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zed-must avatar image
zed-must asked

ESS config templates or calculators?

hi,

Im setting up a new ESS and have what i believe is a slightly non standard setup and wondering if there is a program or matrix or smart calculator to allow me to achieve what i want without all the trial and error or reinventing the wheel.

1. What i want to achieve is to minimise grid usage (i.e. my monthly electricity bill), maximise grid feedback (monthly rebate) and never be completely without battery power in case of a power outage which does happen a couple of times a year.

2. my setup is 6kw wind turbine in a very windy location
20kwh lithium batteries (hope to double capacity soon)
quattro 15kva inverter, cerbo gx, bms etc (will add a small generator for backup eventually)
solar coming soon but i'm in ireland so i'm not expecting solar to be fantastic!
2 houses running everything on electricity ie hot water, heating etc, a polytunnel, a 9KW sauna and an electric car

3. where it gets complicated and where i get stuck is on the configuration. Here's why:

our day rate to purchase electricity from the grid is 0.40c/kwh
11-2am and 4-8am its 0.178c/kwh
2-4am its 0.10c/kwh

feedback rate earned 24/7 is 0.21c/kwh

So the q is - how do i optimise the ESS so that it automatically gives the best bang for my buck? For example i know that the best time to charge the batteries is from 2-4am and then run them down during the day when the rate is high. But the ESS will naturally take power from the wind first, which i don't want between 11-2, 2-4, and 4-8, because i make more money selling back my wind power during those hours. and if the batteries go below my threshold of say 15% at 7pm and there's no wind, they will start charging up from the grid, which is not really necessary and it would be better to wait until 2am for the cheap rate, although it might be good to just charge them a little, say 10%, in case the grid goes down. And then there are capacity limitations. I only have a 63a main fuse, so it may not always be possible to charge my whole battery bank in 2 hours for example if the car charge is also in use.

Lots of options, lots of possibilities, but surely someone has already done this and theres a config file i can copy paste or an excel sheet to enter all my variables and have it spit out the answer?

thanks!




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2 Answers
ejrossouw avatar image
ejrossouw answered ·

@zed must Short answer is there is no magic config file from my experience with multiple customer setups, especially for "non standard" setups. From a high level perspective you can easily use the scheduling to charge at specific times. You will have to delve into node-red for more control to e.g. stop self consumption in favour of exporting or explore DESS. Also, new functions are constantly added, which allows greater control without the need for node-red. For me part of the Victron experience is to go through the trial in error process so that you understand you system and can resolve issues and make adjustments as necessary. If that is not for you, consider engaging a dealer or installer.

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zed-must avatar image zed-must commented ·
that's brilliant, i didn't know about DESS, looks like exactly what i need so will try it. Thanks a lot for your help


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zed-must avatar image zed-must commented ·
Hi, are you an installer who could configure node red in my system to help achieve what I want Via vrm?
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gazza avatar image
gazza answered ·

This is not a trivial question. There are variables and constraints (known and unknown, since some "forecasting" is required) all varying dynamically over time. You will require some sort of numerical methods such as dynamic programming or optimization libraries in languages like Python (e.g., scipy.optimize). Choice of the optimization method would also depend on the complexity of your model. Here is an article that outlines a linear programming approach.
http://www.eseslab.com/posts/blogPost_batt_schedule_optimal

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