Never get energy from grid on DESS

Q&A and troubleshooting DESS
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1

Hello
How can I make DESS never buy energy from the grid?
Thanks

2

Why do you need DESS if you don’t want to buy electricity from the grid?

1 Like
3

I’m trying to understand the system, still at the beginning, and sometimes it makes the decision to bring energy from the grid and I still have battery power.
I don’t know if we can control this any other way…
Thanks

4

That is precisely the main benefit of the DESS. It uses the stored energy at the time when prices are highest. In your specific case, it will probably be more expensive later and the system will save the energy for that time.

5

Ok, but I may just want to sell or have some control over the purchase.

6

In my opinion, the DESS is not intended for manual sales. The DESS is intended for making the most economical decision yourself. There are or were functions for only buying or only selling, but I honestly don’t know if that still works in the current version.

7

ok thanks for your attention.
I’m just trying to understand how DESS makes decisions, today for example it started charging from the grid, with solar energy available.
The price of purchasing energy was high at that time.

8

So I have been following the development of DESS for a year now. I experienced some disappointments in the beta version but now the system actually runs well and correctly. In my opinion most malfunctions now occur because the “learning phase” of the forecasts is too short or the user-specific variables are not configured correctly (battery costs and the like).

9

That’s my problem I’ve started now, and I’m trying to understand how it all works.
I haven’t seen documentation yet on how DESS makes decisions.
I really need the learning curve.
Thanks for the help.

10

Don’t you think the right way would be to look through the documentation first and then ask your questions here?

11

Yes, I already read it.
But I have doubts, so I ask.
Is this the only documentation?
https://www.victronenergy.com/live/drafts:dynamic_ess

12

If you do not want to buy (sell) energy to (from) grid, you do not need DESS. Main purpose of DESS is to exploit low (high) grid prices.

Unfortunately DESS is still missing possibility:

  1. To specify day/night/weekend grid fees/taxes/etc
  2. To specify lowest SOC, below which trading stops and ESS only supports house loads

Waiting for Vicrton to implement these features.

1 Like
13

I want to sell energy to the grid. I do not need or want to buy energy any more than necessary. All but about 25kWh/year of our electricity use comes from PV: a few kWh of top-up are needed in long grey periods in Dec/Jan. The ‘automatic scheduling and use of solar forecast’ aspect of DESS is very useful for scheduling exports to maximise grid support and/or income. But in practice it doesn’t work for us because it still imports, even on sunny days, sometimes at 10am, sometimes at 3am, and sometimes at 4pm when it should be exporting (and using the battery to support local loads).

It is not true that it only does this because ‘the prices are incorrectly entered’. We tried jacking the import price right up to 50p/kWh for all the hours outside the (Octopus Flux) export period of 4-7pm, so import was always much more expensive than export, and it still did pointless imports. We did give it a few days to learn that this was pointless (and it does already have 2 months of consumption and solar data to work this out from), but it didn’t seem to want to stop doing it. There are many reports on here of this unhelpful behaviour (and even some nerdy workarounds to inhibit import which I have not tried yet). Perhaps a ‘a few days’ is not enough - the documentation is silent on how long one should allow? The primary issue seems to be that it tries too hard to stick to its SOC predictions, resorting to charging-from-the-grid even where more than enough solar to meet that hour’s shortfall will be available over the next hour or two. It’s hard to tell exactly because the algorithm is a black box.

So I disagree with the assertion made here that ‘You don’t need DESS if you don’t want to buy from the grid’. It’s true that we have been able to make a reasonable node-red flow to export at a given rate during the high sell-rate period, but it needs some manual tending, and would need (quite a lot) more work to get smarter about tomorrow’s weather forecast, and longer evenings leading to more consumption etc. Using DESS would save having to re-implement this sort of functionality, but until it learns not to import when it doesn’t need to, some sort of manual override is needed to make it useful, at least to people like us.