Microgrids Operation for More Efficient Disaster

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Apr 17, 2014 - such as the potential for higher power supply availability and .... Tokyo Gas microgrid, Aichi Institute of Technology microgrid, Japan; ... momentary shut down as soon as the city lost power, could .... month and a half after Hurricane Gustav, in mid-September .... The estimated cost of damages incurred by.
Powering Through the Storm Microgrids Operation for More Efficient Disaster Recovery

By Chad Abbey, David Cornforth, Nikos Hatziargyriou, Keiichi Hirose, Alexis Kwasinski, Elias Kyriakides, Glenn Platt, Lorenzo Reyes, and Siddharth Suryanarayanan Digital Object Identifier 10.1109/MPE.2014.2301514 Date of publication: 17 April 2014

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DISASTERS, WHETHER NATURAL OR MAN-MADE, compromise the quality of life for all involved. In such situations, expeditious recovery activities are deemed imperative and irreplaceable for the restoration of normalcy. However, recovery activities rely heavily on the critical infrastructures that supply basic needs like electricity, water, information, and transportation. When disasters strike, it is likely that the critical infrastructures themselves are affected significantly, hampering efficient recovery processes, thus presenting a Catch-22 conundrum. In this article, we present examples from different parts of the world where distributed energy resources, organized in a microgrid, were used to provide reliable electricity supply in the wake of disasters, allowing recovery and rebuilding efforts to occur with relatively greater efficiency.

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The concept behind the MPQSS is to simultaneously provide power at multiple quality levels according to consumer needs.

What Is a Microgrid? According to the CIGRE Working Group (WG) C6.22, “microgrids comprise low voltage distribution systems with distributed energy sources, storage devices, and controllable loads, operated connected to the main power network or islanded, in a controlled, coordinated way.” A microgrid may also be defined as a self-contained subset of an area electric power system (EPS) with access to indigenous distributed generation sources, distributed energy storage devices, end-user loads, control and protection switchgear, and distribution system assets. A microgrid is equipped to function in parallel with the area EPS, appearing to the rest of the grid as a single controllable entity as well as in an intentionally islanded mode. Presently, a typical microgrid can be found serving dedicated loads such as campus facilities, remote communities, and military installations. The microgrid concept offers a potential avenue to increase the penetration of renewable energy-sourced generation in the grid, especially in light of stunted investments in transmission systems in most

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developed countries. Microgrids possess several advantages, such as the potential for higher power supply availability and security for critical loads, investment deferrals in transmission and centralized generation plants, the provision of ancillary services to EPS, and opportunities for economic incentives for customers. The microgrid concept is in alignment with the smart grid vision of the U.S. Department of Energy (DOE), the Smart Power Infrastructure Demonstration for Energy Reliability and Security (SPIDERS) program of the U.S. Department of Defense, and is a key component in the Strategic Research Agenda for Europe’s Electricity Networks of the Future. A conceptual architecture of a microgrid is shown in Figure 1, and Table 1 lists some of the microgrid installations in the world.

Microgrids in Disasters with Electricity Service Disruptions We present some examples of microgrids that were used to increase electricity supply availability during disasters

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figure 1. A conceptual one-line diagram of a microgrid based on IEEE Standard 1547.4. (Source: C. Abbey.) 68

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table 1. Some examples of microgrid deployments in different parts of the world. Region

Microgrid

North America

FortZed, Fort Collins, Colorado; University of San Diego, California; Santa Rita jail, Santa Rita, California; Perfect Power, Chicago, Illinois; BCIT microgrid, Vancouver, BC, Canada; Balls Gap Station, Milton, West Virginia

South America

Robinson Crusoe Island, Chile; Ollagüe’s microgrid, Chile; Huatacondo’s microgrid, Chile

