- Lowest Cost of Energy microgrid
- 70% offset of diesel consumption by solar energy
- Environmental benefits and financial performance
- Low-risk project delivery with high client satisfaction
For many decades, every time a light was turned there had to be a diesel generator running to power it. The diesel powerplant was running around the clock, 365 days a year, just like every other islanded community in the Caribbean. Since the PV microgrid was started up early in 2021, the sun has been powering all of the lights and other island loads for about 65% to 90% of the day. Diesel consumption has dropped overall by about 75%, and now visitors hear chirping bananaquits and parrots when exploring the island rather than diesel engines. The solar microgrid is safe, quiet, and reliable, and the project is a low-risk, smart investment. Most of the time there is no diesel smoke wafting downwind of the island and there’s a much lower chance of diesel fuel spills on land or in the pristine waters. Maintenance costs also are reduced, and overall there is much more cash available for other island improvements.
Highbourne Cay Resort
Engineer and Constructor (EPC) for 1.1 MW Ground-Mount PV System with 2MWh battery plant integrated with an existing island diesel powerplant.
Design Rationale and System Architecture
Highbourne Cay is in the chain of the Exumas, adjacent to the Bahamas National Trust, Land and Sea National Park system. It is remote from any airport or port of entry, so shipping and personnel logistics were a challenge. From the engineering perspective, as with any Caribbean project, wind and corrosion resistance were key factors driving equipment selection, quality assurance, and quality control during construction. This project is engineered and constructed to a 180 mph wind standard–significantly higher than the Category-5 threshold wind speed. The design follows the recommendations from the Solar Under Storm manual that was adopted by CARILEC as a best-practices guide, and of which the Principal Engineer on this project was one of the primary contributing authors.
- Selection of the strongest PV modules with highest uplift pressure rating.
- Racking with heavy galvanizing and employing a 4-post design with cross bracing for resistance of non-linear, irregular wind gusts.
- Field equipment not attached to the racking tables to avoid the added stresses that are not part of the racking design.
- PV modules that are through-bolted instead of top-clamped, to resist the cascading failures common with top-clamped modules in hurricanes.
- PV module hardware using locking, sawtooth washers to resist vibrational loosening.
- Strict wire-management practices for long-term survivability and performance.
- Stainless steel electrical equipment to resist corrosion.
- Thorough documentation, wayfinding, and island staff training for better response to abnormal situations.
We delivered the project in phases, to limit risk, control investment, and improve decision making. The first phase was an energy model, followed by engineering, followed by the construction phase. We have used this approach many times and we find that these intangible aspects make as much difference as quality workmanship in delivering outstanding performance. Construction required close coordination with the management team to minimize interruption of island operations and visitor comfort. All hot work and cutovers had to be coordinated with staff and marina guests to avoid damage to sensitive electronics on shore and aboard ship. Sometimes the diesel powerplant doesn’t run at all during a sunny day. The island owners can see this any time on their mobile-device monitoring apps. But when it is cloudy and the marina is full of large yachts, the diesel powerplant can run most of the time on those days. The energy modeling phase explored the operating and occupancy expectations and helped develop the best combination of PV power capacity, battery plant capacity, and diesel operation to deliver the lowest overall cost of energy over the life of the project. Now that we have good operational data and experience with the characteristic loads of the island resort, the next steps include expanding the microgrid and reducing more of the diesel consumption and also addressing energy efficiency measures to further improve performance and reduce operating expenses.
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