metadata: authors: 0: author: Schweikert,Amy Elizabeth
1: author: Nield,Lindsey
2: author: Otto,Erica
3: author: Deinert,Mark Robert
count: World
docna: 0: docna: Resilience and Critical Power System
            Infrastructure : Lessons Learned from Natural Disasters and
            Future Research Needs
docty: Policy Research Working Paper
subtopic: Hydrology,Energy Policies & Economics,Energy Demand,Energy and Mining,Energy and Environment,Natural Disasters
teratopic: Water Resources,Energy,Environment
abstracts: cdata!: Resilience against infrastructure
            failure is essential for ensuring the health and safety of
            communities during and following natural hazard situations.
            Understanding how natural hazards impact society in terms of
            economic cost, recovery time, and damages to critical
            infrastructure is essential for developing robust approaches
            to increasing resilience. Identifying specific
            vulnerabilities allows for better communication, planning,
            and situation-specific interventions. This is particularly
            relevant in areas recovering from a natural hazard that have
            the opportunity to build back their infrastructure, and for
            those currently planning infrastructure expansions. This
            study considers recent hurricanes, earthquakes, droughts,
            heat waves, extreme wind and rainfall events, ice and
            thunder storms as well as wildfires. For many of these, data
            are available for the same type of hazard in different
            geographies which provides information not only on specific
            vulnerabilities, but whether the impacts are location
            dependent. Where available, specific design considerations,
            cost information for repairs, and the recommendations for
            'building back better' are presented. Above-ground
            transmission systems were the most commonly affected power
            system component, with fuel and maintenance supply chains
            representing a major vulnerability for isolated regions and
            islands. Generation systems were most commonly affected when
            a hazard exceeded design limits, particularly in relation to
            water temperature or wind speeds. Institutional capabilities
            are important throughout the sector. In all case studies
            analyzed, the design standards of the infrastructure asset,
            and the ongoing maintenance of assets and the organized
            response (or lack of) has major implications for the
            performance of the electricity grid.
repnme: repnme: Resilience and Critical Power System
            Infrastructure : Lessons Learned from Natural Disasters and
            Future Research Needs
display_title: Resilience and Critical Power System
            Infrastructure : Lessons Learned from Natural Disasters and
            Future Research Needs
listing_relative_url: /research/2019/06/31166998/resilience-critical-power-system-infrastructure-lessons-learned-natural-disasters-future-research-needs
topicv3: Water m1326522 137,Energy and Extractives m1326595 507,Power and Electricity Sector m1327094 515,Drought m1503313 3162,Hurricane m1503314 3179
publishtoextweb_dt: 2019-06-19T00:00:00Z
historic_topic: Water Resources,Energy,Environment
no_of_pages: 70
author_keys: 0: author_key: 1154780
1: author_key: 1667844
model_extractions: Policy Research Working Paper 8900 Lifelines: The Resilient Infrastructure Opportunity _Background Paper_ Resilience and Critical Power System Infrastructure Lessons Learned from Natural Disasters and Future Research Needs _Amy Schweikert Lindsey Nield Erica Otto Mark Deinert_ Climate Change Group Global Facility for Disaster Reduction and Recovery June 2019
Policy Research Working Paper 8900

# **Abstract**

Resilience against infrastructure failure is essential for ensuring the health and safety of communities during and following natural hazard situations. Understanding how natural hazards impact society in terms of economic cost, recovery time, and damages to critical infrastructure is essential for developing robust approaches to increasing resilience. Identifying specific vulnerabilities allows for better communication, planning, and situation-specific interventions. This is particularly relevant in areas recovering from a natural hazard that have the opportunity to build back their infrastructure, and for those currently planning infrastructure expansions. This study considers recent hurricanes, earthquakes, droughts, heat waves, extreme wind and rainfall events, ice and thunder storms as well as wildfires. For many of these, data are available for the same type of hazard in different geographies which provides information not only on specific vulnerabilities, but whether the impacts are location dependent. Where available, specific design considerations, cost information for repairs, and the recommendations for ‘building back better’ are presented. Above-ground transmission systems were the most commonly affected power system component, with fuel and maintenance supply chains representing a major vulnerability for isolated regions and islands. Generation systems were most commonly affected when a hazard exceeded design limits, particularly in relation to water temperature or wind speeds. Institutional capabilities are important throughout the sector. In all case studies analyzed, the design standards of the infrastructure asset, and the ongoing maintenance of assets and the organized response (or lack of) has major implications for the performance of the electricity grid.

This paper is a product of the Global Facility for Disaster Reduction and Recovery, Climate Change Group. It is part of a larger effort by the World Bank to provide open access to its research and make a contribution to development policy discussions around the world. Policy Research Working Papers are also posted on the Web at http://www.worldbank.org/ prwp. The authors may be contacted at aschweikert@mines.edu.

_The Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about development issues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry the names of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank and its affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent._ Produced by the Research Support Team
# **Resilience and Critical Power System Infrastructure: Lessons learned from natural disasters and future research needs**

**Amy Schweikert**<sup>**1,2**</sup> **, Lindsey Nield**<sup>**2**</sup> **, Erica Otto**<sup>**2**</sup> **, Mark Deinert**<sup>**1,2**</sup>

- 1The Payne Institute for Earth Resources, Golden, Colorado, USA

- 2The Colorado School of Mines, Golden, Colorado, USA

**Keywords** : Critical infrastructure, Resilience, Natural hazards

**JEL classification:** Q54, H54, O13
# **Executive Summary**

Resilience against infrastructure failure is essential for ensuring the health and safety of communities during and following natural hazard situations. The Swiss Reinsurance Company Ltd (Swiss Re) estimated 2017 global infrastructure losses at 337 billion USD, with all but 7 billion resulting from natural hazards. (Of this, more than half was uninsured.) These losses are expected to grow as climate change continues unless actions are taken to prevent them. Importantly, people and communities in developing and emerging economies are expected to be disproportionately affected.

An understanding of how natural hazards impact society in terms of economic cost, recovery time, and damages to critical infrastructure is essential for developing robust approaches to increasing resilience. Identifying specific vulnerabilities allows for better communication, planning, and situation-specific interventions. This is particularly relevant in areas recovering from a natural hazard that have the opportunity to build back their infrastructure, and for those currently planning infrastructure expansions.

This paper<sup>1</sup> , commissioned by the World Bank’s Global Facility for Disaster Reduction and Recovery, looks at a range of historical natural hazard events and their impact on power system infrastructure including: generation facilities, transmission and distribution assets, and fuel supply chains. We consider recent hurricanes, earthquakes, droughts, heat waves, extreme wind and rainfall events, ice and thunder storms as well as wildfires. For many of these, data are available for the same type of hazard in different geographies which provides information not only on specific vulnerabilities, but whether the impacts are location dependent. Where available, specific design considerations, cost information for repairs, and the recommendations for ‘building back better’ are presented.

Within the three categories in the power system, we identify specific areas that require attention: 1) Generation facilities: affected by access to cooling water, preemptive shutdowns when winds exceed design limits, or structural damage from insufficient design.

2) Transmission grids: affected by wind, debris, ice, fire, flood, earthquakes and landslides. Above ground systems tend to be the most vulnerable.

3) Fuel and maintenance supply chains: affected by port closures, damage to roads and pipelines.

In some events, all or many of the assets in each of the categories were affected. In jurisdictions such as the Philippines or Puerto Rico, these events caused catastrophic failure of the electrical grid, and resulted in impacts to livelihoods and wellbeing. These situations help highlight which regions are well-prepared for events as well as their ability to respond and repair damages. Above-ground transmission systems were the most commonly affected power system component, with fuel and maintenance supply chains representing a major vulnerability for isolated regions and islands. Generation systems were most commonly affected when a hazard exceeded design limits, particularly in relation to water temperature or wind speeds. Institutional capabilities are important throughout the sector.

In all case studies analyzed, the design standards of the infrastructure asset, and the ongoing maintenance of assets and the organized response (or lack of) has major implications for the performance of the electricity grid.

> 1 This paper is the result of a contract with the World Bank’s Global Facility for Disaster Reduction and Recovery division focused on providing background on the state of understanding related to the vulnerability of power grid system and components to natural hazard events. This include generation facilities, supply chains, transmission networks. The goal of this analysis is to inform resilient planning of power grid systems.

2
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(with other sectors and services) and how to mitigate them.

Implementing the above recommendations will generate data to better inform power system planning and resilience of critical infrastructures that couple to them. The work will also provide data that is critical to optimizing the allocation of funds targets to increasing resilience.

# **Report Structure**

The report is organized into five sections with related appendices. Section 1 gives a brief introduction to resilience planning. Section 2, Methodology, provides an overview of the types of data looked at and analysis completed. Section 3 provides the results of the analysis related to the vulnerability of electricity system components and the costs and impacts when affected by different hazard events. This includes transmission and distribution infrastructure and fuel-specific generation facilities. Where applicable, the investigation of vulnerabilities includes the interdependencies of the electricity system including supply chain considerations and repair and maintenance interconnections. Section 3 also provides recommendations for more resilient infrastructure assets and, where available, the costs of doing so. Section 4 includes a detailed case study looking at the impacts, adaptations and costs of Hurricanes Maria and Irma on the power grid in Puerto Rico. Section 5 provides a summarized conclusion of the findings and outlines areas for future work. Appendices A-F provide supplemental information presented in this report, from definitions of terms to additional detailed, case study data. Appendices D and E additionally provide baseline and ‘build back better’ estimates specific to Puerto Rico.

