Llandinam wind farm opened in 1992
Plans have been unveiled in Powys to turn one of the largest wind farms in the UK into one of the tallest.
The companies behind the scheme want to replace 103, 45-metre (149ft) tall turbines in Llandinam, near Newtown, with 42, 122-metre (400ft) machines.
They said the redevelopment would treble the output of "clean, green energy" at the mid Wales site.
But objectors claim the new turbines could have a detrimental visual impact on the landscape.
Wind energy consultant Geoffrey Sinclair said, if approved, the wind farm would have the tallest turbines in Wales.
When it was opened in 1992 Llandinam was one of the largest wind farms in Europe.
But Mr Sinclair, who specialises in the environmental impact of wind energy, warned the changes would affect the environment.
He explained that only two other sites in the UK, both in Scotland, had similar sized machines.
In Llandinam, the plan by ScottishPower Renewables and partner Eurus Energy is to treble the output of "clean, green energy" at the site.
Project director David Walker said: "This is an important milestone in the development of renewable energy in the UK.
"The redevelopment of Llandinam will see the replanting of one of this country's first wind farms, which at the time was the largest in Europe."
The developers said the "newly repowered wind farm" would be capable of producing enough energy to power more than 53,000 households.
Mr Sinclair, who used to advise the Campaign for the Protection of Rural Wales (CPRW), said blades on the proposed new turbines would be taller than the existing machines.
He added: "Cefn Croes (near Aberystwyth) has the tallest turbines in Wales at the moment.
"The planned turbines will become the tallest in Wales and some of the tallest in the UK. They are only two other sites in the UK, in Scotland, with similar sized turbines.
"Considering both the size and number, these enormous turbines will have a huge visual impact."
The companies behind the project will be hosting a number of public information days in Llandinam and the surrounding areas during May.
Currently, there are 26 wind farms in Wales with 482 on-shore turbines and 30 off-shore.