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