4
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commercial and industrial customers, with costs ranging from $466 to $742 for a one-hour outage, with the lowest costs found on weekends and during the winter season and the highest costs found in summer and on weekends. The same patterns are found for medium and large commercial and industrial customers, though at higher costs: averaging between $4,190 (weekends) to over $16,000 (weekday outages and summer outages) (Sullivan et al. 2018). The tool is not designed for resiliency planning, especially for events lasting more than twenty-four hours or outside the United States. Nonetheless it could provide a baseline assessment method for resiliency investment and planning and is the focus of recent work comparing generator costs and other aspects of resiliency in post-event evaluations.

Much of the recent work related to power system resiliency has been focused on cyber-security<sup>3</sup> . While a valuable body of research and an important consideration in power system design, this falls outside the scope of the present study and should be a considered in resilience planning, particularly for smart grid systems. Here we focus on understanding component and system vulnerabilities to a wide range of natural disasters found through case study assessments.

# **2.0 - METHODOLOGY**

We consider the power system impacts of earthquakes, wild fires, hurricanes, droughts, floods, heat waves, as well as snow, ice, wind and thunder storms. The assets investigated include transmission and distribution infrastructure (e.g. substations, wires, and poles) as well as fuel-specific generation facilities. The data for the events studied falls into three general categories: hazard event case studies with multiple data sources covering many assets within a power system; single-facility operation disruptions from weather or water-related issues in the United States (McCall, Macknick, and Macknick 2016) or globally (Karagiannis et al. 2017a); major outage events in the United States between 2000 and 2016 focused on the cause of the disruption and customers affected (Mukherjee, Nateghi, and Hastak 2018c). The latter data were limited to customers affected, and the causal event. Where possible, cost estimates to repair damage back to operational capacity was recorded as were recommendations to improve performance. The types of events for which case study level data were available for different hazard events are summarized in Table 1.

This paper does not specifically address the impacts of climate change but instead focuses on empirical assessment of past hazard events and their impacts on the electrical power grid. Many studies cite that the impacts of a changing climate may increase the severity or intensity of natural hazard events and should be considered in the planning of new infrastructure (e.g. Meyer et al. 2013). Some examples of ways to incorporate climate change considerations in planning can be found, including a 2016 study of vulnerabilities of power system infrastructure to flooding (Chattopadhyay et al. 2016) and others focused on different types of critical infrastructure (Schweikert, Espinet, and Chinowsky 2018). This is an important consideration for future work and discussed in the recommendations at the end of this work.

**Table 1: Case Study Summary** - Over 50 events and more than 700 outages were investigated in this analysis. The 13 events detailed in this table represent analyses that covered multiple infrastructure assets and sources to provide a picture of the impacts of a specific natural hazard event on the electric power <u>system in the affected region.</u>

||**Number**|||||**Damaged Assets**|
|---|---|---|---|---|---|---|
|**Hazard**|**of Case**|**Event Name**|**Date**|**Location**|**Severity**|**(for which data**|
||**Studies**|||||**was available)**|

3 For more information on this important consideration, several resources are available, including The United States’ Department of Energy Office of Cybersecurity, Energy Security, and Emergency Response (CESER)(Department of Energy n.d.).

7
|Earthquake|2|Christchurch<br>Earthquake<br>N/A|2011<br>2011|<sup>Christchurch,</sup><br>New Zealand<br>Virginia,<br>United States|Magnitude 6.3<br>Magnitude 5.8|Transmission<br>lines, substations,<br>backup generators<br>No damages,<br>curtailment of<br>generation<br>facilities|
|---|---|---|---|---|---|---|
|||Typhoon<br>Haiyan/Yolanda|2013|The<br>Philippines|Category 5|Transmission<br>lines, poles,<br>substations,<br>geothermal plant,<br>oil barge|
|||Hurricane Sandy|2012|Northeast,<br>United States|Post-tropical<br>cyclone|Transmission<br>lines, distribution<br>system, fuel<br>generation plants,<br>supply chain<br>infrastructure|
|Hurricane/<br>Typhoon|4|Hurricane Maria|2017|Puerto Rico|Category 4|Transmission grid,<br>distribution<br>system, generation<br>facilities, ports,<br>supply chain<br>infrastructure|
|||Hurricane Maria|2017|U.S. Virgin<br>Islands|Category 5|Transmission grid,<br>distribution<br>system, generation<br>facilities, ports,<br>supply chain<br>infrastructure|
|||Hurricane<br>Harvey|2017|Texas,<br>United States|Category 4|Transmission grid,<br>ports,refineries|
|Drought/<br>Heatwaves|2||2011<br>2018|Texas,<br>United States<br>France|D4<br>("Exceptional")|Thermoelectric<br>plants<br>(curtailment)<br>Generation<br>facilities<br>(curtailment)|
|Wildfires|1||2007|California,<br>United States|33,195 acres<br>burned|Transmission<br>lines, generation<br>facilities<br>(curtailment)|
|||Tropical Storm<br>Dolores|2015|California,<br>United States|Heavy rainfall,<br>lightning|Transmission lines|
|Storm|4|Thunderstorm|2013|Virginia,<br>United States|Strong winds|Transmission lines|
|||Thunderstorm|2015|Minnesota,<br>United States|Wind, heavy<br>rain|Transmission<br>poles,<br>transmission lines,<br>transformers|

8
|||||damaged|
|---|---|---|---|---|
|Snow/ice|2014|Maryland,<br>United States|Ice|Transmission lines|

9
# **3.0 - VULNERABILITIES AND FAILURES**

The following results consider all reviewed data including outage information, facility-specific curtailments and case studies. Table 2 presents the major outages in the United States (2000-2016) summarized by cause. Half of all events are attributed to natural hazard events. Notably, where outages were due only to damage to operability disruptions, more than half of all classified events were due to the transmission and distribution infrastructure.

<u>Mukherjee, Nateghi, and Hastak (2018)</u> examined the cause, location, duration and impact (MW lost, customers affected) of every major electrical outage in the United States between 2000-2016. Over 1,500 events were included in the dataset, and each outage event was categorized by the major cause. Fifty percent of all major outage events in the examined period were due to natural hazard events, Table 2. System Operability Disruptions account for approximately 8% of outages, of which more than 50% were transmission/ distribution interruptions issues (where classified). Fuel Supply Emergency caused outages 3% of the time, with data on the fuel type for each outage: coal (35%), hydroelectric facilities (12%), natural gas (14%) and petroleum (2%) and unknown accounting for the rest.

McCall et al. (2016) examined the impact of water-related issues on generation facility operation. It focused on all water-related curtailments in the United States between 2000-2015. A total of 37 events were recorded for nuclear, coal and hydroelectric facility operations.

The majority of curtailments occur due to water intake and/or discharge issues related to water temperature (>90%) with many of these (79%) occurring during heatwave/drought conditions. Specific design and operation parameters associated with environmental regulations and permitting were the major cause of curtailment (water temperatures

**Table 2 - Major Outages in the Continental United States** (2000-2016), summarized from Mukherjee et al. 2018.

|**Cause**|**Percent of all**<br>**events**|
|---|---|
|**Natural Hazards**|**50%**|
|Hurricane|10%|
|Heat Wave/Drought|1%|
|Earthquake|<1%|
|Winter Weather|18%|
|Flooding|<1%|
|Wind|11%|
|Wildfire|1%|
|Storm|29%|
|**Fuel Supply Emergency**|**3%**|
|Coal|35%|
|Hydroelectric|12%|
|Natural Gas|14%|
|Petroleum|2%|
|**System Operability**<br>**Disruptions**|**8%**|
|Classified events:<br>Transmission<br>Distribution|54%|
|**Intentional Attack**|**27%**|
|**Other**|**11%**|

exceeding permitted levels and/or water availability). The remaining curtailments are attributed to winter weather (McCall et al. 2016).

When combined with the case studies assessed in this analysis, similarities were found across geographies, hazard events and other parameters that might affect design standards, policy practices and cost considerations. Three general categories with common corresponding causes were identified in the vulnerability of the power grid system: 10
# 1) Transmission grid failures

- a. Wires above ground ruined by wind, debris, snow, ice, flood, fire, or earth movement

- b. Wires below ground affected by flooding, liquefaction, landslide, but much less vulnerable overall than above ground

# 2) Generator failures

- a. Limited access to cooling water or water of low enough temperature

- b. Hazard events that exceed operational limits

- c. Hazard events that exceed structural limits

- d. Flood or earth movement

- 3) Fuel and maintenance supply chain failures

- a. Port closures for fuel delivery

- b. Pipeline damage for fuel delivery

- c. Road damages for fuel delivery / repair operations

- d. Backup generators requiring diesel stored on site

A detailed description of the findings which lead to the above vulnerabilities is given below by subsystem component: first for transmission grid and then by fuel type, which includes both the generation facility vulnerabilities and supply chain considerations. In each section vulnerabilities to infrastructure and supply chain are given as well as possible methods to increase resiliency.

# **3.1 – Transmission Grid**

_Vulnerabilities._ In nearly every case study, Table 1, transmission infrastructure represented the most vulnerable part of the power system. Particularly in geographies with less redundant systems, the time required to restore transmission lines constituted the majority (or sole) reason for the lag in recovery time. This was seen in Puerto Rico, where restoration of power across the island took nearly a year despite many solar and other generation facilities’ quick recovery times (U.S. Energy Information Administration 2018) (see Section 3.3).

