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Subject: RE: [emix] Plane of Control vv. Transactional Energy
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David: The
plane of control description you mentioned is an interesting element to
consider. The description, along with the “other priorities”
mentioned, seem to indicate there are multiple intersecting planes of control
and locations for the human interface. We need to have some elegant simplicity
to have a managable system that still leaves the desired planes intact. There
was one statement that seems a bit delicate. “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. “
This seems to be trying to force a price system to behave like direct load
control program. In my opinion, we need to be very cautious of this idea of
using price for a forced / absolute response. In
the human dynamics process of making significant changes, there is a tendency
to want to make the new system function like the old system to which we have
grown accustomed. Sometimes this indicates that we have not adapted to the
change and the benefits or features it entails. In this case there may be reason
to also have DR/DLC signals or emergency signals separate from price. However,
we may want to hesitate on the expectation of having price system with a point
where a system “must” shut down. It may be more realistic to
assume that, over time, we will develop are reasonable amount of statistical
reliability based on experience with pricing. Gale Gale R.
Horst Electric
Power Research Institute (EPRI) From: 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 301-975-6450 |
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