Plans to build 32 wind turbines in forestry in the Denbighshire and Conwy border are now being examined by the UK government's Planning Inspectorate.
Officials are now inviting opponents and other interest groups to register to share their views on the plans for the Clocaenog Forest.
Proposals were first put forward in 2009 but must go through several stages in the planning process.
Officials will prepare a report for ministers to consider.
Members of the protest group Clocaenog Against Wind Turbines (CAWT) are opposed to more turbines in the wider area, saying they want the forest preserved.
The Planning Inspectorate now has six months to conduct its examination and people have until 12 June to formally register to be able to air their views.
It is an agency of the Department for Communities and Local Government responsible for public examination of development plans.
RWE npower renewables says the forest turbines could produce enough energy to supply the domestic needs of up to 40,800 households.
It has set up a dedicated website to provide updates and an explanation of the process affecting Clocaenog Forest.
The company said it has worked closely with ornithologists and ecologists to produce a habitat management plan, to include restoration of habitats and woodland management.