One
question worth answering is to whom is the definition important and how will it
be used? For example, a micro economy can be your household, neighborhood,
or town, and it cannot print money (legal tender, that is). A Macro
economy includes a regulatory authority, and it can print money. Therefore, the
rules of operation are different for each but with
similarities.
With
respect to microgrids, and with the possible exception of the LBNL wording,
the example definitions seem to imply asset requirements imposed on the smaller
group by a larger group. This is appropriate if a micro grid has legal
standing and is subject to market rules or regulatory authority. If that
indeed is the case, then said authorities also will define what a micro
grid is, much the same as DR Capacity is similar to but not exactly the same
between NYISO and PJM. the result will be a patchwork of definitions. The
U.S. is known for that.
Microgrids are a big topic in the buildings
industry. There are some building owner/management companies (The Irvine
Company, and CBRE come to mind) who use the term referring to plans to link
buildings into portfolios, then use internal "balancing" capability to negotiate
more favorable contracts with energy retailers and DR aggregators, and on and
on...So we need to accommodate both large scale authorities and the informal
groupings that are coming together in markets in response to increased awareness
of potential.
For
me, the most useful definition of a micro grid is some grouping of entities such
that they are under (or have the capability to be under) a central control point
and that the central control has the ability to measure, model and therefore
accurately describe and predict the state of that group together with its
capability to act in a specific way. The consumer of that information
might be an LSE, ISO, CSP, etc.
The
actual resources contained within that micro grid are less important than the
predictability of how that micro grid can behave together with its
communications reliability. Perhaps "micro grid" also should have some
legal component that gives a central point the ability to contract with external
entities. In that way, a potential usage such as "micro grid certified"
could mean that the expensive and time consuming work of audits, analysis,
retrofits, and commissioning has been done and and asset grouping is ready
to communicate and act in a meaningful way.
Such a
definition could be useful to LEED certification, market participants, market
value, etc, while still offering the flexibility that diverse capabilities (gen,
non gen; storage, non storage) could interact with interested third parties
that specialized in each area.
Phil
________________________________________________________________________________________________
Phil
Davis | Senior Manager | Schneider Electric Demand Response
Resource Center | 3103 Medlock
Bridge Road, Ste 100 | Norcross,
GA 30071 | (: 404.567.6090 | 7: 678.672.2433 |
*: | : Website: http://www.schneider-electric.com
From: Anne Hendry [mailto:]
Sent: Saturday, March 20, 2010 1:41 AM
To:
Subject: Re: [emix] defining terms --
microgrid]
every
microgrid should have some storage'should' ...
The
'interesting additions' came from a paper/presentation at the same site (second
link from end of original email -- DOE Electric Distribution Transformation
Program site) summarizing the results of a survey of technical experts.
The table on page 10 summarizes their findings showing the position of each of
11 of those experts on various questions aspects of a microgrid. The
question of whether a microgrid *must* have storage was only answered in the
positive by 2 of the 11 experts (DTE Energy and CERTS microgrid). 3 others
answered that storage was "preferred but optional" (Northern Power, Scandia, and
GE). The other 6 had no comment on the question. Northern Power's
definition of a microgrid is "2 or more distributed generation or storage assets
... assets may be combinations of power generation and energy storage devices
depending on the requirements of a specific application."
So the idea
seems to be definitely generation, and optionally storage. They recommend
storage, so, yes, 'should', but don't seem to think it would be
required. There was mention in a couple of the papers that backup
would be handled by the grid. I suppose that's where 'seamless' becomes
most important ...
Regarding 'driven by DER', here is the full sentence:
"Many microgrid concepts appear to be driven by DER technology rather than by
energy service requirements." I saw similar statements in at least one
other, maybe two, of the sites mentioned below. I'm not entirely sure what
constitutes 'energy service requirements'. I'll try to find the other
instances.
HTH,
Anne
Holmberg, David wrote:
I
don’t think I agree with any of the “interesting additions”, except that every
microgrid should have some storage to allow meeting typical demand
requirements. I’m not sure what “driven by DER” means. Certainly there has to
be some DER. The definition and value of high reliability is in the eyes of
the beholder.
David
From:
Anne Hendry [mailto:]
Sent:
Friday, March 19, 2010 2:59 PM
To:
Subject: Re:
[emix] defining terms -- microgrid
Yes, the primary recurring attributes seem to be:
-
can operate independently from grid or in parallel
- can seamlessly move
from one mode to the other
- independently controlled at the local level,
no need for central control
- driven by DER, co-locates generation and
load
- highly reliable
Interesting additional notes from the survey
presentation at the same site are the 'points of varying agreement'
-
generation capacity must be < 1 KW
- must contain > 1 generation
source
- must connect to the grid at a single point
- must contain
storage (batteries, etc)
- must be able to meet full load
requirement
-A
Holmberg, David wrote:
They
all agree as far as I can tell. I like the http://www.electricdistribution.ctc.com/microgrids.htm,
along with the EI idea of hierarchy put together.
