can count like 2000 full cycles (there will be degradation but battery should still work). So putting 20kWh * 2000 cycles is 40000 kWh into battery for cost of 14 000 €. So cost for 1kWh is 0.35 € (which is closes to default value)

So what is correct value meant there?

Also second part of my question regarding buy and sell prices - I have read text several times and found my mistake - in formula for sell price I need to substract values from p not to add. But I am still unsure what is best way to use fixed prices in formula - I mean if energy cost consists of fix price / month. I have tried to do kWh consumption/production estimation in average and calculate price per kWh from this estimation to be added to formula. Is it only approach there?

Thanks again.

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magnusb avatar image
magnusb answered ·

Hi,

I am quite fresh to the topic myself, but believe I can at lease answer one of your questions from my understanding of the manual:

1. the monthly cost is not relevant for the calculation at any point as it does not scale with use of the grid - or does it in your particular case? if so please explain how - do you pay a different monthly fee depending on how much energy you consume?


What I am also still unsure about is the cost of charging/discharging. The manual suggests: 

costs for buying the battery in € / (charging cycles * battery capacity in kWh)

but it is unclear to me if I shouldn*t add losses to this as well of approx 20% or if the algorithm itself does this and of course would use less if the battery is carged directly via DC instead of being charged via a Multiplus form AC.


Anyone with insights to this?


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marco-face avatar image
marco-face answered ·

The algorithm applies a battery cost to the charging as well as the discharging cycle. If you have worked out that your battery cost is 10 cents per cycle it is advisable to fill in 5 cents in the dynamic ess node battery cost parameter. You can verify this in the node red dashboard cost/revenue graph.

The way I price the inefficiency is as a discount on my sell price. Under normal ESS my system is about 88.4% efficient but this drops to 77% - 86.6% when doing relatively large arbitrage. The low efficiency seems to come about when the battery still has a high SOC at the beginning of the day and has cooled since its previous charge thus losing efficiency. When the charge - discharge cycle is afternoon-evening my efficiency in the upper part of the range and battery temperature delta is much lower.

The way I discount is by dividing my price formula by (price formula)/(1+discount) where the discount variable is the inefficiency I want to earn back through the price given the lower kwh's (Q). I use an average discount of 10% in my system currently. Let me know if anyone has a better method.


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cronblad avatar image
cronblad answered ·

Anyone that can point me to Q&A related to missing "provider" list in Dynamic ESS for Sweden?

provider-list-missing-dynamic-ess.png


provider-list-missing-dynamic-ess.png (43.3 KiB)
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