The Netherlands-based maritime solar energy specialist deploys its Solar Flatrack solution onto unused deck space without disrupting operations.
The company is now preparing to expand use of its Solar Flatrack technology into the international bulk shipping market after completing two trials and installing the first full-scale system aboard the Vertom Tula, where a 79kWp installation was divided into four independent solar groups connected directly to the vessel’s 400V AC hotel load switchboard.
“In its current form, Solar Flatrack is well suited for bulk cargo vessels equipped with stackable or folding hatch covers,” said Bo Salet, CEO and co-founder of Wattlab. “This typically includes vessel sizes up to Capesize, where deck layouts and cargo operations allow for relatively straightforward integration of modular systems like ours.”
Wattlab said the technology is now suitable for ships up to the Supramax class, with development work under way for Panamax carriers.
The system has been designed to supplement onboard electrical demand, particularly for hotel load. Performance data gathered during the pilots indicated that the solar arrays functioned consistently in marine conditions and reduced auxiliary fuel use, contributing to lower emissions.
The initial trials, conducted with TNO and shipping company Vertom, were carried out on the Vertom Anette. Lessons from the project informed the design and installation of 44 Solar Flatracks on the Vertom Tula, where the equipment reduced approximately one-fifth of the vessel’s hotel load.
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A key consideration during development was avoiding operational disruption. The Flatrack units are engineered so they can stay in place during cargo handling and be disconnected, stacked or stored within the footprint of a 20‑foot container when required. According to Wattlab, this enables shipowners to retain flexibility in deck operations.
“The main limitation arises not from the core technology itself, but from how cargo is handled on larger vessels,” said Salet. “On Capesize vessels and above, operations often involve falling cargo onto deck areas, which introduces a significantly harsher mechanical environment. This requires additional protection and a different system design to ensure durability and reliability under those conditions.”
Salet continued: “We have recently started development work to address this specific challenge, focusing on solutions that can withstand these operational loads without compromising performance or safety.”
Salet added that over 200 international parties are interested in applying Solar Flatracks across their fleets.”
Wattlab said the technology can help operators improve performance under emissions-related indicators such as CII (Carbon Intensity Indicator) and EEXI (Energy Efficiency Existing Ship Index) by reducing fuel consumption. It also supports compliance with EU regulations including FuelEU Maritime and the Emissions Trading System. The company estimates a payback period of three to five years.
“We see Solar Flatrack primarily as a practical and complementary decarbonisation solution rather than a one-to-one replacement for other pathways,” said Salet. “Its main strength is that it delivers direct fuel and emissions savings with a relatively simple retrofit, while avoiding the infrastructure dependency of some alternatives.”
How does Solar Flatrack compare with competing decarbonisation pathways?
Bo Salet: Compared with shore power, Solar Flatrack has the advantage that it generates value while the vessel is operating, rather than only when it is connected in port. Shore power is very effective where infrastructure is available, but that availability is still limited in many ports, and it does not reduce onboard energy demand during voyages. Solar Flatrack helps reduce generator use both at sea and, depending on the operating profile, also in port. Compared with wind-assisted propulsion, our solution is generally simpler to retrofit and easier to integrate operationally. Wind systems can deliver significant savings on the right routes and vessel types, but they are more route-dependent and can have a larger impact on vessel design, air draft, cargo handling, or port operations. Solar Flatrack is modular, low-profile, and can be installed with limited disruption, which lowers the threshold for adoption.
Compared with alternative fuels, the main difference is that Solar Flatrack improves the efficiency of the vessel itself rather than replacing the energy carrier. Alternative fuels can potentially achieve deeper decarbonisation, but they often require major changes in fuel supply, onboard systems, regulation, and cost structure. Solar Flatrack is easier to retrofit in the near term and can start reducing fuel consumption and emissions immediately, without requiring new bunkering infrastructure. So in terms of positioning: alternative fuels may be necessary for full long-term decarbonisation, but solutions like Solar Flatrack can already reduce emissions today, improve energy efficiency, and lower compliance costs. That makes it an attractive near-term step, and in many cases a complementary technology alongside batteries, shore power, wind, or future clean fuels.