Europe

Model City of Manheim, Germany; Cell Controller Project, Denmark; CRES-Gaidouromantra, Kythnos, Greece; Liander’s Holiday Park at Bronsbergen, Zutphen, The Netherlands; RSE-DER test facility, Italy; TECNALIA-DER test facility, Bilbao, Spain; PIME’S project, Dale, Norway; Szentendre, Hungary; Salburua, Spain; La Graciosa Island microgrid, Spain; Optimagrid, Spain; iSare project, Guipúzcoa, Spain

Asia

Rural PV hybrid microgrid, West Bank; Hangzhou Dianzi University, China; NEDO microgrid, Aichi, Kyotang, Hachinohe, Japan; NEDO Tohoku Fukushi University, Sendai, Japan; Shimizu Corp. microgrid, Tokyo Gas microgrid, Aichi Institute of Technology microgrid, Japan; INER microgrid, Taiwan

Africa

Diakha Madina, Senegal

Australia

CSIRO, Kings Canyon, Coral Bay, Bremer Bay, Denhem, Esperence, Hopetoun, King Island, Rottnest Island

Note: Information from the U.S. DOE Renewable and Distributed Systems Integration (RDSI) projects and CIGRE WG C6.11.

or cases in which microgrids could have been utilized to improve power supply availability.

The Tohoku Region Pacific Coast Earthquake and Its Relationship with NTT Facilities Microgrid in Sendai, Japan The great East Japan earthquake, which struck at 2:46 p.m. Japan Standard Time on 11 March 2011, coupled with the subsequent tsunami and nuclear accident at the Fukushima #1 nuclear power plant, inflicted massive damages to the infrastructure in the eastern part of Japan. The Tohoku region Pacific coast earthquake and the Fukushima #1 nuclear power plant incidents highlight an important aspect of disasters: they are not single events with consequences limited to the period of time when a damaging action affects the electric power supply. From an infrastructure-planning perspective, disasters have distinct phases, some of which could last several months or even years. The phases are 1) preparation, 2) disaster occurrence, 3) immediate aftermath, and 4) long-term aftermath. In the case of the nuclear incident at the Fukushima #1 nuclear power plant, the preparation phase involved the engineering and design tasks related with preparing the nuclear power plant for an earthquake and tsunami of a given magnitude. The disaster occurrence phase was when the tsunami struck the site. The immediate aftermath phase included all the tasks intended to avert the nuclear accident and the immediate activities to mitigate its effects and control the reactors into a stable state. As of late 2013, the present phase is the long-term aftermath in which Japan’s generation capacity has been reduced dramatically. Such a drastic loss of generation capacity, mostly caused by safety concerns derived from the 2011 disaster, has led to planned blackouts and the need for voluntary power consumption reduction, which impacts not only the electric utilities finances but the quality of life and economic outlook of the entire country of Japan. may/june 2014

In the last several years, there has been a diversification of user needs and in the development of distributed power supplies and energy system technology in Japan. The gridtied photovoltaic (PV) systems penetration has been growing, and several wind farms have been built around Japan. It is pertinent to note that one of those, the Kamisu wind farm, survived strong shaking and a 5-m tsunami wave. Against this background, there has been research and the investigation of new and forward-looking power network systems. An energy supply system for meeting consumer needs in such a distributed environment is the multiple power quality supply system (MPQSS). The concept behind the MPQSS is to simultaneously provide power at multiple quality levels according to consumer needs. It involves a complementary engagement of distributed power sources, including solar power generation systems, fuel cell systems, and existing power systems, as well as the efficient use of batteries and power electronics. The actual field operation of the MPQSS was conducted in Sendai City, Japan, in 2003–2007. This demonstration project was supported by the New Energy and Industrial Technology Development Organization (NEDO). Figure 2 shows the configuration of the MPQSS installed in Sendai for the demonstration project, which was the first trial to take place in Japan in the area of power quality concepts and solutions. For this demonstration, NTT Facilities, Inc. developed and operated an MPQSS that had the capability to feed four classes (A, B1, B2, and B3) of ac and one of dc power while meeting various customer requirements. Quality classes A, B1, and dc were interfaced by an integrated power supply (IPS), and classes B2 and B3 were interfaced by two dynamic voltage restorers (DVR). The IPS comprised a bidirectional power converter, a dc-ac inverter, a dc-dc converter for powering the load, a semiconductor switch, and a sealed lead-acid battery. It supplied power in three quality classes: dc, A, and B1. The MPQSS had three types of distributed IEEE power & energy magazine

