Variable Speed Driven (VSD) oil-free rotary screw blowers from Atlas Copco have been chosen to play an integral role in an innovative air lubrication system designed to save up to 8% on fuel on larger vessels.
Applicable for both retrofit and new-build installations, the patented system from London-based Silverstream Technologies reduces frictional resistance between the water and the hull surface, dramatically reducing fuel consumption and associated emissions. The Silverstream system employs a series of carefully positioned air release units (ARU) on the ship’s hull near the bow, which then creates a carpet of micro-bubbles. This carpet reduces drag, minimising the amount of fuel required to propel the vessel forward.
Designated as an ‘innovative technology’ within the International Maritime Organisation’s Energy Efficiency Design Index (EEDI), the Silverstream system is seen by many as integral to the future of shipping by reducing Green House Gas emissions.
At the heart of the system is the need for reliable air compressor technology. “The system relies on a constant and dependable supply of compressed air,” explained Stephen Potts, Head of Supply Chain at Silverstream. He added: “The Atlas Copco ZS55 oil-free screw blowers provide this – giving us the right combination of cost, performance and reliability.”
The energy-efficient VSD technology within the blowers is central to their role in the Silverstream system. As Rob Boughton, business development manager for low-pressure technology at Atlas Copco, explains: “Why give full flow when sailing at a low speed? That would be a waste of energy. That’s why ZS units are equipped with VSD technology: you can perfectly follow an ‘optimal flow demand curve’ and tune your flow to your sailing speed. You also benefit from a large turndown to further optimise energy efficiency.”
As a fuel-saving measure, air lubrication is more effective when the compressors or blowers used are themselves highly efficient, and Atlas Copco enables a faster return on investment by giving Silverstream Technologies and its customers the right balance of CAPEX and OPEX.
Also, since the air lubrication system releases air directly into the ocean around the vessel, it was important from an environmental perspective to ensure that the air output carried no pollutants. Stephen Potts explained: “The ZS oil-free system was perfect for Silverstream since it gave us reliability and pollutant-free output, thus supporting the company’s strong environmental position.”
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