The carriers are equipped to allow onboard regasification of LNG for direct delivery into natural gas pipeline systems.
The move will boost Houston, Texas-based Excelerate's fleet of carriers to nine, a statement said.
The company has three LNGRV vessels and one conventional LNG bulk carrier in service, and wo newbuild vessels due for delivery in 2008 and 2009.
Excelerate's new vessels include two ordered by Exmar in 2006 as well as a third order just agreed. Exmar is based in Antwerp, Belgium.
The new ships when they come into service will be named Exquisite, Exemplar and Expedient and will be delivered between the third quarter of 2009 and the first quarter of 2010.Exmar will operate the vessels on behalf of Excelerate. The new vessels will be built in South Korea by Daewoo Shipbuilding & Marine Engineering Co. Ltd.