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that affected Christchurch, New Zealand. In addition to the aforementioned generation-level outages discussed in result of the Fukushima #1 nuclear power PAS 350 kW 350 kW 50 kW 250 kW plant incident in Japan, all of these disasters caused power outages PV GE GE MCFC CB1 originating in failures at the transmission and distribution level. For CB2 6.6 kV ac- Bus example, in Chile, the longitudinal configuration of the interconnected system led to the formation of four Integrated Power Supply DVR 2 DVR 1 electrical islands when equipment (IPS) failed at large substations (see Figure 3) and when a few transmission lines experienced some damage. Still, these damages were relatively Normal B3 B2 B1 A dc Quality Quality Quality Quality Quality Quality minor, and service into a single Load Load Load Load Load Load transmission system was restored within two days in the mainland. 130 kW 420 kW 18 kW 180 kW 20 kW 700 kW More damage, although affecting a small percentage of power grid elements, occurred in the distribution MCFC Molten Carbonate Fuel Cells PAS Pole Air Switch portion of the grid causing power GE Gas Engine Generator Set CB Circuit Breaker outages extending up to a week. PV Photovoltaic Panels DVR Dynamic Voltage Restorer On the island of Robinson Crufigure 2. A configuration of the MPQSS installed in Sendai, Japan. (Source: K. Hirose.) soe in Chile, where half of the main grid disappeared underwater in the aftermath of the 2010 earthquake and tsunami, it is quite typical generators (DGs): gas engine sets, fuel cells, and PV panels. to find diesel systems in operation. When such disasters affect The total rated capacity of the DGs was 1 MW. After the four-year field demonstration period, the MPQSS these islands, the transport of diesel to the islands by ships is was kept in operation with some technical modifications. As impeded, thus reducing the reliability of the isolated electria result of the Tohoku Fukushima disaster, a long-term power cal system. Such systems offer an avenue for integrating local outage of about two and a half days occurred, even in Sendai resources and assets for electrical storage so that a reliable supCity where the MPQSS had been operating. At the same time, ply of electricity can be available for critical loads. An additional the trunk line for medium-pressure gas was undamaged, and gas-supply services were never interrupted to the city. As a result, gas-engine power generators, although experiencing a momentary shut down as soon as the city lost power, could be restarted shortly thereafter. These were used to power university hospitals and welfare facilities. Concomitantly, the supply of heat using thermal exhaust from power generation was available for use. Additionally, the supply of high-quality power such as dc and uninterruptible ac (quality class A and B1) to loads continued without interruption even immediately after power was lost to the rest of Sendai. It is significant to note the usefulness of the NTT Facilities microgrid at Sendai in the relief and recovery efforts that followed the Fukushima #1 nuclear power plant disaster. II) Islanding Mode

III) Outage (Backup Mode)

600 kVA

200 kVA

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Earthquakes and Tsunamis in Chile, Japan, and New Zealand Extensive power outages followed the February 2010 earthquake and tsunami in Chile, the March 2011 earthquake and tsunami in Japan, and the 2010 and 2011 series of earthquakes 70

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figure 3. Damage at the Charrua Substation, Chile, after the 2010 earthquake. (Source: A. Kwasinski.) may/june 2014

figure 4. A demolished substation in Minamisanriku, Japan, after the March 2011 earthquake and tsunami. The poles in the background were installed as part of the restoration process. (Source: A. Kwasinski.) figure 6. Damaged buried cables in Christchurch, New Zealand, after the February 2011 earthquake. (Source: A. Kwasinski.)

