Gülsan's first renewable energy project, Degirmenustu HPP was built in the Mediterranean Region, near the city of Maras, Andirin, in order to utilize the energy potential of the Korsulu River.

Degirmenustu HPP Project consists of the Kargacayiri Regulator, a settling basin, a transmission channel, a transmission tunnel, a forebay pool, a penstock, a powerhouse, a tailwater channel and an electrical substation.

The water collected with Kargacayiri Regulator on the Korsulu Stream at a base elevation of 1235.00 meters is transferred through a 145 meter long passageway and 2871 meter long and 3.2 meter wide horseshoe transmission tunnel (T1) to a forebay pool. After the forebay pool, the water is passed through a pressurized circular transmission tunnel of 3.2 meter width (T2). Then, the water is directed to the 611 meter long, 2.4 meter wide penstock with a 15 m³/s flow, and finally to the vertical axis pelton-type turbines at the 940.00 meter tailwater elevation level power house.

The produced energy will be transmitted via the 8 km long power transmission lines of 33 kV capacity to the interconnected power system.

Degirmenustu HPP started commercial power production in 05 December 2008 with an installed capacity of 40 MW and an annual average production of 114 GWh.

In terms of carbon emissions, Degirmenustu HPP, reduces approximately 74.000 tons of CO2 per year.

For the positive environmental impact it has created, Degirmenustu HPP has also been awarded Verified Emission Reduction (VER) credits by international independent verification bodies.