Surface Effect Ships (SES), which marry the advantages of hovercraft and catamaran technologies, have been around for more than 50 years. As windfarms move further offshore, the ability of SES to operate as a stable, fuel efficient platform in harsher waters is gaining new attention in the market
Offshore Support Journal asked Trygve Halvorsen Espeland, naval architect at Norwegian naval architectural and marine engineering firm ESNA, the inventors of the Sea Puffin SES daughter craft, to explain the advantages of SES technology for crew transfer.
What are the advantages of an SES design for offshore wind CTVs and daughter craft?
“A Surface Effect Ship (SES) has two side hulls like a catamaran. Between these two hulls, fore and aft, there is flexible rubber sealing. Fans blow air into this air cushion between hulls and rubber seals, and partly lift the vessel out of the water. Up to 80% of the vessel weight is typically lifted by this air cushion. For a CTV and daughter craft this has some great advantages.
“Firstly, an SES is more fuel efficient. The air cushion reduces resistance, which allows both higher speed and reduced fuel consumption as compared to traditional CTVs and daughter craft.
“Secondly, the contact with waves is reduced. In combination with the ESNA air cushion motion control system this greatly improves the transit comfort for passengers. When pushing on to turbines the control system counteracts the effects of waves, allowing the SES to access the wind turbines in higher wave heights.
“The combination of these two properties makes the SES very well suited for offshore wind operations. Sea Puffin 1 is the perfect match for this. The vessel is the weight and size of a daughter craft but has the turbine access of a larger CTV.”
Has Sea Puffin 1 performed as you expected regarding stability and safety? What about emissions?
“Yes, Sea Puffin 1 has delivered on all performance and safety expectations. The vessel has demonstrated successful safe turbine access in 1.5 m significant wave height for a range of test conditions, and even been successful in tests up to 1.75 m.
“At maximum speed, which is typically 20 to 25 knots depending on wave conditions, the vessel only burns 150 l/hrs fuel oil. Compared to larger CTVs Sea Puffin 1 can typically cut the operating fuel consumption in half. And combined with an offshore operation from a mother ship, the vessel can reduce fuel oil consumption and emissions even more by not having to transit to shore.”
Where is Sea Puffin 1 deployed now?
“The vessel is in the UK. Owner WindPartner had the vessel scheduled for mothership demonstration, but this was postponed due to this very unfortunate Covid-19 situation. We do hope and trust that the UK, and remaining Europe, will soon fight off and recover from this crisis."
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