David
From:
Anne Hendry [mailto:]
Sent:
Friday, March 19, 2010 2:49 AM
To:
Subject: [emix]
defining terms -- microgrid
We've been using the term
microgrid (among others) frequently and today it came up again but with the
thought it might also be applicable to subsystems within the
'macrogrid'. At the same time, in the Dutch 'microgrid' paper,
they use the term Virtual Power Plant (not so much a microgrid, but more of a
role a microgrid may assume). 'Microgrid' is used and defined
differently by different entities and the definition is evolving, as are most
in this space, and new terms are devleoping. Perhaps it would be helpful
to start a glossary for terms like these we may use in the spec so everyone
understands the definition as they are used by EMIX? The defining
process may have the added value of generating more clearly articulated scope
and price communication requirements.
For instance, below are several
different defs/characteristics for microgrid I've run across recently.
Each specs a different set of characteristics from which we could generate an
amalgam of those (and any from other sources) characteristics most relevant to
EMIX and perhaps then define some use cases using these characteristics to
drive element declarations/definitions?
Just throwing this out, as an
example, to start gathering glossary terms.
-A
EI
spec:
"Small, local versions of the bulk power grid that optimize the local
distribution system and may include local generation and storage. A
microgrid may contain smaller microgrids and may be part of a larger
microgrid; communication interface at the edge of each microgrid is the
same."
http://eetd.lbl.gov/CERTS/pdf/mg-pesc04.pdf
Subsystem
of generation and associated loads that can separate from the distribution
system to isolate from disturbances without harming the transmission grid's
integrity and providing higher local reliability by islanding generation and
load together. Allows for local control of distributed generation,
eliminating the need for central dispatch.
From NAESB report to
NIST
http://www.naesb.org/pdf4/interimsmartgridroadmapnistrestructure.pdf
"electric
island"
>From http://www.electricdistribution.ctc.com/microgrids.htm
A
microgrid, a local energy network, offers integration of DER with local
electric loads, which can operate in parallel with the grid or in an
intentional island mode to provide a customized level of high reliability and
resilience to grid disturbances. This advanced, integrated distribution system
addresses the need for application in locations with electric supply and/or
delivery constraints, in remote sites, and for protection of critical loads
and economically sensitive development. By operating microgrid in the
islanding mode, critical loads can continue to operate, impervious to grid
disturbance events.
http://certs.lbl.gov/certs-der-micro.html
CERTS
Microgrid:
A key feature of a microgrid, is its ability, during a utility
grid disturbance, to separate and isolate itself from the utility seamlessly
with little or no disruption to the loads within the microgrid (e.g., in the
CERTS Microgrid concept, no impacts on power quality). Then, when the utility
grid returns to normal, the microgrid automatically resynchronizes and
reconnects itself to the grid, in an equally seamless fashion. A
critical feature of the CERTS Microgrid is its presentation to the surrounding
distribution grid as a single self-controlled entity. A CERTS Microgrid
appears to the grid as indistinguishable from other customer sites that do not
include DER. This presentation means that the microgrid avoids many of the
current concerns associated with integrating DER, such as how many DER the
system can tolerate before their collective electrical impact begins to create
problems like excessive current flows into faults and voltage
fluctuations. The peer-to-peer concept insures that no single
component, such as a master controller or a central storage unit, is required
for operation of the microgrid. Therefore, by its very design, the CERTS
Microgrid can continue operating with loss of an individual component or
generator.
>From http://www.electricdistribution.ctc.com/microgrids.htm
http://www.electricdistribution.ctc.com/pdfs/Microgrid_Assessment_Phase_1.pdf
: (slide 4, also more detail at slides 9-11)
No clear definition, but
characteristics include ability to operate 'islanded' or 'grid parallel', and
to switch seamlessly between these two modes, and to include significant DER
capacity; driven by DER technology rather than by energy service
requirements.
http://green.venturebeat.com/2009/10/29/microgrids-a-21b-market-in-the-making/
Smaller-scale
electrical systems spanning college campuses, municipalities and business
parks, where energy is generated, stored and very closely managed on an
intensely local level. Without being hooked into one of the larger
national grids, there are less likely to be disruptions due to peak demand or
excessive power loads. Easier to do DR. Can store enough energy to
keep power flowing during blackouts or other disruptions. This makes them
ideal for emergency services, hospitals, and of course, the
military.
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