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Subject: Plane of Control vv. Transactional Energy
So, I wanted to think more about this “plane of
control” concept as it relates to Ed’s doc on TeMIX http://www.oasis-open.org/apps/org/workgroup/energyinterop/download.php/37301/Transactional%20Energy%20White%20Paper%20Draft%20004.pdf A refrigerator can be smart enough to monitor a price and
see that the price is higher or much higher than normal and take energy saving
measures. It can learn a daily routine and plan accordingly. It really doesn’t
need any higher level control, because no human is going to bother to tell it “I
have a load of groceries coming this evening with some potentially warm milk,
so please pre-cool before 6pm.” A home thermostat can have a pre-programmed schedule that is
used to adjust temperature. That is the control plane for the different
components of the heat pump/furnace/AC. But the thermostat may pay attention to
other inputs, like a door sensor that indicates an occupant’s arrival and
need to lower the temp, or certainly an occupants direct override. The
thermostat watches the price and the house temp profile may be adjusted
accordingly. There may also be DR signals that effectively move the plane of
control outside the home (even though the homeowner has essentially contracted
some grid-side service partner to handle energy management). A commercial HVAC controller takes this to a higher level,
with more sensor and human inputs, and variability in schedules. A building may
define common operation modes for different zones. A schedule for facility use
determines which modes apply at a given time. The price of electricity will be cross-cutting
input, adjusting each of the operation modes, perhaps bumping operation from
one mode to another, or into additional cost-saving modes. Microgrids somehow imply local power management: maintaining
voltage, managing load/storage/generation, and ability to go “off-grid”.
Some microgrid controller may micro-manage these things or instead use a market
mechanism to manage. We can have algorithms on the storage that indicate when
to store or deliver based on price. The real test is when we lose the big-grid
supply and can we manage voltage and phase. It’s not clear to me that
price messaging/markets can do that. Besides the electrical challenges, to make
the load/gen/storage balance work, we will need significant pre-programmed
rules for load flexibility. If some loads must shut down, then we must have
rules that say “you go to this mode at this price, and shut down at that
price” for all such loads/systems/devices. Is the question of “plane of control” the same
as “where is the human interface?”, unless (as in the case of the
refrigerator) there is no human interface? And in the case of a campus or
microgrid there are effectively multiple human inputs that impact a single
system. There is the building operator and the human resources office and the
Energy management director’s office and the “how green we want to
be” CEO office. Each of these impacts decisions about conditions on
energy use, and how and when and why. Hopefully they all work together to have
a consistent policy for response to price signals and other priorities. It’s the “other priorities” that Toby
brought up on the call. Price is not all that matters. Maybe source matters.
Maybe local matters—that might be factored in as a price adder on
external power. Other priorities might be reflected as exceptions in the policy
for a particular system, like “the bowling alley will never go into
reduced-power mode when the director has bowling league”. Perhaps some of this ought to be discussed in the TeMIX
paper. David Holmberg NIST Building and Fire Research Lab 301-975-6450 |
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