St. Eustatius an island in the Caribbean Sea depended on diesel fuel for public electricity supply. Every day 12,000 liters of diesel were needed to supply 4,000 inhabitants. Until 2016! Then SMA Sunbelt commissioned a PV diesel hybrid system covering 23% of the energy demand. The first phase went very well, so we were happy to continue simply with the expansion of the second phase in the same manner as phase one was executed.
That’s why they decided to double diesel savings. To meet this target, SMA engineers worked out an ambitious plan: double the solar power and use as much solar energy as possible during the day, while switching off the diesel generators! In a very short time, SMA engineers developed the Sunny Central Storage 2200 with grid forming functions.
Grid Forming Control Algorithm
We developed a grid forming control algorithm which controls voltage and frequency based on the load and PV balance on the grid. So the Sunny Central Storage can run completely standalone or in parallel to an existing genset grid and other generation. Simulations delivered the optimal storage capacity of additional 5.3-megawatt hours for energy shifting from midday into the evening hours. SMA Sunbelt Energy, a specialist for off-grid solutions, was responsible for the overall system design, sizing and supply of lithium-ion cells and its customized container design.
Turnkey from the first single line diagram to the provision of fitting cable lugs. We are interfacing eight gensets with remote start/stop functionality, we have grid forming inverters, an overlay plant controller that controls the whole environment with frequency and voltage control, and has an internal energy management system that decides when the dynamic genset shutdown should be run or not.
So that we can completely shut down the diesel gensets and save as much energy as possible. To test these systems, we have a very flexible and unique setup to combine all these different sources. This system then can be operated either in grid parallel mode or even as an isolated grid. After testing all these functionalities and with all the hardware dependencies we have the good confidence to bring our solution to the customer site.
An additional unscheduled real-life test was faced in September: two category 5 hurricanes hit the island: Irma and Maria! We know that the storm was pushing winds of 200 miles per hour in excess of this, and when I cleared my eyes and I turned and I looked over at the park, I saw the most beautiful thing: it was completely intact! The most exciting part of this project was turning off the diesel.
Battery And Solar Power
The most exciting moment for me on this project was when the whole genset plant was shut down for the first time and this really noisy surrounding turned into a really quiet environment. The whole island was powered only from battery and solar power. St. Eustatius is 100% solar now with European grid quality! On every sunny day the island saves around 5,500 liters of diesel, 1.7 million liters per year.
The system delivers uninterrupted power supply in case of a generator failure at night and prevents blackouts. We achieve something 100% for a grid. That I’m sure has never been presented before in the industry. Here it happens first on St. Eustatius with SMA as a key partner in this endeavor. We did it very successfully. St. Eustatius is the first and there are many islands to come.