Transmission lines are vulnerable to most meteorological impacts of a hazard event, including wildfires, high winds, freezing rain, snow, earth movement (liquefaction, earthquake, landslides) and debris. The most common vulnerability and damages occurred from wind resulting from hurricanes, storms, winter weather or debris picked up by wind. All infrastructure in earthquake areas where liquefaction occur saw damages (Watson 2013). Wind was found in many case studies to topple transmission lines and poles (Thompson 2011; Sinclair Broadcast Group 2013; Hoffman and Bryan 2013; Sinclair Broadcast Group 2012; Dispatch 2015).

Wildfires present an interesting and unique vulnerability to transmission and distribution infrastructure. Various case studies illustrate that during high risk conditions (drought, high temperatures, high wind), curtailments were used to reduce the risk of transmission infrastructure causing a wildfire. The potential risk was illustrated in California (USA) in 2017 when transmission lines were identified as a likely cause of fire start. Here San Diego Gas & Electric was found liable for causing three fires that led to three deaths and the destruction of 1,300 homes. The utility ultimately paid out $2 billion in settlements (Daniels 2017). Recent wildfires have put Pacific Gas and Electric, a large utility in California, under scrutiny due to $10 billion in liabilities from fires in 2017 and unknown amounts from ongoing fires in 2018 (McNeely 2018). A key parameter in overall grid vulnerability was the geographic distance between generation facilities and end-use. Summary vulnerabilities identified in the case studies are detailed in Table 3, with detailed case study data presented in Appendix B and C.

11
Transmission infrastructure was also seen to be acutely dependent on other infrastructure for its recovery, e.g. transportation, because equipment and materials must be brought to each site for repair. Specific design standards identified to reduce the vulnerability of the grid and the costs are summarized in Table 4.

|**Table 3: Tran**|**smission Grid and Distribution I**<br>|**nfrastructure, Ke**<br>|**y Vulnerabilities**<br>||
|---|---|---|---|---|
||Hurricane|WinterWeather|Wildfires|Earthquake|
|Transmission<br>and<br>Distribution|* Wind damage can topple lines<br>and poles(Thompson 2011;<br>Sinclair Broadcast Group 2013;<br>Hoffman and Bryan 2013;<br>Sinclair Broadcast Group 2012;<br>Dispatch 2015)<br>* Damage to transmission<br>tower foundations due to<br>erosion and/or landslides<br>(Karagiannis et al. 2017b)<br>* Moisture and dirt infiltration<br>(Karagiannis et al. 2017b)<br>* Inaccessibility due to<br>flooding (Hoffman and Bryan<br>2013)<br>* Substations at risk of flooding<br>(New York Power Authority et<br>al.2017)|Icing on<br>transmission<br>lines|* Damaged power<br>lines can cause<br>fires and fires can<br>damage<br>transmission lines<br>causing power<br>outages (Rogers<br>2017)<br>* Trees falling on<br>power lines due to<br>strong winds can<br>spark fire (Daniels<br>2017)|*Vulnerable<br>to liquefaction<br>(N. Watson<br>2013)<br>*Landslide<br>*Buried lines<br>vulnerable to<br>flooding|

_Resilient Design Guidelines._ The design parameters used for transmission and distribution infrastructure relate directly to their performance during and after a natural hazard event. In New Zealand, case studies following the earthquakes in 2010-2011 highlight the value of pre-emptive investment in infrastructure. Estimates show that $6 million spent to harden transmission and distribution infrastructure resulted in $30-50 million reduction in direct asset replacement costs (Fenwick and Hoskin 2011). Specific to a case study performed in Puerto Rico, detailed data can be found in Appendix D and E.

12
|**Table 4**|**– Transmission and Distributi**<br>Hurricane|**on, Resilient Desig**<br>Earthquake|**n Guidelines**<br>Wildfires|
|---|---|---|---|
|Transmission<br>and<br>Distribution|* Poles and towers should be<br>of design and material to<br>survive 240 kph sustained<br>winds (U.S. Department of<br>Energy 2018b)<br>* Enable integration of<br>microgrids (New York Power<br>Authority et al. 2017)<br>* Build flood barrier around<br>site based on observed worst<br>case flooding plus a foot or<br>more for design safety<br>margin (New York Power<br>Authority et al. 2017)<br>* All critical electricity<br>system assets should be<br>located at BFE +1 meter or<br>0.2% flood elevation or sited<br>outside of the floodplain<br>entirely (U.S. Department of<br>Energy 2018b)<br>* Build substations at higher<br>elevations<sup>[66]</sup><br>* Poles should have deeper<br>subgrade support to<br>withstand min. 1 meter of<br>water (New York Power<br>Authority et al. 2017)<br>* Towers in Philippines only<br>designed to withstand winds<br>of 185 kph while Yolanda<br>had winds greater than 220<br>kph (Rappler.com 2013)|* Build to<br>withstand events<br>greater than<br>events in the past<br>and update aging<br>infrastructure (N.<br>Watson 2013)<br>* Determine<br>threshold of<br>acceptable risk<br>and cost<br>increment.<br>(Stevenson et al.<br>2011)<br>*Upgrade major<br>cables,<br>switchyards, and<br>substations to<br>seismic standards<br>(Fenwick and<br>Hoskin 2011)|* Harden grid by<br>replacing wooden<br>poles with steel<br>ones, better<br>insulating power<br>lines, and burying<br>power lines<br>(Rogers 2017)<br>* Be aware of<br>max winds towers<br>and poles can<br>withstand<br>(NDRRMC 2014)<br>* Turn off power<br>lines in time of<br>high fire risk to<br>prevent wildfires<br>(Daniels 2017)|

# **3.2 – Generation Plant Vulnerabilities by Fuel type**

Generation plant vulnerabilities were investigated using case study and curtailment data. By comparing impacts across geographies and hazards, specific guidelines about resilience (or lack the of) of specific power generation systems (fuel types) can be made. The following sections are organized by fuel type (petroleum, coal, natural gas, nuclear, solar and others (including Wind, Hydroelectric, Backup Diesel Generators, Geothermal). For each fuel type, vulnerabilities are detailed specific to the facility and the supply chain or interdependent infrastructure. Additionally, where information was available, the costs of damages and impacts are detailed from specific case studies along with recommendations for more resilient design. A comprehensive case study of component level damages and corresponding baseline and build back better costs are provided in Section 4 specific to Puerto Rico.

13
_3.2.1 - Oil-Fired Generation Facilities_ . Oil-fired generation facilities are generally used for small proportions of overall electricity generation within a larger system and represent facilities constructed before 1980. This is due to relatively higher costs of fuel when compared to natural gas or other similar sources (Dubin 2017). The largest natural hazard vulnerabilities are from hurricanes, droughts and heatwaves (see Table 5).

||**Table 5: Oil-Fired (Petroleum) Generation Faciliti**<br>|**es, Impacts from Case S**<br>|**tudies**<br>|
|---|---|---|---|
||Hurricane|Drought/Heat Wave|Flooding/Storm<br>Surge|
|Direct<br>impacts|* Damage to plant infrastructure due to high winds<br>and flooding (New York Power Authority et al.<br>2017)<br>* Cooling tower damage (New York Power<br>Authority et al. 2017)<br>* Power barges off shore at risk to strong winds and<br>storm surge (Joint UNEP/OCHA Environment Unit<br>2013)|* Low water levels to<br>be used for cooling and<br>high temperatures<br>(25°C) that regulations<br>prevent from being<br>discharged (Harto and<br>Yan 2011)|* Refineries shut<br>down due to heavy<br>rainfall and flooding<br>(Hoffman and<br>Bryan 2013)|
|Supply<br>chain<br>effects|* Damages to ports can disable supply chain (where<br>imports are required for fuel delivery) (New York<br>Power Authority et al. 2017)<br>* Damages to pipelines, roads can disrupt fuel<br>delivery to generation facilities|||

Facility vulnerabilities for oil-fired generation were identified in some studies (including Puerto Rico). Plants were damaged due to high winds, specifically of the cooling tower structure. In two case studies reviewed, damages from wind, storm surge and flooding shut down the facility and caused costly damaged (see also Section 4 of this report) (Hoffman and Bryan 2013; Joint UNEP/OCHA Environment Unit 2013). During Typhoon Haiyan in the Philippines, the Estancia Oil Barge was ripped from its moorings offshore, causing an oil spill along the coastal areas (Joint UNEP/OCHA Environment Unit 2013).

_Supply Chain and Interdependencies for Oil-Fired Generation Facilities_ . The main vulnerabilities identified in supply chain and interdependencies with oil-fired capacity is the supply chain of fuel and water required for cooling. Facilities require petroleum (or petroleum products) to operate, with delivery relying on pipelines, roads, and/or ports for delivery. In cases where these interdependent infrastructures are damaged, plant operation is reduced or shut down completely (New York Power Authority et al. 2017). This was seen in Puerto Rico following Hurricanes Irma and Maria, where port closures resulted in an estimated loss of 1.2 million barrels per day of petroleum, over the course of 11 days, and directly affected the major generation stations which relied exclusively on imported fuel types (U.S. Department of Energy 2018a). Similar closures occurred in Texas during the same events in 2017 as well as in New York and New Jersey during Hurricane Sandy (U.S. Department of Energy 2018a). In Hurricane Sandy, it was noted that, “Due to its harbour and terminal infrastructure, the oil and gas supply chain is particularly prone to storm surges. At the same time, it is greatly dependent on secure power supply. Due to power outages, infrastructures such as pipelines, oil terminals, storage tanks and filling stations could hardly 14
**Table 7: Coal Facility Generation, Key Vulnerabilities**

||Drought/HeatWave|
|---|---|
|Direct<br>impacts||
|Supply chain<br>effects|Low water levels to be used for cooling and high temperatures (25°C) that regulations<br>prevent frombeing discharged (HartoandYan 2011)|
|function” (Com|es and Van de Walle 2014).|

All oil-fired facilities reviewed rely on intake water for circulation in the cooling systems and are vulnerable to flooding, storm surge, high temperatures of intake water and low amounts of water availability for intake water. In most case studies, permitting regulations resulted in curtailment or closure of facilities when intake water exceeded the permitted temperatures (approximately 75 degrees Fahrenheit in most studies) (McCall, Macknick, and Macknick 2016).

