laursen
May 11, 2023, 8:33pm
24
somy:
My use-cases are:
To show hourly prices in a table like what https://elspotpris.dk shows. What is would be the best way to show those prices with hourly or 3-hourly intervals?
It’s currently not possible to do that for future prices, only historic prices which are persisted hour by hour. That’s one of the things I expect to be solved by the mentioned core pull request 3597.
To calculate when cheapest to charge the car, but I think the action calculateCheapestPeriod you have implemented works much better. In my current rules I have a nested for loop to go hour by hour to find our when to start charging, and it won’t work when the price is updated every 15mins.
That should be possible with calculateCheapestPeriod, although I’d be interested to know if it fully covers your case. You probably know how much you want to charge it and either the charge speed or perhaps even the duration needed? Depending on the information you have available to making the decision, we might find some calculation methods missing.
Btw, I consider the calculations within the binding temporary as they don’t really belong there. Still, for the time being they are better to have there than scattered even more in user rules etc. End goal:
opened 08:56PM - 07 Jan 23 UTC
enhancement
I'm creating this issue to start brainstorming ideas which may or may not grow i… nto something. For starters, I will share some unstructured thoughts, which could grow into something structured and potentially into something that could be designed and implemented.
Let me start out by sharing some links which can shed some light into where I'm coming from with this:
- https://github.com/openhab/openhab-addons/pull/13416#discussion_r980432359
- [Dishwasher price calculation automation](https://community.openhab.org/t/dishwasher-price-calculation-automation/139207)
- [Meter readings from Kamstrup Omnimeter with Pow-K+](https://techblog.vindvejr.dk/?p=523)
My initial need is integration to services providing future energy prices. After that, having these prices, I would like to be able to perform calculations. These calculations should be implemented once with a common interface, no matter from which service the prices were obtained. I wonder, from an architectural point of view, if this already means something is needed within openhab-core, since addons cannot depend on other addons? For example, core could provide some interfaces and calculations, while addons could integrate various API's implementing such interface.
Now really brainstorming/dreaming. For the dishwasher example, I logged energy consumption during our most frequently used program and manually mapped that into a timetable in a rule. Considering being able to select the last run specific program on some device (having an energy consumption channel which can be persisted) and map that into another timeslot to calculate the price of that, or having the ideal timeslot calculated automatically within some boundaries. I guess this is just a use-case for the price integrations and calculations and an application which should be built outside of openHAB itself, but just wanted to mention this, so that the parts needed for this could emerge.
I now also have almost real-time logging of the power consumption in my house (see third link above) provided a current power (W) as well as accumulated energy consumed (kWh). The accumulated value is updated once per hour, and current power is updated every 10 seconds. With this data I would like to be able to create a graph like this (screenshot from [AMS reader](https://github.com/gskjold/AmsToMqttBridge)):
For this some post-processing is needed, since I receive the kWh data like this:
```
2023-01-07 21:00:07.940 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'Omnipower_Accumulated' changed from 14609.85 kWh to 14610.24 kWh
```
i.e. as totals, not hourly contributions. So (14610.24-14609.85) kWh = 0.39 kWh from this log example, which is shown as last bar on the graph above. I'm not sure what is the best approach for doing this, but again it would be nice with something consistent and reusable.
I will update this issue with additional thoughts and knowledge from all of you.
I'm currently considering providing a small binding fetching data from EnergiDataService which is a Danish service providing prices. Yesterday I was also able to receive the same prices from ENTSO-E, but in EUR. So this could reach a broader audience, but would additionally require integration to online currency exchange rates to have conversion to local currencies. Currency question: Do we have any kind of currency handling in openHAB?
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