figure 5. A pole and transformers in Rikuzentakata, destroyed by the tsunami that affected Japan in March 2011. (Source: A. Kwasinski.)

advantage of integrating local sources is a reduction in the consumption of fossil fuels. Similar outcomes were observed in Japan after the 2011 earthquake, where the most significant damage was observed in many coastal towns where the massive tsunami demolished all infrastructures (see Figures 4 and 5); still, long outages also extended inland, where the damage to the power grid was relatively minor. The series of earthquakes in Christchurch, New Zealand, particularly in February 2011, presented a similar performance of the power grid—i.e., outages mostly originated in failures at the transmission and distribution levels. However, since most of the power lines in Christchurch are buried (as opposed to mostly overhead lines in Chile and Japan), the failure modes were different, mostly caused by severe soil liquefaction and extreme ground shaking affecting the buried cables and transformers (see Figures 6 and 7).

Hurricanes Ike, Gustav, Katrina, and Superstorm Sandy In the past decade there have been several hurricanes in which the inherent fragility of electric power grids caused by centralized power generation, control architectures, and long power may/june 2014

figure 7. A “sinking” substation as a result of extreme soil liquefaction in Christchurch, New Zealand. (Source: A. Kwasinski.)

delivery paths is exemplified. In 2005, Hurricane Katrina caused more than 2.7 million outages in the U.S. Gulf Coast area, some of which lasted several weeks. Three years later, Hurricane Gustav caused more than 1.1 million power outages in approximately the same region affected by Katrina. A month and a half after Hurricane Gustav, in mid-September 2008, Hurricane Ike caused even more outages than Katrina or Gustav. Hurricane Ike initiated more than 3 million outages in the western U.S. Gulf Coast states and more than 1.5 million outages in the eastern half of the United States, including more than 1 million in Ohio (located 1,000 km north of the Gulf Coast). In 2011, Hurricane Irene caused almost 6 million electric outages in the northeastern U.S. coast. Despite these extensive power outages, excluding a relatively narrow area along the coast where the hurricane storm surge caused extensive damage, most of the areas affected by power outages had fewer than 1% of the grid infrastructure components showing damage—e.g., one in 100 poles were damaged, usually as a result of intense winds (see Figure 8). IEEE power & energy magazine

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From an infrastructure-planning perspective, disasters have distinct phases, some of which could last several months or even years.

During hurricanes, most issues leading to power outages originate at the transmission and distribution level of the power grid. This was exemplified by an electrical island formed after Hurricane Gustav, roughly along the Mississippi River between New Orleans and Baton Rouge, Louisiana, where, despite having a 320-MW operating generation capacity, power outage incidences still reached close to 100% of the grid customer base in most of the parishes within the electrical island. Microgrids are often a good option for powering loads during extensive power outages that occur during hurricanes and their aftermath. Although the above-mentioned hurricanes caused extensive grid power outages, natural gas distribution networks did not have outages as severe as

figure 8. A fallen pole in Baton Rouge, Louisiana, after Hurricane Gustav. (Source: A. Kwasinski.)