_Costs, Impacts and Resilient Design Considerations for Oil-Fired Generation._ Flooding and inundation can be mitigated by putting facilities at elevation and away from coastal regions. Hardening facilities to withstand the highest predicted winds, or other stressing events, expected during a facility lifetime can protect against structural damage. The cost to repair damaged facilities depends significantly on what was damaged, but at the high end would be the replacement cost. A summary of costs and recommendation from relevant studies is summarized in Table 6.

**<u>Table 6 - Oil-Fired (Petroleum) Generation Facilities, Costs and Resilient Design Guidelines</u>**

|Hurricane|Drought/Heat Wave|
|---|---|
|Oil_Estimated Cost:_$718,000/MW to repair PREPA (Puerto Rico)<br>oil generating facilities (New York Power Authority et al. 2017)<br>_Design Guidelines:_<br>* Locate facilities away from coast to avoid flooding from<br>coastal storm surge (New York Power Authority et al. 2017)<br>* Elevate facilities (U.S. Department of Energy 2018b)<br>* Design to withstand Category 4-5 wind speeds 210 kph (U.S.<br>Department of Energy 2018b)|* Install power mix that<br>doesn't all depend on water<br>for generation (Alvaro 2018)|

_3.2.2 - Coal-Fired Generation Facilities_ **.** Coal fired generation facilities are most vulnerable to droughts, heatwaves, and supply chain considerations (see Table 7). Flooding was identified as an important criteria for resilient facility design and a 2016 study in Bangladesh particularly noted that the historical guidelines for flood design are likely to be inappropriate for future conditions (Chattopadhyay et al. 2016).

Vulnerabilities of Coal-Fired Facilities were found to be similar to those for oil-fired ones. Findings specific to the assessed case study literature are summarized in Table 7.

_Supply Chain and Interdependencies for Coal-Fired Generation Facilities._ Similar to petroleum and natural gas facilities, coal generation plants require on-demand fuel delivery, although typically plants have some on site reserve available. In the United States, between 2000-2016, 35% of all outages related to a fuel supply emergency were for coal generation facilities, the largest of any fuel type (see Table 2). In a study in Bangladesh, additional vulnerabilities identified in the supply chain included the mining, 15
transportation and storage of coal vulnerable to natural hazard events including flooding (Chattopadhyay et al. 2016).

All facilities reviewed rely on intake water for circulation in the cooling systems and are vulnerable to flooding, storm surge, high temperatures of intake water and low amounts of water availability for intake water. In most case studies, permitting regulations resulted in curtailment or closure of facilities when intake water exceeded the permitted temperatures (approximately 75 degrees Fahrenheit in most studies) (McCall, Macknick, and Macknick 2016). In a study that includes climate change considerations, thermal electric power stations (including coal) were identified to have increasing vulnerability in the future specifically due to increased ambient temperatures and water availability that will affect water required for cooling (Chattopadhyay et al. 2016).

_Costs, Impacts and Resilient Design Considerations for Coal-Fired facilities._ As with oil-fired capacity, flooding and inundation can be mitigated by putting facilities at elevation and away from coastal regions. Hardening facilities to withstand the highest predicted winds, or other stressing events, expected during a facility lifetime can protect against structural damage. The cost to repair damaged facilities depends significantly on what was damaged, but at the high end would be estimated by the replacement cost.

_3.2.3 – Natural Gas-Fired Generation_ **.** Natural gas fired generation facilities are most vulnerable to droughts, heatwaves, and supply chain considerations (see Table 8).

|**Table 8: NaturalGas Facility Generation, Key Vulne**<br>|**rabilities**<br>|
|---|---|
|Drought/HeatWave|Hurricanes|
|* Low water levels to be used for cooling and high<br>temperatures that regulations prevent from being<br>discharged (HartoandYan 2011)|*Broken pipelines limiting gas<br>distribution (Hoffman and Bryan<br>2013)|

_Supply Chain and Interdependencies of Natural Gas-Fired Generation._ The main vulnerabilities identified in supply chain and interdependencies with natural gas plants is the supply chain of fuel and water required for cooling. Facilities require liquid natural gas (or other fuel product) to operate, with delivery relying on pipelines, roads, and/or ports for delivery. In cases where these interdependent infrastructures are damaged, plant operation is reduced or shut down completely (New York Power Authority et al. 2017). This was seen in Puerto Rico following Hurricanes Irma and Maria, where port closures directly affected the major generation stations which relied exclusively on imported fuel types (U.S. Department of Energy 2018a). Similar closures occurred in Texas during the same events in 2017 as well as in New York and New Jersey during Hurricane Sandy (U.S. Department of Energy 2018a).

All facilities reviewed rely on intake water for circulation in the cooling systems and are vulnerable to flooding, storm surge, high temperatures of intake water and low amounts of water availability for intake water. In most case studies, permitting regulations resulted in curtailment or closure of facilities when intake water exceeded the permitted temperatures (approximately 75 degrees Fahrenheit in most studies) (McCall, Macknick, and Macknick 2016). In the 2011 Texas drought, lack of water available for cooling resulted in curtailment of production from all thermoelectric plants, resulting in increased prices to consumers (EIA 2011; Harto and Yan 2011).

_Costs, Impacts and Resilient Design Considerations of Natural Gas-Fired Generation._ As with oil and coal-fired capacity, flooding and inundation can be mitigated by putting facilities at elevation and away from coastal regions. Hardening facilities to withstand the highest predicted winds, or other stressing events, expected during a facility lifetime can protect against structural damage. The cost to repair damaged facilities depends significantly on what was damaged, but at the high end would again be the 16
replacement cost. Costs and resilient design guidelines are summarized in Table 9.

**Table 9 – Natural Gas, Costs and Resilient Design Guidelines**

|Drought/Heat Wave|
|---|
|<br>Install power mix that doesn't all depend on water for generation (Alvaro 2018)<br><br>air cooling<br><br>backup cooling water supplies<br><br>put facilities at elevation to avoid flooding<br><br>avoid coastal regions.|

_3.2.4 – Nuclear-Fired Generation._ Nuclear power plants are built to robust design standards, reducing the impacts of most events (such as high winds, storms). The only nuclear power plant curtailments or shut downs observed, except for one, in this analysis occurred because of pre-emptive closure (in the case of predicted hurricane-force winds and/or storm surge for coastal plants) or issues with the intake water used for cooling. The primary cause seen for the pre-emptive closures were hurricanes, while issues with intake water used for cooling were caused by drought, heatwaves, and winter weather (see Table 10). The only power plant reviewed that sustained damage was the Fukushima Daiichi Plant in Japan following a magnitude 9 earthquake and tsunami, which was considerable.

Nuclear power plants are the most robust generation type reviewed in terms of facility design and limited reliance on the fuel supply chain. This was particularly evident in Texas following Hurricane Harvey where nuclear power was able to operate at full capacity throughout the event. This allowed for continued electricity supply despite the demand deficit seen from reductions in generation facilities located on the coast which were more affected by storm surge and flooding for longer time periods (Conca 2017).

|**Table 10: Nuclear Power Plants, Key Vu**<br>|**lnerabilities**<br>||
|---|---|---|
|Hurricane|Drought/HeatWave|Earthquake|
|* United States safety procedures require<br>plants to shut down or reduce output<br>when hurricane-force winds 117 kph are<br>present or if water levels exceed certain<br>flood limits (Foro Nuclear)<br>* High water levels threaten cooling<br>units (Steve Mufson 2012)<br>* Automatically shut down if plant loses<br>power from grid (Steve Mufson 2012)|* Shut down or curtailed when<br>intake cooling water<br>temperature is too high (25°C)<br>(Harto and Yan 2011)<br>* Shut down or curtailed when<br>discharge temperature is too<br>high due to local environmental<br>regulations (Harto and Yan<br>2011)|* Automatically shut<br>down if plant loses<br>power from grid<br>(Mufson 2012)<br>* Damage occurs when<br>force exceeds design<br>basis (N. Watson 2013)|

Vulnerabilities of nuclear-fired facilities included power plant curtailments or shut downs. In all cases reviewed in this analysis, excluding Fukushima Daiichi plant, these occurred because of pre-emptive closure. Generally, these were due to predicted hurricane force winds or detected seismic levels exceeding a design threshold. Because of strict permitting and regulations in the United States, when plants were shut down pre-emptively, there was often a large lag time before being able to operate again. Inspections are required, particularly in the context of an earthquake. No damages were found to a nuclear facility in the studies reviewed for this analysis with the exception of the tsunami impact on the Fukushima Daiichi facility.

