Re: Hyphae TSC Meeting [Every Other Thursday] - Thu, 04/29/2021 6:00pm-7:00pm #cal-reminder
James Kempf <kempf42@...>
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Thanx for sending out the meeting notes. I'd like to clarify my position w.r.t. load control.
It is not that I don't think load control is needed. Actually, it is important for a microgrid, especially one having exclusively renewable generators, to be able to shed load when grid disconnection happens. In addition, even if the grid is connected, it is important to be able to schedule load when renewable generation is high on the grid or the TOU tariff is low and deschedule it when renewable generation is low or the TOU tariff is high. This allows such strategies as using a building as a thermal battery by precooling it during the afternoon to below the ideal temperature when the grid has lots of solar generation and turning the HVAC system off in the evening when the solar resource starts to go away.
For this reason, I think having the microgrid be able to control prioritized circuits when the grid is down, and be able to control when HVAC equipment and hot water heaters run when the grid is up is necessary. The actual prioritization and scheduling of loads should be done by the building energy management system not the microgrid controller, as these are functionally distinct. Soft circuit prioritization is also more desirable than hard circuit prioritization. Having the priority controlled through a building energy management system allows the circuits that are energized to change during the day when the grid is down rather than having a critical loads subpanel where a fixed set of loads are backed up and the others are not.
I would like to have an OpenAPI 3.x REST API between the building energy management system and the microgrid controller for indicating which circuits are prioritized when the grid is down and when HVAC and hot water heater loads should run. Also when to charge the battery and when not, but I think that is already covered by Hyphae. A separate API between the microgrid controller and load circuits and major loads turns prioritized loads on and off when the grid is down and the HVAC equipment and hot water heater on and off for flexible scheduling. The latter might be available through protocols such as BACnet or Modbus, but having a REST API on top of those protocols would greatly enhance interoperability. Scheduling flexible loads may not require the microgrid controller to talk directly to the HVAC equipment, it might just require the building energy management system to tell the microgrid controller when to run the HVAC.
What I don't think is necessary is fine grained load control of individual devices. For example: "I would like my porch light to be switched on and the stereo playing when I get home from work". That is basically a lifestyle type function, and while I image it could be important, I don't see it as relevant to microgrids (though it is relevant to building energy management systems). My view is that the CHIP (Connected Home over IP) consortium is addressing such lifestyle/smart home functions, since they say nothing about controlling batteries or DERs in their charter.
Does that make sense?
On Fri, Apr 30, 2021 at 3:25 AM <kotaro.jinushi@...> wrote: