The developer has also said its contractor GeoSea will use High Wind's new Boom Lock system. It allows for safe component installation in higher wind speeds.
Mainstream said the use of the two initiatives will help the project "produce the cheapest ever electricity generated from a UK offshore wind farm".
Siemens' offshore transmission module (OTM) removes the need for a topside platform and can be installed across two turbine foundations. Mainstream said it would save 30% in capex costs.
The OTM was unveiled by Siemens at the EWEA Offshore 2015 conference in Copenhagen last month.
The modules can be mounted on special "balconies" fitted to turbine foundation transition pieces. A 500MW project would need two turbines fitted with the equipment on their foundation structures after the necessary structural load adjustments have been made. Alternatively the OTM could be fitted on a separate turbine foundation (without a turbine).
Mainstream also said GeoSea will use a "Boom Lock" system developed by High Wind BV. It allows installation of offshore wind components in winds up to 15 m/s, reducing the work days lost to unsuitable weather.
The Boom Lock was also unveiled in March following performance trials on GeoSea's Neptune vessel. The system is mounted on an offshore crane and controls the movement of the load and the crane hook.
Mainstream's chief operating officer Andy Kinsella said the project would be the first commercial development without a "heavy offshore substation topside and foundation". He also described the Boom Lock as a "game-changer".
Neart Na Gaoithe was one of only two UK projects to be awarded a contracts for difference subsidy by the government in February. Mainstream was able to secure the contract by bidding to produce energy at £114.39/MWh. It is due online by 2020.