_Supply Chain and Interdependencies of Nuclear-Fired Generation._ Generation For nuclear power plants, fuel can be stored on site and refueling is far less than other power sources, ranging in the timescales of 17
years. The only identified impact on supply chain and interdependencies are when demand shifts and the water used for cooling. For demand shifts, nuclear power is not as quickly able to adjust power production as other technologies including natural gas. Generally, this is accounted for with forecasting and planning.

The largest vulnerability of nuclear power facilities is the intake water used for cooling. High temperatures can make it difficult for water to reach temperatures cool enough to be discharged and, due to permitting restrictions, may require generation curtailment (Galbraith 2011). A case study on the 2011 Texas heat wave was performed and augmented with facility-specific data for curtailments at several facilities, including a study finding 25 water-related curtailments in the United States between 2000-2015 (McCall et al. 2016). The impacts on power generation were similar across all data reviewed: water availability and temperature affected generation systems that rely on cooling water. The majority of curtailments occur due to water intake and/or discharge issues related to water temperature (>90%) with many of these (79%) occurring during heatwave/drought conditions. One example occurred for winter weather, where snow and ice restricted the amount of intake water available. Specific design and operation parameters associated with environmental regulations and permitting were the major cause of curtailment (water temperatures exceeding permitted levels and/or water availability). This was also seen in France in August 2018. Here four nuclear reactors were shut down because river temperatures were too high to allow for water discharge (Shugerman 2018).

_Costs, Impacts and Resilient Design Considerations for Nuclear-Fired Generation._ The key vulnerability of existing nuclear power plants is the reliance on intake water for cooling. The design guidelines for constructing a facility include seismic considerations (where applicable) and resilience to withstand high windspeeds, flooding, and other hazards, Table 11.

**<u>Table 11 – Nuclear Power Plants, Costs and Resilient Design Considerations</u>**

|Hurricane|Drought/Heat Wave|Earthquake|
|---|---|---|
|* Design plants to withstand<br>winds up to 580 kph (Reuters<br>2011)<br>* Steel reinforced concrete<br>containmentwith at least 1-<br>meter thick walls(Conca 2017)<br>* Build plants at higher<br>elevations (Steven Mufson<br>2012) <br>* Keep backup generators in<br>case of power failure (Steven<br>Mufson 2012)|* Install power mix that doesn't<br>all depend on water for<br>generation (Alvaro 2018)|* Build plants to withstand<br>earthquakes above maximum<br>magnitude recorded (N. Watson<br>2013)|

One modification that has been made is found in Arizona (USA): The Palo Verde plant. This facility does not sit on a body of water but instead uses recycled municipal water (APS 2018) and therefore operates under different rules for intake and discharge temperatures. This reliability on grey municipal water changes the regulations for cooling water and may provide an operational case study for future designs.

_3.2.5 – Solar Generation._ Solar generation facilities are unique in that they can operate at almost any size, from a single panel to large, utility-scale plants. In the case studies reviewed, the main vulnerability of solar was found to be high winds that damaged the panels, although this was directly related to the design standard they were built to. For detailed information, see Section 4.

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Although research is ongoing on the topic, solar (and other intermittent renewables) create a potential vulnerability in the electricity system. This was seen in Puerto Rico following Hurricanes Irma and Maria, where one solar facility was at operational capacity within a week, but curtailed from production for several months due to damages in the transmission grid and concerns about the stability of power production in the larger mix (U.S. Energy Information Administration 2018).

Solar Facilities were seen to be vulnerable to flooding (resulting in landslides or damage to foundations) and high winds. In Puerto Rico, four facilities were impacted by Hurricanes Irma and Maria, with three sustaining significant damage. The fourth facility was built to higher design standards and sustained less damage (see: Section 4).

_Supply Chain and Interdependencies of Solar Facilities._ The fuel supply chain vulnerabilities of renewables (wind, solar) are less vulnerable than traditional fuels relying on on-demand delivery. The uncertainty of weather and limited timescales for forecasting are areas for improved resiliency. Many case studies cited the use of solar panels following a hazard event for basic electricity provision, and the stockpiling and coordinated planning for post-disaster intermittent energy options was one recommendation for increasing resiliency (Fthenakis 2013; Ranada 2014a). Lack of transportation infrastructure would be limiting to their use in this capacity as well as to their repair.

_Costs, Impacts and Resilient Design Considerations of Solar Facilities._ The main case study where damages were observed is described in detail in Section 4 and highlights the importance of design standards in the resilience of utility-scale solar.

|**Table 12– Solar Power, Costs and Resilient Design Guidelines**|
|---|
|Hurricane|

* Panels and all components built at least 2 meters off the ground on mountings designed to avoid floods (Limperis 2017a)

- Panels reinforced to withstand Category 5 winds (250 kph) (Limperis 2017a)

* Need to be small and portable if being moved to areas in need (Ranada 2014b)

# _3.2.6 - Backup Diesel Generators_

_Vulnerabilities of diesel generators._ The most widely observed damages to diesel generators found in the analyzed case studies was due to flooding (Table 13). In some locations, diesel generators are stored in the basement of a facility; when flooding, storm surge, or other damages occur, the generators are inundated and become inoperable. Damage to diesel generators from flooding was a major contributor to the meltdown of reactors at the Fukushima Daiichi nuclear complex, where backup power would have extended the time for a response effort.

|**Table 13 –O**|**ther Fuel Generation Facilities, Key Vuln**<br>|**erabilities**<br>||
|---|---|---|---|
||Hurricane|Drought/Heat<br>Wave|Earthquake|
|Diesel<br>Generators|* Temporary relief and backup for other<br>power plants (NDRRMC 2014; Steve<br>Mufson 2012; Ardagh et al. 2012)<br>* Reliant on immediate on-demand fuel<br>supply (Powell, Hanfling, and Gostin<br>2012)||* Serve as backup<br>during times of grid<br>related power outages<br>(NDRRMC 2014;<br>Ardagh et al. 2012)<br>* Severe shaking can<br>cause sump sludge<br>which leads tofailures|

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(Ardagh et al. 2012)

# _Supply Chain and Interdependencies of diesel generators._

Diesel generators are often used as backup electricity when an outage occurs (NDRRMC 2014). Fuel is often stored on-site, but with longer outages or poor planning (such as not storing the fuel and generators in the same space), this can result in limited operation and have a significant impact on other critical facility operations that rely on electricity, such as hospitals or communication infrastructure (Powell, Hanfling, and Gostin 2012). In many examples, the co-location of fuel and generators is important (to minimize transport time and effort between generator and fuel required to operate).

_Costs, Impacts and Resilient Design Considerations of diesel generators._ The resilience of diesel generators was seen to depend on the ability to resist flooding and to have adequate fuel supply on hand.

**Table 14 – Resilient Design Considerations, Diesel Generators**

Flooding, (Hurricane, Storm Surge, Tsunami) Store fuel next to generators Store generators above predicted flooding levels (water, debris, mud)

# _3.2.7 – Other Renewables (Wind, Hydroelectric, Geothermal)_

Limited data was assessed for other important power generation technologies in terms of case study data, although this is an area for future work. Table 15 lists key vulnerabilities identified in this analysis for geothermal plants, hydroelectric plants, and wind farms.

|**Table 15 –O**|**ther Fuel Generation Facilities, Key Vuln**<br>|**erabilities**<br>||
|---|---|---|---|
||Hurricane|Drought/Heat<br>Wave|Earthquake|
|Geothermal|* Water and wind damage to cooling<br>towers (Rappler.com 2013)|||
|Hydro|* Mud and water damage to generation<br>plants (New York Power Authority et al.<br>2017)|* Low water<br>levels limiting<br>generation<br>capacity, forcing<br>closure (Alvaro<br>2018)||
|Wind|* Blades ripped from poles due to high<br>winds. Facilities are shut down when<br>wind speeds exceed set threshold<br>(typically 88 km/hour) (Conca 2017)<br>* Damage to vertical posts (New York<br>Power Authority et al.2017)|||

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|Diesel<br>Generators|* Temporary relief and backup for other<br>power plants (NDRRMC 2014; Steve<br>Mufson 2012; Ardagh et al. 2012)<br>* Reliant on immediate on-demand fuel<br>supply (Powell, Hanfling, and Gostin<br>2012)|* Serve as backup<br>during times of grid<br>related power outages<br>(NDRRMC 2014;<br>Ardagh et al. 2012)<br>* Severe shaking can<br>cause sump sludge<br>which leads to failures<br>(Ardagh et al. 2012)|
|---|---|---|

_Vulnerabilities of wind, hydro, and geothermal._ Wind farms were found to be particularly vulnerable to hurricane force winds and debris, resulting in damages in Puerto Rico and Texas. Damages to geothermal facilities in The Philippines were seen due to hurricane force winds and flooding resulting from Typhoon Haiyan.

_Supply Chain and Interdependencies of wind, hydro, and geothermal._ Hydroelectric facilities and diesel generators were seen to be heavily reliant on their supply chain for fuel – in this case, water and diesel gas, respectively. In Malawi, capacity was reduced by half because of low water levels at the largest hydroelectric plant during a 2017 drought and heatwave. Nearly all of Malawi’s electricity is generated through hydroelectric plants, highlighting a potential vulnerability if precipitation patterns change in the future. Similar impacts from drought and heatwaves were seen in Tanzania in 2015 and Mozambique in 2016 (Alvaro 2018). Hydroelectric plants account for 12% of all Fuel Supply Emergency outages in the United States in the period 2000-2015 (Table 2) (Alvaro 2018).