those experienced by the electric power grids. Microgrids with natural gas-fueled sources, such as microturbines or fuel cells with local reformers, have a higher probability of remaining operational after hurricanes. Such characteristics can be exemplified by the microgrid at Verizon’s Garden City, New York, Central Office, which is powered by seven 200-kW fuel cells (see Figure 9) and functioned satisfactorily after Hurricane Irene and Superstorm Sandy affected the U.S. east coast in 2011 and 2012, respectively. Since fuel cells have a relatively slow dynamic response, this site relies on diesel generators for local power supply during grid outages. The main function of the fuel cells is to reduce power consumption from the grid. Although unconventional, this configuration based on two diverse power sources meets the microgrid definition given previously. Moreover, by reducing power consumption from the grid, this microgrid represents an excellent solution for natural phenomena such as heat waves or severe droughts when conventional power grids are severely stressed. Additionally, it also indicates a contributing solution to the power-consumption reduction efforts during long aftermaths of disasters, such as the one experienced in Japan, in which the grid’s power generation resources are severely reduced. In general, distributed generation systems based on diesel-fueled generators (Figure 10) are the main choice for powering loads after hurricanes. In some cases, even electric power utilities rely on these types of generators to realize small ad-hoc-distributed generation systems used to provide emergency power to critical loads. During Superstorm Sandy, natural gas cogeneration assets at the campuses of New York University and Princeton University kept their local loads supplied with electricity. The microgrid at the Federal Drug Administration’s White Oak Research Facility in Maryland was also able to supply its local loads by islanding from the grid during Superstorm Sandy. Another example is that of the natural-gas-powered combined heat and power units based on the Consortium for Electric Reliability Technology Solutions (CERTS) microgrid model, which were retrofitted in a building complex in Greenwich Village, New York, that was able to tide over the outages caused by Superstorm Sandy.

Floods in Queensland, Australia figure 9. Fuel cells outside Verizon’s Garden City, New York, Central Office. (Source: A. Kwasinski.) 72

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From December 2010 to early January 2011, a series of floods occurred in Queensland, the northeastern state of may/june 2014

Australia, killing 35 people and resulting in an estimated A$30-billion loss to the Australian economy (see Figure 11). The floods covered three quarters of the state, an area larger than France and Germany combined. Parts of Brisbane, Queensland’s capital city, were flooded, and electric power was cut off to many areas due to safety concerns. This resulted in some situations where properties were cut off, despite not being inundated, because the arrangement of network feeders did not coincide with the areas flooded. This leads to three issues relevant to microgrids: islanding, protection, and education. During the floods, the residents in Brisbane were advised to consider all facilities as electrically live and to contact licensed technicians for the safe restoration of electric supply to damaged property. In the event of risk due to inundation, islanding is necessary. Due to rising waters, some residents climbed onto the roof of their property to escape while waiting for assistance. This led to risks where rooftop PV systems were installed, and residents were warned to treat solar panels and accessory equipment as electrically live. Further, the residents were also advised that solar PV systems were designed to shut off when the main grid was down. Residents were urged to avoid touching any part of the systems, including disconnecting individual panels to run small appliances or charge batteries. Some residents expected that having a PV system would mean that in the event of a natural disaster, such as these floods, they would have a secure source of electricity. Unfortunately, such systems are designed to operate in grid-tied mode only so they cannot be used during grid outages. The same issue has been observed during several recent hurricanes, such as Hurricane Isaac in the Lower Ninth Ward of New Orleans, Louisiana, a neighborhood rebuilt as a sustainable community after it was destroyed during Hurricane Katrina. One might observe that there is no technical barrier to making a PV system able to continue to provide local supply without the presence of a wider grid, and, even if resynchronization cannot be done automatically, a manual switch system would suffice to change between grid connect and island mode. In fact, such a system is employed in countries where the power supply is not very reliable. For example, many government buildings in India have standby generators that can be started, and the two-way switch system is used. The Queensland floods raised several issues in relation to microgrids. First, it seems that microgrids were already in existence but were not designed to transition to island operation. In fact, they were designed to detect unintentional islanding and simply shut down. While there is certainly an associated safety issue, there may be more sophisticated approaches that can be taken. This brings up the question of whether the barriers to this smarter behavior are related to costs or regulatory policies. Second, it raises the question of whether microgrids that allow “ride through” are smart enough to automatically detect conditions associated with a disaster and therefore be able to continue operation or shut down as required. Third, residents were judged to be may/june 2014

figure 10. Mississippi Power’s portable diesel generator after Hurricane Katrina. (Source: A. Kwasinski.)

figure 11. Floods in Queensland, Australia. (Courtesy: Timothy Swinson, Flickr-kingbob86.)

figure 12. Damage to distribution poles from the 2007 forest fires in Greece. (Courtesy: PPC, Greece.)

unaware of the capabilities and the risks of rooftop solar PV systems during a disaster, creating an issue of education that should be explored.

