Aruba's grid is built around reciprocating engines, and the island's utility is now putting a controller over all of it. Wärtsilä announced on 13 October an agreement with Water- en Energiebedrijf Aruba (WEB Aruba) to integrate, optimise and control the island's generating assets. The package has three parts: an EPC contract for a 35 MW / 70 MWh battery energy storage system, a Wärtsilä energy management system, and a services agreement covering that system and the maintenance of the storage plant. Wärtsilä booked the order in the third quarter; final takeover is planned for the second quarter of 2028. No contract value was given.
Software Sold as a Service
The energy management system is the less visible half of the deal and probably the more interesting one. It brings forecasting together with secondary and tertiary control, so it does more than log data: it decides how the plants on the island are dispatched. WEB buys it on an as-a-service basis, which under the agreement means regular updates to its configurations and models and quick technical support. Wärtsilä calls the battery its largest energy storage project in the Caribbean so far, in both MW and MWh.
WEB's chief executive Alfredo Koolman said the utility is giving priority to cleaner production and expects the system to make fuller use of renewable power. Risto Paldanius, Vice President, Americas at Wärtsilä Energy, spoke of better quality and reliability of supply at a lower cost.
Firm Capacity First
The order follows an engine extension that was finished only weeks ago. In June 2025 Wärtsilä described an EPC job adding two 50DF dual-fuel engines, 36 MW in total, to an existing WEB plant. The capacity Wärtsilä has supplied on the island would go from 194 MW to 230 MW, or 85 % of Aruba's 268 MW. According to Noticia CLA, WEB handed over the expanded RECIP-3 plant at a ceremony on 19 August 2026, an investment of about Afl. 115 million. It lets the utility retire a mobile power plant that had been in service since August 2024 as an emergency measure. Koolman said then that the extra firm capacity gives a stronger base for adding wind, solar and storage.
So the sequence on Aruba was firm engine capacity first, then storage and a control layer above it. That order matters.
What Changes for the Engines
Once a battery and a fleet controller are in place, the engines stop being the only thing that holds the frequency. They are started and stopped by software that weighs forecasts, battery charge and fuel cost, and their running pattern follows the wind and the sun more than the load curve. That is good for the fuel bill. For the people who maintain the plant it means more starts, more hours at part load and duty cycles that are harder to predict when service intervals are planned.
The same arrangement is turning up in mines, industrial sites and data center yards where gensets share the work with batteries. When it is specified, the control interface between the energy management system and each engine's own controller deserves as much attention as the battery rating, and it needs to be tested at commissioning together with the engines, not on paper.
Sources: Wärtsilä, Wärtsilä, June 2025, Noticia CLA