_Costs, Impacts and Resilient Design Considerations of wind, hydro, and geothermal._ The resilience of wind farms was found to depend in part on the wind velocity that the turbines were designed to withstand. Hydroelectric facilities were seen to be vulnerable to blockages, but also flooding (through potential erosion of dam structures). Repair costs were found to be dependent on damage type and extent. Design considerations from the studies considered in this analysis are summarized in Table 16.

**Table 16 – Other Generation Facilities, Costs and Resilient Design** **<u>Considerations</u>**

||Hurricane|Drought/Heat Wave|Earthquake|
|---|---|---|---|
|Wind|* Poles and blades<br>reinforced to withstand<br>Category 4-5 wind speeds<br>210 kph (U.S. Department<br>of Energy 2018b)|* Can help prevent outages water supply is<br>low (Scanlon, Duncan, and Reedy 2013;<br>Faeth 2013)||
|Hydro||* Install power mix that doesn't all depend<br>on water for generation (Alvaro 2018)||

# **SECTION 4.0 – PUERTO RICO CASE STUDY**

The Commonwealth of Puerto Rico is a set of islands in the Caribbean Sea southeast of the continental United States. It consists of several islands, with the majority of occupants on the largest and main island of Puerto Rico. Energy use in the Puerto Rico is about 1/3 the consumption per capita of the United States. The generation portfolio consists of many fuel types including coal, oil, natural gas and renewables including solar, wind and hydroelectric. The vast majority of electricity is generated using 21
fossil fuels, all of which are imported. The electricity sector is run by PREPA, a government run agency that owns the transmission and distribution infrastructure as well as ~ 85% of the main island’s generating capacity (U.S. Energy Information Administration 2018). In September 2017, Hurricanes Irma and Maria hit Puerto Rico and caused severe damage to all critical infrastructure, including the power grid. These events provide ideal case studies for understanding the impacts that a hazard can have on power infrastructure including: asset-level damages, interdependencies within the electricity grid system and with other critical infrastructures, the impact of supply chain disruptions, considerations for planning and policy, and the costs of building back better.

Hurricane Irma was a Category 5 storm that made landfall on September 6, 2017, and left 70% of electricity customers without power and damaged critical infrastructure (Campbell, Clark, and Austin 2017; New York Power Authority et al. 2017). On September 20, 2017, Hurricane Maria made landfall in Puerto Rico as a Category 4 storm with wind speeds of over 250 kph (Campbell, Clark, and Austin 2017). These storms caused catastrophic damage, especially to the electrical grid (Central Intelligence Agency 2018). Hurricane Maria brought torrential rainfall with a range of 38 to over 100 centimeters, resulting in widespread flooding across the island (Campbell, Clark, and Austin 2017). The northern coast was severely impacted as the rotation of the hurricane led to severe coastal storm surge, which coupled with major rain runoff from the central mountains resulting in sustained flooding (New York Power Authority et al. 2017). The damage was so extensive that even undamaged generators could not supply power (U.S. Energy Information Administration 2018). The damage resulted in electrical power outages to 90% of the island as well as loss of housing and infrastructure and contamination of potable water (Central Intelligence Agency 2018).

Puerto Rico’s Office of Emergency Management reported that the storms had incapacitated the central electric power system, decimating transmission and distribution lines across the island and caused widespread wind and flood damage to substation, distribution, and generating facilities (Campbell, Clark, and Austin 2017; New York Power Authority et al. 2017). Hurricane Maria was the worst storm to hit the island in over 80 years, and the cost of the damage is estimated in the tens of billions of dollars (Central Intelligence Agency 2018). The request for disaster recovery funds, submitted by the Governor of Puerto Rico Ricardo Rossello in November 2017, totaled just under a trillion dollars. The second largest category in this request, behind housing, was for nearly at nearly $18 billion to restore the power grid and increase resiliency (R. Rossello 2017).

Much of the island’s electricity is generated at power plants on the southern coast, while the largest population centers are in the north, making the system highly dependent on its 2,400 miles of transmission and 30,000 miles of distribution lines in the island’s forested, central mountain range (U.S. Energy Information Administration 2018). Due to staffing shortages at PREPA, no one had been cutting back the jungle growth on these south to north transmission lines (Ferris 2018). As a result, the combination of long distances, inaccessibility, and wind and tree damage led to a near total wipeout of the electricity grid when Hurricane Maria hit (Ferris 2018). In particular, transmission lines and towers in the center of the island were severely damaged by high winds that were funneled through changes in the terrain (New York Power Authority et al. 2017). In all, approximately 101 transmission line segments, 636 poles, and 673 conductors/insulators were damaged by the storm, Table 16 (New York Power Authority et al. 2017).

In early October 2017, only 20% of all transmission lines in Puerto Rico were functioning (Ferris 2018). Steep hills and muddy slopes in the north-south corridor made access to damaged transmission lines difficult, leading to repair times lasting up to a year in some locations (New York Power Authority et al. 2017). Virtually 100% of PREPA customers did not have power for over a week following the storm, and this slow pace of recovery meant that many customers were left without power for several months (U.S. Department of Energy 2018a).

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Generally, generating facilities were not as badly damaged as the transmission and distribution system (Table 15) (U.S. Energy Information Administration 2018). Most renewable generating facilities sustained modest amounts of damage (see Table 15); however, none of these facilities were able to connect to the power grid for several months (U.S. Energy Information Administration 2018). Small amounts of solar and hydropower were able to reconnect to the transmission system in late 2017; however, the first wind farm reconnected in February 2018 (U.S. Energy Information Administration 2018). Puerto Rico’s second largest solar farm and second largest wind farm were both badly damaged and are not expected to be in service until 2019 (U.S. Energy Information Administration 2018).

# **4.1 - Power Generation**

While Puerto Rico has some renewable solar, wind, and hydropower resources, the island has no reserves or production of conventional fossil fuels and primarily relies on imported fossil fuels (U.S. Energy Information Administration 2018). Approximately three-fourths of the energy used in Puerto Rico comes from petroleum products, most of which are imported through the ports of San Juan, Guayanilla, and Ponce (U.S. Energy Information Administration 2018). These ports were closed for 5 to 14 days following Hurricane Maria, leading to an estimated loss of 1.2 million barrels of petroleum per day during this period (U.S. Department of Energy 2018a).

# **Solar**

The experience of Puerto Rico’s solar farms in the aftermath of Hurricane Maria exemplify the importance of understanding the intra-system interdependencies and role that resilient designs can play in the vulnerability of systems. The extent of damages to transmission infrastructure was the primary driver of electricity recovery in Puerto Rico; specifically, different solar energy farms proved to have different levels of resilience during the 2017 Hurricane season in the Caribbean. While Hurricane Maria’s flooding rains and winds heavily damaged a few of Puerto Rico’s solar farms, including the second largest solar farm on the island where a majority of recently added solar panels were ripped from their foundations, many sites sustained minimal to no damage, Table 16 (Smith, 2017). The Illumina solar farm located on the southern coast is estimated to have lost a quarter of the modules from the 24 MW system to the storm (Limperis 2017). In contrast, there were hardly any damages to systems with adaptive designs (Limperis 2017). The solar farm in Loiza on the northern coast remained almost untouched by the hurricane (Limperis 2017). The panels at the site were specifically designed to outlast hurricanes: to prevent flood damage, each panel was built at least 2-meters off the ground and reinforced to withstand winds of Category 5 hurricanes (approximately 251 kph) (Smith 2017).

While a majority of solar farms sustained very little damage, a major factor preventing solar farms from exporting power to the grid was the complete destruction of the transmission and distribution system. This prevented sites from being able to reconnect to the grid and operate at full capacity. Apart from some torn away modules, Pattern Energy’s 101 MW Santa Isabel wind farm sustained minimal damage following the storm (Limperis 2017). While the farm lost power in the days following Hurricane Maria’s landfall, within a week, the farm informed Puerto Rico’s Electric Power Authority (PREPA) that it was ready to return to normal operations (Merchant 2018). However, over seven months after Hurricane Maria, generation remained 75 percent curtailed because of grid issues (Merchant 2018). Similarly, AES’ Illumina solar farm also was curtailed for months due to transmission work delays (Merchant 2018). Further, PREPA did not authorize the 24 MW solar farm in Guyama to begin exporting power to the grid until February 2018, and then only at 10% of the farms’ normal generation. Of particular concern was that solar power could create instability with the recovering transmission network in the area not able to support the amount of electricity potentially being fed into it (Gallucci 2018). Over a year after the storm, in October 2018, the site was only operating at 74 percent capacity (Gallucci 2018).

