Enabling reliable transmission of offshore wind power

More power. Green transition. Clean energy. Climate change puts global pressure on everyone to find solutions for clean energy development. China now makes use of its immense offshore resources to build a wind power farm with an aggregate capacity of 1,1 GW. For the transition to shore, Alfa Laval T series are used in the wind power converter station to ensure reliable performance and high thermal efficiency.

Transmitting green electricity from sea to land

The conversion station at Three Gorges Rudong Offshore Wind Farm is the largest in the world, developed by Three Gorges Corporation (CTG). To deliver the generated electricity to shore with minimal loss, it is converted to direct current under high voltage. The voltage is first increased in the AC booster station and then at the HVDC (High Volage Direct Current) converter station. AC is converted into DC which is then transmitted to shore where it is converted back to AC and injected into the electricity grid. For offshore wind power transmission, converter stations are set on the surface of the open sea. This means stringent requirements for the equipment.

Reliable performance for critical positions

For the critical cooling positions in the HVDC converter station, Alfa Laval gasketed plate heat exchangers were chosen for their reliable performance and high thermal efficiency under harsh offshore environments. Alfa Laval T series is equipped with unique and vital features; FlexFlowTM where the asymmetric channels optimize thermal efficiency resulting in up to 30% higher efficiency and reduced fouling, CurveFlowTM whereby the distribution area improves media flow and minimizes risk of fouling, and OmegaPortTM with non-circular port holes which enhance the media flow and thermal efficiency.

FlexFlow™
Superior thermal performance

CurveFlow™
Distribution area

Omegaport™
Non-circular port holes

Harsh conditions challenge the heat exchangers

During the AC to DC conversion at the HVDC converter station, its core components generate heat requiring an external cooling system. Temperature control of the cooling water and cooling of the thyristor valves is of utmost importance to ensure continuous transmission of electric energy while minimizing power loss and unplanned downtime due to overheating.

In such environment, seawater is usually preferred as a cold source. However, seawater has a very high corrosion intensity. It also contains sediment and a rich marine life as well as strong winds and humid conditions. Adding the limited space of the offshore platform, this combined creates a very harsh and challenging environment for heat exchange.

Inside the convertor station

Outstanding cooling solution optimise performance

The heat exchangers used, Alfa Laval T series, have corrosion-resistant titanium plates due to the use of seawater as the cooling medium. The units were carefully designed to assure that the offshore flexible HVDC transmission converter station's external cooling system can fully use the seawater's natural cooling source and use the low-temperature fresh water to cool the converter valve and transformer after equipping a freshwater circulation system.

In a harsh and challenging environment, Alfa Laval gasketed plate heat exchangers deliver outstanding performance in a compact footprint.