The damage caused to the power grid is a major problem Puerto Rico faces when recovering from hurricanes. By 8:00 PM on September 20th, 2017, PREPA reported that nearly 100% of its customers on the island had lost power.  It was not until eleven months after Maria that PREPA restored power to nearly all of its customers. In order to reduce the damage caused by future hurricanes and the time required to make repairs, certain steps could be taken to make the current power grid more resilient.
Weaknesses in the Power Grid
a.) Wooden Poles: Many of the failures of power distribution following the storm can be attributed to the failure of wooden poles. Several wooden poles on the island had attachments added for communication systems. It is unclear how thoroughly communications providers were required to test the structural integrity of the poles following the installation of such attachments. For this reason, the Department of Energy suspects that these attachments are partly responsible for the poles being unable to withstand the storm.  Along with implementing more routine and standard assessments of poles, there is value in considering more resilient materials from which they can be made. Utility poles can be made out of steel, concrete, or composite materials instead of wood. Additionally, transmission towers can be made with galvanized steel or concrete instead of aluminum. Other structural supports, such as guy wire anchors, can also be installed. Many power lines were also damaged not by the strong winds themselves, but due to flying tree limbs and other debris. Proper vegetation management (i.e., removing any tree branches that are on the verge of breaking or falling onto power lines) can help reduce the occurrence of this issue.
b.) Transmission Towers: Another major cause of the blackout on the island was the failure of transmission towers, which carry electricity at high voltages across long distances, when faced with the high wind speeds of Maria. In order to make transmission towers more resilient during a hurricane, the use of monopoles (shown in Figure 2 on the left) has been suggested. During the hurricane, steel monopole transmission towers fared much better than lattice tower structures (shown in Figure 2 on the right). 
Current Building Codes
Prior to Hurricane Maria, Puerto Rico adopted the 2009 International Building Code (IBC) in 2011, requiring buildings to withstand 140 mph winds, which is typical of a Category 3 storm. Since then, Puerto Rico has adopted the 2018 IBC after assessing the damage from Hurricane Maria, which was a Category 4 hurricane. The 2018 IBC makes recommendations for minimum wind speeds for different types of structures, such as offices, commercial buildings, residences, utility posts, and schools. For Puerto Rico, wind resistance recommendations in the new code are between 150 and 200 miles per hour. Although there are strict standards for building codes, it is important to note that continuous enforcement will be required to ensure the building of the energy grid and structures are up to code.
Proposed Future Structural Improvements
a.) Underground Power lines: In order to prevent damage to power lines, many people have also proposed that Puerto Rico move its power lines underground. Unfortunately, this solution may not be a viable one, since it brings up several complications. Much of the island faces flooding during storms, so many underground power lines would be at risk of being damaged from water intrusion. It was found during Hurricanes Katrina and Sandy that underground power lines in coastal areas are at risk for saltwater intrusion, which damages their components.  A similar problem would likely arise in Puerto Rico if areas with high risk of flooding had lines moved underground. Additionally, this option is not very cost effective, either. It can cost up to 10 times more to move lines underground than to rebuild lines above ground.  For these reasons, a more realistic and effective solution would be to strengthen lines above ground.
b.) Resilient Solar Array Infrastructure: Currently, in order to shift to a more resilient, renewable source of energy throughout the island, a law was passed in Puerto Rico which envisions half of its energy coming from solar power by 2035 and all of its energy coming from solar power by 2050. If such plans are going to be implemented, it is necessary to consider ways to make solar panels more durable. At the moment, the areas of the island with the largest solar energy potential are along the coast. Since areas along the coast are the most susceptible to damage from flooding and strong winds, solar panels installed in these areas must be built with these factors taken into account. For instance, one solar field built by a company called TSK Solar was able to survive Hurricane Maria. These solar panels were built to withstand winds of over 150 mph and set up several meters off the ground to account for flooding.  If other solar farms are built similarly, the island can effectively use areas with good solar potential without worrying about future storms.