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Subject: Re: [emix] defining terms -- microgrid]

For definitions I'd look to the Galvin Electricity Initiative; the defintion is at http://galvinpower.org/microgrids .

Phil has a lot of excellent points. From the perspective of EMIX, I think that a microgrid reflects a market with electrical switching. Storage may be benefitical, as might alternate generation, but the DR/Curtailment within and consumption from outside are all part of my model of microgrids.

The interesting question is in Phil's first line "to whom is the definition important?" My discussions on the topic assume that there is a community of interest boundary, but that the boundaries are mutable. And the ability to buy/sell/transfer/consumer energy inside the microgrid with its own controls seems pretty central.

William Cox
Email: wtcox@CoxSoftwareArchitects.com
Web: http://www.CoxSoftwareArchitects.com
+1 862 485 3696 mobile
+1 908 277 3460 fax

Phil Davis wrote:
0F01D03BE833406095BD560EB6DB0355@us.schneiderelectric.com" type="cite">
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 Davis | Senior Manager Schneider Electric Demand Response Resource Center | 3103 Medlock Bridge Road, Ste 100 | Norcross, GA  30071 | (404.567.6090 | 7678.672.2433 | *phil.davis@us.schneider-electric.com | : Website:  http://www.schneider-electric.com


From: Anne Hendry [mailto:ahendry@pacbell.net]
Sent: Saturday, March 20, 2010 1:41 AM
To: emix@lists.oasis-open.org
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.



Holmberg, David wrote:
ECA909905BF0314CB16441980AFC5CE607A5A05686@MBCLUSTER.xchange.nist.gov" type="cite">

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.


From: Anne Hendry [mailto:ahendry@pacbell.net]
Sent: Friday, March 19, 2010 2:59 PM
To: emix@lists.oasis-open.org
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


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.


From: Anne Hendry [mailto:ahendry@pacbell.net]
Sent: Friday, March 19, 2010 2:49 AM
To: emix@lists.oasis-open.org
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.


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."

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
"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.

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.

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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