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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