Forest Fires in Greece During 24 August–2 September 2007, forest fires erupted in Peloponnese and Evia in Greece, affecting more than 400 villages with 1,500 houses completely burnt and 6,000 people left homeless. The forest fires also caused extensive damages to the medium-voltage distribution network, including IEEE power & energy magazine

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Microgrids with natural gas-fueled sources, such as microturbines or fuel cells with local reformers, have a higher probability of remaining operational after hurricanes.

2,500 burnt poles, and seriously disrupting electricity supply to more than 90,000 customers (see Figure 12). The immediate mobilization of personnel of the national utility [Public Power Corporation (PPC)] from all over Greece to the locations of the fires for power supply restoration resulted in the minimization of outage durations; however, it is not possible to estimate the exact time of power cutoffs because it was affected by continuous fire re-ignitions. Few people had complete power outages for the entire period, but for more than 20% of the customers affected, it took longer than five days to restore their electricity supply. Distributed generation systems including mobile diesel generators of 50-, 100-, and 130-kVA ratings were used for restoring power supply to parts of the distribution network (islanded villages), forming ad-hoc low-voltage microgrids. The total cost of damage by the fires for PPC reached €10 million, while the total cost of power restoration (for distribution) was estimated at €6.3 million.

figure 13. Downed transmission towers during the 1998 ice storm in Québec. (Source: C. Abbey.)

figure 14. Locomotives were used for supplying electricity during the 1998 ice storm in Québec. (Source: C. Abbey.) 74

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Ice Storms in Canada In 1998, the worst ice storm in Québec’s recorded history lead to extended power outages for over 1 million customers in the Hydro-Québec service area. On 9 January 1998, the accumulation of ice over the previous five days eventually culminated in mechanical failures and a widespread blackout in a large part of the utility system. The additional mechanical load associated with the ice finally led to failures of the infrastructure at numerous points in both the distribution and transmission systems and the resulting electrical outages of the majority of customers in the Montreal area (see Figure 13). The impact of this event was felt on a large scale, affecting 3,000 km of power lines, 16,000 distribution poles, 3,000 transmission structures (including 1,000 pylons), and 4,000 transformers. As a result of the damages, some 1.4 million customers were without power, in some cases for up to a couple of weeks. The estimated cost of damages incurred by the utility was C$2 billion in Québec. In addition to the existing disaster action plans, locomotives were used by certain communities to restore power to certain sections of the distribution network, operated in an islanded grid or microgrid (see Figure 14). While a success, there were nonetheless delays in implementing the system and limitations in terms of the extent of load that could be served. This anecdote, while but a small part of the mitigation strategy that was ultimately developed following the disaster, speaks to the fact that microgrids, if properly planned for and coordinated, can play an active role in providing secondlevel services in the case of disasters.

Potential Venues for Microgrids Operation in Recovery from Disasters Evangelos Florakis Naval Base Explosion in Cyprus On 11 July 2011, a tragic explosion at the Evangelos Florakis naval base in Cyprus killed 13 people and injured dozens more. The country’s newest and largest power station at Vasilikos, situated next to the naval base, suffered extensive damages, in effect losing all of its power generation capacity for several months. At the time of the explosion, the installed capacity at the station was 428 MW, while two combined cycle units rated at 220 MW each were under testing/commissioning. The installed capacity in Cyprus at the time of the explosion was 1,584 MW, the actual generation capacity was 1,445 MW, and the maximum demand was 1,210 MW. Overall, the explosion may/june 2014

Typically, in earthquake-prone areas, the most suitable option to power microgrids is to rely on diesel-fueled engine generators.