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|**Table 15:**<br>**Plant**<br>**Locatio**<br>**n**|**Summary**<br>**Gen.**<br>**Capacit**<br>**y**|**Damages to Solar Plants From 2017 Hurrica**<br>**Damages**|**nes, Puerto Rico**<br>**Design Specifications**|
|---|---|---|---|
|Humaca<br>o|44 MW|* The first phase of the solar farm, (finished<br>in 2016) fared relatively well (Limperis<br>2017)<br>* The solar modules of the northern<br>expansion still under construction,<br>consisting of 52 MW, were almost<br>completely ripped from their mountings<br>(Limperis 2017)<br>* Majority of newly added solar panels<br>ripped from foundation and completely<br>destroyed by winds (Smith 2017)|* System fitted with Fonroche<br>modules (Limperis 2017)|
|Guayam<br>a|24 MW|* Satellite imagery estimates a quarter of<br>modules were ripped from their mountings<br>by the storm (Limperis 2017)<br>* Site back to 74% generating capacity by<br>mid-October (Gallucci 2018)<br>* Curtailed because of transmission system<br>damage(Gallucci 2018)<sup>4</sup>||
|Loiza|27 MW|* Minimal damage (Limperis 2017)|* Panels and all components<br>(inverters, transformers) built<br>several (at least 2) meters off the<br>ground on mountings designed by<br>TSK to avoid floods (Limperis<br>2017)<br>* Reinforced to withstand<br>Category 5 winds (251 kph)<br>(Limperis 2017)<br>* Design withstood both the<br>hurricane and the torrential<br>rainfall well (Limperis 2017)|
|Isabela|58 MW|*Apart from occasionally torn away<br>modules, almost no damage was caused<br>(Limperis 2017)|<br>* Example of resilient design<br>(Limperis 2017)|

# **4.2 - Other Considerations**

The Puerto Rican government was facing challenges prior to the arrival of Hurricane Maria (Campbell, Clark, and Austin 2017). In the last decade, Puerto Rico’s economy has shrunk by over 15 percent, and this economic downtown has coincided with a sharp rise in the price of oil, which generates the majority of the island’s electricity (Central Intelligence Agency 2018). Prior to the 2017 hurricane season, the island’s electricity infrastructure was in poor condition, largely due to underinvestment and a lack of

> 4 Note: there are conflicting reports concerning the extent of damages at the Guayama wind farm. This highlights the need for more complete coverage of storm damages.

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maintenance (Campbell, Clark, and Austin 2017). PREPA’s electricity generators were 28 years older than that of the U.S. average, and the outage rates of these generators were 12 times higher than the U.S. average prior to the arrival of Hurricanes Irma and Maria (U.S. Energy Information Administration 2018). Only 15% of transmission lines on the island were built to Category 4 storm criteria (New York Power Authority et al. 2017).

# **4.3 – Resiliency and Building Back Better**

As repairs and rebuilding occur, PREPA has evaluated rebuilding resilience options (and has been the subject of several reports, including New York Power Authority et al. (2017), Rossello (2017), and Bloodgood and Martinez (2018)). Drawing on these and other sources, Table 16 provides asset-level estimates of costs for rebuilding damaged power infrastructure. Recommendations (where given) for rebuilding to a more resilient design standard are also included as are the estimated incremental costs of doing so. More detailed information is provided in Appendix E. Other resilience options are being explored; for example, Siemens Industry, Inc. (2018) presents a vision for mini-grid based systems designed to withstand outages better than an existing island-wide grid.

Results show that the cost of building back better, when compared to baseline estimates, varies greatly in magnitude based on the component. For example, hardening of the transmission grid (lines, poles, circuits) are generally relatively low incremental costs (~10%). Appendix D provides detail on the costs, damages, and baseline and resilient unit cost estimates for upgrading infrastructure design. Results show that there is approximately 3-40% increase in cost to upgrade transmission and distribution infrastructure to withstand Category 3 hurricanes, while there is a 24-70% increase in cost to upgrade to Category 4 hurricanes (130 mph sustained windspeeds). When wood poles (low windspeed design) are compared with tubular steel poles, for example, costs may increase as much as 200% (see Appendix D).

Table 16: Reported damages following 2017 Hurricane season in Puerto Rico. When available, costs represent estimates specific to the Puerto Rico grid (New York Power Authority et al. 2017). Where costs were not available, estimates were used from various sources _(see:_ <u>PG&E 2018; California ISO 2012; Curry and Wilson 2012)</u>

|<br>**Power System Component**|<br>**Transmissio**<br>**Struc**|**n Lines and**<br>**tures**|**Distribution**<br>**Cirit**|**Substations**|
|---|---|---|---|---|
||**115 kV**|**230 kV**|**cus**||
|Number damaged|84 Line<br>Segments, 230<br>Towers/poles|17 Line<br>Segments, 106<br>Towers/Poles|900|252|
|Baseline Unit Repair Cost|1.4/mile|1.6/mile|0.91/mile|$5.5 - $9.5<br>(depending on<br>capacity)|
|Build Back Better Unit<br>Cost|1.5/mile|1.9/mile|2.0/mile|15/substation|
|Incremental Better Unit<br>Cost|0.1/mile|0.3/mile|1.09/mile|277/substation|
|Incremental Better System<br>Cost|41*|13*|357*|4155*|

* _Note_ - not all costs add up exactly; much of the available information did not include cost information or exact miles (unit damages reported in segments or number of poles, while costs are given in miles). Estimates were made from available information. Where missing from Puerto Rico-

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specific documents, estimates were made using equivalent U.S. based design structure and components.

A final consideration for resilient infrastructure design is the incremental design costs relative to the probability that an event occurs over the lifetime of the infrastructure. While a full analysis of the power grid infrastructure in Puerto Rico and occurrence of hurricane-level storms is outside the scope of this paper, Table 17 provides an estimate based on historical storm occurrences since 1901. More detail is provided in Appendix D and E. Taken together, this information lays a foundation for a probabilistic risk assessment and cost-benefit analysis of different infrastructure investment decisions and is an area for future work.

Table 17: Summary statistics for windspeed events occurring in Puerto Rico, 1901-Present. Data for windspeed recorded in one-minute sustained wind speeds at approximately 100 meters above ground elevation. (For details on calculation, see Appendix E). _Data from:_ <u>National Centers for Environmental Information (2018)</u>

||Top Windspeed<br>for Category<br>(miles/hour)|Top Windspeed for<br>Category (km/hour)|Annual Prob.<br>Of 1 event|Number of<br>Storms since<br>1901|
|---|---|---|---|---|
|Tropical Storm|40-74|63-118|10.6%|14|
|Hurricane-Category 1|74-95|119-153|2.5%|3|
|Hurricane-Category 2|96-110|154-177|2.5%|3|
|Hurricane-Category 3|111-129|178-208|0.8%|1|
|Hurricane-Category 4|130-156|209-251|2.5%|3|
|Hurricane-Category 5|>156|>251|0.8%|1|

# **5.0 – SUMMARY OF FINDINGS**

# 5.1 – Power Grid Infrastructure

Generation plant vulnerabilities were the broadest area in our case studies. However, the data do suggest specific guidelines about resilience (or lack the of) of specific power generation systems (fuel types) in the context of specific hazards. For example, in Section 4, the performance of 4 solar photovoltaic farms in Puerto Rico are detailed to show how the design parameters of a system define the impact it sustains from a hurricane event. Similarly, in Section 3.1.3, transmission and distribution investments totaling $6 million made in New Zealand for higher seismic design standards are estimated to have saved Orion an estimated $30-50 million in direct asset replacement costs during the 2010-2011 earthquake events <u>(Fenwick and Hoskin 2011). In this context, an important finding is that more robust design standards</u> (such as a higher design threshold for wind speed) is directly related to performance during and after a hazard event. A next step in assessment would be to calculate the relative incremental cost of a more or less robust asset design and both the dividend in terms of performance in a hazard situation and the resilience dividend<sup>5</sup> .

> 5 The resilience dividend is defined as the value of more resilient infrastructure _in the absence_ of the event it is designed for. This can include things like aesthetics, job creation and performance in other events than the specific design threshold. It is similar to the idea of ‘co-benefits’, but explicitly tries to value to benefit to a community of spending more on infrastructure that is more resilient beyond the resilience to a specific event.

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A key finding in this study is the vulnerability of different generation technologies to the fuel supply chain. In a hazard situation, damage often occurs to other infrastructure systems including pipelines, roads, and ports. The interdependencies between these supply systems and others are important for understanding the impact a hazard has on society. Generation technologies that require on-demand fuel delivery notably include natural gas, oil, and coal fired systems. While some on-site reserve is typical with coal, it is less common for natural gas and oil-fired capacity making the supply chain of these systems vulnerable to many hazards. This was seen in Puerto Rico following Hurricanes Irma and Maria, where port closures resulted in an estimated loss of 1.2 million barrels per day of petroleum, over the course of 11 days, and directly affected the major generation stations which relied exclusively on imported fuel types (U.S. Department of Energy 2018a). Similar closures occurred in Texas during the same events in 2017 as well as in New York and New Jersey during Hurricane Sandy (U.S. Department of Energy 2018a). These fuel supply chain vulnerabilities are in contrast to renewable sources (wind, solar) and generations which keep a supply of fuel on hand (e.g. diesel generators used for short term backup) and those which require less frequent refueling (i.e. nuclear).

Four recent hurricane events and one typhoon event were investigated. These included Hurricane Sandy (Northeastern United States), Hurricane Harvey (Texas, United States), Hurricanes Irma and Maria (Puerto Rico and U.S. Virgin Islands) and Typhoon Haiyan/Yolanda (The Philippines). The recent hurricane events in Puerto Rico also resulted in several useful documents relating to the energy grid infrastructure and damages it sustained during the hurricane events. Particularly useful in this instance is a detailed assessment (New York Power Authority et al. 2017) of individual power generation stations, transmission line failures and design recommendations for recovery efforts. Puerto Rico provides an ideal case study for assessing power system vulnerabilities because of its isolated grid, its diversity in fuel generation technologies and the availability of information following the event. The recent hurricanes here can also be compared directly with impacts in the US Virgin Islands, a much smaller set of islands 180 kilometers east of Puerto Rico. The US Virgin Islands were hit by the same hurricanes, at similar or higher strength, and saw similar devastation to the power systems. Despite this, the rebuilding efforts, time, planning and other factors differ notably with those of Puerto Rico (e.g. U.S. Department of Energy 2018a). These events then present a unique opportunity to compare the recovery efforts and identify best practices related to preparation and building back better.

