Hurricanes, Microgrids and Reslience

In the Caribbean, according to Rocky Mountain Institute Engineer, Kaitlyn Bunker, hurricanes that cause disaster are such regular occurrences that local planners take them into account. Most of the damage is done to distribution and transmission lines. This is what occurred on the Island of Dominica after Hurricane Maria hit the island in 2017. She showed this slide as an example of the destructive power of Category 3 and Category 4 storms.

The damage was so over whelming that lights in the entire region went dark.

In the British Virgin Islands the 11 islands are linked by through undersea power cables to a central generating plant. It was found that just being dependent on one central Power Plant left the people on the islands too vulnerable. Instead they opted to build microgrids on many of the islands. Over half of Carribbean Islands now have solar PV and many have batteries for spinning reserves.

Despite estimated wind gusts of 180 -190 miles an hour in 2017, many solar PV systems in the British Virgin Islands, Turks and Caicos Islands, Puerto Rico and St. Eustatius survived.  

“In contrast other PV systems suffered major damage or complete failure with airborne solar modules,broken equipment and twisted metal racking.” Solar Under Storm page 9.

Those In Puerto Rico, the US Virgin Islands and Barbuda suffered critical damage

Because of variability in wind speed and geography it is not possible to determine all the reasons for failure.

However specialists from the Rocky Mountain Institute commissioned a study which said the failed sites shared these common characteristics during Hurricanes Irma and Maria

1) Top down or T clamp modules

2) Undersized Racks

3) Lack of lateral side racking supports

4) Undersized bolts

5) Under torqued biolts

6) Lack of vibration resistant connewctions

7) PV module design too low for environment

8) Use of self tapping screws instead of bolting

Surviving attributes for solar fields include

1) Dual post piers

2) Through bolting of solar modules

3) Lateral racking supports

4) Structural calculations on record

5) Owners engineer of record recorded

6) Vibration resistant module bolted connections

(Solar under Storm Part One Summary)

Organization and methodology has led to the resilience of microgrids during Category 3, and 4 hurricanes. The Rocky Mountain Institute has helped the different island power companies coordinate the needs of their people. Despite the fact that they represent different countries, political systems and languages, theses island nations have developed decentralized power systems that help them survive destructive hurricanes.