resulted in the loss of 51% of the actual generation capacity of the country and inflated the costs of electricity to the end user by almost 100% in March 2012. Cyprus, being an island, has no electrical interconnections with other countries. Therefore, the sudden loss of such a significant amount of power forced the local electric utility to resort to sequential load shedding for over one month, until backup generation units were leased and shipped to Cyprus. Residential consumers experienced two-hour power interruptions, typically twice a day, whereas commercial and industrial consumers were forced to shut down their air conditioning and turn on their reserve units to aid the grid. It is apparent that if the electricity supply in Cyprus had not been so dependent on a highly centralized power station like the Vasilikos power station, but instead if a number of geographically disperse microgrids were in operation, the system would have been able to respond with higher levels of reliability.

Challenges The use of microgrids during disasters still faces some challenges. Arguably, the most important of those challenges is that many microgrids would rely on lifelines—essential infrastructures to operate a system, e.g., a natural gas distribution network is a lifeline for a microgrid with natural gasfueled microturbines—to keep their nonrenewable energy sources operating. There are several approaches to address dependency on lifelines. Perhaps the preferred approach is to design the microgrid so it is powered with diverse power sources. As the successful experience with the microgrid in Sendai, Japan, demonstrates, improving the design of the lifelines so they can perform well during expected disasters could enhance this approach. The effect of earthquakes on buried infrastructures has important consequences when planning microgrids in earthquake-prone areas. Since renewable energy sources typically provide a limited solution for continuously powering microgrids because of their intermittent output and potentially larger footprint, and natural gas service may be interrupted during earthquakes, options for powering microgrids in such situations are limited. Typically, in earthquake-prone areas, the most suitable option to power microgrids is to rely on diesel-fueled engine generators. Using diesel generators was a common choice to power critical loads after the earthquakes and forest fires mentioned above. These ad-hoc distributed generation systems were even implemented by electric utilities through the use of mobile diesel generators. may/june 2014

Still, these systems may not be termed as microgrids because they do not operate in coordination or in parallel with the main grid. Ironically, such a solution takes a closer form to what is defined as a microgrid in Haiti, where the power grid had a very poor reliability even before the January 2010 earthquake. In Haiti, critical loads such as communications facilities are usually equipped with permanent diesel generators that are used to power the load for most of the day because of the poor reliability of the main power grid. Hence, when the earthquake occurred, these loads did not experience significant outages because their infrastructure was already prepared to power the loads for extended periods of time when the main grid was out of service. The addition of local energy storage contributes to decoupling dependencies on lifelines. However, total decoupling would generally require adding a significant stored energy asset such as large battery strings at the microgrid site, which could increase its cost and footprint and lead to other design issues—e.g., large battery installations pose structural design challenges in earthquake-prone areas. Another approach is to include renewable energy sources at the microgrid site, such as PV arrays. The importance of using renewable energy sources to reduce the reliance of microgrids on lifelines presents

figure 15. A religious center used to provide emergency relief services in Kamaishi, Japan, with the capacity of being powered by a PV array and wind generators. The distribution power infrastructure was destroyed by the March 2011 earthquake and tsunami. (Source: A. Kwasinski.) IEEE power & energy magazine

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a previously mentioned paradox found in most conventional residential PV systems. Currently, these systems are equipped with grid-tied inverters, which cannot power their load even when the sun is shining during grid power outages. That is, even when PV systems do not have a lifeline, a renewable energy source cannot power its local load because another infrastructure, the power grid, has failed (see Figure 15). The reason for this issue is that grid-tied PV inverters need to comply with IEEE Standard 1547, which specifies that “the distributed resources shall not energize the area electric power system when the area electric power system is de-energized.” However, the U.S. DOE program Solar Energy Grid Integration Systems has already identified this issue in its 2007 white paper to promote research efforts to address such limitations in grid-tied PV systems, and there are current efforts to modify IEEE Standard 1547 to contemplate this situation. Another challenge is the education of the end user regarding the capabilities and expectations of a microgrid, especially those powered using renewable sources, as evident from the Queensland, Australia, floods incident.

