London said companies MeyGen Ltd. and Sea Generation Wales Ltd. won the funding from the Marine Energy Array Demonstrator plan launched last year.
The British government said marine energy could meet as much as 20 percent of nationwide energy demand by 2050.
"These projects will provide valuable insight into how best to harness the power of the sea and take us one vital step closer to realizing the full potential of marine in our future energy mix," British Energy and Climate Change Minister Greg Barker said.
MeyGen touted its project as the largest tidal energy development of its kind to get government support. Six tidal energy turbines would be installed as part of a demonstration array by 2014.
Sea Generation said its nine devices would be able to generate 10 MW of energy through nine tidal turbines. Its array would be fully operational by 2015.
"This $30 million will give MeyGen and Sea Generation Wales the boost they need to leap to the next level and test their innovative turbines in formations out at sea," Barker said.