Julia Lynch Williams, speaking ahead of the annual Scottish Renewables awards in Edinburgh tonight, said companies must focus on proven technologies to help meet renewable energy targets for 2020.
She expects the industry to begin moving more resource towards building large-scale offshore wind farms as part of that.
RWE npower renewables, the UK renewables arm of German parent RWE, operates almost 300 megawatts of onshore wind in Scotland plus some hydro schemes. It is also building a £200 million biomass plant at the Tullis Russell paper factory in Markinch in Fife.
However, last year RWE npower renewables pulled out of a wave energy project being developed by Inverness firm Wavegen at Siadar Bay off the north coast of the Isle of Lewis.
Ms Lynch Williams said: "I believe at some point in my lifetime [marine] will make a significant contribution but not in the next five to seven years. We need to get beyond [research and development] and into proof of concept. Even at proof of concept level you are seeing large subsidies.
"From our perspective, we fundamentally believe to deliver 2020 targets and probably up to 2030 we have to rely on technology which is proven."
Ms Lynch Williams praised the Scottish Government's supportive stance on renewable energy.
She said: "At an industry level the consistently and publicly supportive Government position in Scotland appears to be factually supported by the level of projects coming through the system.
"A number quoted at a conference not all that long ago suggests something like 80% of planning applications for onshore wind are successful in Scotland and the number is significantly less across England and Wales.
"I would not underestimate how important the support from Government is. That sets the framework for us for the continued investment in development.
"As long as the Scottish Government continues to provide consistent and public support that is a big tick."
Ms Lynch Williams warned there was an increasing trend for local authorities across the UK to push wind farm planning applications to public enquiries which ended up being costlier for developers and the public sector.
She said: "We are aware it can be quite a difficult thing for people to accept, particularly in onshore wind. We fully accept we have to go through due process.
"We are seeing more projects going to public enquiry now than we did five to 10 years ago. It costs us about £500,000 extra to go to public enquiry and local councils about the same amount."
Although Ms Lynch Williams believes there is still work to be done on improving grid connection across Scotland, she has been impressed by the talent pool here. She said: "We have no issues on a practical level in terms of people with the right level of skills.
"It has never been an issue in terms of construction of a project, taking on apprentices or the operation of a wind farm or hydro plant."