Conclusions In 2013, Pike Research, an independent market research entity, predicted that the worldwide annual revenue from microgrids is expected to reach US$13 billion by 2018. International standards such as IEEE Standard 1547.4 have been developed for the efficient interconnection and operation of microgrids. In the United States, many demonstration projects sponsored by the DOE via the RDSI program have illustrated the use of microgrids. In Europe, two major research efforts have been devoted exclusively to microgrids with a total funding of €13 million including field trials in actual installations. From the examples presented in this article, the applicability and broader benefits of the microgrid in disaster relief are quite clear even though, in most cases, this was not necessarily a design objective. In that regard, the planning process for the future grid should take into account the coordinated operation of microgrids during disasters as one of their many potential benefits.

Acknowledgments The authors are grateful for the comments and guidance of Dr. Tsutomu Oyama, professor in the Department of Electrical and Computer Engineering, Yokohama National University, Japan, and Dr. Chris Marnay, (retired) staff scientist at the Lawrence Berkeley National Laboratory. The authors also acknowledge the insightful discussions of the participants and audiences of the panel, “Microgrids and Disasters,” at the Jeju 2011 Symposium on Microgrids.

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For Further Reading B. Kroposki, R. Lasseter, T. Ise, S. Morozumi, S. Papathanassiou, and N. Hatziargyriou, “Making microgrids work,” IEEE Power Energy Mag., vol. 6, no. 3, pp. 40–53, May 2008. E. Strickland. (2011, Oct.). IEEE spectrum inside technology. A Microgrid that wouldn’t quit: How one experiment kept the lights on after Japan’s earthquake. [Online]. Available: http://spectrum.ieee.org/energy/the-smarter-grid/amicrogrid-that-wouldnt-quit A. Kwasinski, “Technology planning for electric power supply in critical events considering a bulk grid, backup power plants, and micro-grids,” IEEE Syst. J., vol. 4, no. 2, pp. 167–178, June 2010. T. Oyama, A. Kwasinski, L. Reyes, D. Cornforth, C. Abbey, and N. Hatziargyriou. (2011, May). Microgrids at Berkeley Labs, Berkeley National Laboratories. Disaster panel at Jeju 2011 Symposium on Microgrids. [Online]. Available: http://der.lbl.gov/microgrid-symposiums/jeju-2011/ K. Hirose, A. Fukui, A. Matsumoto, H. Murai, T. Takeda, and T. Matsumura, “Development of multiple power quality supply system,” IEEJ Trans. Electr. Electron. Eng., vol. 5, no. 5, pp. 523–530, Sept. 2010. M. LaMonica. (2012, Nov.). Microgrids keep power flowing through Sandy outages, MIT Tech. Rev. [Online]. Available: http://www.technologyreview.com/view/507106/ microgrids-keep-power-flowing-through-sandy-outages/ R. Panora, J. Gehret, M. M. Furse, and R. H. Lasseter, “Real-world performance of a CERTS microgrid in Manhattan,” IEEE Trans. Sustainable Energy, to be published. IEEE Guide for Design, Operation, and Integration of Distributed Resource Island Systems with Electric Power Systems, IEEE Standard 1547.4, July 2011.

Biographies Chad Abbey is with the Hydro-Québec Research Institute, Varennes, Canada. David Cornforth is with the University of Newcastle, Australia. Nikos Hatziargyriou is with the National Technical University of Athens, Greece. Keiichi Hirose is with NTT Facilities, Inc., Tokyo, Japan. Alexis Kwasinski is with The University of Texas at Austin. Elias Kyriakides is with the University of Cyprus, Nicosia, Cyprus. Glenn Platt is with CSIRO’s Energy Transformed Flagship, Mayfield, Australia. Lorenzo Reyes is with the University of Chile, Santiago. Siddharth Suryanarayanan is with Colorado State University, Fort Collins. p&e

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