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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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