Drought and heat waves often coincide and may exacerbate the severity of both events. High temperatures can make it difficult for water to reach temperatures cool enough to be discharged and, due to permitting restrictions, may require generation curtailment (Galbraith 2011). A case study on the 2011 Texas heat wave was performed and augmented with facility-specific data for curtailments at several facilities. The impacts on power generation were similar across all data reviewed: water availability and temperature affected generation systems that rely on cooling water. This was also seen in France in August 2018. Here four nuclear reactors were shut down because river temperatures were too high to allow for water discharge (Shugerman 2018). There are examples of adaptation to these challenges, highlighting both policy and design considerations. During the 2011 heat wave in Texas, water typically allocated to farmers in the area was directed to power plants despite regulations detailing the opposite prioritization (Faeth 2013). Partially due to the aggressive installation of wind power in years prior, the increased demand was met through these alternative generation sources but resulted in much higher prices than normal (NOAA 2011; EIA 2011). The Palo Verde plant in Arizona (USA) also has a unique approach to cooling water. This facility does not sit on a body of water but instead uses recycled municipal water (APS 2018).

Drought conditions threaten thermoelectric plants (including coal and nuclear generation facilities) by reducing the availability of cooling water (Galbraith 2011). Several droughts in Sub-Saharan Africa have resulted in documented power losses. The country of Malawi generates 98% of its power from 27
hydroelectric plants and, in 2017, saw capacity reductions of 50% (from 300 MWe to 300 MWe) due to low water levels. As a result, rolling blackouts lasting over 24 hours were required (Alvaro 2018). Similar issues were seen in Tanzania. In 2015 the country was forced to shut down all hydropower due to two years of drought conditions (Alvaro 2018). In several cases, hydroelectric power facilities planned for installation in dams sit in river basins recently affected by severe drought, a hazard event that may increase with climate change ((Alvaro 2018; Conway et al. 2017).

Pre-emptive curtailments were found to occur as a precaution when a hazard event was projected to be imminent at or above safe operating thresholds for a facility. This includes most generation types and a range of hazard events. In cases of drought, a lack of water availability for cooling systems was found to be a cause of curtailment or shutdown (also discussed in the next section on generation-specific vulnerabilities). In cases of extreme heat, the temperature limits set on intake or discharge water from cooling systems may require shutdown of a plant unless special permissions are granted to exceed normal thresholds, often seen at 25°C (Eaton 2012); (Morris 2015).

The impacts of climate change are a particularly important consideration where weather can impact power systems (Mukhi et al. 2017). Particularly, in regions where precipitation patterns are predicted to change and temperatures increase, this may have impacts on facility operation. The consideration of available resources over the life-cycle of a facility during plant design is one factor to increase resiliency.

# 5.2 – Other Considerations: Planning and Policy

In case studies where a catastrophic failure of the power grid was seen (such as The Philippines or Puerto Rico case studies), a few findings emerged in the context of response and recovery. First, pre-emptive planning is critical. This can take many forms, including storage of diesel generators and fuel in critical sites, such as hospitals (Powell, Hanfling, and Gostin 2012), storage of repair vehicles and equipment close to distribution stations or key points in the grid and stockpiling and coordinated planning for postdisaster intermittent energy options (such as rooftop solar panels) (Fthenakis 2013; Ranada 2014a).

In large-scale disasters, existing aid relationships and political agreements can facilitate the quick deployment of temporary infrastructure. When this does not exist, there can be delays in response efforts (NDRRMC 2014; Ranada 2014a);(FEMA 2018b)). Pre-emptive planning can also be important as it typically includes an emphasis on maintenance to address vulnerabilities that may exist because of aging infrastructure or other factors. In Puerto Rico, for instance, some of the challenges relating to transmission infrastructure damage and restoration times was dependent on the jungle growth around the lines, limiting access (Ferris 2018). In the context of ‘building back better’, pre-emptive planning may allow for quicker restoration at lower costs for higher design standards than would be possible if more resilient design is not considered until after a hazard occurs. This was seen in a comparison of Puerto Rico and the US Virgin Islands. Here the same events (Hurricanes Irma, Maria and Harvey) were analyzed in two very close geographic locations that showed different recovery patterns. In April 2018, FEMA and the Virgin Islands Water and Power Authority announced plans to harden the power grid in the U.S. Virgin Islands so that it can withstand hurricanes with winds up to 321 km/hour. This will be accomplished by placing critical transmission lines underground, replacing wooden transmission and distribution poles with stronger, composite poles, and developing micro electric grids (FEMA 2018a). In contrast, no such formal plans have been announced to strengthen Puerto Rico’s power grid.

An important finding that applies across supply chains, generation facilities, and the electricity grid is that redundancy can directly contribute to more stable grid operation even in a non-normal event. Redundancy of transmission lines can allow power to be re-routed if a single line is damaged, and this can reduce curtailment of plants and limit disruptions to consumers. Where multiple generation technologies 28
exist within a power grid, redundancy can reduce recovery time, as can redundancy in supply chains. This was particularly evident in Texas following Hurricane Harvey where nuclear power was able to operate at full capacity throughout the event and wind farms were curtailed during the event but most immediately came back online, covering much of the demand deficit seen from reductions in generation facilities located on the coast which were more affected by storm surge and flooding for longer time periods (Conca 2017).

# **6.0 - CONCLUSIONS**

The impact of natural hazard events on power infrastructure varies based on the asset being analyzed, the standards to which it was constructed, the hazard event, its severity and duration, as well as many other factors. Yet across geographies and hazards, some generalizations are possible. In many instances, design and planning considerations can enhance the resiliency of the asset to withstand and recover from an event. This is true for wildfires, drought, heat waves, flooding, hurricanes, earthquakes and more. As climate change continues to accelerate the pace and severity of weather-related events, quantifying the benefit to proactive adaptation and construction of the power grid requires better understanding. To this aim, this paper has identified several key vulnerabilities and adaptation considerations, including generation facility-specific considerations, supply chain differences in fuel types and the transmission grid.

This paper details three general areas of vulnerability: Supply chains for fuel and maintenance; Generation facility cooling systems and safe operating thresholds; Transmission infrastructure, particularly for above ground transmission lines. System-wide catastrophic failures due to extreme natural hazard events were also seen, especially in developing regions. Each of these findings is detailed in Section 3, including (where available) associated estimated costs and design considerations for more resilient operation of the grid.

# **6.1 – Areas for Future Work**

An important area of future work is to establish the likelihood of future disruptions to power systems from region specific threats. In particular, electrical distribution grids were found to be generally vulnerable to many natural hazards, but wind in particular. Historical wind data is available at high spatial and temporal resolution for much of the world. This can be used to identify regions where electrical grids would be at significant risk and to advise building and maintenance standards to ensure their resiliency. Climatological predictions for future rainfall and temperature also available and can be used to inform where cooling water might become limited. Similarly, historical data on wildfires can be used to identify regions at particular risk for these events. These predictive data can be used to design better systems, and to inform ‘build back better’ efforts.

Additional case studies on geography specific natural hazard events should also be undertaken. Several cities in Sub-Saharan Africa, Southeast Asia and South America cite aging, failing or inadequate energy infrastructure as ongoing considerations. Additional case study work for these locations could help inform the best techno-economic approach to increasing resilience. Appendix F contains information on some developing regions of the world that are of interest for future work. This includes a list of severe natural hazard events (Table F-1) and a list of geographic regions with regions of interest for case study work based on hazard exposure and an infrastructure gap (Table F-2). As an example, Lagos, Nigeria has over 20 million persons, lacks critical power, and other, infrastructure and is prone to natural hazard events including flooding and sea level rise (Gandhi 2018; Soleye 2015; Business Journal 2017; 100 Resilient Cities 2018b; Busari and Osman 2017). Kigali, Rwanda cites similar issues regarding infrastructure, energy shortages, and exposure to flood, droughts, and severe storms (Byumvuhore 2018; May and Kamurase 2009; 100 Resilient Cities 2018a; Al Jazeera 2018; Davis 2017).

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The interdependencies of infrastructure systems are complex, poorly understood, and affect the ability to recover from a hazard events. Future work in this area should consider a larger range of events and geographies, specifically as they relate to design considerations, although data availability is a limitation. A particular topic of interest is the interdependence of power systems with other critical infrastructure such as roads, pipelines, emergency services and communication infrastructure. How to avoid cascade failures when one system is damaged is an important for future work. Finally, the value of different types of generation and distribution networks (large, centralized vs. smaller, distributed systems) should be considered in the context of other stresses on a system, including conflict and man-made disasters. Understanding the benefit to smaller distributed systems that require less transmission distances and have a smaller, localized geographic impact if compromised is an important area of study in geographies with ongoing conflict.

Additional work on geographically specific hazard probabilities, coupled with the associated generation and distribution system vulnerabilities, can be used to inform location specific design and rebuilding standards. This information could help to better allocate development and redevelopment funds. Consideration of exposure to a hazard (particularly in terms of siting facilities near coasts, waterways or within floodplains) can impact the amount of damages seen. Specific engineering design standards listed in Table 4 and Appendices B, C and D can be used as a reference point in this work.

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